Tuberculous anal fistulas--prevalence and clinical features in an endemic area

The aim of this study was to determine the prevalence of tuberculosis (TB) in anal fistulas at a referral hospital in Cape Town, and to document the clinical features and course of patients with tuberculous anal fistulas.

This was a prospective study of all patients who underwent surgery for anal fistulas at the Colorectal Surgery Unit at Groote Schuur Hospital, Cape Town, from 2004 to 2006. Tissue was submitted for histopathological examination, Ziehl-Neelsen (ZN) staining and TB culture. The patients with proven TB were followed up until January 2008.

During the 3-year study period, 117 operations were performed on 96 patients. TB was diagnosed in 7 of the 96 patients (7.3%). In 5 of these 7 cases, the diagnosis of TB could be proven on histological examination and ZN staining, while in 2 cases the diagnosis could only be made on TB culture. None of the 7 patients had systemic features suggestive of TB, and only 1 had evidence of TB on a chest radiograph, Five patients were HIV-negative, and 2 declined testing. After a median follow-up of 2 years, 5 of 7 patients had evidence of recurrent or persistent fistulas, despite having completed 6 months of TB treatment.

At a referral hospital in an endemic area, TB was present in 7.3% of anal fistulas. Histopathological examination including ZN staining was inadequate to make the diagnosis in a third of these patients. Tissue from anal fistulas should therefore routinely be sent for TB culture as well as histopathological examination and ZN staining in areas where TB is prevalent.