Comparison of within- and between-subject variation of serum cystatin C and serum creatinine in children aged 2-13 years.

BACKGROUND: Previously, data on both the within-subject (SD(I)) and the between-subject (SD(G)) variation of cystatin C in children has not been reported. Thus, this study aimed to determine this biological variation including analytical variation (SD(A)) of both cystatin C and creatinine to characterize the two analytes as renal function markers in children. METHODS: On two consecutive days blood samples for duplicate analysis of cystatin C (nephelometric, Dade Behring) and creatinine (enzymatic, Roche) were obtained from 30 children (11 females and 19 males, mean age 8.3 range 2-13 years) referred for GFR measurements by (51)Cr-EDTA clearance. For determination of the between-subject variation only children with normal GFR (n=21) were included. Data were adjusted for the well known age-related increase in creatinine. RESULTS: The results are given as coefficients of variation. The within-subject variations were identical for both analytes (6.4%). The between-subject variation was 11.1% for cystatin C and 28.4% for creatinine, though decreasing to 20.1% after adjusting for age. The analytical variation was 1.7% and 2.5% for cystatin C and creatinine, respectively. The index of individuality (IOI = SD(I)/SD(G)) was 0.65 for cystatin C and 0.25 for creatinine, though increasing to 0.36 after age-adjustment. CONCLUSION: The within-subject variation was identical and low for cystatin C and creatinine suggesting that the two are equally suitable for serial monitoring of renal function in children. Based on the low IOI neither analyte, however, seems suitable as a screening marker of renal function in a healthy population of children using population-based reference intervals.

[Aprotinin scintigraphy in amyloidosis]. / Aprotininskintigrafi ved amyloidose.

Amyloidosis is a disease characterized by protein deposition (amyloid) in THE extracellular matrix leading to organ dysfunction and death. New treatment modalities have emphasized the need for accurate and early diagnosis. Aprotinin scintigraphy is a radionuclide imaging technique in which the localisation and extent of amyloid deposits are visualized. It is specific and sensitive in detecting cardiac amyloidosis, which is associated with a poor prognosis. In addition, aprotinin scintigraphy appears to be a useful tool for the monitoring of disease progression and treatment efficacy.

Measuring glomerular filtration rate in children; can cystatin C replace established methods? A review.

Our aim was to evaluate published methods that use serum cystatin C (s-CysC) for measuring glomerular filtration rate (GFR) in children and to discuss advantages and limitations of s-CysC and of established GFR methods. A comprehensive literature review of clinical studies in children evaluating s-CysC or CysC-based formulas and plasma creatinine or creatinine-based formulas against an exogenous reference method using receiver operating characteristics (ROC) curves or Bland-Altman plots is presented. The comparison of s-CysC with plasma creatinine indicated that s-CysC was superior to plasma creatinine in five of 13 studies; four studies showed no difference, and, in four studies, no statistical comparison was made. Comparison of s-CysC and the Schwartz formula showed that s-CysC was superior to the Schwartz formula in two of seven studies; two studies demonstrated no difference, and, in one study, the Schwartz formula was superior to s-CysC. In two studies no statistical comparison was made. The CysC-based prediction equations all had high accuracy but low agreement when compared with a reference GFR, in the range of 30-40% at best. S-CysC is most likely superior to plasma creatinine and at least equal to creatinine-based formulas. CysC-based prediction equations are at least as good as creatinine-based formulas but cannot replace exogenous methods.

Reproducibility and repeatability of differential renal function in 4-week-old piglets.

BACKGROUND: Congenital obstructive renal disease often requires a decision early in the child's life on whether or not surgery is required. Differential renal function (DRF) calculated from the renogram provides important information for the correct decision in this process. A recent publication cast doubt as to the reliability of the renogram in providing DRF in the young child. AIM: To describe the day-to-day variation and reproducibility of the two commonly used agents for estimating DRF. METHODS: Within 1 week, 4-week-old pigs each underwent three examinations with both 99mTc-DTPA and 99mTc-DMSA. DRF values from the 99mTc-DTPA renograms were calculated using both the area under the curve (AUC) and the Rutland-Patlak equation. Day-to-day variations in the results using different background subtraction methods were analysed using the coefficient of variation for each case and the repeatability coefficient for each type of background subtraction. RESULTS: DRF calculated from the 99mTc-DMSA studies showed little variation, with a coefficient of variation of 3.9% in the worst case. The repeatability coefficient calculated from the 99mTc-DTPA studies using the AUC technique combined with the background subtraction method giving the least variation was 14.9% while using the Rutland-Patlak technique with its best background subtraction showed an RC of 9.4%. CONCLUSIONS: The study demonstrates that DRF calculated from 99mTc-DMSA studies have low variability and the results are highly reproducible in immature pigs. The DRF calculated from 99mTc-DTPA renograms failed to show acceptable reproducibility when analysed using either the AUC method or the Rutland-Patlak equation.

