The most common cause of small intestinal obstruction is:
Intussusception
Iatrogenic adhesion
Trauma
Carcinoma
Adhesion secondary to previous surgery are by far the most common cause for small bowel obstruction. Adhesions paicularly after pelvic surgery are responsible for more than 60% of cause of small bowel obstruction. Causes of small bowel obstruction in order of frequency: Adhesions (Approximately 60%) commonest Malignant tumors (approximately 20%) second most common cause. Most commonly these tumors are metastatic lesions. Hernias (Approximately 10%) Crohn's disease (approximately 5%) Ref: Sabiston 18/e, Page 1290.