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
Rod shaped bacteria are visible on urine sediment examination when the colony count exceeds what number? Cocci bacteria?
Rods: visible if colony count >10,000
Cocci: visible if colony count >100,000
What percent of positive urine cultures are positive for E coli?
Dogs 44-45%
Cats 37%
What substance in cranberries has anti-adherence properties?
Proanthocyanidins with type A linkages - anti-biofilm properties and prevent P-fimbriated UPEC from binding to uroepithelial cells
How is D mannose anti-adherent?
Disrupts bacterial adhesion by blocking the ability of lectins on the tips of type 1 fimbriae to interact with carbohydrate moieties on urothelial cells
How might instillation of glycosaminoglycans into the urinary bladder help prevent UTIs?
E coli virulence factors injury the protective GAG barrier overlying the urothelium. Exogenous GAG may adhere to the urothelium or bind invading bacteria, thus preventing bacteria induced injury
How might estrogen help prevent UTIs in females?
Alters the urinary microenvironment by promoting vaginal Lactobacillus growth, lowering vaginal pH, and restoring atophic mucosa in the urethra - proven in humans, but not dogs
What is the basis of prophylactic antibiotic therapy?
Provide 1/3 to 1/2 the total daily dose of an antibiotic, usually at night after the last void of the day. Antibiotic concentrates in the urine overnight, preventing colonization
How long is prophylactic antibiotic therapy continued?
For 6 months with monthly cultures
At 6 months if the urine is sterile, discontinue antibiotics and monitor for relapse
What is sporadic cystitis (previously called uncomplicated UTI)? What animals should not be managed as sporadic cystitis?
- Bacterial infection of the urinary bladder resulting in compatible lower urinary tract signs in dogs or cats.
- Intact male dogs rarely have sporadic bacterial cystitis - usually bacterial prostatitis is present - treat for this
- Dogs with >3 episodes of cystitis in 12 months should be managed as recurrent bacterial cystitis
A urine culture is preferred in all cases of suspected bacterial cystitis. However, empiric therapy could be considered in what cases?
In dogs with sporadic cystitis that have limited prior antimicrobial exposure
What causes the clinical signs of a UTI? What treatment should be considered in the first few days of UTI treatment?
Inflammation - consider prescribing an NSAID and adding antimicrobials 3-4 days later if clinical signs persist or when the urine culture results are back
If empiric antibiotics are being prescribed for a UTI, what drugs can be used?
Amoxicillin ideally, Clavamox if plain amoxicillin is not available
TMS
How long should sporadic bacterial cystitis be treated? When should a response be seen?
- 3-5 days
- If no improvement in 48 hours, re-evaluate what’s going on
Should a repeat urinalysis or urine culture be performed for sporadic bacterial cystitis?
No as long as the clinical signs have resolved
What is the definition of recurrent bacterial cystitis?
3 or more episodes of bacterial cystitis in the prior 12 months or 2 or more episodes within the prior 6 months
What should be performed for all cases of recurrent cystitis?
Urine culture
- If the pathogen isolated is different from previous organisms, reinfection is likely - identify and address underlying factors
- If a relapsing or refractory infection is present, review the drug, dosing, timing, and client compliance. Then look for underlying factors
For recurrent cystitis cases where re-infection is suspected, how long should antibiotics be prescribed? Should re-culture be performed?
3-5 days - no need to repeat culture/urinalysis if clinical signs resolved
For recurrent cystitis cases where persistent or relapsing infection is suspected, how long should antibiotics be prescribed?
7-14 days
For recurrent cystitis cases where persistent or relapsing infection is suspected, when should the urine be re-cultured?
After 5-7 days of treatment
- Positive culture: evaluate compliance, further diagnostic testing to determine why the bacteria is not cleared
- Negative culture: can determine when to stop therapy
Then 5-7 days after cessation of antimicrobials to help differentiate relapse/persistent infection vs re-infection
For animal with suspected pyelonephritis, when should blood cultures be considered?
In immunosuppressed or febrile animals - perform at the same time as urine culture
When interpreting susceptibility data for pyelonephritis or prostatitis cases, look at the antimicrobial breakpoints for what?
Serum, rather than urine
What should the initial treatment for pyelonephritis be, while waiting for culture results?
- Drugs that have efficacy against Enterobacteriaceae - fluoroquinolone or cefpodoxime reasonable
A diagnosis other than pyelonephritis should be considered if there is no improvement after what time frame?
72 hours of antibiotics, if the culture results say that antibiotic is appropriate
How long should pyelonephritis be treated? What should the follow up be?
- 10-14 days
- Repeat PE, chemistry, UA, and UC 1-2 weeks after stopping antibiotics
What drugs can be used to treat bacterial prostatitis?
TMS, enrofloxacin
What drugs can penetrate the prostatic barrier, but should not be used as empiric treatment as they are not effective against gram negative bacteria?
Clindamycin and macrolides
How long should bacterial prostatitis be treated?
4 weeks in acute cases, 4-6 weeks for chronic disease
Apart from antibiotics, what medical treatments should be considered for dogs with prostatitis?
- Ultrasound guided percutaneous drainage of prostatic abscesses
- Castration or finasteride
Subclinical bacteriuria is defined by what? What does not define it?
Bacteria in the absence of clinical signs
These things do not define it and do not indicate the need for treatment:
- Heavy growth (>100,000 CFU/mL) can be observed
- Pyuria can be observed
- MDR bacteria can be observed
When might you consider treating subclinical bacteriuria?
- Presence of plaque forming (Corynebacterium) or urease producing bacteria due to their ability to cause encrusting cystitis or struvites
Name 5 situations where urine culture may be indicated in animals without lower urinary tract signs
- Suspected pyelonephritis
- Investigation of the bladder as a source of septicemia
- Patients that are to undergo a surgical or minimally invasive procedure that will involve entering the urinary tract
- Suspected struvite stones
- Difficult to regulate diabetics
Prior to cystoscopy or urologic surgery, what should be performed?
Urine culture - if positive, treat based on susceptibility for 3-5 days before the procedure
Should peri-operative antibiotics be used in cystoscopy or urologic surgery?
Only for stone manipulation or open surgical procedures IF the pre-procedure culture was positive for bacterial growth
If peri-operative antibiotics are indicated, when should they be given and what drugs are appropriate?
60 minutes before the procedure, then re-dosed intra-operatively after 2 half lives of the drug have passed
A 2nd generation cephalosporin is appropriate or continue the antimicrobial the patient was already on
All patients with uroliths should have a urine culture performed. How should you act on the results?
- If a urease producing bacteria is identified, treat according to susceptibility - the ISCAID consensus does not recommend treating for the entire course of dissolution
- If a non-urease bacteria is present and the patient has clinical signs of cystitis - treat like a sporadic cystitis
- If no clinical signs, treat like a subclinical bacteriuria
Uroliths smaller than what diameter may not be visible on radiographs, even if they are a radio-opaque stone?
<2mm
At what pH do struvite uroliths form?
> 7
Are calcium oxalate stones more common in males or female? Struvite?
CaOx: males - 78%
Struvite: females - 82%
Uroliths that are typically considered radiolucent may be visible on radiographs if they are larger than what diameter?
> 5 mm
50% of CaOx stones are identified in 6 breeds. Name them
Miniature Schnauzer, Shih Tzu, Yorkshire Terrier, Chihuahua, Bichon Frise, Maltese