A 62-year-old man from rural India presents with acute onset abdominal distension, colicky pain, and vomiting for 18 hours. On examination, he is dehydrated with visible peristaltic waves. Plain abdominal radiograph shows multiple dilated small bowel loops with air-fluid levels and a transition zone in the distal ileum. No free air is visible. Vital signs are stable. What is the most appropriate next step in management?

Explanation

## Clinical Context This patient presents with **acute small bowel obstruction** with clinical and radiological evidence of a transition zone. The vital signs are stable and there is no evidence of perforation (no free air). The clinical presentation is classic for mechanical obstruction. ## Management Algorithm for Acute Small Bowel Obstruction ```mermaid flowchart TD A[Acute SBO suspected]:::outcome --> B{Signs of perforation?}:::decision B -->|Yes: free air, peritonitis| C[Immediate laparotomy]:::urgent B -->|No| D{Vital signs stable?}:::decision D -->|Unstable/septic| E[Resuscitate + urgent surgery]:::urgent D -->|Stable| F[Nasogastric decompression]:::action F --> G[IV fluids, electrolyte correction]:::action G --> H[CT abdomen with oral/IV contrast]:::action H --> I{Complete obstruction?}:::decision I -->|Yes| J[Surgical consultation]:::action I -->|No/Partial| K[Conservative management trial]:::action ``` ## Why Nasogastric Tube + IV Fluids + CT Abdomen? **Key Point:** In **stable patients with acute SBO without peritonitis**, the standard approach is: 1. **Nasogastric decompression** — relieves distension, reduces vomiting, allows assessment of output 2. **IV fluid resuscitation** — corrects dehydration and electrolyte abnormalities (especially K^+^ loss from vomiting) 3. **CT abdomen with oral and IV contrast** — gold standard imaging to: - Confirm obstruction and identify transition zone - Determine **completeness** of obstruction (partial vs. complete) - Identify **etiology** (adhesion, hernia, malignancy, volvulus) - Assess for complications (ischemia, perforation) **High-Yield:** CT has **95% sensitivity and specificity** for mechanical SBO and guides management: partial obstruction may resolve with conservative care; complete obstruction requires surgery. **Clinical Pearl:** Plain radiographs (as shown here) are insensitive for etiology and cannot reliably distinguish partial from complete obstruction. CT is the next logical step after initial resuscitation. ## Why NOT Immediate Laparotomy? Patient is stable, no peritoneal signs, no free air. Surgery is indicated only after imaging confirms complete obstruction or if patient deteriorates. ## Why NOT Ultrasound? Ultrasound has poor sensitivity in acute obstruction due to bowel gas. It may assess wall thickness but cannot reliably determine obstruction level or etiology. ## Why NOT Barium Enema? Barium is contraindicated in suspected small bowel obstruction (risk of impaction). Barium enema is used for **colonic obstruction**, not ileal obstruction. CT is superior.