Harvey's Garden

Bowel obstruction

3 min read

  • Classifications
    • By Location:
      • Small Bowel Obstruction (SBO): Blockage in the small intestine. More common.
      • Large Bowel Obstruction (LBO): Blockage in the large intestine.
    • By Severity:
      • Partial: Allows some liquid and gas to pass. May resolve with conservative Tx.
      • Complete: Allows nothing to pass. Usually requires surgical intervention.
    • By Pathophysiology:
      • Mechanical: A physical barrier obstructing the lumen (e.g., adhesion, tumor). The most common type.
      • Functional (Ileus): Impaired peristalsis without a physical barrier.
    • By Vascular Compromise:
      • Simple: Obstruction without vascular compromise.
      • Strangulated: Obstruction where blood flow is compromised, leading to ischemia and necrosis. A surgical emergency.
      • Closed-Loop: A segment of bowel is obstructed at two points (e.g., volvulus or LBO with a competent ileocecal valve). High risk of rapid strangulation.
  • Etiology
    • SBO: Most common causes are Adhesions (from prior surgery), Bulges (hernias), and Cancer (malignancy).
    • LBO: Most frequent causes are malignancy (colorectal cancer), volvulus (sigmoid and cecal), and diverticular disease.
    • Functional Obstruction (Ileus): Often occurs post-operatively or due to medications (e.g., opioids), electrolyte imbalances (especially hypokalemia), and severe illness.
  • Pathophysiology
    • A mechanical blockage leads to the accumulation of gas and fluid proximal to the obstruction, causing bowel distention.
    • Increased intraluminal pressure can compromise blood flow to the bowel wall, leading to ischemia, necrosis, and perforation.
    • Significant fluid shifts into the bowel lumen (“third-spacing”) and vomiting can cause severe dehydration and electrolyte abnormalities.
  • Clinical Presentation
    • Cardinal symptoms include colicky abdominal pain, nausea/vomiting, abdominal distention, and obstipation (inability to pass flatus or stool).
    • SBO: Pain is often mid-abdominal and colicky. Vomiting is typically early and bilious in proximal obstructions, becoming feculent in distal obstructions.
    • LBO: Presentation is often more insidious, with more pronounced distention and less vomiting, especially if the ileocecal valve is competent.
    • Physical Exam: Early on, bowel sounds may be high-pitched and hyperactive (“tinkling”), but they become hypoactive or absent later, especially with ischemia. Peritoneal signs (e.g., rigidity, rebound tenderness) suggest perforation or strangulation.
  • Diagnosis
    • Abdominal X-ray (AXR): Often the initial imaging study.
      • SBO: Shows multiple dilated loops of small bowel (>3 cm) with air-fluid levels, often in a “step-ladder” pattern.
      • LBO: Shows marked colonic dilation (>6 cm, >9 cm for cecum) proximal to the obstruction.
    • CT Scan (Abdomen/Pelvis with contrast): This is the gold standard imaging modality. It can confirm the diagnosis, identify the location and cause of the obstruction (the “transition point”), and detect complications like ischemia, perforation, or a closed loop.
    • Labs: A complete blood count (CBC) may show leukocytosis (suggesting ischemia). An elevated lactate level is a red flag for ischemia. Electrolyte panels often reveal dehydration and disturbances (e.g., hypokalemic, hypochloremic metabolic alkalosis from vomiting).
  • Management
    • Initial/Conservative (“Drip and Suck”):
      • NPO (Nil Per Os - nothing by mouth).
      • IV fluid resuscitation to correct dehydration and electrolyte imbalances.
      • Nasogastric (NG) tube decompression to remove fluid and air from the stomach and proximal bowel, relieving distention and vomiting.
      • This approach is often successful for partial SBO due to adhesions.
    • Surgical Intervention:
      • Indications: Complete or closed-loop obstructions, signs of bowel compromise (ischemia, necrosis, perforation), strangulated hernias, or failure of conservative management (typically after 48 hours).
      • The specific procedure depends on the cause (e.g., lysis of adhesions, hernia repair, bowel resection).
  • Complications
    • Bowel ischemia and necrosis (strangulation).
    • Perforation, leading to peritonitis and sepsis.
    • Dehydration and acute kidney injury.
    • Electrolyte imbalances.

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