Renal salt wasting syndrome in a patient with COVID-19; a case report and review of the literature

Introduction: Cerebral salt wasting or renal salt wasting (RSW) syndrome, may be more common than syndrome of inappropriate antidiuretic hormone secretion (SIADH) and may even occur in the absence of cerebral disease. We report a case of RSW in a Bangladeshi patient positive for COVID-19 without clinical cerebral disease. Case Presentation: A 53 years-old Bangladeshi patient presented with history of chest pain and acute MI. On examination, the patient was conscious, alert, vitally stable, chest with fine bilateral basal crepitation and heart with additional S3 sound and abdomen was lax with no organomegaly. There was no lower limbs oedema. His serum creatinine; 68 umol/L, urea; 3.4 mmol/L, K; 4.7 mmol/L, sodium; 135 mmol/L, uric acid; 141 mmol/L and phosphate was 1.3 mmol./L. Echocardiography (ECG) revealed anterior lateral wall STEMI. PCI was done for LAD. ECG revealed ejection fraction (EF) 10-15 %. Nasopharyngeal swab for COVID-19 was positive. Serum sodium decreased from 135 to 108 with signs of hypovolemia. Work up for hyponatremia revealed serum osmolality of 237 mOsm/kg, urine NA; 109 mmol/L, urine osmolality; 295 mOsm/kg, urine uric acid; 685 umol/L, and urine phosphate; 6.5 mmol/L. Additionally serum T3, T4, TSH and serum basal cortisol were normal. The patient received normal saline infusion and fludrocortisone and serum sodium increased to 134 mmol/L. Our patient had all the important clinical and laboratory characteristics of RSW in the absence of cerebral disease which include hyponatremia associated with hypovolemia, high urinary sodium excretion, increased fraction excretion of phosphate and persistent hypouricemia with increased fractional excretion of urate after correction of hyponatremia and with normal renal, adrenal and thyroid functions. Furthermore, there was a prompt response to saline replacement and fludrocortisone and steady improvement in serum sodium with negativity and improvement of COVID-19. Our diagnosis was RSW in the absence of cerebral disease and to our knowledge; this is the first case of RSW in a patient with COVID-19 in the literature. Conclusion: RSW should be considered in patients with COVID-19 with hyponatremia and absence of cerebral disease. We suggest changing cerebral salt wasting to the more appropriate term RSW.