Efficiency of ultrasound-guided aspiration of medial retropharyngeal lymph node in dogs.

The purpose of this retrospective cross-sectional study was to assess the diagnostic yield of ultrasound-guided aspiration of the medial retropharyngeal lymph node (MRPLN) and to report factors on computed tomography (CT) evaluation that are predictive of obtaining a diagnostic sample. A secondary objective was to report CT size reference ranges for cytologically confirmed normal MRPLNs in dogs. Medical records and CT images of 69 dogs were retrospectively reviewed. The diagnostic yield of ultrasound-guided aspiration on MRPLNs was 47.5%. Six lymph nodes were positive for metastasis with various cancers. Only rostral height was predictive of the diagnostic yield. The Pearson correlation coefficient and Spearman's Rho tests suggested that the age of the dog has significant negative linear correlation with the size of MRPLNs while the weight has positive correlation. Overall, ultrasound-guided aspiration of MRPLN has low diagnostic yield in normal size lymph nodes. Prior case selection based on CT evaluation may increase the probability of diagnostic samples.