Epidemiology of paediatric renal stone disease in the UK.

BACKGROUND: The previous epidemiological study of paediatric nephrolithiasis in Britain was conducted more than 30 years ago. AIMS: To examine the presenting features, predisposing factors, and treatment strategies used in paediatric stones presenting to a British centre over the past five years. METHODS: A total of 121 children presented with a urinary tract renal stone, to one adult and one paediatric centre, over a five year period (1997-2001). All children were reviewed in a dedicated stone clinic and had a full infective and metabolic stone investigative work up. Treatment was assessed by retrospective hospital note review. RESULTS: A metabolic abnormality was found in 44% of children, 30% were classified as infective, and 26% idiopathic. Bilateral stones on presentation occurred in 26% of the metabolic group compared to 12% in the infective/idiopathic group (odds ratio 2.7, 95% CI 1.03 to 7.02). Coexisting urinary tract infection was common (49%) in the metabolic group. Surgically, minimally invasive techniques (lithotripsy, percutaneous nephrolithotomy, and endoscopy) were used in 68% of patients. CONCLUSIONS: There has been a shift in the epidemiology of paediatric renal stone disease in the UK over the past 30 years. Underlying metabolic causes are now the most common but can be masked by coexisting urinary tract infection. Treatment has progressed, especially surgically, with sophisticated minimally invasive techniques now employed. All children with renal stones should have a metabolic screen.     

Epidemiology of paediatric renal stone disease in the UK

Background: The previous epidemiological study of paediatric nephrolithiasis in Britain was conducted more than 30 years ago. Aims: To examine the presenting features, predisposing factors, and treatment strategies used in paediatric stones presenting to a British centre over the past five years. Methods: A total of 121 children presented with a urinary tract renal stone, to one adult and one paediatric centre, over a five year period (1997–2001). All children were reviewed in a dedicated stone clinic and had a full infective and metabolic stone investigative work up. Treatment was assessed by retrospective hospital note review. Results: A metabolic abnormality was found in 44% of children, 30% were classified as infective, and 26% idiopathic. Bilateral stones on presentation occurred in 26% of the metabolic group compared to 12% in the infective/idiopathic group (odds ratio 2.7, 95% CI 1.03 to 7.02). Coexisting urinary tract infection was common (49%) in the metabolic group. Surgically, minimally invasive techniques (lithotripsy, percutaneous nephrolithotomy, and endoscopy) were used in 68% of patients. Conclusions: There has been a shift in the epidemiology of paediatric renal stone disease in the UK over the past 30 years. Underlying metabolic causes are now the most common but can be masked by coexisting urinary tract infection. Treatment has progressed, especially surgically, with sophisticated minimally invasive techniques now employed. All children with renal stones should have a metabolic screen.     

Nephrocalcinosis in preterm babies

OBJECTIVES: To determine prospectively the incidence and cause of nephrocalcinosis in preterm infants. STUDY DESIGN: Inborn babies of gestation less than 32 weeks or birth weight less than 1500 g were eligible to be entered into a prospective observational study. Two renal ultrasound scans were performed, the first at 1 month postnatal age and the second at term or discharge. Data were collected on gestation, birth weight, sex, race, family history of renal calculi, oliguria on first day, respiratory support (ventilation, steroid, and oxygen dependency), and use of nephrotoxic drugs (gentamicin, vancomycin, and frusemide). Intake of fluid, calcium, and phosphate and plasma urea, creatinine, calcium, and phosphate were recorded for the first 6 weeks of life. Random urinary calcium/creatinine, oxalate/creatinine, and urate/creatinine ratios and tubular absorption of phosphate were measured once at term. RESULTS: A total of 101 preterm infants were studied. Twenty three (23%) had abnormal ultrasound scans. Sixteen (16%) had nephrocalcinosis. On univariate analysis, gestational age, male sex, duration of ventilation, oxygen dependency, duration and frequency of gentamicin treatment, toxic gentamicin/vancomycin levels, and postnatal dexamethasone were significantly associated with nephrocalcinosis. In addition, babies with nephrocalcinosis had a lower intake of fluid, calcium, and phosphate, longer duration of total parenteral nutrition, and higher urinary oxalate/creatinine and urate/creatinine ratios than infants who did not have the condition. There was also a significant association with plasma urea and creatinine but not with plasma calcium or phosphate or urinary calcium. Multivariate analysis showed that the strongest predictors of nephrocalcinosis were duration of ventilation, toxic gentamicin/vancomycin levels, low fluid intake, and male sex. CONCLUSION: 16% of babies born at less than 32 weeks gestation developed nephrocalcinosis. The multifactorial origin, in particular, the association with extreme prematurity and severity of respiratory disease, is confirmed. In addition, an association with male sex, frequency and duration of gentamicin use, and high urinary oxalate and urate excretion is shown.     

