Straining puborectalis reflex: description and significance of a "new" reflex

The present communication studies the technique and clinical significance of a new reflex, termed straining puborectalis reflex. Nineteen healthy volunteers with an average age of 38.2 years were studied, including ten males and nine females. The intravesical pressure, representative of intra-abdominal pressure, was measured by means of a balloon-tipped catheter introduced into the urinary bladder and connected to a pressure transducer. The electromyographic (EMG) activity of the puborectalis muscle was recorded using a concentric needle electrode inserted into the muscle. The EMG response of the puborectalis muscle to straining at different pressures was recorded. The response to two types of straining--sudden momentary and slow, sustained--was observed. The procedure was repeated in ten subjects after puborectalis infiltration with xylocaine or saline. Sudden straining evoked puborectalis contraction, whereas slow, sustained straining did not. Puborectalis contraction increased with the increase in straining intensity. These results were reproducible. The anesthetized puborectalis did not respond to straining, whereas the saline-infiltrated muscle did. The latency of the reflex was studied. Besides its role as a voluntary continent sphincter, the puborectalis seems to have a role also in the involuntary continence of the pelvic organs through the straining-puborectalis reflex. The muscle contracts on sudden straining, sealing the rectal and vesical necks and thereby preventing fecal or urinary leak. However, it is only on sudden straining that the puborectalis contracts. Slow, sustained straining as occurs during defecation and micturition does not evoke the reflex action. The straining puborectalis reflex is informative and may be incorporated as an investigative tool in patients with fecal and urinary control disorders.