Feasibility and Impact of the Measurement of Extracellular Fluid Volume Simultaneous with GFR by 125I-Iothalamate
The feasibility, validity, and possible applications of the assessment of extracellular fluid volume (ECFV) simultaneous with glomerular filtration rate (GFR) were assessed in a series of validation studies using the constant infusion method of 125I-iothalamate (IOT). In 48 subjects with a broad range of GFR, distribution volume (Vd) of IOT corresponded well with Vd bromide (16.71 ± 3.0 and 16.73 ± 3.2 l, respectively, not significant), with a strong correlation (r = 0.933, P < 0.01) and without systematic deviations. Reproducibility assessment in 25 healthy male subjects showed coefficients of variation of 8.6% of duplicate measurement of Vd IOT during strictly standardized (50 mmol Na+/d) sodium intake. An increase in dietary sodium intake (200 mmol Na+/d) induced a corresponding rise in Vd IOT of 1.11 ± 1.5 l (P < 0.01). In 158 healthy prospective kidney donors, the impact of indexing of GFR to ECFV was analyzed. Age, gender, height, and body surface area (BSA) were determinants of GFR. Whereas GFR, GFR/BSA, and GFR/height were gender-dependent, GFR/ECFV was gender-independent and not related to height or BSA. This supports the potential of normalizing GFR by ECFV. Thus, ECFV can be simultaneously assessed with GFR by the constant infusion method using IOT. After appropriate validation, also other GFR tracers could be used for such a simultaneous estimation, providing a valuable resource of data on ECFV in renal studies and, moreover, allowing GFR to be indexed to the body fluid compartment it clears: the ECFV.
Pauci-immune Crescentic Glomerulonephritis Superimposed on Diabetic Glomerulosclerosis
Background and objectives: Pauci-immune necrotizing and crescentic glomerulonephritis (PNCGN) superimposed on diabetic glomerulosclerosis (DGS) is a rare occurrence. Only limited data on this dual glomerulopathy are available.
Design, setting, participants, & measurements: Twenty-three cases of PNCGN superimposed on DGS were identified from the archives of the Renal Pathology Laboratory of Columbia University. The clinical features, pathologic findings, and outcomes are described.
Results: The majority of patients were white, elderly, and had longstanding diabetes. Patients presented with acute renal failure and an active urine sediment. Antinuclear cytoplasmic autoantibody (ANCA) testing was positive by indirect immunofluorescence in 18 of 22 patients. Sixteen patients had a P-ANCA pattern, 9 of whom underwent further testing and were found to be MPO-ANCA positive by enzyme-linked immunosorbent assay. Among the two patients with C-ANCA by indirect immunofluorescence, enzyme-linked immunosorbent assay was performed in one and revealed PR3-ANCA. Eight patients had extrarenal manifestations of vasculitis, including 6 with pulmonary hemorrhage. At the time of presentation and renal biopsy, 11 patients required hemodialysis. The mean percentages of glomeruli with cellular crescents, fibrous crescents, and necrosis were 24.9, 8.4, and 12.9, respectively. Most patients were treated with cyclophosphamide and prednisone. At a mean follow-up of 14.6 mo (available in 21 patients), 8 patients had died and 8 of the remaining 13 patients had reached end-stage renal disease. Correlates of end-stage renal disease were hemodialysis at presentation and the degree of DGS.
Conclusions: PNCGN may occur superimposed on DGS. The prognosis for this dual glomerulopathy is dismal despite aggressive therapy.
