Abstract
Although systemic hypertension is very common in patients with glomerulonephritis there is a dispute if this alteration is consequence of the glomerulonephritis “per se” or is a consequence of the renal failure secondary to the glomerular lesion. With the aim to analyze the factors associated with systemic hypertension, 196 patients with different forms of nephritis were studied. The systemic arterial pressure was measured by standard sphygmomanometer, renal function was evaluated by the determination of the serum creatinine concentration or creatinine clearance. The diagnosis of the type of glomerulonephritis was made on the basis of an examination of kidney biopsy specimens. The prevalence of arterial hypertension among patients with glomerulonephritis was 62.7%. The hypertensive patients were older (hypertensive = 30.6 ± 12.8; normotensive = 25.4 ± 1.6 years; P = 0.03). The prevalence of arterial hypertension was lower in patients with minimal glomerular lesion (12.5%), though their ages were also lower (18.1 ± 3.6 and 29.1 ± 1.03 years; P = 0.03). Arterial hypertension did not correlate with the serum levels of creatinine and albumin; creatinine clearance and 24-h proteinuria. In conclusion: In the patients with glomerulonephritis, the presence of arterial hypertension was associated with a higher mean age whereas the intensity of proteinuria, the level of renal function or the type of glomerulonephritis was not different between the two groups.
INTRODUCTION
Proteinuria, hematuria, reduced glomerular filtration rate and sodium retention are the most frequent manifestations of glomerulonephritis. Sodium retention, on its turn, manifests itself through two important clinical findings, edema and arterial hypertension.Citation[[1]], Citation[[2]] The prevalence of arterial hypertension in patients with glomerulonephritis is higher than in the general populationCitation[[3]], Citation[[4]] and usually correlates with reduced glomerular filtration rate.Citation[[3]], Citation[[4]], Citation[[5]], Citation[[6]], Citation[[7]], Citation[[8]] Moreover, other factors such as ageCitation[[3]], Citation[[6]], Citation[[7]], Citation[[8]] gender,Citation[[8]] body mass indexCitation[[3]], Citation[[7]], Citation[[8]] and type of glomerulonephritisCitation[[3]], Citation[[4]], Citation[[5]], Citation[[7]] have been reported to be associated with elevated blood pressure in patients with glomerulonephritis.
The objective of this study was to evaluate the frequency of arterial hypertension in the different types of glomerulopathy and determining the associated factors.
PATIENTS AND METHODS
In order to study systemic hypertension in patients with acute or chronic glomerulonephritis the charts of 196 consecutive patients were reviewed. The following clinical and laboratory data obtained on the first visit were used for analyses: age, gender, 24-h urinary protein, serum albumin, creatinine clearance, and serum creatinine and serum urea. Renal biopsy was indicated for the patients with a chronic disease or those with acute nephritis with serum creatinine higher than 2 mg/dL. The patients with acute nephritis characterized by abrupt edema, lasting less than a week, serum creatinine less than 2 mg/dL, and with remission within 4 weeks, were not biopsied. Supine blood pressure was measured with a mercury sphygmomanometer and diastolic blood pressure was recorded at phase V. Hypertension was defined as diastolic blood pressure higher than 90 mmHg. Patients taking antihypertensive drugs were classified as hypertensive. Nephrotic syndrome was defined as proteinuria equal or greater than 3 g/24 h and renal failure as serum creatinine higher than 1.5 mg/dL. Biopsy specimens were examined by light and immunofluorescence and were classified according to World Health Organization criteria.Citation[[9]] Data are expressed as means ± standard error. Means were compared using unpaired monocaudal “t” test and categorical variables (hypertensive/non hypertensive) were compared by χ2 or exact Fisher's test when appropriate. Statistical difference was set at P < 0.05.
RESULTS
The mean age of the 196 studied patients was 28 ± 1.0 years; 109 (56%) were males and 123 (63%) displayed arterial hypertension. Serum creatinine ranged from 0.5 mg/dL to 18.6 mg/dL (mean = 2.07 ± 0.16 mg/dL); 72 patients (36%) presented renal insufficiency (serum creatinine > 1.5 mg/dL) and 36 (18%) had nephrotic syndrome.
The mean diastolic arterial pressure of the group as a whole was 97.4 ± 1.34 mmHg, in the hypertensive group it was 108.8 ± 1.1 mmHg and in the normotensive group it was 78.1 ± 1.2 mmHg. The mean systolic pressure of the 196 patients was 148.4 ± 2.02 mmHg, in hypertensive group it was 163.4 ± 2.1 mmHg and in normotensive group it was 122.9 ± 1.8 mmHg.
Among the patients with arterial hypertension there were 71 male (60%), and among normotensive patients there were 38 (52%) (P > 0.05). The mean age (30.6 ± 1.28 years) of the patients with systemic hypertension was significantly different from that of normotensive group (25.4 ± 1.6 years) (P = 0.01).
