Causes of swollen lymph nodes in dogs in the Mediterranean region

Abstract

Lymphadenopathy is a common clinical concern in dogs. Causes of lymphadenopathy include neoplasia, infection, and immune-mediated diseases. Seasonal infectious diseases should be considered as a potential cause of lymphadenopathy in endemic regions, such as the Mediterranean region. Therefore, the purpose of this study was to evaluate the causes of peripheral lymph node enlargement in dogs in a Mediterranean region (north‑eastern Spain). In addition, we aimed to assess the relationship between peripheral lymphadenopathy and other clinical data. Medical records of dogs admitted to 2 referral hospitals in Barcelona (Spain) with peripheral lymphadenopathy and cytological evaluation of lymph nodes, during a 4-year period (2015-2019) were included. One hundred and thirty dogs met the inclusion criteria. The most common final clinical diagnoses were lymphoproliferative neoplasia (36%) and dermatological disease (18.4%), followed by vector borne infectious disease (VBID; 16.5%). In the VBID group, 19 dogs were positive for Leishmania infantum and 2 dogs were positive for heartworm antigen. The presence of lymphadenopathy as the only clinical sign, generalized peripheral lymphadenopathy and internal lymphadenopathy was more frequent in dogs with lymphoma. The patients with metastatic neoplasms had significantly more localized lymphadenopathy compared to the other diagnosis groups. Twenty percent of the dogs had fever and this was more frequent in the immunemediated disease group. Our findings suggest that lymphoma is the most likely cause of lymphadenopathy in dogs. Clinicians should consider lymphoproliferative neoplasia in dogs with general peripheral lymphadenopathy concurrent with internal (abdominal or thoracic) lymphadenopathy and without other clinical signs. A higher incidence of immune-mediated disease was found in the population of febrile dogs included in this study.