An uncommon cause of acute kidney injury in young children: Cystinuria

Bilateral obstructive nephrolithiasis is a rare cause of acute kidney injury (AKI) in early childhood. As soon as the identification of AKI secondary to ureteral stone is made, it will necessitate an emergency treatment.PatientsWe report three infants with AKI caused by bilateral obstructive ureteral cystine stones. They were diagnosed with acute post-renal injury due to obstructive bilateral ureteral stones based on ultrasound scan findings. Immediately, bilateral ureteral stents were inserted for urinary drainage. Once renal function recovered to normal, each patient underwent ureteroscopy and percutaneous nephrolithotomy at the same session. Cystinuria was diagnosed by stone analysis and increased urinary excretion of cystine. Patients were advised to maintain a high fluid intake and were treated with potassium citrate in addition to tiopronin.ConclusionsWith these three cases we would like to emphasize the importance of urolithiasis in the differential diagnosis of acute renal failure in young children, since urolithiasis may only cause nonspecific symptoms in this population. An early diagnosis with prompt treatment and a close follow-up are the key for achieving the best long-term outcome in cystinuria.     

Hypercalciuria is the main renal abnormality finding in Human Immunodeficiency Virus-infected children in Venezuela

Kidney involvement in children with Human Immunodeficiency Virus (HIV) infection is increasing in prevalence in parallel with the longer survival of HIV-infected patients and the side-effects of new antiretroviral drugs. However, there are only a few reports describing renal tubular disorders in HIV+ children. This is a cross-sectional, case series study evaluating kidney disease in 26 Venezuelan HIV-infected children. The study cohort consisted of 15 girls and 11 boys, with a median age of 5.9 years (25–75th percentile: 3.6–7.8), who had been treated with antiretrovirals for 2.8 ± 0.4 years, Overall, the patients were short for their age and gender (Z-height: −3.1; 25–75th percentile: −4.94 to −1.98), and 15 showed signs of mild to moderate malnutrition. All of the children had a normal estimated glomerular filtration rate (136 ± 22.6 ml/min/1.73 m²), and glomerular involvement was only observed in one patient with isolated proteinuria. None had nephromegaly. In contrast, tubular disorders were commonly found. Hypercalciuria was detected in 16 of the patients (UCa/Cr = 0.28; 25–75th percentile: 0.17–0.54 mg/mg), with five of these showing crystalluria. Eight children showed hyperchloremia, and three had frank metabolic acidosis. Kidney stones were absent in all, but one boy had bilateral medullary nephrocalcinosis. Conclusion, in Venezuelan children, HIV infection per se, or its specific treatment, was commonly associated with renal tubular dysfunction, especially hypercalciuria and acidosis, potentially leading to nephrocalcinosis and growth impairment. We recommend renal tubular evaluation during the follow-up of children with HIV infection.     

Medullary sponge kidney associated with distal renal tubular acidosis in a 5-year-old girl

Introduction Medullary sponge kidney (MSK) is characterized by cystic dilatation of the inner medullary collecting ducts, which causes the kidneys to resemble a sponge.Case report Although distal renal tubular acidosis (dRTA) is commonly observed in patients with MSK, we report a 5-year-old girl with MSK who had features of both dRTA (nephrocalcinosis, hypercalciuria, hypocitraturia) and proximal tubular dysfunction (hyperuricosuria, impaired tubular phosphate reabsorption and proteinuria).Discussion Metabolic acidosis, hypercalciuria, hypocitraturia, tubular phosphate reabsorption and growth retardation in the patient improved with alkali therapy.     

