Acs0502 Abdominal Mass 2006


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Acs0502 Abdominal Mass 2006

  1. 1. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 2 Abdominal Mass — 1 2 ABDOMINAL MASS Wilbur B. Bowne, M.D., and Michael E. Zenilman, M.D., F.A.C.S. Evaluation of an Abdominal Mass Clinical Evaluation Abdominal masses are commonly addressed by surgeons, as well as by members of many clinical subspecialties. In terms of clinical In general, the term abdominal mass importance, abdominal masses cover a broad spectrum: some refers to a palpable mass that lies anterior have few or no apparent consequences, others significantly impair to the paraspinous muscles in a region bor- quality of life, and still others represent severe conditions that are dered by the costal margins, the iliac crests, associated with poor outcomes and high mortalities. For each and the pubic symphysis. One method of patient, therefore, it is essential to formulate a management description divides the abdomen into nine approach that is tailored to the particular clinical situation. areas: epigastric, umbilical, suprapubic, Effective decision-making in this regard involves establishing the right hypochondriac, left hypochondriac, correct diagnosis, introducing an effective treatment plan, elimi- right lumbar, left lumbar, right inguinal, nating risks and complicating factors, initiating preventive mea- and left inguinal.3 Our preferred method sures, and determining the prognosis. divides the abdominal cavity into four quadrants—right upper, The history of the abdominal mass in the medical literature is right lower, left upper, and left lower—and makes specific refer- ancient, dating back to the Egyptians.The varied differential diag- ence to the epigastrium and the hypogastrium as necessary. This nosis of such masses was discussed in the Papyrus Ebers (ca. 1500 method of description also includes masses discovered within the B.C.).1 Egyptian medical scholars kept detailed notes chronicling retroperitoneum and the abdominal wall. For practical purposes, conditions encountered and describing methods of abdominal the abdominal wall begins from the diaphragm superiorly and examination that were based on studies of basic anatomy and continues inferiorly to the pelvic cavity through the pelvic inlet. embalming practices. Centuries later, in his Book of Prognostics, the The anterior, posterior, and lateral boundaries of the abdominal Greek physician Hippocrates (ca. 400 B.C.) discussed the prog- wall should be familiar to surgeons. Further anatomic detail is nostic significance of various types of abdominal masses: available in other sources.4,5 A sound understanding of the normal anatomy in each The state of the hypochondrium is best when it is free from pain, soft, and of abdominal quadrant is essential for the evaluation of the abdom- equal size on the right side and the left. But if inflamed, or painful, or distend- inal mass. Particular abnormalities tend to be associated with ed; or when the right and left sides are of disproportionate sizes; all of these particular regions or quadrants of the abdomen, and these asso- appearances are to be dreaded. A swelling in the hypochondrium, that is hard ciations should be considered first in the differential diagnosis. and painful, is very bad…. Such swellings at the commencement of disease prognosticate speedy death. Such swellings as are soft, free from pain, and Commonly, an abnormal enlargement or mass in the abdomen yield to the finger, occasion more protracted crises, and are less dangerous comes to the clinician’s attention in one of three ways: it is than others.2 detected and reported by the patient, it is discovered by the clin- ician on physical examination, or it is noticed as an unrelated Along with the basic methods of clinical evaluation known since incidental finding on a radiographic study. Subsequent clinical antiquity, the modern surgeon has an armamentarium of sophis- decision making is then influenced by whether the lesion is intra- ticated diagnostic studies that aid in the detection, diagnosis, and abdominal, pelvic, retroperitoneal, or situated within the abdom- appropriate treatment of abdominal masses. inal wall. In certain cases, a prompt diagnosis can be made after In this chapter, we begin with essential definitions and anatom- the physical examination, with no further investigation required; ic considerations and then outline our fundamental approach to obesity, ascites, pregnancy, hernias, infection or abscess, cysts, evaluating patients with an abdominal mass, which integrates the and lipomas are examples of conditions that can generally be clinical history, the physical examination, and various investigative diagnosed at this point. studies. In particular, we address current developments in inves- Of the various factors that go into making the diagnosis and tigative techniques, including radiographic and molecular imaging implementing therapy, clinical experience is undoubtedly para- studies that facilitate anatomic evaluation, diagnosis, and determi- mount. Nevertheless, even the most experienced physicians are nation of the biologic significance of the abdominal mass; we also subject to some degree of clinical inaccuracy. A randomized study address minimally invasive diagnostic interventions. Throughout, from 1981 found that even when experienced clinicians were cer- we emphasize an algorithmic, evidence-based approach to detec- tain about the presence of a mass, there was still an appreciable tion and evaluation of abdominal masses. Specific perioperative (22%) chance that further investigation would not reveal any and operative strategies for addressing particular diagnoses are abnormality.6 The evaluation of abdominal masses continues to outlined in other chapters. pose many clinical challenges for the surgeon.There is no magical
  2. 2. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 2 Abdominal Mass — 2 Evaluation of an Abdominal Mass Patient presents with abdominal mass Obtain complete history. Generate differential diagnosis. Perform thorough physical examination. Patient has generalized abdominal Patient has discrete mass swelling Consider common causes of generalized abdominal enlargement or swelling: Fat, F luid, F latus, F etus, Feces, and F atal growths. Working or presumed diagnosis Diagnosis is unknown is generated Initiate investigative studies: Once diagnosis is established, • Laboratory tests (e.g., chemistry manage as appropriate. profile, CBC with differential, urinalysis, occult blood, tumor markers, LDH). • Imaging (e.g., plain film, US, CT, MRI, PET, PET/CT). Diagnosis remains unknown Diagnosis is established Perform image-guided Manage as appropriate. percutaneous biopsy (US, EUS, CT, MRI). Diagnosis remains unknown Diagnosis is established Perform diagnostic laparoscopy Manage as appropriate. and biopsy, supplemented by laparoscopic US or peritoneal cytology if indicated. If diagnosis is still unclear, consider exploratory laparotomy. Once diagnosis is established, manage as appropriate.
