Veterinary Society of
Surgical Oncology

General Considerations

  • leiomyosarcoma and leiomyoma are the most common mesenchymal tumors of the bladder in cats and dogs
  • leiomyosarcoma and leiomyoma account for up to 12% of all primary bladder tumors
  • leiomyosarcoma and leiomyoma are usually small and located in the trigone or neck of the bladder
  • leiomyomas are asymptomatic unless large size
  • leiomyosarcoma can be differentiated from leiomyoma using AgNOR
  • leiomyosarcomas are locally aggressive and infrequently metastasize to regional lymph nodes, liver, pancreas, kidneys, intestines, omentum, diaphragm, heart, and lungs

Clinical Signs

  • dysuria, hematuria, pollakiuria, and stranguria
  • vaginal discharge
  • urinary obstruction
  • incontinence

 Urinalysis and Urine Sediment Cytology

  • hematuria and proteinuria are consistent findings on urinalysis due to ulceration of the urothelial mucosa
  • bacteruria, pyuria, and positive urine cultures are common in cats
  • bladder wash cytology may improve diagnosis capabilities by reducing contaminants

Blood Tests

  • hematology and serum biochemistry findings are usually normal or non-specific
  • mild to moderate normochromic, normocytic anemia can be caused by either hematuria or bone marrow suppression secondary to chronic disease
  • uremia may result from neoplastic obstruction of urinary outflow or age-related renal failure

Imaging Studies

Survey Radiographs

  • imagining techniques include survey abdominal and thoracic radiographs, contrast radiography, and CT
  • survey radiographs: sublumbar lymph node enlargement, renomegaly, and metastatic disease in the pulmonary parenchyma or skeleton, particularly lumbar vertebrae and pelvis
  • positive contrast cystography is useful for identification of mucosal abnormalities and space occupying lesions
  • excretory urogram is indicated to determine the location and extent of obstructive urinary tract disease when the urethra cannot be catheterized


  • ultrasonography is recommended to determine the location and extent of bladder involvement, regional lymph node size and appearance, and involvement of adjacent anatomical structures such as the colon


  • biopsy is required for definitive diagnosis of urinary tract tumors
  • biopsy techniques include FNA, needle biopsy, catheter biopsy, cystoscopic, and open surgery
  • percutaneous biopsy procedures are not recommended due to the risk of tumor seeding
  • catheter biopsy techniques correlate with surgical biopsy results in 73% of urethral and bladder tumors
  • inflammation secondary to necrosis and ulceration is common and may result in false-negative findings

Surgical Management

  • surgical techniques for management of bladder tumors include:
  • palliative procedures: tube cystostomy ± partial cystectomy
  • curative-intent procedures: partial cystectomy and total cystectomy with urinary diversion
  • cystostomy tube can be placed percutaneously or with either laparoscopic or open surgery
  • complications: stranguria, pollakiuria, hematuria, urine leakage around the stoma, and vesicoureteral reflux which predisposes to ascending UTI and tumor seeding of the upper urinary tract
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