Effects of low-dose dopamine on urine output in normotensive very low birth weight neonates.

OBJECTIVE: To determine the effects of low-dose dopamine on urine output (UOP) in very low birth weight premature neonates. STUDY DESIGN: Retrospective cohort study of all low-dose (3-5 µg kg(-1) per min) dopamine infusions >24-h duration in neonates 1500 g and 32 weeks gestation from August 2009 through September 2011. Linear regression was used to estimate the impact of covariates on UOP. RESULT: We identified 91 episodes of low-dose dopamine use in 65 neonates. Increased UOP occurred in 64% of episodes. Low-dose dopamine use was associated with a 0.6 ml kg(-1) h(-1) increase in UOP (P<0.001) and a 1.3 ml kg(-1)h(-1) increase when baseline UOP was <1.5 ml kg(-1) h(-1) (P<0.001). The improvement remained statistically significant after controlling for medications (diuretics and hydrocortisone) and fluid intake. CONCLUSION: Low-dose dopamine use was associated with increased UOP in very low birth weight neonates.

Prevalence and clinical correlates of glomerulopathy in children with sickle cell disease.

OBJECTIVES: Glomerular disease and renal failure cause substantial morbidity for patients with sickle cell disease (SCD). Proteinuria is an early manifestation of sickle nephropathy, but the prevalence of proteinuria and its clinical correlations in children with SCD are unknown. STUDY DESIGN: Data were collected prospectively on children with SCD for 10 years including physical measurements, laboratory test results, and clinical complications. Persistent proteinuria was defined as > or =1+ protein on urinalysis for at least 6 months. The glomerular filtration rate was estimated with serum creatinine concentration and height. Proteinuria was correlated with other variables by chi(2) analysis. RESULTS: Proteinuria occurred in 20 of 442 pediatric patients including 15 (6.2%) with sickle cell anemia. Proteinuria increased with age, affecting 12% of older teenagers with sickle cell anemia. Proteinuria was significantly associated with lower hemoglobin concentration, higher mean corpuscular volume, and higher leukocyte count. For children of some ages, proteinuria was associated with complications including stroke, acute chest syndrome, cholelithiasis, and hospitalizations. Glomerular filtration rate hyperfiltration occurred early in life, followed by normalization. CONCLUSIONS: Sickle nephropathy, manifested as persistent proteinuria, begins early in life, occurs in all forms of SCD, and is associated with severity of disease. Early detection of proteinuria may allow therapy to prevent progressive renal insufficiency.

Thrombocytopenia and absent radii (TAR) syndrome associated with horseshoe kidney.

The TAR syndrome is an inherited disorder characterized by limb abnormalities, especially absent radii, and hypomegakaryocytic thrombocytopenia. Previous reports have included two infants with genitourinary abnormalities. We report a newborn with bilaterally absent radii and foreshortened ulnae, hypoplastic humeri, a left clubfoot, a ventricular septum defect, and persistent thrombocytopenia. This constellation of abnormalities is consistent with the TAR syndrome. In addition, he had a horseshoe kidney with parenchyma of normal appearance. This is the first report of horseshoe kidney in association with the TAR syndrome.

Perspective of a pediatric nephrology program: an 18 year retrospective.

We analyzed the patient profile in a pediatric nephrology training program, along with data collected over an 18 year period, to determine whether there is merit in the proposition that clinical training can be obtained equally well in internal medicine nephrology training programs. We also compared the rate of patient referral in an U.S. metropolitan area with a population of 1.2 million, in the first 9 years without the "gatekeeper" health insurance system and the next 9 years with managed care competition. Finally, we discussed guidelines for renal biopsy in the child and approaches to treatment as practiced in a pediatric nephrology program of almost two decades. We used the same NIH clinical data form throughout the 18 years of data collection to record clinical, laboratory and biopsy diagnosis, dialysis/ transplantation and other treatment data of patients entering our outpatient and inpatient services. Between 1977 and 1996, 3,150 new patients were examined for disorders related to the kidney. Twenty-one per cent of the patients were in the first year of life and 50% were younger than seven years of age. The majority of the 389 percutaneous renal biopsies were done in children under 10 years of age. In addition, almost half of the 112 pediatric dialysis/transplant patients presented before 10 years of age. Thus, the majority of patients were in the early years of life, with an unique pattern of renal diseases and issues regarding therapy which are clearly different from adulthood. Therefore we concluded that the existing data did not support the proposition that pediatric nephrology training be absorbed into internal medicine nephrology programs. The introduction of managed care competition did not affect the rate of patient enrollment. In fact, the rate of referrals in the latter 9 years paralleled the first 9 years. The factors which contribute to this outcome are discussed. Such data should be useful to those trying to meet the challenges of this competitive era. Finally, we discussed guidelines for renal biopsies in children and approaches to specific diseases.

