Is the rectum a conduit or storage organ?

The rectum is claimed to be a conduit; as it receives the stools, the rectoanal inhibitory reflex is evoked and defecation occurs. However, in many healthy subjects, stools could be palpated in the rectum by digital rectal examination (DRE) without the subject feeling the desire to defecate. The purpose of this communication is to study whether the rectum is a conduit or a storage organ. The study comprised 48 healthy volunteers (mean age 38.4 +/- 15.8 SD years; 30 men, 18 women). Number of stools per week was recorded and DRE was carried out followed by air enema radiography. The subjects had a normal stool frequency of 7.8 +/- 1.4 per week. Most of them last defecated a mean of 6.2 +/- 3.4 hours prior to the test. Stools were palpated in the lower rectum by DRE in 31/48 subjects and by radiography in 12/16. DRE correlated with radiologic examination in 9/12 subjects; in 3 of them, DRE revealed an empty rectum while radiography showed stools in the upper rectum. The 17 subjects with an empty rectum had their last defecation 5.2 +/- 3.6 hours before DRE, and the 31 subjects with palpable stools 15.6 +/- 12.9 hours. In conclusion, the rectum might be considered not simply as a conduit for stools but also as a storage organ. This occurs when it receives from the sigmoid colon an amount of stools too small to evoke the defecation reflex, or when this reflex is neglected due to unfavorable circumstances of defecation.