Equine Renal Disease

T/F: Clinical signs of urinary disease are often nonspecific.

True!

What kind of renal disease has signs often masked by concurrent disease and have recognized risk factors, like nephrotoxic drugs?

Acute kidney disease (AKI)

What kind of renal disease is often an incidental finding or acute exacerbation of chronic condition, where the inciting cause is rarely known?

Chronic kidney disease (CKD)

What are the SIX common presenting complaints with urinary disease in horses?

1. Abnormal urine/urination (color/stranguria or dribbling/volume)

2. Weight loss (especially CKD)

3. Lethargy

4. Colic

5. ADR

6. Decreased appetite

Stranguria and dribbling are classic (upper/lower) urinary tract signs.

Lower

What color is normal urine?

When is urine usually turbid?

What TWO things usually make urine turbid?

Pale yellow to deep tan

End of stream

Mucous and crystals

Name at least THREE things that can cause pigmenturia.

Hematuria (kidney or LUT), hemaglobinuria, methemoglobinuria, myoglobinuria, bilirubinuria

T/F: Reddish color on snow or shavings may be normal.

True!

Abnormal urination is most associated with (LUT/UUT) disease.

LUT

————- may indicate neurologic disease and —— often presents as colic, but both are primary urinary signs.

Urine scald

Stranguria

What is reduced or absent urine production by the kidney?

Is it more common with AKI or CKD?

Oliguria/anuria

AKI

Is polyuria more common with AKI or CKD?

CKD

What are THREE important differentials for PU/PD in horses?

1. Endocrine (PPID)

2. Psychogenic polydipsia and medicaations (corticosteroids)

3. Physiologic (lactation/hot weather/heavy work)

What is the normal urine output for a horse?

What is considered polyuria?

10-20 ml/kg/day (5-10 L/day)

>50 ml/kg/day (>25 L/day)

What is the normal water intake for a horse?

What is considered polydipsia?

40-60 ml/kg/day (20-30 L/day)

>100 ml/kg/day (>50 L/day or >13 gallons)

What are the THREE mechanisms for PU with renal disease?

1. Increased tubular flow rate

2. Decreased medullary hypertonicity

3. Impaired response of collecting ducts to ADH

What is the most common presenting complaint in CKD horses?

Weight loss

Name FOUR other clinical signs of CKD.

1. Inappetence

2. Ventral edema

3. Lethargy/poor performance

4. Halitosis/dental tartar

What are FOUR pathophysiologic reasons behind CKD?

1. Accumulation of uremic toxins and nitrogenous waste in blood

2. Increased ammonia production

3. Anemia and protein loss

4. Activation of the RAAS

What are TWO important findings often seen with renal disease on CBC?

1. Inflammatory leukogram (AKI or pyelonephritis)

2. Anemia (CKD- reduced EPO)

What are FOUR important chemistry abnormalities often seen with renal disease?

1. Azotemia

2. Electrolyte alterations

3. Hypoalbuminemia

4. Acid base (often secondary)

—- is less sensitive of an indicator of renal disease in horses compared to small animals.

BUN

T/F: PLE is uncommon in horses, so you should look for other causes when you see a horse with hypoalbuminemia.

True!

What is a LESS sensitive indicator for loss of renal function compared to SDMA or USG and requires >75% loss of nephron function?

Creatinine

T/F: Small increases in creatinine are usually unproblematic in horses, but large jumps are often clinically significant and should be investigated.

False! Small increases in creatinine can INDICATE AKI in at-risk horses EVEN if it is still within the RI.

T/F: Azotemia defines renal disease.

False! Azotemia does NOT define renal disease, and you must always differentiate between pre-renal and renal azotemia.

What is the major difference between pre-renal and renal azotemia?

Pre-renal: dehydration/hypovolemia; resolves with fluid replacement

Renal: abnormal USG and electrolytes

You should expect a >—-% reduction in creatinine within 12-14 hours of appropriate fluid therapy.

>50%

How can administration of IV fluids and a-2 agonists impact urine?

Horse passes larger amounts of dilute urine -> impact USG interpretation

What can be used to compare urine and serum creatinine and electrolytes?

Fractional excretion of electrolytes

When measuring —-, you should always measure prior to administration of IV fluids or medication such as a-2 agonists.

USG

What is isosthenuric in the horse?

1.008-1.014

Isosthenuria relies on loss of —-% of nephrons.

>66%

What are the normal USG values of an adult?

>1.025-1.040

T/F: The USG is less on dry forage than pasture.

False! USG on pasture is LESS THAN dry forage USG.

What USG would be pre-renal azotemia?

>1.025

What is the normal urine pH of adults and foals?

Adults: 8-9

Foals: 5.5-8

What causes false positives with protein?

High urine pH

T/F: Blood on urinalysis does not distinguish between intact RBC, hemoglobin, or myoglobin.

True!

T/F: Glucose is negative in urine on a normal horse.

True!

What can glucosuria WITHOUT hyperglycemia indicate?

AKI

What THREE things can cause hyperglycemia-associated glucosuria?

1. Drugs (a-2 agonists, corticosteroids, dextrose in fluids

2. Physiologic stress/exercise

3. Pathologic (sepsis, PPID, diabetes, etc.)

Sediment should be examined within how long after urine collection?

1 hour

What crystals are NORMAL in horse urine?

Calcium carbonate

T/F: Granular cysts are normal findings in horse urine.

False! Granular casts are ABNORMAL and can suggest renal tubular damage (AKI).

What is the formula that compares creatinine and electrolytes in urine and serum, as described by the fraction excretion of electrolytes (Fex)?

Serum Cr/Urine Cr x Urine Elect/Serum Elect x 100

What is the normal range of Na/Cl in a Fex? K?

Na/Cl:

With tubular damage, electrolyte re-absorption (increases/decreases) and Fex (increases/decreases).

Decreases

Increases

What is a biomarker of acute kidney injury and is more sensitive than creatinine as an indicator of altered renal function?

SDMA

What value is increased with excessive production associated with renal tubular damage, as in aminoglycoside toxicity?

Urinary GGT

Azotemia should improve by at least —-% within ——— hours in horses that are appropriately fluid resuscitated.

50%

12-24 hours

What are TWO methods to visualize the urinary tract?

Ultrasound (+/- biopsy) and cystopscopy

What can be visualized through the spleen at the last ICS?

What can be visualized at the last 2-3 ICS and is heart-shaped?

Left kidney

Right kidney

T/F: Calcium carbonate crystals in the bladder should settle ventrally on ultrasound.

True!

In (foals/adults), the bladder can be seen trans-rectally or transabdominally and transabdominally only in (foals/adults).

Adults

Foals

What are TWO ultrasound findings with AKI?

1. Enlarged kidney

2. Hypoechoic parenchyma

What should you expect to see with end-stage kidney disease on ultrasound?

Very small irregular kidney

What artifact is typically accompanied by a nephrolith?

Shadowing

Which kidney is preferred for biopsy?

What is a potential complication?

Right

Hemorrhage

What is the most useful diagnostic for renal neoplasia and may offer diagnostic and prognostic value in some horses with AKI, but rarely changes case management?

Renal biopsy

T/F: Renal biopsy is less helpful in chronic disease.

True!

What diagnostic is most helpful for visualizing lower urinary disease?

Cystoscopy