Appearance of immune complex glomerulonephritis following the onset of type I diabetes mellitus in a child.

Renal disease is a frequent late complication of type I diabetes mellitus, occurring almost entirely in adult patients. Typical diabetic nephropathy is characterized by proteinuria, and by the histological lesions of mesangial expansion and basement membrane thickening. We report an interesting case of a 3-year-old boy who developed immune complex glomerulonephritis with nephrotic syndrome 2 months after the onset of insulin-dependent diabetes mellitus.

Nutritional intake in children with renal insufficiency: a report of the growth failure in children with renal diseases study.

OBJECTIVE: This study was designed to assess sequentially the nutrient intake in children with chronic renal insufficiency and its relationship to body size, the level of renal failure, and growth velocity. METHODS: The nutrient intake from 401 4-day food records obtained from 120 children with renal insufficiency over a 6-month observation period was analyzed. The height and weight were measured at the beginning and end of the observation period. The glomerular filtration rate was estimated from the height and serum creatinine. RESULTS: The mean caloric intake in these children was 80 +/- 23% (mean +/- SD) of the Recommended Dietary Allowance (RDA) for age. Fifty-six percent of the food records obtained from these children revealed a caloric intake that was less than 80% of the RDA. Caloric intake expressed as the %RDA for age decreased with increasing age. However, the mean caloric intake when factored by body weight was in the normal range. There was no correlation between caloric intake and height velocity. The mean protein intake in these children was 153 +/- 53% of the RDA. Further, 45% of the food records indicated a protein intake greater than 150% of the RDA. There was no relationship between the degree of renal insufficiency and caloric or protein intake. Calcium, vitamin, and zinc intakes were also low. CONCLUSIONS: Children with chronic renal failure consume less calories than their age matched peers, but the majority of these children appear to ingest adequate amounts for their body mass. This reduction in caloric intake occurs early in renal insufficiency. They also ingest inadequate amounts of calcium, zinc, vitamin B6, and folate.

Metabolic studies of rat renal tubule cells loaded with cystine: the cystine dimethylester model of cystinosis.

The cause of Fanconi syndrome in cystinosis is enigmatic. It has previously been shown that renal tubules could be loaded with cystine by incubating them with cystine dimethylester (CDE), mimicking the biochemical hallmark of cystinosis. Such tubules have impaired transport, decreased whole-cell O2 consumption, and substrate utilization. In this study, the metabolic disturbances in cystine-loaded renal tubule cells were further characterized. Isolated rat renal tubules were loaded with cystine by incubating them with 2 mM CDE for 10 min. This had no significant effect on total ATPase, Na(+)-K(+)-ATPase, or the ouabain-insensitive ATPase activity of renal tissue homogenates from these cystine-loaded tubules. Intracellular K was significantly lower in the cystine-loaded tubules (37 +/- 2 versus 47 +/- 3 nEq/mg; P < 0.008). Intracellular ATP was reduced by 39% in the cystine-loaded tubules (23.7 +/- 2.4 versus 38.1 +/- 3.3 nmol/mg of protein; P < 0.0025). CDE (2 mM) reduced isolated mitochondrial O2 consumption with glutamate as the substrate by 66% (4.7 +/- 0.7 versus 13.9 +/- 0.8 nm/min per mg of protein, P < 0.001) but had no effect on mitochondrial O2 consumption with succinate as the substrate. It was speculated that the impaired transport from cystine loading with CDE is secondary to a decrease in energy generation.

Insulin-like growth factor-I gene expression in the tibial epiphyseal growth plate of growth hormone-treated uremic rats.

To identify the molecular mechanisms involved in long bone growth of uremic animals, we evaluated the effects of recombinant human growth hormone (rhGH) supplementation on whole body growth, growth plate morphometrics, and insulin-like growth factor-I (IGF-I) gene expression in the tibial epiphyseal growth plates of uremic rats. Uremia was induced by a two-stage subtotal nephrectomy (Nx) of 30-day-old rats, followed by rhGH (N = 6) or saline (N = 6) treatment from day 56 to day 70 of age. Controls (N = 4) were sham decapsulated. Treatment with rhGH on Nx animals caused: (1) a significant increase in weight, (2) longitudinal growth similar to controls, and (3) increased total growth plate width predominantly due to an increase in hypertrophic zone width. rhGH increased IGF-I mRNA abundance in both zones, but the increase was greater in the proliferative zone. These changes were accompanied by concomitant alterations in IGF-I immunoreactivity. In uremic animals, therefore, rhGH treatment induces local IGF-I gene expression in the growth plate and increases the hypertrophic zone width but not the proliferative zone width. The latter suggests resistance to IGF-I action in that zone.

