Final Exam - Equine Urinary Tract Disease

Question 1

what are the typical presenting complaints seen with urinary tract disease in horses?

Answer 1

ADR, weight loss, abnormal urination, decreased performance, & recurrent colic

Question 2

why are chronic renal disease horses anemic?

Answer 2

there is decreased erythropoietin production & a shorter RBC lifespan

Question 3

what lab values are most commonly used to interpret renal function in horses? how long does it take for disease to affect these values?

Answer 3

BUN & creatinine

75% of nephrons must be non-functional before values are increased! once elevated, a doubling of BUN & creatinine = 50% decline of remaining nephrons!!!

Question 4

what electrolyte abnormalities do you expect to see in a foal with uroperitoneum?

Answer 4

HYPERkalemia

HYPOnatremia

HYPOchloremia

increased BUN & creatinine, increased lactate, decreased bicarb (metabolic acidosis)

Question 5

what do you expect the USG of horse urine to look like after water has been deprived for 24 hours?

Answer 5

1.045

Question 6

T/F: suckling foals are naturally hyposthenuric

Answer 6

true

Question 7

can a suckling foal concentrate its urine?

Answer 7

yes - when dehydrated or hypovolemic

Question 8

is urine usually alkaline or acidic in horses?

Answer 8

alkaline

Question 9

what indicates proteinuria in a horse?

Answer 9

urine protein: urine creatinine ratio > 1 = proteinuria

Question 10

what is the renal threshold of glucose in the horse?

Answer 10

170 mg/dl

Question 11

if you get a positive dipstick for blood, what all could that potentially indicate? how do you further classify this?

Answer 11

hematuria, hemoglobinuria, or myoglobinuria

need to centrifuge it down!

Question 12

what is endoscopy used for in horses with urinary disease?

Answer 12

used to visualize the urethra, bladder mucosa, & ureter openings

Question 13

where is the left kidney located on ultrasound?

Answer 13

left kidney is deep to the spleen which is adjacent to the body wall

Question 14

what would the kidneys look like on ultrasound if a horse had an AKI?

Answer 14

kidneys appear normal, peri-renal edema, & loss of corticomedullary junction

Question 15

what would the kidneys look like on ultrasound if a horse had CKD?

Answer 15

decreased kidney size, irregular shape/margins, & increased echogenicity

Question 16

what defines acute renal failure in horses? can this be fixed?

Answer 16

sudden reduction in GFR

usually reversible if caught early!

Question 17

what damage is done to the urinary system of a horse with an AKI?

Answer 17

damage to tubules, tubular obstruction, acute glomerulonephritis, & edema

azotemia is most often pre-renal or renal in origin due to hemodynamic insult

Question 18

what is the most common classification of azotemia seen in horses? what defines it?

Answer 18

pre-renal - reversible increase in BUN & creatinine associated with hypovolemia & renal hypoperfusion

concentrating ability is maintained - USG stays above 1.014 & urine osmolality above 500 mOsm/kg

Question 19

what is decompensation of the kidneys of a horse defined as in regards to pre-renal azotemia?

Answer 19

persistence of azotemia after correction of hypovolemia

can progress to acute renal failure!!!

Question 20

what defines renal azotemia?

Answer 20

urine concentrating ability is lost in the face of dehydration or hypovolemia - urine is often isosthenuric

fractional sodium clearance is > 1%

urine to serum creatinine ratio is < 37:1

Question 21

what is an example of post-renal azotemia in horses?

Answer 21

obstruction or disruption of post-renal urinary tract!

dysuria/pollakiuria, renal colic

progressive abdominal distension - leads to bladder rupture & development of uroperitoneum

Question 22

how do you diagnose uroperitoneum in a neonatal foal?

Answer 22

ultrasound - look for free anechoic fluid in the abdomen & get a sample

uroperitoneum confirmed by peritoneal fluid creatinine concentration >/= 2X serum creatinine concentration

Question 23

is a ruptured bladder in a foal a surgical or medical emergency? why?

Answer 23

medical - hyperkalemia must be addressed first

hyperkalemia - severely affects the heart

Question 24

what would you expect the BUN to creatinine ratio to be in prerenal, renal, & postrenal azotemia?

Answer 24

pre-renal: higher ratio due to increased reabsorption of urea with low tubule flow rates

renal: values are non-discriminatory

postrenal: ratio should be higher due to preferential diffusion of urea across peritoneal membranes in cases of uroperitoneum

Question 25

what do you expect the BUN to creatinine ratio to be in a horse with an AKI? what about CKD?

Answer 25

AKI: creatinine tends to increase proportionately more than BUN, so BUN to creatinine ratio < 10:1

CKD: ratio exceeds 10:1

Question 26

what horses may be at risk of developing acute renal failure?

Answer 26

concurrent disorders - serious gi disease, rhabdomyolysis, hemolysis, & those receiving nephrotoxic medications

Question 27

when is it important to look at CK & AST values?

Answer 27

important when pigmenturia is a complaint - helps differentiate myoglobinuria from hemoglobinuria from hematuria

Question 28

why can you not trust a positive dipstick for protein on a urinalysis for a horse?

Answer 28

they normally have alkaline urine, so they can get false positive proteinuria

need to assess this using the urine protein to urine creatinine ratio to quantify it

Question 29

does normal equine urine contain glucose?

Answer 29

nope

Question 30

what are some differentials for bilirubinuria in a horse?

Answer 30

intravascular hemolysis

hepatic necrosis

obstructive hepatopathies

Question 31

is it normal to see crystals in equine urine?

Answer 31

yup - normally loaded with crystals

Question 32

where is the right kidney imaged using ultrasound on a horse?

Answer 32

adjacent to the right body wall at the dorsal 16-17 ICS

lungs will cover the cranial pole during inspiration, < 15cm in longest axis

Question 33

what are some nephrotoxins that may cause acute renal failure in a horse?

Answer 33

aminoglycosides, NSAIDS, hemoglobin/myoglobin, tetracycline (especially in foals), exposure to heavy metals (mercury), & cantharidin

Question 34

in order of most to least nephrotoxic, what aminoglycosides are known to cause acute renal failure?

Answer 34

1. neomycin
2. gentamicin, amikacin, & kanamycin are intermediate level
3. streptomycin

Question 35

how do you avoid causing acute renal failure from using nephrotoxic drugs?

Answer 35

use once daily dosing - attenuates the risk while maintaining or improving therapeutic efficacy

Question 36

what are some clinical signs associated with acute renal failure?

Answer 36

anorexia/lethargy, oliguria/anuria, tachycardia, conjunctival edema, & limb/truncal edema

Question 37

what is the most important part of treatment for a horse with acute renal failure?

Answer 37

to restore & maintain normovolemia

Question 38

T/F: urine production is a useful indicator of end-organ (renal) perfusion

Answer 38

true

Question 39

what is the most important determinant of prognosis for a horse with acute renal failure?

Answer 39

duration of renal failure before treatment is the most important determinant!!!

Question 40

what is the most common complaint for horses with CKD?

Answer 40

chronic weight loss

Question 41

what is the prognosis for a horse with CKD?

Answer 41

long term prognosis is grave - usually progressive & irreversible

Question 42

what are the goals of treatment for a horse with CKD?

Answer 42

provide supportive care

monitor the progression closely

provide human euthanasia before the development of uremic decompensation

Question 43

what treatment is used for pyelonephritis/renal abscesses?

Answer 43

prolonged, 2-4 month, systemic antibiotics based on c & s

if unilateral - consider nephrectomy

bilateral pyelonephritis has a worse prognosis