+ 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

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

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
Polycythemia is a reported paraneoplastic syndrome with renal tumors
Uremia may result from obstruction of urinary outflow, bilateral renal tumors, or age-related renal failure

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 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

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

Ventral midline celiotomy ± pubic symphyseal separation or pelvic osteotomy for greater exposure
Ventral midline approach recommended to evaluate and remove regional lymph nodes

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

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

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

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