Gallbladder pressure, compliance, and hysteresis during cyclic volume change

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Abstract
The gallbladder has both storage and contractile properties, but its pressure–volume characteristics have not been fully described. We studied gallbladder pressure, compliance, stress relaxation, and the work performed during infusion–withdrawal of fixed volumes of bile at increments of base-line volume under halothane anesthesia in 13 dogs. Two cannulae were inserted in the gallbladder fundus: one for cyclic infusion–withdrawal of bile, and one for pressure monitoring. Following ligation of the cystic duct, the gallbladder was fully aspirated and then filled to successive predetermined base-line volumes (15, 20, 25, 30, or 35 mL). At each base-line volume, 5 mL of bile was infused and withdrawn at 2.47 mL/min. Studies were performed under basal conditions and with cholecystokinin octapeptide (CCK) infusion (10 or 30 ng∙kg−1∙h−1 iv). Pressure was measured at base-line, after infusion, and after withdrawal. Compliance during infusion (ΔV/ΔP) was calculated for each cycle. Stress relaxation was defined as the difference between base-line pressure and any reduction in pressure after withdrawal. Hysteresis, the difference between work of infusion and work of withdrawal, was calculated. The results were such that base-line, end-infusion, and end-withdrawal pressures; work of infusion, work of withdrawal, and hysteresis; and stress relaxation all increased significantly with increases in the predetermined base-line volumes (p < 0.001). Compliance decreased significantly (p < 0.001) with increasing base-line volume. CCK at 10 ng∙kg−1∙h−1 iv had no effect, but infusion of CCK at 30 ng∙kg−1∙h−1 significantly (p < 0.05) increased pressure and work, decreased compliance, and increased stress relaxation compared with controls. Thus, with increasing resting volumes of bile, the gallbladder (1) exhibits increased intraluminal pressure and decreased compliance in response to further filling, but (2) accommodates to increased distension by stress relaxation. In response to CCK there is a decrease in compliance that promotes emptying.

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