Renal pathology, glomerular number and volume in a West African urban community

Abstract

Background: Low glomerular number and large glomerular volume are hypothesized to be risk factors for hypertensive renal disease in adult life. Reports of human glomerular number are based on studies from developed nations and have found single kidney mean values of approximately 900 000 per kidney with a roughly 8-fold range matched by a similar range in glomerular volume. Glomerular number and volume have never been investigated in people from a developing country.

Methods: This study analysed the pathology of 81 autopsy kidneys from Dakar, Senegal, and determined total glomerular number and mean glomerular volume in 28 of these kidneys using the physical disector/fractionator method.

Results: Total glomerular number ranged 2.6-fold from 536 171 to 1 394 010, with a mean of 925 485 nephrons. The mean glomerular volume was 5.74 microm(3) x 10(6) with a 2.5-fold variation that was strongly and inversely correlated with total glomerular number. Glomerular number was inversely correlated with age, and age-associated increases in arteriosclerosis, cortical fibrosis and glomerulosclerosis were observed. Arteriolar nephrosclerosis was observed in 34% of adults. Mean glomerular number in this Dakar population was similar to that previously reported for people from developed nations, while the range of glomerular number and mean glomerular volume was much narrower.

Conclusions: The frequency of arteriolar nephrosclerosis in these Senegalese adults was high (34%), suggesting that hypertensive kidney disease could contribute to a large burden of future chronic kidney disease in this population. Unusually low glomerular number or large glomerular volume do not appear to provide a basis for this potential burden of kidney disease.

Fig. 1

(a) Relationship between right kidney weight and age. (b) Relationship between body weight and age. (c) Relationship between right kidney weight and body surface area (BSA) (m²). n = 81 subjects in all figures. Individual values are shown together with line of best fit and 95% confidence intervals (shaded area).

Fig. 2

The effect of age on total glomerular number. Individual values are shown together with line of best fit and 95% confidence intervals (shaded area). There is a significant inverse relationship between glomerular number and age (n = 28, r² = 0.27, P = 0.005). The relationship is not quite significant (r² = 0.16, P = 0.08) in adults alone (likely due to small sample size).

Fig. 3

Inverse relationship between total glomerular number and mean glomerular volume in adults (n = 20, r² = 0.38 P = 0.005). Individual values are shown together with line of best fit and 95% confidence intervals (shaded area).

Fig. 4

Photomicrographs of renal pathology in subjects from Dakar (Senegal) in sections stained with PAS (a and b) or Masson's Trichrome (c and d). (a) Arteriosclerosis (intimal thickening of the vessel wall). (b) Focal segmental glomerulosclerosis; arrow indicates the sclerosed region. (c) Sickle cell disease or trait. (d) Glomerular capillary thrombosis (likely dissiminated intravascular coagulation). Scale bars = 50 μm.

Fig. 5

(a) Relationship between arteriosclerosis of compliance arteries and age (n = 81, r = 0.79, P < 0.0001). (b) Relationship between age and glomerulosclerosis (r = 0.55 and P < 0.0001). Individual values are shown together with line of best fit and 95% confidence intervals (shaded area) for all ages in (a) and for subjects aged over 5 years in (b).

Fig. 6

Relationship between percentage of glomerulosclerosis and cortical fibrosis in adult subjects (n = 62, r = 0.68, P < 0.0001). Individual values are shown together with line of best fit and 95% confidence intervals (shaded area) for subjects aged over 5 years.