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TUMOURS OF
THE URINARY BLADDER
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Provet for educational purposes only.
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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
- 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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