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Acs0504 Intestinal Obstruction 2004
1. © 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 Gastrointestinal Tract and Abdomen 4 Intestinal Obstruction — 1 4 INTESTINAL OBSTRUCTION W Scott Helton, M.D., F.A.C.S., and Piero M. Fisichella, M.D. . Assessment of Intestinal Obstruction Clinical Evaluation Intestinal obstruction is a common medical problem and accounts for a large percentage of surgical admissions for acute HISTORY AND CLINICAL abdominal pain [see 5:1 Acute Abdominal Pain].1 It develops SETTING when air and secretions are prevented from passing aborally as a result of either intrinsic or extrinsic compression (i.e., mechani- When a patient complains cal obstruction) or gastrointestinal paralysis (i.e., nonmechanical of acute obstipation, abdom- obstruction in the form of ileus or pseudo-obstruction). Small inal pain and distention, intestinal ileus is the most common form of intestinal obstruc- nausea, and vomiting, the tion; it occurs after most abdominal operations and is a common probability that either mechanical bowel obstruction or ileus is response to acute extra-abdominal medical conditions and intra- present is very high.3 Mechanical obstruction can often be distin- abdominal inﬂammatory conditions [see Table 1].2 Mechanical guished from ileus or pseudo-obstruction on the basis of the loca- small bowel obstruction is somewhat less common; such tion, character, and severity of abdominal pain. Pain from obstruction is secondary to intra-abdominal adhesions, hernias, mechanical obstruction is usually located in the middle of the or cancer in about 90% of cases [see Table 2]. Mechanical colonic abdomen, whereas pain from ileus and pseudo-obstruction is dif- obstruction accounts for only 10% to 15% of all cases of fuse. Pain from ileus is usually mild, and pain from obstruction is mechanical obstruction and most often develops in response to typically more severe. In general, pain increases in severity and obstructing carcinoma, diverticulitis, or volvulus [see Table 3]. depth over time as obstruction progresses; however, in mechani- Acute colonic pseudo-obstruction occurs most frequently in the cal obstruction, pain severity may decrease over time as a result postoperative period or in response to another acute medical of bowel fatigue and atony.The periodicity of pain can help local- illness. ize the level of obstruction: pain from proximal intestinal obstruc- There are several different methods of classifying mechanical tion has a short periodicity (3 to 4 minutes), and distal small obstruction: acute versus chronic, partial versus complete, simple bowel or colonic pain has longer intervals (15 to 20 minutes) versus closed-loop, and gangrenous versus nongangrenous. The between episodes of nausea, cramping, and vomiting. importance of these classiﬁcations is that the natural history of Abdominal distention, nausea, and vomiting usually develop the condition, its response to treatment, and the associated mor- after pain has already been felt for some time.The patient should bidity and mortality all vary according to which type of obstruc- be asked what degree of abdominal distention is present and tion is present. whether there has been a sudden or rapid change. Distention When chyme and gas can traverse the point of obstruction, developing over many weeks suggests a chronic process or pro- obstruction is partial; when this is not the case, obstruction is com- gressive partial obstruction. Massive abdominal distention cou- plete.When the bowel is occluded at a single point along the intesti- pled with minimal crampy pain, nausea, and vomiting suggests nal tract, leading to intestinal dilatation, hypersecretion, and bacte- long-standing intermittent mechanical obstruction or some form rial overgrowth proximal to the obstruction and decompression of chronic intestinal pseudo-obstruction. The combination of a distal to the obstruction, simple obstruction is present.When a seg- gradual change in bowel habits, progressive abdominal disten- ment of bowel is occluded at two points along its course by a sin- tion, early satiety, mild crampy pain after meals, and weight loss gle constrictive lesion that occludes both the proximal and the dis- also suggests chronic partial mechanical bowel obstruction. If the tal end of the intestinal loop as well as traps the bowel’s mesentery, patient has undergone evaluation for similar symptoms before, closed-loop obstruction is present. When the blood supply to a any previous abdominal radiographs or contrast studies should closed-loop segment of bowel becomes compromised, leading to be reviewed. The patient should be asked when ﬂatus was last ischemia and eventually to bowel wall necrosis and perforation, passed: failure to pass ﬂatus may signal a transition from partial strangulation is present. The most common causes of simple to complete bowel obstruction. Patients with an intestinal stoma obstruction are intra-abdominal adhesions, tumors, and strictures; (ileostomy or colostomy) who present with signs and symptoms the most common causes of closed-loop obstruction are hernias, of obstruction often report abdominal distention and pain after a adhesions, and volvulus. sudden change in stomal output of stool, liquid, or air. One of the most difﬁcult tasks in general surgery is deciding The patient should also be asked about (1) previous episodes of when to operate on a patient with intestinal obstruction.The pur- bowel obstruction, (2) previous abdominal or pelvic operations, (3) pose of the following discussion is to outline a safe, efﬁcient, and a history of abdominal cancer, and (4) a history of intra-abdominal cost-effective stepwise approach to making this often difﬁcult inﬂammation (e.g., inﬂammatory bowel disease, cholecystitis, pan- decision and to optimizing the management of patients with this creatitis, pelvic inﬂammatory disease, or abdominal trauma). Any problem. Absolutes are few and far between: treatment must of these factors increases the chance that the obstruction is sec- always be highly individualized. Consequently, the following rec- ondary to an adhesion or recurrent cancer. Obstructive symptoms ommendations are intended only as guidelines, not as surgical that come and go suddenly over several days in a patient older than dicta. 65 years should increase the index of suspicion for gallstone ileus.4
© 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 Gastrointestinal Tract and Abdomen 4 Intestinal Obstruction — 2 gic side effects. Patients who are receiving chemotherapy or have Table 1—Causes of Ileus undergone abdominal radiation therapy are prone to ileus. Severe infection, ﬂuid and electrolyte imbalances, narcotic and Intra-abdominal causes anticholinergic medications, and intra-abdominal inﬂammation Intraperitoneal problems of any origin may be implicated. Acute massive abdominal dis- Peritonitis or abscess tention in a hospitalized patient usually results from acute gastric Inflammatory condition distention, small bowel ileus, or acute colonic pseudo-obstruc- Mechanical: operation, foreign body tion. Excessive anticoagulation can lead to retroperitoneal, intra- Chemical: gastric juice, bile, blood abdominal, or intramural hematoma that can cause mechanical Autoimmune: serositis, vasculitis obstruction or ileus. Finally, there are speciﬁc problems that tend Intestinal ischemia: arterial or venous, sickle-cell disease to arise in the postoperative period; these are discussed more Retroperitoneal problems fully elsewhere [see Urgent Operation, Early Postoperative Pancreatitis