The prevalence of urolithiasis in adults is approximately 5.2%, with an incidence rate of 1.5%. In industrialized countries, it is estimated that individuals experience at least one episode of urolithiasis during their lifetime [1]. Urolithiasis is incidentally detected in 15% to 40% of cases, often asymptomatically, suggesting that the actual prevalence may be higher. Additionally, the prevalence is reported to be approximately twice as high in men compared to that in women [1].

In children, the prevalence of urolithiasis is on the rise. While the rates vary depending on the race and socioeconomic conditions, the prevalence is reportedly approximately 10% of that observed in adults [2]. Unlike adults, in whom lifestyle factors, such as metabolic syndrome, obesity, physical inactivity, and inadequate fluid intake are the major contributors, urolithiasis in children is more commonly associated with metabolic, genetic disorders, or congenital urological anomalies [3]. Therefore, when evaluating a patient suspected of urolithiasis, it is essential not only to confirm the diagnosis through imaging, but also to identify the underlying causes and risk factors. This includes assessing the family history, conducting metabolic and genetic testing, and analyzing 24-hour urine collections and stone composition. Such a comprehensive approach can inform the development of targeted treatment and preventive strategies [4].

Primary hyperparathyroidism (pHPT) is an exceptionally rare condition in children and adolescents. A Korean study identified only two pediatric cases among 17 patients diagnosed with pHPT (11.7%) [5]. The symptoms reported in pediatric patients include epigastric pain, knee pain [5], chest pain, headache [6], skeletal complications from low bone mineral density [7,8], abdominal pain due to pancreatitis, and acute flank pain caused by ureteral stones [8]. Herein, we report a recent case of pHPT presenting as bilateral renal stones in a 13-year-old boy.

The patient was a 13-year-old boy who presented with the primary complaint of abdominal pain. The symptoms began 1 day prior to his emergency room visit on September 2, 2024. His relevant medical history includes chronic rhinitis, a deviated septum, and prior admissions for respiratory infections, specifically bronchiolitis and pneumonia, at 3 years of age. In August 2024, occult blood was detected during the national student health examination system. However, the finding was not considered serious at the time, and the patient did not seek medical attention. During the recent acute presentation, the patient reported abdominal pain localized around the umbilical area. The patient had no fever, diarrhea, or other gastrointestinal complaints. The patient's height and weight were 152.2 cm (12.5 percentile), and 45.1 kg (21.2 percentile), respectively. The vital signs were as follows: blood pressure, 128/62 mmHg; pulse rate, 78 beats per minute; respiratory rate, 22 times per minute; and body temperature, 36.4 ℃. Upon physical examination, diffuse abdominal tenderness was observed, without tenderness over the costovertebral angles. An initial erect abdominal radiograph revealed tiny high-density lesions in both kidneys (Fig. 1). Laboratory findings included the following: white blood cell count, 9,200/µL (segmental neutrophils, 46.0%; lymphocytes, 38.0%); hemoglobin, 12.5 g/dL; hematocrit, 37.7%, platelets, 348,000/µL; albumin, 4.3 g/dL; total protein, 6.6 g/dL; total bilirubin, 0.2 mg/dL; aspartate aminotransferase, 22 IU/L; alanine aminotransferase, 17 IU/L; blood urea nitrogen, 12.3 mg/dL; creatinine (Cr), 0.67 mg/dL; sodium, 139 mmol/L; potassium, 3.9 mmol/L; uric acid, 8.5 mg/dL; total calcium, 10.5 mg/dL; and phosphorus, 3.2 mg/dL. The erythrocyte sedimentation rate was 13 mm/hr, and the C-reactive protein level was 0.01 mg/dL. The urinalysis results were as follows: specific gravity, 1.022; pH, 6.5; protein, 1+; red blood cells, many/high-power field (HPF); and white blood cells, 20–29/HPF. The urine protein to Cr ratio was 0.13 mg/mg Cr. The random urine calcium to Cr ratio was 187.6 mg/g. The urine N-acetyl-beta-D-glucosaminidase-to-Cr ratio was 14.89 IU/g, and the urine β2-microglobulin level was 0.30 mg/dL. An additional non-contrast computed tomography scan was performed to confirm the diagnosis. Computed tomography of the kidney and bladder revealed a stone measuring 0.5×0.8 cm in the right distal ureter with hydronephrosis as well as multiple small calyceal stones in both kidneys (up to 0.5×0.6 cm) (Fig. 2). The patient's 24-hour urine collection, performed shortly after admission and prior to extracorporeal shock wave lithotripsy (ESWL), was analyzed. The 24-hour urine citric acid level was 109 mg/day, which is below the normal range (>150 mg/day), while the calcium level was 77.76 mg/day, within the normal range. After ESWL for bilateral renal stones, the retrieved stone fragments were subjected to composition analysis using the wet chemical method. The analysis identified calcium, oxalate, uric acid, phosphate, and magnesium, indicating a mixed-type stone, primarily composed of calcium oxalate and calcium phosphate, which are commonly associated with hypercalciuria and hypocitraturia. These findings support a metabolic etiology, consistent with the diagnosis of pHPT. After 3 weeks, follow-up laboratory findings showed a further increase in serum calcium to 13.0 mg/dL (normal range, 8.6–10.2 mg/dL), with alkaline phosphatase elevated to 2,232 IU/L (normal range, 276–855 IU/L). The intact parathyroid hormone (iPTH) level was markedly elevated at 296.2 pg/mL (normal range, 10–65 pg/mL), while the 25-hydroxy vitamin D level was low at 13.5 ng/mL (normal range, 30–100 ng/mL). Technetium-99m sestamibi parathyroid scintigraphy identified a parathyroid mass at the anterior portion of the right thyroid gland (Fig. 3). Genetic testing for the MEN1 gene revealed no mutations. The patient was transferred to another hospital for surgical treatment, and a calcium-sensing receptor agonist, such as cinacalcet, was administered while awaiting surgery. Eventually, the patient underwent a successful parathyroidectomy, leading to normalization of calcium and iPTH levels postoperatively.

