Mean segmental transit time of radiopaque markers through the right colon, left colon and rectosigmoid areas of adults and children has been calculated form their distribution on consecutive plain films of the abdomen. Overall mean transit does not differ significantly in the large bowel between adults and children. However, there are regional differences within the colon in relation to age. Mean transit time in the right colon is 13.8 hours in adults and 7.7 in children (p less than 0.01). Corresponding values in the left colon are 14.1 and 8.7 hours (p less than 0.02) and, in the rectum, 11 and 12.4 hours (p = NS). The percentage of the mean total large bowel transit time spent in the right colon, left colon and rectosigmoid area are respectively for adults and children 33 +/- 4 and 28 +/- 3 per cent (p = NS); 39 +/- 4 and 32 +/- 4 per cent (p = NS); and 28 +/- 4 and 41 +/- 4 per cent (p less than 0.05), indicating a relative stagnation in the rectosigmoid area of children. These physiologic differences may have implications in diseased states.

Viscoelastic properties of the rectal wall and anal sphincter pressure were studied simultaneously in 25 normal children. During rectal distension for 60 s, with varying volumes of air, the rectal pressure varied as the sum of two exponential functions of the time plus an asymptotic constant. A rectoanal inhibitory reflex was elicited during these distensions. The exponential decrease of the rectal pressure corresponded exactly to the return of the upper anal canal pressure to the resting value in some subjects. In others, the upper anal canal remained relaxed as long as the rectal ampulla was distended, except with smaller volumes. The results obtained may be explained by an analogical rheological linear model.

Anorectal motility was investigated in 146 children with Hirschsprung's disease and 89 normal control subjects. Pressures were recorded in the rectum and anal canal at rest and during rectal distention. The rectoanal inhibitory reflex was absent in all but four patients. Intraluminal rectal pressure was higher than normal (16.5 vs. 14.6 cm H2O, P less than 0.03), with more frequent (41 per cent vs. 18 per cent, P less than 0.01) pressure waves. In the upper anal canal, there were more frequent (62 per cent vs. 18 per cent, P less than 0.001) spontaneous variations of pressure of lower frequency (9.5 vs. 12.8 cycles/min P less than 0.001) and greater amplitude (5.2 vs. 3.6 cm H2O, P less than 0.001) than normal. The rectoanal contractile reflex occurred in 47 per cent of the patients but in only 21 per cent of the control subjects (P less than 0.001). Aganglionosis was associated with the presence of a rectoanal inhibitory reflex in three patients. This study confirms the value of anorectal manometry in diagnosing Hirschsprung's disease in a large group of patients, and demonstrates other abnormalities that may be useful in cases in which histologic and manometric data are in conflict.