Fecal calprotectin is an accurate noninvasive screening tool for pouchitis

Pouchitis is the most common complication after ileal pouch anal anastomosis (IPAA), yet symptoms are non-specific, and diagnosis typically requires pouchoscopy. Fecal calprotectin (FC) is an established inflammatory bowel disease biomarker, but optimal thresholds and diagnostic performance across distinct pouch phenotypes remain unclear.

We performed an analysis of a prospectively maintained IPAA registry (2022-2025) at Mount Sinai Hospital. Adults with ulcerative colitis who had underwent total proctocolectomy with IPAA and had FC testing within ±90 days of pouchoscopy were included. Phenotypes were categorized as normal pouch (NP), acute pouchitis (AP), chronic pouchitis (CP), or Crohn's disease-like pouch inflammation (CDLPI). FC was compared across phenotypes and tested for associations with endoscopic Pouchitis Disease Activity Index (PDAI) sub-score, histologic activity, and symptoms using non-parametric tests, Spearman correlation, log-linear regression, and receiver operating characteristic analysis.

Among 163 patients, FC differed significantly across pouch phenotypes (P <.01) with a median value of 50.5 µg/g in NP, 244 µg/g in AP, 370.5 µg/g in CP, and 231.5 µg/g in CDLPI. FC distinguished between inflammatory and normal pouches with an area under the curve (AUC) of 0.82, with an optimal threshold of ∼167 µg/g (specificity, 94%). FC correlated significantly with endoscopic PDAI sub-scores (Spearman ρ = 0.45, P <.001), and predicted severe endoscopic activity with an AUC of 0.82 and an optimal cutoff of 280 µg/g.

FC is accurate for detecting and grading pouch inflammation. Thresholds near 167 and 280 µg/g reliably discriminate normal from inflamed pouches and mild from severe endoscopic disease, respectively.