No significant difference was observed between the normotensive and hypertensive groups regarding the serum creatinine concentration (hypertensive group = 2.06 ± 0.21 mg/dL; normotensive group = 2.09 ± 0.26 mg/dL), serum urea (hypertensive group = 62.23 ± 4.83 mg/dL; normotensive group = 65.30 ± 7.76 mg/dL), creatinine clearance (hypertensive group = 56.68 ± 3.38 mL/min; hypertensive group = 52.58 ± 4.20 mL/min), frequency of patients with renal insufficiency (hypertensive group = 24%; normotensive group = 18%), 24 h proteinuria (hypertensive group = 4.96 ± 0.48 g; normo-tensive group = 3.97 ± 0.06 g), serum albumin (hypertensive group = 3.16 ± 0.07; normotensive group = 2.92 ± 0.10 g/dL), and presence of nephrotic syndrome (hypertensive group = 45%, normotensive group = 41%).
The prevalence of arterial hypertension among the different types of glomerulonephritis varied between 12% (minimal glomerular lesion) and 90% (focal and segmental glomerulosclerosis). In patients with lupus nephritis, prevalence was intermediary (42%). Statistical analysis revealed that the frequency of arterial hypertension in the patients with minimal glomerular lesion (MCGL) (1 in 8), was significantly different from that observed in the remaining groups (). The only MCGL patient with arterial hypertension was 47 years old, whereas the age of the normotensive subjects varied between 13 and 17 years. Mean age of the group with MCGL (18.1 ± 3.6 years) significantly differed from that observed among the remaining patients of the group (29.1 ± 1.03 years; P = 0.03) ().
Table 1. Main Clinical Data of Normotensive and Hypertensive Groups
Table 2. Distribution of the Patients According to the Type of Glomerulonephritis and Presence of Arterial Hypertension
DISCUSSION
In the population studied, which included patients carrying different types of glomerulonephritis, with a mean age of 28 years, the prevalence of renal insufficiency was low, subjects were considered hypertensive when presenting diastolic blood pressure (DBP) >90 mmHg or when using antihypertensive drugs, and the prevalence of arterial hypertension was 63%.
In the literature, the prevalence of arterial hypertension is reported to range from 23 to 83%Citation[[3]], Citation[[4]], Citation[[5]], Citation[[6]], Citation[[7]], Citation[[8]] probably due to differences among the samples studied and the several different criteria used to define arterial hypertension. Buckelew et al.Citation[[8]] reported their findings in 1795 patients with chronic renal disease, but only 30% of their patients had glomerulonephritis while other investigators studied only those carrying primary glomerulonephritis.Citation[[3]], Citation[[4]], Citation[[5]], Citation[[6]], Citation[[7]] Other differences found among the cases studied by other authors are mean age and prevalence of renal insufficiency (18 to 60%).Citation[[3]], Citation[[4]], Citation[[5]], Citation[[6]], Citation[[7]], Citation[[8]]
The criteria utilized to define arterial hypertension have also differed. Some authors have defined it as DBP >90 mmHgCitation[[7]] and others as DBP > 95 mm HgCitation[[3]], Citation[[4]], Citation[[5]], Citation[[6]] while Buckelew et al.Citation[[8]] considered as hypertensive the patients who were on antihypertensive drugs.
The mean age of the subjects with arterial hypertension in this current work, as well as in the literatureCitation[[3]], Citation[[6]], Citation[[7]], Citation[[8]] was higher than that of the normotensive. In addition to age, other factors have been observed to be associated with essential arterial hypertension. Increased BMI,Citation[[3]], Citation[[7]], Citation[[8]] the male genderCitation[[8]] and black race have been reported to be associated with arterial hypertension in glomerulonephritis. These data suggest that the same mechanisms involved in essential arterial hypertension are important components of hypertension observed in patients with glomerulonephritis.
In the cohort described in the present work, no association between renal insufficiency and arterial hypertension was seen as it has been reported in the literature.Citation[[3]], Citation[[4]], Citation[[5]], Citation[[6]], Citation[[7]], Citation[[8]] The cohort studied was very heterogeneous and the duration of the disease varied much so it is possible that, in these patients, factors other than those usually associated with renal insufficiency played a role in the genesis of arterial hypertension.
The importance of the type of glomerulonephritis in the prevalence of hypertension has been debated in the literature. Some investigators report that patients with mesangiocapillary glomerulonephritisCitation[[3]], Citation[[4]], Citation[[5]], Citation[[6]] or focal and segmental glomerulosclerosisCitation[[4]], Citation[[7]] present a higher frequency of arterial hypertension and that those with minimal glomerular lesionsCitation[[3]], Citation[[5]] present normal arterial pressure more frequently.
Among the cases studied it was observed that the prevalence of hypertension in MCGL patients was lower than among those with other types of glomerulonephritis. However, among the MCGL patients, the mean age was lower than that of the whole cohort. Thus the lower prevalence of arterial hypertension might be due to the lower age rather than the type of glomerulonephritis presented by these patients.
The presence of arterial hypertension and the presence or intensity of proteinuria did not correlate with the albumin serum level, suggesting the alterations in the glomerular basal membrane, which occur in patients with glomerulonephritis, do not affect the genesis of arterial hypertension in these patients.
In conclusion, arterial hypertension in patients with glomerulonephritis is multifactorial and depends on factors such as age and reduction in glomerular filtration.
ACKNOWLEDGMENT
Grants: PIBIC/CNPq.
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