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
How can you treat a urethral calculii? (2)
–Calculus at ischial arch- via standing, sedated, epidural= perineal urethrotomy
–Lower urethral calculià retrieval with endoscopic instruments eg. Basket forceps
How can we prevent recurrence of uroliths? (4)
–Removal of calculus
–Removal of debris and fragments after surgery
–Antimicrobials if UTI/recurrent cystitis after urolith removal (C&S)
–Dietary management
How can we use diet to maage uroliths? (6)
- Reduce calcium absorption from GIT
- Avoid calcium supplements
- Avoid alfalfa – hay rich in Ca
- Feed low calcium containing grass hay
- Use urinary acidifiers
- Promote diuresis – add extra salt daily to concentrate ration 50-75g and provide warm water in cold weather
What use is urinary acidifciation to reduce uroliths? What can be used? (4)
–Efficacy is unproven!!!
•their effects inconsistent and they are often unpalatable at the recommended doses
- Ammonium chloride 20-40mg/kg/day PO
- Methionine 1g/kg/day PO
- Ascorbic acid 1-2g/kg/day PO
- Addition of grain to dietà only small acidification effect
What are the most likely causes of cystitis in the horse? (5)
- Primary cystitis = uncommon in the horse
- Secondary to:
–Urolithiasis
–Bladder neoplasia (less common)
–Bladder paralysis (neurogenic cystitis – issue with the innervation meaning the bladder loosing ability to empty!)
–Anotomical defect bladder/urethra
–Instrumentation of urinary tract eg. Catheterisation, endoscopy
What clinical signs are seen in horse cystitis? (5) What is different about signs in males and females?
- Dysuria –Pollakiuria, stranguria, haematuria, pyuria
- Urine scalding /urine crystals (damage to the skin where there horse is dribbling urine)
–Mares = perineum
–Males = hind limbs
How can we diagnose cystitis? (7)
–Physical examination
–Rectal palpation
•Find evidence of stones
–Urinalysis
- Identify infections
- Bacterial C&S (>10,000CFU/ml – mid-stream catch/catheterisation)
- Sediment exam within 30-60 mins of collection – 10+ leukocytes/high power field
–Has to be done within an hour if not sooner!! Cells change too much
–Ultrasonography
•Wall thickening, uroliths, masses
–Cystoscopy
- Mucosal damage, masses
- Easiest way can just have a look
What organisms are often isolated in cystitis? (9)
–E. Coli
–Proteus spp.
–Klebsiella spp.
–Eneterobacter spp.
–Streptococcus spp.
–Staphylococcus spp.
–Pseudomonas aeruginosa
–Rarely Corynebacterium renale
–Candidia spp- sick neonates
What is shown here?
Left - calcium carbonate
Right - Calcium oxalate
How can we treat cystitis? (4)
–Long term meds (4-6 weeks)
•If you were to do a sort term, might get better and then get worse again
–TMPS, penicillin à renal excretion and concentrated in urine, use C&S results
–Bladder lavage – catheter and filling bladder with saline a few times
–Treat primary problem
- Urolithiasis – get rid of them
- Sabulous urolithiasis – why is this?
What is sabulous urolithiasis?
- sabulous urolithiasis, sabulous cystitis
- Deposition of mucous and cells in the bladder. More of a slurry material (not stones).
- Presence of abnormal quantities of sediment
–mostly calcium carbonate
–in the bladder ventrally
•No stones!
why is cystitis often present with sabulous
urolithiasis?
–Constant mucosal irritation due to the sand and prevents the bladder emptying completely
–Bacterial ammonia production in the sediment
What is the effect of Stretching/inflammation of bladder wall from the sand in the bladder with sabulous urolithiasis?
–Negative effects on detrusor muscle function
–Decreased bladder function à more crystal accumulation
–More inflammation and stretch – less ability to empty; viscous circle!
What is sabulous urolithiasis often secondary to?
