A RARE CASE OF HYPOVOLEMIC HYPONATREMIA IN A PATIENT WITH EXCESSIVE BILIARY TRACT LOSS

Abstract

INTRODUCTION/BACKGROUND
Hyponatremia is the most common electrolyte abnormality observed among inpatients in the hospital setting. Severe hyponatremia (defined as serum sodium <125 mmol/L) is associated with significant morbidity and mortality. Hypovolemic hyponatremia occurs in the context of extracellular fluid depletion. Therefore, accurate diagnosis and judicious fluid therapy are essential in managing patients with hypovolemic hyponatremia. We report a case who developed severe hypovolemic hyponatremia following the insertion of a percutaneous transhepatic biliary drain for pancreatic head cancer.

CASE
A 66-year-old female with type-2 diabetes mellitus and hypertension was diagnosed with carcinoma of the head of the pancreas. The patient underwent percutaneous transhepatic biliary drainage (PTBD), which involved inserting a pigtail to facilitate biliary drainage. She presented with a 2-day history of altered behaviour and lethargy. Her Glasgow Coma Scale (GCS) was E4V3M5 and serum sodium level was 112 mmol/L. Prior to PTBD insertion, the patient had a baseline sodium level of 133 mmol/L. The patient’s PTBD output ranged from 300 mL to 1400 mL daily. Furthermore, the patient’s serum osmolarity was 252 mOsm/kg, her urine osmolarity was 331 mOsm/ kg, and her urine sodium was 21 mmol/L, which indicated hypovolaemic hyponatremia. She was initially managed with isotonic fluid (NaCl 0.9%) replacement, and her serum sodium improved to 130 mmol/L. However, the patient's IVD regime was not adjusted to account for PTBD drain output, resulting in fluctuating serum sodium levels ranging from 107 to 119 mmol/L. The patient’s bile fluid was sent for analysis, which revealed a sodium level of 119 mmol/L. She was restarted on IVD (NaCl 0.9%) for 4 pints to normalise her serum sodium level while waiting for surgery and oncology therapy.

CONCLUSION
Biliary tract loss is a rare cause of hypovolemic hyponatremia. It is important to recognize it in order to plan for appropriate fluid replacement.