Diagnosis and treatment of pediatric kidney stones

by Travis Groth, MD, and Charles Durkee, MD

Travis Groth, MD, uses ureteroscopy and holmium laser lithotripsy to view a ureteral stone in a Children's Hospital of Wisconsin patient.
Travis Groth, MD, uses ureteroscopy and holmium laser lithotripsy to view a ureteral stone in a Children's Hospital of Wisconsin patient.
Travis Groth, MD, is a pediatric urologist at Children's Hospital of Wisconsin. He also is an assistant professor of Pediatric Urology at The Medical College of Wisconsin and a member of Children's Specialty Group.

Charles Durkee, MD, is a pediatric urologist at Children's Hospital of Wisconsin. He also is an associate professor of Pediatric Urology at The Medical College of Wisconsin and a member of Children's Specialty Group.

The lifetime prevalence of developing kidney stones in the U.S. has been reported at between 10-15 percent1, 2. Recent studies have suggested that the incidence of urinary stones in the pediatric population is increasing3. Although there continues to be some debate on this, urinary stones in children can cause significant morbidity and can be challenging for physicians to diagnose and treat.

Stones are formed in the urinary system by a series of events that lead to crystal formation and growth, which then proceed to stone development. Factors such as poor hydration, genitourinary anomalies, genetic factors and metabolic disorders can promote this process. In adults with urolithiasis, there is a male predominance. However, in children, boys and girls are affected equally.

For common symptoms of urinary stones see Table 1. Older children will demonstrate localizing symptoms of costovertebral angle tenderness or abdominal pain on the affected side. These symptoms can be less specific in younger children. Some renal stones are incidentally diagnosed on workup for urinary tract infections.

The majority of stones in children are composed of either calcium phosphate or calcium oxalate, independently or in combination. Other rare causes of stones in children include uric acid, cystine or struvite stones4.

The initial workup for a child with renal colic symptoms should include a urinalysis and urine culture to assess for hematuria and infection. In certain situations, a basic metabolic panel and complete blood count is indicated to assess for infection and metabolic abnormalities. The diagnosis of renal stones is made from radiologic imaging – abdominal X-ray (KUB), renal ultrasonography or helical CT scan. The most sensitive and specific method for diagnosing a urinary stone is an unenhanced helical CT scan, which has a reported sensitivity and specificity greater then 96 percent5. In patients that are ill or present acutely and may require urgent treatment, a CT scan should be performed. At Children's Hospital of Wisconsin, we routinely will obtain a low-dose-mode stone protocol CT scan that significantly reduces the radiation exposure without reducing the sensitivity of stone diagnosis in these patients.

After a stone has been diagnosed, it must be decided if it warrants emergent or urgent treatment. Stones 3-5 mm in size can spontaneously pass in children 60-85 percent of the time, and smaller stones have an even greater chance of passing6. Recent studies have demonstrated that á-blockers both increase the incidence of spontaneous stone passage and provide symptomatic pain relief7. This has been studied extensively in adult patients with ureteral stones. Although not as extensively studied in children, there are several studies demonstrating the efficacy and safety of tamsulosin in the pediatric population.

For indications for treatment for urinary stones see Table 2. The surgical treatment options include extracorporeal shock wave lithotripsy (ESWL), ureteroscopy and holmium laser lithotripsy and percutaneous nephrolithotripsy (PCNL). The treatment used for urinary stones usually depends more on stone size, location and composition than the age of the patient. Because of advancements in technology, the treatment for urinary stones in pediatric patients has evolved from open procedures to the same endourologic and minimally invasive treatment options used in adults.

ESWL dramatically changed how renal stones were treated in adult patients in 1984. It has been shown to be both safe and effective in pediatric patients.

Due to the significant minimization of endourologic instruments, ureteroscopy with holmium laser lithotripsy has become more prevalent as the primary treatment for both ureteral and renal stones in children. This procedure has the added benefit of allowing the surgeon to directly treat the renal or ureteral stones along with removing the stone fragments during the same procedure. ESWL and ureteroscopy with laser lithotripsy routinely are performed as outpatient procedures unless there are unusual circumstances. (See Figure 1)

PCNL is reserved for larger renal stones (typically greater than 2 cm) or patients with complex anatomy precluding ureteroscopy or passage of fragments. Access to the renal collecting system is performed percutaneously and then a rigid or flexible nephroscope is used. Patients that undergo PCNL are admitted to the hospital for treatment.

After treatment of urinary stones, children are evaluated for predisposing metabolic abnormalities with a basic chemistry panel and frequently with a 24-hour urine analysis along with assessment for anatomical abnormalities. Since children have a high lifetime recurrence rate for urinary stones, they are followed closely. This is done most commonly with renal ultrasounds and urine analysis assessing for hematuria to help to decrease radiation exposure.

References

  1. Johnson CM, et al. Renal Stone Epidemiology: A 25-year Study in Rochester, Minnesota. Kidney Int. 1979. 16(5): p. 624-31.
  2. Norlin A, et al. Urolithiasis. A Study of its Frequency. Scand J Urol Nephrol. 1976. 10(2): p. 150-3.
  3. Sas DJ, et al. Increasing Incidence of Kidney Stones in Children Evaluated in the Emergency Department. J Pediatr. 157(1): p. 132-7.
  4. VanDervoort K, et al. Urolithiasis in Pediatric Patients: A Single Center Study of Incidence, Clinical Presentation and Outcome. J Urol. 2007. 177(6): p. 2300-5.
  5. Palmer JS, et al. Diagnosis of Pediatric Urolithiasis: Role of Ultrasound and Computerized Tomography. J Urol. 2005. 174(4 Pt 1): p. 1413-6.
  6. Pietrow PK, et al. Clinical Outcome of Pediatric Stone Disease. J Urol. 2002. 167 (2 Pt 1): p. 670-3.
  7. Singh A, HJ Alter, Littlepage A. A Systematic Review of Medical Therapy to Facilitate Passage of Ureteral Calculi. Ann Emerg Med. 2007. 50(5): p. 552-63.

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