Unusual Renal Manifestations in a Girl with Hyperthyroidism

A 16-year-girl, a known case of hyperthyroidism since last 6 months, presented to the emergency with complaints of acute gastroenteritis of 5 days duration. At admission the child was found to be hypovolemic with acidotic breathing, which was thought to be due to dehydration. However, despite fluid correction she remained acidotic. A diagnosis of distal renal tubular acidosis (RTA) was suspected when her renal scan, for the cause of metabolic acidosis, revealed nephrocalcinosis. This was later confirmed by relevant investigations. She was started on treatment for distal RTA on which she symptomatically improved. The association of distal RTA and thyroid disorders is rarely reported in children. Till date there is only one report of distal RTA and hypothyroidism, but none with hyperthyroidism in this age group. The authors chose to report this case to highlight the fact that one should have a high index of suspicion for renal tubular disorders in children with thyroid hormone abnormalities, as these are treatable conditions if diagnosed early.     

Intracraneal epidural abscess as a complication of sinusitis

Familiar hypomagnesemia with hypercalciuria and nephrocalcinosis is a rare syndrome belonging to the group of heterogeneous tubular diseases whose common characteristic is renal magnesium wasting. We present a 9 year old boy with polyuria, polydipsia and enuresis. Radiologic and ultrasonographic examinations showed nephrocalcinosis. Hypomagnesemia, normokaliemia, hypermagnesiuria, hypercalciuria, incomplete distal tubular acidosis, hypocitraturia and mild renal failure were found. Treatment with magnesium salts, hydrochlorothiazide, potassium citrate and sodium bicarbonate did not restore magnesium or calcium levels to normal. Renal function and nephrocalcinosis remain stable after 3 year's treatment. In conclusion, we report a new case of this rare syndrome caused by a congenital defect in magnesium reabsorption and discuss the evolution of the illness during 3 years' treatment.     

Extracorporeal lithotripsy in children. Study of its efficacy and evaluation of renal parenchymal damage by DMSA-Tc 99m scintigraphy: a series of 39 children]

AIM: The objectives of the study were to confirm the efficacy of extracorporeal shock wave lithotripsy (ESWL) in infants and children and to evaluate potential long-term renal parenchymal damage by 99m Tc DMSA renal scan. MATERIALS AND METHODS: Between November 1989 and November 1997, 39 children between 10 months and 17-1/2 years of age (average: 7 years) were treated by extracorporeal shock wave lithotripsy for kidney or ureteral stones with a Sonolith 3000 lithotriptor (Technomed Corp). Forty-six stones were treated. Eight metabolic and 11 urological abnormalities were identified. The evaluation of the treatment and its consequences were based on a clinical examination, conventional imaging and a DMSA renal scan performed 24 h before extracorporeal shock wave lithotripsy and at least 6 months after treatment. RESULTS: Treatment was successful (stone fragmented and eliminated) in 84.6% at 3 months after one to four sessions. Sixty-one sessions were necessary and two patients underwent open surgery for failed extracorporeal shock wave lithotripsy. Three recurrences were also retreated. At long term follow-up (6 months to 8 years) no incidents of high blood pressure were observed, nor parenchymal lesions imputable to extracorporeal shock wave lithotripsy. CONCLUSIONS: The efficacy of the extracorporeal shock wave lithotripsy for children is proven. This study also confirms the innocuousness of extracorporeal shock wave lithotripsy for renal parenchyma even in infants. However, long term follow-up and further evaluation with the other categories of lithotriptors are necessary to make definitive conclusions.     

Continuous renal replacement therapy for patients with acute kidney injury caused by melamine-related urolithiasis

Background  

In 2008 there was an epidemic of renal disease affecting infants after consumption of melaminetainted milk products. Most of the infected children were asymptomatic or with mild symptoms, and a few suffered from acute obstructive kidney injury secondary to melamine-contained renal stones (8 of 15 577 children screened at our hospital for urolithiasis). This study was intended to retrospectively review the management of acute kidney injury using continuous renal replacement therapy (CRRT) in the 8 children with acute kidney injury.     

