Unilateral hydronephrosis and hypertension: cause or coincidence?

In the present study, the frequency and the mechanism of hypertension associated with unilateral hydronephrosis (UHY) were investigated in 115 patients. Hypertension (blood pressure greater than 140/90 mm Hg) was found in 20% of 101 consecutive patients with UHY. Twenty-six patients with UHY and hypertension were followed for 35 months and the effect of surgery on blood pressure was analyzed. Blood pressure fell from 178 +/- 4/108 +/- 4 to 135 +/- 2/84 +/- 2 mm Hg after surgery. Hypertension was cured in 62%, improved in 19% and unchanged in 19%. In 73% of the cured patients the PRA-ratio was greater than or equal to 1.5, while all unchanged patients had a value of less than 1.5. Hypertensive patients were significantly older than normotensive patients, but did not differ in kidney function, underlying cause of hydronephrosis, incidence of urinary tract infection or frequency of interstitial nephritis. We conclude that in UHY the incidence of hypertension is not particularly high. However, in a substantial number of patients, high blood pressure is reversible by surgery. In most of these patients the renin-angiotensin-aldosterone system seems to play an important role in sustaining high blood pressure, although in some patients other mechanisms might be operative as well. Since the overall incidence of hypertension is not particularly high in UHY, this secondary form of hypertension appears to be rare.