Equine Urinary Disease Flashcards
What is the epidemiology of urolithiasis and obstructive disease in horses?
–0.1-0.5% referral hospital admissions (underestimation?)
- In referral probably less
- Might be under recognised
–Adult horses (mean age ~10 years). More common in the older horses than the younger ones
–Foals – reported after ruptured bladder repair. Although reported it is not a common finding in foals.
–Males, mainly geldings à longer, narrower urethra!
•Females urethra can normally expand well so can pass the stones.
–No breed predisposition
What are the location of uroliths in horses?
What is the compostion of equine stones?
•Composition: Calcium carbonate >> calcium phosphate
What are nephroliths?
Uroliths in the kidney
- Usually within/adjacent to renal pelvis.
- Small passed to bladder – no clinical signs
What are ureteroliths?
- Probably nephroliths = ureter (enlarge over time)
- Lodge in distal ureter
- Palpate them per rectum??? RARE!!! (dorsal and lateral to bladder neck)
What are the clinical signs of unilateral nephroliths?
–Challenging to dx as mild clinical signs e.g. Recurrent colic or no clinical signs! Often misdiagnosed for colic!!!!
–Azotaemia usually absent
–Intermittent /persistent gross haematuria
What is a risk factor for bilateral nephrolithiasis and ureterolithasis?
–NSAID usage a risk factor!? (Renal papillary necrosis)
•Know they are toxic and can result in renal papillary necrosis which can form the nidus for nephroliths
What are the clinical signs of bilateral neophrolithiasis and ureterolithasis?
Usual signs (3) uncommon signs (2)
–Usually in CRF before presentation
- weight loss, polyuria, poor performance
- Reduced appetite
- Lethargy
–Uncommon signs – usually present as a chronic disease
- Obstructive disease - colic, haematuria, lumbar pain, hind limb lameness
- Signs chronic azotaemia
- oral ulceration, excessive dental tartar, melena
How can we diagnose Urolithiasis and Obstructive Disease? (7)
–Incidental at Post-mortem (particularly upper urinary tract)
–If clinical signs
- Rectal examination= turgid ureter +/- ureterolith, increased renal size
- Cannot usually palpate ureters
–Blood biochemistry
- CRF: azotaemia and isosthenuria (develops when 75% of nephrons non-functioning normally a huge reserve which can cope with damage)
- Azotaemia absent if unilateral obstruction
–Urinalysis (inc. sediment exam) à pigmenturia or microscopic haematuria
•Gross haematuria - less common
–Bacterial culture
•UTI usually NOT present, BUT should culture urine if pyuria/bacteriuria
–Often don’t grow enough to get over the threshold set for a bacteria
–Ultrasonography
- Trans abdominally ànephroliths, dilation of renal pelvis, fibrosis (echogenicity) - BUT may miss small stones <1cm
- Trans rectally= ureteral dilation and lithiasis
–Cystoscopy
•Stones in the bladder should be easy to spot
What is this?
Stones
How can you treat nephroliths? (3)
–Surgery = nephrotomy / ureterotomy
–Unilateral nephrectomy IF:
- No azotaemia; if there is azotemia as if there was would indicated the other kidney affected (over 75% of function)
- No disease in other kidney
- DO NOT REMOVE BOTH KIDNEYS
–Electro hydraulic lithotripsy (for ureteroliths)
- Endoscope passed into ureterà lithotriptor passed through biopsy channel until touches the stone surface
- Irrigating solution is used to distend the distal ureter
- Electrical impulse causes a shock wave at stone surface
- Calcium carbonate is fragile so breaks
- Fragments are flushed out
What are the most common uroliths in horses?
Cystic calculi
What are these?
–Calcium carbonate (spikey appearance) LEFT
•single, large spiculated stones, fragment
–Calcium phosphate (hard) RIGHT
•Smooth, grey-white stone, do not fragment
What are the risk factors for crystal precipitation? (8)
- Supersaturation of urine
- Prolonged urine retention; possible neurological damage
- Promoters of crystal growth
- Tissue damage; inflammation and nidus to allow the CaCo3 to precipitate
- Need nidus
- Equine urine is alkaline which favours crystallisation with CaCO3
–If you are giving carbonate to a horse do not add Ca as will precipitate
•UTI – often not associated although centre of stone often has bacteria present
What crystals do normal horses have?
Carbonate crystals
What is the relation between mucous and calculi?
–Mucous production in renal pelvis and proximal ureter acts as lubrication to stop adherence of crystals to uroepithelium
Which sex is more likely to have an onsturction? Why?
- Males >>> females
- Male urethra – long and narrow, esp at ischial arch
- Female urethra short, wide, easily distensible and permits expulsion of a calculus before clinical signs apparent
What are the clinical signs of cystic calculi? (5)
–Dysuria
–Stranguria
–Pollakiuria- frequent passage small amounts urine
–Haematuria- esp post exercise/end of micturition
•After exercise might make the calculus bounce around
–Restlessness, grunting, tenesmus during urination
How can we diagnose cystic calculi? (4)
- Rectal palpation – firm oval mass in lumen , rare to get multiple calculi
- Transrectal Ultrasonography –Easier to do before urination to see stones
- Cystoscopy – remember to drain bladder via catheter–Gold standard
Clinical signs
How can we treat cystic calculi both standing surgically (3) and under GA (3)?
IN MALES
•Techniques for standing surgery
–Perineal urethrotomy
–Pararectal cystotomy (Gokels operation)- NOT recommended
–Electro hydraulic, shockwave or laser lithotripsy
•Techniques under GA
–Laparocystotomy via parapreputial or midline incision
• urolith removal without fragmentation, urethra not traumatised, ability to flush bladder thoroughly
–Laparoscopic or laparoscopic-assisted cystotomy
–Urethrotomy – distal urethral calculi
–Anything in the bladder – do a GA to be able to bring bladder out
How can we treat cystic calculi in mares?
–Manual extraction (calculi <10cm) under standing sedation and epidural anaesthesia
–Fragmentation via electro hydraulic or laser lithotripsy- then flush fragments out of bladder
–Sphincterectomy of dorsal urethra for large stones
–Laparocystotomy rarely required
How does an urethral calculi present and where is it most common?
- More likely to cause an acute obstruction; presenting with signs of colic, may try to urinate and wont or some blood. Might be able to palpate calculi if in penis. It is when it moves from the bladder to urethra
- Commonly lodged at ischial arch in males or distal urethra
How can you diagnose urethral calculi? (4)
–Clinical signs
–Palpable calculus in penis
–Rectal examination- turgid, full bladder
–Confirmation- passage of catheter and endoscope
What are the clinical signs of urethral calculi? (3)
- colic,
frequent attempts to urinate,
blood at urethral orifice
What can happen if a urethral calculi is not noticed? What are the signs of this? (6)
Bladder rupture if not recognised early = depression,
anorexia, electrolyte imbalances, azotaemia, palpation of empty bladder on rectal, comparison of serum creatinine with peritoneal creatinine >2 fold increase