Research roundup: University researchers ID lymph nodes previously undocumented in dogs

Researchers have discovered what they believe to be the presence of two lymph nodes in the pelvic region of certain dogs that were previously undocumented in the animal. The findings have the potential to improve diagnostic and treatment plans for the most popular pet in the world. 

The lymph nodes are sciatic and gluteal. Sciatic lymph nodes have been documented in pigs, cats, horses, and ruminants such as cattle; and gluteal lymph nodes are found in pigs and sometimes the ox. However, the glands have not been documented in dogs, and the Nomina Anotomica Veterinaria, published by the World Academy of Veterinary Anatomists, specifically says sciatic lymph nodes are absent in dogs. 

The University of Minnesota researchers, in the Department of Veterinary Clinical Sciences, found the lymph nodes via a retrospective study in which they assessed images of all dogs taken to the University’s Veterinary Medical Center that underwent a CT angiography of the abdomen or abdomen and pelvis between Sept. 1, 2020, and Dec. 31, 2020. A CT angiography is a CT scan combined with a dye injection to help visualize blood vessels and tissues in the body. 

The clinical scientists, radiologist Christopher Ober, DVM, PhD, DACVR, and then fourth-year vet student Riley Claude, currently a DVM at the Angell Animal Medical Center in Boston, found sciatic lymph nodes in 19 of 121 dogs and gluteal nodes in one of 121 dogs. Eight of the dogs with sciatic nodes represented four breeds: boxer, German shepherd, shih tzu, and the wirehaired fox terrier. A Tamaskan had visible sciatic and gluteal nodes. Males, intact and neutered, and spayed females were represented. The median age was 12, and 17 of the 19 dogs were at least 8 years old. (The same lymph nodes are not present in all dogs.)  

 In any species, swollen or enlarged lymph nodes can indicate the spread of disease beyond its primary locus—so it’s important in diagnosis and in therapeutic planning to understand where lymph nodes are located. The findings could be of special value for diagnosis and treatment of canine patients with tumors in the abdomen or pelvis, specifically in a cancer like apocrine gland anal sac adenocarcinoma, where spread to distant lymph nodes could mean a poor prognosis.

Because it was a retrospective study, the researchers could not further test the lymph nodes to determine whether they were normal or abnormal. But future research, including post-mortem analysis, could help characterize those differences. The study was published recently in the journal Veterinary Radiology & Ultrasound.