In an elderly male (≥80 years) residing in a care facility who presents with 24‑hour severe abdominal pain, a soft, lax, diffusely tender abdomen, hyperactive bowel sounds, and no peritoneal rigidity, what is the most appropriate next diagnostic step: colonoscopy, sigmoidoscopy, abdominal ultrasound, or digital rectal examination?

Digital Rectal Examination (DRE) is the Most Appropriate Next Step

In an elderly male with severe diffuse abdominal pain, a soft non-rigid abdomen, and hyperactive bowel sounds, digital rectal examination should be performed immediately to assess for fecal impaction, rectal masses, or occult blood before proceeding to imaging. 1, 2

Rationale for DRE as the Initial Step

Critical Diagnostic Information from DRE

• Digital rectal examination is mandatory in acute abdomen evaluation and provides immediate bedside information about rectal masses (including palpable rectal cancer), fecal impaction, and the presence of blood 1
• In elderly patients with colon cancer presenting with abdominal pain, DRE may reveal impacted stool—an extremely common cause of severe pain in this population due to opioid use, decreased mobility, and tumor effects 2
• The American College of Emergency Physicians specifically recommends DRE to detect blood, masses, or fecal impaction as part of the immediate diagnostic approach 2

Clinical Context Supports DRE First

• The absence of peritoneal rigidity with hyperactive bowel sounds suggests obstruction rather than perforation 1
• This presentation is consistent with either incomplete bowel obstruction or severe constipation/fecal impaction—both diagnoses where DRE provides immediate actionable information 2
• In elderly patients, fecal impaction can cause severe abdominal pain mimicking obstruction or perforation, and DRE immediately identifies this treatable condition 2

Why Not the Other Options First?

Colonoscopy and Sigmoidoscopy (Options A & B)

• Endoscopy is contraindicated in acute abdomen with suspected obstruction or perforation until imaging excludes these complications 1
• These procedures require bowel preparation, which is dangerous in the setting of potential obstruction 1
• Endoscopy should only be considered after imaging confirms it is safe to proceed 1

Ultrasound Abdomen (Option C)

• While ultrasound is valuable for acute abdomen evaluation 1, 3, it should follow—not precede—DRE in this clinical scenario 1, 2
• CT scan with IV contrast is the gold standard imaging for elderly patients with severe abdominal pain (sensitivity 95%, specificity 96-99%) and should be obtained after DRE if obstruction or other serious pathology is suspected 1
• In elderly patients over 80 with acute abdominal pain, CT changed the clinical diagnosis in 43% of cases and influenced treatment plans in 65% 1
• Ultrasound has lower sensitivity than CT for detecting complications (61% vs 98.6% for CT) 1

Algorithmic Approach After DRE

If DRE Reveals Fecal Impaction:

• Plain radiography can exclude true obstruction while confirming impaction 2
• Manual disimpaction may provide immediate relief 2

If DRE Reveals Rectal Mass or Blood:

• Proceed immediately to CT abdomen/pelvis with IV contrast (>90% accuracy for identifying cause, site, and complications) 2
• This imaging will distinguish between obstruction, perforation, abscess, or other cancer-related complications 1

If DRE is Non-Diagnostic:

• Obtain CT scan with IV contrast urgently given the severity of pain and elderly age 1
• Check serum lactate—elevated levels suggest mesenteric ischemia (30-90% mortality if untreated) requiring immediate CT angiography 2

Critical Pitfalls to Avoid

• Do not assume normal vital signs exclude serious disease in the elderly—they often have blunted physiologic responses 2
• Do not mistake incomplete obstruction with watery diarrhea for gastroenteritis—this represents overflow diarrhea around an obstruction and leads to dangerous delays 2
• Do not skip DRE because it seems "low-tech"—it provides immediate diagnostic information that guides all subsequent management 1, 2
• In this age group with hyperactive bowel sounds and diffuse tenderness, large bowel obstruction from colon cancer is a leading concern, and DRE may palpate the obstructing lesion 1