Login to Access Video or Poster Abstract: MP95-08
Sources of Funding: none

Introduction

Higher serum calcium (Ca) and/or parathyroid hormone (PTH) in patients with kidney stones raises the suspicion for primary hyperparathyroidism (PHPT), however the diagnosis can be challenging to confirm. We sought to determine if patients can be risk stratified regarding likelihood of PHPT based on blood and urine studies.

Methods

We queried our electronic medical record for patients with ICD-9 codes for both PHPT and kidney or ureteral stones. In an effort to identify patients with a suspicion of PHPT we also included patients with a serum Ca >9.9 mg/dL, PTH >50 pg/ml, and kidney or ureteral stones. Patients with kidney transplant or prior parathyroidectomy were excluded. From the medical record we extracted demographics, lab and urine values at presentation and at follow-up visits, parathyroid Imaging, details of parathyroidectomy, and post-operative lab values when appropriate.

Results

We divided the 147 patients into three groups based on serum Ca and PTH: classic, suspicious, and not suspicious for PHPT. The classic group (n=30) had high Ca (>10.2mg/dL) and high PTH >65 (pg/ml) simultaneously during follow-up. The suspicious group (n=53) had a Ca ≥9.9 and a PTH ≥50 simultaneously during follow-up. The non-suspicious group (n=64) never had a Ca ≥9.9 and a PTH ≥50 simultaneously during follow-up. We further subdivided the suspicious group into three groups: Group S1 (n=20) with high normal Ca (9.9-10.1mg/dL) and high normal PTH (50-64pg/ml), Group S2 with high normal Ca and high PTH (n=22), and Group S3 (n=11) with high Ca and high normal PTH. There was no significant difference in the maximum urine Ca across groups. In the classic group 100% had parathyroid imaging, 80% of which was positive. In the suspicious group 47% had imaging 52% of which was positive. Parathyroidectomy was performed in 83.3% of classic, 30% of S1, 27%, of S2, 45% of S3 and 9.4% of the not suspicious groups. Serum Ca normalized in 100% of patients who underwent surgery. The classic group had the shortest time to imaging and surgery but this did not reach significance (p=0.2).

Conclusions

Half of patients who undergo parathyroidectomy had a non-classic presentation, suggesting that we are underdiagnosing PHPT. Although both Ca and PTH are considered when making the diagnosis of PHPT, in our study group serum Ca seemed to more frequently drive the diagnosis supporting the AUA guidelines on the selective use of PTH. Efforts should be made to pursue a better diagnostic algorithm for the diagnosis of PHPT.

Funding

none