A 72-year-old man with a history of chronic constipation and neuropsychiatric illness presents with acute abdominal pain, severe distension, and inability to pass stool or flatus for 3 days. On examination, he is afebrile, blood pressure 135/88 mmHg, heart rate 98/min. Abdomen is markedly distended and tympanic. Plain abdominal radiograph shows a massively dilated sigmoid colon with a characteristic twisted appearance creating a "coffee bean" or "omega" sign. What is the most likely diagnosis and the most appropriate initial management?

Explanation

## Clinical Diagnosis: Sigmoid Volvulus with Sigmoidoscopic Decompression ### Pathophysiology of Sigmoid Volvulus **Key Point:** Sigmoid volvulus occurs when the sigmoid colon twists around its mesentery (volvulus axis), creating a closed-loop obstruction. The twisted segment appears as a characteristic "coffee bean" or "omega" sign on plain radiography. ### Risk Factors for Sigmoid Volvulus | Risk Factor | Mechanism | |-------------|----------| | Chronic constipation | Elongated, redundant sigmoid loop | | Neuropsychiatric disease | Altered bowel motility and evacuation | | Chagas disease (endemic areas) | Megacolon with dilated, atonic sigmoid | | Institutionalization | Immobility + constipation | | Spinal cord injury | Loss of defecation reflex | | High-fiber diet (in predisposed) | Increased fecal bulk in redundant loop | This patient has **two major risk factors**: chronic constipation + neuropsychiatric illness. ### Radiographic Diagnosis ```mermaid flowchart TD A[Acute colonic obstruction]:::outcome --> B{Radiographic appearance?}:::decision B -->|Coffee bean/Omega sign| C[Sigmoid volvulus]:::outcome B -->|Bird's beak appearance| D[Carcinoma or stricture]:::outcome B -->|Thumbprinting + pneumatosis| E[Ischemic colitis]:::outcome C --> F{Strangulation signs?}:::decision F -->|No: stable, no peritonitis| G[Sigmoidoscopic decompression]:::action F -->|Yes: fever, peritonitis, shock| H[Immediate surgical exploration]:::urgent ``` ### Management Algorithm for Sigmoid Volvulus **High-Yield:** Sigmoid volvulus is the **second most common cause of large bowel obstruction** (after carcinoma) in developing countries, but the **most common in certain endemic regions** (Middle East, Africa, India). ### Initial Management: Sigmoidoscopic Decompression **Clinical Pearl:** Sigmoidoscopic decompression is the **first-line treatment** for uncomplicated sigmoid volvulus in a hemodynamically stable patient without peritonitis. Success rate is 60–90%. **Procedure Steps:** 1. Gentle sigmoidoscopy under light sedation 2. Identify the twisted segment (appears as a tight spiral narrowing) 3. Advance the scope carefully past the twist point 4. Aspirate gas and stool proximal to obstruction 5. Place a rectal tube or flatus tube across the decompressed segment 6. Leave tube in place for 24–48 hours to prevent re-volvulation ### Indications for Emergency Surgery **Warning:** Do NOT attempt sigmoidoscopy if: - Peritonitis is present (suggests perforation or gangrene) - Shock or hemodynamic instability - Fever with elevated lactate (suggests ischemia) - Radiographic evidence of perforation (free air) These patients require **immediate laparotomy** for resection. ### Definitive Management After Decompression After successful sigmoidoscopic decompression: - Keep NPO, continue IV fluids, monitor closely - Recurrence rate: 40–60% if managed conservatively alone - **Elective sigmoid colectomy** (within 2–4 weeks) is recommended to prevent recurrence - If recurrent volvulus or failed decompression → urgent surgical resection ### Why This Patient Needs Sigmoidoscopy, Not Surgery - **Hemodynamically stable:** BP normal, HR only mildly elevated - **No peritonitis:** Afebrile, no guarding/rigidity mentioned - **No perforation:** No free air on radiograph - **Classic presentation:** Coffee bean sign is diagnostic - **High success rate:** 60–90% of uncomplicated cases resolve with decompression