How kidney disease patients' urine can tell if they are at serious risk

Low ammonium levels in the urine may indicate the serious risks for kidney disease patients, according to a recent study.

The University of Utah study indicates that measuring ammonium excretion in the urine may be help identify patients with chronic kidney disease (CKD) who face serious health risks.

Keeping the body's pH level in balance is important for normal organ function. Doctors commonly assess whether a patient's body fluids contain too much acid, a condition called acidosis, by measuring bicarbonate levels in the blood.

This can indicate whether the body is having trouble maintaining its acid-base balance, but it may reveal only part of the picture because the kidneys are important for eliminating acid in the urine.

Researcher Kalani Raphael and team looked to see if urine levels of ammonium may be a better indicator of acid accumulation in the body. They found that low urine ammonium excretion predicted kidney failure or death in CKD patients irrespective of serum bicarbonate concentration.

Compared with participants with the highest levels of daily ammonium excretion, those with the lowest levels had a 46 percent higher risk of dying or needing dialysis, and those with intermediate levels had a 14 percent higher risk. Low ammonium excretion predicted these outcomes even in patients who had normal serum bicarbonate. In addition, those with low ammonium excretion had a 2.6-fold higher risk of developing acidosis within one year.

"These results suggest that low urine ammonium excretion identifies individuals at high risk of CKD progression or death irrespective of the serum bicarbonate concentration," said Raphael. "Overall, acid levels in the urine provide important information about kidney health above and beyond acid measurements obtained from the blood." The findings also suggest that CKD patients with low urine ammonium excretion might benefit from alkali before overt acidosis develops. Additional research is needed to test this.

The study appears in the Journal of the American Society of Nephrology (JASN).