Technical Complications, and No Operation, Early Postoperative Retroperitoneal hematoma Obstruction, below]. Spine fracture Aortic operation PHYSICAL EXAMINATION Renal colic AND RESUSCITATION Pyelonephritis The initial steps in the Metastasis physical examination are (1) Extra-abdominal causes developing a gestalt of the Thoracic problems patient’s illness and (2) Myocardial infarction assessing the patient’s vital Pneumonia signs, hydration status, and Congestive heart failure cardiopulmonary system. A nasogastric tube, a Foley catheter, and Rib fractures an I.V. line are placed immediately while the physical examination Metabolic abnormalities is in progress.The volume and character of the gastric aspirate and Electrolyte imbalance (e.g., hypokalemia) urine are noted. A clear, gastric efﬂuent is suggestive of gastric out- Sepsis let obstruction. A bilious, nonfeculent aspirate is a typical sign of Lead poisoning medial to proximal small bowel obstruction or colonic obstruction Porphyria Hypothyroidism Hypoparathyroidism Uremia Table 2—Causes of Small Bowel Medicines Obstruction in Adults Opiates Anticholinergics Extrinsic causes Alpha agonists Adhesions* Antihistamines Hernias (external, internal [paraduodenal], incisional)* Catecholamines Metastatic cancer* Spinal cord injury or operations Volvulus Head, thoracic, or retroperitoneal trauma Intra-abdominal abscess Chemotherapy, radiation therapy Intra-abdominal hematoma Pancreatic pseudocyst Intra-abdominal drains Tight fascial opening at stoma If the patient has experienced episodes of obstruction before, one should ask about the etiology and the response to treatment. If the Intraluminal causes patient has ever undergone an abdominal operation, one should Tumors* try to obtain and read the operative report, which can provide a Gallstones great deal of helpful information (e.g., description of adhesions, Foreign body assessment of their severity, and evaluation of intra-abdominal Worms pathology and anatomy). If abdominal cancer was present, one Bezoars should ﬁnd out what operation was performed and attempt to Intramural abnormalities determine the likelihood of intra-abdominal recurrence. Tumors The clinical setting often provides clues to the cause and type Strictures of bowel obstruction. In hospitalized patients, there is likely to be Hematoma an associated medical condition or metabolic derangement that Intussusception led to obstruction. A thorough review of the patient’s medical Regional enteritis history and hospital course should be undertaken to identify pre- Radiation enteritis cipitating events that could have led to intestinal obstipation. One should ask the patient about any previous abdominal irradiation *Approximately 85% of all small bowel obstructions are secondary to adhesions, and should note and take into account all medications the patient hernias, or tumors. is taking, especially anticoagulants and agents with anticholiner-
© 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 Gastrointestinal Tract and Abdomen 4 Intestinal Obstruction — 3 Signs and symptoms Clinical history of intestinal obstruction Assess character, severity, location, and periodicity of pain. Signs and symptoms include Assess degree of abdominal distention, and ask about any abdominal pain or distention, nausea, sudden or rapid changes. vomiting, and obstipation. Ask about changes in bowel habits, weight loss, and last passage of flatus. Ask about (1) previous obstruction, (2) previous abdominal or pelvic procedures, (3) abdominal cancer, (4) intra- abdominal inflammation. Consider clinical setting: ask about medical conditions or metabolic derangements, exposure to radiation, all medications. Immediate postoperative state is special situation. Mechanical obstruction Classification of obstruction Determine whether obstruction Nonmechanical obstruction The most useful distinction is is complete or partial. mechanical vs. nonmechanical. Terminally ill patients: consider no treatment other than comfort measures and hospice care. Ileus Pseudo-obstruction [See Figure 12.] [See Figure 13.] Complete obstruction Partial obstruction Operate immediately. Look for associated factors that may necessitate immediate operation. Immediate operation indicated Indications include peritonitis, incarcerated hernia, suspected or confirmed strangulation, pneumatosis cystoides intestinalis, sigmoid volvulus with systemic toxicity or peritoneal irritation, small bowel volvulus, colonic volvulus above sigmoid, and fecal impaction. Operate immediately. Assessment of Intestinal Obstruction Urgent operation Indications include • Lack of response to 24–48 hr of nonoperative therapy (increasing abdominal pain, distention, or tenderness; NG aspirate changing from nonfeculent to feculent; ↑ proximal small bowel distention with ↓ distal gas). • Early technical complications of operation (abscess, phlegmon, hematoma, hernia, intussusception, anastomotic obstruction).
© 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 Gastrointestinal Tract and Abdomen 4 Intestinal Obstruction — 4 Physical exam and resuscitate as necessary Develop gestalt of patient’s illness, and assess patient’s vital signs, hydration, and cardiopulmonary system. Place NG tube, Foley catheter, and I.V. line immediately. Assess volume and character of NG aspirate, and measure urine output. Replace lost fluid with isotonic saline or lactated Ringer solution. Look for signs of abscess, pneumonia, or myocardial infarction, and be alert for dyspnea, labored breathing, or jaundice. Perform systematic abdominal examination: observation → auscultation → palpation and percussion. Look for abdominal masses, tenderness, incisions, and hernias; assess bowel sounds; examine rectum for masses, fecal impaction, and occult blood. Investigative studies Obtain chest x-rays and abdominal films. If uncertainty about presence or nature of colonic obstruction remains, perform sigmoidoscopy and barium enema examination. Measure serum electrolytes and creatinine, determine hematocrit, and order coagulation profile. If ileus is suspected, measure serum magnesium and calcium and order urinalysis. Perform CT (with oral or I.V. contrast agents), fast MRI, or abdominal ultrasonography. Immediate operation not indicated Manage initially with nonoperative measures. Reassess patient every 4 hr. For partial obstruction, administer oral diatrizoate meglumine. Look for changes in pain, abdominal findings, and volume and character of NG aspirate. Repeat abdominal x-rays, and look for changes in gas distribution, pneumatosis cystoides intestinalis, and free intraperitoneal air. Classify patient’s condition as improved, unchanged, or worse. Decide whether operative treatment is necessary and, if so, whether it should be done on urgent or elective basis. Arrival of contrast agent in right colon within 24 hr is highly predictive of successful resolution of adhesive obstruction without operation. No operation Elective operation Conditions that typically resolve with nonoperative Indications include nontoxic, nontender sigmoid volvulus with therapy include adhesive obstruction (unless it sigmoidoscopically managed obstruction; recurrent adhesive does not improve in 12 hr), early postoperative or stricture-related small bowel obstruction; partial colonic obstruction (unless it does not improve in 2 wk), obstruction unresponsive to 24 hr of nonoperative therapy; and various inflammatory conditions (IBD, radiation development and resolution of small bowel obstruction in patient enteritis, diverticulitis, acute Crohn disease). who has never undergone abdominal operation.
