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Background. The aim of the study was to evaluate how well a biopsy from one region of a human renal allograft represented biopsies from other regions regarding the renal interstitial tissue assessed by stereology. Furthermore, we wanted to evaluate the reproducibility of the measurements. Methods. Punch biopsies (3 mm) from six regions in each kidney were obtained from seven explanted renal grafts with varying degrees of clinically diagnosed chronic and acute rejection. One kidney, removed for a minor pelvic tumour, served as reference material. Using point counting on PAS-stained sections, the volume fraction of the interstitial tissue per glomerular cortex VV(interstitiumucortex) was estimated. From each kidney, two of the six biopsies were re-evaluated by the same observer. Results. VV(interstitiumucortex) varied from 0.25 to 0.78 between the explanted kidneys vs 0.26 in the reference kidney. Variations within the kidneys were low, expressed by standard deviations (SD) of between 0.04 and 0.06, and coefficients of variation (CV) between 0.06 and 0.22. The SD estimated from repeated measurements was 0.04 and CV was 0.07. Conclusions. Biopsies from one region of the kidney were found to be representative for estimates of interstitial tissue in explanted human kidney grafts, and the degree of reproducibility was high when using point counting, as in the present study.

ity may develop as a consequence of a long-standing diabetic glomerulopathy and might lead to less proBackground. Diabetic nephropathy is associated with renal structural changes involving all of the compart- nounced elevation of albumin excretion. ments. Most characteristic is the diabetic glomerulopa- Key words: diabetic glomerulopathy; glomerular vascuthy. Studies of the histological changes during the early lar pole; juxtaglomerular arterioles; microalbuminuria; phases of nephropathy have included the glomerulopa- neovascularization thy and also the juxtaglomerular structures. Neovascularization, well-known in diabetic retinopathy, has also been observed in the kidney. The present study concerns estimates of frequency of neovasculariz- Introduction ation at the vascular pole region in early stages of diabetic nephropathy. The diabetic angiopathy as first described by Lundbaek Methods. Extra eVerent arterioles at the glomerular [1] aVects the vascular beds all over the body. The vascular pole were detected during measurements of involvement of the smallest blood vessels, the microanthe vascular pole area applying 1-mm serial sections giopathy, is well known in its localization to the retinal through kidney biopsies. It was observed that more and renal capillaries. One special appearance of the than one eVerent arteriole existed occasionally. The diabetic retinopathy is the proliferative stage defined present study was carried out with the aim of estimating by the new vessel formation. the frequency of this phenomenon in diabetic patients Neovascularization at the glomerular vascular pole and in non-diabetic controls, the diabetic patients in diabetic patients has been described a few years ago categorized according to the level of albumin excre- [2]. A very comprehensive study of a few cases includtion rate. ing three-dimensional reconstruction showed elegantly Results. Neovascularization was first observed in IDDM the formation of new vessels connecting the glomerular patients with microalbuminuria. Some of the cases pre- tuft with the interstitial blood vessels. sented the phenomenon in all of the glomeruli studied. The present report deals with registration of the As the examinations of many kidney biopsies continued frequency of this particular neovascularization in insuthe phenomenon was observed also in the non-diabetic lin-dependent diabetic patients (IDDM patients) with control group and in one IDDM patient with normoal- the main focus on patients with microalbuminuria. buminuria. However, the frequency was statistically The observations are based on serial sectioning of highly significantly increased in patients with elevated kidney biopsies. This procedure was established in our albumin-excretion. Within this group a strong correla- laboratory primarily to obtain sampling of several tion between frequency of neovascularization and the levels of glomeruli for electron microscopy for a better severity of diabetic glomerulopathy is seen. estimate of mesangial volume fraction during early Conclusions. The vascular abnormality localized to the stages of nephropathy [3]. Next, the serial sections vascular pole region is observed occasionally in the were used for the estimation of glomerular volume and normal kidney, but the frequency is increased in the vascular pole area [4]. With these procedures patients with diabetic glomerulopathy. The abnormal- examination of many vascular pole regions was per