pHPT is relatively more prevalent in adults and is frequently identified incidentally owing to asymptomatic hypercalcemia. Conversely, pHPT is an uncommon condition in the pediatric population, occurring in approximately 2 to 5 cases per 100,000 children [9]. Among children, nearly 90% of pHPT cases are associated with musculoskeletal manifestations, including bone pain, structural deformities, and fractures. Hypercalcemia, a defining characteristic of pHPT, often presents with symptoms, such as abdominal discomfort, appetite loss, fatigue, nausea, vomiting, and constipation. Notably, approximately half of the pediatric patients with pHPT also experience nephrolithiasis as a significant complication [10-12].

The relationship between nephrolithiasis and kidney function is intricate and bidirectional. Impaired kidney function can predispose individuals to stone formation by disrupting calcium and phosphate metabolism, reducing uric acid excretion, and lowering the citrate levels [13]. Conversely, the presence of urinary stones can lead to complications, such as hydronephrosis, renal parenchymal damage, and urinary tract infections, initiating a vicious cycle that exacerbates renal dysfunction [14]. In pediatric patients with urinary stones, a comprehensive metabolic and systemic evaluation is essential—even in cases involving a single stone—to prevent recurrence and protect long-term renal function. Identifying urinary tract infections and underlying metabolic abnormalities plays a crucial role in both etiologic assessment and prevention of future stone formation [15].

Treatment strategies should be individualized based on several factors, including stone size, location, symptom severity, comorbid conditions, and anatomical considerations. Small ureteral stones (≤10 mm) are often managed conservatively with adequate hydration and pain control. When appropriate, medical expulsive therapy using α-blockers may be considered to facilitate stone passage. For patients with identified metabolic abnormalities, dietary modification and pharmacologic interventions are essential. Pharmacologic therapy is tailored to the specific metabolic disturbance, such as thiazide diuretics for hypercalciuria, potassium citrate for hypocitraturia, and allopurinol for hyperuricosuria [16,17]. Surgical intervention is indicated for symptomatic stones, stones unlikely to pass spontaneously, cases where conservative management fails, or when there is a risk of urinary obstruction, infection, or renal impairment. Among surgical options, minimally invasive approaches are preferred. Ureteroscopy is recommended for ureteral stones and renal stones smaller than 20 mm, offering high stone-free rates (up to 95% for small stones). ESWL is a noninvasive and commonly used method that provides a relatively simple procedure with a short hospital stay and a low risk of complications. Percutaneous nephrolithotomy is typically reserved for large renal stones (>20 mm) and should be performed by experienced surgical teams [16,17].

In this case, the patient had multiple bilateral renal stones and a right distal ureteral stone associated with hydronephrosis. Given the stone burden and location, ESWL was selected as the initial treatment modality. This aligns with current pediatric urolithiasis treatment guidelines, which recommend ESWL as a safe and effective option for renal and upper ureteral stones in children. Combined with laboratory findings of high PTH and hypercalcemia, the successful retrieval and analysis of stone fragments following ESWL facilitated the diagnosis of pHPT as the underlying metabolic etiology. This highlights the importance of not only treating the stones but also addressing the underlying etiology to prevent recurrence.

The American Urological Association guidelines recommend including iPTH testing in the metabolic workup of nephrolithiasis to rule out pHPT, especially in initial presentations [16]. The Canadian Urological Association guidelines also recommend an in-depth metabolic evaluation for patients with risk factors for recurrent stone disease, for example, such as pediatric patients, those with a family history of urolithiasis, bilateral stones, or non-calcium stones [17]. Hypercalcemia and elevated iPTH levels are often interpreted as secondary hyperparathyroidism due to impaired renal function. However, in this case, imaging studies showed no evidence of reduced kidney size, and there is no clear evidence of renal dysfunction; hence, pHPT should be considered as a differential diagnosis. This necessitates additional diagnostic modalities, such as parathyroid scans or ultrasonography. Approximately 10% of pHPT cases are linked to genetic conditions, including familial hypocalciuric hypercalcemia, multiple endocrine neoplasia, familial isolated pHPT, and neonatal severe hyperparathyroidism. The prevalence of these genetic associations is notably higher in pediatric patients as compared to that in adults, making genetic testing a critical component of the diagnostic process [9,18].

The treatment of choice for pHPT is surgical removal of the lesion, and in most patients, the serum calcium and iPTH levels returned to a normal range after parathyroidectomy [9].

In some patients with higher calcium levels, Cinacalcet, an oral calcimimetic agent, or intravenous bisphosphonates may be used as an interim treatment to reduce the risk of complications associated with hypercalcemia while preparing for surgery [19].

This case underscores the importance of considering pHPT as an underlying cause in pediatric patients presenting with nephrolithiasis. A comprehensive metabolic evaluation, including iPTH measurement, is essential for accurate diagnosis and effective management. Genetic testing can provide additional insight into the etiology, particularly in children, where hereditary factors are more prevalent. An early diagnosis and timely intervention can prevent long-term complications, such as chronic kidney disease and skeletal deformities, ensuring better patient outcomes.