Hydronephrosis _- Definition, Causes, Pathogenesis, Signs & Symptoms, Diagnosis & Treatment

Hydronephrosis is defined as distention of renal calyces and renal pelvis with urine as a result of urine outflow obstruction.
The other term, hydroureter is defined as distention of the ureter with urine due to obstruction. It could be either unilateral or bilateral.

In both hydronephrosis and hydroureter, obstruction of urine outflow leads to build up and back flow of urine, increasing the pressure inside the ureter. This will ultimately lead to changes in GFR, tubular function, and renal blood flow. GFR declines significantly with hours following acute obstruction.
And the tubular ability to transport ions and dilute urine will be severely impaired. In addition, increased ureteric pressure will lead to pyelovenous and pyelolymphatic back flow.