Effect of Cooling on the Rectal Tone

<i>Objectives:</i> It has been claimed that recognizable organized sensory nerve endings could not be detected in the rectal wall. Hence the identification of cold receptors sensitive to cold temperature in the rectal wall has so far not been reported in the literature. We investigated the hypothesis that rectal cooling effected an increase of the rectal tone. <i>Methods:</i> Twenty-eight healthy volunteers (18 men, 10 women, age 26–50 years) were studied. The rectal wall tone was assessed by the barostat system during infusion of normal saline at 30°C and at 4°C. The test was repeated after rectal anesthetization with lidocaine. <i>Results:</i> The rectal tone on rectal saline infusion showed no response at a temperature of 30°C, and asignificant increase (p < 0.05) at 4°C. The latency measured by the switch-inflation apparatus recorded a mean of 15.3 ± 1.2 ms. Iced saline infusion into the anesthetized rectum effected no significant change in the rectal tone. <i>Conclusions:</i> The current study has demonstrated that rectal infusion of iced saline produced an increase of the rectal tone. This effect is suggested to be a reflex and mediated through the ‘rectal cooling reflex’. The reflex is suggested to act as an investigative tool in the diagnosis of rectal motile disorders provided further studies are performed.