MRI appearance of a hemorrhagic external hemorrhoid at the anal verge with concomitant low anal fistula: A case report

External hemorrhoids are commonly diagnosed clinically, and their MRI appearance is not routinely emphasized. We report a 69-year-old man who presented with a firm perianal nodule for more than 10 months and worsening anal pain for 10 days. Clinical examination suggested mixed hemorrhoids and a low anal fistula. MRI demonstrated a well-circumscribed nodular lesion at the anal verge with marked central hyperintensity on T1-weighted imaging, a peripheral low-signal rim, iso- to mildly hyperintense signal on T2-weighted imaging, no convincing restricted diffusion, and peripheral ring-like enhancement with central nonenhancement. Maximum-intensity-projection images showed continuity of the enhancing wall with the anal verge and anal mucosal margin. MRI also demonstrated a separate low anal fistula, allowing the fistulous tract and the hemorrhagic anal-margin lesion to be assessed as distinct abnormalities before surgery. Surgery revealed a dark-brown blood clot within the external hemorrhoidal lesion, and histopathology confirmed hemorrhoidal change and fistulous change in the respective specimens. In this individual case, the combination of intrinsic T1 hyperintensity, absence of convincing diffusion restriction, peripheral enhancement with central nonenhancement, and an anal-verge location was concordant with hemorrhagic hemorrhoidal change. These observations should be regarded as case-specific imaging clues rather than a validated diagnostic pattern, but they may be useful when considering the differential diagnosis of painful anal-margin lesions, particularly when anal fistula coexists.