Chemical Neurolysis in Proctology: A Narrative Review of Intradermal Methylene Blue for Anorectal Disorders

Chronic anorectal disorders, including idiopathic pruritus ani and chronic anal fissure, frequently prove refractory to conservative management, while acute postoperative pain following procedures for anal fistula and hemorrhoidectomy remains a significant clinical hurdle. Perianal infiltration of methylene blue (MB) has emerged as a sophisticated neurolytic adjunct to address these challenges. By selectively targeting superficial sensory nerve terminals, it disrupts the chronic itch-scratch cycle and attenuates persistent pain pathways, providing relief that extends well beyond the duration of standard local anesthetics. This review examines the biochemical mechanisms of MB, along with its evolving clinical indications and refined injection techniques. While MB is a potent tool for achieving prolonged analgesia across these four key pathologies, clinical success necessitates precise delivery into the dermo-epidermal plane. When properly titrated to a 0.2% concentration, MB serves as a safe, cost-effective cornerstone of modern enhanced recovery protocols in proctology, effectively minimizing surgical morbidity and accelerating the return to daily activities.