  3. 3. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 2 Abdominal Mass — 3 DIFFERENTIAL DIAGNOSIS formula for mastering the necessary diagnostic skills; the closest thing to such a formula is an approach that combines knowledge For practical purposes, the differential diagnosis for an abdom- and application of fundamental anatomic principles with continu- inal mass is divided into categories corresponding to the anatom- ous development and appropriate utilization of new diagnostic ic divisions of the abdomen (i.e., the four quadrants, the epigastri- modalities. For accurate assessment of the origin and character of um, and the hypogastrium) [see Figure 1]. The challenge for the the abdominal mass, it is essential to possess a thorough under- modern surgeon is how to narrow down the diagnostic possibili- standing of the normal anatomy, the anatomic variations that may ties while avoiding needlessly extensive and expensive evaluations. be observed, and the distortions that may be caused by the vari- To accomplish this goal with efficiency, the surgeon must draw ous potential disease processes. As has been said of many profes- both on his or her own reservoir of fundamental knowledge and sions besides surgery, “You must know the territory.” Ultimately, on the available patient data (e.g., age, gender, associated symp- whether a correct diagnosis calls for further intervention or for toms, and comorbidities). referral to colleagues with complementary technical expertise After obtaining a thorough clinical history, the surgeon should depends on the experience of the practitioner. be able to generate a differential diagnosis.The physical examina- Fundamental to the successful diagnosis of any abdominal mass tion may then help confirm or rule out diagnostic possibilities. For are a detailed medical and surgical history and a meticulous phys- example, the presence or absence of pain or tenderness may dis- ical examination (see below). tinguish an inflammatory or nonneoplastic process from a neo- plastic one (e.g., cholecystitis from Courvoisier gallbladder or, per- HISTORY haps, diverticulitis from carcinoma of the colon). Likewise, the Establishing a solid surgeon-patient relationship is vital for acuteness of the condition may help eliminate diagnostic possibil- building patient trust and confidence, particularly during a period ities, as when an incarcerated abdominal wall hernia is distin- of great uncertainty and vulnerability in the patient’s life. guished from a lipomatous mass. So too may the nature of the Accordingly, our philosophy in dealing with an abdominal mass is process, as when a pulsatile mass such as an aneurysm is distin- to evaluate the patient first and then consider radiographic and guished from a nonpulsatile one such as a hematoma or a cyst. laboratory studies if the initial assessment does not yield a diagno- Masses of the abdominal wall commonly are subcutaneous sis. A careful and methodical clinical history should be taken that lipomas, and care should be taken to differentiate them from neo- includes all factors pertaining to the lesion. Information about the plastic lesions such as desmoid tumors,13 dermatofibrosarcoma lesion’s mode of onset, duration, character, chronology, and loca- protuberans (DFSP),14 and other related15 or nonrelated tion should be obtained, as well as confirmation of the presence or tumors.16,17 When an abdominal mass is associated with uncom- absence of associated symptoms. mon or unexpected findings, the surgeon must be alert to the pos- Interviewing strategies for collecting clinical data may vary from sibility of an uncommon or unexpected disease process.18,19 It surgeon to surgeon.7 For example, some prefer to conduct a clin- remains true, however, that knowledge of the most common dis- ical history while sitting rather than standing because this posture ease processes associated with region-specific abdominal masses, tends to suggest the absence of undue haste and the presence of combined with familiarity with the characteristic signs and symp- appropriate concern and empathy. A focused, comprehensive toms, is the foundation of the clinical assessment of such masses. interview usually provides all the information necessary for mak- PHYSICAL EXAMINATION ing the correct diagnosis. Our practice is to start by asking nondi- rective questions—for example, “When did you first notice the The physical examination plays an essential role in the evalua- mass on your left side?” or “How long did you experience this pain tion and workup of an abdominal mass. Current investigative in your abdomen?” It is important to allow patients to describe the studies are also important in this setting, but all too often, clini- history in their own words. It is also important to avoid questions cians become overly reliant on various imaging modalities, some- with a built-in degree of bias—for example, “Didn’t you know the times overlooking the importance of a careful and thorough exam- mass was on your left side?” or “The pain must have been there ination. Such overreliance can increase the chances of missing for some time?” Such questions can lead to biased answers that subtle physical findings—such as an enlarged lymph node, subcu- may misrepresent the chronology or the true natural history of the taneous irregularity, or referred pain—that could have a significant disease. In most cases, we then proceed to ask questions designed effect on the management of the abdominal mass. Our practice in to elicit more specific information (e.g., previous operations, pre- examining patients with an abdominal mass is to follow an orga- vious medical conditions or therapies, family medical history, or nized, systematic approach consisting of inspection, auscultation, recent travel). It is sometimes necessary to fill in the details by ask- percussion, and palpation, in that order. More detailed discussions ing direct questions about particular points not already mentioned of these specific maneuvers are available elsewhere.20 by the patient. For example, an inquiry regarding gastrointestinal The physical examination has three main objectives. First, the symptoms associated with the abdominal mass may be either non- examiner must evaluate the patient’s condition as it directly or specific (e.g., concerned with nausea, vomiting, diarrhea, or con- indirectly relates to the mass (e.g., by noting associated systemic stipation) or specific (e.g., concerned with jaundice, melena, illness, pain, malaise, or cachexia). Second, the examiner must hematochezia, hematemesis, hematuria, or changes in stool cal- assess the acuteness of the patient’s condition (e.g., by determin- iber). Non-GI symptoms (including urologic, gynecologic or ing whether a left upper quadrant mass is likely to be a ruptured obstetric, vascular, and endocrinologic symptoms) should not be spleen or simply a long-standing mass in the abdominal wall), overlooked. A history of surgery, trauma, or neoadjuvant or adju- which will dictate whether the next step is immediate treatment or vant cancer therapy may be diagnostically important.8 For further evaluation. Third, the examiner must carefully examine instance, the presence of an abdominal mass representing recur- each abdominal quadrant, assessing both normal and abnormal rent cancer raises important clinical questions concerning the anatomic relations as possible sources of the presumed mass. advisability of additional therapy or palliative measures, which How to distinguish a normal abdominal mass or swelling from may carry significant morbidity and mortality.9-12 an abnormal one remains a common challenge for the surgeon.
