What is the appropriate workup and management for a patient with left-sided abdominal pain despite a normal colonoscopy?

Workup and Management of Left-Sided Abdominal Pain with Normal Colonoscopy

Initial Diagnostic Approach

Obtain CT abdomen and pelvis with IV contrast as the primary diagnostic test to identify the underlying cause of persistent left-sided pain. 1 CT imaging provides 98-99% sensitivity and 99-100% specificity for detecting common causes of left lower quadrant pain including diverticulitis, colitis, inflammatory bowel disease, epiploic appendagitis, and bowel obstruction. 2, 3

Key Imaging Considerations

• CT with contrast is highly sensitive for detecting small quantities of extraluminal air, bowel wall pathology, pericolic abnormalities, and fluid collections that may have been missed on colonoscopy. 1
• CT without contrast may be appropriate when IV contrast is contraindicated, with similar accuracy to contrast-enhanced CT in elderly patients. 1
• Ultrasound directed at the area of maximal pain can reduce unnecessary CT examinations in selected patients. 1

Laboratory Evaluation

• Obtain complete blood count to assess for leukocytosis (>15 × 10⁹ cells/L), which indicates infection or inflammation. 1
• Measure C-reactive protein, as levels >140 mg/L suggest significant inflammatory disease. 2
• Fecal calprotectin testing can differentiate symptomatic uncomplicated diverticular disease from IBS-like symptoms in patients with known diverticulosis—positive in 64.3% of symptomatic diverticular disease versus 0% in IBS-like symptoms. 4

Differential Diagnosis Based on CT Findings

If CT Shows Diverticulitis

• Complicated diverticulitis (abscess, phlegmon, fistula, perforation) requires colonoscopy 6-8 weeks after symptom resolution to exclude colorectal cancer, which has a 6-fold higher prevalence (1.6%) in complicated versus uncomplicated disease. 2
• Uncomplicated diverticulitis in patients up-to-date with CRC screening does not require additional colonoscopy beyond routine screening intervals. 2

If CT Shows Alternative Diagnoses

• Primary epiploic appendagitis presents with focal left lower quadrant tenderness (82.1%), an oval fatty mass with hyperattenuated ring sign on CT (89.3%), and typically lacks fever, rebound tenderness, or leukocytosis. 5, 6
• Colonic diverticulitis presents with more diffuse left-sided tenderness (52%), fever (40%), rebound tenderness (52%), and leukocytosis (52%). 5
• Renal colic, urinary tract infection, gynecologic disorders, perforated carcinoma, or inflammatory bowel disease should be considered based on CT findings. 6

Management Based on Diagnosis

For Symptomatic Uncomplicated Diverticular Disease (SUDD)

• Severe and prolonged left lower-abdominal pain (≥24 consecutive hours) with positive fecal calprotectin characterizes SUDD and differentiates it from IBS. 4
• Conservative management with high-fiber diet (>22.1 g/day), regular vigorous physical activity, maintaining BMI 18-25 kg/m², and smoking cessation reduces recurrence risk. 7, 3
• Low-to-moderate dose tricyclic antidepressants may address visceral hypersensitivity in patients with chronic post-diverticulitis pain without ongoing inflammation. 7

For Epiploic Appendagitis

• Conservative management with NSAIDs for pain control is appropriate, as this is a self-limited condition. 5, 6

For Persistent Pain Without Clear Diagnosis

• Perform both repeat CT imaging and lower endoscopy to exclude ongoing inflammation, stricture, fistula, or alternative diagnoses such as ischemic colitis, inflammatory bowel disease, or malignancy. 7
• Consider diagnostic nerve blocks to determine if pain is peripheral, central, or psychogenic in origin. 1

Critical Pitfalls to Avoid

• Do not assume normal colonoscopy excludes all pathology—colonoscopy cannot visualize extraluminal structures, mesenteric abnormalities, or early diverticulitis. 2, 1
• Do not overlook the possibility of colorectal cancer mimicking diverticulitis, especially when CT shows pericolonic lymphadenopathy >1 cm or absence of mesenteric edema. 2
• Do not restrict nuts, corn, popcorn, or small-seeded fruits, as these are not associated with increased diverticulitis risk. 7, 3
• Approximately 45% of patients report ongoing abdominal pain at 1-year follow-up after acute diverticulitis, usually due to visceral hypersensitivity rather than ongoing inflammation—reassurance and evaluation are needed before attributing symptoms to recurrent disease. 7