Etiologic and Epidemiologic Pattern of Urolithiasis in North Iran;Review of 10-Year Findings

Objective: To determine epidemiologic and metabolic characteristics of renal stone in the northern Iran. Methods: We prospectively analyzed demographic, clinical and metabolic findings in children less than 16 years old with renal stone revealed by ultrasonography from September 2003 to May 2012. Evaluations included serum and urine measurement of main elements predisposing patients to stone formation. Findings : 271 children (160 males) aged 2 months to 16-years (mean 30 months) were evaluated. 91 (33.6%) had a positive family history, abdominal discomfort (18.8%), UTI (11.8%) and hematuria (11.4%) were main presenting features. 45 children were diagnosed accidentally without any specific compliant. Nearly all (99%) stones lay in kidney., 35.1% had metabolic, 10% infective and 4.1% obstructive trends, 110 children had no definable etiology. Hypercalciuria (25.5%) hyperoxaluria (18.4%) and hypocitraturia (18.1%) were more frequent than uricosuria (8.5%) and cystinuria (3.1%) Conclusion: Metabolic derangement plays significant role in stone formation in our area. Patients should be carefully evaluated considering this point of view.Key Words: Nephrolithiasis, Kidney Stone, Hypercalciuria, Hyperoxaluria, Cystinuria, Hypocitraturia     

LYMPHANGIOMA OF THE RIGHT KIDNEY IN AN INFANT BOY

A 9-month-old boy with a primary cystic lymphangioma of the right kidney is reported. The clinical and radiological features favored a malignant tumor. Histology revealed the lesion to be a lymphangioma; the diagnosis was confirmed by immunohistochemistry and chemical analysis of the intracystic fluid. Lymphangiomas of the kidney are rare in adults; they are even rarer in infants and children. Nevertheless, renal lymphangiomas should be considered in the differential diagnosis of multicystic, unilateral renal masses, independent of the age of the patient.     

Urinary calcium excretion in enterally fed disabled children.

The urine calcium/creatinine (Ca/Cr) ratio was measured in 17 enterally tube fed disabled children. Urine Ca/Cr ratios were inversely related to dietary calcium intake in immobile children (r = -0.57, p < 0.05) but not in those who were able to stand or walk (mobile children) (r = 0.4, p = 0.51). None of the subjects had evidence of nephrocalcinosis or renal calculi detectable by renal ultrasonography.     

Surgical management of renal tract problems

The majority of renal tract problems in childhood are congenital in origin with an overall incidence of 2–4 per 1000 live births. Some anomalies may occur in isolation e.g. posterior urethral valves; whilst others may be part of a more complex spectrum of anomalies e.g. duplex or horseshoe kidney in VACTERL or VATER association. Prenatal screening has highlighted an increasing number of children with renal tract anomalies which may require paediatric specialist involvement in the immediate postnatal period. Most congenital renal tract problems are managed by paediatric urologists and paediatric surgeons with a special interest in urology.The aim of this review is to highlight the most common renal tract disorders of childhood and to discuss their aetiology, clinical presentation, investigation and surgical management.     

Acute kidney injury

The definition and classification of acute kidney injury (AKI) in children has become clearer over the last decade. The paediatric RIFLE criteria stratify AKI in children into five groups (R = risk, I = injury, F = failure, L = loss of kidney function, E = end stage renal disease) enabling earlier recognition and intervention. This article reviews the definition, classification, causes and management of AKI as relevant to the general paediatrician.Common causes of AKI in neonates and children are reviewed including E. Coli associated haemolytic uraemic syndrome, hypoxic ischaemic insults and medication related kidney injury. Initial management of acute kidney injury and its complications is outlined in the context of the role of the general paediatrician and factors which should prompt discussion with a tertiary paediatric nephrologist. The outcome and complications of kidney injury are discussed and future directions in the field considered.     

Efficacy and side effects of differential calcium and phosphate administration in prevention of osteopenia in premature infants

The prevention of osteopenia and frequency of renal and intestinal side effects of mineral supplementation was studied in 24 preterm infants with birth weight under 1,500 g, prospectively (gestational age 26-34 weeks). Calcium intake varied from 2.5 vs. 3.75 vs. 5 mmol/kg/day, phosphate was offered in dose of 2.5 mmol/kg/day. At the expected birth date 40% of infants with low calcium dose showed an activity of serum alkaline phosphatase greater than five times the maximum adult normal value which is defined as a reliable marker; for osteopenia no infant with medium or high calcium intake reached this critical value (p = 0.03). Medium and high calcium doses resulted in an increased risk for hypercalcuria (25 vs. 50%) (p = 0.03). Half of these infants developed typical signs of nephrocalcinosis on ultrasound examination. No significant difference of fecal fat content was observed with increased calcium intake; but more episodes of abdominal distension occurred during the first days of high calcium supplementation (p = 0.03). We conclude, that a calcium intake of 3.75 mmol/kg/day in combination with phosphate 2.5 mmol/kg/day is sufficient for adequate bone mineralization on a low level of side effects. Calcium excretion in urine has to be observed for early diagnosis of nephrocalcinosis.     

