PATHOLOGY - Equine Urinary Disease Flashcards
Describe the appearance of normal urination in a male horse
When male horses urinate, they will be in a stretched, lordotic (inward curvature of the lumbar spine) position, the tail will be elevated and the penis will be out of the sheath. Urination in horses requires abdominal contraction, and there should be a brisk stream of urine which won’t contaminate their limbs due to their posturing. Male horses may grunt when urinating, this is normal and not a sign of pain
Describe the appearance of normal urination in a female horse
When female horses urinate, they will be in a stretched lordotic position, the tail will be elevated and there should be a brisk stream of urine which which won’t contaminate their limbs or perineum due to their posturing
How does urination differ in horses in oestrus?
When female horses are in oestrus, they will have pollakuria
How much water should a horse intake per day?
2 - 4 litres of water per kg of dry matter consumed per day
When is a horse classified as polydipsic?
A horse is classified as polydipsic if they are drinking more than 100ml/kg/day
What is one of the first signs of polydipsia in the horse?
Hard faeces
What are the differential diagnoses for PUPD in horses?
Psychogenic polydipsia
Secondary to renal medullary washout
Hyperadrenocorticism
Chronic renal failure
Diabetes insipidus
What is the most common cause of PUPD in horses?
Psychogenic polydipsia
What causes psychogenic polydipsia in horses?
Psychogenic polydipsia is usually due to boredom, environmental changes or feeding changes in horses
What is secondary renal medullary washout?
Renal medullary washout is a condition where the normal osmotic gradients between the renal interstitium and the renal tubules are reduced due to a loss of sodium, resulting in an inability to concentrate urine. This loss of sodium can be caused by long term psychogenic polydipsia as excessive water intake will dilute sodium levels in the blood, and result in the loss of both water and sodium in the urine. Horses with renal medullary washout and psychogenic polydipsia usually concentrate their urine in response to the gradual restriction of water, achieved via a water deprivation test
What is the gross appearance of normal adult equine urine?
Normal adult equine urine will appear pale yellow to brown, slightly turbid and viscous
Why does normal adult equine urine appear turbid and viscous?
Horses have a large quanitity of mucus in their urinary tract which causes the urine to be viscous, and horses excrete a lot of calcium crystals into their urine due to their diet being so high in calcium, causing the urine to be turbid
When is urine specific gravity (USG) classified as hypersthenuric in an adult horse?
Urine specific gravity above 1.020 is classified as hypersthenuric
What is the gross appearance of normal foal urine?
Normal foal urine will appear yellow, watery and translucent
Why do foals typically have dilute urine?
Foals should typically have dilute urine as they have a higher intake of fluids, primarily milk, which is high in water content. As a result they should be producing dilute urine
What can be indicated if a foal produces more concentrated urine?
If a foal produces more concentrated urine, this can indicate they are not getting sufficient fluid intake
Which urinary tract diseases are seen in young horses?
Patent urachus
Ectopic ureters
Rectovaginal fistula
Rectourethral fistula
Polycystic kidney disease
Renal agenesis
Most of these are congenital diseases
What is the key sign of ectopic ureters in horses?
Urinary incontinence in a young horse can be a key sign of ectopic ureters
Which urinary tract diseases are more commonly seen in older horses?
Neoplasia
What are the most common forms of bladder neoplasia seen in horses?
Bladder squamous cell carcinoma
Bladder transitional cell carcinoma
Which history questions can be benefial to ask when investigating equine urinary tract disease?
Have there been any recent dietary changes?
Has the horse been moved from pasture to stabling?
Is the forage the horse is being fed high in calcium?
Is the horse being given any supplements (such as calcium supplements)?
Is the water intake adequate?
Does the horse have access to salt blocks?
Has there been any recent environmental changes?
Has there been any recent trauma?
Are any of the other horses affected?
Could the horse have had access to any toxins?
Is the horse being treated with NSAIDS?
Why is it important to establish if the horse has had any recent dietary changes or has been moved from pasture to stabling?
