What is the recommended diagnostic work‑up and treatment for a patient with proctitis and markedly elevated fecal calprotectin?

Management of Proctitis with Markedly Elevated Fecal Calprotectin

In a patient with proctitis and markedly elevated fecal calprotectin (>150 mg/g), initiate treatment with mesalamine 1-g suppository once daily as first-line therapy, and perform endoscopic assessment within 3-6 months to confirm diagnosis, assess treatment response, and rule out more extensive disease. 1, 2

Diagnostic Work-Up

Initial Assessment

• Perform flexible sigmoidoscopy or colonoscopy with biopsies to confirm the diagnosis of ulcerative proctitis, establish disease extent, and obtain histological confirmation 1, 3

  • Colonoscopy is preferred initially to accurately determine disease extent, as up to 50% of patients with apparent proctitis will develop more extensive disease over time 4
  • Segmental biopsies throughout the colon are essential, as endoscopic appearance may underestimate true extent, particularly in quiescent disease 4

• Exclude infectious causes before attributing symptoms to inflammatory bowel disease 2

  • Test stool for Clostridioides difficile and other enteric pathogens, as these can elevate fecal calprotectin and mimic IBD 2
  • Fecal calprotectin >150 mg/g may be elevated from non-intestinal sources of infection or inflammation 2

• Obtain baseline laboratory studies including complete blood count, CRP, albumin, and ESR to assess systemic inflammation and rule out severe disease 1, 4

Important Caveat About Fecal Calprotectin in Proctitis

Fecal calprotectin levels are significantly lower in proctitis compared to more extensive disease, even when endoscopically active 5, 6. In endoscopically active proctitis (Mayo Endoscopic Score ≥2), median fecal calprotectin is approximately 440 mg/g compared to 1690 mg/g in pancolitis 6. Therefore, a "markedly elevated" fecal calprotectin in proctitis strongly suggests:

• Active mucosal inflammation requiring treatment 5, 6
• Possible underestimation of disease extent—the inflammation may extend beyond the rectum 4, 5

Treatment Approach

First-Line Therapy

Start mesalamine 1-g suppository once daily as the preferred initial treatment for mild to moderately active proctitis 1

• Suppositories are superior to enemas or foam for proctitis as they better target rectal inflammation and are better tolerated 1
• Topical mesalamine is more effective than topical steroids for proctitis 1
• No dose-response benefit exists above 1 g daily for topical therapy 1

Combination Therapy for Enhanced Efficacy

Consider combining topical mesalamine with oral mesalamine (or topical steroids if needed) for improved response rates 1

• Combination therapy is more effective than monotherapy for inducing remission 1
• This approach is particularly appropriate given the markedly elevated fecal calprotectin suggesting significant inflammation

Refractory Disease Management

If symptoms persist after 8-12 weeks of optimized topical and oral mesalamine therapy, escalate to systemic steroids, immunosuppressants, or biologics 1

• Anti-TNF agents are the preferred first-line advanced therapy after conventional treatment failure in proctitis 7
• However, clinicians are often more reluctant to initiate advanced therapies in isolated proctitis compared to more extensive disease, though this may not be evidence-based 7

Monitoring Strategy

Short-Term Monitoring (First 3 Months)

Assess clinical activity within 3 months of treatment initiation using symptom assessment and repeat fecal calprotectin 7

• Fecal calprotectin should be measured to monitor treatment response 2, 3
• In patients achieving symptomatic remission, fecal calprotectin <50 mg/g is preferred over <150 mg/g to detect endoscopic improvement (Mayo Endoscopic Score 0 or 1) 2

Endoscopic Reassessment

Perform endoscopic evaluation 3-6 months after treatment initiation to assess mucosal healing 3, 7

• Flexible sigmoidoscopy is adequate for assessing disease activity in most UC patients 3
• Endoscopic assessment is essential because fecal calprotectin, while reliable for mucosal healing across disease extents, shows decreased correlation with endoscopic findings specifically in proctitis 5
• The fecal immunochemical test for hemoglobin may be superior to fecal calprotectin for discriminating Mayo Endoscopic Score 0 in proctitis patients 5

Long-Term Monitoring

For patients in clinical remission, perform proactive monitoring every 6-12 months using patient-reported outcomes and objective markers (fecal calprotectin, CRP) 8

• If fecal calprotectin remains elevated (>150 mg/g) despite symptomatic remission, perform endoscopic assessment rather than empiric treatment adjustment 2
• Alternatively, repeat biomarker measurement in 3-6 months may be reasonable before proceeding to endoscopy 2

Key Clinical Pitfalls

Do not assume proctitis will remain limited to the rectum—up to 50% of patients will develop more extensive disease, with 10% ultimately developing extensive colitis 4. Initial colonoscopy with biopsies throughout the colon is essential to establish true disease extent.

Do not rely solely on fecal calprotectin for monitoring proctitis—the correlation between fecal biomarkers and endoscopic findings is lower in proctitis compared to more extensive disease 5. Endoscopic confirmation remains important for treatment decisions.

Do not delay escalation to advanced therapies in truly refractory proctitis—while historically undertreated, refractory proctitis significantly impacts quality of life and may require biologics 1, 7.

1, 2, 3, 2, 4, 8, 7, 5, 6