•Secondary to neurological dz affecting bladder emptying
–EHV1, Polyneuritis equi, EPM, Sacral Fx, osteomyelitis, illicit tail block
What can be seen?
Bladder was huge and then opened up and its like play doh inside; was never going to pass out alone!
Sabukous urolithiasis
What are the clinical signs of sabulous urolithiasis? (2)
–Urinary incontinence
- Primary or secondary UT disease
- Neurological
- Idiopathic
- UMN lesions rarely cause sabulous cystitis
- LMN lesions à overflow incontinence
- UMN/LMN lesions à failure of bladder to empty completely, allow accumulation of sabulous material à further detrusor m. Function loss à common end stage neuromyopathy
- Often see some urine scalding too
–Hind limb weakness/ataxia.
•Worth doing a neuro assessment
How can you diagnose sabulous urolithiasis? (4)
- History
- Clinical signs
- Rectal examination- flaccid bladder full of sediment
–Never really empty
•Confirmed on endoscopic examination of bladder
What is the prognosis of sabulous urolithiasis?
- Pathological changes are generally irreversible
- Poor unless the primary cause of bladder paralysis can be fixed
–If you get it early you can manage to an extent
–Mechanical – may restore
–Neuro – wont go back to normal function
–Treat as a life long
–May need to empty and lavage periodically.
•Owners need to be committed to long term management/treatment
4/5 horses returned to athletic function with appropriate management
How can you treat sabulous urolithiasis? (5)
–Bladder lavage
- Repeated, large volumes, sterile saline
- Remove all the things preventing contracting
–Antimicrobial therapy
•Based on urine C&S, initial therapy eg. TMPS which usually works well over a few weeks
–Anti-inflammatory therapy
- Clinical perception for requirement eg. NSAIDS
- Might be helpful in terms of pain and inflammation
–Dietary management
•Low calcium diet might benefit
–Bethanecol??
- Not licensed in horse, no pharmacokinetic data for the drug, but reports suggest dose rates
- Meant to help the bladder empty…?
- Not a 1st opinion drug
What is the aim of treating sabukous urolithiasis?
–to encourage bladder emptying while hoping for recovery/improvement as reflex neurological activity develops
What is Pyelonephritis usually assocaited with? (4)
- Urolithiasis, nephrolithiasis, ureterolithiasis
- Recurrent cystitis
- Bladder paralysis
- Bladder neoplasia/ FBs
What are the clinical signs of pyelonephritits? (5)
–Dysuria- haematuria and pyuria rather than stranguria/pollakiuria
–Fever, weight loss, anorexia, depression
How can you diagnose pyelonephritis? (4)
–Same as cystitis
–Also CBC and biochemistry
–Cystoscopy: evaluate ureteral openings
- Catheterise and sample them individually
- Differentiate unilateral vs bilateral disease
- See from which ureter is producing different colour
–US
•kidneys, bladder, ureters
What is this?
–Cystoscopy: evaluate ureteral openings
What organisms are usually invovled with pyelonephritis? (5)
–Those on cystitis list
–Haematogenous septic nephritis
- Actinobacillus equuli
- Streptococcus equi equi
- Rhodococcus equi
- Salmonella spp
How can you treat pyelonephritis?
–Prolonged antimicrobials based on C&S
–Unilateral disease= surgical removal of kidney +/- ureter. Need to be sure the other kidney is 100%
–Successful tx of bilateral disease is RARE as problem often diagnosed at a late stage
What is haematuria associated with? (9)
–Vascular malformation
•If horse is young
–UTI
–Urolithiasis
–Neoplasia
–Exercise
–“Oxidation”
- Horse urine contains pyrocatechin, an oxidising agent that causes urine to turn red-brown after exposure to air, snow, bedding
- If a horse passes urine in shavings, after a while in shavings looks different and may look like blood
- Would need to see straight from being passed
–Nephrotoxicity
•NSAIDs
–Urethral defects
•Rent (lesions) at proximal urethra or ischial arch in males also haemospermia in stallions, pathophysiology unknown, blowout of corpus spongiosum penis into the urethral lumen
–Idiopathic
What is idiopathic haematuria?
