The rate of kidney deterioration as a result of bladder dysfunction due to multiple sclerosis (MS) is low, affecting only 3 percent of the patients, a single tertiary center study shows.
However, kidney deterioration is a slow process and detected only after 60 months of follow-up, highlighting the need for continued monitoring of MS patients who have lower urinary tract symptoms.
The study “Assessment of renal deterioration and associated risk factors in patients with multiple sclerosis” was published in the journal Urology.
MS patients often experience lower urinary tract symptoms, or LUTS, with up to 75 percent of patients reporting moderate-to-severe symptoms.
LUTS is a term that describes problems in holding or in frequency to urinate, urge incontinence, and nocturia (the need to wake at night one or more times to urinate), among others. Individuals with LUTS are at higher risk of their kidney function deteriorating.
Previous studies have identified MS disease duration and Expanded Disability Status Scale score (EDSS) — a method of quantifying disability in MS — as predictors of kidney deterioration.
In this study, a team of researchers at University of Texas Southwestern Medical Center evaluated the prognostic potential of these parameters in a group of patients with bladder dysfunction due to MS — a condition called neurogenic bladder.
They reviewed data of 660 patients followed in a tertiary center from December 1999 to September 2016.
Kidney deterioration was defined according to established criteria, namely patients who underwent at least two visits to the clinic due to LUTS, and who had more than double the normal levels of creatinine in the blood. Creatinine is a waste product filtered out of the blood into urine in the kidneys, so measuring its levels is a simple way to assess renal function.
Additional criteria of kidney deterioration included swelling of the kidney due to a build-up of urine (a condition called hydronephrosis), or renal shrinkage (atrophy).
A less strict criteria included patients who had a decline on kidney filtration capacity, measured by the estimated glomerular filtration rate or eGFR, by more than 30 percent.
Out of the initial pool of 660 patients, 355 met the inclusion criteria. Median follow-up of these patients was 79 months. Serial measurements of serum creatinine were available for 340 patients, and follow-up renal ultrasound for 146 patients.
The overall rate of kidney decline was low, detected in only 11 of the 355 patients – a total of 3 percent of the population analyzed – according to the more stringent criteria. Using the less strict criteria of 30 percent or greater decline in eGFR, the percentage of patients positive for kidney deterioration rose to 13 percent (46 out of 355 patients).
The majority of the patients (235 of 355) were followed-up by more than 60 months, and the decline in kidney function usually occurred at or beyond this time point.
“Since it is clear that RD [renal deterioration] can and does occur late (more than 60 months) in other neurogenic bladder conditions, continued surveillance in this population is appropriate,” researchers wrote.
The only urinary factor found to be significantly associated with renal deterioration was the uncontrolled activity of the most important muscle in the bladder, the detrusor muscle, a condition known as detrusor overactivity. That condition was noted in 153 of 355 patients.
Based on the results, the team concluded that the rate of renal deterioration in MS patients “was low (3%) at median follow-up of 79 months.” In addition, the team suggested that the “study of the impact of more aggressive control of DO [detrusor overactivity] in this population may be warranted.”