Immobilization and hypercalciuria in children

Rapid Hypercalciuria Induction With Bone Formation Marker Reduction During Immobilization in Children

OBJECTIVE

To prospectively examine the occurrence of hypercalciuria and changes in bone metabolite markers in pediatric patients during immobilization.

METHODS

In total, 13 children with an orthopedic disease requiring immobilization longer than 2 weeks were enrolled. Blood samples were collected after breakfast. Urine samples were collected at the second voiding after waking. The urine calcium/creatinine (Ca/Cr) ratio and various bone metabolite parameters were measured before and every 1 to 4 weeks after the start of immobilization.

RESULTS

The median patient age was 7 years with a range of 2 to 13 years. Orthopedic diseases in the patients were dislocated hip joint (N = 7), slipped capital femoral epiphysis (N = 2), etc. The urine Ca/Cr ratio increased significantly within a week after immobilization (P < .01) and continued to increase for 2 more weeks. Once immobilization ended, the urine Ca/Cr ratio gradually decreased and returned to the normal range approximately 6 weeks after mobility was achieved (P < .01). Serum alkaline phosphatase (ALP) and bone-specific ALP significantly decreased after immobilization began (P < .01). After immobilization ended, the serum ALP returned to preimmobilization levels in 2 to 4 weeks (P < .01). Serum N-terminal telopeptides did not change significantly during immobilization.

CONCLUSION

The urine Ca/Cr ratio immediately increased after immobilization. In contrast to adults, bone formation markers in children decreased during immobilization, whereas bone resorption markers did not increase. To our knowledge, this study is the first to examine bone metabolism markers in children during immobilization.

Stone growth patterns and risk for surgery among children presenting with hypercalciuria, hypocitraturia and cystinuria as underlying metabolic causes of urolithiasis

INTRODUCTION

Hypercalciuria, hypocitraturia and cystinuria are the most common underlying metabolic stone abnormalities in children. The present study compared stone growth patterns, stone burden, and the risk of stone-related surgery among these underlying metabolic conditions.

METHODS

A retrospective cohort of 356 children with renal stones, followed from 2000 to 2015, was studied. Differences among metabolic groups were determined using Kruskal-Wallis test; the Scheffé-test was used for multiple comparisons to determine differences among single groups. Independent sample t-test was used when adequate, given the sample size, and Chi-squared test was used for categorical variables. Stone growth rates were calculated as differences in diameter divided by time elapsed between U/Ss (mm/year). Logistic regression was performed to assess the effect of initial stone size on the likelihood of surgery.

RESULTS

Median stone size at presentation was significantly different among groups, with cystinuria being the group with the largest proportion of stones >10 mm, while patients with stones <5 mm were likely to have a normal metabolic workup (P < 0.05). Stones with a higher growth rate were found in the operative group, while slower growing stones were mostly managed conservatively (3.4 mm/year vs 0.8 mm/year, respectively; P = 0.014). However, stone growth rates were not significantly different among metabolic groups. On the other hand, the rate of new stone formation in cystinuric patients at their first follow-up was 30.4%, which was significantly higher than in patients with hypercalciuria (16.3%) or with a normal metabolic workup (17.2%; P < 0.05). Compared with stones <5 mm, stones measuring 5-10 mm were more than four times more likely to result in surgery, whereas the likelihood of surgery for 10-20 mm or >20 mm stones was almost 16 or 34 times, respectively (P < 0.001).

CONCLUSIONS

It is believed that this is the first study to evaluate stone growth patterns, stone burden and surgical risk among children with hypercalciuria, hypocitraturia and cystinuria. Cystinuric patients presented with larger stones at the time of diagnosis, higher new stone formation rates, and were at higher risk of surgery. While no significant difference of growth rate was found among metabolic groups, stones with a higher growth rate were significantly more likely to result in surgical treatment than slower growing stones. Initial stone size, location of largest stone, previous urinary tract infection, and patient's metabolic type significantly influenced the likelihood of a surgical intervention. Better understanding of the natural history ultimately helps surgeons and clinicians defining prognosis, treatment, and prevention plans for pediatric urolithiasis.

Epidemiology of paediatric renal stone disease: a 22-year single centre experience in the UK

Background

Whilst still rare, the incidence of paediatric stone disease is increasing in developed countries and it is important to evaluate the aetiology. We set up a dedicated renal stone service for children combining medical and surgical expertise in 1993 and now have a large case series of children to investigate the epidemiology.

Methods

A retrospective hospital note review of children presenting with kidney stones during the last 22 years (1993–2015) was conducted. All patients had a comprehensive infective and metabolic screen and were classified as metabolic, infective or idiopathic stone disease.

Results

Five hundred eleven patients (322 male) were reviewed. The median age of presentation was 4.4y for males (1 m-16.6y) and 7.3y (1–18.5y) for females with a median height and weight on the 25th centile for male and on 10th and 25th for female, respectively. One hundred seventy five (34%) had an underlying metabolic abnormality, 112 (22%) had infective stones and 224 (44%) were classified as idiopathic.

Of the 175 patients with a metabolic abnormality: 91 (52%) had hypercalciuria (76 persistent and 15 transient), 37 (21%) hyperoxaluria, 38 (22%) cystinuria, 3 (2%) abnormalities in the purine metabolism and the remainder other metabolic abnormalities. Bilateral stones occurred in 27% of the metabolic group compared to 16% in the non-metabolic group (OR 0.2, p < 0.05). Urinary tract infection was a common complication (27%) in the metabolic group.

