The etiology and clinical significance of increased radiographic opacity along the dorsal margin of the tracheal lumen has long been debated. Most often, this opacity is attributed to redundancy of the dorsal tracheal membrane (DTM), a condition that occurs with tracheal collapse. We hypothesized that the underlying etiology of this radiographic opacity differs between small breed dogs with tracheal collapse and small or large breed dogs without tracheal collapse. The purpose of this prospective, cross-sectional study was to compare the radiographic appearance of an increased opacity within the trachea to tracheoscopy findings in a group of small and large breed dogs. A total of 17 small breed dogs and 16 large breed dogs were included. Of these, only one did not have a radiographically visible DTM. Small breed dogs were divided into groups with tracheal collapse (n = 8) and those without (n = 9) based on tracheoscopy. Tracheal collapse was absent in larger breed dogs, however both large and small breed dogs demonstrated inward invagination of the DTM. In dogs with tracheal collapse, the DTM occupied a larger percentage of the tracheal luminal height on radiographs and a larger percentage of tracheal circumference on tracheoscopy vs. dogs with an invaginated DTM on tracheoscopy and dogs with no collapse and no invagination of the DTM. Findings supported the hypothesis that increased radiographic opacity along the dorsal margin of the trachea arises from different etiologies in dogs with and without tracheal collapse.

Chondro-osseous respiratory epithelial adenomatoid hamartomas (COREAHs) are rare tumors in the nasal cavity of people, which have not been described in other species. COREAHs in people are minimally invasive and rarely recur following excision. Histologically, these tumors are composed of disorganized, mature, nasal turbinate tissue that is organized into polypoid growths. These growths are lined by respiratory epithelium, contain glandular elements, and are organized around central cores of chondro-osseous matrix. This report describes 3 cases of dogs with nasal tumors that have histomorphology similar to that of COREAH in people. The tumors were all identified within the nasal cavity and were associated with regional bony lysis of the turbinates and surrounding skull bones, a feature that has not been reported in COREAH in people. There was no evidence of metastasis or extension beyond the nasal cavity in any of the 3 cases.