Yes! Constipation may be an important contributor to hyperkalemia in some patients with chronic kidney disease (CKD).

 Under normal conditions, 80-90% of excess dietary potassium (K⁺) is excreted by the kidneys, with the remainder excreted through the GI tract.¹ However, in advanced CKD, particularly in the setting of end-stage kidney disease (ESKD), the GI tract assumes a much more important role in maintaining K⁺ balance. 

As early as 1960’s, the daily fecal excretion of K⁺ was found to be directly related to the wet stool weight, irrespective of creatinine clearance. Furthermore, K⁺ excretion in stool was as high as ~80% of dietary intake (average 37%) in some hemodialysis (HD) patients compared to normal controls (average 12%). ²

Such increase in K⁺ excretion in the GI tract of patients with CKD was later found to be primarily the result of K⁺ secretion into the colon/rectum rather than reduced dietary K⁺ absorption in the small intestine ^1,3, was inversely related to residual kidney function, and as a consequence could serve as the main route of K⁺ excretion in patients with ESKD. ⁴

Collectively, these findings suggest that in addition to non-dietary factors such as medications, we may need to routinely consider constipation as a potential cause of hyperkalemia in patients with advanced CKD or ESKD. ¹

Bonus Pearl: Did you know that secretion of K⁺ by the apical surface of colonic epithelial is mediated in part by aldosterone-dependent mechanisms? ⁵

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References

1. St-Jules DE, Goldfarb DS, Sevick MA. Nutrient non-equivalence: does restricting high-potassium plant foods help to prevent hyperkalemia in hemodialysis patients? J Ren. Nutr 2016;26: 282-87. https://www.ncbi.nlm.nih.gov/pubmed/26975777
2. Hayes CP, McLeod ME, Robinson RR. An extrarenal mechanism for the maintenance of potassium balance in severe chronic renal failure. Trans Assoc Am Physicians 1967;80:207-16.
3. Martin RS, Panese S, Virginillo M, et al. Increased secretion of potassium in the rectum of humans with chronic renal failure. Am J Kidney Dis 1986;8:105-10. https://www.ncbi.nlm.nih.gov/pubmed/3740056
4. Cupisti A, Kovesdy CP, D’Alessandro C, et al. Dietary approach to recurrent or chronic hyperkalemia in patients with decreased kidney function. Nutrients 2018, 10, 261;doi:10.3390/nu10030261. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5872679/
5. Battle D, Boobes K, Manjee KG. The colon as the potassium target: entering the colonic age of hyperkalemia treatment. EBioMedicine 2015;2: 1562-1563. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4740340/pdf/main.pdf

Contributed in part by Alex Blair, MD, Mass General Hospital, Boston, MA.

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