Introduction

Hyponatremia is a common electrolyte disorder resulting from an excess of total body water relative to total body sodium [1]. It is defined as a serum sodium concentration below 135 mEq/L [2]. Based on the extracellular fluid volume status, the etiology of hyponatremia can be categorized as hypovolemic, euvolemic, or hypervolemic [3]. Causes of hypovolemic hyponatremia, where the decrease in total body water is less than the decrease in total body sodium, include gastrointestinal fluid losses such as diarrhea or vomiting, diuretic therapy, third-space losses such as pancreatitis, hypoalbuminemia, or small bowel obstruction, cerebral salt-wasting syndrome, salt-wasting nephropathies, mineralocorticoid deficiency, and osmotic diuresis [4]. Among the unusual causes of hypovolemic hyponatremia, percutaneous biliary drainage has been reported [5-7].

In this report, we describe a 78-year-old male patient with symptomatic hyponatremia that occurred five days after the placement of a percutaneous biliary drainage catheter to relieve obstructive jaundice due to liver metastases of lung cancer.