Long-term results of pre-emptive liver transplantation in primary hyperoxaluria type 1

In primary hyperoxaluria type 1 (PH 1), deficiency or mistargeting of hepatic alanine glyoxylate aminotransferase (AGT) results in over-production of oxalate and hyperoxaluria, leading to nephrocalcinosis and development of end-stage renal disease (ESRD) in the majority of patients. Renal transplantation (Tx) alone carries a high risk of disease recurrence as the metabolic defect is not cured. Therefore, combined liver/kidney Tx is recommended for patients with ESRD. An alternative approach is to cure PH 1 by pre-emptive isolated liver Tx (PLTx) before ESRD has occurred, but this approach has been carried out only occasionally and there are no uniformly accepted recommendations concerning the timing of this procedure. We report follow-up 3-5.7 yr after performing successful PLTx in four children (at the age of 3-9 yrs) with PH 1 prior to the occurrence of ESRD (glomerular filtration rate [GFR] range 27-98 mL/min/1.73 m2). There was no mortality or long-term morbidity associated with the Tx procedure. Plasma and urinary oxalate levels normalized rapidly within 4 weeks, and renal function did not deteriorate under immunosuppression, even in one patient with advanced chronic renal failure (GFR 27 mL/min/1.73 m2) who showed a stable course for more than 5.7 yrs. Although treatment must be individualized in this severe metabolic disorder, and PLTx has to be regarded as an invasive procedure, we consider that PLTx should be offered and considered early in the course of PH 1. PLTx cures the metabolic defect in PH 1 and can help to prevent, or at least delay, the progression to ESRD and systemic oxalosis.     

Incidence, ultrasonic patterns and resolution of nephrocalcinosis in very low birthweight infants

This longitudinal study was undertaken in order to elucidate the incidence and natural course of nephrocalcinosis in preterm infants and to evaluate whether the ultrasonic classification for nephrocalcinosis used here is suitable for predicting subsequent resolution of the condition. A total of 129 very low birthweight infants were screened for nephrocalcinosis by renal ultrasonography at 2 wk, 6 wk and 3 mo. The pyramidal changes were classified as peripheral, scattered or extensive. Follow-up renal ultrasonography was performed on the infants with nephrocalcinosis at 6, 12, 18 and 24 mo, and thereafter annually up to 6 y of age, or until ultrasonic resolution. The overall incidence of nephrocalcinosis was 20% (26/129). Nephrocalcinotic changes were peripheral in 14 out of the 26 infants (54%), scattered in 7 (27%) and extensive in 5 (19%). Ultrasonic resolution had taken place in all the cases with peripheral nephrocalcinosis by 12 mo, but 3 of the 7 infants with the scattered pattern and 3 of the 4 with the extensive pattern (1 died) were still affected at 24 mo. In two cases with extensive nephrocalcinosis the condition still persisted at 5-6 y of age. We conclude that about 20% of very low birthweight infants develop nephrocalcinosis during the first 3 mo of life. In about half of the affected infants renal changes are restricted and transient, but more extensive forms may last several years. The classification of nephrocalcinosis used here is appropriate for predicting later ultrasonic resolution.     

Management of Acute Kidney Injury

Acute kidney injury is common in hospitalized children and is associated with siginficant morbidity and mortality especially in critically ill children. A complete evaluation is necessary for all children with AKI as early recognition and treatment is paramount. Apart from clinical evaluation, urinalysis, biochemical investigations and imaging studies helps in the diagnosis of the specific cause of AKI and assessing its severity. Attention should be given to assessment of volume status and fluid administration because volume depletion is a common and modifiable risk factor for AKI. Prevention or prompt management of complications like fliud overload, hyperkalemia and metabolic acidosis improves outcomes. Immediate initiation of renal replacement therapy (RRT) is indicated in the presence of life threatening changes in fluid, electrolyte and acid-base balance. Other measures like treating the underlying cause of AKI, adapting dosage of drugs to renal function, treatment of infections and providing adequate nutrition is important. Children with AKI should be followed up as they are at risk for development of chronic kidney disease.