Dietary changes and movement from pasture to stabling can cause a dramatic drop in water intake in horses
Why is it important to determine the quantity of calcium in a horse’s diet?
Equine diets are already very high in calcium so it is important to determine if the owner has been providing high calcium forage or supplements as this could contribute to the development of further calcium carbonate crystals in the urine and increase the risk of urolithiasis
Which toxins can cause urinary tract disease in horses?
Red maple
Acorns
Aflatoxins
What are the potential clinical signs of urinary tract disease in horses?
Dysuria
Stranguria
Pollakuria
Haematuria
Oliguria
Anuria
PUPD
Urine scalding/staining of the hindlimbs or perineum
Weight loss
Lethargy
Poor performance
Pyrexia
Anaemia
Can appear lame due to external genital pain
More systemic clinical signs typically indicate renal disease
Which factors should you assess during the clinical exam of a horse with suspected urinary tract disease?
Thorough clinical examination
Take a blood sample (prior to sedation)
Rectal examination
Collect a sterile urine sample
Examine the external genitalia
Which structures should you palpate on rectal examination of the horse when investigating urinary tract disease?
Caudal aspect of the left kidney
Bladder
How do you collect a sterile urine sample in horses?
Urinary catheterisation
Which sedative drugs should you use to examine the penis on a horse?
To examine the penis you should sedate the horse with a combination of acepromazine and xylazine as acepromazine is the most reliable sedative drug for relaxation of the retractor penis muscle
What are the differential diagnoses for a mass on the penile sheath in horses?
Sarcoid
Squamous cell carcinoma
Habronemiasis
Melanoma
Which signalement is more prone to melanoma in horses?
Grey horses are more prone to melanoma due to having increased numbers of melanocytes
What are the differential diagnoses for a perineal or perivulval mass in female horses?
Squamous cell carcinoma
Abscess
Post-service injury
Fibrosarcona
Lymphoma
What is indicated by depigmentation of the external genitalia in horses?
Depigmentation of the external genitalia in horses can be a key sign of papilloma virus lesions which can precede the development of squamous cell carcinomas
What is a urethral diverticular concretion?
A urethral diverticular concretion, also known as a bean, is an accumulation of excess smegma which has hardened at the urethral fossa in male horses
What are the clinical signs of a urethral diverticular concretion?
Urine spraying
Dysuria
Swelling of the urethral opening
How do you treat a urethral diverticular concretion?
Manual removal of the bean and sheath cleaning with water based lubricant and water
Which diagnostic tests can be done when investigating urinary tract disease in the horse?
Urinalysis
Haematology and Biochemistry
Ultrasound
Cystoscopy
Abdominocentesis
Neurological examination
What are the limitations of urine dipsticks in horses?
Urine dipsticks have a very low specificity in horses as they cannot distinguish between blood, haemaglobin, myoglobin and certain plant proteins that can be passed into the urine in horses
What is a more reliable method than can be used to measure proteins levels in the urine in horses?
Urine protein:creatinine ratio (UP:C)
Which crystals are normal to see in equine urine?
Calcium carbonate
Calcium oxalate
Triple phosphate
What are the most common causes of pre-renal azotaemia in horses?
Dehydration
Hypovolaemia
Endotoxaemia
What are the most common causes of renal azotaemia in horses?
Progression from pre-renal azotaemia
NSAIDs
Aminoglycosides
What is the most common cause of post-renal azotaemia in horses?
Urinary tract obstruction
How do the serum electrolytes change in horses with urinary tract obstructions?
Hyperkalaemia
Hyponatraemia
Hypochloraemia
What can cystoscopy be used to assess in horses?
Trauma
Cystoliths
Visualise the ureters
Neoplasia
What is the typical signalement for urolithiasis in horses?
Middle-aged, male horses
What are some of the key clinical signs of urolithiasis in horses?
Dysuria
Stranguria
Haematuria after exercise
Haematuria at the end of urination
Urine scalding
Colic signs
How can you diagnose urolithiasis in horses?
