In an elderly male with 24‑hour severe abdominal pain, a soft lax abdomen, diffuse tenderness, hyperactive bowel sounds and no rigidity, what is the most appropriate next step: colonoscopy, flexible sigmoidoscopy, or abdominal ultrasound?

Abdominal Ultrasound is the Most Appropriate Next Step

In an elderly male with severe abdominal pain, diffuse tenderness, hyperactive bowel sounds, and a soft abdomen without rigidity, abdominal ultrasound (US) is the most appropriate initial imaging modality to rapidly assess for potential causes while avoiding delays in diagnosis.

Clinical Context and Differential Diagnosis

The clinical presentation suggests an acute abdominal process requiring urgent evaluation, but the absence of peritoneal signs (no rigidity) makes immediate surgical intervention less likely. The key differential diagnoses include:

• Sigmoid volvulus – particularly relevant in elderly males, presenting with severe pain, abdominal distension, and hyperactive bowel sounds initially 1
• Small bowel obstruction – can present with hyperactive bowel sounds in early stages before progression to ileus 1
• Ischemic bowel – requires urgent identification but may not show rigidity in early stages 1

Why Ultrasound is Preferred in This Setting

Ultrasound provides rapid, bedside assessment without radiation exposure or contrast administration, which is particularly valuable in elderly patients who may have renal impairment or require immediate triage decisions 1. While CT abdomen/pelvis is the gold standard for suspected high-grade obstruction with diagnostic accuracy exceeding 90%, it requires patient transport and may delay intervention 1.

In the acute setting with hyperactive bowel sounds and no rigidity, ultrasound can:

• Identify free fluid or signs of perforation 1
• Detect bowel wall thickening or abnormal peristalsis 1
• Assess for colonic distension suggestive of volvulus 1
• Guide the urgency of subsequent imaging or endoscopy 1

Why Not Colonoscopy or Sigmoidoscopy First?

Endoscopic procedures should NOT be the initial step in this acute presentation because:

• Colonoscopy requires bowel preparation and is technically difficult in the setting of acute obstruction or volvulus, with limited diagnostic value before imaging confirms the diagnosis 1
• Flexible sigmoidoscopy is indicated for sigmoid volvulus ONLY after imaging confirms the diagnosis and excludes perforation or ischemia 1. The 2023 WSES guidelines explicitly state that endoscopic decompression should be performed "in patients in whom ischemia or perforation is not suspected clinically and/or radiologically" 1
• Performing endoscopy without prior imaging risks missing critical diagnoses like perforation, ischemia, or closed-loop obstruction 1

Algorithmic Approach

1. Immediate assessment: Obtain vital signs, laboratory tests (CBC, lactate, CRP), and assess for peritoneal signs 1
2. First-line imaging: Abdominal ultrasound for rapid bedside evaluation 1
3. If ultrasound suggests obstruction/volvulus: Proceed to CT abdomen/pelvis with IV contrast (oral contrast NOT needed and may delay diagnosis) 1
4. If CT confirms sigmoid volvulus without ischemia/perforation: Proceed to flexible sigmoidoscopy for decompression 1
5. If signs of ischemia, perforation, or septic shock: Urgent surgical consultation 1

Critical Pitfalls to Avoid

• Do not delay imaging to perform endoscopy first – this risks catastrophic complications if perforation or ischemia is present 1
• Hyperactive bowel sounds do not exclude serious pathology – they may represent early obstruction before progression to ileus 1
• The absence of rigidity does not rule out ischemia – early ischemic bowel may present with a soft abdomen 1
• In elderly patients with volvulus, mortality reaches 12% with emergency surgery, making accurate pre-operative diagnosis essential 1