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Role of ultrasonography in evaluation of perianal fistula-A study of 200 cases.

OBJECTIVE
The purpose of this study was to evaluate the role of transrectal, transvaginal, or transperineal ultrasound (US) in evaluation of perianal fistula and to assess the possibility of its role as a first-line investigation for diagnosis and for follow-up as well as a possible substitute for magnetic resonance imaging (MRI).


METHODS
This is a retrospective observational study of 200 patients. All the patients complaining of discharging wound, acute or chronic pain in the perianal region and patients suspected clinically having perianal sinus/fistula, referred for ultrasound evaluation were included in the study. Male patients were scanned by transrectal and transperineal ultrasound, and females by transrectal, transvaginal and transperineal approach. All the patients were followed up with referring surgeon till surgical cure, discharge, and follow-up. Out of total 200 patients, 47 were female and 153 were male patients. Patients were in age range from 16 to 74 years. The path, direction, extent, diameter and internal branching and openings of tracts were recorded. Presence, location and extent of any collection/abscess was also noted.


RESULTS
Fistulae and sinus tracts are seen as hypo to anechoic tracts ranging from 2 to 10 mm in diameter. Air and mixed echogenic moving collection were noted in active tracts. Fibrous tracts were seen as well defined, echogenic structures. Depending on the chronicity and localization, walls of abscesses appeared ill defined or well defined. Findings of transrectal, transvaginal, and transperineal USG were confirmed with intraoperative findings in 200 cases. Out of which 148 patients were followed up clinically till tracts were closed. In 54 patients, there was recurrence that were operated again and followed up with ultrasound. In total 33 had internal collection along the tracts and in the perianal region.


CONCLUSION
Transrectal, transvaginal, and perineal ultrasound together have the potential to reach the sensitivity of MRI. Ultrasound has its greatest advantage in being cheap, easily reproducible and an excellent modality for follow-up.