© 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 Gastrointestinal Tract and Abdomen 4 Intestinal Obstruction — 5 Approximately 70% of patients with bowel obstruction have symmetrical tenderness, whereas fewer than 50% have rebound Table 3—Causes of Colonic Obstruction tenderness, guarding, or rigidity.3 The traditional teaching is that Common causes localized tenderness and guarding indicate underlying strangulat- Cancer (primary, anastomotic, metastatic) ed bowel; however, prospective studies have demonstrated that Volvulus these physical ﬁndings are neither speciﬁc nor sensitive for detect- Diverticulitis ing underlying strangulation5 or even obstruction.3 Nevertheless, Pseudo-obstruction most surgeons still believe that guarding, rebound tenderness, and Hernia localized tenderness reﬂect underlying strangulation and there- Anastomotic stricture fore are indications for operation. Patients with ileus tend to have generalized abdominal tenderness that cannot be distinguished Unusual causes from the tenderness of mechanical obstruction. Gentle percussion Intussusception is performed over all quadrants of the abdomen to search for areas Fecal impaction of dullness (suggestive of an underlying mass), tympany (sugges- Strictures (from one of the following) tive of underlying distended bowel), and peritoneal irritation. Inflammatory bowel disease A thorough search is made for inguinal, femoral, umbilical, and Endometriosis incisional hernias. The rectum is examined for masses, fecal Radiation therapy impaction, and occult blood. If the patient has an ileostomy or a Ischemia colostomy, the stoma is examined digitally to make sure that there Foreign body is no obstruction at the level of the fascia. Extrinsic compression by a mass Pancreatic pseudocyst Hematoma Investigative Studies Metastasis Primary tumors IMAGING One should obtain a chest x-ray in all patients with with a competent ileocecal valve. A feculent aspirate is a typical bowel obstruction to exclude sign of distal small bowel obstruction.Volume replacement, if nec- a pneumonic process and to essary, is initiated with isotonic saline solution or lactated Ringer look for subdiaphragmatic solution. Urine output must be adequate (at least 0.5 ml/kg/hr) air. In most cases, supine, upright, or lateral decubitus ﬁlms of the before the patient can be taken to the OR; supplemental potassi- abdomen can distinguish the type of obstruction present um chloride (40 mEq/L) is administered once this is achieved. (mechanical or nonmechanical, partial or complete) and establish Fever may be present, suggesting that the obstruction may be the location of the obstruction (stomach, small bowel, or colon). A a manifestation of an intra-abdominal abscess. Signs of pneumo- useful technique for evaluating abdominal radiographs is to look nia or myocardial infarction should be sought: these conditions, systematically for intestinal gas along the normal route of the GI like intestinal obstruction, can have upper abdominal pain, dis- tract, beginning at the stomach, continuing through the small tention, nausea, and vomiting as presenting symptoms. Dyspnea bowel, and, ﬁnally, following the course of the colon to the rectum. and labored breathing may occur secondary to severe abdominal The following questions should be kept in mind as this is done. distention or pain, in which case immediate relief should be pro- • Are there abnormally dilated loops of bowel, signs of small bowel vided by placing the patient in the lateral decubitus position and dilatation, or air-ﬂuid levels? offering narcotics as soon as the initial physical examination is • Are air-ﬂuid levels and bowel loops in the same place on supine performed. Jaundice raises the possibility of gallstone ileus or and upright ﬁlms? metastatic cancer. • Is there gas throughout the entire length of the colon (suggestive Examination of the abdomen proceeds in an orderly manner of ileus or partial mechanical obstruction)? from observation to auscultation to palpation and percussion. • Is there a paucity of distal colonic gas or an abrupt cutoff of The patient is placed in the supine position with the legs ﬂexed at colonic gas with proximal colonic distention and air-ﬂuid levels the hip to decrease tension on the rectus muscles. The degree of (suggestive of complete or near-complete colonic obstruction)? abdominal distention observed varies, depending on the level of • Is there evidence of strangulation (e.g., thickened small bowel obstruction: proximal obstructions may cause little or no disten- loops, mucosal thumb printing, pneumatosis cystoides intesti- tion. Abdominal scars should be noted. Abdominal asymmetry or nalis, or free peritoneal air)? a protruding mass suggests an underlying malignancy, an abscess, • Is there massive distention of the colon, especially of the cecum or closed-loop obstruction. The abdominal wall should be or sigmoid (suggestive of either volvulus or pseudo-obstruction)? observed for evidence of peristaltic waves, which are indicative of • Are there any biliary or renal calculi, and is there any air in the acute small bowel obstruction. biliary tree (suggestive of gallstone ileus6 or a renal stone that Auscultation should be performed for at least 3 to 4 minutes to could be causing ileus)? determine the presence and quality of bowel sounds. High- pitched bowel tones, tingles, and rushes are suggestive of an It is important to be able to distinguish between small and large obstructive process, especially when temporally associated with bowel gas. Gas in a distended small bowel outlines the valvulae waves of crampy pain, nausea, or vomiting.The absence of bowel conniventes, which traverse the entire diameter of the bowel lumen tones is typical of intestinal paralysis but may also indicate intesti- [see Figure 1]. Gas in a distended colon, on the other hand, outlines nal fatigue from long-standing obstruction, closed-loop obstruc- the colonic haustral markings, which cross only part of the bowel tion, or pseudo-obstruction. lumen and typically interdigitate [see Figures 2 and 3]. Distended
© 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 Gastrointestinal Tract and Abdomen 4 Intestinal Obstruction — 6 Figure 2 Radiograph from a patient with acute colonic pseudo- obstruction shows a dilated colon with haustral markings (white arrow) and edematous small bowel loops (black arrow). Air extends down to the distal sigmoid. This picture is also consistent with rectal obstruction, which could have been excluded by rigid Figure 1 Supine radiograph from a patient with complete small sigmoidoscopy. bowel obstruction shows distended small bowel loops in the cen- tral abdomen with prominent valvulae conniventes (small white arrow). Bowel wall between the loops is thickened and edematous (large white arrow). No air is seen in the colon or the rectum. Note the presence of an isolated small bowel loop in the right lower quadrant (black arrow), which is seen ﬁxed in the same location on upright ﬁlms, as shown in Figure 4. A small bowel loops usually occupy the central abdomen [see Figure 1], whereas distended large bowel loops are typically seen around the periphery [see Figure 2]. In patients with ileus, distention usual- ly extends uniformly throughout the stomach, the small bowel, and D the colon [see Figure 3], and air-ﬂuid levels may be found in the colon and the small intestine. Patients with gastric outlet obstruction or gastric atony typical- ly have a giant gastric bubble if no nasogastric tube has been placed, with little or no air in the small bowel or the colon. B Patients with mechanical small bowel obstruction usually have C multiple air-ﬂuid levels, with distended bowel loops of varying sizes arranged in an inverted U conﬁguration [see Figure 4]. A dilated loop of small bowel appearing in the same location on supine and upright ﬁlms suggests obstruction of a ﬁxed segment of bowel by an adhesion or an internal hernia [see Figures 1 and 4]. Small bowel obstruction is often accompanied by a paucity of Figure 3 Radiograph from a patient with postoperative ileus gas in the colon. The complete absence of colonic gas is strongly shows massive gastric distention (A), distended small bowel loops suggestive of complete small bowel obstruction; however, the (B), air throughout the colon, mild dilatation of the sigmoid colon presence of colonic gas does not exclude complete small bowel (C) with air mixed with stool, and a haustral fold in the apex of obstruction, in that there may have been unevacuated gas distal the sigmoid colon (D).
