Equine urinary tract Flashcards
Describe the epidemiology of urolithiasis and obstructive disease in horses
- Adults: mean age ~10yo
- Foals: reported after bladder rupture repair
- Males, mainly geldings
- No breed predisposition
Describe the location of uroliths in the horse
- 84% in bladder, 60% remain in bladder, 24% pass into urethra to cause obstruction
- 16% in renal pelvis, 12% within renal pelvis, 45 causing ureteral obstruction
What is the most common composition of uroliths in horses and how do these form?
- Calcium carbonate more common than calcium phosphate
- Form from nidus of inflammation, infection or fibrosis
Compare the nephroliths and ureteroliths in horses
- Nephro: usually within/adjacent to renal pelvis, small passed into bladder with no signs
- Uretero: probably nephro that moved into ureter, enlarge over time, lodge in distal ureter, may be palpated per rectum
Describe the clinical signs of unilateral renal/ureteral calculi
- Mild clinical signs e.g. recurrent colic or none
- Azotaemia usually absent
- Intermittent/persistent gross haematuria
Describe the clinical signs of bilateral renal/ureteral calculi
- Hx of NSAID use
- Usually CKD before presentation: weight loss, PU, poor performance, reduced appetite, lethargy
- Uncommon signs: obstructive disease leads to colic, haematuria, lumbar pain, HL lameness, chronic azotaemia (oral ulceration, excessive dental tartar, melaena)
Describe the diagnosis of renal/ureteral calculi in the horse
- Often incidental at PM, esp. if UUT
- Rectal exam may show turgid ureter (not usually palpable - able to feel = abnormal) +/- ureterolith, increased renal size
- Blood biochem: azotaemia, isosthenuria in CKD, no azotaemia if unilateral
- Urinalysis: pigmentation/microscopic haematuria
- Bacterial culture: rule out UTI
- Ultrasonography transabdo: nephroliths, dilation of renal pelvis, fibrosis but may miss small stones <1cm
- Transrectally: ureteral dilation and lithiasis
Describe the treatment of nephroliths in the horse
- Surgery: Nephrotomy/uretotomy
- Unilateral nephrectomy if no azotaemia
- Electro hydraulic lithotripsy for ureteroliths: electrical impulse causes shock waves to break stone, fragments flushed out
What is the most common type of urolithiasis in the horse?
Cystic calculi
Compare the gross appearance of calcium carbonate and calcium phosphate calculi
- Carbonate: singe, large spiculated stones, fragment
- Phosphate: smooth, grey-white stone, do not fragment
List the risk factors for crystal precipitation in the horse
- Supersaturation of urine
- Prolonged urine retention
- Promotors of crystal growth
- Tissue damage
- Nidus present
- UTI
- Fluid therapy containing calcium
Describe the clinical signs of cystic calculi in the horse
- Dysuria
- Stranguria
- Pollakiuria
- Haematuria esp. post exercise
- Restlessness, grunting, tenesmus during urination
Outline the diagnosis of cystic calculi in the horse
- Rectal palp: firm oval mass in lumen, rare to get multiple calculi
- Transrectal ultrasonography
Outline the treatment options for cystic calculi in male horses
- Standing or GA depending on site of calculus
- Standing: perineal urethrotomy, pararectal cystostomy (not recommended), electro hydraulic, shockwave or laser lithotripsy
- GA: laparoscystotomy via parapreputial or midline incision, laparaoscopic or laparoscopic assisted cystotomy, urethrotomy for distal urethral calculi)
Outline the treatment options for cystic calculi in mares
- Manual extraction of calculi <10cm under standing sedation and epidural anaesthesia
- Fragmentation via electro hydraulic or laser lithotripsy
- Sphincterectomy or dorsal urethra for large stones
- Laparoscystotomy rarely required
Where do urethral calculi commonly lodge in horses?
Ischial arch in males or distal urethra
Compare the presentation of cystic and urethral calculi in horses
Urethral tend to cause a more acute problem
Describe the diagnosis of urethral calculi in horses
- Clinical signs: colic, frequent attempts to urinate, blood at urethral orifice
- Palpable calulus in penis
- Rectal examination: turgid, full bladder
- Confirm by passing catheter and endoscope
In the horse, what is a possible consequence of urethral calculi and how is this diagnosed?
