Contributors of Campbell-Walsh-Wein, 12th edition
Gregory E. Tasian, and Lawrence A. Copelovitch
Epidemiology of pediatric kidney stone disease
The incidence of nephrolithiasis has increased over the past several decades 5%–10% per year for children. Among all pediatric age groups, the greatest increase is among adolescents, particularly females. Girls have a higher frequency of stones compared with boys. In adults, approximately 75%–80% of stones are calcium oxalate, 5% are calcium phosphate, 10%–20% are struvite, and 5% are pure uric acid. Children have a similar distribution of stones, with calcium phosphate stones being slightly more common and uric acid stones being less common. The notion that most stones that form during childhood are caused by rare genetic causes, inborn errors of metabolism, or infection is not true. Patients who develop kidney stone disease during childhood are at risk for development of comorbidities such as decreased bone mineral density, chronic kidney disease, and heart disease.
Evaluation
Evaluation of child with suspected nephrolithiasis
Ultrasound is the initial imaging study recommended for children with suspected nephrolithiasis reserving a noncontrast computed tomography (CT) scan for children with a nondiagnostic ultrasound in whom the clinical suspicion for stones remains high. The criteria for defining a stone on ultrasound are (1) hyperechoic focus in the renal papillae, calyces, or renal pelvis and (2) confirmatory twinkle artifact ( Fig. 8.1 ). Although historically the presence of a posterior acoustic shadow was a necessary diagnostic criterion for a kidney stone, modern harmonic and spatial compounding ultrasound technology does not generate shadows as readily, particularly for stones less than 4 mm. Ultrasound has >70% sensitivity and >95% specificity for detecting urinary tract stones, including stones located in the mid-ureter.
Noncontrast CT has nearly 100% sensitivity and specificity to identify kidney stones. CT, however, delivers ionizing radiation, which is associated with an increased risk for malignancy. Although the attributable risk for cancer from a single CT scan performed for kidney stones is small (0.2%–0.3% above baseline), the cumulative risk is higher for those undergoing repeated studies. When necessary (e.g., stone not visualized on ultrasound but with secondary signs of obstruction such as hydronephrosis), a low-dose noncontrast CT of the abdomen and pelvis should be performed ( Fig. 8.2 ).
Medical history
A focused dietary history with special emphasis on fluid and salt intake, vitamin (A, C, D) and mineral supplementation, and special diets (e.g., ketogenic diet) is indicated in every patient. A detailed medication history with special emphasis on corticosteroids, diuretics (furosemide, acetazolamide), protease inhibitors (indinavir), antibiotics and antiepileptics (e.g., topiramate) should also be obtained. Children with a history of prematurity, urinary tract abnormalities, urinary tract infections (UTIs), intestinal malabsorption, and prolonged immobilization are at increased risk for developing stones.
Metabolic investigation
Children with a metabolic abnormality have a fivefold increased risk for recurrence compared with children with no metabolic disorder. Consequently, some believe all children should undergo a comprehensive metabolic evaluation. The need for such an analysis after a child’s first kidney stone has become somewhat controversial, as the composition of pediatric kidney stones have become similar to that seen in adults. An analysis should be performed of a passed or retrieved stone. Further metabolic evaluation could include serum and urine studies in patients in whom stone analysis could not be performed or for those with either calcium or uric acid–based stones. A serum creatinine may be used to evaluate for acute kidney injury or chronic kidney disease. Serum calcium, phosphorous, bicarbonate, magnesium, and uric acid levels are effective in screening for hypercalcemia/hypocalcemia-associated calculi. A 24-hour urine collection will evaluate urinary levels of calcium, oxalate, uric acid, sodium, citrate, cystine, creatinine, as well as urinary volume and pH.
Urine metabolic abnormalities
Hypercalciuria is found in 30%–50% of children. The most common cause of hypercalicuria in both children and adults is idiopathic hypercalciuria. Increased urinary oxalate excretion may be caused by an inherited metabolic disorder (primary hyperoxaluria) or, more commonly, as a secondary phenomenon caused by increased oxalate absorption or excessive intake of oxalate precursors. Gastrointestinal absorption varies inversely with dietary calcium intake, and, as a result, calcium-deficient diets may increase oxalate absorption and hyperoxaluria. Cystinuria is an autosomal recessive disorder, resulting in disordered amino acid transport in the proximal tubule. In spite of the higher uric acid excretion observed in children, uric acid nephrolithiasis is rather rare in childhood, accounting for <5% of all renal calculi. Hyperuricosuria in the setting of low urinary pH is the greatest risk factor for uric acid stone formation.
There may be other inborn metabolic diseases that may also lead to pediatric stone formation. A summary of such conditions is included in Table 8.1 .
