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, the abdomen is distended with visible peristaltic waves. Bowel sounds are high-pitched and tinkling. Plain abdominal X-ray shows dilated small bowel loops with air-fluid levels in a "staircase" pattern, and the colon appears collapsed. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Small Bowel Obstruction from Adhesions ### Key Clinical Features **Key Point:** The combination of prior abdominal surgery (appendicectomy 20 years ago), colicky pain, high-pitched tinkling bowel sounds, and the classic "staircase" pattern of dilated small bowel loops with air-fluid levels on X-ray is pathognomonic for small bowel obstruction (SBO). ### Radiological Findings **High-Yield:** The "staircase" or "ladder-like" appearance of air-fluid levels is the hallmark of SBO. The collapsed colon rules out large bowel obstruction as the primary pathology. ### Why Adhesions Are the Culprit 1. **History of prior abdominal surgery** — appendicectomy is a common cause of intra-abdominal adhesions 2. **Time interval** — adhesions can form within weeks but often present years later after minor trauma or spontaneously 3. **Accounts for 60–75% of SBO** in developed countries [cite:Sabiston 21e Ch 45] 4. **Mechanical obstruction pattern** — the colicky pain and high-pitched bowel sounds indicate incomplete obstruction with peristalsis attempting to overcome the blockage ### Clinical Pearl **Clinical Pearl:** Visible peristaltic waves and colicky pain suggest a **mechanical obstruction** (adhesions, hernia, volvulus) rather than paralytic ileus, where pain is typically absent and bowel sounds are silent. ### Mnemonic for SBO Causes **Mnemonic: CHAMPS** — Crohn's disease, Hernia, Adhesions, Malignancy, Pseudo-obstruction, Strictures. In this case, adhesions from prior surgery are the most likely. ### Management Approach ```mermaid flowchart TD A[SBO suspected]:::outcome --> B{Complete or partial?}:::decision B -->|Partial| C[Conservative: NG tube, fluids, monitor]:::action B -->|Complete| D[Surgical exploration]:::action C --> E{Resolves in 48-72 hrs?}:::decision E -->|Yes| F[Discharge, advise diet]:::action E -->|No| D D --> G[Adhesiolysis]:::action G --> H[Resolution]:::outcome ``` ### Why Collapsed Colon Matters **Key Point:** A collapsed colon on imaging indicates that the obstruction is proximal (small bowel), not in the colon itself. This rules out primary colonic causes like volvulus or malignancy.