Echolocation was accomplished by means of "Alok-650" echochamber (Japan) and 3.5 and 5 megahertz transducers. Twenty individuals of the control group and 40 patients who underwent operations on the extrahepatic bile ducts and the gallbladder through S. P. Fedorov's approach were examined. Morphometry was conducted of the linea alba, the broad abdominal muscles, and the rectus abdominis muscles on 5 levels in relaxation and tension of the prelum abdominale muscles. The size of the rectus abdominis muscles in the control group was found to be the same on both sides. Atrophy of the right rectus abdominis muscle was revealed in all patients who were operated on. The spread and depth of the atrophic changes varied. In most cases the muscle was atrophied along its whole length distal to the line of division. The atrophic changes were maximum (22%-62% of the thickness of the symmetric area of the left rectus muscle) for a length of 2-3 cm below the operative incision. In the zone with most marked atrophic changes the muscle loses its property of contraction in functional load of the prelum abdominale.