Design, setting, participants & measurements: The authors describe six patients with clinical and pathologic findings suggesting a secondary form of FSGS, in whom a history of prematurity and very LBW was obtained. No other known causes of secondary FSGS were identified.

Results: The cohort consisted of two women and four men with a mean age of 32 yr. Patients were born at 22 to 30 wk gestation with mean birth weight of 1054 g (range 450 to 1420 g). Mean 24-h urine protein was 3.3 g/d (range 1.3 to 6.0 g/d), mean creatinine clearance 89 cc/min (range 71 to 132 cc/min), mean creatinine 1.2 mg/dl (range 0.9 to 1.5 mg/dl), and mean serum albumin 4.1 g/dl (range 3.4 to 4.8 g/dl). No patient had full nephrotic syndrome. Renal biopsy revealed FSGS involving a minority (mean 8.8%) of glomeruli, with a predominance of perihilar lesions of sclerosis (five of six patients), glomerulomegaly (all six patients), and only mild foot process effacement (mean 32%), all features typical of postadaptive FSGS.

Conclusions: Our findings support that very LBW and prematurity promote the development of secondary FSGS. Because birth history is often not obtained by adult nephrologists, this risk factor is likely to be underrecognized.

Design, setting, participants, & measurements: GFR was measured by sampling plasma 12 times over 5 h in 56 patients with CKD (mean age 64 yr, 98% men, 79% Caucasian, 34% diabetics, estimated GFR 31.8 ± 14.2 ml/min/1.73 m²). In a subset of 12 patients we measured GFR by sampling plasma 17 times over 10 h.

Results: Short sampling intervals considerably overestimated GFR measured using total plasma iothalamate clearance, especially in larger patients. In the higher estimated GFR group (>30 ml/min/1.73m²), the 5-h GFR was 17% higher and 2-h GFR 54% higher compared with the 10-h GFR, which averaged 40.3 ml/min/1.73 m². In the lower estimated GFR group (<30 ml/min/1.73m²), the 5-h GFR was 36% higher and 2-h GFR 126% higher compared with the 10-h GFR, which averaged 22.2 ml/min/1.73 m². Short sampling duration also reduced the precision of the estimated GFR from 1.67% for 10-h GFR, to 3.48% for 5-h GFR, and to 7.07% for 2-h GFR.

Conclusions: GFR measured over a longer duration with multiple plasma samples spanning the distribution and elimination phases may improve precision and provide a better measure of renal function.