Rectal palpation
Urinalysis and culture
Ultrasound
Cystoscopy
Why should you do a urine culture on patients that you suspect have urolithiasis?
Urolithiasis can predispose patients to urinary tract infections
How can you treat urolithiasis in horses?
Laprocystotomy
Lithotripsy
Direct removal via the external urethral orifice in mares
When is urolithiasis classfied as a surgical emergency?
Urolithiasis of the urethra is a surgical emergency due to urethral obstruction
How can you medically manage urolithiasis in horses?
Restrict calcium intake
Maximise water intake
Diet with low cation to anion balance (DCAB)
What is sabulous urolithiasis in horses?
Sabuloud urolithiasis refers to a condition where the bladder becomes filled with sandy or gravel-like sediment which can be made up of mineral particles or small uroliths
How can you treat sabulous urolithiasis in horses?
Bladder lavage with sterile saline
Bethanechol
Phenoxybenzamine
What are the benefits of bethanecol to treat sabulous urolithiasis in horses?
Bethanecol will increase detrusor contractility to try and excrete the sediment from the bladder
What are the benefits of pheonxybenzamine to treat sabulous urolithiasis in horses?
Phenoxybenzamine decreases internal urethral sphincter tone which can help to excrete the sedminent from the bladder
Why is cystitis more common in mares?
Mares have a shorter urethra compared to male horses which can make it easier for bacteria to enter the urinary tract and cause cystitis. Furthermore, mares that have birthed foals are more prone to cystitis due to the altered conformation of the urogenital tract relative to the anal sphincter, which can make it easier for ascending infections to reach the urogenital tract
How do you treat cystitis in horses?
Treat with antibiotics, ideally based on culture and sensitivity
Which antibiotics can you use to treat cystitis in horses when you don’t have culture and sensitivity results?
Trimethroprim-sulphonamides (TMPS)
Penicllin
What is the typical signalement for bladder rupture in horses?
Post-partum mares
Male foals
What are the clinical signs of bladder rupture in horses?
Lethargy
Inappetence
Passage of small volumes of urine
Pendulous abdomen
How can a bladder rupture present on biochemistry?
Azotaemia
Hyperkalaemia
Hyponatraemia
Hypochloraemia
What can be done to assess if a horse has a uroabdomen secondary to bladder rupture?
Abdominocentesis and compare the effusion creatinine levels to the serum creatinine levels
What are the benefits of cystoscopy to diagnose a bladder rupture?
Cystoscopy can be used to determine the extent of the rupture and thus give a prognosis
How do you treat bladder ruptures?
Stabilse electrolyte imbalances
Surgical correction
Allow to heal by second intention
What are the congenital causes of urinary incontinence in horses?
Ectopic ureters
Hydroureters
What are hydroureters in horses?
Congenital malformations can predispose horses to hydroureters which is where the ureters become abnormally enlarged or dilated
What are the neurological causes of urinary incontinence in horses?
Cauda equina syndrome
Trauma to the spinal cord or brain
What is renal tubular acidosis in horses?
Renal tubular acidosis in horses is where the kidneys are unable to regulate the body’s acid base balance, resulting in metabolic acidosis
What is type 1 renal tubular acidosis?
Type 1 renal tubular acidosis is where there is an inability to excrete H+ ions at the distal convoluted tubule
What is type 2 renal tubular acidosis?
Type 2 renal tubular acidosis is where there is an inability to reabsorb bicarbonate at the proximal convoluted tubule
What are the clinical signs of renal tubular acidosis in horses?
Lethargy
Muscle weakness
Ataxia
Decreased body condition score
Tachypnoea
Tachycardia
How does renal tubular acidosis typically present on biochemistry and venous blood gas analysis?
Hyperchloraemia
Hypokalaemia
Metabolic acidosis
How do you treat renal tubular acidosis?
Correct the bicarbonate deficit and provide long term oral supplementation of bicarbinate based on venous blood gas analysis and response to treatment