© 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 Gastrointestinal Tract and Abdomen 4 Intestinal Obstruction — 7 creatinine concentration, and the coagulation proﬁle (prothrom- bin time [or international normalized ratio—INR] and platelet count) are helpful in determining the severity of volume depletion and guiding resuscitative efforts. If ileus is suspected, serum mag- nesium and calcium levels should be measured, and urinalysis should be done to check for hematuria. Determination of Need for Operation and Classiﬁcation of Obstruction The combination of a thorough history, a carefully performed physical exami- nation, and correctly interpreted abdominal radiographs usually allows one to identify the type of bowel obstruction present and to decide whether a patient requires immediate, urgent, or delayed operation [see Table 4] or can safely be treated initially with nonoperative measures. To this end, it is particularly impor- tant and useful to stratify patients into those with mechanical obstruction and those with nonmechanical obstruction. In patients with mechanical bowel obstruction, an effort should be made to determine whether the obstruction is complete or par- tial. Except for a few clinical situations, patients with complete bowel obstruction require immediate operation; conversely, patients with partial bowel obstruction rarely do. Finally, an effort should be made to establish the level and cause of obstruction because these factors often help guide therapy and affect the probability of success in response to speciﬁc therapeutic inter- vention. Patients with nonmechanical obstruction, which derives from ileus or pseudo-obstruction [see Ileus and Pseudo-obstruc- tion, below], do not require immediate operation. Figure 4 Upright radiograph from the same patient as the ADJUNCTIVE TESTS FOR EQUIVOCAL SITUATIONS supine radiograph in Figure 1 shows multiple air-ﬂuid levels of varying size arranged in inverted Us. In the right lower pelvis, a Sigmoidoscopy loop of small bowel is seen in exactly the same location as on the supine abdominal ﬁlm (black arrow), a ﬁnding suggestive of adhe- When one is uncertain whether the obstruction is mechanical sive obstruction. or not on the basis of the information in hand, additional diag- nostic measures are immediately indicated. When large amounts of colonic air extend down to the rectum, ﬂexible or rigid sig- moidoscopy will readily exclude a rectal or distal sigmoid to a point of complete obstruction before the radiograph was obstruction. Care must be exercised to avoid insufﬂating large taken. On the other hand, if repeat radiographs demonstrate amounts of air during endoscopy: excessive insufﬂation can cause decreased or absent colonic or rectal gas in a patient with small overdistention of the colon above the level of the possible obstruc- bowel obstruction who previously had more colonic or rectal gas, tion, which can be counterproductive and harmful. If sigmoid- it is probable that partial obstruction has become complete, and oscopy yields normal ﬁndings but partial colonic obstruction immediate operation is almost always indicated. High-grade seems to be the correct diagnosis, a water-soluble contrast enema obstruction of the colon with an incompetent ileocecal valve may should be administered.7 Barium studies may be harmful in manifest itself as distended small bowel loops with air-ﬂuid levels, patients with acute obstruction when they are performed before thereby mimicking small bowel obstruction. Hence, it is some- the nature of the obstruction (complete or partial) is determined. times necessary to perform a barium enema to exclude colonic Abdominal ultrasonography, though not as deﬁnitive as a con- obstruction. trast examination, is also able to diagnose suspected colonic Massive gaseous distention of the colon is usually secondary to obstruction in 85% of patients.8 distal colonic or rectal obstruction, volvulus, or pseudo-obstruction [see Figures 2, 5, 6, and 7]. There are well-deﬁned radiographic cri- Ultrasonography, Computed Tomography, and Fast Magnetic teria that are highly sensitive and speciﬁc for sigmoid volvulus.6 If Resonance Imaging there is any uncertainty regarding the presence, type, or level of Abdominal radiographs can be entirely normal in patients with colonic obstruction, immediate sigmoidoscopy followed by barium complete, closed-loop, or strangulation obstruction.9 Therefore, if enema is diagnostic. the patient’s clinical proﬁle and the results of physical examination are consistent with intestinal obstruction despite normal abdomi- LABORATORY TESTS nal radiographs, abdominal ultrasonography, CT scanning, or fast Serum electrolyte concentrations, the hematocrit, the serum MRI should be performed immediately.9-18 All three modalities are
© 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 Gastrointestinal Tract and Abdomen 4 Intestinal Obstruction — 8 a highly sensitive and speciﬁc for intestinal obstruction when per- formed properly and interpreted by experienced clinicians. Two prospective clinical trials found ultrasonography to be as sensitive as and more speciﬁc than abdominal radiography in diagnosing intestinal obstruction.19,20 Ultrasonography, CT, and fast MRI are all capable of detecting the cause of the obstruction, as well as the presence of closed-loop or strangulation obstruction.8,10,15-18,21-24 Sonographic criteria have been established for small bowel and colonic obstruction8,21,22: (1) simultaneous observation of dis- tended and collapsed bowel segments, (2) free peritoneal ﬂuid, (3) inspissated intestinal contents, (4) paradoxical pendulating peristalsis, (5) highly reﬂective ﬂuid within the bowel lumen, (6) bowel wall edema between serosa and mucosa, and (7) a ﬁxed mass of aperistaltic, ﬂuid-ﬁlled, dilated intestinal loops. One group of authors has recommended that when abdominal radio- graphs are inconclusive or normal in patients with suspected colonic obstruction, ultrasonography, rather than CT or barium enema, should be the next diagnostic step.8 Ultrasonography is well suited to critically ill patients: because it can be performed at the bedside, the risk associated with transport to the radiology suite is avoided. Given that ultrasonography is relatively inexpen- sive, is easy and quick to perform, and often can provide a great deal of information about the location, nature, and severity of the obstruction, it should be employed early on in the evaluation of all patients with intestinal obstruction.19 Several authors have recommended that patients with suspected small bowel obstruction and equivocal plain abdominal ﬁlms under- go CT scanning before a small bowel contrast series is ordered.11-14 CT scanning has several advantages over a small bowel contrast examination in this setting: (1) it can ascertain the level of obstruc- tion, (2) it can assess the severity of the obstruction and determine b its cause, and (3) it can detect closed-loop obstruction and early strangulation [see Figures 8,9,10,and 11]. CT can also detect inﬂam- matory or neoplastic processes both outside and inside the peri- toneal cavity and can visualize small amounts of intraperitoneal air or pneumatosis cystoides intestinalis not seen on conventional ﬁlms [see Figure 10]. Prospective studies have demonstrated that the accu- racy of CT in diagnosing bowel obstruction is higher than 95% and that its sensitivity and speciﬁcity are each higher than 94%.23,24 CT scanning distinguishes colonic mechanical obstruction from pseu- do-obstruction more accurately than conventional ﬁlms do and thus is the preferred modality in many cases.25 There is evidence to indicate that fast MRI with T2-weighted images is more sensitive, speciﬁc, and accurate than contrast- enhanced helical CT scanning in establishing the location and cause of bowel obstruction.17 The advantages of fast MRI over helical CT scanning are (1) that the image acquisition time is short (1 to 2 seconds per slice), which means that the image can be acquired in the space of a single held breath, and (2) that no contrast agents are required. In addition, because of its multipla- nar capability, MRI is also more effective at demonstrating the transition point of the obstruction. When helical CT scanning is nondiagnostic in a patient with suspected bowel obstruction and fast MRI is not available, a small bowel follow-through examina- tion with dilute barium is often useful.14 Figure 5 (a) Radiograph from a patient with massive sigmoid volvulus shows a distended ahaustral sigmoid loop (white arrow), inferior convergence of the walls of the sigmoid loop to the left of the midline, and approximation of the medial walls of the sigmoid loop as a summation line (black arrow). (b) Barium enema of the colon shows a tapered obstruction at the rectosigmoid junction with a typical bird’s-beak deformity (black arrow).
