Exam 3 - Ureteral Obstructions Flashcards
why are dogs more amenable to stents for ureteral obstructions than cats?
cats have ureters that enter the bladder further distally than dogs, so stents sit very closely if not in their urethra which is painful
what is the kidneys’ immediate response to obstruction?
ureteral pressures increase immediately
renal blood flow decreases
pressure in bowman’s capsule goes up & GFR/blood flow decreases
vasoactive mediators are released leading to more vasoconstriction & further decreased blood flow
WBC influx
fibrosis - chronicity -> permanent damage!!!
T/F: time is of the essence when dealing with a patient with blocked ureters
true - 5 days in dogs & 4 days in cats if you’re aiming to get them back to normal function
what is the most common cause of ureteral obstructions in dogs & cats? why is this important?
ureterolithiasis - calcium oxalate stones
NOT DISSOLVABLE!!!
behind calcium oxalate stones causing ureteral obstruction, what commonly can cause it dogs & cats?
dogs - struvite stones
cats - blood calculi/pus balls
what is the normal size of a cat ureter?
1 mm
if you have a cat that you palpate a large kidney on, but don’t see any stones on rads, what should you do?
do an ultrasound - could be blood calculi causing the obstruction
is bilateral disease associated with ureteral obstruction more common in dogs or cats?
cats
what are the indications of when you should intervene for nephrouteroliths?
if they obstruct urine flow
if they grow in the face of appropriate therapy
associated with serving as a nidus for infection
associated with serious pain or hematuria
how do circumcaval ureters cause issues in cats?
more likely to be seen in cats ~15%
usually the right ureter wraps around the cava, which causes compression over time
what is the best way to diagnose circumcaval ureters in a cat?
CT
what is usually seen on physical exam of patients with ureteroliths?
asymmetrical kidney palpation & pain
or could also not have any pain
what is the common signalment of animal affected by ureterolithiasis?
middle aged to older animals is most common
can happen in young animals
why is it important to do a urine culture for a dog with a ureteral obstruction?
50-75% of them will have a positive urine culture!!!! indicates the need for antibiotics
high incidence of concurrent UTI & pyelonephritis
if you palpate asymmetric kidneys on physical exam, what should you suspect?
obstructed kidneys!!!!
will an animal be azotemic if they have one of two healthy kidneys become obstructed? why?
no - takes a minimum of 75% of renal mass loss to see azotemia
minimum of 60% of functional nephron loss in animals with chronic kidney disease
what clin path abnormalities do you expect to see in a cat with a ureteral obstruction?
azotemia
hyperkalemia
hyperphosphatemia
normocytic, normochromic anemia
positive urine culture
hypercalcemia
what clin path abnormalities do you expect to see in a dog with a ureteral obstruction?
positive urine culture
azotemia
leukocytosis
what diagnostic imaging is recommended when working up a patient for a ureteral obstruction?
combine ultrasound & radiographs
in a transverse plane, how big should the pelvic width of the ureter measure in a dog & cat?
dogs - up to 2 mm
cats - 1.6 mm
what is the normal diameter of the canine ureter? what about the feline ureters?
dogs - ranges from 1-3 mm
cats - internal diameter is 0.4 mm & outside diameter of 1 mm
what is seen on this ultrasound image of the kidney?
dilated renal pelvis
what is seen on this ultrasound image of the kidney?
hydronephrosis & a stone in the ureter
what is seen on this ultrasound image of the ureter?
ureteroliths
does a normal renal pelvis mean there is no obstruction present?
NO!!!
26% of obstructed feline ureters will result in minimal pelvic dilation < 4 mm
what are some contraindications for medical management of a patient with ureteroliths?
if they are oliguric/anuric
hyperkalemic
progressively getting worse over 24-72 hours
not fluid overloaded
what is included in medical management for patients with ureteroliths?
iv fluids, a blockers, diuretics, amitriptyline, glucagon, & supportive care
T/F: a nephrectomy should be the absolute last resort for treating a ureteral obstruction
true
what are some surgical options for treating ureteral obstructions?
ureterotomy/ureteral resection & anastomosis
ureteral re-implantation
ureteronephrectomy
what are the most common surgical options used for treating ureteral obstructions?
ureterotomy & reimplantation
what are the complications associated with ureterotomy & reimplantation surgery?
uroabdomen, site edema, recurrence of obstruction (40%), stricture, & leakage
what is extracorporeal shockwave lithotripsy?
procedure used to fragment uroliths so that they are small enough to be passed & voided - ultrasound shock waves are used to crush stones
not as effective in cats
what is included in a shock wave lithotriptor?
energy source for generating the shock waves
focusing device to concentrate the shock wave energy to a focal zone
coupling medium to transmit the shock waves from the generator to the urolith within the patient’s body
imaging system (fluoroscopy & ultrasound) used for positioning the urolith within the focal zone
T/F: all common uroliths are amenable to fragmentation by ESWL except for cystine stones
true
what are the goals of ureteral stenting?
divert the urine to bypass the obstruction
passive ureteral dilation
decrease surgical tension
aid extracorporeal shockwave lithotripsy
prevent future obstructions while the stent is in place
when is a percutaneous placement of ureteral stent common?
common in dogs that have a UCC causing obstruction
when do we use a hybrid approach for placing a ureteral stent?
generally done for patients that are too small to scope
what animals do we use a cystoscopic retrograde placement for a ureteral stent? what about an antegrade approach?
retrograde - dogs
antegrade open - cats
what is the most common short term ureteral stent complication seen in cats? why?
dysuria - they have ureters that enter the bladder very distal, so the stents are very close to the urethra if not in it
what are some long term complications associated with ureteral stents?
pollakiuria, stent migration, ureteritis, tissue in-growth, chronic hematuria, UTIs, & stent reobstruction
T/F: dogs with ureteral stents have fewer complications than cats
true
what makes up a subcutaneous ureteral bypass?
locking loop nephrostomy tube
cystotomy tube at the apex of the bladder
catheters are tunneled under the skin
attach onto a subcutaneous port
permanent, internalized drainage system
what is the success rate of SUBS?
85-90% survival to discharge
well tolerated by cats long term
what are the disadvantages of SUBS?
life long management!!!!
current recommendations include 3 month recheck with SUB flush (special HUBER needle, tetra EDTA, required u/s & experience)
what are the peri-operative complications associated with SUBS?
nephrostomy site leakage, catheter leakage, catheter obstructions/kinks, & blood clot occlusion
what are the long term complications associated with SUBS?
infections, encrustations, failure to resolve azotemia, kinking, migration, & peritoneal effusion
when should you intervene in treatment for a patient with nephroliths?
recurrent or persistent UTIs proven or presumed secondary to nephroliths
compromise of renal function worsening with a large stone burden
recurrent or persistent clinical signs
severe hematuria that is renal in origin