- Bladder rupture if not recognised early
- Signs: depression, anorexia
- Clin path: electrolyte imbalances, azotaemia
- Peritoneal creatinine >2x serum creatinine
- Palpation of empty bladder on rectal exam
Describe the treatment options for urethral calculi
- Ischial arch: standing, sedated, epidural perineal urethrotomy
- Lower urethral calculi: retrieval with endoscopic instruments e.g. Basket forceps
Outline the prevention of calculi in horses
- Remove calculus, and debris
- Antimicrobials if UTI/recurrent cystitis after urolith removal
- Dietary management: reduce calcilum absorption, avoid calcium supps, avoid alfalfa, promote diuresis (add salt to concentrate ration, warm water in winter)
- Urinary acidification efficacy unproven, not really an option in horses
What conditions does cystitic occur secondary to in the horse?
- Urolithiasis
- Bladder neoplasia
- Bladder paralysis
- Anatomical defect in bladder/urethra
- Instrumentation of urinary tract e.g. catheterisation, endoscopy
Describe the clinical signs of cystitis in the horse
- Dysuria: pollakiuria, stranguria, haematuria, pyuria
- urine scalding/urine cystals (mares perineum, males HL)
How does bladder paralysis lead to cystitis in the horse?
Incomplete emptying, sediment remains in bladder leading to secondary issues
Describe the diagnosis of cystitis in the horse
- Physical examination
- Rectal palpation
- Urinalysis: bacterial C+S (>10,000cfu/ml in mid-stream catch/catheter sample), sediment exam within 30-60mins of collection (10+ leukocytes/hpf, not feasible in first op. practice)
- Ultrasonography: wall thickened, uroliths, masses
- Cystoscopy: mucosal damage, masses
List the organisms commonly involved in cystitis in horses
- E coli
- Proteus spp
- Klebsiella spp.
- enterobacter spp
- Streptococcus spp
- Staphylococcus spp
- pseudomonas aeruginosa
- Corynebacterium renale (RARE)
- Candida spp in sick neonates
Describe the treatment of cystitis in horses
- Long term ABs (4-6 weeks)
- TMPS, penicillin
- Bladder lavage
- Treat primary problem e.g. urolithiasis, sabulous urolithiasis
What is sabulous urolithiasis?
Aka sabulous cystitis: deposition of mucous and salts in bladder, sand-like/slurry material deposited in the badder - abnormal quantities of sediment, mostly calcium carbonate
Explain how sabulous urolithiasis may lead to cystitis
- Constant mucosal irritation from sand
- Prevents complete bladder emptying
- BActerial ammonia production in the sediment
- Stretching/inflammation of bladder wall negatively impacts detrusor muscle function leading to more crystal accumulation
How does sabulous urolithiasis develop?
- May be idiopathic bladder paralysis syndrome
- Or secondary to neurological disease affecting bladder emptying: EHV1, polyneuritis equi, EPM, sacral Fx, osteomyelitis, illicit tail block
Describe the clinical signs of sabulous cystitis in the horse
- Urinary incontinence (may be primary or secondary)
- HL weakness/staxia
- Generally urine scalding
Describe the diagnosis of sabulous cystitis
- History and clinical signs
- Rectal examination demonstrates flaccid bladder full of sediment
- Endoscopic examination of bladder for confirmation
Discuss the prognosis of sabulous urolithiasis in the horse
- Poor
- Pathological changes generally irreversible
- May be able to fix bladder paralysis depending on primary cause
- Long term management and treatment required, may need periodic lavage of bladder
Describe the treatment of sabulous urolithiasis in the horse
- Options for end-stage neuro-myogenic bladder dysfunction same regardless of cause
- Aim to encourage bladder emptying while hoping for improvement in bladder reflex
- Bladder lavage: repeat with large volumes of sterile saline
- Antimicrobial therapy based on urine C+S, intially TMPS over a few weeks (even if no UTI at this stage - high risk)
- NSAIDs
- Low calcium diet
- Bethanecol suggested but not licensed in horse
Describe the clinical signs of pyelonephritis in the horse
- RARE
- Signs may relate to underlying cause
- Haematuria, pyuria rather than strang/pollakiuria
- Pyrexia, weight loss ,anorexia, depression
What conditions is pyelonephritis usually associated with in the horse?
