Equine urinary tract, chronic kidney disease Flashcards
horse bladder volume
4-5L
Horses produce 10-20 L of urine per day.
horse ureter length
70 cm
stallion/gelding urethra length
75-90 cm
equine left kidney
More caudally than right (can palpate rectally).
More oval, 18x12x5cm
equine right kidney
Below last ribs and first lumbar transverse process.
Embedded into the liver (fossa). CanNOT be palpated.
Horseshoe/heart-shaped, 15 x 15 x 5 cm.
What is tiludronate for horses?
Tiludronate has been used primarily for the treatment of diseases in horses that are associated with inappropriate osteolysis, such as navicular disease and osteoarthritis.
What is sabulous sediment?
Sabulous = sandy or gritty
Sabulous cystitis, is a common condition in middle-aged male horses. Clinical signs include dribbling urine for a prolonged period with contact dermatitis in many cases, but otherwise the horses are in good health and seemingly undisturbed by the incontinence.
Horse urine can naturally be pale yellow to deep tan, turbid and viscous with calcium carbonate crystals.
Where are the glomeruli located and how many per kidney?
renal cortex
10 million per kidney
Cortical and juxtamedullary nephrons.
Where are the renal pyramids located and how many per kidney?
renal medulla
40-60 in 4 parallel rows
What are renal papillas?
structures at the tip of each renal pyramid. Act as large collecting ducts.
Renal pelvis and proximal ureter are lined with
tubular mucous glands and goblet cells which contributes to the viscous consistency of equine urine – looks foamy.
Horse urine can be pale yellow to deep tan, turbid and viscous with calcium carbonate crystals.
3 markers that give you insight about glomerular function:
creatinine
urea
SDMA
Adult horse urine production ml/kg/h.
1-2 ml/kg/h
That makes 500-1000 ml/h.
10-20L/day
Foals on an all milk diet produce 4-8 ml/kg/h.
adult and foal urine pH
Adults alkalotic at pH 7-9
Foals acidic at pH 5-7
renal blood flow % of cardiac output
ca 22% of CO
GFR in horses?
800-1000 ml/min
(1200-1400 l/day)
Which part of the kidneys are extremely sensitive to hypoxia?
the renal medulla
The medulla is extremely metabolically active but receives only about 20% of total renal
blood flow and has a low oxygen tension.
The Kidneys can regulate blood flow locally:
* Renal nerves can locally cause arterioles to vasoconstrict when blood pressure falls.
* If blood flow decreases further, kidneys produce vasodilators: prostaglandins (PGE2 and PGI2) and dopamine.
* Plus Several more mechanisms at play.
Why are NSAIDs bad for the kidneys?
So the kidneys normally produce prostaglandins in response to lower blood flow.
But NSAIDs are PG inhibitors that shut off that protective mechanism.
In case of significant hypovolemia, vasodilation will not occur when on NSAIDs.
Medullary necrosis and tubular damage will follow.
Hypovolemia and NSAIDs don’t go together!
Why is general anesthesia hard on the kidneys?
Inhalation anaesthesia decreases cardiac output and thus blood pressure is decreased.
- Renal perfusion can be decreased to a dangerous level.
General anesthesia for colic surgery can be risky for the kidneys!
Main presenting complaints in horses with renal disease. (5)
Main two are anorexia and colic.
Then come,
poor body condition
horses smells like urine
polyuria & polydipsia
Main urinary tract related presenting complaints in horses with renal disease or urinary issues. (3)
Frequent urination (pollakiuria)
Straining to urinate
Blood seen in urine (rarely)
the 4 stages of of renal disease:
- decreased renal reserve
- chronic renal insufficiency
- chronic renal failure
- end-stage renal disease
Describe decreased renal reserve (1st stage of renal disease).
Crea, urea normal; SDMA may be higher.
Kidneys can’t compensate for hypovolemia or
decreased perfusion – may have episodes of AKD.
Describe chronic renal insufficiency (2nd stage of renal disease).
Mild azotemia, decreased urine concentrating ability, polyuria.
Clinical signs of uremia are not yet present.
Describe chronic renal failure (3rd stage of renal disease).
Uremia present + slowly worsening azotemia
Describe End-stage renal disease (4th stage of renal disease).
Oliguria, severe azotemia, clinical signs of uremia.
What % of functional nephrons must be lost to see a small increase in crea?
60-75%
Further SMALL losses in functional nephrons result in a LARGER increase in crea because at that point renal reserve is low (see graph).
