In mechanical small bowel obstruction, which of the following is the most common cause in the developed world?

Explanation

## Epidemiology of Small Bowel Obstruction Causes **Key Point:** Adhesions account for 60–75% of mechanical small bowel obstructions in developed countries, making them the single most common etiology. ### Cause-Specific Breakdown | Cause | Frequency (%) | Geography | Notes | |-------|---------------|-----------|-------| | Adhesions | 60–75 | Developed world | Post-surgical (80% of adhesion cases); post-inflammatory | | Hernia | 10–15 | Developed world | Incarcerated external or internal herniae | | Volvulus | 5–10 | Developed world | More common in sigmoid colon; rare in small bowel | | Malignancy | 5–10 | Developed world | Extrinsic or intraluminal; usually advanced disease | | Intussusception | 1–3 | Pediatric (< 3 years) | Rare in adults; Meckel's diverticulum may be lead point | ### Geographic Variation **High-Yield:** In developing countries (India, Africa, Middle East), volvulus and internal herniae (paraduodenal, parajejunal) are relatively more common due to higher rates of untreated herniae and anatomic predisposition. **Clinical Pearl:** Post-operative adhesions typically develop 4–6 weeks after abdominal surgery but can present years later. Lower abdominal and pelvic surgeries carry the highest adhesion risk. ### Why Adhesions Dominate in Developed World 1. High frequency of elective abdominal surgery (cesarean section, appendectomy, cholecystectomy) 2. Better access to hernia repair reduces incarcerated hernia rates 3. Earlier diagnosis and treatment of malignancy reduces obstruction from advanced tumors 4. Improved nutritional status and living conditions reduce inflammatory causes