Endocrine Abstracts

Hyponatremia may manifest with nausea, disorientation, seizures, coma, cerebral edema and even death. The etiology of hyponatremia as paraneoplastic syndrome has been attributed most often to high levels of vasopressin. Correction of hyponatremia is usually successful at moderately low sodium levels, although it must be done slowly to prevent osmotic demyelination. Gastrointestinal stromal tumors (GISTs) rarely present paraneoplastic reactions, a few cases have been reported.

An 81 year-old man presented with anemia (HGB=8.5 g/dl), mild hyponatremia (Na=128 mEq/l) and low Plasma Osmolality (273 mmOsm/l). A CT scan showed a large mass originating from the gastric wall, without gastrointestinal obstruction or distant metastases. A tumor, 12 cm in diameter, was completely removed by proximal gastric resection. Histological examination diagnosed a GIST.

During post-operative period, the patient developed arrhythmia, pneumonia, vomit and confusion, requiring recovery in intensive care unit. Blood sample evaluation showed severe hypotonic hyponatremia (Na=114 mEq/l, Plasma Osmolality=239 mOsm/l) and worsening anemia. Red blood cell transfusion, antibiotics and supportive care were administered. Treatments to correct hyponatremia (water restriction and hypertonic saline) weren’t effective, with persistent and symptomatic hyponatremia. Treatment with tolvaptan 15 mg started 30 days after surgery once daily for five consecutive days. Natremia have gradually reached 130 mEq/l, and plasma osmolality 282 mOsm/l; the treatment was continued weekly for 4 months, and then monthly for 2 months. Tolvaptan treatment was necessary to maintain natremia within normal value. Drug withdrawal occurred six months from the start, with stable normal natremia. PETscan performed 2 months after surgery showed abnormal uptake in the stomach, of uncertain significance. Because of patient’s poor performance status a watchful waiting approach was preferred continuing tolvaptan treatment. PETscan performed 4 months after surgery showed a decreased uptake. After 15 months, the patient is well and free from disease.

Vaptans may be useful and safety to treat hypotonic hyponatremia associated with paraneoplatic syndrome.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.