Equine Urogenital Flashcards
Which kind of horses usually get urethritis?
What presenting signs may they have?
Usually older geldings with preputial or distal urethral conditions
Look for underlying conditions eg trauma, neoplasia
Owners present for malodorous sheath, swelling
May have red discharge on legs
How would you treat urethritis?
Clean urethral fossa +/- apply very mild topical antibacterial agents
(Urethral fossa accumulates crystals)
Give some initiating causes of cystitis
Urolithiasis, neoplasia, paralysis, catheterisation (primary bacterial cystitis is really rare)
How do you diagnose cystitis?
Urine sediment examination (>10 leucocytes/HPF+ >20 organisms/HPF)
Urolithiasis is more likely in which horses?
Geldings
Where are uroliths usually found?
Bladder
May also be in the kidneys or ureters
What are uroliths usually composed of?
Calcium carbonate
What are the 3 forms of urolithiasis?
- Yellow-green spiculated stone, easily fragmented
- Grey-white smooth stones-harder and contain more phosphate
- Sabulous urolithiasis-sludge usually secondary to bladder paralysis
Give some clinical signs of dysuria in horses
May see urine dribbling or scalding
(Owner may misinterpret for oestrus behaviour in females)
Less commonly may see colic or tenesmus
Give some factors which contribute to urolith formation?
- Tissue damage (eg secondary to renal damage)
- Prolonged transit time (eg neurological conditions)
- Nidus formation (eg area of necrotic tissue, leucocytes or desquamated epithelial cells)
- Reduced inhibition of crystal growth (mucous is a natural inhibitor)
Nephroliths and ureteroliths usually occur secondary to which other problems?
eg pyelonephritis, tubular necrosis, papillary necrosis (NSAIDs)
How do nephroliths and ureteroliths occur?
Obstruction causes dilation of the renal pelvis -> hydronephrosis
What can happen if both kidneys are affected by nephroliths or ureteroliths?
Renal failure
What frequently accompanies the calculi seen with nephroliths/ureteroliths?
Bacterial infection
How do you diagnose nephroliths/ureteroliths?
Palpation and/or US
What clinical signs may you see in a horse with cystic or urethral calculi?
Dysuria eg haematuria, stranguria, pollakiuria, pyuria
May see posturing to urinate (differentiate from oestrus in mare)
May see colic, urine scalding, loss of condition
How would you diagnose cystic or urethral calculi?
Palpation or endoscopy
How would you remove cystic and urethral calculi?
Surgically eg laparotomy, perineal urethrotomy in males
Females: calculi can be retrieved by forceps or hands after epidural
What should you give a horse after removing cystic/urethral calculi?
Antibiotics
Urinary acidifiers could be given but horses wont eat them
Don’t feed alfalfa as want to decrease calcium excretion
Salt to increase water consumption and diuresis
What is the normal water intake of a horse?
20L/day
Can increase to 90L with exercise/hot conditions
Give some differential diagnoses for PUPD in the horse
Most common: -Renal failure/disease -Cushings -Psychogenic water consumption (stereotypie) Less common: -Diabetes insipidus -Diabetes mellitus -Miscellaneous eg endotoxaemia
Describe the pathogenesis of PUPD with PPID/Cushings disease
Glucosuria and osmotic diuresis
Antagonism of ADH by cortisol
Impingement on the posterior pituitary, decreasing ADH
What range of urine specific gravity indicates renal failure?
1.008-1.010
Is a horse in renal failure if its specific gravity is <1.008? Why?
No because the kidney is still functioning as it is actively diluting the urine
What 2 things must be present to confirm renal failure?
Isosthenuria (check specific gravity)
Azotaemia (high blood urea and creatinine) with PUPD
How would you test for PPID?
Dexamethasone suppression test
What should you do with a PUPD horse that is not azotaemic to rule out different causes?
Water deprivation test (CI in azotaemic horses)
Measure urine SG, PVC, TPP and BW
Withhold water and monitor min. 12 hourly
Stop test after 24-48 hrs, if SG>1.025, if >12-15% loss of BWT, or 12g/L increase in TPP or azotaemic
If concentrates normally -not renal (either psychogenic or cushings)
Then rule out Cushings with endocrine testing
Modified water deprivation (modified 40ml/kg/day for 3-4 days, expect SG >1.025)
Response to ADH (with central diabetes insipidus)
Give some differential diagnoses for red urine
Haematuria
Pigmenturia
(differentiate by spinning down/sediment examination)
Give some causes of haematuria
Cystitis, pyelonephritis, urolithiasis
Urinary tract neoplasia
Drug toxicity (NSAIDs)
Urethral defects
Exercise-associated haematuria (usually microscopic)
Idiopathic renal haematuria and renal vascular anomalies
Give some causes of pigmenturia
Myoglobinuria (myopathy-exercise associated, elevated muscle enzymes)
Pasture-associated (Sycamore poisoning, very ill horse, unable to metabolise fatty acids so give glucose)
Give some causes of haemoglobinuria
IMHA (usually secondary in horses eg penicillin, strep equi abscesses)
Neonatal isoerythrolysis
Oxidative injury to RBCs (eg methaemoglobinaemia, haemolysis)
Equine Infective Anaemia
Piroplasmosis (Babesia)
DIC
Iatrogenic
What must you differentiate red urine from?
