Simple clinical examination predicts complexity of perianal fistula

To investigate the diagnostic value of the distance between external opening of perianal fistula and anal verge and to evaluate its relation to the type of fistula. Preoperative identification of complex fistulae is important for proper planning of treatment.

One hundred and fifteen consecutive patients operated for perianal fistula were studied prospectively. The distance between the external opening and the anal verge was measured. Location of the external opening, demographic and medical history data were correlated with characteristics of the fistulae. Data analysis was performed using the SPSS statistical package. The association between categorical variables was examined using the chi(2)-test or Fisher's exact test for small sample. Comparison of continuous variables between two groups was analysed by t-test.

The mean distance between external opening and anal verge in simple fistulae was 2.8 cm (range 1.5-4.3, SD 0.689) and in complex fistulae it was 4.4 cm (range 3.5-6.0, SD 0.526). This difference was statistically significant -P < 0.0001. Age and previous operations (particularly attempted definitive operations) were also significantly related to the complexity of the fistula. Data concerning location and direction of the fistulous tracts confirm the validity of Goodsall's rule.

Simple preoperative clinical examination may reliably predict the complexity of a perianal fistula. Identification of these patients permits to select the cases that should have specific sophisticated preoperative work-up. The first definitive operation is most important to assure a successful outcome, thus such preoperative triage may also permit selective referral to a specialized colorectal team.