Anorectal Physiology Following Rectal Resection: A Prospective, Longitudinal Evaluation of Conventional and Vector Volume Manometry
Abstracts
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BACKGROUND: Changes in anorectal physiology patterns following low anterior resection of the rectum are well known and have been studied extensively. However, vector volume manometry (VVM) is a relatively new method in the evaluation of anal sphincter function. The aim of this study was to determine the usefulness of VVM as compared to conventional manometry in the assessment of sphincter function in patients undergoing rectal resection. METHODS: 57 patients (24 females; median age 65) with rectal carcinomas of the lower and middle third were studied prospectively. All patients underwent low anterior resection with total mesorectal excision and primary low colorectal or coloanal anastomosis. Reconstruction was performed using either a coloanal pouch (n=28) or a straight anastomosis (n=29). A protective ileostomy was fashioned in all cases and was closed after a median of 88 (41-196) days. Anorectal physiology was assessed preoperatively, at the time of stoma closure, and three-monthly thereafter for one year. A total of 342 physiology studies (57 patients x 6 measurements)were thus carried out. All manometries were performed using a water-perfused, low-compliance capillary system. A special computer software program transformed the obtained data to calculate the mean resting vector volume (MRVV), the mean squeeze pressure (MSP), and the so called assymetry index (AI). The Wilcoxon test was used for statistical analysis. RESULTS: Conventional mean resting pressure (MRP) dropped from initially 83 to 67 mmHg at the time of stoma closure (P<0.0001) and remained stable at this level throughout the study period. Preoperatively, the MRVV measured 41792 mmHg2cm. This value dropped to 22239 (P<0.0001)and remained at this level. MSP as measured by conventional manometry as well as VVM did not change significantly throughout the study period. The AI increased significantly from a mean preoperative value of 31% to 36% at the time of stoma closure (P<0.001). There were no differences between the two reconstruction methods. CONCLUSION: It is concluded that low anterior resection leads to a decrease in the MRVV and MRP whereas the asymmetry index increases, both indicating significant alterations in anal sphincter physiology. However, in the evaluation of anal sphincter function there was no distict advantage of vector volume assessment over conventional manometry. |
