Exam 3 - Ureteral Obstructions

Question 1

why are dogs more amenable to stents for ureteral obstructions than cats?

Answer 1

cats have ureters that enter the bladder further distally than dogs, so stents sit very closely if not in their urethra which is painful

Question 2

what is the kidneys’ immediate response to obstruction?

Answer 2

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!!!

Question 3

T/F: time is of the essence when dealing with a patient with blocked ureters

Answer 3

true - 5 days in dogs & 4 days in cats if you’re aiming to get them back to normal function

Question 4

what is the most common cause of ureteral obstructions in dogs & cats? why is this important?

Answer 4

ureterolithiasis - calcium oxalate stones

NOT DISSOLVABLE!!!

Question 5

behind calcium oxalate stones causing ureteral obstruction, what commonly can cause it dogs & cats?

Answer 5

dogs - struvite stones

cats - blood calculi/pus balls

Question 6

what is the normal size of a cat ureter?

Answer 6

1 mm

Question 7

if you have a cat that you palpate a large kidney on, but don’t see any stones on rads, what should you do?

Answer 7

do an ultrasound - could be blood calculi causing the obstruction

Question 8

is bilateral disease associated with ureteral obstruction more common in dogs or cats?

Answer 8

cats

Question 9

what are the indications of when you should intervene for nephrouteroliths?

Answer 9

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

Question 10

how do circumcaval ureters cause issues in cats?

Answer 10

more likely to be seen in cats ~15%

usually the right ureter wraps around the cava, which causes compression over time

Question 11

what is the best way to diagnose circumcaval ureters in a cat?

Answer 11

CT

Question 12

what is usually seen on physical exam of patients with ureteroliths?

Answer 12

asymmetrical kidney palpation & pain

or could also not have any pain

Question 13

what is the common signalment of animal affected by ureterolithiasis?

Answer 13

middle aged to older animals is most common

can happen in young animals

Question 14

why is it important to do a urine culture for a dog with a ureteral obstruction?

Answer 14

50-75% of them will have a positive urine culture!!!! indicates the need for antibiotics

high incidence of concurrent UTI & pyelonephritis

Question 15

if you palpate asymmetric kidneys on physical exam, what should you suspect?

Answer 15

obstructed kidneys!!!!

Question 16

will an animal be azotemic if they have one of two healthy kidneys become obstructed? why?

Answer 16

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

Question 17

what clin path abnormalities do you expect to see in a cat with a ureteral obstruction?

Answer 17

azotemia

hyperkalemia

hyperphosphatemia

normocytic, normochromic anemia

positive urine culture

hypercalcemia

Question 18

what clin path abnormalities do you expect to see in a dog with a ureteral obstruction?

Answer 18

positive urine culture

azotemia

leukocytosis

Question 19

what diagnostic imaging is recommended when working up a patient for a ureteral obstruction?

Answer 19

combine ultrasound & radiographs

Question 20

in a transverse plane, how big should the pelvic width of the ureter measure in a dog & cat?

Answer 20

dogs - up to 2 mm

cats - 1.6 mm

Question 21

what is the normal diameter of the canine ureter? what about the feline ureters?

Answer 21

dogs - ranges from 1-3 mm

cats - internal diameter is 0.4 mm & outside diameter of 1 mm

Question 22

what is seen on this ultrasound image of the kidney?

Answer 22

dilated renal pelvis

Question 23

what is seen on this ultrasound image of the kidney?

Answer 23

hydronephrosis & a stone in the ureter

Question 24

what is seen on this ultrasound image of the ureter?

Answer 24

ureteroliths

Question 25

does a normal renal pelvis mean there is no obstruction present?

Answer 25

NO!!! 26% of obstructed feline ureters will result in minimal pelvic dilation < 4 mm

Question 26

what are some contraindications for medical management of a patient with ureteroliths?

Answer 26

if they are oliguric/anuric hyperkalemic progressively getting worse over 24-72 hours not fluid overloaded

Question 27

what is included in medical management for patients with ureteroliths?

Answer 27

iv fluids, a blockers, diuretics, amitriptyline, glucagon, & supportive care

Question 28

T/F: a nephrectomy should be the absolute last resort for treating a ureteral obstruction

Answer 28

true

Question 29

what are some surgical options for treating ureteral obstructions?

Answer 29

ureterotomy/ureteral resection & anastomosis ureteral re-implantation ureteronephrectomy

Question 30

what are the most common surgical options used for treating ureteral obstructions?

Answer 30

ureterotomy & reimplantation

Question 31

what are the complications associated with ureterotomy & reimplantation surgery?

Answer 31

uroabdomen, site edema, recurrence of obstruction (40%), stricture, & leakage

Question 32

what is extracorporeal shockwave lithotripsy?

Answer 32

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

Question 33

what is included in a shock wave lithotriptor?

Answer 33

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

Question 34

T/F: all common uroliths are amenable to fragmentation by ESWL except for cystine stones

Answer 34

true

Question 35

what are the goals of ureteral stenting?

Answer 35

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

Question 36

when is a percutaneous placement of ureteral stent common?

Answer 36

common in dogs that have a UCC causing obstruction

Question 37

when do we use a hybrid approach for placing a ureteral stent?

Answer 37

generally done for patients that are too small to scope

Question 38

what animals do we use a cystoscopic retrograde placement for a ureteral stent? what about an antegrade approach?

Answer 38

retrograde - dogs antegrade open - cats

Question 39

what is the most common short term ureteral stent complication seen in cats? why?

Answer 39

dysuria - they have ureters that enter the bladder very distal, so the stents are very close to the urethra if not in it

Question 40

what are some long term complications associated with ureteral stents?

Answer 40

pollakiuria, stent migration, ureteritis, tissue in-growth, chronic hematuria, UTIs, & stent reobstruction

Question 41

T/F: dogs with ureteral stents have fewer complications than cats

Answer 41

true

Question 42

what makes up a subcutaneous ureteral bypass?

Answer 42

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

Question 43

what is the success rate of SUBS?

Answer 43

85-90% survival to discharge well tolerated by cats long term

Question 44

what are the disadvantages of SUBS?

Answer 44

life long management!!!! current recommendations include 3 month recheck with SUB flush (special HUBER needle, tetra EDTA, required u/s & experience)

Question 45

what are the peri-operative complications associated with SUBS?

Answer 45

nephrostomy site leakage, catheter leakage, catheter obstructions/kinks, & blood clot occlusion

Question 46

what are the long term complications associated with SUBS?

Answer 46

infections, encrustations, failure to resolve azotemia, kinking, migration, & peritoneal effusion

Question 47

when should you intervene in treatment for a patient with nephroliths?

Answer 47

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