Does urinary stone composition and morphology help for prediction of primary hyperparathyroidism?

BACKGROUND

Primary hyperparathyroidism (HPT) is a common cause of urolithiasis. Only a few data are available on stone composition and morphology in HPT patients.

METHODS

We compared the composition and morphology of stones from 264 HPT patients (143 males and 121 females) and 24 567 non-HPT stone formers (16 918 males and 7649 females) including a subgroup of 1356 patients with idiopathic hypercalciuria (IH) (1049 males and 307 females). We excluded uric acid and infection stones containing struvite.

RESULTS

Calcium oxalate (CaOx) was the most prevalent crystalline species among the main components of stones in all groups. However, CaOx stones were significantly less frequent in patients with vs without HPT (51.9% vs 82.2%; P<0.0001). An inversion of CaOx crystalline phases was observed in HPT and IH patients: whewellite was predominant in 16.3% and 30.2% of cases, respectively, vs 57.4% in the non-HPT group (P<0.001), whereas weddellite was predominant in 35.6% of HPT and 49.5% of IH vs 24.8% of non-HPT stones (P<0.0001). Among calcium phosphates, brushite was 7-fold more frequent in HPT than in non-HPT patients (14.0% vs 2.2%; P<0.0001) and almost three times as frequent as in IH patients (4.9%, P<0.0001). Carbapatite was significantly more frequent in male patients with HPT vs non-HPT or IH patients (23.1% vs 8.3% and 9.9%, P<0.0001). Morphological data showed that pure type I calculi were markedly less frequent in HPT patients (1.1% vs 25.3% in non-HPT group, P<0.0001, and 9.1% in IH subgroup, P<0.001). A high occurrence of IVd calculi and of the association of types IVa and II was observed in HPT vs non-HPT and IH patients (14.4%, 2.3% and 6.3%, P<0.0001 and 58.3%, 17.2% and 29.9%, P<0.0001, respectively).

CONCLUSIONS

Our data highlight a striking increase in the proportion of calcium-dependent crystalline species, especially brushite in HPT patients, with particular morphological associations in both genders which were more marked than in IH patients.