Perianal fistulae and abscesses are debilitating conditions, frequently encountered in clinical practice. Perianal fistulae are classified according to their nature and their anatomical course relative to the anal sphincter complex. This is mandatory for the proper management, since incorrect or inappropriate treatment may lead to irreversible functional consequences and recurrence of the fistula. The main imaging modalities in the assessment of perianal fistulae are transanal ultrasound and magnetic resonance imaging. Transperineal ultrasound has been proposed as an alternative diagnostic tool and as a non-invasive and cheap technique to monitor perianal lesions during treatment. Perineal fistulae can be detected by transperineal ultrasound as hypoechoic tracts, sometimes with air within, between the anus or rectum and the perianal skin or vagina and are correctly classified in most patients.