of serum sodium following pericardiocentesis. Case presentationA 78-year-old female patient was admitted at the Internal Medicine Department of our hospital due to symptoms of generalized weakness, fatigue, confusion and dyspnea. On her clinical examination the patient was disoriented in time and space, with bilateral peripheral edema, diminished lung sounds at the basal fields of the lungs and muffled heart sounds. Her medical history included uterine cancer eight years ago treated with hysterectomy and radiotherapy, bilateral hip replacement, hypertension and two episodes of bowel obstruction.During laboratory examination, she was found to suffer severe hyponatremia with sodium levels at 107 (normal range: 135-145 mmol/L) along with increased liver enzymes: ALP 235 U/L (normal range: 30-120), AST 116 U/L (normal range: 3-32 U/L), γGT 113 U/L (normal range: 9-38). An abdominal ultrasound was performed that revealed ascites, liver hyperemia and normal kidney dimensions. Her chest x-ray was remarkable for increased cardiothoracic index and bilateral pleural effusions. Performed ECG revealed sinus rhythm. The patient was receiving hydrochlorothiazide, which was at first thought could be the reason for her hyponatremia.Urine osmolarity and urine sodium were 453 mOsm/ kg (normal range: 300-900) and 95 mmol/L (normal range: 27-147) respectively. During her hospitalisation, the patient experienced an episode of Acute Pulmonary