Red blood cell distribution width may help distinguish canine gastrointestinal lymphoma from chronic inflammatory enteropathy and be a prognostic indicator.

[OBJECTIVE] This study aimed to evaluate the diagnostic and prognostic utility of RBC distribution width (RDW) for gastrointestinal lymphoma (GIL) versus chronic inflammatory enteropathy (CIE) in dogs.

[METHODS] Medical records of dogs diagnosed with GIL or CIE based on histopathological examination of endoscopic gastrointestinal biopsy specimens between April 1, 2016, and March 31, 2024, were retrospectively reviewed. Red blood cell parameters were measured at diagnosis via an automated hematology analyzer (ProCyte Dx; Idexx Laboratories Inc). Canine Chronic Enteropathy Clinical Activity Index (CCECAI) score was recorded. The diagnostic performance of RDW and CCECAI was assessed with logistic regression and receiver operating characteristic curve analyses. The prognostic value was evaluated via Kaplan-Meier survival analysis and Cox proportional hazards modeling.

[RESULTS] 56 dogs were diagnosed with GIL, and 60 were diagnosed with CIE. The RDW was significantly higher in the GIL group compared to the CIE group, with an area under the curve of 0.63. In logistic regression analysis, RDW (OR, 1.25) and CCECAI (OR, 1.27) were identified as independent predictors of GIL versus CIE. Kaplan-Meier survival analysis for GIL showed that the median overall survival time (OST) was significantly shorter for dogs with RDW > 18.3% (134 days). In the multivariable Cox proportional hazards analysis, RDW remained an independent prognostic factor for OST for GIL.

[CONCLUSIONS] RDW was independently associated with a diagnosis of GIL and with shorter OST in dogs with GIL.

[CLINICAL RELEVANCE] RDW may provide information when considering endoscopic biopsy and prognosis in dogs with suspected GIL.