Correspondence between Ca²⁺ and calciuria, citrate level and pH of urine in pediatric urolithiasis

Urethral Microenvironment Adapted Sodium Alginate/Gelatin/Reduced Graphene Oxide Biomimetic Patch Improves Scarless Urethral Regeneration

The nasty urine microenvironment (UME) is an inherent obstacle that hinders urethral repair due to fibrosis and swelling of the oftentimes adopted hydrogel-based biomaterials. Here, using reduced graphene oxide (rGO) along with double-freeze-drying to strengthen a 3D-printed patch is reported to realize scarless urethral repair. The sodium alginate/gelatin/reduced graphene oxide (SA/Gel/rGO) biomaterial features tunable stiffness, degradation profile, and anti-fibrosis performance. Interestingly, the 3D-printed alginate-containing composite scaffold is able to respond to Ca2+ present in the urine, leading to enhanced structural stability and strength as well as inhibiting swelling. The investigations present that the swelling behaviors, mechanical properties, and anti-fibrosis efficacy of the SA/Gel/rGO patch can be modulated by varying the concentration of rGO. In particular, rGO in optimal concentration shows excellent cell viability, migration, and proliferation. In-depth mechanistic studies reveal that the activation of cell proliferation and angiogenesis-related proteins, along with inhibition of fibrosis-related gene expressions, play an important role in scarless repair by the 3D-printed SA/Gel/rGO patch via promoting urothelium growth, accelerating angiogenesis, and minimizing fibrosis in vivo. The proposed strategy has the potential of resolving the dilemma of necessary biomaterial stiffness and unwanted fibrosis in urethral repair.

Why is childhood urolithiasis increasing? Etiology, diagnosis and management: a single-center experience

BACKGROUND

Globally, urolithiasis is becoming more and more common among children. We aimed to determine the etiology, and the diagnostic and therapeutic approaches in patients with urolithiasis.

METHODS

This was a retrospective study which included all patients (aged 1 month-18 years) admitted to the pediatric nephrology clinic in Elazığ Fethi Sekin City Hospital with urolithiasis between November 2019 and 2021. Only patients whose diagnosis of urolithiasis was confirmed by urinary ultrasonography were included in the study, while patients with chronic diseases (neurological diseases such as epilepsy, cerebral palsy, chronic bowel diseases, etc.) predisposing to kidney stone formation were not. Demographic characteristics, serum and urine biochemical parameters, urine metabolic and kidney stone metabolic and chemical analyses, urinary tract ultrasonography findings and treatment modalities were collected.

RESULTS

One hundred ninety-seven patients (91 female and 106 male) were included in the study. Hypervitaminosis D was detected in 4 (2%) patients, suppressed parathyroid hormone in 12 (6%) and hypercalcemia in 27 (14%) patients. Metabolic screening showed hypercalciuria in 69 (35%) patients, hypocitraturia in 39 (20%), hyperoxaluria in 15 (8%) and cystinuria in 6 (3%) patients. Eighty three (42%) patients had a positive family history for kidney stones. One hundred eighteen (60%) patients received potassium citrate treatment, 71 (36%) were given hydration and diet recommendations without medical treatment, 6 (3%) received tiopronin treatment, and 2 (1%) patients were treated surgically.

CONCLUSIONS

Our study suggests that Vitamin D supplementation at doses higher than 400 IU/day may be a risk factor for kidney stones in children. We observed that mothers tend not to give water to infants who are breastfed or formula-fed in the first year of life. K-citrate treatment can be a good option for prevention and dissolution of stones by alkalinization.

Medical management for the prevention of kidney stones

The alarming fact is that approximately one out of every 10 of us will have a kidney stone during our lifetime. The increasing prevalence and associated costs of kidney stones have resulted in it being one of the most commonly encountered and impactful medical conditions. Contributing factors include, but are not limited to, diet, climate, genetics, medications, activity and underlying medical conditions. Symptoms generally parallel stone size. Treatment varies from supportive to procedural (invasive and non-invasive). Prevention remains the best way to avoid this condition especially given the high recurrence rate. First time stone formers require counselling regarding dietary adjustments. Certain risk factors ultimately require a more in-depth metabolic investigation, especially if stones are recurrent. Ultimately, management is defined by stone composition. Where appropriate, we review both pharmacologic and non-pharmacologic options. Pivotal to successful prevention is patient education and the encouragement of compliance with the appropriate regimen.

