What is Hyperkalemia?

Hyperkalemia

Author: Eleanor Lederer, MD, Consulting Staff, Louisville VA Hospital; Professor of Medicine; Interim Chief of Nephrology; Director of Nephrology Training Program; Director, Metabolic Stone Clinic; Director of Outpatient Clinics, Kidney Disease Program, University of Louisville School of Medicine
Coauthor(s): Rosemary Ouseph, MD, Professor of Medicine, Director of Kidney Transplant, University of Louisville School of Medicine; Vibha Nayak, MD, Assistant Professor of Nephrology, Director of Home Dialysis, Kidney Disease Program, University of Louisville; Son Dinh, MD, Nephrologist, Southland Renal Medical Group, Inc
Contributor Information and Disclosures

eMedicine from WenMD: Mar 19, 2010

Introduction

Background

Potassium homeostasis
Hyperkalemia is defined as a condition in which serum potassium greater than 5.3 mEq/L.

Potassium, the most abundant intracellular cation, is essential for the life of the organism. Potassium is obtained through the diet. Common potassium-rich foods include meats, beans, fruits, and potatoes. Gastrointestinal absorption is complete, resulting in daily excess intake of about 1 mEq/kg/d (60-100 mEq). This excess is excreted through the kidneys (90%) and the gut (10%). Potassium homeostasis is maintained predominantly through the regulation of renal excretion. The most important site of regulation is the distal nephron, including the distal convoluted tubule, the connecting tubule, and the cortical collecting tubule, where aldosterone receptors are present.

The regulation of potassium excretion at the cortical collecting tubule has been extensively studied. Sodium reabsorption through epithelial sodium channels (ENaC) located on the apical membrane of cortical collecting tubule cells, is driven by aldosterone and generates a tubular lumen negative electrical potential, driving the secretion of potassium at this site through specific potassium channels called the renal outer medullary K channels (ROMK). Studies have demonstrated, however that aldosterone also regulates sodium transport in the thick ascending limb of the loop of Henle, the distal convoluted tubule, and the connecting tubule.

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