Lower urinary tract disease Flashcards
What is the vesicoureteral valve?
A valve-like effect formed when the ureter enters the urinary bladder on the serosal surface and tunnels through the bladder wall obliquely to the mucosal surface. The intramural ureter has a “j hook” conformation, Turing from a caudal to cranial direction before entering the trigone
What three factors promote unidirectional flow of urine into the bladder?
Vesicoureteral valve, ureteral peristalsis, and a compliant bladder
What is vesicoureteral reflux?
Reflux of urine back up to the kidneys
What innervation is most important for neurogenically mediated ureteral contraction?
Sympathetic innervation - alpha-1 receptors predominate, but alpha-2, beta-adrenoreceptors all present
What drives normal ureteral peristalsis?
- Myogenic in origin - not neurologic
- When urine enters the ureter, it initiates electrical impulses that are conducted between smooth muscle cells => peristalsis propelled towards the bladder
During obstruction of a ureter, spasmodic contractions occur, which are mediated by what?
Sympathetic input
Stimulate of the ureter with alpha-adrenergic agonist causes what? With beta-adrenoreceptor agonists?
Alpha agonists: ureteral contraction
Beta agonist: ureteral relaxation
What is the most common ureterolith type in dogs and cats?
Calcium oxalate
Conservative medical management of ureteroliths may be attempted if:
- There is minimal renal functional compromise
- No evidence of infection
- No evidence pf progressive ureteral dilation
What is the normal diameter of a cat ureter? Dog ureter?
Cats: 0.3-0.4 mm
Dogs: <2.7mm but varies with breed
In one study, medical management of ureteroliths was successful in what percent of cats?
8-13%
What is the mechanism of action of prazosin and tamsulosin?
Alpha-adrenergic antagonists
Medical management of ureteroliths consists of what therapies?
IV fluid administration, diuretics, alpha-adrenergic antagonists
If medical management of ureteroliths is attempted, what are indications to pursue surgical intervention instead?
Progressive enlargement of the ureter or renal pelvis, worsening renal function, uncontrollable pain, or no movement in 1-2 weeks
For cats, no movement in 24-48 hours
Name 4 urease producing bacteria that may be present with struvite uroliths
Staphylococcus, Proteus, Klebsiella, Corynebacterium, Mycoplasma
Why shouldn’t obstructive struvite ureteroliths be medically managed?
- An obstructed stone is not being bathed in urine, so dissolution is not effective
- Often results in obstructive pyelonephritis which has a high risk of urosepsis
What minimally invasive procedure can be used for the treatment of struvite ureteroliths in dogs?
Retrograde lavage of the renal pelvis and placement of a ureteral stent
Cats typically require surgical, antegrade placement and it’s more difficult
If a ureteral stent is used, when should it be removed or replaced?
Prior to discontinuing antibiotics (may harbor bacteria)
What is shock wave lithotripsy and what species can it be used in?
Uses shock waves generated outside the body and target at the uroliths using integrated fluoroscopy or ultrasonography - used to fragment uroliths in dogs
What percent of uroliths in dogs can be removed via shock wave lithotripsy?
80%, although 50% of dogs require 2+ treatments
Ureteral stents induce passive ureteral dilation, increasing the diameter of the lumen by how much?
3 fold
What is a circumcaval ureter?
Congenital anomaly characterized by ventral displacement or duplication of the caudal vena cava, which crosses over the ureter and results in compression of the proximal ureter - more commonly affects the right side
Uropathogenic E coli contain what adhesion molecule that is expressed by 100% of bacteria that cause pyelonephritis?
Type 1 fimbriae that bind mannose targets on the urothelium
Why are gram negative organisms more likely to cause pyelonephritis than other organisms?
Express adhesion molecules with high affinity for kidney tissue - not typically expressed in other organisms