Urinary stone disease in pediatric and adult metabolic bone clinic patients

Pediatric Stone Disease: Current Trends and Future Directions

Pediatric nephrolithiasis is less common in children than in adults but the incidence has been rising rapidly, and it is now a public health and economic burden in the United States. There are challenges unique to children that should be taken into consideration when evaluating and managing pediatric stone disease. In this review, we present the current research on risk factors, emerging new technologies for treatment of stones and recent investigations on prevention of stones in this population.

Is cerebral palsy associated with successful ureteral access during the initial attempt at ureteroscopy for urolithiasis in children and young adults?

BACKGROUND

Ureteroscopy is a common treatment for urolithiasis, but initial ureteral access is not always possible, particularly in pediatrics. Clinical experience suggests that neuromuscular conditions such as cerebral palsy (CP) may facilitate access, thus avoiding the need for pre-stenting and staged procedures.

OBJECTIVE

We sought to determine if probability of successful ureteral access (SUA) during initial attempted ureteroscopy (IAU) is higher in pediatric patients with CP vs. without CP.

STUDY DESIGN

We reviewed IAU cases for urolithiasis (2010-2021) at our center. Patients with pre-stenting, prior ureteroscopy, or urologic surgical history were excluded. CP was defined using ICD-10 codes. SUA was defined as scope access to urinary tract level sufficient to reach stone. Association of CP and other factors with SUA were evaluated.

RESULTS

230 patients (45.7% male, median age: 16 years [IQR: 12-18 y], 8.7% had CP) underwent IAU, with SUA in 183 (79.6%). SUA occurred in 90.0% of patients with CP vs. 78.6% of those without CP (p = 0.38). SUA was 81.7% in patients >12 years (vs. 73.8% in those <12), and the highest SUA was in those >12 years with CP (93.3%), but these differences were not statistically significant. Renal stone location was significantly associated with lower SUA (p = 0.007). Among patients with renal stone only, SUA in those with CP was 85.7% vs. 68.9% in those without CP (p = 0.33). SUA did not differ significantly by gender or BMI.

CONCLUSIONS

CP may facilitate ureteral access during IAU in pediatric patients, but we were unable to show a statistically significant difference. Further study of larger cohorts may demonstrate whether CP or other patient factors are associated with successful initial access. Improved understanding of such factors would help preoperative counseling and surgical planning for children with urolithiasis.

Nephrolithiasis management and outcomes in pediatric patients with limited mobility

INTRODUCTION AND OBJECTIVES

Pediatric patients with limited lower extremity mobility may be at increased risk of developing nephrolithiasis due to bone mineral metabolic derangements. This study sought to assess whether nephrolithiasis management and related outcomes differ between ambulatory versus non-ambulatory pediatric patients.

METHODS

This was a retrospective review of ambulatory and non-ambulatory pediatric patients with nephrolithiasis from 2010 to 2021 from a single tertiary care center. Demographics, surgical history, stone compositions, and 24-h urine data were reviewed. Adjusted logistic and linear regression models were utilized to assess whether mobility status was associated with nephrolithiasis-related management and outcomes, including: age at first stone; requiring surgical intervention for stones; number of surgeries; stone compositions; urine culture results; and completion of 24-h urine studies.

RESULTS

Among 339 pediatric patients with nephrolithiasis, 67 (19.8%) were non-ambulatory. In adjusted analyses, non-ambulatory patients had 3.24 times greater odds of requiring surgical intervention for stones (95% CI: 1.93-6.84; p < 0.0001); among those who required surgery, non-ambulatory patients required an average of 0.82 more surgical interventions (95% CI: 0.35-1.30; p = 0.0008) than ambulatory patients. Additionally, non-ambulatory patients had 5.28 times greater odds of having a positive urine culture at the time of surgery (95% CI: 2.35-14.08; p = 0.0001) and were significantly less likely to undergo 24-h urine studies (OR: 0.35; 95% CI: 0.15-0.83; p = 0.02). Stone composition significantly varied by mobility status, with non-ambulatory patients being significantly more likely to form calcium apatite (OR: 5.1; 95% CI: 2.18-11.93; p = 0.0002) or struvite (OR 3.72; 95% CI: 1.18-11.74; p = 0.03) stones, and significantly less likely to form calcium oxalate stones (OR: 0.19; 95 CI: 0.08-0.47; p = 0.0003). Among all patients, age at first stone occurred at a median age of 13.4 years (IQR: 8.2-16.4) and did not significantly differ by mobility status (p = 0.92).

