The measurement of colonic mucosal-submucosal blood flow in man.

1. A method is described for the measurement of colonic mucosal-submucosal blood flow in man, by studying surgically created colostomies. 2. A local radioisotopic clearance technique utilizing a stable preparation of [125I]4-iodoantipyrine is employed. The indicator is injected directly into the colostomy under study and its gamma emission is recorded by a scintillation detector. 3. A radioautographic study was carried out at laparotomy in humans to facilitate the interpretation of the recorded washout curves. This demonstrated that the tracer was cleared from both the mucosa and submucosa throughout the period of study. 4. Mucosal-submucosal blood flow was calculated according to Kety (1949) from the monoexponential clearance curves obtained, and amounted to 31.7 +/- 11 ml./min. 100 g (S.D. of an observation, n = 30). 5. The results from two consecutive measurements in seventeen patients showed that the mean change between first and second readings was not significant (t test). In addition the between-patient variation (12.2) was significantly greater than the within-patient variation (2.6) for consecutive recordings (F test; P less than 0.01). 6. The within-patient between-days variation (12.9; n = 10) was found to be similar to the between-patient variation. 7. It is concluded that the technique permits measurement of local colonic blood flow in man and by consecutive measurements, it may be used to evaluate local changes in blood flow following reflex or pharmacological stimulation.