What are common CT findings in dogs and cats with grass seed foreign bodies?

5 July 2024

Summer is here and chances are you’ll be seeing more dogs and cats with grass seed injuries.

Grass seed migration is a well-documented issue in dogs and cats and retrieval of grass seeds can be difficult due to unpredictable migration routes, being deeply embedded in dense fibrous tissue, and difficulty in identifying small fragments. Grass seeds may be visible on computed tomography (CT) images, although this is not always reliable.

A study published in the Journal of Small Animal Practice by researchers at the RVC explored CT findings associated with grass seed migration in dogs and cats.

For the study, records of cases that had a CT scan and subsequent retrieval of a grass seed during the same period of hospitalisation between August 2004 and October 2013 were retrospectively reviewed, resulting in cases of 44 dogs and 10 cats being included. CT scans were either performed using a single slice helical CT scanner (prior to August 2009) or a 16-slice CT helical scanner (after August 2009), and CT images reviewed by a board-certified radiologist.

The majority of animals (80%) were presented between July and December, likely a result of animals predominantly acquiring grass seeds during the summer and developing signs within the following few weeks or months. Affected dogs were significantly younger (median age 3 years) than cats (median age 8 years) and hunting dogs (springer spaniels and retrievers) were well-represented.

The most frequent clinical signs were soft tissue swelling (30% of cases), coughing (28%), sneezing (28%) and discharge from an orifice or sinus (26%), while pyrexia (20%) and neutrophilia (22%) were reported less frequently. Median duration of clinical signs was 4 weeks (ranging from 2 days to 2 years).

In dogs, grass seeds were retrieved from a range of locations – the thorax (41% of cases), other sites in the head and neck (27%), nasal cavity (21%), abdomen (10%), ear (9%) and pelvic limb (2%). In cats, grass seeds were found mostly in the nasal cavity (80%).

The grass seed was visible in CT images in 19% of cases and in each one, located in an airway and visible only when using a wide CT display window suitable for lung. Secondary lesions were visible in CT images in 96% of cases, including collection of exudate (37%), abscess (24%), enlarged lymph nodes (22%) and pulmonary consolidation (20%). CT images appeared normal in 4% of animals.

The appearance of grass seeds on CT images varied from delicate linear structures representing seed fragments, elongated fusiform structures representing individual intact florets, to an oblong cluster of soft tissue and gas foci representing part of the spike or spikelet.

CT findings varied with the grass seed’s anatomical location. In the nasal cavity, CT images had signs of exudate (88% of cases), localised loss of turbinate structure (24%), a linear intraluminal inclusion compatible with the retrieved grass seed (18%) and appeared normal in one case. In the ears, CT images had thickened lining of the external ear canal (50% of cases), and a linear intraluminal inclusion compatible with retrieved grass seed, signs of exudate in the tympanic cavity, para-aural soft tissue swelling, and enlarged ipsilateral medial retropharyngeal lymph node, each in one case. CT images of other sites in the head and neck had signs of cavitary lesions compatible with abscesses (75% of cases), soft tissue swelling (58%), enlarged regional lymph nodes (58%) and appeared normal in one case. In the thorax, CT images had signs of focal or multifocal pulmonary consolidation (58% of cases), a linear intraluminal inclusion compatible with retrieved grass seed (32%), pleural fluid (21%), pleural gas (16%), thickening of soft tissues in the thoracic wall (16%), pulmonary cavitary mass (11%), enlarged thoracic lymph nodes (11%) and overinflation of the affected lung lobe in one case.

Fourteen surgically confirmed abscesses were identified in CT images, all of which contained a grass seed or fragment, however, no grass seeds were identified in CT images in any abscess.

Take home message

This study confirmed that grass seeds in the respiratory tract are often visible in CT images (visible in 19% of cases in this study), but CT is not always reliable. CT appears to be more useful for localising secondary lesions, rather than for a definite diagnosis.

Read the full study: https://onlinelibrary.wiley.com/doi/abs/10.1111/jsap.12278


Vansteenkiste DP, Lee KCL & Lamb CR (2014) Computed tomographic findings in 44 dogs and 10 cats with grass seed foreign bodies. Journal of Small Animal Practice. 55(11), 579-584.