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The development of extra efferent vessels (EEV) is a little-known feature of diabetic glomerulopathy. The only previous large study [Min W, Yamanaka N. Three-dimensional analysis of increased vasculature around the glomerular vascular pole in diabetic nephropathy. Virchows Archiv A Pathol Anat 1993; 423:201-7] known to us found that up to 5 EEV per glomerulus (glom) each drained a separate lobule. Most EEV connected to the second- and third-order branches of the afferent arteriole (AA), and drained into peritubular capillaries. Although not so stated, the illustrations suggested that some EEV could be shunts, and thus detrimental to glom function, and possibly glom health. There was no correlation between the unquantitated presence of increased EEV at the vascular pole (VP) and the severity of the major diabetic glomerular (glom) lesions. The authors opined that efferent arteriole (EA) stenosis by insudative lesions (IL) stimulated the formation of EEV. To confirm and extend these findings, we have repeated the study in 18 diabetic cases with mild to severe, but not end-stage, diffuse and nodular lesions (DL and NL), 8 controls, and the 2 normal traumatic nephrectomy cases. Up to 18 EEV per glom were found in diabetic cases along with occasional EEV in controls. EEV contained muscle and were almost identical to the EA in structure. Nearly all EEV connected with efferent glom capillaries at the VP, where they exited the glom through apparently preexisting gaps in the Bowman's capsule and/or glomerular capillary basement membranes (BCBM/GCBM). The EA exited through a similar gap, so the exit of EEV was accomplished without altering the anatomical relationships between the exiting vessels and the components of the VP thought to be important in the control of glom outflow. The largest number of EEV occurred in long-standing T2DM cases with mild to moderate DL and NL. Complete photographic glom reconstructions revealed numerous anastomoses among efferent glom capillaries in normal and diabetic gloms with mild to moderate DL and NL. No disproportionately dilated EEV were seen. The findings just cited confirm that EEV are common and surprisingly numerous in diabetic gloms. They suggest that EEV formation served to preserve glom function, and that EEV could neither shunt nor restrict glom outflow locally. In our opinion, the formation of EEV represents a significant, possibly hemodynamically induced, remodeling of the glom that should be added to the list of changes that occur in diabetes. It is hypothesized that EEV develop because of increased glom inflow, and that the latter may be attributable to AA muscle damage that impairs its contractile ability.

Kidneys from 74 consecutive, primarily non-insulin-dependent diabetics at autopsy and 59 age-, sex, and ethnic group-matched controls were examined qualitatively and semiquantitatively to determine the prevalence and severity of insudative lesions (ILs) and obsolescent glomeruli with (OGcFC) and without (OGsFC) insudative (fibrin cap) lesions. A subset of 25 cases with advanced diabetic changes was examined using serial sections, immunohistochemical stains, and electron microscopy to determine the pathogenesis of ILs and OGcFCs. Insudative lesions consisted of intramural accumulations (hereafter called deposits) of presumably imbibed plasma proteins and lipids within renal arterioles, glomerular capillaries, Bowman's capsule, and proximal convoluted tubules. Insudative lesions in Bowman's capsule are called capsular drop lesions (CDs), in glomerular capillaries they are called fibrin cap lesions (FC), and in afferent and efferent arterioles they are called hyalinized afferent (HA) and hyalinized efferent (HE) arterioles, respectively. All ILs were much more numerous and/or larger in diabetics than in controls. Contrary to previous opinion, CDs and HE arterioles were not specific for diabetes, being present in small numbers in nine (15%) controls. Controls with CD/HE arterioles had far more HA arterioles and focal mesangiolyses (FMs) than those without. Insudative lesions consisted of the well known homogenous eosinophilic deposits (homogenous eosinophilic ILs) and the less familiar foamy, reticulated, and vacuolar deposits (heterogenous lucent ILs). Homogenous eosinophilic ILs were predominant in afferent arterioles and more so in efferent arterioles, and were segregated into globules of varying density with the denser deposits located peripherally. Two types of CDs, which differed sharply in location and composition, were found. The first was mostly homogenous eosinophilic, usually without capsular adhesions and located near the vascular pole close to preglomerular arterioles. The second was mostly heterogenous lucent, located away from the vascular pole, and consistently connected by adhesions to the capillary tuft usually near FMs and/or Kimmelstiel-Wilson (KW) nodules. The latter ILs sometimes extended in continuity along the internal surface of the basement membrane from Bowman's capsule into the proximal convoluted tubule. It was hypothesized that ILs traveled centrifugally through the walls of preglomerular arterioles to form the first type of CD and longitudinally within the walls of afferent arterioles and glomerular capillaries and through adhesions to form the second. Contrary to previous opinion, FCs were consistently intramural. When numerous, FCs were associated with a form of glomerular obsolescence called OGcFC.(ABSTRACT TRUNCATED AT 400 WORDS)

This is a study of quantitative glomerular morphology in 14 normal and 6 long-term diabetic female baboons between 3 and 25 years of age. In the normal female baboon, peripheral glomerular capillary basement membrane thickness increased until around 10 years of age, reached a plateau between 10 and 20 years of age, and possibly decreased at 25 years of age. Mean value for young (3 to 7 years of age) and older (10 to 25 years of age) controls were 266 nm and 329 nm respectively. Fractional volumes of mesangial matrix (8.9%) and mesangial cells (6.8%) were not affected by age. Glomerular basement membrane thickness and the volume of mesangial matrix increased progressively in female baboons with poorly controlled pancreatectomy-induced diabetes, while the volume of mesangial cells remained unchanged. After 106 to 145 months of diabetes, glomerular basement membrane thickness and the volume of mesangial matrix were 558 nm and 18.7% respectively. These values were significantly greater than those of the age-matched controlled (p = less than 0.05). By light and electron microscopy, the normal baboon glomerular morphology, morphometric measurements and changes with age were similar to those in man. The renal changes in diabetic baboons were also similar in morphology and rate of development to those of mild to moderate diffuse diabetic glomerulosclerosis in humans, indicating that the baboon is an ideal model for the long-term study of diabetic glomerulosclerosis. The presence of considerable interanimal variability in the degree of glomerulosclerosis attained after prolonged diabetes suggested that glomerulosclerosis progressed at different rates in these models. The reason for this was not apparent.