Library · Disease
Hydronephrosis
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The kidney makes urine nonstop, and that urine gathers in the collecting system, the set of cavities that take it in before sending it downward. Hydronephrosis is the dilation and distension of that collecting system, and it happens when something obstructs urine outflow below the renal pelvis, the funnel where the kidney empties into the ureter.
What happens next is purely a matter of pressure. With the outlet blocked, hydrostatic pressure inside the collecting system rises, and that pressure is transmitted backward all the way to the glomeruli, the kidney's microscopic filters. As intraglomerular pressure rises, filtration is affected. Urine keeps arriving, the outlet is closed, and the kidney fills from the inside.
How much is lost depends on two things: how long the obstruction lasts and how severe it is. If it drags on, what is left behind is cortical atrophy, meaning thinning of the layer that does the work, and fibrosis, which is scar tissue taking the place of functioning tissue.
In brief
Hydronephrosis is dilation and distension of the renal collecting system caused by obstruction of urine outflow below the renal pelvis.
The obstruction raises hydrostatic pressure in the collecting system, which in turn raises intraglomerular pressure and affects filtration.
Urine keeps arriving, the outlet is closed, and the kidney fills from the inside.
How much kidney function is lost depends on how long and how severe the obstruction is; prolonged obstruction leaves cortical atrophy and fibrosis.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingHydronephrosis and Hydroureter, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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