Basics
Description
- Urolithiasis is the occurrence of calculi (stones) within the urinary tract, including the kidney, ureter, or bladder.
- Stones may be composed of calcium oxalate, calcium phosphate, uric acid, cystine, magnesium ammonium phosphate, xanthine, indinavir, and triamterene.
Epidemiology
The incidence of stones in children of both sexes has increased over the last 25 years.
Risk Factors
- Poor fluid intake
- Immobility
- Urinary tract obstruction
- Urinary tract infection (Proteus mirabilis or Escherichia coli)
- Bladder augmentation
- Dumping syndrome
- In children, 50% have a metabolic syndrome associated with urolithiasis.
- 75% have a metabolic predisposition to forming stones.
Pathophysiology
- The urine contains multiple solutes; some help prevent crystallization and some contribute to crystal formation.
- The likelihood of a solute crystalizing varies with the pH of the urine (e.g., uric acid crystal formation is more likely at lower pH).
- When enough crystals form in the urine and urine flow out of the kidney is slow or obstructed
- Crystals then coalesce into a small nidus upon which more crystals will form. This process then leads to stone formation.
Commonly Associated Conditions
Children who present with urolithiasis younger than age 6 years are more likely to develop hypertension (HTN) and diabetes mellitus (DM) later in life.
Diagnosis
History
- Sudden or gradual onset of flank pain
- Location of stone is guided by the pain.
- Midabdominal or suprapubic pain may indicate ureteral location of stone.
- Testicular or labial pain indicates the stone is near the ureteral orifice.
- Younger children are more likely to have nonspecific and/or nonlocalized pain.
- Nausea and/or vomiting
- Vague midabdominal pain
- Gross or microscopic hematuria is seen in only 50% of patients.
- Urinary tract infection (UTI) or fever
- Recent furosemide exposure
- Immobilization (postsurgical, wheelchair use)
Physical Exam
- +/ ’ Costovertebral angle (CVA) tenderness
- Abdominal tenderness, without rebound tenderness. Patient will have peritonitis only if a stone is accompanied by severe pyelonephritis.
- +/ ’ Restless and unable to find a comfortable position
- +/ ’ Blood in the urine
Diagnostic Tests & Interpretation
Lab
- Urinalysis and urine culture
- 24-hour urine collection for calcium, citrate, creatinine, magnesium, oxalate, pH, phosphate, and uric acid
- Basic metabolic panel including calcium, phosphorus, and uric acid
- If hypercalcuria, then obtain vitamin D and PTH levels.
- CBC: if infection suspected
Imaging
- Renal ultrasound: limited ability to visualize ureteral stones
- Plain abdominal radiograph
- CT scan of abdomen and pelvis, only if absolutely necessary
- Remember radiation ALARA goal (as low as reasonably achievable).
Differential Diagnosis
- UTI, upper or lower tract
- Appendicitis
- Gastroenteritis
- Congenital ureteropelvic junction (UPJ) obstruction
- Henoch-Sch Άnlein purpura
- Tumor
- Papillary necrosis
- Trauma
- Renal artery/vein thrombosis
- Nutcracker phenomenon
Alert
A stone causing urinary obstruction with an associated urinary tract infection is high risk and a surgical emergency.
Treatment
Medication
- Fluid
- Watchful waiting
- Consider expulsion therapy.
- Alpha-blockers: Flomax (may cause headache and hypotension) (not FDA approved)
Additional Therapies
- Surgical removal
- Ureteroscopy
- Extracorporeal shock wave lithotripsy (ESWL)
- Percutaneous nephrolithotomy (PCNL)
General Measures
- After diagnosis, referral to pediatric urology for surgical management and to pediatric urology or pediatric nephrology for complete metabolic evaluation and treatment
- Stones <3 mm may pass without surgical intervention.
- Regardless of the size, further metabolic evaluation by a specialist should occur.
Ongoing Care
Follow-up Recommendations
- All stones passed should be sent for chemical analysis.
- Increase fluid intake: Urine should be clear.
- Avoid vitamin D and C supplementation until metabolic workup is complete.
- Avoid high cranberry intake.
- Minimize sodium intake and reduce animal protein intake.
- Targeted reduction of specific foods such as oxalate-containing foods if with hyperoxaluria
Prognosis
- 1/2 " 1/3 of children with metabolic abnormality will form another stone.
- Severe hyperoxaluria is associated with primary hyperoxaluria that can cause early renal failure and may require kidney transplant to correct renal failure and simultaneous liver transplant to correct the hereditary metabolic defect.
- Cystinuria: Treatment with Thiola and D-penicillamine can be associated with myelosuppression.
Additional Reading
- Dave S, Khoury AE, Braga L, et al. Single-institutional study on role of ureteroscopy and retrograde intrarenal surgery in treatment of pediatric renal calculi. Urology. 2008;72(5):1018. [View Abstract]
- Dwyer ME, Krambeck AE, Bergstralh EJ, et al. Temporal trends in incidence of kidney stones among children: a 25-year population based study. J Urol. 2012;188(1):247. [View Abstract]
- Erturhan S, Bayrak O, Sarica K, et al. Efficacy of medical expulsive treatment with doxazosin in pediatric patients. Urology. 2013;81(3):640. [View Abstract]
Codes
ICD09
- 592.9 Urinary calculus, unspecified
- 592.0 Calculus of kidney
- 592.1 Calculus of ureter
- 594.1 Other calculus in bladder
- 594.9 Calculus of lower urinary tract, unspecified
- 594.2 Calculus in urethra
- 594.8 Other lower urinary tract calculus
- 594.0 Calculus in diverticulum of bladder
ICD10
- N20.9 Urinary calculus unspecified
- N20.0 Calculus of kidney
- N20.1 Calculus of ureter
- N21.0 Calculus in bladder
- N20.2 Calculus of kidney with calculus of ureter
- N21.1 Calculus in urethra
- N21.8 Other lower urinary tract calculus
- N21.9 Calculus of lower urinary tract, unspecified
SNOMED
- 95566004 Urolithiasis (disorder)
- 95570007 Kidney stone (disorder)
- 31054009 Ureteric stone
- 70650003 Urinary bladder stone (disorder)
- 20342001 calculus in urethra (disorder)
FAQ
- Q: When should a child with a stone be admitted for management?
- A: If the stone has obstructed a solitary kidney, if the child has an elevated white blood cell count or UTI in the setting of obstruction, and if the child is immunocompromised and shows signs of a UTI.