The Kidneys and Calcium Metabolism

The kidneys may be affected in several ways, directly or indirectly, in sarcoidosis. They may be infiltrated by granulomas, but these rarely cause symptoms or signs. The most frequent cause of impairment of renal function in sarcoidosis is the hypercalcaemia that occurs in a minority of patients and may cause a nephropathy, at first reversible but later leading to irreversible and possibly progressive changes. In many cases with this hyper-calcaemic nephropathy, granulomas are also present in the kidneys, and it is thus appropriate to consider renal changes and the disordered calcium metabolism together.