© 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 Gastrointestinal Tract and Abdomen 4 Intestinal Obstruction — 9 a Figure 7 Shown is a radiograph from a patient with complete colonic obstruction from an obstructing carcinoma in the descending left colon with proximal air-ﬂuid levels. The absence of air distally in the rectum or the sigmoid is suggestive of com- b plete obstruction. The ileocecal valve is competent, and thus, there is no small bowel air. Contrast Studies Enteroclysis (direct injection of BaSO4 into the small bowel) is generally considered the most sensitive method of distinguishing between ileus and partial mechanical small bowel obstruction: it has a diagnostic sensitivity of 87% for adhesive obstruction.26,27 Many surgeons are concerned that injection of barium might cause partial obstruction to progress to complete obstruction; however, there is no evidence that this ever occurs, and one there- fore should not refrain from using barium to diagnose partial small bowel obstruction.28-31 If complete obstruction is identiﬁed, the patient should undergo immediate operation. If partial obstruction is identiﬁed in either the small or the large bowel, the patient is treated accordingly. If (1) mechanical obstruction is not identiﬁed and (2) a point of obstruction, as evidenced by the ﬁnd- ing of both dilated and decompressed intestinal loops, cannot be identiﬁed through abdominal ultrasonography, CT scanning, or fast MRI, then the diagnosis is almost certainly ileus, in which case one’s attention is directed toward identifying and correcting the underlying precipitating cause [see Table 1 and Mechanical Obstruction, No Operation, Adhesive Partial Small Bowel Ob- struction, below]. Mechanical Obstruction TERMINAL ILLNESS Figure 6 (a) Radiograph from a patient with cecal volvulus Patients with a terminal illness (e.g., AIDS or advanced carci- shows a dilated cecum with no air distally in the colorectum. Convergence of the medial walls of the loop (black arrow) points nomatosis) to whom surgical treatment offers little hope of to the right, a typical ﬁnding in cecal volvulus. (b) Barium exami- improved quality or duration of life may choose not to undergo nation demonstrates a bird’s-beak deformity tapering at the point operative intervention for acute bowel obstruction. These patients of volvulus (large white arrow). Note walls of dilated cecum (small should be offered comfort measures, including continuous mor- white arrows). phine infusion, rehydration, and administration of antisecretory
© 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 Gastrointestinal Tract and Abdomen 4 Intestinal Obstruction — 10 die of malignant bowel obstruction in a hospital should be offered Table 4—Guidelines for Operative hospice care or home visiting nurse services with continuous octreotide infusion, I.V. rehydration, and gastrostomy decompres- and Nonoperative Therapy sion.37,38 Three prospective, randomized clinical trials demonstrat- ed that octreotide signiﬁcantly attenuated the severity of nausea Situations necessitating emergent operation Incarcerated, strangulated hernias and vomiting and the degree of subjective discomfort in patients Peritonitis with inoperable obstruction and permitted the discontinuance of Pneumatosis cystoides intestinalis nasogastric tube decompression.33,34,39 One of these studies also Pneumoperitoneum demonstrated that octreotide signiﬁcantly reduced the degree of Suspected or proven intestinal strangulation fatigue and anorexia experienced.39 When long-term gastric Closed-loop obstruction decompression is required for palliation in a terminally ill patient, Nonsigmoid colonic volvulus percutaneous endoscopic gastrostomy or jejunostomy should be Sigmoid volvulus associated with toxicity or peritoneal signs considered [see 5:18 Gastrointestinal Endoscopy].40 Attention must Complete bowel obstruction always be paid to quality-of-life issues and to the patient’s potential interest in pursuing nonoperative forms of palliation. For many ter- Situations necessitating urgent operation minally ill or incurable patients with bowel obstruction, the most Progressive bowel obstruction at any time after nonoperative humane and sensible treatment comprises nothing more than measures are started instituting palliative measures such as those described. Failure to improve with conservative therapy within 24–48 hr Early postoperative technical complications IMMEDIATE OPERATION Situations in which delayed operation is usually safe All patients with complete Immediate postoperative obstruction bowel obstruction, whether Sigmoid volvulus successfully decompressed by sigmoidoscopy of the small intestine or the Acute exacerbation of Crohn disease, diverticulitis, or radiation large, should undergo imme- enteritis diate operation unless extra- Chronic, recurrent partial obstruction ordinary circumstances (e.g., Paraduodenal hernia diffuse carcinomatosis, ter- Gastric outlet obstruction minal illness, or sigmoid volvulus that responds to sigmoidoscop- Postoperative adhesions ic decompression) are present. If one attempts to manage com- Resolved partial colonic obstruction plete intestinal obstruction nonoperatively, one risks delaying deﬁnitive treatment of patients with intestinal ischemia and sub- jecting them to signiﬁcantly increased morbidity and mortality agents.32-34 In some of these patients, endoscopic deployment of should perforation or severe infection develop.5,41 plastic stents may relieve high-grade partial obstruction, thus ren- Immediate operation is also indicated when bowel obstruction dering laparotomy unnecessary.35,36 Patients who do not wish to is associated with peritonitis; incarcerated strangulated hernias; Figure 8 CT scan from a patient with partial small bowel obstruction Figure 9 CT scan from a patient with adhesive partial small shows distended, ﬂuid-ﬁlled loops of small bowel with air-ﬂuid levels, bowel obstruction shows massively dilated small intestine (black hyperemia, and bowel wall thickening (large white arrow). Note the arrow) proximal to a thick adhesive band (large white arrow) discrepancy in caliber between dilated small bowel and decompressed and decompressed small bowel distal to the adhesion (dashed small bowel (dashed white arrow) and the stranding (small black white arrow). The patient was operated on because of the low arrow) in the small bowel mesentery. Air in a decompressed descend- probability that this obstruction would resolve with conservative ing colon (large black arrow) is indicative of partial obstruction. management.
