Detrusor sphincter dyssynergia syndrome. A new syndrome and its treatment by external sphincter myotomy.

A new syndrome in which there was persistent external anal sphincter contraction on rectal distension is described in 18 patients. 12 were females and 6 males. Average age was 38.3 years. The main complaint was chronic constipation and straining at stool. Rectal evacuation was performed manually or by enemas. Investigations comprised manometric and EMG studies of external anal sphincter. The average number of stools per week was 2.1. Rectal neck pressure recorded normal values at rest and on squeeze. The rectoinhibitory reflex registered high rectal neck pressure on rectal distension [average 136 +/- (SD) 12.3 mm Hg] which was lowered (average 13 +/- 2.2 mm Hg) after pudendal nerve block. External sphincter showed persistent high EMG activity during rectal distension. External sphincter myotomy was performed in 16 patients. Myotomy specimens showed no histologic abnormalities. The patients were followed up for 2-4 years after the operation. The stool frequency approached the normal range, and straining at stool disappeared. Rectal neck pressure during rectal distension dropped to normal values (average 36 +/- 10.3 mm Hg). Control disorders occurred in 2 patients but disappeared within 6 months after myotomy. External sphincter contraction on rectal distension leads to rectal neck obstruction with a resulting constipation and straining at stool. The cause of this contraction is unknown. Myopathy is excluded by the normal muscle integrity as evident from the normal EMG and biopsy findings. A disorder of the reflex arc may be considered.