A Systematic Approach to the Histologic Evaluation of Terminal Ileal Biopsies

BackgroundIleal biopsies represent a critical diagnostic tool in gastroenterological practice, with particular relevance in the evaluation of Crohn's disease (CD). However, the ileal mucosa can harbor numerous nonneoplastic and neoplastic conditions that may clinically and histologically mimic CD. Accurate interpretation requires a nuanced understanding of normal ileal histology and its variants, alongside a structured diagnostic algorithm.ObjectivesTo delineate the spectrum of pathologic processes affecting the ileum and establish a systematic diagnostic approach, while highlighting potential diagnostic pitfalls and intrinsic limitations of biopsy interpretation.MethodsWe conducted a MEDLINE literature review focusing on ileal pathology, supplemented with clinical-pathologic insights derived from institutional experience. Key diagnostic criteria, differential considerations, and evolving concepts were critically analyzed.ResultsThe ileum is implicated in a wide range of conditions beyond CD, including tropical sprue, eosinophilic enteritis, graft-versus-host disease, tuberculosis, and various neoplasms, including metastatic lesions. Drug-induced injuries, particularly those associated with nonsteroidal anti-inflammatory drugs and immunotherapy agents, are increasingly recognized as important differential diagnoses.ConclusionsA systematic histologic evaluation of ileal biopsy specimens-integrated with the patient's clinical presentation, endoscopic findings, and imaging studies-is paramount for accurate diagnosis. This approach minimizes diagnostic errors, particularly when distinguishing between conditions with overlapping features, such as CD and other inflammatory or neoplastic processes. Recognizing histologic variations and adopting a comprehensive diagnostic strategy can significantly improve diagnostic yield and inform appropriate management.