Pathophysiology of potassium absorption and secretion by the human intestine

Rajiv Agarwal, Rekha Afzalpurkar, John S. Fordtran

Research output: Contribution to journalArticle

118 Citations (Scopus)

Abstract

When normal people ingest 90 mEq/day of K+ in their diet, they absorb about 90% of intake (81 mEq) and excrete an equivalent amount of K+ in the urine. Normal fecal K+ excretion averages about 9 mEq/day. The vast majority of intestinal K+ absorption occurs in the small intestine; the contribution of the normal colon to net K+ absorption and secretion is trivial. K+ is absorbed or secreted mainly by passive mechanisms; the rectum and perhaps the sigmoid colon have the capacity to actively secrete K+, but the quantitative and physiological significance of this active secretion is uncertain. Hyperaldosteronism increases fecal K+ excretion by about 3 mEq/day in people with otherwise normal intestinal tracts. Cation exchange resin by mouth can increase fecal K+ excretion to 40 mEq/day. The absorptive mechanisms of K+ are not disturbed by diarrhea per se, but fecal K+ losses are increased in diarrheal diseases by unabsorbed anions (which obligate K+), by electrochemical gradients secondary to active chloride secretion, and probably by secondary hyperaldosteronism. In diarrhea, total body K+ can be reduced by two mechanisms: loss of muscle mass because of malnutrition and reduced net absorption of K+; only the latter causes hypokalemia. Balance studies in patients with diarrhea are exceedingly rare, but available data emphasize an important role for dietary K+ intake, renal K+ excretion, and fecal K+ losses in determining whether or not a patient develops hypokalemia. The paradoxical negative K+ balance induced by ureterosigmoid anastomosis is described. The concept that fecal K+ excretion is markedly elevated in patients with uremia as an intestinal adaptation to prevent hyperkalemia is analyzed; we conclude that the data do not convincingly show the existence of a major intestinal adaptive response to chronic renal failure.

Original languageEnglish (US)
Pages (from-to)548-571
Number of pages24
JournalGastroenterology
Volume107
Issue number2
StatePublished - 1994
Externally publishedYes

Fingerprint

Intestines
Diarrhea
Potassium
Hyperaldosteronism
Hypokalemia
Cation Exchange Resins
Hyperkalemia
Uremia
Intestinal Absorption
Sigmoid Colon
Rectum
Malnutrition
Small Intestine
Chronic Kidney Failure
Anions
Mouth
Chlorides
Colon
Urine
Diet

ASJC Scopus subject areas

  • Gastroenterology

Cite this

Pathophysiology of potassium absorption and secretion by the human intestine. / Agarwal, Rajiv; Afzalpurkar, Rekha; Fordtran, John S.

In: Gastroenterology, Vol. 107, No. 2, 1994, p. 548-571.

Research output: Contribution to journalArticle

Agarwal, R, Afzalpurkar, R & Fordtran, JS 1994, 'Pathophysiology of potassium absorption and secretion by the human intestine', Gastroenterology, vol. 107, no. 2, pp. 548-571.
Agarwal, Rajiv ; Afzalpurkar, Rekha ; Fordtran, John S. / Pathophysiology of potassium absorption and secretion by the human intestine. In: Gastroenterology. 1994 ; Vol. 107, No. 2. pp. 548-571.
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