| CONDITION | INHERITANCE PATTERN/GENETIC CAUSE | PRESENTING SYMPTOMS | MEDIAN PRESENTING AGE | TYPE OF STONE FOUND | MEDICAL TREATMENT |
|---|---|---|---|---|---|
| Primary hyperoxaluria | Autosomal recessive; Defect of hepatic AGT enzyme | Renal calculi, nephrocalcinosis, renal impairment, hyperoxaluria, hyperglycoluria | 5–6 years; Can be first detected as infant or into adulthood | Calcium oxalate | High fluid intake, potassium or sodium citrate, orthophosphate, pyridoxine, liver/kidney transplantation |
| Cystinuria | Autosomal recessive | Renal calculi | Second to third decades of life | Cystine | High fluid intake, limited salt intake, urinary alkalinization, low-protein diet, chelators |
| Phosphoribosyl pyrophosphate (PRPP) synthetase superactivity | X-linked inheritance | Usually young males, gouty arthritis, nephrolithiasis | Childhood | Uric acid | Allopurinol |
| Hypoxanthine-guanine phosphoribosyl transferase (HGPRT) deficiency Lesch-Nyhan syndrome | X-linked inheritance | Neurologic manifestations, self-mutilation, hyperuricemia, hyperuricosuria | Childhood | Uric acid | Allopurinol |
| Adenine phosphoribosyl transferase (APRT) deficiency | Autosomal recessive | Nephrolithiasis | Early childhood | 2,8-Dihydroxyadenine (DHA) | Allopurinol, high fluid intake, dietary purine restriction |
| Xanthine-oxidase (XOD) deficiency | Mutations of 2p22 | Nephrolithiasis, myopathy, low plasma levels of uric acid | 5 years | Xanthine | Low purine diet, high fluid intake |
| Glycogen storage disease Type 1 (GSD-1) | Autosomal recessive | Hepatomegaly, short stature, osteoporosis, hypoglycemia, lactacidemia, hyperlipidemia, hypercalciuria, hypocitraturia, hyperuricemia | Childhood with increasing incidence with age | Calcium | Oral citrate therapy, salt reduction, metabolic control of acidosis |
| Dent disease | X-linked recessive | Nephrolithiasis, proteinuria, hypercalciuria, rickets, hypotonia, cataracts | Early childhood | Calcium | Thiazides, ACE inhibitors |
| Familial primary hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) | Autosomal recessive | Nephrolithiasis, polyuria, polydipsia, failure to thrive, seizures, muscular tetany, rickets, severe ocular involvement | 1–8 years of age | Calcium | Magnesium supplements, thiazides, renal transplant |
Management of children and adolescents with kidney and ureteral stones
Medical expulsion therapy
Medical expulsion therapy (MET) is the use of α-blockers or, less commonly, calcium-channel blockers to facilitate passage of a ureteral stone. The mechanism for MET in increasing stone passage is that type 1a and 1d α-receptors are found in high concentrations in the smooth muscle of the distal third of the ureter and at the ureterovesical junction. Spontaneous stone passage without MET is higher among older patients and for smaller (<5 mm) and more distal ureteral stones. The American Urological Association (AUA) and Endourological Society Guideline for the surgical management of urinary stones recommends that pediatric patients with uncomplicated ureteral stones ≤10 mm should be offered “observation with or without MET using α-blockers” (Grade B Level of Evidence).
Surgical management
Options for surgical management.
Up to 60% of children with kidney or ureteral stones require surgery. Surgical options for pediatric patients include ureteroscopy (URS), shock wave lithotripsy (SWL), and percutaneous nephrolithotomy (PCNL), all of which require anesthesia and, traditionally, radiation exposure. A recent review reported stone clearance ranging from 70%–97% for PCNL, 85%–88% for URS, and 80%–83% for SWL. The choice of intervention is determined primarily by the size and location of the stone, patient anatomy, and patient (and provider) preference ( Table 8.2 )
| RECOMMENDATION | STRENGTH OF RECOMMENDATION | LEVEL OF EVIDENCE |
|---|---|---|
| In pediatric patients with uncomplicated ureteral stones <10 mm, clinicians should offer observation with or without medical expulsive therapy using α-blockers | Moderate: net benefit or harm moderate | B: Moderate certainty |
| Clinicians should offer URS or SWL for pediatric patients with ureteral stones who are unlikely to pass the stones or who failed observation and/or MET, based on patient-specific anatomy and body habitus | Strong: net benefit or harm substantial | B: Moderate certainty |
| Clinicians should obtain a low-dose CT scan on pediatric patients before performing PCNL | Strong: net benefit or harm substantial | C: Low certainty |
| In pediatric patients with ureteral stones, clinicians should not routinely place a stent before URS | Panel consensus, based on members’ clinical training, experience, knowledge, and judgment for which there is no evidence. | Expert opinion |
| In pediatric patients with a total renal stone burden ≤20 mm, clinicians may offer SWL or URS as first-line therapy | Moderate: net benefit or harm moderate | C: Low certainty |
| In pediatric patients with a total renal stone burden >20 mm, both PCNL and SWL are acceptable treatment options. If SWL is utilized, clinicians should place an internalized ureteral stent or nephrostomy tube | Panel consensus, based on members’ clinical training, experience, knowledge, and judgment for which there is no evidence | Expert opinion |
| In pediatric patients, except in cases of coexisting anatomic abnormalities, clinicians should not routinely perform open, laparoscopic, or robotic surgery for upper tract stones | Panel consensus, based on members’ clinical training, experience, knowledge, and judgment for which there is no evidence | Expert opinion |
| In pediatric patients with asymptomatic and nonobstructing renal stones, clinicians may utilize active surveillance with periodic ultrasonography | Panel consensus, based on members’ clinical training, experience, knowledge, and judgment for which there is no evidence | Expert opinion |
Related posts:
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Principles of urologic surgery: Perioperative management
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Evaluation of the urologic patient: History, physical examination, laboratory tests, imaging, and hematuria workup
Congenital anomalies of the upper urinary tract: UPJ obstruction, duplication anomalies, ectopic ureter, ureterocele, and ureteral anomalies
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