Retrospective evaluation of and risk factor analysis for presumed fluid overload in cats with urethral obstruction: 11 cases (2002–2012)

Objective To describe patient characteristics, treatment, and outcome in male cats with urethral obstruction (UO) and fluid overload (FO), and to determine risk factors for the development of FO. Design Retrospective case‐control study from 2002–2012. Animals Eleven client‐owned cats with UO that developed respiratory distress secondary to suspected FO and 51 control cats with UO without FO. Interventions None. Measurements and Main Results Medical records of cats with UO and FO were identified. FO was defined as the development of respiratory distress secondary to pleural effusion or pulmonary edema while receiving IV fluids. To identify risk factors for FO, variables for cats that developed FO were compared with variables from a randomly selected control group of unaffected UO cats during the same time period. Variables analyzed included patient signalment, previous medical history, serum biochemical data, respiratory rate, cardiac auscultation abnormalities, admission systolic blood pressure, intravenous fluid administration, thoracic imaging, treatment, duration and cost of hospitalization, and outcome. Echocardiogram identified heart disease in 5/6 cats with FO. Cost (2.9 times as much) and median duration of hospitalization (4.1 vs 1.8 days) were significantly greater in cats with FO. Cats with FO were more likely to have received a fluid bolus (odds ratio [OR]: 5.1; 95% confidence interval [CI]: 1.3, 20, P = 0.014), developed a heart murmur (OR: 4.5; 95% CI, 1.1–18, P = 0.028) or a gallop sound (OR: 75; 95% CI, 8.1–694, P < 0.0001). Conclusions FO is a possible complication of the treatment of UO. The administration of a fluid bolus on presentation, and the development of a heart murmur or gallop sound during treatment were the most clinically useful risk factors identified. The development of FO is associated with significant increases in both the cost and length of hospitalization, but was not associated with increased mortality.