  4. 4. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 2 Abdominal Mass — 4 EPIGASTRIUM Omental Hernia Pancreatic Tumor RIGHT UPPER QUADRANT Pancreatic Cyst Tender Gastric Carcinoma Liver in Hepatitis Gastrointestinal Stromal Tumor (GIST) Congestive Heart Failure Pyloric Stenosis Gallbladder in Cholecystitis Aortic Aneurysm Subphrenic Abscess Retroperitoneal Sarcoma Perinephric Abscess Hepatomegaly Colonic Tumor Abdominal Wall Hematoma LEFT UPPER QUADRANT Nontender Splenomegaly Hepatomegaly Abdominal Wall Hematoma Renal Tumor Pancreatic Tumor Adrenal Tumor Pancreatic Cyst Courvoisier’s Gallbladder Gastric Tumor Hydrops of Gallbladder Colonic Tumor Fecal Impaction Renal Tumor or Enlargement Fecal Impaction RIGHT LOWER QUADRANT Tender LEFT LOWER QUADRANT Appendiceal Abscess Sigmoid Diverticulitis Psoas Abscess Carcinoma of Colon Pyosalpinx Ovarian Tumor Regional Ileitis Pyosalpinx Intussusception Nontender HYPOGASTRIUM Carcinoma of Colon Bladder Ovarian Tumor Gravid Uterus Uterine Fibroids Regional Ileitis Urachal Cyst Figure 1 Schema represents differential diagnosis of an abdominal mass by quadrant or region. Fundamental knowledge of normal anatomy and clinical presentations is the basis for distinguishing the various disease processes. Abdominal wall hernia is considered a possibility in every region or quadrant. Physical findings on examination are sometimes variable and can Palpable or discrete masses should always be localized with be affected by factors such as obesity, body habitus, associated respect to the previously described landmarks (see above), and medical conditions, and the patient’s ability to cooperate. For they should, if possible, be described in terms of size, shape, con- example, the normal aorta is often palpable within the epigastrium sistency, contour, presence or absence of tenderness, pulsatility, and may be slightly tender; in elderly, asthenic patients, the nor- and fixation. Knowledge of the location of the mass in the mal aorta may be mistaken for an aneurysm. Likewise, the cecum abdomen shortens the list of structures or organs to be considered and the descending colon, both of which are usually palpable in and may give insight into the nature and extent of the pathologic thin patients (especially when they contain feces), sometimes mas- process. Frequently, however, the mass’s location can only be querade as a cancerous mass; subsequent disimpaction causes vaguely outlined, particularly when fluid is present, when the such “masses” to resolve. Obesity may preclude evaluation of a abdomen is tender or tense, or when the patient is obese. Gastric potential abdominal mass: it can be difficult to identify discrete neoplasms, pancreatic neoplasms, colonic neoplasms, sarcomas, palpable masses amid the often remarkable adiposity present with- pancreatic cysts, and distended gallbladders may be palpable, typ- in the abdominal wall and the surrounding structures. Ascites may ically at advanced stages of disease. Recognition of such masses also obscure abdominal masses, making examination more prob- can be facilitated by repeating the abdominal examination after lematic. Transient gaseous distention or intestinal bloating occa- analgesics have been administered or after the patient has been sionally presents a similar problem, but it usually resolves sponta- anesthetized in preparation for a procedure. neously, except in cases of intestinal obstruction. Either gastric dilatation or intestinal obstruction may lead to abdominal disten- tion that is severe enough to necessitate nasogastric decompres- Working or Presumed Diagnosis sion. Not uncommonly, in women of childbearing age, a lower Once a thorough clinical history has abdominal mass may represent a gravid uterus. In such cases, a been obtained and a careful physical exam- gynecologic examination must be conducted and a pregnancy test ination conducted, it is usually possible to performed before further studies are ordered. The multiplicity of generate a working diagnosis. Once the potential benign causes notwithstanding, the possibility of a neo- working diagnosis has been established, plasm (single or multiple) clearly remains a matter of considerable subsequent management is considered in concern in the evaluation of any patient with abdominal disten- light of its appropriateness for the presumed tion. A convenient method of recalling the main causes of gener- condition. Sometimes, however, the diag- alized enlargement or distention of the abdomen is to use the so- nosis remains unknown even after a com- called “six Fs” mnemonic device: Fat, Fluid, Flatus, Fetus, Feces, prehensive clinical history and physical examination; in such cases, and Fatal growths.21-23 further studies are required. A wide range of laboratory and imag-
  5. 5. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 2 Abdominal Mass — 5 ing studies are now available for establishing the diagnosis. If these improved and refined for use in evaluating abdominal masses. studies do not resolve the diagnostic uncertainty, additional pro- In particular, advances in cross-sectional imaging techniques, cedures, including image-guided percutaneous biopsy, diagnostic such as ultrasonography (US), computed tomography, magnet- laparoscopy, and exploratory laparotomy, may be employed as ic resonance imaging, and positron emission tomography necessary. (PET), have made it possible to assess these lesions more pre- cisely. Consequently, whenever the surgeon is confronted with the scenario of a clinically suspected or palpable abdominal Investigative Studies mass, accurate diagnostic imaging is of paramount importance. Surgeons are in a unique position to The appropriate use of different imaging modalities in the eval- care for patients presenting with an uation of the palpable abdominal mass is well described by the abdominal mass and should guide the American College of Radiology guidelines,25,26 which are up- collaborative management effort and the dated every 6 years. choice of appropriate investigative stud- The use of noninvasive US and CT as first-line procedures for ies. It is therefore essential that surgeons the evaluation of palpable masses has received considerable clini- be familiar with every available method cal attention.6,27-30 Investigators have found both US and CT to for efficient and cost-effective diagnosis of be excellent for affirming or excluding a clinically suspected an abdominal mass. For any given situa- abdominal mass, with sensitivity and specificity values exceeding tion, the selection of investigative studies should be based on 95%.This finding is particularly noteworthy because in only 16% the preferences of the patient, the knowledge and judgment of to 38% of patients referred for a suspected abdominal mass will the surgeon, and the capabilities of the institution. In this way, the diagnosis be corroborated by an imaging study.31 Both US and surgeons who practice outside large, specialized referral cen- CT are also capable of visualizing the organ from which the mass ters will still be able to provide integral leadership for most dis- arises: US successfully determines the organ of origin approxi- ease management efforts arising from the diagnosis of an mately 88% to 91% of the time, and CT does so approximately abdominal mass. 93% of the time. Prediction of the pathologic diagnosis of an abdominal mass, however, remains a challenge for both modali- LABORATORY STUDIES ties. US correctly predicts the pathologic diagnosis in 77% to 81% The diagnostic workup of an abdominal mass usually includes of cases, whereas CT suggests the diagnosis in 88% of cases. laboratory evaluation. If the cause of the mass remains unknown, Further advancements in cross-sectional imaging (e.g., multide- preliminary laboratory analysis should include a chemistry profile tector CT [MDCT] with three-dimensional reconstruction and (electrolyte, blood urea nitrogen [BUN], and creatinine concen- magnetic resonance angiography [MRA]) and the addition of trations, as well as liver function tests), a complete blood count molecular and functional imaging