What are the most common causes of gut obstruction, in order of rank?

Most Common Causes of Intestinal Obstruction by Rank

Small Bowel Obstruction

Adhesions are the leading cause of small bowel obstruction, accounting for 55-75% of all cases, followed by hernias (15-25%), and malignancies (5-10%). 1, 2

Ranked by Frequency:

1. Adhesions (55-75%) - Fibrous tissue connecting normally separated peritoneal surfaces, typically forming after abdominal surgery but can occur in virgin abdomen (26-100% of cases without prior surgery) 1, 2

2. Hernias (15-25%) - Including external hernias (inguinal, femoral, umbilical, incisional) and internal hernias (paraduodenal, foramen of Winslow); abdominal wall hernias account for approximately 10% of cases 2

3. Malignancies (5-10%) - Both primary small bowel tumors (NETs, lymphoma, carcinomas) and metastatic disease (commonly from colon, ovary, or prostate); in virgin abdomen, malignancy accounts for 4-41% of cases 1, 2

4. Other causes - Including intussusception, volvulus, gallstone ileus, bezoars/foreign bodies, inflammatory bowel disease (Crohn's disease), Meckel's diverticulum, radiation-induced strictures, and carcinomatosis peritoneal 1, 2

Large Bowel Obstruction

Colorectal cancer is the dominant cause of large bowel obstruction, responsible for approximately 60% of cases. 1

Ranked by Frequency:

1. Colorectal cancer (60%) - The most frequent cause of colonic obstruction 1, 3

2. Volvulus (30%) - Primarily sigmoid volvulus 1, 3

3. Diverticular disease (30%) - Note: percentages overlap as some studies report combined frequencies 1

4. Inflammatory bowel disease - Can cause stenosis and obstruction 1

5. Megacolon - From Hirschsprung disease or Chagas disease 1

Key Clinical Pearls:

• History of prior abdominal surgery has 85% sensitivity and 78% specificity for predicting adhesive small bowel obstruction 1, 2

• Hernias are the most common cause of strangulation (requiring urgent surgery), despite adhesions being the most common overall cause of obstruction 4

• CT scan is the most accurate imaging modality for determining etiology with 76% accuracy compared to operative findings 2

• In patients over 40 years, adhesions and malignancy predominate, while hernias and intussusception are more common in children 5