Meet The Author
July 2026
Rachel Pollard DVM, PhD, DACVR
I currently reside in Davis, CA and I am the lead radiologist for Veterinary Educators and Team Scientists (VETS), LLC (https://imaging-vets.com/). This company provides research and teaching support for organizations in need of radiologist input. When not working, I enjoy telemark skiing with my husband, backpacking for hundreds of miles in the wilderness or playing Scrabble with my 2 sons.
Radiographic Detection of Intrathoracic Lymphadenomegaly in Dogs: How Useful Is It?
Gordon Lye, Rachel E Pollard, Angela Hartman, Sarah Pemberton, Michael S Kent, Allison L Zwingenberger
I was working with a resident on an oncology case where we had reported that there were no enlarged lymph nodes on thoracic radiographs. However, we found multiple enlarged lymph nodes on CT that was performed shortly thereafter. It sparked a discussion with the oncologist about how reliable thoracic radiographs were for detecting thoracic lymph node enlargement and no one could answer that question.
What is the primary knowledge gap your study aims to address?
We wanted to determine whether thoracic radiographs were a useful tool for screening for enlarged thoracic lymph nodes. This is particularly relevant when the presence or absence of thoracic lymphadenomegaly will have a direct impact on prognosis and treatment selection.
The Study Design
This study was a retrospective, analytical, cross-sectional, multicenter study of dogs presenting between January 2012 and January 2023. We did an electronic search of the medical records at the University of California-Davis William R. Pritchard Veterinary Medical Teaching Hospital (Davis, CA, USA), Animal Referral Centre (Auckland, New Zealand), and Inland Empire Veterinary Imaging (Spokane, WA, USA) to identify dogs that underwent multi-detector CT (MDCT) of the thorax using the search terms lymphadenomegaly and lymphadenopathy involving any or all of the intrathoracic LN clusters. Dogs with conventional thoracic CTs with orthogonal 2- or 3-view thoracic radiographs obtained within 9 days of the CT were included in the study. A control group was formed by selecting dogs that had undergone thoracic CT and radiographs within 9 days of one another, but in which the imaging reports of both studies failed to identify thoracic LN enlargement. This group was included to ensure adequate numbers of animals with normal LNs were intermixed with the dogs with enlarged LNs, with the intention of limiting observer bias. The hypothesis of this study was that intrathoracic LNs (sternal, cranial mediastinal and tracheobronchial) cannot be consistently identified radiographically, even when enlarged and assessed by experienced and trained observers.
What are the main study results?
Interobserver agreement on radiographs was almost perfect. Correlations between radiographic grades and CT volumes were weak or nonsignifican. No CT-derived volume threshold yielded a unanimous radiographic classification of enlargement across observers. Radiographs frequently failed to detect enlarged nodes and occasionally overcalled normal-sized nodes. These findings indicate poor alignment between radiographic grading and CT-measured volume for intrathoracic lymphadenomegaly, despite high interobserver agreement.
Were there any unexpected results or challenges during your research?
I was pleased to see that the 3 radiologists mostly agreed with one another meaning that it wasn't just me who is bad at identifying enlarged thoracic lymph nodes on radiographs! But it was surprising exactly how poor radiographs are for identifying enlarged intrathoracic lymph nodes.
Takeaways from this study
When accurate intrathoracic LN assessment is expected to influence clinical decision-making, CT should be considered.
What future directions would you like to explore based on this study?
It would be interesting to see if certain diseases result in substantial enough intrathoracic lymph node enlargement to be radiographically detectable. In particular, I wonder if lymphoma might cause intrathoracic lymph nodes to become so big that they are more likely to be detected on a radiograph.
