Observations on Intra-Intestinal Pressure with Special Reference to Absorption of Saline

Abstract

Measurement of the absorption of fluid from an isolated fistulous loop of intestine by the use of an ordinary manometer tube is unsatisfactory, since with absorption the manometer level falls progressively, and with it, the intra-intestinal pressure. The intra-intestinal pressure can, however, be maintained at a constant level by a manometer system built on principles similar to that used by White 1 for the measurement of the intracapsular pressure in the kidney. Inserted in a closed loop of small intestine previously prepared, is a rubber catheter, which is encircled close to its eye by an inflatable rubber balloon, which serves as a flange fitting snugly in the fistulous passage through the abdominal muscles and preventing escape of fluid. The catheter is attached by a glass T tube to a long rubber connection, continuous in its turn with a fine glass tube. This glass tube, open at its other end, is kept horizontal at any required level above the loop. The system is filled with physiological saline by syringe through the third limb of the T tube, until the fluid reaches the horizontal glass tube, forming a meniscus there which is brought to a mark near the center of the tube. Movement of the meniscus away from this mark toward the rubber connecting tube indicates absorption of fluid from the system, movement towards the open end of the glass tube indicates secretion by the isolated bowel loop. The amount of fluid added to the system by syringe over a given period to hold the meniscus steady at the mark on the horizontal tube will now allow measurement of the rate of absorption from the intestinal loop. Peristaltic movements of the isolated loop, never very considerable, were greatest with each change in pressure but decreased to a stable level after 10 minutes. No readings were recorded during the first 10 minutes of each pressure period.

The rate of absorption of physiological saline has been measured by this method in 3 dog loops of ileum (8 to 12 inches in length) at various levels of intra-intestinal pressure.