The peritoneal equilibration test in children.

Eight children, aged 15 months to 17 years 9 months, maintained by continuous ambulatory peritoneal dialysis (CAPD)/continuous cycling peritoneal dialysis and nine adults, aged 20-59 years, managed by CAPD were compared using a standardized peritoneal dialysis protocol, the peritoneal equilibration test (PET). The peritoneal glucose concentration tended to equilibrate with the serum glucose more rapidly in children, but the percentage of the glucose load absorbed was not different between the two age groups. There was an inverse trend between the percentage of glucose absorbed and age in children. Peritoneal creatinine clearance scaled to surface area in children was significantly less than that of the adults; however, the clearances became similar when adjusted for body weight. Peritoneal creatinine clearance scaled to surface area bore a positive and significant relationship to age which, when expressed per kilogram body weight, disappeared. Children had a significantly higher dialysate/plasma (D/P) creatinine ratio after the first 2 h of the PET, but this ratio approached unity by 4 h and was not different from adults. The fractional change in the creatinine D/P ratio during the PET was not different between the two age groups. Drain volume adjusted to surface area was significantly less in children than adults. This difference was reversed when drain volume was factored by weight. Similarly drain volume scaled to surface area demonstrated a significant and positive relationship to age, which disappeared when drain volume was expressed per kilogram body weight. Ultrafiltration, whether factored by weight or scaled to surface area, did not differ between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypercholesterolemia in rats with chronic renal insufficiency not aggravated by recombinant human growth hormone.

The lipid metabolic disorders in chronic renal insufficiency (CRI) are related to increased hepatic lipid synthesis, reduced triglyceride removal coupled with insulin insensitivity and impaired lipoprotein lipase activity. Growth hormone is lipolytic, and the effects of recombinant human growth hormone (rhGH) on the hypercholesterolemia of CRI are unsettled. To test this question, we gave rhGH for 14 days at a dosage of 3 units/day intraperitoneally to two-stage, 5/6 nephrectomized, male Sprague-Dawley rats (n = 18) compared to sex- and age-matched control (n = 27) and CRI (n = 40) rats. At the end of the study, CRI rats and those treated with rhGH had a similar degree of renal impairment, as assessed by serum concentrations (mean +/- SEM) of urea nitrogen (49 +/- 3 vs. 54 +/- 4 mg/dl), creatinine (0.9 +/- 0.0 vs. 1.0 +/- 0.1 mg/dl) and cumulative food intake (311 +/- 8 vs. 290 +/- 12 g). Serum urea nitrogen (16 +/- 4 mg/dl) and creatinine (0.4 +/- 0.1 mg/dl) concentrations as well as food intake (412 +/- 9 g) of control rats were significantly (p < 0.0001) different. Serum cholesterol concentration of CRI rats treated with rhGH (87 +/- 3 mg/dl) was not higher than those of CRI rats (81 +/- 2 mg/dl, p < 0.1338) but was significantly higher than in control rats (55 +/- 3 mg/dl, p < 0.0001). CRI rats treated with rhGH showed a similar serum albumin concentration and lower serum glucose than CRI rats (0.9 +/- 0.1 vs. 0.9 +/- 0.0 g/dl and 144 +/- 4 vs. 163 +/- 3 mg/dl, p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of calcium oxalate crystal growth in vitro by uropontin: another member of the aspartic acid-rich protein superfamily.

The majority of human urinary stones are primarily composed of calcium salts. Although normal urine is frequently supersaturated with respect to calcium oxalate, most humans do not form stones. Inhibitors are among the multiple factors that may influence the complex process of urinary stone formation. We have isolated an inhibitor of calcium oxalate crystal growth from human urine by monoclonal antibody immunoaffinity chromatography. The N-terminal amino acid sequence and acidic amino acid content of this aspartic acid-rich protein, uropontin, are similar to those of other pontin proteins from bone, plasma, breast milk, and cells. The inhibitory effect of uropontin on calcium oxalate crystal growth in vitro supports the concept that pontins may have a regulatory role. This function would be analogous to that of other members of the aspartic acid-rich protein superfamily, which stereospecifically regulate the mineralization fronts of calcium-containing crystals.

