Case Study

CT – Retrobulbar abscess with circumferential septic cellulitis in an intact F canine hunting dog

This intact female dog presented with a 4-day history of progressive 3rd eyelid prolapse and exophthalmus. A purulent draining tract was noted/lanced in the mouth (also left side), but severity has worsened significantly instead of improving since that was drained by rDVM. Patient is a hunting dog.

CBC/Chem wnl

DX

The CT findings are compatible with a retrobulbar abscess with circumferential septic cellulitis after incomplete drainage

Image Interpretation

CT of the head, plain and post contrast – There is an ill defined, hypoattenuating, heterogeneous mass lesion measuring 2 x 2.5
x 2 cm within ventral and medial aspect of the left retrobulbar space. The mass lesion
causes a marked mass effect on the left bulbus with significant compression and dorsal
and temporal deviation. There is retrobulbar fat stranding. The soft tissue swelling
extends into the left retromolar space. Multiple gas bubbles are seen within the soft
tissue medial and caudal to the main component of the mass lesion.
After contrast administration ill-defined thick-walled peripheral rim enhancement is
noted extending to the neighbouring soft tissue.
A foreign body is not seen.
The left sided medial retropharyngeal and submandibular lymph nodes reveal moderate
generalized enlargement. The short to long axis ratio and contrast enhancement pattern
of the lymph nodes is preserved.
Mild localized mucosal soft tissue swelling was noted next to the orbits on the left side
within the nasal cavity.

Outcome

The drainage tract is medial and caudal to the main component of the abscess.
Note the even though a foreign body is not seen a foreign material related history of
the mass lesion is very likely. Macerated organic material is typically undetectable
with CT after being located within the soft tissue for a long time. So the presence of
small foreign bodies can’t be ruled out based on CT in general.
The lymph node changes are compatible with reactive lymphadenitis. Moreover there
was mild secondary localized rhinitis, which was non-destructive on the left side.
The previous surgical measures drained the abscess cavity insufficiently. Repetition of
the surgical drainage is mandatory. The best option for nontraumatic surgical approach
still appears to be via the retromolar space. Other than the mass effect no structural
changes of the globe were noted. Monitoring of intraocular pressure is advised.