PATHOLOGIC PROCESSES IN HYDRONEPHROSIS

An Experimental Pathologic Study

Abstract

Unilateral hydronephrosis was experimentally induced in 34 Japanese white rabbits by complete ligations of the left ureteropelvic junctions.
Histopathologic studies, intravenous pyelography (IVP) and microangiography (MAG) were performed during the period of 300 experimental days in order to elucidate pathologic processes of hydronephrosis.
The results obtained were as follows.
1) At early stage of hydronephrosis, enlargement of the lumens and atrophy of the epithelial cells appeared in collecting tubules and all nephrons, which were more obvious in distal, convoluted segments and top of Henle's loops than in proximal and straight segments.
2) The epithelial cells showed gradual atrophy with reduction of size and numbers, loss of the polarity in mitochondria and increase in numbers of large lysosomes containing fluid substance. Basement membranes became thick, undulated and were dissociated from epithelial cells. Mesh structures consisted of basement membrane-like materials appeared in dissociated space. In glomeruli, fusion of foot processes of endothelial cells were recognized at the comparatively early stage.
3) After about the 40th experimental day, enlarged lumens of the pelvis became smaller and diminished. The renal tissues which showed progression of atrophy and sclerosis, ultimately fell into such a state as “hydronephrotic contracted kidney”.
Hydronephrosis was thought to be induced by complicated mechanisms of pressure and ischemic atrophy, lowered or lost glomerular filtration and some other factors.