Page 674 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

652 PART IV Specific Malignancies in the Small Animal Patient

in the bladder and urethra, damaged urothelium, and, in some for feline iUC and possible role of RT requires more study. Surgi-
cases, potentially compromised immune function. 71,72 UTIs are cal approaches and the placement of stents and cystostomy tubes
35,90–92
to improve urine flow have been reported in cats with iUC.
problematic because they can result in worsening clinical signs,
VetBooks.ir the false impression of cancer progression, and further malignant Canine Urethral Tumors
transformation, invasion, and metastasis secondary to inflamma-
tion. 73–75 Antibiotic use can negatively affect the immune response
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through changes in the microbiome and other mechanisms. Most urethral tumors in dogs are malignant epithelial tumors
Another major problem with UTIs is the increasing resistance including iUC and squamous cell carcinoma, with other cancers
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to antibiotics. 71,76–79 For example, between January 2013 and being less common. Staging procedures and treatment recommen-
February 2015, 168 resistant bacterial isolates from urine were dations for urethral iUC are generally the same as for iUC located
reported at the Purdue University Veterinary Teaching Hospital, in the bladder. It is important to note that granulomatous/chronic
and 60% of the resistant isolates were from dogs with TCC (Fulk- active urethritis comprised 24% of urethral lesions in a series of 41
erson, unpublished data). In a 1-year period, 7 of 57 dogs with dogs, and the clinical signs and lesions associated with granuloma-
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iUC developed infections that were sensitive only to nephrotoxic tous urethritis can mimic iUC. Complete urethral obstruction
antibiotics, very expensive antibiotics, or were not sensitive to any has been reported with granulomatous urethritis. Histopathology is
1
antibiotics tested. These issues point out the need to appropri- particularly important for urethral masses to rule out granulomatous
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ately treat UTIs, but to also refrain from prescribing antibiotics urethritis, as treatment and prognosis differ from those of iUC.
when not indicated, as this can promote antibiotic resistance. A
positive urine culture, especially with a low colony count in the Canine Renal Tumors
absence of worsening clinical signs and supporting findings on
urinalysis, is not an indication to treat with antibiotics. Canine renal cancer includes renal cell carcinoma (RCC), adeno-
If a dog with iUC develops new or progressive lower urinary carcinomas, iUC, papillary cystadenocarcinomas, and less com-
tract signs, a urinalysis with sediment evaluation should be per- monly, sarcomas. 94–97 Nodular dermatofibrosis in association with
formed. If the urinalysis reveals pyuria or the presence of intra- renal cystadenocarcinoma and uterine tumors has been reported,
cellular bacteria, a urine culture is recommended. Because of the mostly in German shepherd dogs. 98,99 This condition arises as a
risk of tumor seeding, urine samples for culture are collected via result of a dominantly inherited missense mutation in FLCN, a
midstream voiding or through a urinary catheter. While waiting tumor suppressor gene coding for the protein folliculin, and is
on culture results, an initial antimicrobial choice should target similar to Birt–Hogg–Dubé syndrome in people. 98,99
Escherichia coli and Staphylococcus spp., which are among the most Epithelial renal tumors and sarcomas tend to occur in older
common uropathogens in non–tumor-bearing and tumor-bear- dogs. Nephroblastoma has been reported in young dogs (includ-
94
ing dogs with UTIs. The authors typically prescribe amoxicil- ing a 3-month-old dog), middle-aged, and older dogs. 94–96
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97
lin–clavulanate or trimethoprim–sulfa pending culture results. A male predisposition has been reported. Clinical signs, when
Amoxicillin, doxycycline, and enrofloxacin (but not amoxicillin- present, include hematuria, pain in the area of the kidneys, a pal-
clavulanate or cephalexin) have been associated with resistance pable abdominal mass, bone pain secondary to hypertrophic oste-
80
patterns in cultures performed within 30 days after use. The opathy, or other nonspecific signs such as GI upset or behavior
benefits and risk of other approaches to treat or control UTIs, changes. 94–96,100
such as methenamine maleate or bacterial transfer, have not yet Laboratory findings can include mild to moderate anemia,
been determined. 81,82 neutrophilia, azotemia, elevated alkaline phosphatase, hypoalbu-
minemia, hypercalcemia, and paraneoplastic polycythemia sec-
Prognosis ondary to erythropoietin production. 94,101–104 In a case report of
a dog with renal carcinoma and suspected paraneoplastic leukocy-
Although iUC is not usually curable in dogs, it is considered very tosis, immunohistochemistry revealed expression of granulocyte-
treatable because of the 75% chance of cancer control or remis- macrophage colony-stimulating factor by the tumor. 103
sion with treatment. The quality of life in most dogs is excellent. Clinical staging should include thoracic and abdominal imaging.
Survival has been strongly associated with the TNM stage at the Tumor extension into the caudal vena cava is possible; thus CT may
1,3
time of diagnosis. Factors associated with a more advanced be useful for surgical planning. Evaluation of glomerular filtration
TNM stage at diagnosis include younger age (increased risk of rate via scintigraphy can also be useful. Histopathology is required
nodal metastasis), prostate involvement (increased risk of distant for a definitive diagnosis and can be obtained by ultrasound-guided
metastasis), and higher T stage (increased risk of nodal and distant percutaneous biopsy or at the time of nephrectomy. Immunohisto-
1,3
metastasis). chemistry can help differentiate subtypes of RCC. 105
Nephrectomy remains the treatment of choice for dogs with
Feline Urinary Bladder Tumors unilateral renal tumors with no evidence of metastasis and normal
renal function. Even in dogs with metastasis, surgery can be pallia-
Bladder cancer is rarely reported in cats. iUC is the most fre- tive. Renal lymphoma is typically treated with chemotherapy (see
quently reported form of feline bladder cancer, with mesenchymal Chapter 33), but effective chemotherapy protocols have yet to be
tumors, lymphoma, and other tumors being less common. 83–89 described for most primary renal tumors.
Clinical signs of iUC in the cat are similar to those in the dog. In In one study, the MSTs were 16 months for 49 dogs with
84
contrast to dogs, more than half of iUCs in a series of 20 cats were renal carcinomas, 9 months for 28 dogs with renal sarcomas, and
away from the trigone. Cats in this series were treated with sur- 6 months for 5 dogs with nephroblastomas. Higher mitotic
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gery, cytotoxic chemotherapy, COX inhibitors, or combinations index, increased COX-2 expression, specific histologic subtypes,
84
thereof, and the MST was 261 days. As in canine and human and Fuhrman nuclear grade have reported negative prognostic
89
iUC, most feline iUCs express COX-1 and COX-2. The MST of value for RCCs. 106,107 The MSTs for dogs with a mitotic index of
89
11 cats treated with meloxicam was 311 days. The optimal drugs <10, 10 to 30, and >30 were 1184 days, 452 days, and 187 days,