Recurrent Transient Pseudohypoaldosteronism After Subtotal Colectomy and Ileostomy

Abstract

Introduction: Pseudohypoaldosteronism(PHA) has elevated aldosterone with hyponatremia, hyperkalemia and metabolic acidosis due to inability of aldosterone to cause potassium and hydrogen secretion. There are three types of PHA, the primary inherited types I, II and secondary. Secondary PHA is mostly due to urinary tract infection or obstruction that leads to a transient resistance to aldosterone in renal tubular cells. Rarely, transient PHA occurs due to excessive salt and water loss from a high output ileostomy. We report a case of recurrent PHA after subtotal colectomy and ileostomy. Case description: A 92-year-old woman with PMH of HTN, DM, hypothyroidism and subtotal colectomy with end ileostomy due to prior diverticular bleed presented with high output from ostomy and lethargy. Physical examination revealed BP: 63/41mm Hg, HR: 72/min with poor skin turgor. She was found to have hyponatremia (130 meq/L), hyperkalemia (> 7 meq/L), metabolic acidosis (bicarbonate 13 meq/L), and Acute Kidney Injury (AKI). She had 3 prior admissions where she had similar clinical features and laboratory values which resolved after hydration. Her urine sodium(Na): 26 mmol/L (low), urine potassium(K): 77 mmol/L (< 30 is low). Stool Na: 68 mmol/L (normal ≈ 30), K: 31 mmol/L (normal ≈ 75). Cortisol, ACTH, TSH and free T4 were normal. Plasma renin activity was high at 16.97 ng/mL/hr (normal 0.5-3) and aldosterone was high at 31.4 ng/dL (normal 0-30). IV saline normalized her electrolytes, creatinine and aldosterone levels. PHA was diagnosed and family was educated about adequate fluid and salt intake. Discussion: Patients with colonic resection have significant salt and water depletion, compensated by reduced urinary Na. In high output ostomy, this adaption suffers and kidneys are unable to excrete K due to tubular Na deficiency. However, in our patient, urine K was high implicating colon's role in electrolyte disturbances. Colon is rich in mineralocorticoid receptor and after its resection, when Na and water absorption becomes critically low, aldosterone cannot maintain normal electrolytes due to an incompletely understood mechanism and leads to PHA. Hyponatremia, hyperkalemia and metabolic acidosis in adults is usually due to adrenal insufficiency or hypoaldosteronism, but rarely in patients with ileostomy, it is due to PHA. It is critical to identify PHA since the treatment is with hydration and salt supplementation and not mineralocorticoid replacement.