Pediatric stone disease: Current management and future concepts

Treatment of pediatric urolithiasis consists of medical and surgical approaches. The main goal of the treatment is to prevent stone recurrence by avoiding multiple surgical interventions. In recent years, many innovations have been reported in the medical diagnostic evaluation protocol and in surgical treatment. According to recent reports, single mutations could be responsible for a larger proportion of renal stones. This etiologic feature holds the potential to change the management in stone prevention from metabolically directed therapy to more specific approaches. In addition, miniaturized instruments have been adopted in clinical practice. In recent years, minimally invasive endoscopic surgery is the treatment of choice in pediatric urolithiasis. This review aims to assess the current literature on medical and surgical treatment options for pediatric urolithiasis. We also aim to provide an overview of potential future advances.

A versatile probe for serum albumin and its application for monitoring wounds in live zebrafish

A versatile probe for serum albumin and its application in monitoring wounds in live zebrafish.

Role of Calcium to Citrate Ratio in Predicting Stone Formation in Idiopathic Hypercalciuria Children (2-12 Years Old)

OBJECTIVE

Considering the predictive role of the relatively low urinary citrate for stone formation, especially in hypercalciuric patients, this study is aimed at comparing urine calcium to citrate (Ca/Cit) ratio in 3 groups of children, including patients with idiopathic hypercalciuria with and without renal stone as well as the healthy children.

METHODS

This study was carried out on 96 children (2 to 12 years old) referred to a pediatric nephrology clinic in the city of Ahvaz, Southwest Iran. All the children underwent renal ultrasonography, urinalysis, and measurement of random nonfasting urine Ca, Cr, and citrate. Those with secondary hypercalciuria, urinary tract malformations, and/or functional abnormalities of the gastrointestinal tract were excluded from the study.

RESULTS

The mean Ca/Cit. ratio (mg/mg) in the three groups, including children with hypercalciuric with and without renal stones and the healthy children (control group), was 0.44 ± 0.14, 0.39 ± 0.13, and 0.19 ± 0.08, respectively, which showed a significant difference (P < .001). There was also a significant difference in Ca/Cit ratio between the first and the control group by Tukey's range test (P < .001). Mean urinary Ca/Cit ratio in those with a positive family history of urolithiasis within three groups was 0.42 ± 0.17 and in those with a negative family history was 0.32 ± 0.16 (P = .013). Mean Ca/Cit. ratio (mg/mg) of 0.25 showed a sensitivity of 90.6% (confidence interval: 75.7-96.7%) and a specificity of 81.2% (confidence interval: 64.7-91.1%) to differentiate between the renal stone group and the control group.

CONCLUSION

High Ca/Cit ratio can predict stones formation in hypercalciuric patients, especially in those with a positive family history of urolithiasis. The present study found the cutoff level of 0.25 for Ca/Cit. ratio as the highest prognostic value for renal stone formation.

Hypocitraturia Is an Untoward Side Effect of Synthetic Human Parathyroid Hormone (hPTH) 1-34 Therapy in Hypoparathyroidism That May Increase Renal Morbidity

Subcutaneous human parathyroid hormone (hPTH) therapy can effectively manage hypocalcemia in hypoparathyroidism, with varying effects on hypercalciuria. However, little is known about its ability to decrease the renal comorbidities of hypoparathyroidism: nephrocalcinosis (NC), nephrolithiasis (NL), and renal insufficiency. Urinary citrate (Ucit) promotes the solubility of urinary calcium (UCa); hypocitraturia is a risk factor for NC/NL. Twenty-four-hour UCa, Ucit, and UCa/Ucit were determined in 31 hypoparathyroid subjects receiving hPTH 1-34 therapy for up to 5 years. Before hPTH 1-34, the geometric least squares mean UCa was 346 mg/day (normal <250) and Ucit was 500 mg/day (normal 250-1190); UCa/Ucit was 0.67 mg/mg. After 6 months of hPTH 1-34, UCa decreased (238, p < 0.001), but with a greater decrease in Ucit (268, p < 0.001), increasing UCa/Ucit, which became significant over time (p < 0.001). After stopping hPTH 1-34 and resuming conventional therapy (follow-up; FU), compared to the last measures on hPTH 1-34, Ucit rose to 626 (p < 0.001), reducing UCa/Ucit to 0.44, (p < 0.05); UCa also rose (273), but was still lower than baseline (p < 0.05). Daily hPTH 1-34 dose did not correlate with UCa, but was inversely related to Ucit, and directly related to UCa/Ucit (p < 0.01). Mean blood bicarbonate decreased significantly on hPTH 1-34 and remained lower than baseline at FU (p < 0.01). Mean eGFR increased on hPTH 1-34 (86 to 96 mL/min/1.73 m² , p < 0.001) and returned to baseline at FU. On renal imaging, 6 subjects did not have NC/NL, 8 had NC/NL prior to hPTH 1-34 that remained unchanged, and 16 developed new-onset (n = 10) or progressive (n = 6) NC/NL while on hPTH 1-34. Our data demonstrate that treatment with subcutaneous hPTH 1-34 may have an untoward effect of hypocitraturia and high UCa/Ucit ratio that may increase renal morbidity. With increasing use of PTH therapy in hypoparathyroidism, close monitoring and exploration for treatment of hypocitraturia seem warranted. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Dyslipidaemia in overweight children and adolescents is associated with an increased risk of kidney stones

