Clinical Features of Tuberculous Versus Crohn's Anal Fistulas, in Korea

Background and Aims: In Western countries, tuberculous anal fistula may not be an issue because tuberculosis [TB] is not common, and this is a very rare form of extrapulmonary manifestation of TB. However in TB-endemic countries, careful diagnostic differentiation is required because the clinical features of TB anal fistula and Crohn's disease [CD] anal fistula are similar, with distinguishing features remaining unclear. We aimed to analyse the clinical features of TB versus CD anal fistulas. Method: Among 13872 patients who underwent anal fistula surgery from 2003 to 2014, 87 patients with TB fistulas and 116 patients with CD fistulas were included. Data on the annual incidence of TB and CD, as well as the clinical, pathological, ultrasonographic, colonoscopic and surgical data were analysed. Results: Compared with CD, the TB group was older [median: 37 vs 22 years] and underlying chronic illness was more common [20.3% vs 2.6%]. In the TB group, 46 patients [59.7%] showed active or inactive pulmonary TB, and acid-fast bacilli and caseating granuloma were found in 56.3% and 62.1%, respectively. During colonoscopy, mucosal lesions were observed more frequently in CD [96.9% vs 16.9%]. Conclusions: TB anal fistula is clinically very similar to CD anal fistula. In Korea, the incidence of CD anal fistula has recently increased in prevalence, whereas the prevalence of TB anal fistula is decreasing but is still persistent. We recommend that clinicians should prepare for a possibility of TB as well as CD anal fistula in TB-endemic countries including Korea.