A hypokalaemic woman with nephrocalcinosis: rebirth of old knowledge

The coexistence of hypokalaemia and nephrocalcinosis poses a challenge in rapid diagnosis and appropriate management. We describe a 38-year-old woman who presented with thirst, intermittent carpopedal spasm, paresthaesia of both hands and progressive weakness of lower extremities for two years. She had a history of chronic hypokalaemia of unknown cause with intermittent potassium supplementation for 7-8 y and bilateral nephrocalcinosis notable for one year. She denied vomiting, diarrhoea or use of laxatives, alcohol or diuretics. Her blood pressure was normal. Laboratory investigations showed hypokalaemia (2.7 mmol/L) and metabolic alkalosis (HCO3- 32.6 mmol/L, pH 7.46). Two random urine samples both showed a consistently high urine K+ excretion but with excretion rates of Na+, Cl- and divalent cations which were high in one sample but not the other. Ingestion of furosemide 120 mg daily for body image for 7-8 y was uncovered. With furosemide cessation and potassium supplementation, her hypokalaemia with neuromuscular symptoms was corrected but nephrocalcinosis persisted. Surreptitious use of diuretics for various purposes should be kept in mind as an important cause of hypokalaemia and/or nephrocalcinosis. Measurement of electrolyte concentrations in at least two random urine samples is warranted to distinguish it from true renal tubular disorders and extrarenal causes.