GENERAL CONSIDERATIONS


General Considerations

•urethral tumors are rare

•sex predisposition in dogs: female

•TCC should occur in the proximal 3rd of the urethra in females and the entire urethra in males

•SCC should occur in the distal two-thirds of the urethra in females and the external urethral orifice in males

•TCC is the most common canine urethral tumor, but distal and diffuse SCC was the most common diagnosis in 1 study of 20 dogs with primary urethral tumors

•other urethral tumors include ADC, HSA, myxosarcoma, rhabdomyosarcoma, leiomyosarcoma, and LSA

•benign urethral tumors include adenoma, papilloma, and leiomyoma

•29% (5/17) metastatic rate with the regional lymph node the most common metastatic site

•DDx: granulomatous or chronic active urethritis



DIAGNOSIS


Clinical Signs

•hematuria, pollakiuria, and dysuria

•vaginal discharge

•urinary obstruction

•incontinence

•lameness may be caused by either skeletal metastases or hypertrophic osteopathy


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


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

•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

•pulmonary metastasis with urinary TCC has 4 radiographic patterns:

•diffuse unstructured increase in interstitial density which can mimic old age changes

•localized interstitial or alveolar infiltrates

•multiple interstitial nodules

•normal pulmonary opacities

•positive contrast cystography is useful for identification of mucosal abnormalities and space occupying lesions in the urethra

•excretory urogram is indicated to determine the location and extent of obstructive urinary tract disease when the urethra cannot be catheterized

•ultrasonography may be able to determine the location and extent of urethral lesions but is useful for detecting neoplastic involvement of regional lymph nodes and adjacent anatomic structures such as the colon

•transurethral cystoscopy is the principal method for the diagnosis of TCC in humans and has been used for the investigation of bladder diseases in cats and dogs

•transurethral cystoscopy provides a minimally-invasive method of assessing urethral mucosal surface and performing biopsies for staging and grading purposes


Biopsy

•biopsy is required for definitive diagnosis of urinary tract tumors

•techniques: FNA, needle biopsy, catheter biopsy, endoscopy, and 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 tumors

•inflammation secondary to necrosis and ulceration is common and may result in false-negative findings



TREATMENT


Chemotherapy

•MST 181 days with piroxicam alone, including 6% CR and 20% PR

•MST 220 days with cisplatin alone, including 0% CR and 25% PR with MST significantly longer for responders (445 days v 70 days)

•carboplatin is not effective in the treatment of canine TCC

•other chemotherapy agents include mitoxantrone, doxorubicin, and gemcitabine


Surgical Management


General Considerations

•ventral midline celiotomy ± pubic symphyseal separation or pelvic osteotomy for greater exposure

•ventral midline approach recommended to evaluate and remove regional lymph nodes


Tube Cystostomy

•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


End-to-End Anastomosis

•small, localized and benign lesions can be excised with subsequent end-to-end anastomosis

•advanced lesions in proximal urethra may require urinary diversion techniques (i.e., ureterocolonic or trigonal-colonic anastomosis) or permanent tube cystostomy

•survival times range from 2-22 months


Vaginourethroplasty

•indications: distal urethral tumors

•approach: episiotomy or ventral midline celiotomy with pubic symphyseal separation

•urethra transected minimum 1 cm proximal to lesion

•bladder catheterized through transected proximal urethral segment to allow urine diversion from surgical field

•distal urethral segment isolated from the vagina dorsally and resected with the external urethral orifice and urethral tubercle of the vagina

•en bloc resection of urethra and ventral vaginal wall was performed if tumor invaded vaginal wall

•cranial vagina and cervical remnants resected following ligation of uterine arteries

•vaginal resection is performed to allow end-to-end anastomosis of the proximal urethra to the caudal vagina

•complications are uncommon and include transient urinary incontinence and recurrent cystitis


Prognosis

•poor for urethral TCC as local recurrence or metastatic disease usually occurs within 6 months

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