Sickle cell nephropathy is now a well characterized entity with specific manifestations, risk factors, and prognosis. This review provides an approach to understanding the mechanisms involved in the development of the nephropathy, in order to provide rational treatment for the patients.

The

Sickle Cell Nephropathy

The prevalence of nephrocalcinosis (NC) in preterm neonates in recent reports is 7-41%. The wide range in prevalence is a consequence of different study populations and ultrasound equipment and criteria, in addition to a moderate interobserver variation. NC in preterm neonates has a multifactorial aetiology, consisting of low gestational age and birth weight, often in combination with severe respiratory disease, and occurs as a result of an imbalance between stone-promoting and stone-inhibiting factors. A limited number of histological studies suggest that calcium oxalate crystals play an important role in NC in premature neonates. In 85% of children resolution of NC occurs in the first years of life. Prematurity, per se, is associated with high blood pressure, relatively small kidneys, and (distal) tubular dysfunction. In addition, NC in preterm neonates can have long-term sequelae for glomerular and tubular function. Long-term follow-up of blood pressure and renal function of prematurely born children, especially with neonatal NC, is recommended. Prevention of NC with (low) oral doses of citrate has not resulted in a significant decrease in the prevalence of NC; a higher citrate dosage deserves further study. Future research pertaining to prevention of NC in preterm neonates is crucial.

https://link.springer.com/content/pdf/10.1007%2Fs00467-008-0908-9.pdf

Nephrocalcinosis in preterm neonates

https://www.kidney-international.org/article/S0085-2538(15)47319-3/pdf

Etiology of nephrocalcinosis in preterm neonates: Association of nutritional intake and urinary parameters

We carried out a retrospective survey on 152 children and adolescents with nephrocalcinosis (NC) in 22 German centers of pediatric nephrology. Etiology, clinical manifestations, growth and development, sonographic appearance of NC and renal function were analyzed. The median age at the time of diagnosis was 3.3 (range 0.1–21) years and the median duration of follow-up was 4.1 years. In 34% of children NC was associated with idiopathic hypercalciuria (IHC) and in 32% with various hereditary tubular disorders. In 9% NC was observed subsequent to prophylactic bolus administration of vitamin D in infancy. A positive family history was found in 36%. Clinical manifestations were mainly failure to thrive during the 1st year of life (46%), psychomotor/mental retardation (28%) and urinary tract infection (34%). In 14% nephrolithiasis was associated. During the follow-up the proportion of patients with the most severe degree of NC (stages 2b or 3) increased from 40% to 55% and that of hypercalciuria decreased from 79% to 52%. Body height was <2 standard deviation scores (SDS) of normal in 41% at the time of diagnosis and in 32% at the last observation; the increase in relative height was significant only for IHC. Glomerular filtration rate (GFR) and urinary concentration capacity changed only slightly with time. At the last investigation GFR was <50 ml/min/1.73 m2 in 6% and concentration capacity <800 mosmol/kg in 48% of patients. The degree of NC was negatively correlated with GFR and concentration capacity.

Nephrocalcinosis in children: a retrospective survey

Increased echogenicity of the kidney in the newborn has many causes, some of which reflect serious renal disease. The major abnormal imaging pattern is the large, diffusely hyperechoic kidney with abnormal architecture. Its differential diagnosis includes recessive and dominant polycystic kidney disease (PKD), glomerulocystic kidney disease, and diffuse cystic dysplasia. The family history and ultrasonic screening of the parents and siblings are essential in the evaluation. The identification of associated nonrenal abnormalities is important to the recognition of syndromal cystic disease. Glomerulocystic kidney disease, which comprises sporadic and syndromal forms, appears similar to dominant PKD. While renal biopsy almost always differentiates recessive from dominant PKD, renal biopsy cannot differentiate among the forms of glomerulocystic kidney disease, except in the case of tuberous sclerosis, which has unique histopathological characteristics. Other causes of the enlarged hyperechoic kidneys with abnormal architecture include renal vein thrombosis and congenital nephrotic syndrome. A second pattern is the hyperechoic small kidney with abnormal architecture. Many of these kidneys are dysplastic and associated with urinary tract obstruction. The combination of hyperechoic parenchyma and pyelocaliceal dilatation suggests obstructive cystic dysplasia. Cortical and medullary necrosis in the newborn also causes hyperechogenicity in small kidneys. A third pattern contains those kidneys with medullary hyperechogenicity, the most common cause of which in the newborn is nephrocalcinosis associated with furosemide therapy. A systematic approach to the differential diagnosis of the hyperechoic kidney will enable the nephrologist to choose additional imaging studies and to limit the use of invasive procedures.

Hyperechoic kidneys in the newborn and young infant

Fifty-five children (34 boys, 21 girls; age range, 1 day to 18 years) with increased echogenicity of the renal medullary pyramids at ultrasound evaluation were identified. The clinical diagnoses associated with hyperechoic medullary pyramids could be separated based on the presence or absence of hypercalciuria. Patients with drug-induced hypercalciuria included 10 infants treated with furosemide, two treated with long-term steroid therapy, and one treated with excessive amounts of vitamin D. Other clinical conditions associated with hypercalciuria included renal tubular acidosis (n = 10), Bartter syndrome (n = 5), hyperparathyroidism (n = 3), Williams syndrome (n = 2) and medullary sponge kidney (n = 2). Ten children with transient renal insufficiency and three with sickle cell disease had normal urine calcium concentration. Isolated disease entities accounted for the remainder of cases. A specific diagnosis can usually be made in a patient with hyperechoic renal medullary pyramids by using a systematic clinical approach that includes evaluation of patient age, serum and urine calcium concentration, and renal function.

Hyperechoic renal medullary pyramids in infants and children.

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Hyperechoic renal medullary pyramids in infants and children.