Rectal Sensory Testing in Anorectal Disorders: A Critical Review of Neurophysiological and Biomechanical Perspectives

Rectal sensory dysfunction plays a central role in constipation, fecal incontinence, and functional defecatory disorders, yet its physiological basis and clinical interpretation remain not completely established. Advances in neuroanatomy and high-resolution anorectal manometry (HRAM) have reshaped current diagnostic paradigms, prompting reconsideration of the traditional threshold-based definition of rectal hyposensitivity. To provide the current mechanisms of rectal sensitivity measurements with critical analysis, and to show the emerging technological advances that can fill the existing gaps as well as the possibilities in the future. The present narrative review synthesizes emerging evidence on anorectal neurophysiology, HRAM-derived sensory thresholds, biomechanical contributors to rectal perception, and the role of novel technologies, such as translumbosacral magnetic stimulation and endoluminal functional lumen imaging probe (EndoFLIP) (technologies scheduled to arrive in Brazil this year), and the interaction of artificial intelligence (AI). Multicenter HRAM datasets evaluating the clinical significance of isolated abnormal thresholds were critically examined. Rectal sensory thresholds reflect a complex interplay of afferent signaling, rectal wall biomechanics, and cortical processing. Multicenter analyses show that even a single elevated threshold may correlate with symptom severity, especially in women, although using a one-threshold definition. Distinguishing primary afferent dysfunction from biomechanical alterations is crucial, with pressure-volume analysis and emerging technologies offering complementary insights. Sensory biofeedback improves outcomes in true afferent hyposensitivity but is less effective when biomechanical factors predominate. Current evidence supports maintaining the London Classification definition of rectal hyposensitivity (≥ 2 abnormal thresholds), while recognizing that isolated abnormalities may indicate early dysfunction in selected patients. Integrating HRAM findings with biomechanical and neurophysiological metrics may refine diagnostic precision. Future developments may allow a single abnormal parameter to reliably define clinically meaningful rectal hyposensitivity.