Factors regulating sodium balance in proctocolectomized patients with various ileal resections.

Patients subjected to proctocolectomy together with an ileal resection will lose increased amounts of sodium with the ileostomy excreta and may develop sodium and water depletion. Studies of sodium balance and measurements of renin activity, aldosterone, and arginine vasopressin in plasma were made in 23 such patients, 8 of them under metabolic-ward conditions while receiving various salt loads. Salt loss never resulted in subnormal sodium levels in serum. The earliest sign of salt depletion was a nearly total inhibition of renal sodium excretion, which could precede activation of the renin-aldosterone axis in these patients. Secretion of vasopressin remained unaffected by sodium-water depletion and by activation of the renin system. The routine monitoring of these patients should include measurements of renal sodium excretion. Measurement of renin and aldosterone levels should be used for evaluation of the severity of a sodium deficiency.