© 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 Gastrointestinal Tract and Abdomen 4 Intestinal Obstruction — 11 Abdominal ultrasonography can also identify edematous, hem- orrhagic loops of intestine. Accordingly, whenever one is con- cerned about possible strangulation or closed-loop obstruction but is not yet committed to taking the patient immediately to the OR, an ultrasonogram or a CT scan should be obtained. In fact, given that ultrasonography, CT, and fast MRI are the only well- B established means of diagnosing strangulation obstruction short of exploratory laparotomy or laparoscopy, an argument can be made that one of these modalities should be performed in all patients who have been admitted to the hospital with bowel obstruction and are initially being treated nonoperatively. Many surgeons base the decision whether to operate on patients with bowel obstruction on the presence or absence of the so-called classic signs of strangulation obstruction—continuous abdominal pain, fever, tachycardia, peritoneal signs, and leukocy- tosis—and on their clinical experience. Unfortunately, these clas- sically taught signs, even in conjunction with abdominal x-rays and clinical judgment, are incapable of reliably detecting closed- loop or gangrenous bowel obstruction.5,28,41,44 In fact, one pro- Figure 10 CT scan from a patient with partial small bowel spective clinical trial concluded that the ﬁve classic signs of stran- obstruction from cancer shows distended small bowel (dashed gulation obstruction and experienced clinical judgment were not white arrows) proximal to a mass (small white arrow). There is air in the cecum (black arrow), the transverse colon, and the sensitive for, speciﬁc for, or predictive of strangulation5: in more descending colon (large white arrow). The small bowel is maxi- than 50% of the patients who had intestinal strangulation, the mally dilated, with hyperemic, edematous bowel wall (B) just condition was not recognized preoperatively. Such ﬁndings sug- proximal to an obstructing recurrent colon carcinoma. Even gest that early nonoperative recognition of intestinal strangulation though plain radiographs showed partial small bowel obstruction, is not feasible without ultrasonography, CT, or fast MRI. this CT scan led to early operation because continued nonopera- tive management would not resolve the problem. Incarcerated or Strangulated Hernias A hernia that is incarcerated, tender, erythematous, warm, or edematous is an indication for immediate operation. Primary suspected or conﬁrmed strangulation; pneumatosis cystoides or incisional hernias may not be palpable in obese patients, in intestinalis; sigmoid volvulus accompanied by systemic toxicity or which case ultrasonography, CT scanning, or fast MRI should be peritoneal irritation; colonic volvulus above the sigmoid colon; or performed. fecal impaction. These conditions will not resolve without opera- tion and are associated with increased morbidity, mortality, and cost if diagnosis and treatment are delayed. The only time one would not operate immediately on any patient with one of these diagnoses is when the patient requires cardiopulmonary stabiliza- tion, additional resuscitation, or both. Whenever there is any doubt as to the presence of any of these conditions, additional diagnostic tests (e.g., ultrasonography, CT, fast MRI, or contrast studies) are indicated to conﬁrm or exclude them. Strangulation and Closed-Loop Obstruction Morbidity and mortality from intestinal obstruction vary sig- niﬁcantly and depend primarily on the presence of strangulation and subsequent infection. Strangulation obstruction occurs in approximately 10% of all patients with small intestinal obstruc- tion. It carries a mortality of 10% to 37%, whereas simple obstruction carries a mortality of less than 5%.5,28,42,43 Early recognition and immediate operative treatment of strangulation obstruction are the only current means of decreasing this mortal- ity. Strangulation obstruction occurs most frequently in patients with incarcerated hernias, closed-loop obstruction, volvulus, or complete bowel obstruction; hence, identiﬁcation of any of these speciﬁc causes of obstruction is an important and clear indication Figure 11 Early closed-loop small bowel obstruction CT scan for immediate operation. Radiographic evidence of pneumatosis from a patient with early closed-loop obstruction of the small cystoides intestinalis or free intraperitoneal air in a patient with a intestine shows markedly edematous, hyperemic small bowel, a clinical picture of bowel obstruction is indicative of strangulation, ﬁnding indicative of early strangulation (white arrow). The patient perforation, or both and constitutes an indication for operation. had minimal symptoms, and there was air in the transverse colon High-quality abdominal CT with I.V. contrast can detect ad- and the descending colon (a ﬁnding indicative of partial small vanced strangulation and identify early, reversible strangulation bowel obstruction); however, the ﬁnding of gangrenous, nonperfo- [see Figure 11].13,15,16 rated small bowel on this CT scan led to early operation.
© 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 Gastrointestinal Tract and Abdomen 4 Intestinal Obstruction — 12 Nonsigmoid Volvulus and Sigmoid Volvulus with Systemic tric decompression, analgesics, and octreotide. Such therapy is Toxicity or Peritoneal Signs successful in most cases, especially if the cause of obstruction All intestinal volvuli are closed-loop obstructions and thus is postoperative adhesions, but there is always the risk that carry a high risk of intestinal strangulation, infarction, and perfo- complete bowel obstruction or strangulation already exists but ration. Patients typically present with acute, colicky abdominal is undetected. Furthermore, there is the risk that while the pain, massive distention, nausea, and vomiting. Sigmoid volvulus patient is being observed, partial obstruction will progress to is the most common form of colonic volvulus, followed by cecal complete obstruction or strangulation and perforation will volvulus. Abdominal radiographs are fairly diagnostic for colonic develop. It is therefore crucial to be alert to changes in the volvulus [see Figures 5 and 6]. In contrast, small bowel volvulus patient’s condition. may not be visualized on plain radiographs, because the closed Repeated examination of the abdomen by the same clinician loop ﬁlls completely with ﬂuid and no air-ﬂuid level can be seen. is the most sensitive way of detecting progressive obstruction. Small bowel volvulus is readily detected by ultrasonography or Examinations should be performed no less frequently than every CT scanning; one or both of these procedures should be per- 3 hours. If abdominal pain, tenderness, or distention increases or formed in patients presenting with signs and symptoms of bowel the gastric aspirate changes from nonfeculent to feculent, obstruction and normal abdominal radiographs. Small bowel abdominal exploration is usually indicated. Abdominal radi- volvulus is an indication for immediate operation. ographs should be repeated every 6 hours after nasogastric If one observes signs of systemic toxicity, a bloody rectal dis- decompression and reviewed by the surgeon who is following the charge, fever, leukocytosis, or peritoneal irritation in a patient with patient. If proximal small bowel distention increases or distal sigmoid volvulus, the patient should undergo immediate opera- intestinal gas decreases, nonoperative therapy is less likely to be tion; if all of these signs are absent, the patient should undergo sig- successful; in these circumstances, early operative intervention moidoscopy.When there are no signs of peritonitis or generalized should be seriously considered. Conversely, if the patient’s con- toxicity, sigmoidoscopic decompression is safe and effective in dition appears stable or improved and x-rays indicate that the more than 95% of patients with sigmoid volvulus.45 If mucosal obstruction either has resolved somewhat or at least is no worse, gangrene or a bloody efﬂuent is noted at the time of sigmoid- it is generally safe to continue nonoperative care for another 12 oscopy, immediate operative intervention is necessary even in the to 24 hours. If the clinical picture is stable after 24 hours of absence of any clinical signs or symptoms of strangulation. After observation, one must decide whether to operate or to continue sigmoidoscopy, the patient can undergo elective bowel prepara- nonoperative therapy. Clinical judgment and experience, cou- tion and a single-stage sigmoid resection before being discharged pled with thorough and accurate assessment of the patient’s from the hospital. If, however, clinical toxicity, a bloody rectal dis- underlying diagnosis and clinical condition, have traditionally charge, fever, or peritoneal irritation arises at any time after sig- been the most reliable guides for making this decision. moidoscopic decompression while the patient is being prepared Currently, however, it appears that the decision whether to oper- for an elective procedure, immediate operation is indicated. ate can be made more cost-effectively and reliably on the basis Patients with volvulus proximal to the sigmoid colon should of abdominal imaging studies [see No