When Corneal Edema Is More Than Endothelial Dystrophy: Recognising Canine Endotheliitis Early

Bilateral corneal edema in dogs is often initially approached as endothelial dystrophy or secondary uveitic edema, particularly in younger patients presenting with discomfort and diffuse corneal haze. However, persistent inferior corneal edema, recurrent flare-ups after tapering medication, and the presence of keratic precipitates (KPs) should prompt clinicians to consider canine endotheliitis as an important differential^1,2. 

Canine endotheliitis remains an under-recognised inflammatory endothelial disorder, but recent ophthalmic imaging findings are helping clinicians identify characteristic patterns that distinguish it from primary degenerative endothelial disease^1,2. 

The Clinical Pattern Veterinarians Should Not Miss 

One of the most consistent observations in affected dogs is bilateral edema that appears more severe in the inferior cornea. Unlike transient edema associated with acute anterior uveitis, the edema in endotheliitis often persists despite improvement in anterior chamber inflammation^1,2. 

Affected dogs may present with: 

• Blepharospasm  

• Conjunctival hyperemia  

• Episcleral congestion  

• Mild aqueous flare  

• Diffuse or inferior corneal edema  

• Multifocal pinpoint KPs^1,2 

In one young Chihuahua mix, topical corticosteroid therapy initially improved corneal clarity and discomfort, but edema rapidly relapsed within a week of discontinuing anti-inflammatory treatment^1,2. Similar recurrence patterns were observed in other canine patients, suggesting that endothelial inflammation may persist subclinically even after apparent clinical improvement. 

Another clinically relevant observation was the progressive increase in corneal thickness during active episodes. In one dog, inferior corneal thickness increased by more than 50% during relapse, accompanied by prominent inflammatory deposits visible clinically and on advanced imaging^1,2. 

Why Advanced Imaging Changes the Diagnosis 

Slit-lamp examination remains essential, but multimodal imaging is increasingly valuable in confirming endothelial involvement. Fourier-domain optical coherence tomography (FD-OCT) and in vivo confocal microscopy (IVCM) revealed several characteristic abnormalities in affected dogs^1,2. 

FD-OCT commonly identified: 

• Thickening of the Descemet’s membrane-endothelial complex  

• Inferiorly distributed hyperreflective deposits  

• Marked corneal edema^1,2  

Meanwhile, IVCM demonstrated: 

• Endothelial pleomorphism  

• Polymegathism  

• Reduced endothelial cell density (ECD)  

• Hyperreflective inflammatory deposits compatible with KPs  

• Hyporeflective pseudoguttata^1,2 

These findings parallel endothelial inflammatory changes previously described in human endotheliitis and equine immune-mediated keratitis. Pseudoguttata, which represent transient endothelial edema during inflammatory episodes, have also been associated with endothelial stress and dysfunction¹. 

Endothelial Damage May Persist Long After Inflammation Improves 

A particularly important clinical concern is the marked reduction in endothelial cell density observed in affected dogs. Normal canine ECD typically ranges from 2300–2500 cells/mm², yet several affected patients demonstrated dramatically lower counts^1,2. 

One dog showed endothelial densities below 900 cells/mm² early in the disease course, with further decline during recurrent inflammatory episodes. These findings suggest that corneal edema in canine endotheliitis is not solely inflammatory but may eventually progress toward endothelial decompensation^1,2. 

Some dogs also demonstrated elongated hyperreflective endothelial nuclei on IVCM, a feature associated with endothelial trauma and disease in human ophthalmology¹. 

Practical Implications for Veterinary Practice 

For clinicians, the biggest challenge is avoiding misclassification of these patients as uncomplicated endothelial dystrophy or isolated anterior uveitis. Recurrent edema, inferior corneal involvement, and persistent KPs should raise suspicion for ongoing endothelial inflammation. 

Careful assessment of the Descemet’s membrane-endothelial complex using high-magnification slit-lamp biomicroscopy can be extremely valuable, while FD-OCT and IVCM may help confirm subtle inflammatory changes when diagnosis remains uncertain. 

Importantly, relapse after tapering therapy should not automatically be interpreted as treatment failure. In many dogs, it may instead reflect the chronic and recurrent nature of endothelial inflammation itself. 

Reference 

1. Mayes MA, Casanova MI, Park S, Steele K, Linton L, Kim S, Good KL, Moore BA, Newbold GM, Leonard BC, Li JY. Canine endotheliitis: Clinical characteristics, advanced imaging features, and treatment. Veterinary ophthalmology. 2022 May;25:185-92. https://pmc.ncbi.nlm.nih.gov/articles/PMC9243184/pdf/nihms-1765869.pdf 

2. Thomasy SM, Cortes DE, Hoehn AL, Calderon AC, Li JY, Murphy CJ. In vivo imaging of corneal endothelial dystrophy in Boston terriers: a spontaneous, canine model for Fuchs' endothelial corneal dystrophy. Investigative ophthalmology & visual science. 2016 Jul 1;57(9):OCT495-503. https://iovs.arvojournals.org/arvo/content_public/journal/iovs/935468/i1552-5783-57-9-oct495.pdf