Perianal pathology beyond fistulizing disease: spectrum of MRI findings and diagnostic pitfalls.

Magnetic resonance imaging (MRI) of the perianal region is frequently performed in the context of fistulizing disease; however, a broad spectrum of non-fistulizing conditions may also affect this region. A wide variety of inflammatory, infectious, vascular, cystic, and neoplastic conditions, as well as anatomical variants and post-surgical changes, may involve the perianal region and often present with overlapping or nonspecific clinical manifestations.MRI, owing to its superior soft tissue contrast and multiplanar capability, plays a central role in the evaluation of perianal pathology. Beyond lesion detection, MRI enables accurate characterization, assessment of disease extent, and differentiation between entities that may be clinically indistinguishable, thereby supporting appropriate therapeutic decision-making. Importantly, perianal abnormalities may also be incidentally detected on pelvic MRI studies performed for unrelated indications. In such cases, unfamiliarity with the full spectrum of perianal findings may represent a source of diagnostic uncertainty, particularly for less experienced radiologists.This review focuses on the MRI appearance of non-fistulizing perianal pathology, emphasizing key imaging features that aid in differential diagnosis across a broad range of benign and malignant conditions. Representative cases from routine clinical practice are presented to illustrate typical and atypical imaging patterns, as well as common diagnostic pitfalls. Selected complementary computed tomography findings are included when relevant.Given the relative infrequency of many perianal conditions, comprehensive knowledge of their MRI features, along with recognition of normal anatomical variants and expected post-treatment appearances, is essential. Such familiarity helps avoid misinterpretation, unnecessary invasive procedures, and delayed diagnosis, ultimately contributing to improved patient management and clinical outcomes.