Does renal function improve after diagnosis of malignant phase hypertension?

Abstract

The nature of the relationship between high blood pressure and kidney damage is controversial. There is a view that essential non-malignant hypertension does not cause renal damage in patients with normal renal function and no proteinuria at first presentation. In contrast, patients with malignant hypertension (MHT) not due to underlying renal disease often exhibit progressive renal impairment, although there can be a dissociation between short-term changes in renal function and the long-term renal outcome. It has been established that the association of MHT and renal impairment is associated with a grave prognosis. To investigate further the changes in renal function after diagnosis of MHT. We studied the clinical features, renal function and survival of patients on the West Birmingham MHT Register. Patients presenting with no or only mild-to-moderate renal impairment (defined as an initial serum creatinine level < 300 micromol/L) were categorized as group 1 patients. Patients with severely impaired renal function, defined as a serum creatinine level > or = 300 micromol/l at presentation, were categorized as group 2 patients. Patients who subsequently suffered a deterioration in renal function were defined as those whose serum creatinine level had risen at follow-up (group A). Patients with an invariant or improving renal function at follow-up were those whose serum creatinine level neither rose nor fell (group B). Clinical characteristics and survival of patients in group 1 were therefore compared with those of patients in group 2; features of patients in group A were compared with those of patients in group B. We studied a total of 169 patients with MHT [107 men, aged 49.4 +/- 13.3 years (mean +/- SD)]. Of these, 136 (80.5%) patients had an initial serum creatinine level < 300 micromol/l (group 1). After a median follow-up of 53 months (interquartile range 15-103), the serum creatinine level of 56.8% (96 of 169) patients had risen (group A). Patients with MHT with only mild-to-moderate renal impairment at presentation (creatinine level < 300 micromol/l, group 1) had lower serum urea, creatinine and blood pressure levels at follow-up compared with those of patients with initially impaired renal function. Although there was no significant change in follow-up serum urea and creatinine levels compared with initial levels in patients in group 2 (paired Wilcoxon test, NS), there was a significant deterioration in renal function in patients in group 1 (P = 0.001). Group 2 patients had a shorter median survival time than did group 1 patients (15 versus 59 months, Lee-Desu statistic 15.4, P = 0.0001). Patients whose serum creatinine level had risen (group A) had significantly higher initial serum urea and creatinine levels and follow-up blood pressures than did those whose renal function had remained invariant or improved (group B). However, there was no significant difference between the median survival times of patients in groups A and B (51 versus 58 months, Lee-Desu statistic 0.377, P = 0.54). We suggest that renal function continues to deteriorate in some patients with MHT, despite a good degree of control of their blood pressures having been achieved at follow-up. However, the renal function of 16 of the 33 patients with severe renal impairment at presentation either remained invariant or was found to have improved at follow-up. There was no evidence that those cases whose renal function remained invariant were confined to those who had presented with less renal impairment. The severity of MHT at presentation and the amount of renal impairment did not predict the outcome. In contrast the quality of control of the blood pressure that had been obtained at follow-up did predict the outcome. Careful monitoring of renal functioning and effective treatment of the blood pressure is mandatory in patients with MHT.