CONCLUSIONS

Patients with limited mobility required surgery for nephrolithiasis at significantly higher rates and had different stone compositions than ambulatory patients. Obtaining a 24-h urine study in patients with comorbidities affecting ambulation was uncommon, compared to ambulatory patients. Similarly to ambulatory patients, pediatric patients with limited mobility who develop nephrolithiasis tend to first present with stones in early adolescence.

Preliminary analysis of serum electrolytes and body mass index in patients with and without urolithiasis

OBJECTIVES

To compare body mass index (BMI); serum parameters; and urine parameters between patients with and without urolithiasis.

METHODS

Data from 1164 patients admitted to our Department of Urology from January 2011 to July 2013 were retrospectively reviewed; 714 patients (age, 5-87 years; male:female ratio, 1.8:1) exhibited urolithiasis, and 450 patients (age, 12-94 years; male:female ratio, 3.8:1) did not. Blood and urine were collected from patients the morning after hospital admission. Serum and urine parameters were checked by an automatic biochemistry analyzer. Statistical analysis included the Mann-Whitney U test and binary logistic regression.

RESULTS

Serum sodium, potassium, chloride, calcium, phosphorus, and carbon dioxide combining power significantly differed between groups. In male patients, serum sodium, calcium, and phosphorus levels were higher in the urolithiasis group, whereas serum potassium and urine pH levels were lower. In female patients, serum sodium was higher in the urolithiasis group. BMI was higher in the urolithiasis group in all patients, male and female. Respective β-values of serum sodium and BMI in male patients were 0.077 and 0.084; in female patients, these values were 0.119 and 0.102.

CONCLUSIONS

Changes in serum sodium and BMI may be involved in the pathogenesis and treatment of urolithiasis.

Drug-Induced Urolithiasis in Pediatric Patients

Drug-induced nephrolithiasis is a rare condition in children. The involved drugs may be divided into two different categories according to the mechanism involved in calculi formation. The first one includes poorly soluble drugs that favor the crystallization and calculi formation. The second category includes drugs that enhance calculi formation through their metabolic effects. The diagnosis of these specific calculi depends on a detailed medical history, associated comorbidities and the patient's history of drug consumption. There are several risk factors associated with drug-induced stones, such as high dose of consumed drugs and long duration of treatment. Moreover, there are some specific risk factors, including urinary pH and the amount of fluid consumed by children. There are limited data regarding pediatric lithogenic drugs, and hence, our aim was to perform a comprehensive review of the literature to summarize these drugs and identify the possible mechanisms involved in calculi formation and discuss the management and preventive measures for these calculi.

Comparison of Risk Factors for Pediatric Kidney Stone Formation: The Effects of Sex

Background: Urinary stones are affecting more children, and pediatric stone formers have unique pathophysiology compared to adults. While adult stone formers are most frequently male, children have an age dependent sex prevalence. Under 10 years, a majority of stone formers are boys; adolescent stone formers are mostly female. Previous adult studies have shown that stone composition is influenced by the sex and age of the stone former. Thus, we hypothesize that female and male stone forming children will also have sex and age specific stone phenotypes. Methods: Retrospective chart review of a large pediatric center's stone forming children 6/1/2009 to 6/1/2016. Patients were identified by ICD 9 codes: N20, N20.1, and N20.9. Charts were reviewed for radiographic evidence of stones or documented visualized stone passage. Results: One hundred and thirty six subjects: 54 males and 82 females. Females were older, median age 14 years [interquartile range (IQR): 11, 15] vs. males' median age 12 years (IQR: 11, 14) (p < 0.01). Females had lower height z-scores, median 0.2 (IQR: -0.8, 0.8) vs. males' median 0.8 (IQR: -0.2, 1.8) (p < 0.01). Presenting symptoms were similar except flank pain affecting 39% of females vs. 22% of males (p = 0.04). Leukocyte esterase was positive in more females than males (33 vs. 4%) (p < 0.001). Males had a higher BUN/Cr ratio, mean ± standard deviation of 19.8 ± 6.3 vs. 16.6 ± 6.5 in females (p = 0.01). Glomerular hyperfiltration was present in 9% of patients while 35% of patients had estimated glomerular filtration rate (eGFR) < 90 ml/min/1.73 m². Treatment strategies and clinical course were similar except females were told to increase dietary citrate more frequently than males (21 vs. 4%) (p < 0.01). Conclusion: We have provided a novel analysis and demonstrated that low height z-score and pyuria are more common in female stone formers. We have also shown that 9% of pediatric stone formers have labs consistent with hyperfiltration. Whether high protein intake and/or chronic dehydration are associated with hyperfiltration and long-term renal function in children with kidney stones will be an area for future research.