modalities (e.g., PET) will (CBC) with differential, and urinalysis. An abnormal laboratory undoubtedly improve the predictive abilities of CT and US. At value sometimes plays an important role in establishing the iden- any rate, the current state of imaging technology affords clinicians tity or pathogenesis of an abdominal mass. For example, an ele- the ability to distinguish benign from malignant processes, to vated alkaline phosphatase or liver transaminase level may suggest assess tumor biology, and to detect lesions that impose a minimal metastasis to the liver. Likewise, an elevated serum amylase con- disease burden. As a consequence, clinicians are more likely to centration may be suggestive of a pancreatic pseudocyst rather detect clinically occult disease or discover it incidentally. than a cystic neoplasm or an adenocarcinoma; however, an elevat- Employing an integrative assessment approach (which includes ed total serum bilirubin level (i.e., > 10 mg/dl) may be more sug- clinical history, physical examination, and investigative studies) gestive of a malignant process secondary to adenocarcinoma of should lead to more targeted, efficient, and cost-effective strategies the pancreatic head or cholangiocarcinoma. Routine testing for for evaluating abdominal masses. For example, the surgeon can occult blood in the stool should not be overlooked. Tumor mark- correlate the clinical location of the abdominal mass with perti- ers (e.g., carcinoembryonic antigen [CEA], the cancer antigens nent findings from the history and laboratory studies to determine CA 19-9 and CA 125, and α-fetoprotein [AFP]) may also help which imaging modality is the most expeditious and cost-effective differentiate between benign disease processes and malignant for a given circumstance. Each imaging modality has unique ones, distinguish high-level disease from low-level disease, and, in strengths and weaknesses. some cases, establish a disease diagnosis (e.g., elevated AFP levels in patients with hepatocellular carcinoma). Similarly, an elevated Plain Abdominal Radiographs serum lactate dehydrogenase (LDH) level may prove invaluable in By definition, a plain film is a radiograph made without the use the staging and prognosis of certain diseases (e.g., melanoma) of an artificially introduced contrast substance.32 Commonly connected with an abdominal mass.24 Furthermore, the ability to employed for initial surveillance of the abdomen, the plain film distinguish between functional abdominal masses and nonfunc- still has an important place within the investigative armamentari- tional ones (e.g., adrenal tumors) also has important implications um. Otherwise known as a KUB (kidney-ureter-bladder) study, for evaluation and management. this low-cost technique may reveal nonspecific or indirect evi- In some cases, when the type of mass remains unknown, need- dence of an abdominal mass, such as variations in the size and less and expensive laboratory analysis can and should be avoided density of an organ or displacement of normal structures or fat if it appears that other studies may prove more beneficial. planes. Furthermore, the radiolucency of air within the bowel may also prove helpful for recognizing worrisome displacement of vis- IMAGING cera as a result of a large abdominal mass. Occasionally, a simple Diagnostic radiology is a dynamic specialty that has under- plain radiograph can assist the surgeon in making a specific diag- gone rapid change in conjunction with the ongoing evolution of nosis, such as calcified aortic aneurysm, acute gastric distention, imaging technology. Not only has the number of imaging fecal impaction, porcelain gallbladder, and certain malignancies modalities increased, but each modality continues to be [see Figure 2].
  6. 6. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 2 Abdominal Mass — 6 Novel approaches (e.g., CT virtual colonoscopy), in conjunction with advances in cross-sectional imaging, may eventually render conventional GI imaging unnecessary. Ultrasonography Compared with other modalities, US has several advantages in the evaluation of suspected abdominal masses, including wide- spread availability, speed of use, the absence of ionizing radiation, low cost, and the ability to document the size, consistency (solid or cystic), and origin of a mass with real-time images.27,33 When directed at solving a specific clinical problem, US generally pro- vides more diagnostic information. Moreover, the necessary equipment can easily be transported to the patient’s bedside or another clinical setting; thus, no patient preparation is required, and only minimal patient cooperation is needed. We consider US indispensable in the assessment of abdominal masses. At the same time, we acknowledge that one disadvantage of US is the extent to which the quality of the results depends on the technical proficiency and diligence of the operator or techni- cian (though this disadvantage can actually become an advantage when personnel are well trained and experienced). In the hands of an inexperienced operator, US may yield inconclusive or untrust- worthy results that contribute to delayed diagnosis or even misdi- agnosis. In an effort to help minimize this problem, we encourage the surgeons at our institution (who are trained in US) to perform their own studies in the clinic and the operating room. This approach further expedites recognition of disease [see Figure 3], positively influences management, and facilitates operative deci- sion making regarding abdominal masses [see Figure 4]. Another disadvantage of US is its inability to visualize the entire abdominal cavity as a consequence of the acoustic barriers present- ed by gas-containing structures (e.g., the bowel) and the absorptive interfaces (acoustic shadowing) provided by soft tissue and bone. Figure 2 Plain abdominal radiograph shows a 10 cm functional For optimal visualization of abdominal masses, US should be per- left adrenocortical carcinoma. Calcifications creating a rim formed through “acoustic windows” that allow adequate transmis- enhancement are easily identified. The diagnosis was confirmed sion of sound. Accordingly, US is most effective as a tool for evalu- by means of laboratory analysis and abdominal CT. ating masses in those regions of the abdomen where an acoustic window exists (e.g., the right and left upper quadrants and the Conventional Gastrointestinal Imaging As a consequence of the technical advances in cross-sectional imaging and endoscopy, conventional GI contrast studies are now largely relegated to more adjunctive roles in the evaluation of abdominal masses. In the upper and middle portions of the abdomen, we occasionally use upper GI studies, small bowel fol- low-through (SBFT), or enteroclysis to evaluate inflammatory masses (e.g., lesions arising from Crohn disease), masses that are inaccessible to endoscopy, or unusual masses with uncertain diag- noses. For such lesions, we employ single- or double-contrast bar- ium protocols to ensure that significant pathology is not missed; however, these studies are notoriously insensitive and do not pro- vide an opportunity for tissue diagnosis. In the lower portion of the abdomen, barium studies still play a significant role in the evalua- tion of masses whose history includes GI symptoms (e.g., anemia and weight loss) suggestive of a colonic neoplasm, as well as for evaluating inflammatory masses arising from diverticular disease. In certain cases, we employ a single-contrast barium enema for masses that are causing near-complete obstruction; this study is also helpful for assessing the remaining large bowel for synchro- nous disease. For small lesions (masses < 1 cm), we typically favor Figure 3 Sagittal ultrasonogram of the pancreas demonstrates a a double-contrast barium enema. large mass in the pancreatic head of a 71-year-old patient Currently, in the evaluation of an abdominal mass, barium referred for “gallstones” after experiencing a 10 lb weight loss. studies are used mainly to complement colonoscopy and CT. The mass lies anterior to the inferior vena cava.
