Endocrine Abstracts

Introduction: Hyponatremia is a frequently encountered electrolyte disturbance in clinical practice. The etiology should be searched and revisited properly to be able to guide the appropriate management.

Case-report: A 39-years old woman with type 1. diabetes since childhood, after combined pancreas-kidney transplantation with good stable functions of both organs, was admitted to our internal ward for overall fatigue, fever, unspecific abdominal pain with nausea, suspect urinary infection. In a month she lost 5 kilos on weight and was slightly dehydrated. Laboratory findings at the admission: natrium 122 mmol/mol, kalium 3.9 mmol/mol, chlorides 92 mmol/mol, pH 7.366, bicarbonate 25 mmol/l, total protein 62 g/l, albumin 31 g/l, CRP 72 mg/l, urea 7 mmol/mol, creatinine 127 umol/l, CKD-EPI 0.76 ml/s- stable renal function since transplantation, liver-pancreatic tests normal, euglycemic, mild leukocytosis with a left shift, haemoglobin 98 g/l, thrombocytes in norm, urine smear was clear. Chest X-ray was normal, abdominal ultrasound detected slightly distended small intestine with retroperitoneal and mesenteric lymphadenopathy, on a CT scan the maximal diameter of the lymphadenopathy was 13 mm. After rehydration and empiric antibiotic therapy, no proven microbiological agent was detected and a tendency to hyponatremia 125 mmol/mol persisted with subfebrile temperatures. Hypocortisolism was ruled out and chronic levothyroxine substitution for autoimmune thyroiditis was slightly increased to 150 ucg daily as TSH was 14 mIU/l, fT4 11 pmol/l. With suspicion of a malignancy associated syndrome of inappropriate antidiuretic hormone secretion (SIADH) a PET/CT scan was performed and meanwhile, salt tablets were administered at home. The scan revealed pathology in small intestine mostly in left mesogastrium with intraperitoneal nodules max. diameter 35 mm. The clinical status of the patient worsened rapidly in 14 days leading to readmission for cachexia, fevers, natrium 118 mmol/mol, chlorides 89 mmol/mol, CRP 170 mg/l. Hypertonic saline was administered and due to lack of peripheral lymphadenopathy, negative blood flow cytometry, negative colono/gastroscopy a surgical laparotomy was performed in the abdomen to reach the final diagnosis- diffuse large B cell lymphoma. The patient was referred to the hematooncological department.

Conclusion: Hyponatremia is sometimes overlooked by clinicians, even though it could serve as a warning sign. In our case malignancy associated SIADH due to a posttransplant lymphoproliferation with B-symptoms was found.