The usefulness of tests in anorectal disease

Specialized tests of anorectal function are designed to complement but not to replace good clinical examination and sound professional judgement. The different methods of recording pressure changes have advantages and disadvantages. Poor correlation exists when data recorded using miniature balloons are compared with data from microtransducers. Prolonged ambulatory monitoring of anal sphincter and rectal pressure reveal that spontaneous transient episodes of sphincter relaxation are demonstrable in normal subjects. In the investigation of patients with possible traction injury to the pudendal nerve, electromyography and pudendal nerve terminal motor latency data are more precise than manometry data. Good correlation between noninvasive surface electromyography using an intra-anal plug electrode and anal manometry can be attained. Mapping of sphincter defects using concentric needle technology is reasonably accurate but distinctly painful. Dynamic defecography readily demonstrates abnormalities of the rectal wall. The division between what is normal and what is clinically relevant is rather imprecise. Comparative studies of sonographic and electromyographic mapping of sphincter defects give good correlation. Recent application of fine hooked electrodes have demonstrated periodic episodes of smooth muscle and sphincter relaxation. The saline infusion test and balloon expulsion test help to accurately quantify the difficulty patients experience in retention or evacuation, respectively. Perineometry is a simple, rapid, noninvasive method of measuring the extent of perineal descent on straining. Although reproducible, it tends to underestimate the degree of descent when compared with the radiological method but it avoids the use of ionized radiation.