A 58-year-old man presents to the emergency department with a 3-day history of colicky abdominal pain, abdominal distension, and constipation. He had undergone an open appendicectomy 20 years ago. On examination, he is afebrile, blood pressure 110/70 mmHg, and the abdomen is distended with visible peristaltic waves. Bowel sounds are high-pitched and tinkling. Abdominal X-ray shows dilated small bowel loops with air-fluid levels in a stepladder pattern, and the colon appears collapsed. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Adhesive Small Bowel Obstruction ### Key Clinical Features **Key Point:** This patient presents with the classic triad of small bowel obstruction (SBO): colicky pain, abdominal distension, and constipation, with a significant risk factor (prior abdominal surgery). ### Pathophysiology Adhesions account for approximately 60–75% of all small bowel obstructions in developed countries. Post-operative adhesions form within weeks to months after abdominal surgery and can cause obstruction years or decades later. The mechanical obstruction causes: 1. Accumulation of intestinal contents proximal to the obstruction 2. Bowel distension and increased intraluminal pressure 3. Impaired blood supply if the obstruction is complete or strangulated ### Radiological Findings | Finding | Significance | |---------|-------------| | Dilated small bowel loops | Proximal accumulation of contents | | Air-fluid levels in stepladder pattern | Classic sign of SBO | | Collapsed colon | Indicates complete obstruction | | Absence of free air | Rules out perforation | **High-Yield:** The stepladder pattern of air-fluid levels on upright X-ray is pathognomonic for small bowel obstruction and distinguishes it from colonic obstruction (which shows haustra, not valvulae conniventes). ### Clinical Pearl High-pitched, tinkling bowel sounds ("musical" bowel sounds) occur in early or partial obstruction as the bowel attempts to push contents past the obstruction. Silent abdomen suggests advanced obstruction with bowel fatigue or perforation. ### Why Adhesions Are Most Likely Here - **Prior abdominal surgery** is the single strongest risk factor - **No fever** rules out inflammatory causes (Crohn's, diverticulitis) - **Acute presentation** is typical of adhesions (can occur suddenly after years of quiescence) - **Complete obstruction pattern** (collapsed colon) is more common with adhesions than partial strictures ### Management Approach 1. **Nasogastric decompression** — standard initial management 2. **IV fluids and electrolyte correction** — address dehydration and metabolic derangements 3. **Serial clinical examination** — assess for signs of strangulation (fever, peritonitis, leukocytosis) 4. **CT imaging** (if diagnosis uncertain) — can identify transition point and assess for strangulation 5. **Surgical intervention** — indicated if signs of strangulation, failure to resolve in 48–72 hours, or recurrent episodes **Mnemonic: SOBS** — Signs Of Bad Strangulation: Severe pain, Older age, Bloody stools, Shock. These warrant urgent surgery.