  7. 7. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 2 Abdominal Mass — 7 a b Figure 4 (a) Transverse ultrasonogram of the liver of a 72-year-old cirrhotic patient with a hepatitis C infection shows a 4.0 × 3.5 cm hepatoma, nestled between the right and middle hepatic veins and closely apposed to the inferior vena cava. (b) Color Doppler ultrasonogram from the same patient displays blood flow in the middle hepatic vein and the surrounding liver parenchyma. Blood flow toward the transducer is usually displayed in shades of red, whereas blood flow away from the transducer is displayed in shades of blue. Color Doppler ultrasonography allows evaluation of the patency and flow characteristics of the hepatic circulation as it relates to the mass. pelvis). Fortunately, the shortcomings of US can be compensated and delineating the relations between the abdominal mass and for by employing other cross-sectional imaging modalities. adjacent structures [see Figure 5]. Such data are essential for guid- ing diagnostic procedures, determining whether operative manage- Computed Tomography ment is indicated, and selecting the optimal operative approach. At present, helical (spiral) CT is the most efficient and cost- Although modalities such as MRI, PET, and endoscopic ultra- effective imaging modality for the evaluation of abdominal mass- sonography (EUS) have advantages over CT in one area or anoth- es.6,27,34,35 Unlike US, CT provides cross-sectional images with er, CT continues to be superior overall for assessing abdominal mass- excellent spatial resolution and exquisite density discrimination that es and remains our preferred imaging method for this purpose. are unaffected by bowel gas, bone, or excessive abdominal fat. CT The use of contrast during the acquisition of CT scans is vital. routinely visualizes the abdominal wall, the viscera, the mesentery, Opacification of the bowel enables the examiner to distinguish the and the retroperitoneum, clearly defining important tissue planes abdominal mass from surrounding viscera or other adjacent struc- tures. Contrast-enhanced scans also allow delineation of the rele- vant vascular anatomy; in fact, CT angiography has now relegat- ed conventional angiography to a minimal role in the evaluation of certain abdominal masses.36,37 Triple-phase or multiphase scan- ning that includes noncontrast images is now recommended. Such scans achieve optimal definition and characterization of liver and pancreatic masses. This achievement is of significant clinical value: state-of-the-art CT imaging of malignant pancreatic mass- es, as well as of other malignancies, has the potential to improve outcome not only by correctly detecting the mass but also by accurately assessing the extent of disease, thereby helping deter- mine which patients may benefit from surgical management or neoadjuvant therapy [see Figure 6]. The advent of MDCT technology offers the possibility of even better imaging of abdominal masses than standard contrast CT provides. MDCT scanners can image specific organs or masses with 1 mm slices in less than 20 seconds, and the resultant data can be displayed not only as an axial image but also in a three-dimen- sional representation that includes detailed vascular mapping.35 Studies suggest that MDCT may be the most useful modality for preoperative assessment of the resectability of pancreatic and other Figure 5 CT scan of a 65-year-old man with a large retroperi- abdominal masses.36 MDCT has a sensitivity of 90% and a speci- toneal leiyomyosarcoma clearly demonstrates close association of ficity of 99%, respectively, and it is not observer dependent. this mass with the right hemiliver, as well as displacement of the Currently, although MRI (see below) offers unique tissue con- inferior vena cava. trast and inherent multiplanar capabilities for imaging abdominal
  8. 8. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 2 Abdominal Mass — 8 is a better choice than CT for evaluating an abdominal mass. An example is a case in which the use of iodinated contrast material is contraindicated. The extracellular gadolinium chelates used in MRI are very safe and can be given to patients with mild to mod- erate azotemia without causing renal impairment. MRI has unique characteristics that can be effectively employed to distin- guish normal from pathologic tissue in a patient with an abdomi- nal mass.38 Detailed information about the principles and practices of abdominal MRI is beyond the scope of this chapter and is read- ily available elsewhere.39 A brief technical summary may, how- ever, be worthwhile. The abdomen and its contents are subject- ed to a momentary radiofrequency pulse, then allowed to return to a state of equilibrium. During the return to equilibrium, the nuclei within each specific tissue will emit specific radiofrequen- cy signals. The strength and type of the emitted signal deter- mine the image intensity. The way in which the different tissues are visually rendered depends on (1) the longitudinal relaxation time (T1) and the transverse relaxation time (T2) of the nuclei in the tissues and (2) the method of image weighting employed. Figure 6 CT angiography performed to evaluate vascular inva- By convention, tissues with short T1 values (such as solid struc- sion in a 58-year-old patient with a pancreatic mass demon- tures) appear bright on T1-weighted images, whereas structures strates nearly complete encasement of the superior mesenteric vein. The superior mesenteric artery is not involved with the with long T2 values (e.g., fluid-containing tissues) appear bright mass. on T2-weighted images. The tissue contrast and multiplanar capabilities of MRI allow surgeons and radiologists to distin- guish not only obvious but also subtle differences between masses, CT has several advantages—high resolution, short scan abdominal masses and normal anatomy. For example, T1- times, and fast patient throughput—that make it a more widely weighted images may be valuable for detecting abdominal mass- preferred imaging modality for this purpose. es that contain fluid (e.g., cystic masses or masses containing necrotic tissue), whereas T2-weighted images may be useful for Magnetic Resonance Imaging characterizing these masses as either benign or malignant [see Since its introduction in the mid-1980s, MRI has become one Figure 7]. Similarly, magnetic resonance cholangiopancreatog- of radiology’s great success stories (though, because it still is not as raphy (MRCP) uses T2-weighted images to distinguish masses widely available as US or CT, its cost-effectiveness has yet to be with different signal intensities in the pancreas, the liver, and the determined). Few would dispute the enormous impact MRI has biliary tract.40 had on our ability to diagnose pathologic conditions of the brain, Positron Emission Tomography the spine, and the musculoskeletal system.Whereas MRI has clear advantages over CT in these areas of the body, this is not the case In 1930, Warburg reported that cancer cells show higher rates in the abdomen. Nevertheless, there are situations in which MRI of glycolysis than normal cells do.41 This discovery has stood the a b Figure 7 (a) Gadolinium-enhanced, T1-weighted MRI shows a large mass that appears dark and well-cir- cumscribed in comparison with the normal-appearing enhanced liver and spleen. This abnormal mass clearly contains some fluid. The fluid-filled stomach also appears dark. (b) T2-weighted MRI of the same patient details subtle inhomogeneities characteristic of a malignant mass (less organized appearance with an enhanced necrotic component). Subsequent biopsy showed this mass to be a poorly differentiated adeno- carcinoma from recurrent colon cancer.