- Uro/nephro/ureterolithiasis
- Recurrent cystitis
- Bladder paralysis
- Bladder neoplasia/FBs
Describe the diagnosis of pyelonephritis in the horse
- Same as cystitis
- CBC and biochem
- Cystoscopy to evaluate ureteral openings, catheterise and sample individually
- Ultrasound of kidneys, bladder and ureters (may identify uroliths)
List the organisms involved in pyelonephritis in the horse
- Those as for cystitis
- Plus haematogenous septic nephritis: Actinobacillus equuli, Strep equi equi, Rhodococcus equi, Salmonella spp.
Describe the treatment of pyelonephritis in the horse
- Prolonged antimicrobials based on C+S
- If unilateral, nephrectomy
- Bilateral rarely treated successfully
List the differentials for haematuria in the horse
- Vascular malformation
- UTI
- Urolithiasis
- Neoplasia
- Exercise
- Oxidation
- Nephrotoxicity e.g. NSAIDs
- Urethral defects
- Idiopathic
Explain oxidation as a differential for haematuria in the horse
Horse urine oxidised after exposure to air, snow bedding (due to pyrocatechin) - turns red-brown
Describe urethral defects as a cause of haematuria in the horse
- Rent at proximal urethral or ischial arch in males
- Pathophysiology unknown, may be traumatic, iatrogenic (e.g. catheterisation)
- Blowout of corpus spongiosum penis into urethral lumen
Describe idiopathic haematuria in the horse (presentation, cause)
- Sudden onset, potentially life threatening
- Haemorrhage from 1 or both kidneys leads to blood clots in urine
- Cause undetermined, may be neoplastic, arteriovenous or arterioureteral fistulae
- No other signs of disease
- Haemorrhage can be episodic
Describe the diagnosis of idiopathic haematuria
- Exclude other diseases
- Signs of acute blood loss: tachypnoea, tachycardia, pale MM
- Rectal palp shows enlarged irregular bladder
- Endoscopy to confirm blood from kidneys
- Ultrasonography: identification of renal pathology
- Renal biopsy may be helpful but will cause more bleeding
List the diagnostic methods for the investigation of haematuria in the horse
- Physical exam
- Rectal palp
- Haem and biochem
- Urinalysis: differentiate between haemoglobin, blood, myoglobin
- Cystoscopy
- Ultrasonography of kidneys and bladder
- Assess timing of haematuria
How can haematuria of glomerular origin be differentiated from haematuria from another origin in the horse?
- Glomerular: variation in RBC size, shape and Hb content, present of Hb casts (RBC+Hb+Tamm-Horsfall protein)
- Bleeding from other sites more uniform RBC population
Outline how the timing of haematuria may indicate the origin in the horse
- Throughout: haemorrhage from kidneys, ureter or bladder
- Beginning of urination: lesions distal to urethra
- At end of urination: lesion in proximal urethra or bladder
Describe the treatment of idiopathic haematuria in the horse
- Supportive care for blood loss e.g. blood transfusions
- Haemostatic meds e.g. aminocaproicacid, formalin
- Corticosteroids if suspect immune mediated cause
- If unilateral: nephrectomy, but risk of other kidney being affected later (esp in Arabs)
Describe the treatment of urethral rents in horses
- Often haematuria resolves spontaneously
- If persists >1month or significant anaemia, temporary sub-ischial urethrotomy successful
Describe the clinical signs of urethral rents in the horse
- Haematuria at start/end of urinatioin
- Periurethral accumulation of urine (rare)
- No stranguria or pollakiuria
How are urethral rents diagnosed?
Urethral endoscopy and contrast radiography
List the differentials for pre-renal pigmenturia in the horse
- IMHA
- Piroplasmosis
- Anaplasmosis
- Drug toxicities
- Oxidative damage
- Liver disease
- Haemolytic uraemic synrome
- Rhabdomyolysis
List the post-renal differentials for pigmenturia in the horse
- Urolithiasis
- Cystitis
- Urethral rents
- Vaginal varicoceole/genital tract disease
What is the most common cause of PUPD in the adult horse?
Apparent psychogenic polydipsia
List the differentials for PUPD in the adult horse
- Psychogenic polydipsia
- PPID
- Chronic renal failure
- Hepatic insufficiency
- Diabetes mellitus
- Diabetes insipidus
- Physiological causes
In a horse presented for PUPD, would would anaemia, elevated BUN (urea >15mmol/L, creatinine >300mmol/L), hypercalcaemia, isosthenuria and a low urine creatinine:serum creatinine ratio be suggestive of?
