Exploring Water-free Sodium Storage

Inclusion Criteria: * ESRD Patients actively undergoing PD with a reliably functioning PD catheter * Systolic blood pressure \> 130 mmHg * Serum sodium \>135 mmol/L * daily urine output \< 400ml * stable PD prescription for at least 2 months without requirement of 4.25% glucose PD solution * PD vintage of at least 6 months * Euvolemic as defined by the patient at their dry weight and free of any signs or symptoms of volume overload, per referring nephrologist Exclusion Criteria: * Poorly controlled diabetes with hemoglobin A1C\>9% * 1 or more episodes of peritonitis in the previous 6 months or active infection of the peritoneal dialysis catheter * Anemia with hemoglobin \<8g/dL * Inability to give written informed consent or follow study protocol. * Urinary incontinence * Body weight \< 60kg * gastrointestinal disease that causes diarrhea or expectation of sodium losses in stool. * use of amiodarone in the last 6 months (which will interfere with tissue iodine ascertainment).