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Rhabdomyosarcoma of the Urinary Bladder in Dogs

Rhabdomyosarcoma is a very rare type of malignant and metastasizing (spreading) tumor derived from stem cells, or originating in the striated muscle that surrounds the developing Müllerian or Wolffian ducts. Müllerian ducts begin as two ducts in the female embryo, developing into the vagina, uterus and oviducts. Wolffian ducts begin in the male embryo, developing into the tubes that carry sperm from the testicles through the penis (vas deferens).

Rhabdomyosarcoma of the urinary bladder may also be reported as botryoid rhabdomyosarcomas due to their tendency to take on the appearance of grape clusters. They often spread to the internal organs, and to the lymph nodes.

Symptoms and Types

• Predominantly consistent with a lower urinary tract infection
• Blood in the urine
• Straining to urinate
• Frequent urination in small quantities
• Urine retention/inability to urinate

Causes

Idiopathic (unknown)

Diagnosis

You will need to provide a thorough history of your dog's health leading up to the onset of symptoms. Your veterinarian will perform a complete physical exam on your dog, with a blood chemical profile, a complete blood count, a urinalysis and an electrolyte panel. If rhabdomyosarcoma is in fact present, the urinalysis will show bloody urine, and a cytologic (microscopic) examination of urine sediment will indicate rhabdomyosarcoma.

The bladder may be internally examined using ultrasound, or double-contrast cystourethrography imaging (which uses an injection of dye into the bladder and urethra to show the structures more distinctly). An intravenous pyelography can also be used for examining the kidney and bladder, to evaluate any trigonal mass, and to assess the ureters (the tubes that carry urine from the kidney to the bladder), and the renal pelvis (the center of the kidney where the urine funnels into the ureters). This method also uses the injection of a dye to visually examine the internal structure of these organs.

A definitive diagnosis can be made from an examination of the diseased tissue (histopathology) using tissue samples (biopsies) obtained from exploratory surgery, or from cystoscopy – an examination of the bladder and ureters, performed by inserting a tube through the urethra.