When is a small increase in crea clinically important and when is it not?
Small increase in crea is Clinically important during AKI but NOT clinically important during CKD.
Describe Chronic Kidney Disease in horses.
Syndrome of progressive loss of renal function.
Very uncommon
Tends to affect older horses: >15y
Predisposed Breeds:
* Thoroughbreds
* Standardbreds
* Clydesdales
Causes of Chronic Kidney Disease in horses. (4)
Congenital disorders
Immune-mediated glomerular disorders (Strep equi equi immunocomplexes)
* cause Glomerulonephritis
Tubulointerstitial disease
* Chronic interstitial nephritis
Renal neoplasia
* Very rare
Describe Immune-mediated glomerular disorders in horses.
Glomerulonephritis is the most common.
* Increased permeability of the glomerular barrier occurs resulting in Proteinuria and Microscopic hematuria.
Clinical signs rarely develop so it usually an Incidental finding found at Necropsy.
Other causes include Chronic infection such as
Strep. equi zooepidemicus, Strep. equi equi.
Experimentally, Leptospirosis & Equine infectious anemia virus can also cause glomerulonephritis.
Describe Tubulointerstitial disease in horses.
So its usually Chronic interstitial nephritis which Involves tubules and interstitium.
Is a Consequence of acute tubular necrosis.
* Secondary to ishemia, sepsis, nephrotoxic agents
NSAIDs, aminoglycosides, Vit D, Vit K3, acorns, heavy metals etc.
Or consequence of Intravascular hemolysis, rhabdomyolysis so Hemoglobin, myoglobin clogging things up.
Factors that lead from Chronic Interstitial Nephritis to CKD: (3)
Ascending urinary tract infection resulting in pyelonephritis.
Obstructive disease
Ureterolithiasis, nephrolithiasis
Signs of uremia in horses.
Are Nonspecific and mainly:
Chronic weight loss
Lethargy
Anorexia
Also possible,
Polyuria/polydipsia
Ventral edema
Poor performance
Rough hair coat
„Fishy“ odor due to Increased urea excretion in sweat.
Dental tartar, gingivitis, oral ulcers due to Excess ammonia.
Diagnosis of chronic kidney disease in horses.
Hematology and biochemistry may show:
Azotemia (!)
* Urea:Crea >10:1
Mild anemia
Hypoalbuminemia
Electrolyte disturbance (not so severe as with Acute Renal Failure)
* Hypercalcemia due to Urinary calcium excretion being reduced.
Normally horses absorb a lot of calcium via the intestinal tract and eliminate the excess as calcium
carbonate crystals.
Diagnosis of chronic kidney disease in horses.
Urinalysis may show: (3)
Isosthenuria (SG around 1.012 irrespective of hydration status)
Urine less viscous
Decreased amount of crystals (and/or More calcium oxalate crystals).
Measuring water intake in horses.
When the complaint is polyuria/polydipsia consider
Chicken or egg scensario.
Is the horse Drinking more because its urinating more? (Cannot concentrate urine)
Or is it Urinating more because its drinking more? (miscellaneous reasons)
Normal water intake is 40-65ml/kg/d so around
36 L/500 kg when not at work and in a Relatively cool temperature.
Monitor intake for 24h Using water buckets.
Repeat several times.
If the horse has free access to salt lick – take
it away.
Management of chronic kidney disease in horses.
Goal is Appropiate supportive care.
Blood samples Every 2-4 months to check on
Crea, urea, SDMA, Electrolytes, incl Ca, phosphorus.
Short course of fluid therapy, 24-48h at 2x maintenance (2x 65ml/kg/24h) to Promote diuresis.
IV fluids carry a Risk of pulmonary and peripheral edema. Measure body weight every 12-24h (sorta like ins and outs).
Fluids PO Nasogastric tube with Balanced electrolyte solution as boluses.
NB Stop administration of nephrotoxic agents and
never give them again.
Long term prognosis is grave. Humane euthanasia needs to be
considered if the horse is depressed and not responding to treatment.
Diet for CKD horse.
Good quality pasture
Palatable diet of Good quality grass hay that is
Low in calcium, low in protein (<10% crude prot.): hay analysis needed.
Oats and concentrate feeds:
*Pelleted senior feeds that are High in fiber and fat.
Omega-3 fatty acids supplementation (Fish oil, linseed oil)
Vitamin E supplement
Free water access and add electrolytes or mash to encourage drinking, but also give plain water to choose.
Do not feed extra salt!
