A 58-year-old man with a history of three prior abdominal surgeries presents to the emergency department with acute onset colicky abdominal pain, abdominal distension, and vomiting for 8 hours. On examination, he is afebrile, blood pressure 128/82 mmHg, heart rate 102/min. Abdomen is distended with visible peristaltic waves and hyperactive bowel sounds. Plain abdominal radiograph shows multiple air-fluid levels with a "step-ladder" appearance and dilated small bowel loops. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Adhesive Small Bowel Obstruction ### Key Clinical Features **Key Point:** The constellation of prior abdominal surgery, acute colicky pain, vomiting, visible peristaltic waves, and classic "step-ladder" air-fluid levels on plain radiography is pathognomonic for adhesive small bowel obstruction. ### Pathophysiology Adhesions form after abdominal surgery due to peritoneal trauma and inflammation. They create partial or complete mechanical obstruction of the small bowel lumen, leading to: 1. Increased intraluminal pressure proximal to the obstruction 2. Bowel wall edema and secretion accumulation 3. Retrograde peristalsis and vomiting 4. Characteristic radiographic findings ### Radiographic Findings in Small Bowel Obstruction | Finding | Significance | |---------|-------------| | Air-fluid levels | Indicates fluid accumulation and gas trapping | | "Step-ladder" pattern | Pathognomonic for small bowel obstruction | | Dilated small bowel (>3 cm) | Confirms small bowel involvement | | Transition point | May be visible on CT; indicates obstruction site | | Valvulae conniventes | Preserved in small bowel (unlike colon) | ### Clinical Pearl **Clinical Pearl:** Adhesions account for 60–75% of mechanical small bowel obstructions in developed countries. The risk increases with number of prior surgeries; three prior operations significantly elevates adhesion risk. ### High-Yield Management Algorithm ```mermaid flowchart TD A[Acute small bowel obstruction]:::outcome --> B{Signs of strangulation?}:::decision B -->|Yes: fever, peritonitis, shock| C[Immediate surgical exploration]:::urgent B -->|No: stable, no peritonitis| D[Nasogastric decompression + IV fluids]:::action D --> E{Resolution in 24-48 hrs?}:::decision E -->|Yes| F[Conservative management, discharge]:::action E -->|No| G[CT abdomen/pelvis for transition point]:::action G --> H[Surgical exploration if complete obstruction]:::action ``` ### Why Adhesions Are Most Likely Here - **Prior surgery:** Three abdominal surgeries = high adhesion risk - **Acute onset:** Consistent with mechanical obstruction - **Hyperactive bowel sounds + visible peristalsis:** Indicates early/partial obstruction trying to overcome blockade - **Step-ladder air-fluid levels:** Diagnostic hallmark of small bowel obstruction - **Stable vitals:** No signs of strangulation (yet) **High-Yield:** ~90% of adhesive small bowel obstructions resolve with conservative management (NPO, NG tube, IV fluids). Surgery is reserved for complete obstruction, strangulation signs, or failure to resolve in 48–72 hours.