- Sudden onset, potentially life threatening Haematuria
- Haemorrhage from 1 or both kidneys à blood clots in urine
- Cause undetermined
- Cases reported- renal adenocarcinoma, arteriovenous or arterioureteral fistula
- No other signs of disease
- Haemorrhage can be episodic; may present with anaemia
- Often need blood transfusions
How can we diagnose idiopathic haematuria? (7)
–Exclusion of other disease
–Signs of acute blood loss-tachypnoea, tachycardia, pale mm
–Rectal palpation- enlarged, irregular bladder
–Endoscopy- confirm blood coming from one or both kidneys
–Ultrasonography – anything wrong with the kidneys?
–(Renal gamma scintigraphy)
–(Renal biopsy) – might be helpful but in reality just make the kidney bleed more
How do we investigate haematuria? (6)
–Physical examination
–Rectal palpation
–Haematology, blood biochemistry
–Urinalysis
- Reagent strips cannot differentiate pigmenturiaà haemoglobin or myoglobin (hard to know what is causing the urine discolouration)
- Microscopic vs Macroscopic haematuriaà
–centrifuge sample à red pellet and yellow clear supernatant
- Glomerular bleeding à variation in RBC size and shape and Hb content , presence of Hb casts (RBC + Hb + Tamm-Horsfall protein)
- Bleeding from other sites à more uniform RBC population
–Cystoscopy
–Ultrasonography (kidneys & bladder)
What is the meaning of the different timings of haematuria throughout urination?
- Throughout urination= haemorrhage from kidneys, ureter or bladder
- At beginning urination= lesions distal urethra
- At end urination= lesion prox urethra or bladder
How can tou treat idiopathic haematuria?
–Supportive care for acute blood loss à blood transfusions
–Haemostatic meds eg. Aminocaproic acid, formalin
–Corticosteroids if suspect immune mediated cause
–If unilateral renal originà nephrectomy but risk of haematuria developing in other kidney ? Increased risk in Arabs
How do you treat urethral rents?
–often haematuria resolves spontaneously
–If persists> 1 month or significant anaemia àtemporary sub-ischial urethrotomy has been successful (bypass the rent to give it time to heal)
When are urethral rents seen? Where is the common site?
•After trauma, catheterisation or unknown
–corpus spongiosum blowout?
–Passes a catheter can be the hardest bit to do
•Most common site – at ischial arch
What are the clinical signs of urethral rents? (3)
–Haematuria start/end urination
–Periurethral accumulation of urine (rare)
–No stranguria/no pollakiuria
How can you diagnose urethral rents? (2)
–Endoscopy of urethra
–Contrast radiography; insert contrast in the penis and let it flow. Works in foals but more difficult to do in adults.
How do you treat urethral rents? (3)
–Benign neglect
–Temporary urethrotomy + catheterisation!?
–Antimicrobial treatment alone is unsuccessful
What is the results of pigmenturia?
–Pigments are nephrotoxic can deposit in glomerulus or tubules = AKI
–Interaction of iron ions in the haem molecules with surface molecules on proximal tubular epithelium cells
–Can lead to ARF – can be lethal
–Intra-tubular pigment crystals
What are the differentials for pigmenturia? pre renal? (3), renal (1), post renal (4)
•Pre-renal
–DDx of Haemolysis
•IMHA, Piroplasmosis, Anaplasmosis, drug toxicities, oxidative damage, liver disease
–Rhabdomyolysis
•Myoglobinuriaà to differentiate from haemoglobinuria do ammonium sulphate precipitation (Blondheim) test
–Haemolytic uremic syndrome
•Renal
–Intrinsic renal disease
•Post-Renal
–Urolythiasis
–Cystitis
–Urethral rents
–Vaginal varicocele/genital tract disease