  9. 9. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 2 Abdominal Mass — 9 BIOPSY In many cases, the pathologist is the sur- geon’s greatest teacher. Despite the sur- geon’s most strenuous efforts, the biology of the disease or lesion will inevitably dic- tate the outcome. Nowhere is this state- ment more true than in the evaluation of the abdominal mass, and its truth becomes increasingly evident as ongoing refine- ments in molecular diagnosis permit ever more sophisticated discrimination among different tumor types and their respective behaviors.44 Aside from the treatment of lymphoma, in which the surgeon is frequently called on to pro- vide technical assistance in obtaining tissue for diagnosis, the decision whether to perform a biopsy (as well as when and how to do so) rests on the surgeon’s understanding of the probable disease. For example, surgeons who treat pancreatic cancer usu- ally proceed to surgery without biopsy if the evidence for malig- nancy is strong. In other cases, biopsy is performed to confirm what is already suspected on the basis of clinical and radiograph- ic findings. Moreover, establishing the type of tumor or mass present has important implications for the use of neoadjuvant or adjuvant therapy, as well as for the planning of the surgical approach. We view the biopsy of an abdominal mass as the first stage of surgery. This procedure, though seemingly innocuous, has the potential to contaminate tissue planes and must there- fore be performed carefully. Accordingly, in order to make the appropriate choice when confronted with an abdominal mass, the surgeon must possess a thorough understanding of the vari- ous methods of obtaining an accurate and safe biopsy. Factors Figure 8 18FDG PET scan demonstrates a large metaboli- related to the size and location of the abdominal mass, as well as cally active non-Hodgkin lymphoma giving rise to an abdominal mass. factors related to institutional preference and experience, may influence the choice of biopsy technique. Image-Guided Percutaneous Biopsy test of time and now serves as the theoretical rationale for the use The value of image-guided percutaneous biopsy in the evalu- of 18F-fluorodeoxyglucose (18FDG) PET imaging to assess ation of the abdominal mass is well established.45,46 In practice, abdominal masses caused by cancer. Briefly, 18FDG is a glucose the procedure begins with identification of the mass by means of analogue that crosses the cell membrane by sharing the glucose a cross-sectional imaging modality such as US, CT, or MRI. transporter molecules used by glucose. Like glucose, it undergoes Often, three-dimensional imaging reconstructions are generated phosphorylation by the enzyme hexokinase. The resulting mole- to detail the relations of the abdominal mass to the surrounding cule, 18FDG-6-phosphate, is polar and is unable to cross cell anatomy. Once the mass is identified, decisions are made regard- membranes or serve as a substrate for metabolism. The net effect ing the safest approach and the most appropriate technique.The is that 18FDG both accumulates in and is retained by cancer cells. biopsy needle is then inserted percutaneously under the guid- The molecular information obtained from PET, as measured by ance of US, CT, or MRI.The choice among the different modal- standard uptake values (SUV), allows identification of hypermeta- ities depends on several factors, including the size and location bolic (18FDG-avid) abdominal masses (typically arising from lym- of the mass, the surgeon’s judgment regarding which method is phomas, melanomas, or certain GI malignancies [see Figure 8]).42 best in the circumstances, and the availability of the various PET may also prove to be an important surrogate modality for dis- modalities at a particular institution. The most important con- tinguishing malignant abdominal masses from benign ones.43 sideration, however, is the personal preference and experience of When PET is used alone, it has the disadvantage of being unable the radiologist performing the biopsy.We favor either US or CT, to provide sufficient anatomic information to guide biopsy or fur- both of which yield good results. ther therapy.When PET is used with CT in PET/CT fusion imag- In general, we prefer US-guided biopsy for large, superficial, ing, however, the functional advantages of PET and the structural and cystic masses. This technique is also appropriate for lesions advantages of CT combine to enhance the detection rate for lying at moderate depths in thin to average-size persons. In some abdominal masses.42 If a mass is anatomically evident but metabol- cases, US can be employed to guide biopsy of small, deep, and ically inactive, it will be detected by CT. If it shows increased gly- solid abdominal masses; however, US-guided biopsy of these colysis but few or no CT abnormalities, it will be detected by PET. deep-seated masses (as well as of masses in obese patients) often The apparent advantages of PET/CT notwithstanding, prospec- proves difficult because of inadequate visualization resulting from tive, randomized validation is necessary before the widespread sound attenuation in the soft tissues. Similarly, lesions located application of this approach to the evaluation of abdominal mass- within or behind bone or gas-filled bowel cannot be easily visual- es can be justified. At present, the use of PET/CT is mostly restrict- ized (a consequence of the nearly complete reflection of sound ed to large tertiary referral centers. from bone or air interfaces).