Chronic renal failure
In a horse presented with PUPD, what would polycythaemia be suggestive of?
Dehydration, suggesting PU is primary problem rather than PD, i.e. diabetes insipidus
In a horse presented with PUPD, what would neutrophilia be suggestive of?
Glucocorticoid response or inflammatory disease
In a horse presented with PUPD, what are the differentials for low urea and creatinine and how can these be differentiated?
- Hepatic insufficiency
- Or psychogenic PD and medullary washout
- Differentiate based on GGT, GLFH and bile acids
In a horse presented with PUPD. what would persistent hyperglycaemia be suggestive of?
PPID
In a horse presented with PUPD, what are the differentials for hypercalcaemia?
- Chronic renal failure
- Paraneoplastic causes
What causes of PUPD produce hyposthenuric urine in the horse?
Diabetes insipidus and psychogenic polydipsia
What causes of PUPD may cause glucosuria in the horse?
- Diabetes mellitus
- PPID
- Acute stress
- A2As
Compare the urine creatinine: serum creatinine ratio in horses with dehydration vs CRF
- Dehydration: increased ratio
- CRF: lower ratio
Describe the clinical signs of psychogenic polydipsia in the horse and how is it diagnosed?
- Significant PU, often flooded stables
- PD as a stable vice
- May be result of excessive salt consumption
- Diagnosis of exclusion
Describe the management of psychogenic polydipsia in the horse
- Restrict salt intake
- Restrict water intake
- Alleviate boredom
- Increase feeding frequency of roughage
Outline the mechanisms by which PPID causes PUPD
- High cortisol → hyperglycaemia → osmotic diuresis
- Cortisol antagonism of ADH in collecting ducts
- Adenoma growth may impinge on posterior pituitary and hypothalamus leading to decrease ADH → central diabetes insipidus
Explain the diagnosis and treatment of PPID
- Plasma ACTH
- Positive if >29pg/ml most months, >47pg/ml in Aug, Sept, Oct
- Treat with pergolide, recheck ACTH in 4 weeks
List the differentials for a foal that is weak, trembling, has a distended abdomen, bradycardic a few days after birth?
- Bladder rupture
- Sepsis
- PAS
- Persistent meconium impaction
- Colic for other reasons
Describe the clinical signs of bladder rupture in a foal
- Normal at birth
- First 24-36hours tranguria/pollakiuria
- Day 2-4 dull demeanour, abdomianl distension
- May void small amounts of urine
- Cardiac arrhythmias e.g. bradycardia due to hyperK
- Muscle fasciculations
- Colic
- Sepsis
What diagnostic investivation findings would be likely in a rupture bladder in a foal?
- HyperK, high creatinine, low Na and Cl
- Metabolic acidosis
- Abdominocentesis shows periteonal:serum creatinine ratio >2:1
- Abdominal ultrasound shows large amounts of free fluid in abdomen and collapsed bladder
- ECG shows hyperK related changes (bradycardia, wide WRS, prolonged P wave)
Describe the treatment for a rupture bladder in a foal
- Stabilise pre-op: IV NaCL 0.45-0.9% +5% glucose 1-3L
- If hyperK (>5.5mEq/l): IV Ca gluconate 1ml/kg over 10 mins, IV NaHCO3 1-2mmol/kg over 15 mins, 50% dextrose IV 2ml.kg over 5 mins, insulin if significant ECG abnormalities or poor response to initial fluids
- Drain urine from abdomen pre-op
- Broad spec ABs
- Consdier gastric ulcer prophylaxis
- Ensure passive transfer of Abs occurs
- Surgery to repair defect, remove enlarged umbilical structures
- Place indwelling catheter for 48 hours to decrease bladder distension at repair site
Discuss the prognosis for bladder rupture in the foal
- If non-septic, good prognosis
- 95% success rate if treated early and otherwise healthy
- If concurrent infection of GI issue, 50%
- In septic or premature, complications e.g. peritoniitis, incisional complications, adhesions more common
- Repeat ruptures can occur
Explain the haematological and biochemical parameters that may be abnormal in a foal affected by placental disease
- Serum creatinine may be 30-40% higher in first 3 days
- Do not worry if otherwise healthy and urinating normally
- If does not fall after 3 days, investigate renal causes