AIM

There is conflicting evidence about the role of obesity in paediatric nephrolithiasis. This Polish study explored the influence of nutritional status and lipid disturbances on urinary lithogenic factors and the risk of kidney stone formation in children and adolescents from three to 18 years of age.

METHODS

We carried out serum lipid profile evaluations and 24-h urine chemistry analyses on 493 overweight/obese paediatric participants (mean age 13 years) without nephrolithiasis and 492 healthy normal weight sex and age-matched controls.

RESULTS

A third (33%) of the study group had blood lipid disturbances, with more acidic urine, lower urinary citrate excretion and a higher fraction of ionised calcium and higher Bonn Risk Index than the controls. The participants' body mass index standard deviation score (BMI Z-score) was positively correlated with urinary oxalate and uric acid and negatively correlated with citrate excretion. Total cholesterol, low-density lipoprotein cholesterol and triglycerides correlated negatively with citraturia, while high-density lipoprotein cholesterol correlated positively.

CONCLUSION

The main factor that predisposed overweight and obese children to kidney stones was hypocitraturia. Urinary citrate excretion was related to both BMI Z-scores and all lipid fraction abnormalities. However, hypercholesterolaemia and particularly low-density lipoprotein hypercholesterolaemia seemed to play a major role.

Urinary calcium excretion in children with monosymptomatic enuresis

Background

Among many factors predisposing to monosymptomatic enuresis (MNE) disturbances in urinary electrolites excretion play an important role. Because of many controversies in this field there is a need to debate the role of hypercalciuria in MNE. The aim of our study was to determine the urinary calcium in children with MNE.

Methods

The investigation was conducted on 204 children (83 MNE children and 121 reference group). Urinary calcium excretion (in 24-h collection and per kg of body mass), Ca/creatinine ratio, Ca²⁺ in urine sample and in 24-h collection of urine were estimated.

Results

Hypercalciuria in MNE group was diagnosed in 18/83 (21.69 %) patients. We found statistically significant differences between children with MNE in Ca²⁺ in urine sample and 24-h collection and Ca/creat. ratio. Median urinary calcium excretion (mg/kg/24-h and mmol/24-h) was significantly higher in hypercalciuric enuretic patients. The urinary total calcium (mmol/24-h), urinary bound calcium and urinary calcium concentration (mmol/L) demonstrated a significant positive correlation with height, weight and age in reference group but not in MNE group.

Conclusion

Urinary calcium excretion was significantly disturbed and further studies are needed to assess the role of hypercalciuria in the pathogenesis of MNE.

Urinary citrate excretion in healthy children depends on age and gender

BACKGROUND

Hypocitraturia is considered a major risk factor for calcium stone formation. However, there is no widely accepted reference database of urinary citrate excretion in children. The aim of our study was to determine the amount of citrate eliminated in the urine over a 24-h period in a pediatric cohort and to determine an optimal unit reflecting excretion.

METHODS

The study cohort comprised 2,334 healthy boys and girls aged 2-18 years. The levels of urinary citrate were assessed by an enzymatic method in 24-hour urine and expressed in absolute values, as urinary concentration, citrate/creatinine ratio, per kilogram of body weight, in relation to 1.73 m2, and as the calcium/citrate index.

RESULTS

Similar incremental age-related citraturia rates were observed in both male and female subjects until puberty during which time citrate excretion became significantly higher in girls. Urinary citrate adjusted for creatinine and for body weight showed a significantly decreasing trend with increasing age in both sexes. Urinary citrate corrected for body surface was weakly correlated with age. Thus, the assumption of 180 mg/1.73 m2/24 h for males and 250 mg/1.73 m2/24 h for females as lower cut-off values appeared to be reliable from a practical perspective.

CONCLUSIONS

We found distinct sex-dependent differences in citraturia at the start of puberty, with significantly higher values of urinary citrate in girls than in boys. Further prospective studies are warranted to elucidate whether this difference represents a differentiated risk of urolithiasis.