What Predicts Recurrent Kidney Stone After Parathyroidectomy in Patients with Primary Hyperparathyroidism?

Kidney stone disease (KSD) is the most common clinical manifestation in patients who present with symptomatic primary hyperparathyroidism (PHPT). The definitive treatment for PHPT is parathyroidectomy, which results in the normalization of serum calcium and parathyroid hormone (PTH) levels and should diminish the risk of recurrent kidney stone formation. However, some patients with PHPT and KSD continue to form kidney stones despite successful parathyroidectomy, defined as normalization of serum calcium six months after surgery. The goal of this retrospective single-center study was to identify risk factors for recurrent KSD in a large group of known stone-formers with PHPT. We found that, despite curative parathyroidectomy, 23% (16/69) of stone formers with PHPT develop stone recurrence, and younger age appears to be the only significant predictor of recurrent nephrolithiasis post-parathyroidectomy.

Among PHPT patients, those with kidney stones tend to be younger, have higher body mass index (BMI), consist of a higher proportion of men, and are more likely to exhibit multi-gland disease compared to PHPT patients without stone disease. To better understand the etiology of recurrent KSD after parathyroidectomy, we examined whether urinary metabolic abnormalities, such as persistent hypercalciuria, low urinary volume, high urinary pH, and/or hypocitraturia, may explain the sustained increased risk of stone disease. We specifically examined the following 24-hour urine parameters in our study population: volume, pH, calcium, oxalate, citrate, uric acid, sodium, and creatinine. Although 24-hour urine calcium excretion decreased across all patients from 378 ± 209 mg/day preoperatively to 236 ± 128 mg/day postoperatively (p<0.0001), more than half of the patients (37/69) had persistent hypercalciuria post-parathyroidectomy. Interestingly, urine calcium excretion was similar in patients with and without stone recurrence pre-parathyroidectomy and decreased to a similar degree in both groups post-parathyroidectomy. Similarly, other urine metabolic parameters pre- and post-operatively did not differ significantly between recurrent stone formers and non-recurrent stone formers.

Practicing urologists should be vigilant about recurrent stone formation in their PHPT patients who have undergone curative parathyroidectomy, especially the younger ones. Our recommendation is to closely monitor these patients after surgery with both post-parathyroidectomy serum calcium and PTH as well as 24-hour urine studies, as the latter can help guide treatment for any additional abnormalities in accordance with the AUA guidelines on medical management of kidney stones.

While nearly a quarter of patients with PHPT and KSD have a stone recurrence after successful parathyroid surgery, we still recommended parathyroidectomy, as the majority do appear to be cured of their stone disease after parathyroid surgery. Further prospective studies are needed to better understand who is at risk for stone recurrence post-parathyroidectomy.

Written by: Ana K Islam, MD,¹ Shelby Holt, MD, FACS,¹ Joan Reisch, PhD,² Fiemu Nwariaku, MD, FACS,¹ Jodi Antonelli, MD,³ and Naim M Maalouf, MD⁴

Department of Surgery, UT Southwestern Medical Center, Dallas, Texas
Population and Data Sciences, UT Southwestern Medical Center, Dallas, Texas
Department of Urology, UT Southwestern Medical Center, Dallas, Texas
Department of Internal Medicine and Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, UT Southwestern Medical Center, Dallas, Texas

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