How does the physiologic response to bilateral obstruction differ from unilateral obstruction?
In unilateral ureteral obstruction, the renin release from the obstructed kidney causes a compensatory increase in kidney blood flow and GFR in the contralateral kidney.
Because the contralateral kidney provides compensatory function, there is little change to total GFR, urine output, electrolyte levels, or serum creatinine.
In bilateral ureteral obstruction, there is no compensation by the contralateral kidney. Thus there can be dramatic decreases in GFR, which is often associated with oliguria, electrolyte abnormalities, creatinine elevation, and fluid retention.
Bilateral obstruction can also result in hypertension. In acute bilateral obstruction, hypertension is caused by elevated renin levels. In chronic bilateral obstruction, hypertension is secondary to fluid overload.