Red discharges eg squamous cell carcinoma of the penis can leave a reddish stain inside the HLs, or mares may have vaginal or other disorders causing haemorrhage
Give some pre-renal (haemodynamic) causes of acute renal failure
Hypovolaemia eg colitis, sweat after prolonged exercise
Volume redistribution eg effusions
Decreased cardiac output
Altered vascular resistance eg sepsis, endotoxaemia
Give some renal causes of acute renal failure
Primarily acute tubular necrosis secondary to ischaemia or nephrotoxin exposure
Less commonly glomerulonephritis (eg immune-mediated) or interstitial nephritis
What causes ischaemia of the kidneys?
Prolonged haemodynamic changes, renal infarction, NSAID administration (NSAIDs block vasodilators via COX-1)
Why is the medulla of the kidney more susceptible to ischaemic injury?
The medulla only receives 10-20% of blood flow to the kidneys
What % of cardiac output reaches the kidneys?
20%
Give some examples of nephrotoxins that can cause acute renal failure
Antibiotics (eg aminoglycosides, polymixin B)
Endogenous substances (eg Hb, myoglobin)
Others eg NSAIDs, heavy metals
Why is the cortex of the kidneys susceptible to toxins?
90% of blood flow is filtered by the cortex
Also, the kidney is responsible for the excretion of most drugs
What can exacerbate most drug toxicities?
Concurrent dehydration
What should you measure in horses on potentially nephrotoxic drug therapy?
Serum creatinine (not BUN as this is variable in the horse) Treat aggressively if creatinine rises significantly
Which is the most nephrotoxic aminoglycoside?
Neomycin
Where are aminoglycosides filtered?
Where are they reabsorbed?
Glomerulus (no metabolism)
Proximal tubular epithelial cells
Accumulation in proximal tubular cells interferes with cells function
Pre-treatment with what may reduce aminoglycoside nephrotoxicity?
Calcium
How does NSAID nephrotoxicity occur?
Renal medullary crest and papillary necrosis
Sloughing of the tubular epithelial cells
Give some clinical signs of NSAID nephrotoxicity
Usually referable to the primary problem (eg colic)
Anorexia and depression (uraemia, fluid, electrolyte and acid-base disturbances)
May be lack of response to therapy
How do you correct pre-renal azotaemia?
Fluid therapy
In renal failure, would you see high or low amounts of Na+ and Cl- in urine?
High (as they are usually conserved)
Besides azotamia and isosthenuria, how else could you diagnose renal failure?
Electrolyte imbalances (eg high Na+ and Cl- in urine)
Proteinuria, glucosuria
Metabolic acidosis
Sediment exam-casts, leucocytes, erythrocytes, bacteria
What kind of urine (pH) do carnivores and herbivores have?
Carnivores: acidic
Herbivores: alkaline
How do you treat acute renal failure?
IV fluids (0.9% NaCl or Hartmans) to improve renal perfusion, correct metabolic disturbances and induce diuresis Discontinue nephrotixic drugs (eg bute) where possible
Which fluids should you use when treating a horse for acute renal failure?
0.9% NaCl or Hartmans
Replace fluid deficits and maintain on twice maintenance
What should you monitor when treating a horse for acute renal failure?
BW, PCV, serum protein, serum biochemistry
Which diuretics could you use when treating acute renal failure?
Furosemide (1-2mg/kg IV qid)
Dopamine (renal vasodilator)
(Mannitol)
(DMSO)
Is chronic renal failure common in horses?
Rare
Is glomerular disease seen more as chronic or acute renal failure?
Chronic
Acute tubular necrosis may progress to chronic interstitial nephritis
Give some clinical signs of chronic renal failure
Chronic weight loss
Lethargy, poor coat, PUPD, poor performance (mild anaemia)
May see oral ulceration, gastroenteritis, excessive tartar and halitosis
How do you diagnose chronic renal failure?
Persistent isosthenuria (1.008-1.014) with azotaemia and clinical signs
Mild anaemia, mild hypoalbuminaemia
Electrolyte abnormalities-hypercalcaemia, low blood Cl-, low blood Na etc
US
Endoscopy of ureter samples to look at severity of kidney, culture and biopsy
What is the white sediment usually seen in horses urine?
Calcium carbonate crystals (as it’s normal for the kidneys to excrete Ca2+, opposite to SA)
How big should a normal kidney be?
14-15cm
How do you treat chronic kidney disease?
Palliative only
Ensure water and salt always available
Low protein diet to manage BUN
Decrease calcium if high calcium diet
What is the prognosis like for chronic renal failure?
If mild to moderate elevations in creatinine (<200U/L) -> long survival time
Poor long term prognosis of creatinine is higher
>800U/L -> grave prognosis (euthanasia)
How do you perform a Caslicks procedure?
Put horse in stocks Bandage tail Wash perineum LA Excise a thin band of mucosa (not skin) from each side (3-4mm) (dorsal commissure, level with Ischiatic tuber) Suture with 0 non-absorbable material Remove sutures 10-14 days later
What procedure would you do for a perineal reconstruction?
Gadds procedure
- Loss of perineal body
- Create a new shelf of tissue between rectum and anus
