STRUCTURE OF THE LYMPHATIC MICROCIRCULATION IN THE HUMAN URINARY-BLADDER WITH DIFFERENT INTRALUMINAL PRESSURE AND DISTENSION

The localization, morphology and fine structure of initial lymphatic v essels in the mucosa of the empty and distended urinary bladder were s tudied. Endoscopic transurethral biopsies of the empty (collapsed) bla dder showed under light and electron microscopy numerous intramural ly mphatics with a dilated lumen and thin profile. Contacts between endot helial cells were single, overlapping, interlocking, and open while th e perivascular connective tissue was filled by fascicles of collagen f ibers. In the most superficial layer (subepithelial mucosa), lymphatic s were not seen. Biopsies obtained under elevated intraluminal pressur e and distension showed on light and electron microscopy lymphatic ves sels with small lumens characteristically reduced to irregular slits. Endothelial cell contacts were simple or overlapping; open junctions w ere rare. The perivascular connective tissue was dense and collagen an d elastic fibers often abutted one another. These findings support tha t with a distended or expanded urinary bladder, the effect of increase d intraluminal pressure on the superficial (mucosal) layer radially pu lls on the connective tissue that in turn compresses the initial lymph atics thereby restricting lymph transport.