In an 82‑year‑old man with a three‑month history of constant dull lower‑abdominal pain that worsens on standing and no urinary symptoms, what is the appropriate next step in evaluation?

Diagnostic Evaluation of Chronic Lower Abdominal Pain in an 82-Year-Old Male

Order a contrast-enhanced CT scan of the abdomen and pelvis immediately to distinguish between bladder pathology, colonic disease (particularly diverticulitis or malignancy), and other serious conditions that require urgent intervention. 1

Why Imaging is Mandatory in This Case

Your clinical suspicion of bladder or colon etiology is appropriate, but clinical assessment alone misdiagnoses 34–68% of cases in elderly patients, making imaging essential rather than optional. 1 The combination of:

• Constant dull pain for 3 months (chronic presentation)
• Worsening with standing (suggests possible mass effect, prolapse, or increased intra-abdominal pressure)
• Age 82 years (high-risk population for malignancy and complicated diverticular disease)
• No urinary symptoms (does not exclude bladder pathology)

...creates a clinical picture that demands immediate structural evaluation. 2

Critical Differential Diagnoses to Exclude

Colorectal Malignancy (Most Dangerous)

• Perforated or obstructing colon cancer can mimic diverticulitis and presents with chronic lower abdominal pain in elderly patients. 1
• CT findings that favor cancer over benign disease include pericolonic lymphadenopathy >1 cm in short-axis diameter with or without pericolonic edema. 1
• The 3-month duration makes malignancy a leading concern—chronic symptoms are atypical for acute diverticulitis but consistent with slowly progressive tumor growth or partial obstruction. 2

Complicated Diverticular Disease

• Only 50% of elderly patients with acute left colonic diverticulitis present with lower quadrant pain, only 17% have fever, and 43% lack leukocytosis, making clinical diagnosis unreliable. 2
• Elderly patients are more likely to present with complicated diverticulitis requiring urgent surgery compared to younger populations. 3
• CT with IV contrast achieves 98–99% sensitivity and 99–100% specificity for detecting diverticulitis and its complications (abscess, perforation, fistula). 1, 3

Bladder Pathology

• Bladder cancer, chronic cystitis, or bladder outlet obstruction can present with lower abdominal pain without overt urinary symptoms, particularly in elderly males with prostatic disease. 1
• CT cystography or dedicated pelvic imaging will identify bladder masses, wall thickening, or obstruction. 1

Large Bowel Obstruction

• Colorectal cancer accounts for 60% of large bowel obstructions, and sigmoid volvulus represents 15–20%. 3
• Pain worsening with standing could reflect intermittent obstruction or increased mesenteric tension. 3
• Inability to pass gas or stool, combined with abdominal distension, is present in 90% of large bowel obstructions—ask specifically about these symptoms. 1

Mesenteric Ischemia

• Pain out of proportion to physical examination findings is the hallmark of acute mesenteric ischemia and demands immediate imaging, particularly in elderly patients with cardiovascular disease or atrial fibrillation. 3
• Chronic mesenteric ischemia presents with postprandial pain and weight loss—ask about food fear and unintentional weight loss. 3

Specific Imaging Protocol

Order CT abdomen and pelvis with intravenous contrast (American College of Radiology rating 8/9, "usually appropriate"). 1

Why IV Contrast is Essential

• IV contrast improves characterization of bowel wall pathology, pericolic abnormalities, vascular pathology, and intra-abdominal fluid collections. 1
• Contrast-enhanced CT identifies alternative diagnoses in approximately 49% of patients whose pain is non-localized. 1
• CT findings guide subsequent treatment decisions—medical management, percutaneous drainage, or surgical intervention. 1

If IV Contrast is Contraindicated

• In patients with severe acute or chronic kidney disease or contrast allergy, use ultrasound, MRI, or CT without IV contrast as alternative approaches, though these are less accurate for detecting abscesses and vascular pathology. 2

Mandatory Pre-Imaging Laboratory Workup

Before ordering CT, obtain:

