The objective of this magnetic resonance imaging (MRI) study was to (1) test the validity of the ellipsoid formula for estimating kidney volume using ex vivo and in vivo models and (2) establish a normal range of values for kidney length and volume in patients with no known history of renal disease. The volumes of five excised porcine kidneys were measured by (1) disc-summation method, (2) ellipsoid formula, and (3) water displacement method. In a retrospective, consecutive group of clinically referred patients (n ‫؍‬ 150; 300 kidneys), individual kidney volume and length were calculated by the disc-summation method and by multiplanar reformation of MRI data, respectively. For comparison, kidney volumes also were calculated using the ellipsoid formula in all patients. Renal volume that was obtained by MRI using the disc-summation method was within 5% of the volume that was determined by the water displacement method, independent of the spatial resolution of the MRI technique used. Data from both the in vivo and the ex vivo models revealed that the ellipsoid formula that commonly is used in ultrasonography underestimates renal volume by 17 to 29% compared with the disc-summation method (P < 0.05). As measured by MRI (mean ؎ SD), kidney lengths were 12.4 ؎ 0.9 cm for men and 11.6 ؎ 1.1 cm for women, and kidney volumes were 202 ؎ 36 ml for men and 154 ؎ 33 ml for women. The results from the ex vivo MRI study show that the kidney volume that was obtained using the disc-summation method is within 5% of the true kidney volume as measured by the water displacement method. The ellipsoid formula consistently and significantly underestimates the true kidney volume. The length and the volume of kidneys that are obtained by MRI in patients with no known history of intrinsic renal disease are greater than the commonly quoted reference values that are obtained by ultrasonography.

IntroductionRoutine C4d staining in renal transplantation has stimulated its use in kidney biopsies with glomerulonephritis (GN). Methodical description on staining patterns in the native kidney is not available.MethodsWe retrospectively evaluated C4d staining in formalin-fixed paraffin-embedded sections from 519 native kidney biopsies (bx) with and without glomerular disease.ResultsStrong C4d staining was consistently present in immune-complex GN, including lupus nephritis (LN) (n = 68), membranous GN (n = 24), membranoproliferative glomerulonephritis (MPGN) pattern (n = 22), fibrillary GN (n = 3), and proliferative GN with monoclonal IgG (n = 3). C4d stained all cases of postinfectious GN (n = 7) amyloidosis (n = 20) and C1q GN (n = 3). In contrast, IgA nephropathy (IgAN) (n = 34), was negative in 62% of bx, with the rest staining variably. The E1 Oxford classification score correlated with capillary wall C4d staining (P = 0.05). C4d marked the glomerular and arteriolar lesions in thrombotic microangiopathy (TMA; n = 16), the glomerular sclerotic segments in focal segmental glomerulosclerosis (FSGS; n = 77), and marked areas of necrosis in crescentic GN (n = 21). In diabetic glomerulopathy (n = 70), C4d marked advanced insudative lesions but was negative otherwise. C4d weakly stained the mesangium, or was negative in normal biopsies (n = 13), minimal change disease (MCD; n = 21), thin basement membrane disease (n = 20), Alport (n = 3), IgM nephropathy (n = 2), C3 glomerulopathy (n = 5), acute interstitial nephritis (n = 12), acute tubular necrosis (n = 22), ischemic glomerulopathy/nephrosclerosis (n = 23), and other miscellaneous processes (n = 14). Staining in tubular basement membranes and peritubular capillaries was most common in lupus.ConclusionBased on reliable staining in lupus and membranous GN, C4d staining is potentially useful as a screening and diagnostic tool, if only paraffin-embedded tissue is available. Knowledge of C4d staining patterns in normal and pathological tissues enhances its diagnostic value.

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