Harvey's Garden

Bowel obstruction

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aliasesSmall bowel obstruction

3 min read

Epidemiology & Risk Factors

  • Small Bowel Obstruction (SBO):
    • Adhesions (prior surgery): #1 cause overall (60-70%). c
    • Hernias: #2 cause overall; #1 cause in pts w/o surgical Hx.
    • Crohn disease: Stricture formation in terminal ileum. c
    • Malignancy: Primary or metastatic disease.
    • Intussusception: Common in pediatric pts.
  • Large Bowel Obstruction (LBO):
    • Colorectal cancer: #1 cause overall.
    • Volvulus: Sigmoid (elderly/institutionalized) or cecal (younger pts).
    • Diverticulitis: Chronic strictures.

Clinical Features

  • SBO:
    • Crampy, paroxysmal abdominal pain.
    • Early bilious vomiting (more prominent in proximal SBO).
    • Abdominal distension (more prominent in distal SBO).
    • Obstipation (lack of flatus/stool; late finding).
    • PE: High-pitched “tinkling” bowel sounds (early) or silent abdomen (late). Tympanitic abdomen. c
  • LBO:
    • Gradual onset of infraumbilical cramping pain.
    • Markedly distended abdomen.
    • Late/feculent vomiting (only if ileocecal valve is incompetent).
    • Early obstipation.

Diagnosis

  • Initial Test: Abdominal X-ray (AXR) (supine/upright).
    • SBO findings: Dilated loops of small bowel (>3 cm), multiple air-fluid levels on upright view, absence of distal colonic gas.
    • LBO findings: Colonic dilation (>6 cm; cecum >9 cm).
    • Sigmoid Volvulus: “Coffee bean” sign arising from pelvis/LUQ.
    • Cecal volvulus: Embryo/comma sign pointing to RUQ.
  • Best/Confirmatory Test: CT abdomen & pelvis w/ IV contrast.
    • Identifies transition point, etiology (e.g., mass, hernia), and complications.
    • Differentiates partial vs. complete obstruction.
  • Key Labs:
    • CBC: Leukocytosis (suggests ischemia, necrosis, or perforation).
    • BMP: Dehydration/electrolyte abnormalities (hypokalemic, hypochloremic metabolic alkalosis from vomiting; prerenal AKI).
    • Serum lactate: Elevated levels suggest bowel ischemia.

Differential Diagnostics

  • Paralytic Ileus:
    • Differentiating features: Uniformly dilated loops of both small & large bowel on AXR; absent bowel sounds; typically post-op or associated w/ hypokalemia or opioids.
  • Ogilvie Syndrome (Acute Colonic Pseudo-obstruction):
    • Differentiating features: Massive colonic dilation without mechanical obstruction; occurs in critically ill/elderly pts; Rx with Neostigmine if refractory.
  • Mesenteric Ischemia:
    • Differentiating features: Pain out of proportion to exam; typically presents w/ hematochezia, CV risk factors (AFib), and lack of mechanical obstruction signs on CT.

Management

  1. Initial Stabilization:
    • Make pt NPO (nil per os) immediately.
    • NGT decompression to suction.
    • Aggressive IVF resuscitation (Normal Saline or Lactated Ringer’s) + electrolyte replacement.
    • Monitor urine output (Foley catheter).
  2. Conservative/Non-operative Management:
    • Indicated for: Partial SBO, early post-op SBO, or uncomplicated Crohn-related SBO.
    • Regimen: Serial abdominal exams and imaging (AXR) every 12-24 hours.
  3. Surgical Intervention:
    • Emergent Exploratory Laparotomy/Laparoscopy:
      • Indicated immediately for signs of complicated obstruction (strangulation, ischemia, necrosis, perforation):
        • Peritoneal signs (rebound tenderness, guarding, rigidity).
        • Hemodynamic instability/shock.
        • Fever, persistent tachycardia, leukocytosis.
        • Pneumoperitoneum (free air under diaphragm) on AXR/CT.
    • Urgent/Scheduled Surgery:
      • Indicated for complete mechanical obstruction that fails to resolve w/ conservative management after 24-48 hours.

Complications

  • Bowel ischemia/infarction.
  • Bowel perforation & peritonitis.
  • Intra-abdominal abscess.
  • Sepsis/septic shock & MODS.
  • Aspiration pneumonia.∂

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