Urinary tract diseases in the cow
Whilst some diseases of the urinary tract present suddenly (eg urethral
rupture), many conditions will reach an advanced stage before they are
presented by the owner as the normal clinical signs of urinary tract disease
(polyuria, polydipsia, haematuria etc.) are not easy to notice in many cattle
husbandry systems.
Diseases of the urinary system can be categorised as pre renal, renal and post
renal. Pre renal diseases are diseases of other systems that produce clinical
signs of renal disease. Renal diseases primarily affect the kidneys and post
renal diseases affect the ureters, bladder or urethra.
Pre renal causes of renal insufficiency are any causes that lead to reduced
perfusion of the kidneys, either by a reduction in cardiac output or an insult to
the circulatory system, for example congestive heart failure, ruminal tympany,
dehydration, hypovolaemia, shock and septicaemia. In these cases, treatment
of the primary disease, if possible, will hopefully lead to correction of renal
function.
Primary renal disease can be caused by numerous causes including
pyleonephritis, glomerulonephritis, neoplasia, renal infarctions secondary to
septicaemia or cogenital defects such as renal cysts. Diagnosis of renal disease
is based on clinical signs described above, rectal palpation, biochemistry,
urinalysis and ultrasonography. Renal biopsy may also be of assistance. Rectal
palpation may reveal an enlarged or painful kidney. Biochemistry will reveal
elevated concentrations of urea and creatinine, magnesium and phosphate
concentrations may also be elevated in some cases and this usually indicates a
poor prognosis. Hypoproteinaemia is also a feature of advanced renal failure. A
urine sample can be obtained either by stroking the perineal area of most cows
or by catheterisation, the later being preferred for urine culture. A low urine
specific gravity in a dehydrated animal is very suggestive of renal failure. Trans
rectal ultrasonography may be useful in assessing any structural abnormalities.
Most cases of primary renal disease are well advanced at diagnosis as the
kidneys have a very large reserve of function, so over two thirds of the kidney
will be affected before any clinical signs become apparent, and even when
they do it may be some considerable time before they are noticed. For this
reason, the initial treatment should usually be supportive whilst the underlying
cause is diagnosed and specific treatment implemented. This initial treatment
should include intravenous fluid therapy at maintenance dose rates until urine
output is established, then this can be increased to 2 -3 times maintenance and
diuretic therapy (eg frusemide) may be of help at this time.
Post renal causes of renal insufficiency include any condition that impairs urine
out flow.
Disease of the ureters is very uncommon; however blockage or rupture could
occur but would probably be untreatable by the time a diagnosis had been
reached.
Conditions affecting the bladder include cystitis, urolithiasis, prolapse and
rupture. Cystitis will usually present as haematuria, however it may go
unnoticed for some considerable time in most cattle husbandry systems.
Differential diagnoses for haematuria include babesiosis (red water fever) and
bacillary haemoglobinuria (red water fever). Bacillary haemoglobinuria is now
very rare in this country, babesiosis is caused by the parasites Babesia
divergens and B. major, which are tick borne, mainly occurring in spring and
autumn. Diagnosis can be confirmed on a blood smear and imidocarb
dipropionate is the appropriate treatment, vaccination is available abroad, but
not currently in this country. A diagnosis of cystitis can be confirmed by urine
culture, treatment should include a suitable antibiotic and possibly
antinflammatories. Urolithiasis is a relatively common finding in cattle,
however it is not significant unless calcium carbonate or triple phosphate
crystals are present. Clinical urolithiasis is most common in rapidly growing,
young male animals, especially those fed on a diet high in concentrates, or high
in phosphorus or animals grazed on pastures rich in clover silica or oxalate.
Clinical presentation will usually occur once the urethra has blocked at the
level of the sigmoid flexure. Initially clinical signs will include discomfort and
anuria, if diagnosed at this point it may be possible to pass a catheter and flush
the bladder, however this condition will rarely be noticed until either the
urethra or the bladder has ruptured. Bladder rupture will result in a
uroabdomen on a peritoneal tape, repair may be possible via a laparotomy.
Urethral rupture may be treated by either placing an indwelling catheter and
allowing healing by secondary intention, or by perineal urethrostomy, which
can be performed under epidural anaesthesia in the standing animal. Bladder
prolapse through the urethra may occasionally occur associated with calving or
vaginal prolapse. This can often be gently replaced under epidural anaesthesia.