Prevalence of Glomerular Hyperfiltration and Nephromegaly in Normo- and Microalbuminuric Type 2 Diabetic Patients

Abstract

Glomerular hyperfiltration, correlated with nephromegaly, is a frequent finding in type 1 (insulin-dependent) diabetes. In type 2 (non-insulin-dependent) diabetes, very few studies have been performed, and the results have been inconclusive. Glomerular filtration rate (GFR) and kidney volume, using ⁹⁹mTc-DTPA scintigraphy and ultrasonography, respectively, were evaluated in 58 control subjects and 163 type 2 diabetic patients; 79 of whom were normoalbuminuric and 84 microalbuminuric. In the two groups of patients, these parameters did not differ significantly from those of controls, even when hypertensive subjects were excluded. Glomerular hyperfiltration was observed in 10 cases; all were normotensive (9.8%), of whom 7 were normoalbuminuric and 3 microalbuminuric. Nephromegaly was observed in 3 other normotensive microalbuminuric diabetic patients. Hypertensive subjects showed a lower GFR than normotensive patients and control subjects. Multivariate analysis showed a negative correlation between glomerular filtrate and systolic blood pressure (BP) in the overall population of patients and in normo- and microalbuminuric patients taken separately. It is concluded that the relationship between these variables forms a continuum in our type 2 diabetic patients; it may also be important in determining the low prevalence of hyperfiltration and nephromegaly found in our patients, who had BP levels higher than those of controls.

Renal hyperfiltration in type 2 diabetes: effect of age-related decline in glomerular filtration rate

“…The reported prevalence of hyperfiltration varies widely from 6 to 75%, with high rates documented in new-onset diabetes and in certain ethnic populations [2,[7][8][9][10][11][12]22]. The high rates of hyperfiltration in new-onset diabetes may be explained, at least partly, by the acute metabolic effect of hyperglycaemia, as previous studies have demonstrated an association between hyperglycaemia and hyperfiltration as well as nephromegaly [23,24].…”

“…This may be explained by the fact that systolic hypertension, reno-vascular disease, and increased arterial stiffness form a continuum with age in type 2 diabetes and these factors have been previously recognised to have a negative correlation with renal plasma flow [39,40] and with GFR [7,41]. Renal vascular resistance has been shown to be correlated with age in normal subjects [39] and blood flow to the renal cortex appears to be inversely related to renal vascular resistance.…”

“…Definition of hyperfiltration and normofiltration In this study, an age-unadjusted threshold for hyperfiltration was defined arbitrarily as a Bröchner-Mortensen (B-M) corrected GFR of >130 ml min −1 1.73 m −2 based on the definitions used in previous studies [2,6,7,9,11,12,15]. To account for the age-related decline in GFR in our diabetic population, we used an age-adjusted definition for hyperfiltration of GFR >130 ml min −1 1.73 m −2 that was reduced progressively by 1 ml min −1 year −1 after the age of 40.…”

“…In type 1 diabetes, hyperfiltration carries a 53% risk of developing overt nephropathy compared with 5% in normofiltering subjects over a 17-year period [6]. In comparison, information on the prevalence and pathogenic significance of hyperfiltration in type 2 diabetes is inconclusive and controversial, due to (1) difficulties in defining hyperfiltration in this population, (2) the co-existence of non-diabetic renal disease, (3) the diversity of patient characteristics, and (4) the insidious onset of the disease [2,[7][8][9][10][11][12]. Hyperfiltration in type 2 diabetes has been associated with a greater rate of decline in GFR than in normofiltering and non-diabetic control subjects over a 6-year period [13], but this finding is not universal [2].…”

The clinical significance of hyperfiltration in diabetes

“…Estimates of the prevalence of hyperfiltration in type 2 diabetes have varied from 0% [21,22], 6% [23] and 35% to 45% in recently diagnosed patients [12,24,25]. A prevalence of 62% was reported by Vedel [26].…”