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Bowel obstruction.pdf
Mechanical bowel obstruction is caused by structural barriers like adhesions or tumors blocking intestinal contents. The most common causes are abdominal adhesions, hernias, and colorectal cancer. This leads to a build up of gas and fluids proximal to the obstruction, causing pain, vomiting, distention and potentially ischemia if not resolved. Paralytic ileus is a functional obstruction caused by impaired peristalsis due to factors like surgery or infection. Treatment involves decompression with NG tubes, IV fluids and electrolytes, and surgery if signs of complication or failure to improve. Surgical intervention aims to release the obstruction and prevent complications.
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Bowel obstruction.pdf
- 1. Bowel obstruction • Mechanicalbowel obstruction “dynamic”( tumor, adhesions) • functional bowel obstruction “adynamic”(Temporary functional impairment of peristalsis) Failure of propulsion of intestinal contents Etiology Etiology of bowel obstruction SBO LBO Most common causes •Bowel adhesions ◦ history of abdominal surgery, abdominal tuberculosis •Incarcerated hernias: second most common cause of SBO •Malignant tumors (colorectal carcinoma) •Diverticulitis •Volvulus Other causes •Strictures (e.g., Crohn disease) •Malignant tumors or metastases •Gallstone ileus •Foreign body impaction •Adhesions •Strictures (e.g., ibd) •Foreign body impaction Functional (adynamic): Paralytic ileus Mesentric vascular occlusion (MVO) Bowel obstruction → stasis contents and gas proximal to the obstruction → ↑ intraluminal pressure • Gaseous abdominal distention → sequestration of fluids within the distended bowel loops (third spacing) → dehydration and hypovolemia • Vomiting → loss of fluid and Na+, K+, H+, and Cl- → hypokalemia, metabolic alkalosis, and hypovolemia • Compression of intestinal veins and lymphatics → bowel wall edema → compression of intestinal arterioles and capillaries → bowel ischemia ↑ Bowel wall permeability → translocation of microbes to the peritoneal cavity → sepsis Necrosis and perforation of the bowel wall → peritonitis Pathophysiology Clinical features features associated with the site of bowel obstruction Clinical feature SBO LBO Abdominal pain • Colicky, periumbilical • Colicky or constant Vomiting and/or nausea • Early onset • Larger volume of vomitus than in LBO • Bilious • Late onset • Initially bilious • Progresses to fecal vomiting (presence of feces in vomitus) Constipation or obstipation • Late onset in proximal SBO • Early onset in distal LBO Abdominal distention • Typically less severe than in LBO • Early and significant abdominal distention Examination findings • Dehydration and possible hypovolemia (hypotension, dry mucous membranes) • Diffuse abdominal tenderness • Tympanic percussion • Increased high-pitched bowel sounds (early) or the absence of any bowel sounds (late) • Collapsed, empty rectum on digital rectal examination (complete bowel obstruction); or impacted feces Yellow - green fluid Paralytic ileus (No colic)
- 2. Diagnostics A- Imaging • Initialimaging modality (depends on type of bowel obstruction and hemodynamic stability of the patient) 1- Acute bowel obstruction Stable patients (CT abdomen and pelvis + IV contrast) Unstable patients (X-ray erect position or abdominal U/S first) 1- Dilation 2- Multiple air fluid level 3- For detecting SBO or LBO • Transverse diameter Small bowel > 3 cm Large bowel > 6 cm Cecum > 9 cm • Site SBO (Dilated loops are central) LBO (Dilated loops are Peripheral) • Mucosal Folds SBO (Plicae Circulares) LBO (Haustra) 2- Subacute bowel obstruction • Preferred: CT abdomen and pelvis with IV contrast • Alternatives: MRI with and/or without IV contrast Barium Study Barium enema • Bird beak sign (volvulus) • Apple core sign (colonic malignancy) Barium Swallow Barium follow-through Barium meal B- Laboratory investigations 1- CBC (WBC Increase in cases of strangulation) 2- Serum electrolytes (decreased sodium and potassium levels)
- 3. Differential diagnoses vomiting orConstipation abdominal pain Abdominal distention Abdominal tenderness ◦ Bowel perforation ◦ Mesenteric ischemia ◦ Inflammatory bowel disease ◦ Acute appendicitis Mechanical bowel obstruction vs. paralytic ileus Mechanical bowel obstruction Paralytic ileus Definition • structural barrier • impairment of peristalsis Etiology • Small bowel obstruction ◦ Bowel adhesions ◦ Incarcerated hernias • Large bowel obstruction ◦ Malignant tumors (colorectal carcinoma) ◦ Volvulus • Recent abdominal surgery • Atherosclerotic disease • Abdominal infections or inflammatory conditions • medications (opioids, anticholinergics, antiparkinsonian agents) Clinical features • Colicky abdominal pain • Vomiting • Obstipation or constipation • Abdominal distention • High-pitched bowel sounds (early) • Absent bowel sounds (late) • Diffuse, continuous abdominal pain • Vomiting • Obstipation or constipation • Marked abdominal distention • Absent bowel sounds Findings on imaging • Dilated bowel loops proximal to obstruction • Collapsed bowel loops distal to obstruction • Multiple air-fluid levels • Cause of obstruction (e.g., tumor) • Pendular peristalsis on ultrasound (absent in late mechanical bowel obstruction) • Diffusely dilated small and large bowel loops • No evidence of mechanical obstruction • Absent peristalsis ◦ Acute pancreatitis ◦ Diverticulitis ◦ Toxic megacolon ◦ Chronic megacolon Treatment 1- Non-operative management • Early postoperative bowel obstruction (within 6 weeks of abdominal surgery) • Partial bowel obstruction with no evidence of complications 1- ABCDE Approach 2- Tow lines IV 3- NPO (Bowel Rest) 4- IV Fluid & Electrolyte & analgesics (nonopioid analgesics) 5- NG Tube (if vomiting & Distention) 6- Imaging according to approach 2- Interventional management • Complicated BO (signs of ischemia, perforation) • Closed-loop BO (volvulus, Irreducible hernia) • patients with hemodynamic instability (heart rate, blood pressure) • Failure of nonoperative management (i.e., no improvement after 3 days of NOM) • Procedure (Exploratory laparotomy)
- 4. 3- Endoscopic intervention Canbe considered for bowel obstruction with no signs of strangulation or perforation Complications • Bowel ischemia • Bowel perforation • Peritonitis Preoperative • Decompression • Relieves congestion & oedema of the intestines and helps return of tone & peristalsis Operative • For anaesthesia (prevents vomiting & aspiration pneumonia) • For surgeon (Easy closure of the abdomen) Postoperative • prevent massive toxic absorption after release of obstruction • Reduces postoperative paralytic ileus (distention and vomiting) NG Tube Benefits: