Potassium is the most common intracellular cation. Approximately 98% of total potassium exists in the intracellular fluid (ICF), which has a normal range of  140–150 mEq/l. Merely 2% of this cation is placed in the extracellular fluids (ECF), where it ranges from 3.5 to 5 mEq/l. Potassium is essential during numerous body functions, particularly for excitable cells such as muscle and nerve cells. Any disorder of potassium serum levels can disturb the transmembrane potential and renders excitable cells (nerve and muscle) hyperpolarized and less sensitive. However, cardiac cells don't obey this rule and become hyperexcitable. Potassium regulation is essential to maintain a normal activity in cells. Any impairment in potassium serum levels will have severe consequences on several organs especially the heart and the nervous system. Typically, total potassium excretion in the stool is low and most ingested potassium is absorbed. The kidney is the primary regulator of potassium balance through excretion (the kidney excretes 90-95% of dietary potassium); the gut excretes a minimal amount of dietary potassium (approximately 10%).
Hypokalemia pathophysiology
Hyperkalemia pathophysiology
Hyponatremia pathophysiology
Hyperkalemia risk factors
Hypernatremia pathophysiology
Renal papillary necrosis risk factors
Hypokalemia differential diagnosis
Acute tubular necrosis risk factors