The role and technique of ambulatory anal manometry

Static anal manometry has proved itself a reliable, reproducible and objective assessment of sphincter function in the investigation of disorders of defecation and continence. Despite this, it gives only very limited information on sphincter function due to the unphysiological nature of its measurement. Technical advances, particularly in digital data storage, have made the recording of anal pressure in a normal environment for prolonged periods of time possible. This offers an improved understanding both of anal activity and the interaction of rectal and anal function in normal and pathological states. In normal subjects anal function during a number of normal physiological events such as micturition, passage of flatus and sleep have been investigated. The sampling reflex has been further defined. Abnormalities of the sampling reflex, rectal activity and slow wave activity in the anal sphincter have been demonstrated in a number of pathological conditions of the anorectum and in the states of incontinence or constipation. Effective ambulatory anal manometry remains in its infancy. With continuing advances it offers exciting possibilities in defining normal or abnormal activity of the anorectum and in the investigation of patients with disorders of defecation and continence.