Non-epithelial basement membrane thickening in the urinary tract associated with phenacetin abuse

In four cases of capillarosclerosis in the urinary tract associated with analgesic (phenacetin) abuse, the basement membrane (BM) thickening was not confined to the subepithelial capillaries, but was also found around the smooth muscle cells in the luminal part of the tunica muscularis. Electron microscopy confirmed that the changes in the BM around the smooth muscle cells were similar to those seen around capillaries. This non-vascular affection of BM in the urinary tract in patients with phenacetin abuse has not been reported previously. Thus, capillarosclerosis appears to be only part of a BM disorder, that clearly diminishes in intensity with increasing distance from the lumen. It is therefore suggested that the changes are caused by some agent (possibly a metabolite) in the urine diffusing from the lumen into the wall of the urinary tract.