Infection Evaluation and Management

Clinical Assessment

• Evaluate patients for clinical signs of infection, including fever, tachycardia, tachypnea, localized pain or swelling, as recommended by the World Health Organization 1
• Consider abdominal symptoms, such as pain or tenderness, and investigate with stool cultures, C. difficile testing, and fecal calprotectin, as recommended by the World Journal of Emergency Surgery 2

Laboratory Monitoring

• Monitor CRP response to antibiotic therapy, as CRP should decline within 48-72 hours of effective treatment, according to the American Diabetes Association 3
• Use CRP as a marker of disease activity to assess treatment response in patients with inflammatory bowel disease, as suggested by the American Gastroenterological Association 4
• Fecal calprotectin is the gold standard non-invasive marker for intestinal inflammation, differentiating IBD from functional disorders, monitoring disease activity, predicting relapse and response to therapy, and potentially reducing the need for endoscopic procedures, as recommended by the American Gastroenterological Association 5, 4
• The normal value for CRP is <5 mg/L or <0.5 mg/dL, and for fecal calprotectin is <50 mg/g, as stated by the American Gastroenterological Association 5, 6
• The following table summarizes the clinical interpretation of CRP and ESR results:

Imaging and Endoscopy

• Cross-sectional imaging, such as MR enterography (MRE) or CT, is recommended to detect strictures and extra-luminal complications, with MRE preferred over CT for monitoring Crohn's disease to limit radiation exposure 2, 11, 12
• MRE is excellent for detecting transmural inflammation and extraluminal complications, with similar diagnostic accuracy to CT but without radiation exposure 11, 12
• Ileocolonoscopy with biopsies is the gold standard for assessing disease activity, with flexible sigmoidoscopy usually sufficient in acute severe colitis 13, 12
• MR Enterography (MRE) is the preferred first-line imaging for small bowel assessment, with no radiation exposure and excellent detection of transmural inflammation and extraluminal complications, as recommended by the European Society of Gastrointestinal and Abdominal Radiology 11, 14, 12

Treatment and Management

• Consider statin therapy and aggressive risk factor modification for patients with elevated CRP and cardiovascular risk factors, as recommended by the American Heart Association 15
• For patients with moderate to severe symptoms, active inflammation is confirmed if fecal calprotectin >150 mg/g, elevated CRP, or elevated fecal lactoferrin, and treatment adjustment can proceed without mandatory endoscopic assessment 4
• For patients with mild symptoms, endoscopic assessment is recommended before treatment adjustment if elevated inflammatory markers (fecal calprotectin >150 mg/g, elevated CRP) are present 4
• Treatment outcomes should be monitored with serial examinations, including inflammatory markers, every 4-6 weeks after treatment initiation, as suggested by the Journal of Clinical Oncology guidelines 16

Common Pitfalls and Considerations

• Failing to rule out infectious causes before escalating immunosuppressive therapy can lead to adverse outcomes, and testing for C. difficile and considering CMV in moderate to severe colitis is recommended 17
• Relying solely on symptoms for disease assessment can be misleading, as symptoms may not correlate with objective measures of inflammation, and combining symptoms with biomarkers is recommended for more accurate assessment 4, 11
• Overuse of CT scans in young patients should be avoided, and MRE is preferred for routine monitoring to reduce radiation exposure 11, 12
• Assuming normal CRP rules out active disease can be incorrect, as CRP has low sensitivity in some patients with active disease, and fecal calprotectin is more reliable for detecting intestinal inflammation 4
• Do not dismiss elevated ESR when CRP is normal, as this pattern can occur in several serious conditions, including NVO, tuberculosis, and certain autoimmune diseases, according to the IDSA guidelines 18
• Failing to assess for psychosocial factors that may amplify pain perception is a common pitfall, as noted by the Annals of Oncology and Gut 19, 17
• Premature use of opioids for chronic generalized pain is a common pitfall, as suggested by the Gut 17
• Assuming low CRP rules out bacterial infection is incorrect, as non-infectious causes like obesity can elevate CRP, as stated by the American Heart Association 20 and supported by 21
• Treating CRP itself rather than the underlying cause of inflammation is not recommended, as CRP is a marker rather than a disease, according to the American College of Rheumatology and the American Heart Association 20