Their research, carried out with animals, could lead to a "bladder pacemaker" to restore bladder control for the more than 200,000 Americans living with spinal cord injury (SCI) or disease-related spinal cord problems.
Neural engineer Warren Grill and biomedical engineering doctoral candidate Joseph Boggs found that applying small electrical currents to the pudendal nerve triggered coordinated contraction of the bladder and relaxation of the urethral sphincter, which controls the bladder's outlet. The electrical stimulation emptied 65 percent of the bladder's volume.
In contrast, the bladder overfills without such intervention, triggering spastic contractions that empty only about 32 percent of the volume. The urethral sphincter frequently closes, blocking the flow of urine and forcing the urine back up toward the kidneys. This backup causes the chronic urinary tract infections and kidney problems that typically plague people with SCI.
What's surprising and encouraging about the findings, said the researchers, is that electrically stimulating the pudendal nerve caused the urethral sphincter to function normally and to efficiently empty the bladder.
Boggs, Grill and biomedical engineers Brian Wenzel and Kenneth Gustafson at Case Western Reserve University in Ohio published the findings in the Journal of Neurophysiology. The paper is now available online and will be published later in 2005. The research was sponsored by the National Institutes of Health and the Whitaker Graduate Student Fellowship program.