Short Takes: December 2011

Urethral Obstruction in Cats
Unfortunately, feline lower urinary tract diseases (FLUTDs) are common. Urethral obstruction (UO) is believed to occur more commonly in young cats and almost exclusively in male cats, although veterinary literature has limited information regarding the risk factors for UO.

The most common etiology of UO in cats is urethral plugs, and the most common signs of UO include stranguria, dysuria and pain, and varying degrees of systemic signs. The objectives of this study (“Urethral obstruction in cats: predisposing factors, clinical, clinicopathological characteristics and prognosis,” Journal of Feline Medicine and Surgery, 2011) were to identify risk factors for UO, to illustrate clinical and clinicopathological signs, outcome and recurrence, as well as risk factors for mortality and recurrence.

The study compared 82 cats with UO to 82 sex and time matched control cats. Indoor-outdoor cats were found to have a decreased risk for UO, while increased body weight was found to be a risk factor for UO over the control group. Cats with UO were younger than the control cats, and the proportion of cats with UO consuming dry food was higher than the control cases. Even though UO is a life-threatening condition, the survival rate was actually high in this study. And the recurrence rate in this study was relatively low.

Ionized calcium was found to be significantly higher in survivors compared to non-survivors. Urine pH was overall significantly lower at presentation in those reoccurring cases. Presence of ionized hypocalcemia and hyperkalemia should alert veterinarians to the need for aggressive management and stabilization prior to de-obstructing patients under general anesthesia.

Treatment for FIV Infection
Feline immunodeficiency virus (FIV) is a natural lentivirus infection found in both domestic and wild cats, and the course of the disease is similar to that of human immunodeficiency virus. One of two drugs, zidovudine (ZDV, also known as AZT), has demonstrated some benefit in controlled trials in naturally infected cats (ZDV has been shown to lower viral burden in both acute and chronic infection, and to improve clinical signs in chronically infected cats). Anemia is the most common and significant side effect associated with ZDV that resolves once  the dosage is lowered or discontinued.

Because there is clearly a need for more effective drugs with fewer side effects for FIV treatment, the authors evaluated a compound related to ZDV, fozivudine (FZD), in a controlled experimental trial (“Fozivudine tidoxil as single-agent therapy decreases plasma and cell-associated viremia during acute feline immunodeficiency virus infection,” Journal of Veterinary Internal Medicine, 2011).

Data from the study showed that FZD is effective at lowering viral load the first two weeks of FIV infection, and may also decrease early FIV-associated lympholysis. The adverse effects associated with ZDV administration — including anemia — were not evident in any of the cats treated with FZD at the dosage used during the study. Further investigation is needed to assess optimal dosages for antiviral activity of the drug.

Therapy for Feline Lymphoma
Chemotherapy has primarily been the first choice of therapy for feline lymphoma. Cats generally respond well to chemotherapy protocols, with response rates ranging between 50 and 75 percent — depending on protocol, tumor grade and the location of the lymphoma. Radiation therapy in feline lymphoma is often used in nasal, extranodal or single node lymphoma. The authors chose to conduct a retrospective study of the medical records of 11 cats with gastrointestinal lymphoma (“Abdominal irradiation as a rescue therapy for feline gastrointestinal lymphoma: a retrospective study of 11 cats [2001-2008]”, Journal of Feline Medicine and Surgery, 2011).

All the cats had relapsed or resistant lymphoma, and they were evaluated to determine the efficacy of radiation therapy when used in a rescue therapy setting. The most common clinical sign noted prior to diagnosis was weight loss. The cats received two fractions of radiation delivered over two days, and there was a response in 10 of 11 cats. The overall median survival duration was 355 days while the median survival duration after radiation therapy was 214 days. Cats that were anemic tended to have lower overall survival rates, even with radiation therapy.

Acute effects of radiation were not noted, except one cat that had a limited duration of loss of appetite. The results indicated that at this dose of radiation, abdominal radiation therapy in the rescue setting for feline gastrointestinal lymphoma appears well tolerated.