Retrospective evaluation of the prevalence and risk factors associated with red blood cell transfusions in cats with urethral obstruction (2009-2019): 575 cases

Objective: To evaluate the prevalence of red blood cell (RBC) transfusions and factors associated with the need for transfusion in cases of feline urethral obstruction (FUO). Secondarily, to compare survival to discharge in cats receiving an RBC transfusion versus those that did not. Design: Retrospective, multi-institutional study from 2009 to 2019. Setting: Four university teaching hospitals. Animals: Six hundred twenty-two total occurrences of FUO in 575 cats. Interventions: None. Measurements and Main Results: Medical records were retrospectively reviewed for pertinent information. The overall prevalence of severe anemia (PCV < 0.20 L/L [<20%]) at presentation was 1.0% (6/622). The prevalence of RBC transfusions during hospitalization was 2.1% (13/622). Cats that received an RBC transfusion weighed significantly less than those that did not (4.9 vs 5.8 kg; P = 0.034) and had a lower PCV at presentation (0.30 L/L [30%] vs 0.41 L/L [41%]; P < 0.001). Hospitalization time (240 vs 72 h) and indwelling urinary catheter time (168 vs 48 h) were significantly longer in cats receiving a transfusion compared with those that did not (P < 0.001). Creatinine concentrations were not significantly associated with transfusion administration, while BUN was higher in cats receiving a transfusion (15.35 mmol/L [43 mg/dL] vs. 11.78 mmol/L [33 mg/dL]; P = 0.043). Transfusion rates were significantly higher in cats undergoing perineal urethrostomy (5.5%) compared with those that did not undergo surgery (0.97%; P < 0.001). The overall survival to discharge rate was 96%. Cats not receiving an RBC transfusion were significantly more likely to survive to discharge than those that did (odds ratio: 14.7, 95% confidence interval: 1.8-37; P < 0.001). Conclusions: FUO is rarely associated with severe anemia and the need for RBC transfusions. In this study, cats receiving an RBC transfusion were less likely to survive to discharge; therefore, requiring a blood transfusion may be associated with a worse prognosis. In addition, the need for surgical intervention was associated with a higher prevalence of RBC transfusions.