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TUMOURS OF
THE URINARY BLADDER
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Provet for educational purposes only.
You should seek the advice of
your veterinarian if your pet is ill as only he or she can correctly advise
on the diagnosis and recommend the treatment that is most appropriate for
your pet.
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Description
Tumours of the lower urinary tract (bladder and urethra) are more common in dogs
and cats than tumours of the upper urinary tract (kidneys or ureters). In dogs
most of these tumours (90-97%) are reported to be malignant. Bladder tumours in
cats are relatively rare.
The most common tumours of the bladder in both cats and
dogs are Transition Cell Carcinoma (TCC)
- which is a malignant cancer of the epithelial lining.
Other malignant tumours reported are :
a) Dogs
- Transition Cell Carcinoma (TCC)
- Squamous cell carcinoma (SCC)
- Adenocarcinoma
- Carcinoma (undifferentiated)
- Leiomyosarcoma
- Sarcoma (undifferentiated)
- Fibrosarcoma
- Haemangiosarcoma
- Rhabdomyosarcoma (especially in young dogs)
b) Cats:
- Transition Cell Carcinoma (TCC)
- Squamous cell carcinoma
- Leiomyosarcoma
- Haemangiosarcoma
- Adenocarcinoma
- Rhabdomyosarcoma (young cats)
- Lymphoma (young cats)
The most common benign tumours of the bladder in dogs
is the Papilloma and
in the cat the Leiomyoma
Other benign tumours of the bladder include :
a) Dogs
- Papilloma
- Leiomyoma
- Fibroma
- Haemangioma
- Adenoma
b) Cats
- Leiomyoma
- Fibroma
- Haemangioma
Cause
Bladder tumours usually occur
spontaneously in older animals with no recognisable underlying cause, however
carcinogens in the urine may be involved
Exposure to insecticidal "dips" (not other
methods of insecticidal treatment) is a risk factor for the development of
bladder cancer. Dipping dogs twice a year increased the risk by 1.6 times, and
dipping more than twice a year increased the risk by 3.5 times. Other
identified risk factors for bladder cancer include
- advancing age (see below)
- living in close proximity to marshes (possibly
due to insecticidal spraying against mosquitoes)
- obesity
- cyclophosphamide administration in dogs
Breed Occurrence
Dogs
Females have a higher risk of developing bladder
tumours than males, although males have been found to have a higher incidence
(11:2) of urethral TCC .
Airedales, Beagles, Collies, Scottish Terriers, and
Shetland Sheepdogs are predisposed to develop lower urinary tract tumours.
In young dogs rhabdomyosarcoma is most likely to occur
at 1-2 years of age, and the St Bernard seems to be predisposed to develop it.
The age of onset of other tumours is typically older
dogs - average age 9.5 years
Cats
TCC occurs most frequently in older cats - average age
13 years, but has been reported to occur between 4-20 years of age. SCC occurs
6-15 years of age; Adenocarcinoma - 6-13 years of age,
Leiomyosarcoma - 3-10 years of age; Leiomyoma 5-14 years of age.
Signs
The clinical signs of bladder cancer are similar to
cystitis or urinary tract obstruction, irrespective of the type of tumour and
include the following :
- Blood in the urine (Haematuria)
- Increased frequency of urination
- Difficulty passing urine (dysuria) - straining
(tenesmus) or inability to pass any urine
- Anorexia
- Bladder distension
- Soft tissue mass palpable in the bladder wall
- Regional lymph nodes may be increased in size
- Increased urine production - polyuria occurs
sometimes
- Increased thirst (polydipsia) occurs sometimes
- Urinary incontinence occurs sometimes
Complications
In over 50% of dogs with TCC metastatic spread will
have occurred by the time the diagnosis is made. In contrast, metastatic
spread is rare at the time of diagnosis of bladder tumours in cats.
Tumours in this region of the body may spread to
and involve other local structures such as regional lymph nodes (eg iliac or
sublumbar) or vertebrae, and sometimes causing serious effects. For
example, a leiomyoma in a cat has been reported to involve the
retroperitoneal region causing hindleg paresis, lameness has been caused in
dogs when the tumour involves local skeletal structures.
It is common for malignant tumours of the bladder
in the dog to also involve other parts of the urinary tract including the
urethra, vagina prostate, and sometimes the ureter and kidneys. Unlike dogs,
it is rare for bladder tumours in cats to involve other parts of the
urinary tract, and they are often located at sites different to the trigone
region.
Secondary metastatic spread to the lungs may also
occur so chest radiographs should be taken.
Diagnosis
The presence of a bladder tumour can be identified by
one or more of the following procedures :
- Digital examination per rectum
- Digital examination per vagina
- Abdominal palpation
- Abdominal imaging by radiography (plain, contrast or
double-contrast studies), CT scan or MRI
- Abdominal ultrasonography
- Secondary azotaemia may be found on blood screens
- Cystoscopy
- Cystotomy
Definitive diagnosis of the type of tumour can be made
by :
- Biopsy
- Cytology of urine sediment (preferably collected by
aspiration) - care needed in interpretation
Treatment
Surgical excision is the treatment of choice, and early
diagnosis and removal increase the chances of success. However. surgical
excision may be difficult if the tumour involves the trigone of the bladder -
without damaging or translocating the ureters. To access tumours involving the
urethra it may be necessary to split the pubis. Excision
of benign tumours is potentially curative, whereas excision of malignant tumours
is associated with a relatively high recurrence rate of approximately 25%, and
for TCC in dogs about 50% will have spread by the time the condition is
diagnosed. Other treatments have included :
- Radiation therapy - unfortunately often results in
incontinence due to fibrosis, and recurrence is common
- Chemotherapy for dogs - using cisplatin, carboplatin,
mitoxantrone, or piroxicam. None of these has proved itself as the most
effective treatment regimen. Chemotherapy is not used widely for bladder
cancer in cats.
Prognosis
Good for benign tumours which
can be resected completely . Guarded for malignant tumours and guarded to poor
for tumours with evidence of metastatic spread.
Long term problems
Include :
- Local recurrence at site of
original tumour
- Metastases
- Incontinence
- Seeding of the tumour
following surgery or biopsy
Updated October 2013
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