  10. 10. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 2 Abdominal Mass — 10 laceration or of damage from tearing. Such needles are often used to confirm tumor recurrence or metastasis in patients with a pathologically confirmed primary malignancy. Large-caliber nee- dles are typically used to obtain greater amounts of material for histologic or cytologic analysis.49 In practice, the choice of a biop- sy needle is often influenced by whether the suspected pathology is benign or malignant. For example, large-caliber needles may be necessary to obtain a sufficiently large histologic specimen when certain types of malignancies (e.g., lymphoma) are suspected. When an inflammatory mass is suspected and material is needed for culture, however, a small-caliber needle may be preferred. Additional considerations for image-guided biopsy include the accuracy, safety, and potential complications of the proposed tech- nique. These considerations are essential for an evidence-based approach to diagnosis of an abdominal mass. The reported accuracy of US-guided biopsy ranges from 66% to 97%. The location, size, and histologic origin of the abdominal mass appear to influence the diagnostic accuracy of the proce- dure.47 In a series that included 126 consecutive small (< 3 cm) solid masses distributed among various anatomic locations and histologic types, US-guided biopsies showed an overall accuracy of Figure 9 In a percutaneous biopsy of a large abdominal mass, CT guidance is a reliable means of determining the direction and 91%.47 Biopsy results improved as the size of the mass increased: depth of the needle. accuracy rose from 79% in masses 1 cm or less in diameter to 98% in masses 2 to 3 cm in diameter.The accuracy of US-guided biop- sy in the liver, where most of the biopsies were performed, exceed- US possesses several strengths as a guidance modality for percu- ed 96%. Another study found US-guided biopsy to be 91% accu- taneous biopsy. It is readily available, inexpensive, and portable, and rate for abdominal masses less than 2.5 cm in diameter.50 Two it provides guidance in multiple transverse, longitudinal, or oblique organ-specific reviews concluded that US-guided biopsy of hepat- planes. Moreover, it offers real-time visualization of the needle tip as ic masses had an accuracy of 94%51 and that US-guided biopsy of it passes through tissue planes into the target area,47 thereby allow- pancreatic masses had an accuracy of 95%.52 ing the surgeon to place the needle precisely and to avoid important The reported accuracy of CT-guided biopsy ranges from 80% intervening structures. In addition, color flow Doppler imaging can to 100%. As with US-guided biopsy, the size, location, and histo- help prevent complications of needle placement by identifying the logic origin of the mass influence the results.53-55 In a study of 200 blood vessels involved with the mass, as well as any vessels lying consecutive CT-guided needle biopsies, the overall accuracy for all within the needle path. Because of its real-time capabilities, US sites biopsied was 95%.The reported organ-specific accuracy was guidance has the potential to allow quicker, more accurate, and less as follows: kidneys, 100%; liver, 99%; retroperitoneum, 87.5%; expensive biopsies than CT guidance does.48 In theory, any mass and pancreas, 82%.56 In a prospective study of 1,000 consecutive that is well visualized with US should be amenable to US-guided CT-guided biopsies, the reported sensitivity was 91.8% and the biopsy. In practice, however, this modality remains best suited for specificity 98.9%.55 At our institution, as well as others, CT-guid- superficial to moderately deep abdominal masses and for patients ed biopsy is now considered a reliable tool for the diagnosis and with a thin to average body habitus. classification of malignant abdominal lymphomas.57 The utility of US notwithstanding, CT remains indispensable at The safety of image-guided percutaneous biopsy is well docu- our institution as a guidance method for percutaneous biopsy of mented. Several large multi-institutional reviews reported major most regions in the body. It is particularly useful when an abdom- complication rates ranging from 0.05% to 0.18% and mortalities inal mass is in a location that is inaccessible to US as a result of ranging from 0.008% to 0.031%.58-60 A large prospective study of bowel gas or body habitus. In the abdomen, CT provides excellent 3,393 biopsies (1,825 US-guided; 1,568 CT-guided) documented spatial resolution of all structures between the skin and the mass, an overall mortality of 0.06%, a major complication rate of 0.34% regardless of body habitus or lesion depth, and it provides an accu- (0.3% with US; 0.5% with CT), and a minor complication rate of rate image of the needle tip.We favor CT guidance for abdominal 2.9% (2.4% with US; 3.3% with CT).47 Procedure-related mor- masses that are located deep in the abdomen or in the retroperi- bidity and mortality appear to be largely unaffected by whether a toneum.The only limitation of CT in this setting is that it does not small-caliber or a large-caliber biopsy needle is used. A review of offer continuous visualization of the needle during insertion and 11,700 patients who underwent percutaneous abdominal biopsy biopsy. In most cases, however, CT guidance can reliably establish with 20- to 23-gauge needles found an overall complication rate of the direction and depth of the needle [see Figure 9]. only 0.05% and an overall mortality of only 0.008%.58 A single- Numerous different needles, covering a broad spectrum of cal- institution review of 8,000 US-guided needle biopsies performed ibers, lengths, and tip designs, are commercially available for use with both small- and large-caliber needles reported equivalent in percutaneous image-guided fine-needle aspiration (FNA) biop- results: a major complication rate of 0.187% and a mortality of sy. For convenience, these needles can be grouped into two main 0.038%.61 Of the rare major complications that occur, hemorrhage size categories: small caliber (20 to 25 gauge) and large caliber (14 is the most frequently reported; pneumothorax, pancreatitis, bile to 19 gauge). Small-caliber needles are used primarily for cytolog- leakage, peritonitis, and needle track seeding may also develop. ic analysis but may also be employed to obtain small pieces of tis- Needle-track seeding remains an important theoretical consid- sue for histologic analysis. The flexible shaft of small-caliber nee- eration when an abdominal mass appears likely to be malignant. dles allows them to be passed with minimal risk of tissue or organ According to some investigators, percutaneous needle biopsy has
