Constipation is a frequent and unfortunate experience of people with advanced chronic kidney disease (CKD). Reasons for this include:

• Restrictions on fluid and fiber intake
• Certain concurrent health conditions such as diabetes
• Side effects from medications such as phosphate binders
• Changes in gut flora and microbiota

Until recently, no studies had investigated the effect of laxatives on estimated glomerular filtration rate (eGFR)–the estimated percentage of one’s remaining kidney function–over time.

A new retrospective cohort study, published in Nephrology News and Issues, examined the relationship between laxative use and eGFR during the two years prior to end-stage kidney disease (ESKD) and the transition to dialysis. 

What They Did

For the study, Keiichi Sumida, MD, MPH, PhD, of the University of Tennessee Health Science Center, and his research team identified 43,622 U.S. veterans who had advanced CKD and were anticipating a transition to dialysis.

• 98% of the study cohort was male
• 22.5% had a diagnosis of constipation
• 49.8% were prescribed laxatives

Approximately 76% of participants also had diabetes and were taking medications such as loop diuretics, calcium channel blockers, RAS inhibitors, and/or opioid analgesics. 

What They Found

The researchers found that the difference in eGFR between those who used laxatives and those who didn’t was so minimal that the association was “clinically negligible”:

• eGFR:
  • 27.1 for laxative users
  • 26.8 for non-users
• Difference in eGFR decline:
  • -8.8 for laxative users
  • -8.6 for non-users

Sumida and colleagues did find more significant relationships between different types of laxatives and kidney function decline. Hyperosmotic laxatives, which draw water into the intestine, led to faster eGFR decline. Stool softeners (emollient laxatives), which draw water into the stool, led to slower eGFR decline. 

What It Means

Due to the laxatives’ minor impact on kidney function decline, the research team concluded that they are safe for use by patients with ESKD both before and after dialysis is initiated. 

“Given the recent evidence on the greater risk of adverse kidney outcomes associated with constipation,” the team wrote, “our results may also support active interventions with laxatives to treat constipation in advanced CKD patients.”

*Webb, M. J. (2021, June 28). Laxative Use Found to Be Safe for Advanced CKD Patients on Dialysis. Nephrology News and Issues. https://www.healio.com/news/nephrology/20210628/laxative-use-found-safe-for-patients-with-advanced-ckd-transitioning-to-dialysis