Discussion

Malignant biliary obstruction is common in patients with advanced malignant tumors, leading to poor prognosis and hindering antitumor therapy [8]. In the setting of malignant biliary obstruction due to unresectable malignant tumors, the placement of percutaneous biliary catheters for drainage may be helpful in relieving obstructive symptoms [9]. Although percutaneous transhepatic biliary drainage is a safe and effective way to relieve jaundice caused by advanced inoperable malignant disease [9], procedure-related complications could be observed, such as infectious complications, occlusion or dislocation of drainage, and bile leakage [10]. Moreover, after the placement of a percutaneous biliary catheter in a patient, the importance of fluid and electrolyte replacement has been emphasized in the past [11]. Bile is a physiological aqueous solution produced and secreted by the liver in quantities of approximately 600 mL per day. It consists mainly of bile salts, phospholipids, cholesterol, conjugated bilirubin, electrolytes, and water [12]. The concentration of inorganic solutes (sodium, potassium, calcium, and bicarbonate) in bile is similar to that in plasma and accounts for the bile osmolality of approximately 300 mOsm/kg [13]. Bile has a high sodium concentration, similar to that of plasma, which is essential for bile’s tonicity [14]. After the placement of percutaneous biliary drainage, bile salt reabsorption in the gut, which prevents sodium wasting, is lacking, and a routine daily diet cannot replace external sodium losses in some cases [6].

Indeed, our patient developed dehydration and severe hyponatremia after the percutaneous procedure, which manifested with weakness, fatigue, nausea, and two episodes of vomiting. The patient had a hypovolemic condition, although he did not report diarrhea, sweating, diuretic use, or other causes of hypovolemic hyponatremia. As the urine sodium concentration was less than 20 mmol/L, sodium wasting was considered extrarenal. Initially, gastrointestinal sodium wasting due to vomiting was suspected, but there were only two episodes that stopped soon after. The drainage fluid assessment results supported the occurrence of sodium wasting through biliary drainage. Although the average biliary output of approximately 700 mL/day would not generally be classified as high-output drainage, the measured sodium concentration of 133 mEq/L resulted in daily sodium losses of approximately 93 mEq. This corresponds to approximately 2.1 g of elemental sodium or 5.4 g of sodium chloride, which is close to the maximum daily salt intake recommended by current dietary guidelines. Furthermore, information regarding the patient’s fluid intake, urine output, and biliary drainage volume prior to admission was unavailable. Therefore, it is possible that sodium and fluid losses at home were even greater than those documented during hospitalization, contributing to the development of hypovolemia, acute kidney injury, and severe hyponatremia.

In a previous report, Subasinghe et al. presented a case of hilar cholangiocarcinoma in a 62-year-old man who experienced persistent severe hyponatremia despite salt replacement during external biliary drainage prior to surgery. Sodium levels were restored to normal after nasojejunal refeeding [5].

In another case, a 76-year-old female patient suffering from an inoperable Klatskin tumor presented with kidney dysfunction and hyponatremia due to daily sodium losses of 164 mmol via biliary drainage fluid that exceeded one liter per day. Her sodium levels were restored and remained stable after adding sodium as oral salt supplementation to the patient’s diet [6]. Likewise, Yassine et al. reported a case of a 51-year-old man with an obstructive Klatskin tumor who developed hyponatremia and functional renal failure after high-volume biliary excretion following external biliary drainage. The authors concluded that external biliary drainage can cause serious hydroelectrolytic complications, particularly during high biliary flows, due to the significant loss of water and solutes through the biliary drain. This condition can result in hyponatremia and circulatory insufficiency, which is the cause of functional renal failure [7].