• Complete blood count (leukocytosis suggests bowel ischemia and is a predictor of transmural necrosis and mortality). 3
• C-reactive protein (CRP >170 mg/L predicts severe diverticulitis with 87.5% sensitivity and 91.1% specificity; also useful for assessing severity of acute abdomen). 3
• Serum creatinine (to assess renal function before IV contrast administration). 2
• Serum lactate (marker of poor tissue perfusion; critical for bowel ischemia and septic shock). 3
• Serum albumin and ferritin (assess nutritional status and chronic inflammation). 3

Critical Physical Examination Findings to Document Now

• Digital rectal examination is mandatory to detect rectal mass, fecal impaction, blood, or rectal prolapse. 3
• Examination of all hernia orifices to detect incarcerated hernias. 3
• Assess for peritoneal signs (guarding, rebound tenderness, rigidity)—their presence mandates immediate surgical consultation. 1, 3
• Abdominal rigidity indicates perforated viscus requiring immediate surgical consultation. 3
• Vital signs monitoring for tachycardia, fever, or hypotension (signs of sepsis or shock). 3

What to Do After CT Results

If CT Shows Uncomplicated Diverticulosis or Mild Diverticulitis

• Conservative management without antibiotics is appropriate for immunocompetent elderly patients with uncomplicated diverticulitis (WSES stage 0). 2
• Antibiotic therapy for maximum 7 days only if the patient is immunocompromised or has sepsis-related organ failures. 2

If CT Shows Complicated Diverticulitis with Abscess

• Abscess <4 cm: antibiotic therapy alone for 7 days without drainage. 2
• Abscess ≥4 cm: percutaneous drainage plus antibiotics for 4 days if the patient is hemodynamically stable. 2
• Recommended antibiotic regimen: Ertapenem 1 g q24h or Eravacycline 1 mg/kg q12h for community-acquired infection. 1

If CT Shows Perforation, Free Air, or Peritonitis

• Immediate surgical consultation for emergency laparotomy. 2, 3
• Hemodynamic instability despite resuscitation requires immediate surgical consultation. 3

If CT Shows Colorectal Mass or Suspicious Lymphadenopathy

• Colonoscopy is indicated when CT shows abscess, perforation, fistula, abnormal lymph nodes, or a luminal mass. 1
• Do not perform routine colonoscopy after uncomplicated, CT-confirmed diverticulitis unless age-appropriate screening is due or concerning CT features are present. 1

If CT Shows Bladder Pathology

• Urology referral for cystoscopy and biopsy if bladder mass is identified. 1

If CT is Negative for Structural Pathology

• Functional bowel disorder becomes the most likely diagnosis only after comprehensive exclusion of structural pathology by CT and colonoscopy. 4
• Refer to gastroenterology for colonoscopy if not recently performed (within 5–10 years), even after negative CT, to ensure thorough evaluation for occult structural disease. 4

Common Pitfalls to Avoid

• Do not assume diverticulitis solely on a history of diverticulosis—alternative pathologies, especially colon cancer, must be excluded. 1
• Do not rely on the absence of urinary symptoms to exclude bladder pathology—bladder cancer and chronic cystitis can present without dysuria or hematuria. 1
• Do not delay imaging to obtain "more history"—elderly patients often have atypical presentations, and time from symptom onset to hospital admission is typically longer in this population. 3
• Do not assume normal vital signs exclude serious pathology—the physical examination can be misleadingly benign, even with catastrophic conditions such as abdominal aortic aneurysm rupture and mesenteric ischemia. 5
• Do not order plain abdominal radiographs as the initial imaging modality—they have only 50–60% diagnostic accuracy for small bowel obstruction and low sensitivity for diverticulitis. 3

Disposition and Follow-Up

• Strong consideration for hospital admission given advanced age, chronic symptoms, and inability to exclude surgical pathology. 3
• If outpatient management is chosen after negative CT, instruct the patient to return immediately for fever, inability to pass gas/stool, severe tenderness with guarding, vomiting, bloody stools, or signs of shock. 1
• Repeat CT is indicated if symptoms persist for more than 2–3 days despite conservative management or if new symptoms develop. 1