Radiographic Characteristics of Feline Nasopharyngeal Stenosis

Abstract

Feline nasopharyngeal stenosis (NPS), characterized by narrowing of the nasopharyngeal passage, results in chronic stertor and increased inspiratory effort. While rhinoscopy is the definitive diagnostic modality for NPS, the utility of nasopharyngeal radiography in diagnosis remains under-documented. The purpose of this study is to evaluate the diagnostic accuracy and describe the characteristic radiographic findings in cats with NPS by comparing radiographic findings in cats with stertor but without stenosis. This is a multicenter, retrospective, cross-sectional study. Fifty-two cats with stertor who underwent both rhinoscopy and lateral nasopharyngeal radiography were included. They were divided into two groups: those with NPS (n = 21) and those with stertor without stenosis (ND group, n = 31). Radiographs were reviewed by two board-certified radiologists to determine the presence, location, and morphology (broad or membranous) of NPS, as well as the morphology of the soft palate and the presence of oropharyngeal gas. Radiographic evaluation demonstrated a high diagnostic accuracy for NPS with a sensitivity of 100%, specificity of 83.9%, and overall accuracy of 90.4%. The radiographic morphology of the NPS was broad in 18 cats and membranous in 3 cats. A "bent" soft palate was observed only in the NPS group (19%, n = 4). The presence of oropharyngeal gas was similar in both groups (57.1 vs. 58.1%). However, because radiographic diagnoses were made by consensus between two radiologists, the reported accuracy may be overestimated. Given its high sensitivity, nasopharyngeal radiography serves as an effective initial screening tool for NPS, likely streamlining the diagnostic pathway in cats with stertor.

Keywords: respiratory diseases; soft palate; stertor; upper airway obstruction.

FIGURE 1

Lateral radiograph of the nasopharynx in a cat without evidence of NPS. (A) Unannotated radiograph. (B) Annotated radiograph with the nasopharynx shaded in gray and dotted lines demarcating the rostral, middle, and caudal portions of the nasopharynx. The middle portion of the nasopharynx is defined by the location of the temporomandibular joint.

FIGURE 2

Lateral radiographs of the nasopharynx in two cats with NPS. (A) Broad stenosis involving the rostral and middle portions of the nasopharynx (categorized as middle due to inclusion at the level of the temporomandibular joint) with a “bent” soft palate morphology (dotted line and white arrowhead). (B) Membranous stenosis (white arrowhead) in the caudal nasopharynx with normal soft palate morphology.

FIGURE 3

Lateral radiographs of the nasopharynx in cats without NPS. (A) Absence of gas within the oropharynx. (B) Partial presence of gas within the oropharynx. (C) Continuous presence of gas within the oropharynx.

FIGURE 4

Lateral radiograph of the nasopharynx in a cat without NPS. However, a false‐positive diagnosis of NPS was made radiographically. Black arrows indicate the region of the pterygoid processes of the basisphenoid bone.