Anorectal opportunistic diseases in human immunodeficiency virus/acquired immunodeficiency syndrome patients: spectrum of cross-sectional imaging findings.

Patients infected with the human immunodeficiency virus, particularly male homosexuals, are prone to develop disorders involving the anorectal and perineal structures. Cross-sectional imaging techniques, such as multidetector computed tomography with multiplanar reformations and magnetic resonance imaging performed with phased-array coils, are increasingly adopted to detect and stage infectious and neoplastic diseases, and to assess posttreatment modifications. Pyogenic perianal sepsis may be usefully investigated with imaging, particularly to assess the presence and topography of abscess collections to allow a correct surgical choice. Rectal inflammatory involvement is frequently detected during intestinal opportunistic infections, such as cytomegalovirus, pseudomembranous, and amebic colitides, including primary and secondary imaging signs consistent with proctocolitis. Anal carcinoma and intestinal lymphoma are increasingly diagnosed; therefore, special attention should be paid to the identification of solid tissue consistent with tumor; furthermore, MRI provides optimal staging and posttreatment follow-up of neoplastic lesions. Knowledge of this varied spectrum of anorectal and perineal opportunistic abnormalities and their imaging appearances should help radiologists to propose appropriate differential diagnoses, suggest correlation with laboratory and microbiological assays or biopsy, and reliably assess therapeutic response.