Advances in the evaluation of anorectal function

Functional anorectal diseases such as fecal incontinence and evacuation disorders are common. Reliance on symptoms alone for diagnosis is inadequate and skilled application of anorectal function test is important. There is widespread discordance in understanding and practices among institutions. The International anorectal physiology working group (IAPWG) issued the expert consensus on the advance in the evaluation of anorectal function in 2018 and standardized testing protocol and the London classification for disorders of anorectal function in 2019 (referred to as the "London Consensus"). London Consensus aimed to provide indications, study performance characteristics, clinical utility, advantages and limitations of each anorectal test. Anorectal disorders were classified based on the objective examinations. The IAPWG proposed that anorectal manometry is mainly used to evaluate anal motor function, and that endoanal ultrasonography is suitable for anal structure. Tests of evacuation-balloon expulsion and both barium and magnetic resonance defecography were also included. Simple balloon distension and rectal barostat are tests of rectal sensory and motor function. No single test can fully characterize the causes of fecal incontinence or evacuation disorders. Instead, several tests are used to assess anorectal structure, motor and sensory function. Major findings not seen in healthy controls defined by the classification are as follows:rectoanal areflexia, anal hypotension and hypocontractility, rectal hyposensitivity and hypersensitivity. The London classification for anorectal functional disorders was divided into four parts:the rectoanal inhibitory reflex, anal tone and contractility, anorectal coordination, and rectal sensation. The London Consensus provided framework for clinicians performing and interpreting tests of anorectal function, which is helpful to the standardization of the testing protocol and results.