Hypercalciuria due to combined growth hormone and calcitriol therapy in uremia: effects of growth hormone on mineral homeostasis in 75% nephrectomized weanling rats.

The administration of growth hormone (GH) in conjunction with calcitriol in uremia may increase urinary calcium and decrease renal phosphate excretion, which could have an adverse effect on the kidney in chronic renal insufficiency. The effect of 40 d of ovine GH, calcitriol, and the combination of GH and calcitriol on mineral excretion was studied in rapidly growing uremic rats. Uremia was produced by 75% nephrectomy, and the animals were fed a diet containing 8% protein with equal quantities of calcium (0.6%) and phosphate (0.6%). The uremic rats treated with ovine GH were significantly longer and heavier than the uremic control rats and the uremic rats treated with calcitriol alone. However, the combination of calcitriol and GH abolished the beneficial effect of GH on growth and increased urinary calcium excretion 4-fold over uremic controls whether expressed as calcium excretion per 100 g body weight, urine calcium to creatinine ratio, or as fractional calcium excretion. Calcitriol therapy alone also significantly increased calcium excretion, but not to the extent that the combination therapy did. This increased urinary calcium excretion in the GH plus calcitriol group was not associated with an increase in calcium and sodium intake, plasma ionized calcium, or urinary sodium excretion. The calcium content of the femurs from all uremic rat groups was significantly lower than that of the sham control rats; however, there was also no further decrease in bone calcium content in the GH plus calcitriol group compared with uremic controls. This indicated that bone was not the source of this excess urinary calcium.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of cystine loading and cystine dimethylester on renal brushborder membrane transport.

The effect of loading renal tubule cells with cystine was studied by incubating them with cystine dimethylester. Proline uptake into brushborder membrane vesicles isolated from the cystine loaded cells was not different from that observed into brushborder vesicles isolated from tubules incubated in buffer alone. Incubating brushborder membranes with 2 mM cystine dimethylester for 10 minutes reduced the uptake of proline by 27% after 15 seconds of incubation and by 21% after 60 seconds of incubation. There was no effect after 20 minutes of incubation. Pre-incubating brushborder membrane vesicles with cystine dimethylester had no statistically significant effect on the affinity of proline for the carrier, but did reduce the maximal rate of proline uptake by 49%.

Effect of cystine loading on substrate oxidation by rat renal tubules.

Isolated rat renal tubules were loaded with cystine by incubating them with 2 mM cystine dimethylester. The oxidation of 1 mM glucose and lactate was significantly decreased after 20 and 30 min of incubation, in the cystine-loaded tubules compared with control tubules. The oxidation of 1 mM butyrate was significantly decreased after 10 and 30 min of incubation in the cystine-loaded tubules. Cystine loading decreased the oxidation of 1 mM succinate at all time points examined. The O2 consumption of renal tubules was reduced 59% with cystine loading by the addition of 2 mM cystine dimethylester, and by 37% with 1 mM cystine dimethylester. These data indicate that loading normal renal tubule cells with cystine impairs their ability to oxidize metabolic fuels. This impairment in metabolism may explain the decreased transport observed previously in cystine-loaded tubules and may have implications for the human disorder, cystinosis.

10-year survey of referrals to a pediatric nephrology program.

To provide a realistic picture of the patient case load of a pediatric nephrologist in a teaching hospital, we analyzed the number, the demographics, and the reasons for patient referral to our pediatric nephrology program over a 10-year period. Between January 1, 1978, and December 31, 1987, 1,523 pediatric patients were referred to the Medical College of Virginia for evaluation and treatment of renal and electrolyte disorders. The most common reason for referral was a fluid-electrolyte disorder (30%), followed by hematuria/proteinuria (22%), chronic glomerulonephropathies (10%), hypertension (5%), nephrotic syndrome (6%), end-stage renal disease (3%), urinary tract infections (5%), and acute glomerulonephritis (3%). More than 25% of the patients were under 1 year of age at initial presentation. The rest are equally distributed among the other pediatric age groups, including adolescents. Fifty-eight percent of these patients were white, and 41% were black. Males accounted for 54% of the referrals and females for 46%. Percutaneous renal biopsies were performed under ultrasound guidance on 167 patients or a rate of 17 procedures per year. Fifty-one patients, ranging in age from 0.5 to 19 years, were followed for end-stage renal disease during the 10-year study period. Glomerular disorders accounted for 61% of the end-stage renal diseases and anatomic disorders for 39%. The yearly incidence of end-stage renal diseases over this time was 9.8 patients/million children. Twenty-six (51%) of these patients received one or more kidney transplants during the study period.