145. Acute intestinal obstruction - classification, etiology, pathogenesis, clinical manifestations.

Acute intestinal obstruction - classification, etiology, pathogenesis, and clinical manifestations.

Acute intestinal obstruction is a sudden blockage that prevents the normal passage of intestinal contents, leading to accumulation of fluid and gas above the obstruction and potential life-threatening complications.

Classification

By nature of obstruction

By level

Etiology

Mechanical obstruction

• Adhesions (most common cause of SBO; post-surgical).
• Hernias (external or internal).
• Tumors (most common cause of LBO).
• Volvulus (twisting of bowel, often sigmoid or cecal).
• Intussusception (telescoping of one segment into another).
• Strictures (e.g., Crohn’s disease).
• Fecal impaction.

Paralytic ileus

• Postoperative state (especially after abdominal surgery).
• Peritonitis.
• Electrolyte imbalances (hypokalemia).
• Drugs (opioids, anticholinergics).
• Severe systemic illness.

Pathogenesis

Mechanical obstruction

1. Obstructed lumen → accumulation of gas and fluid above blockage.
2. Increased intraluminal pressure → venous congestion and bowel wall edema.
3. Progressing to impaired arterial blood flow → ischemia and possible necrosis.
4. Bacterial overgrowth and translocation → peritonitis and sepsis if perforation occurs.

Paralytic ileus

Loss of coordinated peristaltic activity → functional stasis of bowel contents without actual blockage.