Hypercalcemia in the nephrology department patients - incidence, etiology and impact on renal function

Hypercalcemia (HCM) is predominantly caused by primary hyperparathyroidism (PHPT) or malignancy. It's incidence varies from 0.17% to 4.74%. Its numerous manifestations include renal symptoms.

The aim of the study was to assess the incidence and etiology of hypercalcemia in patients hospitalized at the Department of Nephrology of the Warsaw Military Institute, as well as to evaluate its impact on renal function.

In this cross-sectional study patients admitted to the Nephrology Department of the Warsaw Military Institute between January 2017 and December 2018 were retrospectively screened for presence of HCM, defined as total calcium level or corrected calcium level in case of hypoalbuminemia >10.2 mg/dl, measured at least twice. Each patient's medical history as well as other laboratory findings were subsequently analyzed in order to establish the etiology of hypercalcemia.

Among 3062 hospitalisations (1993 patients) at The Department, 96 patients had elevated calcium level of which 36 were identified as hypercalcemic (1,81%). Median calcium level was 11.9 mg/dl (IQR: 11.25-13.46) with 22.24 mg/dl being the maximum observed value. Malignancy and drugs having hypercalcemizing effect were the most common etiologies identified, both being found in 9 cases (25%). Other causes of HCM included sarcoidosis, multiple myeloma (analyzed separately from other malignancies), PHPT and hypercalcemic hypocalciuria. In 7 cases HCM etiology could not be established, it therefore remained idiopathic. Acute kidney injury (AKI) developed in 20 patients (56%), in this group serum calcium levels were significantly higher than in non-AKI patients (median: 12.85 mg/dl (IQR:11.82-14.65) vs 11.25 mg/dl (IQR:10.75-11.93); p=0.0039). Additionally, chronic kidney disease (CKD) patients presented significantly lower calcium values than non-CKD patients (median: 11.47 mg/dl (IQR: 10.8-12.6) vs 13.01 mg/dl (IQR:11.9-16.08; p=0.0131).

Hypercalcemia is a rare disorder among Nephrology Department patients, which primary etiology is malignancy and medications having hypercalcemizing effect. Kidney injury is dependent on the severity of hypercalcemia.