The Effect of Chronically Increased Intra-Abdominal Pressure on Rectus Abdominis Muscle Histology an Experimental Study on Rabbits

Background The aim of this study was to specify the histologic response of the rectus abdominis muscle of the rabbit, to the chronically increased intra-abdominal pressure. Materials and Methods Forty-five New Zealand white rabbits were divided into three groups. In all groups, a rubber bag was implanted into the peritoneal cavity. In group A ( n = 15) the bags were kept empty. In group B ( n = 15) the bags were filled with normal saline in order to achieve an intra-abdominal pressure of over 12 mmHg. This pressure was kept at this level for 8 wk. In group C ( n = 15) the intra-abdominal rubber bags were filled with lead covered by silicone, equiponderant to the mean weight of the normal saline insufflated in group B. After 8 wk we took biopsies of the rectus abdominis muscle and counted the proportion of the different types of muscular fibers (type I, IIA, and IIB/X). Results Significant difference was found in the proportion of the three types of muscle fibers. Intra-abdominal hypertension led to an increase in type I fibers ( P = 0.008). No difference was noticed between groups A and C. Conclusions The histologic response to the increased intra-abdominal pressure was an increase in type I muscle fibers. Charging with lead did not cause any significant change in the proportion of muscular fibers.