An upper motor neuron bladder means that the sensory information from the bladder cannot be transmitted to the pons and that upper motor neurons from the pons cannot reach the lower motor neurons of the bladder to cause initiation of bladder expression. To cause this, the lesion is usually cranial to S1. Cats are especially difficult to manually express due to their high external sphincter tone.
Let's look at the bladder innervation for just a moment. The detrusor muscle contracts secondary to innervation that comes from the T12-L1 region via the hypogastric nerve. There are two sphincters, both innervated by nerves arriving from the pelvic plexus (S1-S3 region), that help retain urine. The external sphincter is the only one with voluntary control and that is handled by the pudendal nerve. When we say an upper motor neuro bladder (UMN) we are really talking about anything cranial to the pudendal nerve, that is S1, because that is the only nerve with voluntary control.
We use manual expression in the acute phase of spinal cord injury to avoid separation of the tight junctions of the bladder wall muscles and, therefore, possible permanent injury to the bladder wall. Manual bladder expression works because pressure is exerted onto the urinary bladder which then forces the internal sphincter open, and eventually the external sphincter as well. Due to the high external sphincter tone occasional urinary rupture has occurred when expressing cat urinary bladders. Dogs appear to have less tone and therefore rupture is less common. A recent study (Galluzzi F, De Rensis F, et al Nov 2023) evaluated 34 cats with UMN induced urine retention secondary to acute or chronic spinal cord injury. They divided the cats randomly into two groups: group M underwent manual expression only and group MT underwent manual expression PLUS tactile stimulation of the perigenital region during expression. Tactile stimulation was described as a rapid striping motion of the perigenital region (from prepuce to scrotum or anus to vulva) over a 30 second period. This technique was copied from how female cats will lick their kittens during the first few weeks of life to stimulate urination.(As an aside - In a small study of cats less than 2 weeks of age, urinary retention occurred if this stimulation was not applied.) With this understanding, Galluzzi et al added tactile stimulation to manual expression to see if it improved bladder expression. In the M group, a urinary stream was achieved in half of cats while the MT group obtained a urine stream in 100% of the cats. Additionally, the stream was obtained in significantly less time (3.75 seconds vs 7.8 seconds). This is so simple, and yet make so much sense!
Key Point
Bladder expression for cats with UMN bladder dysfunction could have manual expression PLUS tactile stimulation applied to improve success rates!
I hope you enjoyed this week's TidBit Tuesday! Do you have a case you feel would benefit from a neurology consultation? Please reach out or use the online scheduler to schedule a consultation. This has been an emotional week for many veterinarians that I know; please stay safe and know that my phone and email are always available for you if you need to talk. I hope you have a good week.