Small bowel manometry: short or long recording sessions?

The study of small bowel motility in humans is commonly done by one of two techniques: short-term recording in a stationary patient or long-term recording in an ambulatory patient. To compare the diagnostic yield of short- and long-term manometric studies of small intestinal motility, we reviewed all prolonged records performed in our center over the years. Long-term studies that included less than 6 hr of recording during fasting or less than 5 hr during sleep and short-term studies using the perfused tube technique were excluded, leaving 91/121 tracings suitable for review. We analyzed the first 3 hr of the fasting period and the first 2 hr of the postprandial period on one occasion and the whole tracing on another; the fasting, postprandial and sleep period were analyzed separately. This allowed us to compare short and long recording sessions in the same patient. The two analyses agreed in 81/91 of the cases. In 7/10 patients a study was diagnosed as abnormal in the short recording but was considered normal after review of the long recording, while the opposite occurred in the remaining three. Periods of sleep and fasting contributed similarly to the change in diagnosis. In another 6 patients with equivocal abnormalities during the short period, the long period helped to establish the diagnosis of normality with confidence. Most of the improvement in the long-term study came from extension of the studies during fasting to 6-7 hr from 3 hr. Long-term records of small bowel motility, including study during sleep enhance the diagnostic accuracy of the test. Accuracy can be improved also simply by prolonging the recording during fasting.