  11. 11. © 2006 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 5 GASTROINTESTINAL TRACT AND ABDOMEN 2 Abdominal Mass — 11 the potential to seed between 103 to 104 tumor cells into the nee- ease,75 and the number of samples obtained. In one series that dle track.62,63 Nevertheless, tumor dissemination after percuta- included more than 200 patients with esophageal or gastric mass- neous biopsy remains exceedingly rare: with fewer than 100 cases es, a diagnosis was made in 70% of patients after the first biopsy, reported in the world literature, it has an estimated frequency of 95% of patients after the fourth biopsy, and 98.9% of patients after 0.005%,64-66 mostly occurring after biopsy of pancreatic, hepatic, the seventh biopsy.76 Several other studies have confirmed the high or retroperitoneal masses. Poorly planned biopsies of malignant sensitivity and specificity of EUS-guided biopsy (especially for the abdominal masses have the potential to exert adverse effects on diagnosis of extraluminal abdominal masses) and verified the safe- subsequent surgery and to compromise local tumor control; for- ty of the procedure (reported complication rates range from 0.3% tunately, such negative consequences remain rare. to 2%).68-71,77 It is worth noting that in the resection of a potential- ly curable abdominal mass, concern about needle-track contami- EUS-Guided Imaging and Biopsy nation is obviated when the path of the needle is removed as part EUS provides unique imaging information because it involves of the surgical specimen (as in pancreaticoduodenectomy for a the close apposition of a high-frequency ultrasound transducer, pancreatic head mass or gastrectomy for a stomach mass). called an echoendoscope (whereby image resolution is directly We consider EUS-guided biopsy for the diagnosis of masses related to frequency), to the structures being studied. As a result, that are not readily accessible to percutaneous biopsy, on the it can delineate abdominal masses and associated structures with grounds that it can obviate more invasive procedures (e.g., greater anatomic detail than standard transcutaneous ultrasonog- laparoscopy and laparotomy). In a 10-year study of the impact of raphy can. In general, EUS-guided biopsy is well suited for EUS on patient management, 86% of patients required no further abdominal masses that are too small for visualization by means of imaging, and 25% were able to avoid unnecessary laparotomy.77 other cross-sectional imaging modalities or that are inaccessible to Overall, EUS changed clinical management significantly in as percutaneous biopsy.67 The most frequently used EUS device is many as one third of the 537 patients studied.77 Nevertheless, the radial echoendoscope, which creates a 360º tomographic despite the high diagnostic yield achieved with EUS-guided biop- image perpendicular to the scope. The circumferential view ob- sy, results that are negative for tumor should not always be inter- tained with this instrument facilitates orientation and therefore is preted as proving that no tumor is present; laparoscopic or open more efficient for diagnostic imaging. Alternatively, the linear- biopsy may still be indicated. array echoendoscope, which generates an image parallel to the DIAGNOSTIC LAPAROSCOPY shaft of the scope, may be used. This instrument produces high- quality gray-scale images, as well as color and duplex images. The available evidence now clearly sup- EUS-guided biopsy with a linear scanning system offers clear and ports the role of laparoscopy in the diagno- consistent visualization of the biopsy needle along its entire path sis and management of abdominal masses. in real time, with excellent delineation of intervening tissues and We and others advocate the liberal use of without any interference from intestinal gas. laparoscopy as a primary staging tool for EUS has proved to be superior to other cross-sectional imaging upper and lower GI malignancies, believing modalities for detection and staging of pancreatic, gastric, and it to be a safe, cost-effective tool that offers a esophageal masses.68-71 For instance, in a patient with a pancreat- clear benefit in more than 20% of patients ic mass, EUS not only identifies the size of the mass and the peri- with these diseases.78,79 Preventing unneces- pancreatic lymph nodes but also delineates the relations of these sary laparotomy in selected patients by performing diagnostic structures to major blood vessels. EUS has also proved to be help- laparoscopy is associated with shorter hospital stays and earlier ini- ful in selecting patients for various neoadjuvant protocols. tiation of locoregional or systemic therapy. Moreover, laparoscopic Furthermore, the availability of high-frequency catheter-based ultrasonography80 and peritoneal cytology81 are known to provide intraductal ultrasonography (IDUS) now enables surgeons to added value in the staging of disease. Furthermore, diagnostic visualize masses within the biliary tree and obtain biopsy speci- laparoscopy can safely provide tissue samples from suspected lym- mens from them.72 phomatous masses for full diagnostic analysis.82 With the growth of Advantages notwithstanding, EUS technology has several dedicated minimally invasive fellowships and the improved quality important limitations. As with all forms of ultrasonography, a sub- and availability of laparoscopic training for general surgery resi- stantial period is required before the operator achieves proficien- dents and related subspecialties, the skill sets required for diagnos- cy. EUS is highly operator dependent; when it is done by an inex- tic laparoscopy are coming to be more widely mastered, and the perienced operator, the potential exists for serious misinterpreta- concerns once commonly expressed regarding intra-abdominal tions. For example, if an operator obtains only one view of a mass adhesions and effective biopsy techniques for abdominal masses in the head of the pancreas, the mass may appear to be invading now appear to be less problematic. vascular structures when it is not actually doing so. In the evalua- tion of pancreatic masses around vessels, the operator should always obtain multiple views. It cannot be overemphasized that Indications for Exploratory Laparotomy EUS and EUS-guided biopsy require personnel with sufficient Advances in diagnostic imaging, endoscopy, and minimally inva- experience and skill in both ultrasonography and endoscopy. sive surgery have nearly eliminated the need for open exploration EUS is frequently employed for diagnosis and staging of upper for the sole purpose of establishing a diagnosis in patients with an GI malignancies. In a large single-institution study of 267 pancre- abdominal mass. In selected cases, however, exploratory laparoto- atic masses that were sampled by means of EUS-guided biopsy my may still help in the assessment of abdominal masses that were and subsequently resected, the overall diagnostic accuracy was initially misinterpreted on preoperative evaluation. In general, 95.6%, the sensitivity was 94.6%, and the specificity was 100%.73 exploratory laparotomy should be reserved for those rare instances In studies of gastric and esophageal masses, diagnostic accuracy in which other modalities have failed to yield crucial information was related to the location of the biopsy,74 the histology of the dis- needed for evaluation and diagnosis of an abdominal mass.
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