[Applicability and indications of colonoscopic screening for Crohn's disease in patients with fistula-in-ano].

OBJECTIVE

To determine the indications of colonoscopic screening for Crohn's disease in patients with fistula-in-ano.

METHODS

Clinical data of 302 patients with perianal fistula who received colonoscopy examination from January 2010 to December 2013 in the Department of Colorectal Surgery, The Sixth Affiliated Hospital, Sun Yat-sen University were analyzed retrospectively. Parameters for differentiating perianal Crohn's disease from nonspecific fistulae were screened by logistic regression analysis. A regression mathematical model was established for the prediction of perianal Crohn's disease.

RESULTS

A total of 302 patients received colonoscopy examination, and Crohn's disease was found in 16 patients (CD group). Results of univariate analysis on 26 parameters of clinical manifestation, laboratory and radiological examination revealed that differences in 11 clinical parameters between the CD group and non-CD group were statistically significant(all P<0.05), including age, BMI, abdominal pain, non-specific symptoms, multiple fistula, complex anal fistula, neutrophil count, platelet count, activated partial thromboplastin time, hemoglobin concentration and serum albumin concentration. Multivariate analysis revealed that age≤40 years (OR=14.464, 95% CI: 1.143-183.053, P=0.039), BMI<24.0 kg/m2 (OR=8.220, 95% CI:1.005-67.200, P=0.049), abdominal pain (OR=13.148, 95% CI: 1.110-155.774, P=0.041), complex anal fistula (OR=7.056, 95% CI:1.166-42.688, P=0.033) and elevated platelet count (OR=1.012, 95% CI: 1.004-1.0194, P=0.003) were independent risk factors for discovery of Crohn's disease by colonoscopy. Area under the ROC curve of the regression mathematical model based on factors mentioned above was 0.921, indicating that the model was highly predictive. The sensitivity and specificity of this model was 81.3% and 86.7% respectively when the optimal diagnostic cut-off point was established at 0.856.

CONCLUSIONS

Parameters that predict Crohn's disease in patients with perianal fistula include age, BMI, abdominal pain, classification of fistula and platelet count. Colonoscopy is recommended for patients at high risk.