Operation, Adhesive undergo immediate operation regardless of whether peritoneal Partial Small Bowel Obstruction, below]. irritation is present. The incidence of strangulation infarction is Early Postoperative Technical Complications high in such patients, and nonoperative therapy often fails. If the diagnosis of nonsigmoid colonic volvulus is in doubt, a barium When normal bowel function initially returns after an abdom- enema is indicated to exclude colonic pseudo-obstruction. inal operation but then is replaced by a clinical picture suggestive of early postoperative mechanical obstruction, the explanation Fecal Impaction may be a technical complication of the operation (e.g., phlegmon, Complete colonic obstruction secondary to fecal impaction in abscess, intussusception, a narrow anastomosis, an internal her- the rectum can sometimes be successfully relieved through dis- nia, or obstruction at the level of a stoma). An early, aggressive impaction at the bedside; however, this can be difﬁcult and diagnostic workup should be performed to identify or exclude extremely uncomfortable for the patient. The most expeditious these problems because they are unlikely to respond to nasogas- and successful method of relieving the obstruction is to disimpact tric decompression or other forms of conservative management. the patient while he or she is under general or spinal anesthesia. It is critical to know exactly what was done within the abdomen In one study, the pulsed-irrigated enhanced-evacuation (PIEE) in the course of the operation.To this end, one should try to speak procedure, which can be performed at the bedside, successfully directly with the operating surgeon rather than attempt to deduce resolved fecal impaction in approximately 75% of geriatric the needed information from the operative report. patients.46 In another study, administration of a polyethylene gly- If the patient had peritonitis or a colonic anastomosis at the ini- col 3350 solution over 3 days successfully resolved intestinal tial operation, one should order a CT scan to look for an intra- obstruction from fecal impaction in 75% of pediatric patients.47 abdominal abscess. An abscess or a phlegmon at the site of an anastomosis is usually secondary to anastomotic leakage and is an URGENT OPERATION indication for reoperation. CT scanning can also identify intra- abdominal hematomas, which should be evacuated through early Lack of Response to reoperation. In patients recovering from a proctectomy, hernia- Nonoperative Therapy tion of the small bowel through a defect in the pelvic ﬂoor is a within 24 to 48 Hours common cause of intestinal obstruction. Oral contrast studies can It is usually safe to man- help identify patients with an internal hernia, intussusception, or age partial bowel obstruc- anastomotic obstruction and should be performed after the CT tion initially by nonopera- scan. A retrograde barium examination should be performed in tive means: a nihil per os patients thought to have a problem related to a stoma or an (NPO) regimen, nasogas- intestinal anastomosis.When none of the above factors appears to
© 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 Gastrointestinal Tract and Abdomen 4 Intestinal Obstruction — 13 be the cause of the postoperative obstruction, it is reasonable for vation period, the patient must be constantly reevaluated, ideally the surgeon to assume that the obstruction is secondary to post- by the same examiner. Analgesics can be safely administered, and operative adhesions, which are best treated conservatively (see repeat abdominal examinations should be performed at 3-hour below). intervals when the inﬂuence of narcotics has waned. Repeat abdominal x-rays should be obtained no later than 6 hours after NO OPERATION nasogastric decompression, and the pattern of gas distribution In selected patients, non- should be compared with that seen on the admission ﬁlms. A operative management of decrease in intestinal gas distal to a point of obstruction coupled partial small bowel obstruc- with an increase in proximal dilatation suggests that the obstruc- tion is highly successful and tion is worsening; conversely, a decrease in intestinal distention carries an acceptably low coupled with the appearance of more gas distally in the colon sug- mortality. Such patients in- gests that the obstruction is being reduced.The degree of abdom- clude those whose partial inal distention, the passage of ﬂatus, and the nature of the naso- obstruction is secondary to gastric aspirate should be evaluated periodically. If abdominal intra-abdominal adhesions, occurs in the immediate postoperative distention does not decrease or the gastric aspirate changes from period, or derives from an inﬂammatory condition (e.g., inﬂam- bilious to feculent, the patient should be operated on. matory bowel disease, radiation enteritis, or diverticulitis). Experimental and clinical studies suggest that patients under- going nonoperative treatment of bowel obstruction may beneﬁt Adhesive Partial Small Bowel Obstruction from the administration of somatostatin analogues as a result of Adhesions are the major cause of bowel obstruction. the potent effects these substances exert on intestinal sodium, Obstruction resulting from adhesions can occur as early as 1 chloride, and water absorption.57 In one study, animals with either month or as late as 20 years after operation.48 Adhesive partial complete or closed-loop partial small bowel obstruction were small bowel obstruction is treated initially with nasogastric given either long-acting somatostatin or saline; the treatment decompression, I.V. rehydration, and analgesia. Parenteral nutri- group had signiﬁcantly less intestinal distention, less infarction, tion should be begun if one believes that oral or enteral nutrition and longer survival than the control group.57,58 In a prospective, will not be adequate within 5 days. Nonoperative therapy leads to randomized clinical trial evaluating the use of somatostatin in resolution of adhesive partial obstruction in as many as 90% of patients who had complete small bowel obstruction without clin- patients49,50; however, such resolution is followed by recurrence of ical or radiologic evidence of strangulation, the treatment group obstruction in approximately 50% of cases.51,52 When operative was less likely to need operation, had less proximal intestinal dis- adhesiolysis is performed, the mortality is less than 5% for tention, and exhibited decreased mucosal necrosis proximal to the patients with simple obstruction but may be as high as 30% for point of obstruction.59 In other trials, long-acting somatostatin patients with strangulation or necrotic bowel necessitating intesti- analogues and other nonsecretagogues signiﬁcantly decreased the nal resection.48 In view of this substantial difference in mortality, amount of gastric contents aspirated and alleviated the symptoms it is extremely important to be able to conﬁdently distinguish of intestinal obstruction in terminally ill patients with nonopera- obstruction that is likely to resolve with nonoperative treatment ble malignant disease.32,33,37-40 from obstruction that is not. Patients with adhesive partial It should be possible to determine with a high degree of accu- obstruction that can be accurately predicted to resolve with med- racy and safety which patients will require operation for adhesive ical therapy can and should be treated nonoperatively. small bowel obstruction within 24 to 48 hours of admission to the Some studies suggest that the nature of the previous abdomi- hospital. As a rule, patients with closed-loop or complete bowel nal operation or the type of adhesions present may inﬂuence the obstruction, who require immediate or urgent operation, can be probability that the obstruction will not respond to medical ther- readily identiﬁed by means of abdominal CT or MRI.12-14,17,18 For apy.53-57 Operations associated with a lower likelihood of response the remaining patients, who have some degree of partial obstruc- to medical therapy include those performed through a midline tion, the success or failure of conservative management can be incision; those involving the aorta, the colon, the rectum, the predicted with high accuracy by recording the arrival of contrast appendix, or the pelvic adnexa; and those done to relieve previous material (either a water-soluble agent or a mixed barium prepara- carcinomatous obstruction. Matted adhesions, which are more tion) in the right colon within a deﬁned time.14,30,60-63 One common in patients who have undergone midline incisions or co- prospective study documented the arrival of diatrizoate meglu- lorectal procedures, are less amenable to conservative manage- mine–diatrizoate sodium in the colon within 24 hours and found ment than a simple obstructive band is.53 In the context of this this measure to have a sensitivity of 98%, a speciﬁcity of 100%, an kind of operative history, strong consideration should be given to accuracy of 99%, a positive predictive value of 100%, and a neg- surgical intervention if the obstruction does not resolve within 24 ative predictive value of 96% as a predictor of successful nonop- hours—unless comorbid medical conditions tip the risk-beneﬁt erative treatment.64 Other studies achieved comparable results balance in the direction of nonoperative therapy. with shorter arrival times (e.g., 4 or 8 hours).14,61,65 There is an ongoing debate regarding how long patients with Several prospective, randomized clinical trials have addressed partial adhesive obstruction should be treated conservatively. the issue of whether administration of contrast material can itself After 48 hours of nonoperative management, the risk of compli- be therapeutic with respect to resolving adhesive small bowel cations increases substantially, and the probability that the obstruction. Two such studies examined small bowel follow- obstruction will resolve diminishes.43 Generally, if the obstruction through with barium, either alone or mixed with diatrizoate meg- is going to resolve with nonoperative therapy, there will be a fair- lumine.30,31 Both found that the intervals between admission and ly prompt response within the ﬁrst 8 to 12 hours. Therefore, if a operation were shorter for patients randomized to the contrast patient’s condition has deteriorated or has not signiﬁcantly arm than for those in the control group but that contrast exami- improved by 12 hours after nasogastric decompression and resus- nation did not lead to more expeditious resolution of obstruction. citation, exploratory laparotomy is advisable. During this obser- Both studies also demonstrated that barium could be adminis-
