What is the management approach for a patient with elevated Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP) levels, Left Lower Quadrant (LLQ) abdominal pain, and a normal Computed Tomography (CT) scan?

Management of Elevated ESR/CRP with LLQ Pain and Normal CT

In a patient with elevated inflammatory markers (ESR/CRP), left lower quadrant pain, and a normal CT scan, you should strongly consider acute uncomplicated diverticulitis that may not yet show CT changes, inflammatory bowel disease (particularly Crohn's disease), or early infectious colitis—and proceed with stool studies (fecal calprotectin, stool cultures, C. difficile toxin) followed by colonoscopy if symptoms persist beyond 48-72 hours. 1, 2

Initial Diagnostic Considerations

The combination of elevated inflammatory markers with LLQ pain but normal CT creates a diagnostic challenge that requires systematic evaluation:

• CRP >50 mg/L with LLQ tenderness has 97% positive predictive value for acute diverticulitis even when CT findings are minimal or absent 1
• Clinical diagnosis of acute left colonic diverticulitis (ALCD) has only 65% positive predictive value without imaging, but the absence of CT findings does not exclude early or mild disease 1
• Normal CT does not rule out inflammatory bowel disease, particularly when CRP is elevated—approximately 20% of active Crohn's disease patients may have normal CRP, but elevated CRP with normal CT warrants further IBD workup 1, 2

Mandatory Initial Workup

Stool Studies (Perform Immediately)

• Order fecal calprotectin, comprehensive stool cultures, and C. difficile toxin testing in all patients with elevated inflammatory markers and abdominal pain 1, 2, 3
• Fecal calprotectin >150 mg/g suggests active inflammation and helps differentiate IBD from non-IBD conditions with 93% sensitivity and 96% specificity 2
• C. difficile testing is mandatory as infection can mimic or trigger IBD symptoms and is an independent risk factor in patients with elevated inflammatory markers 1, 2
• Test for other enteric pathogens (Campylobacter, norovirus) as these can present with elevated inflammatory markers and normal initial CT 2

Interpretation of Inflammatory Markers

• CRP is superior to ESR for detecting acute inflammation in the first 24 hours; ESR becomes more useful after 24 hours and for monitoring chronic conditions 1, 4
• CRP >170 mg/L discriminates severe from mild diverticulitis with 87.5% sensitivity and 91.1% specificity, even when CT appears normal initially 1
• ESR/CRP discordance occurs in 12% of patients—high ESR with low CRP suggests chronic inflammatory conditions like lupus or bone/joint infections, while high CRP with low ESR suggests acute infections (urinary, GI, pulmonary, bloodstream) 5

Management Algorithm Based on Clinical Presentation

If Clinical Picture Suggests Diverticulitis

• Patients with LLQ tenderness, CRP >50 mg/L, and absence of vomiting can be diagnosed clinically with 97% accuracy even with normal CT 1
• Uncomplicated diverticulitis (no CT evidence of abscess, perforation, or distant free air) can be managed without antibiotics if patient has no significant comorbidities or sepsis 1
• Monitor clinically for 48-72 hours; if symptoms worsen or fail to improve, repeat CT may show evolving findings 1
• Consider outpatient management with clear liquid diet and close follow-up if patient is hemodynamically stable 1

If IBD is Suspected

• Proceed with colonoscopy if fecal calprotectin >250 μg/g or if symptoms persist beyond 72 hours despite conservative management 1, 2, 3
• Fecal calprotectin interpretation: <100 μg/g suggests endoscopic remission; 100-250 μg/g indicates intermediate probability; >250 μg/g indicates high likelihood of active inflammation requiring endoscopic evaluation 2
• Do not escalate immunosuppressive therapy without first ruling out C. difficile and other infections 2
• Blood cultures are mandatory if patient is febrile 1, 3

If Infectious Etiology is Suspected

• High CRP with relatively lower ESR strongly suggests acute bacterial infection (urinary tract, GI, pulmonary, or bloodstream) 5
• Obtain blood cultures if temperature >38°C 1, 3
• Supportive care with hydration and analgesics while awaiting stool culture results 3
• Reassess in 2-4 weeks if symptoms resolve with conservative management 3

Critical Pitfalls to Avoid

• Do not rely on normal CT alone to exclude significant pathology—CT has limitations in detecting early diverticulitis, mild IBD, and mesenteric lymphadenitis 1, 3
• Do not assume normal inflammatory markers rule out disease—20% of active Crohn's disease presents with normal CRP 1, 2
• Never delay stool studies including C. difficile testing—this infection is common in patients with elevated inflammatory markers and can mimic IBD flares 1, 2
• Do not use ESR alone for acute conditions—CRP is more sensitive in the first 24 hours 1, 4
• Clinical examination alone is only 40-65% accurate for abdominal pathology; do not withhold further diagnostic workup based solely on normal CT 3
• Do not forget to consider mesenteric lymphadenitis, which may not be apparent on initial CT but can cause elevated inflammatory markers with LLQ pain 3

Follow-up Strategy

• If symptoms improve with conservative management, reassess in 2-4 weeks 3
• If symptoms persist or worsen at 48-72 hours, repeat CT imaging or proceed directly to colonoscopy based on fecal calprotectin results 1, 2
• If fecal calprotectin is elevated (>150 mg/g) and stool cultures are negative, colonoscopy with biopsy is indicated to evaluate for IBD 2, 3