Evaluation of isotope proctography in constipated subjects.

Twelve patients with longstanding constipation were examined by isotope proctography. Radio-labelled potato mash was inserted rectally to provoke the urge to defaecate and expulsive manoeuvres were recorded using a Gamma-camera. The method illustrated dynamic alterations in the anorectal angles (ARA) which became more acute on 'squeezing', less so on coughing and more obtuse on straining, and maximally so on evacuation. The pelvic floor (PF) movements were consistently upwards on squeezing, less so on coughing, downwards on straining, and maximally so on evacuation. A useful addition was the measurement of the completeness of evacuation and the time involved. The results were comparable to radiological videoproctography (P < 0.01), but the isotope method gave greater discrimination for both ARA and PF movement changes. It also allowed correlations to be made between the pelvic floor descent (P < 0.05) and anorectal angle changes (P < 0.01) with rectal evacuation.