A 58-year-old man from rural India presents with a 3-day history of colicky abdominal pain, abdominal distension, and absolute constipation. On examination, his abdomen is distended with visible peristaltic waves. Bowel sounds are high-pitched and tinkling. Plain abdominal X-ray shows multiple dilated small bowel loops with air–fluid levels in a "staircase" pattern, and the large bowel is collapsed. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Adhesive Small Bowel Obstruction ### Key Clinical Features **Key Point:** The constellation of colicky pain, visible peristaltic waves, high-pitched tinkling bowel sounds, and the **staircase pattern** of dilated small bowel loops with air–fluid levels on X-ray is pathognomonic for mechanical small bowel obstruction, most commonly due to adhesions. ### Radiological Hallmarks | Feature | Adhesive SBO | Sigmoid Volvulus | Mesenteric Ischemia | Paralytic Ileus | |---------|--------------|------------------|---------------------|------------------| | **Bowel pattern** | Dilated small loops in staircase | Dilated sigmoid (coffee bean sign) | Dilated loops + wall edema | Dilated loops uniformly | | **Bowel sounds** | High-pitched, tinkling | Normal or decreased | Absent (early) | Absent | | **Air–fluid levels** | Multiple, staircase | Localized to sigmoid | Diffuse | | **Collapsed colon** | Yes | No (dilated sigmoid) | Variable | No | | **Peristaltic waves** | Visible, forceful | Absent | Absent | Absent | ### Why This Is Adhesive SBO 1. **Staircase pattern** — classic for small bowel mechanical obstruction; reflects sequential dilation of proximal loops as they attempt to push past the obstruction. 2. **Visible peristaltic waves** — indicates the bowel is still contracting against an obstruction (mechanical, not paralytic). 3. **High-pitched tinkling sounds** — pathognomonic for mechanical obstruction; absent in paralytic ileus. 4. **Collapsed large bowel** — confirms the obstruction is proximal (small bowel), not in the colon. 5. **Adhesions are the most common cause** of mechanical small bowel obstruction in non-operated patients in India; in post-operative patients, adhesions account for >60% of cases. ### Pathophysiology of Mechanical Obstruction ```mermaid flowchart TD A[Mechanical obstruction<br/>adhesion/stricture]:::outcome --> B[Proximal bowel dilates<br/>fluid accumulation]:::action B --> C[Increased intraluminal pressure]:::action C --> D[Forceful peristalsis<br/>High-pitched sounds]:::action D --> E[Visible peristaltic waves]:::outcome A --> F[Distal bowel collapses<br/>no gas distally]:::outcome ``` **High-Yield:** The **staircase pattern** + **visible peristaltic waves** + **high-pitched bowel sounds** + **collapsed colon** = mechanical small bowel obstruction until proven otherwise. ### Clinical Pearl **Clinical Pearl:** In a non-operated patient, adhesions from prior abdominal surgery (even remote) are the leading cause. However, in a patient with no surgical history, consider Crohn's disease, tuberculosis (common in India), or malignancy. The absence of fever and systemic toxicity here makes TB and malignancy less likely acutely. ### Management Approach **Key Point:** Most adhesive obstructions (70–80%) resolve with conservative management: NPO, nasogastric decompression, IV fluids, and electrolyte correction. Surgery is reserved for signs of strangulation, perforation, or failure to resolve within 48–72 hours.