Role of transperineal ultrasonography (TPUS) in follow up of IBD patients with perianal disease

Introduction: The assessment of perianal disease is very important in IBD patients. In clinical practice, the outcome of medical or surgical treatment is evaluated mainly on the basis of physicians' subjective judgment. However, some objective scores for evaluating the efficacy of treatment have been proposed such as the Fistula Drainage Assessment (FDA) and the Perianal Disease Activity Index (PDAI). Specifically, FDA focuses on fistula drainage: a significant clinical improvement is present when at least 50% of fistulae is cured whereas complete remission is achieved when all fistulae are closed at the digital pressure in two consecutive visits. However, both FDA and PDAI give no information on the anatomical evolution of fistulae during medical treatment. Moreover, physical examination of the perineum is generally unable to differentiate between simple and complex fistulae according to the AGA classification although this information is crucial to assess the relationship between fistulae and anal sphincters and to determine the clinical outcome of IBD patients with perianal disease.

Nowadays, clinical evaluation combined with MRI findings is considered ad the gold standard method to evaluate the treatment outcome of the perianal disease. In fact, several studies have shown that MRI is useful in the pre-operatory setting to determine the severity of fistulizing disease and could be used to study how fistulae evolve during medical treatment (1 – 3). Nevertheless, the use of MRI seems to be unfeasible in clinical practice especially during long term antibiotic therapy for active perianal disease.

Recently, TPUS has been recognized as accurate as MRI not only in diagnosis and staging the perianal disease (4.5), but also in predicting the outcome of the disease during infliximab treatment (6).

Purpose: The aim of this retrospective single-center study was to evaluate the accuracy of TPUS in IBD patients with active perianal disease during antibiotic treatment.

Methods: All IBD patients with active perianal disease referred to our IBD unit for starting antibiotic treatment between January 2014 and December 2015 were included in this study. All enrolled patients underwent both gastroenterological and surgical evaluation. PDAI and FDA scores were calculated. According to Present's study (7), a cut-off value of PDAI ≤5 was chosen to establish the clinical remission after medical treatment. TPUS was performed by an experienced operator. All patients were re-evaluated with the same protocol 30 days after the antibiotic treatment introduction. A Fleiss Kappa test was used to evaluate the agreement between FDA, PDAI and TPUS evaluations.

Results: All IBD patients with active perianal disease referred to our IBD unit for starting antibiotic treatment between January 2014 and December 2015 were included in this study. All enrolled patients underwent both gastroenterological and surgical evaluation. PDAI and FDA scores were calculated. According to Present's study (7), a cut-off value of PDAI ≤5 was chosen to establish the clinical remission after medical treatment. TPUS was performed by an experienced operator. All patients were re-evaluated with the same protocol 30 days after the antibiotic treatment introduction. A Fleiss Kappa test was used to evaluate the agreement between FDA, PDAI and TPUS evaluations.

Conclusion: TPUS is able to accurately evaluate the short-term evolution and predict the outcome of perianal disease after antibiotic treatment. In the future we need to elaborate and validate a score useful for a more objective evaluation of TPUS findings in order to standardize the operators' findings between the IBD units.