Glomerular and tubular function during AT1 receptor blockade in pigs with neonatal induced partial ureteropelvic obstruction.

Previously, we showed that neonatal induced chronic partial unilateral ureteral obstruction (PUUO) of the multipapillary pig kidney decreased glomerular filtration rate (GFR) of the obstructed kidney. We hypothesized that ANG II and nitric oxide (NO) are important for the changes in renal function and in the present study we examined the effects of chronic AT1 receptor blockade using CV-11974 (0.12 mg/h candesartan from age 23 to 30 days) on kidney function development after PUUO was induced in 2-day-old piglets. Moreover, the effect of superimposed acute NO inhibition using N(G)-nitro-l-arginine methyl ester (l-NAME; 15 mg/kg) was examined to identify if this has diagnostic potential. PUUO significantly increased GFR in the nonobstructed contralateral kidney independent of candesartan. In candesartan-treated piglets, the l-NAME-induced GFR reduction seen in normal and nonobstructed kidneys was absent in the partial obstructed kidneys. Urine output and fractional excretion of water were increased from the partial obstructed kidneys. Consistent with this immunohistochemical analyses showed a reduced aquaporin-2 labeling in the collecting duct principal cells. Moreover, renal sodium handling was compromised by PUUO evidenced by an increased fractional excretion of sodium which was enhanced by candesartan treatment. In conclusion, our findings suggest that the counterbalance between AT1 receptor-mediated vasoconstriction and NO-mediated vasodilatation which maintain GFR in normal young porcine kidneys is changed by neonatal induced chronic PUUO. This may have diagnostic potential in children with suspected congenital obstruction. Our results also demonstrate compromised tubular functions in response to chronic PUUO despite preservation of glomerular function.

[Prenatal diagnosed hydronephrosis and other urological anomalies]. / Praenatalt diagnosticeret hydronefrose og andre urologiske anomalier.

By renal ultrasound examination, urological anomalies may be demonstrated in 1-2% of fetuses and in about 0.5% of newborns. Boys have about twice the frequency of girls. Surgical treatment is indicated in about one fourth of these urological anomalies. If all pregnant women in Denmark were to have fetal ultrasound examination of the kidneys and the urinary tract, about 70 children would be born each year with a prenatally diagnosed urological anomaly for which surgical procedure is or will be indicated. This paper provides Danish guidelines for prenatal diagnosis, follow-up and intervention in cases of urological anomalies and guidelines for post-natal diagnosis, follow-up and treatment of these anomalies, especially hydronephrosis.

Congenital unilateral hydronephrosis: a review of the impact of diuretic renography on clinical treatment.

PURPOSE: The natural history of and optimal treatment for asymptomatic congenital hydronephrosis is unknown, mainly because most published series are nonrandomized or retrospective with nonstandardized followup regimens. In this survey we provide an overview of the different strategies used for the treatment of congenital unilateral hydronephrosis. MATERIALS AND METHODS: A comprehensive literature review of clinical studies of asymptomatic congenital unilateral hydronephrosis is presented. RESULTS: Different criteria for surgical intervention and different followup regimens have been used. Identification of the population at risk has been attempted but results are ambiguous. Surgery is done in approximately 25% of cases when using deteriorating differential function, symptoms and/or increasing hydronephrosis as criteria for operation. A nonstandardized renographic assessment does not compromise evaluation of the ideal followup but it may compromise the functional outcome. CONCLUSIONS: More studies of kidneys with decreased function, severe hydronephrosis or poor drainage investigated with a standardized protocol are needed to clarify the natural history and establish optimal guidelines for treatment and followup.