© 2004 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 Gastrointestinal Tract and Abdomen 4 Intestinal Obstruction — 14 tered to patients with small bowel obstruction safely and without the best study published to date on this issue is a retrospective, complications. matched-pair analysis that used an intention-to-treat analysis.71 In Four prospective, randomized trials have investigated the effects this study, 52% of the patients in the laparoscopic group underwent of administering water-soluble hyperosmolar contrast agents to conversion to open lysis of adhesions either for completion of adhe- patients with small bowel obstruction.60,62,63,66 In one study, admin- siolysis or for management of complications. No perforations or istration of 100 ml of diatrizoate meglumine (1,900 mOsm/L) recurrent obstructions were missed. Perforations were more com- through the nasogastric tube promoted resolution of adhesive par- mon overall in the laparoscopic group than in the open group, tial obstruction and shortened hospital stay but had no effect on though this difference was largely eliminated when patients from whether laparotomy was required.60 No contrast-related complica- the laparoscopic group who underwent conversion to open lysis tions were observed. In the second study, administration of a dif- were not considered. Patients with two or more previous laparo- ferent water-soluble hyperosmolar contrast agent, ioxitalamate tomies had a higher incidence of intraoperative complications than meglumine (1,500 mOsm/L), had no therapeutic effect on patients those with fewer laparotomies. Accordingly, the authors recom- with partial small bowel obstruction.66 Again, no contrast-related mended against laparoscopic adhesiolysis in patients with two complications were observed. In the third study, administration of or more previous laparotomies. The high conversion rate in this 100 ml of diatrizoate meglumine through the nasogastric tube sig- study notwithstanding, the laparoscopic group as a whole (includ- niﬁcantly accelerated the resolution of adhesive partial small bowel ing conversions) experienced an overall reduction in postoperative obstruction and shortened hospital stay.62 Patients in whom con- complications. trast reached the colon within 24 hours were able to tolerate imme- Another potential advantage of laparoscopic adhesiolysis is that diate oral feeding. In addition, the time needed to decide on oper- it results in fewer intra-abdominal adhesions than open laparoto- ative adhesiolysis was shorter in patients receiving the contrast my76,77 and thus may reduce the risk of recurrent bowel obstruction. agent. In the fourth study, patients whose partial adhesive small However, one study found that despite a reduction in median bowel obstruction did not resolve after 48 hours either received 100 length of stay, patients treated laparoscopically were at increased ml of diatrizoate meglumine or underwent operative adhesiolysis.63 risk for early unplanned reoperation as a consequence of either If administration of the contrast agent revealed complete bowel incomplete relief of obstruction or complications.70 In fact, bowel obstruction, operative treatment was immediately initiated. If it perforation in the course of laparoscopic adhesiolysis often is not revealed partial obstruction, conservative treatment was continued; detected during the procedure and presents in a delayed fashion.75 in 100% of these patients, the obstruction then resolved without Many such injuries are attributable either to insertion of the initial operation. No contrast-mediated complications, no bowel strangu- trocar or to delayed perforation of a thermal injury. When laparo- lation, and no deaths were reported.The signiﬁcant treatment effect scopic adhesiolysis fails to identify and relieve an obvious point of reported in three of the four randomized clinical trials, along with obstruction or when adhesiolysis is inadequate or unsafe, conver- the absence of any deleterious contrast-related complications in all sion to an open approach is indicated. four, constitutes sufﬁcient evidence to support the administration of 100 ml of diatrizoate meglumine to patients with adhesive partial Early Postoperative Obstruction small bowel obstruction. Early postoperative mechanical small bowel obstruction is not By accelerating the resolution of partial small bowel obstruc- uncommon: it occurs in approximately 10% of patients undergo- tion and ileus, administration of water-soluble contrast agents can ing abdominal procedures.78 Postoperative bowel obstruction is shorten the expected hospital stay and thereby reduce the cost of often difﬁcult to diagnose because it gives rise to many of the care. Thus, it is reasonable that the ﬁrst step in managing sus- same signs and symptoms as postoperative ileus: obstipation, dis- pected partial small bowel obstruction from adhesions or postop- tention, nausea, vomiting, abdominal pain, and altered bowel erative ileus should be to administer water-soluble contrast mate- sounds. In most cases, there are roentgenographic signs indicative rial intragastrically. When bowel function does not return within of small bowel obstruction rather than ileus; however, in some 24 hours and the obstruction is demonstrated to be partial, con- cases, abdominal x-rays fail to diagnose the obstruction.79 tinued observation is safe and resolution without operation is still Traditionally, when plain radiographs are equivocal, an upper GI highly probable. Eventually, however, there will be a point beyond barium study with follow-through views is the next test performed which continued observation is no longer cost-effective in com- to distinguish ileus from partial or complete small bowel obstruc- parison with operative adhesiolysis (especially laparoscopic adhe- tion80; however, such studies may yield the wrong diagnosis in as siolysis). Additional prospective trials are necessary to determine many as 30% of cases.26,79,81 A number of authorities believe that precisely how long the waiting period before operative treatment abdominal ultrasonography is excellent at distinguishing postop- should be. erative ileus from mechanical obstruction and recommend that it be done before any contrast study.22 Laparoscopic adhesiolysis Several clinical reports have Early postoperative obstruction is caused by adhesions in about demonstrated that laparoscopic adhesiolysis for acute small bowel 90% of patients.79,82 When there are no signs of toxicity and no obstruction is both feasible and safe.67-72 Laparoscopic or laparo- acute abdominal signs, such obstruction can usually be managed scopic-assisted lysis of adhesions relieves bowel obstruction in more safely with nasogastric decompression.78,79,81,82 As many as 87% of than 50% of patients and is associated with lower morbidity, earlier patients respond to nasogastric suction within 2 weeks. About 70% return of bowel function, quicker resumption of normal diet, and a of the patients who respond to nonoperative treatment do so with- shorter hospital stay than open operative lysis.67-71,73 To minimize in 1 week, and an additional 25% respond during the following 7 the risk for bowel injury at the beginning of the operation, the ﬁrst days. If postoperative obstruction does not resolve in the ﬁrst 2 trocar is inserted under direct vision by means of an open tech- weeks, it is unlikely to do so with continued nonoperative therapy, nique, and the incision is placed well away from any previous and reoperation is probably indicated79,82; about 25% of patients scars.74,75 whose postoperative obstruction was initially treated nonoperative- At present, there are no prospective, randomized, controlled clin- ly eventually require reoperation. An exception to this guideline ical trials comparing laparoscopic with open adhesiolysis. Perhaps arises in patients known to have severe dense adhesions (sometimes
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