Conclusions

In this paper, we present the largest cohort of paediatric stone disease reported from a developed country giving details on both, clinical and laboratory data. We show that in the majority of the patients there is an identifiable underlying metabolic and/or infective aetiology emphasizing the importance of a full work up to provide adequate treatment and prevent recurrence. Moreover, we show that stone disease in children, in contrast to the adult population, does not seem to be associated with obesity, as children have a weight below average at presentation.

Hypercalcemia due to Milk-Alkali Syndrome and Fracture-Induced Immobilization in an Adolescent Boy with Hypoparathyroidism

BACKGROUND

Hypercalcemia of immobilization, while rare, may occur in adolescent boys after fracture. Although not fully understood, the mechanism appears to be related to bone turnover uncoupling, in part mediated by upregulation of RANKL. Animal studies suggest that parathyroidectomy suppresses RANKL-stimulated osteoclastogenesis in immobilized bone. Thus, immobilization-induced hypercalcemia should be uncommon in patients with hypoparathyroidism.

METHODS/RESULTS

We present a 15-year-old boy with well-controlled hypoparathyroidism who developed hypercalcemia and milk-alkali syndrome 5 weeks after sustaining a severe tibia/fibula fracture requiring bedrest. Milk-alkali syndrome (hypercalcemia, alkalosis, and renal insufficiency) results from chronic excessive ingestion of calcium and absorbable alkali. Prior to fracture, our patient had not experienced hypercalcemia despite high doses of supplements, necessary during puberty. Supplements were discontinued and his biochemistries normalized with saline diuresis and a dose of pamidronate. Alkaline phosphatase, which was low at presentation, returned to normal 5 weeks later with remobilization.

CONCLUSIONS

Fracture and immobilization caused acute suppression of bone formation with persistent bone resorption in this rapidly growing adolescent; continuation of carbonate-containing calcium supplements resulted in the milk-alkali syndrome. Therefore, close monitoring of serum calcium with adjustments in supplementation are indicated in immobilized patients with hypoparathyroidism. © 2016 S. Karger AG, Basel.

Children with spinal abnormalities have an increased health burden from upper tract urolithiasis

OBJECTIVE

To examine the epidemiology and health care burden of upper tract urolithiasis in children with spinal abnormalities using a large, national database. Children with spinal dysraphism are predisposed to urolithiasis for many reasons, including immobility, bacteriuria, and urinary stasis. No large epidemiologic studies exist regarding stones in this specific group. Isolated spinal curvature may lead to hypercalciuria from immobility; however, urolithiasis rates are unknown.

METHODS

We extracted data from the Pediatric Health Information Systems database over an 8-year period. Hospitals reporting inpatient visits, emergency room visits, and ambulatory surgery visits were included. Using International Classification of Diseases, Ninth Revision codes and Current Procedural Terminology codes, we identified children with upper tract urolithiasis, spinal dysraphism, and spinal curvature. Data regarding demographics, prevalence, surgical procedures, costs related to stone procedures were extracted.

RESULTS

A total of 11,987 patients had urolithiasis. Prevalence of stones in patients with normal spines was 0.24% compared with 1.40% and 4.03% among children with spinal curvature and spinal dysraphism, respectively (P<.001). Children with spinal curvature and spinal dysraphism were more likely to have multiple procedures for stones than those without spinal abnormalities (25% vs 25.7% vs 13.1%, P<.001). Costs per patient were significantly higher for children with spinal abnormalities compared with those with normal spines.

CONCLUSION

Children with spinal curvature and spinal dysraphism have a much greater rate of upper tract urolithiasis, resulting in more procedures and related costs. Urolithiasis represents a significant, chronic health burden for children with spinal abnormalities. Screening and preventive care may reduce the impact of urolithiasis in these patients.

Comparative analysis of nephrolithiasis in otherwise healthy versus medically complex gastrostomy fed children

PURPOSE

The purpose was to compare nephrolithiasis in healthy versus medically complex gastrostomy fed children.

MATERIALS AND METHODS

Children with nephrolithiasis with and without gastrostomy were identified by database searches from 1999 to 2009. Gastrostomy fed stone formers (GSF) were compared to an age-matched cohort of non-gastrostomy-fed stone formers (NGSF) for demographic and clinical data.

RESULTS

16 neurologically impaired GSF (10M:6F), mean age 10.4 years (range 1.7-17.5 years), were compared to 32 matched neurologically intact NGSF. Compared to NGSF, GSF had significantly higher urine pH (6.93 vs 6.23, p = 0.001) and larger stones (14.5 vs 6.9 mm, p = 0.02) more commonly composed of calcium phosphate (7/11, 64% vs 3/28, 11%, p = 0.002). 15/16 (94%) of GSF were immobile while 0% of NGSF were immobile. GSF had lower l-spine bone density Z-scores (-3.02 vs -1, p = 0.002) but an equal rate of hypercalciuria (2/7, 29% vs 7/24, 29%, p = NS). Contributing lithogenic factors in 8/16 (50%) GSF included urinary tract infection (UTI) (5), lithogenic medications (2), and xanthinuria (1).

CONCLUSIONS

Stone disease in GSF is multifactorial, and half of our study group had an identifiable risk factor for nephrolithiasis. A recurring pattern of alkaline urine and calcium phosphate stone formation was evident. GSF did not have higher rates of hypercalciuria despite chronic immobilization and markedly lower bone density. An awareness of the potential risk factors identified is mandatory for this vulnerable population.