First Canine Case of Renal Lymphangiectasia Unveiled Through Ultrasound

Imaging Diagnosis—Sonographic Features of Bilateral Renal Lymphangiectasia in an Azotemic Dog

Yu Wang, Wilfried Mai, Lisa Dourmashkin, Victoria Leopardi, Hayley Amerman

Background:
Renal lymphangiectasia is a rare and benign dilation of renal lymphatic vessels, previously reported only in human medicine. This case report represents the first sonographic description of renal lymphangiectasia in a dog. The aim was to document the clinical presentation, imaging features, and diagnostic considerations of this condition in a veterinary context, drawing comparisons to similar cases in human literature.

Methods:
A 9-year-old neutered male Labrador Retriever presented with azotemia and bilateral renomegaly. Diagnostic work-up included physical examination, blood and urine analysis, and abdominal ultrasonography. Sonographic evaluation utilized microconvex and linear transducers, with color and power Doppler modes applied to assess vascularization. A postmortem necropsy and histopathology, including CD-31 and PROX-1 immunohistochemical staining, were performed to confirm diagnosis.

Results:
Ultrasound revealed bilateral renomegaly with circumferential subcapsular anechoic fluid collections containing thin hyperechoic septations and no internal Doppler flow, consistent with lymphatic origin. Corticomedullary distinction was reduced, and the renal cortex appeared hyperechoic. Necropsy demonstrated coalescing subcapsular cystic spaces compressing the renal cortex. Histopathology confirmed these as dilated lymphatic vessels with occasional endothelial lining. CD-31 staining was present in vascular endothelia but not in cyst-lining cells. PROX-1 staining was inconclusive due to autolysis.

Limitations:
The diagnosis was complicated by advanced postmortem autolysis, which hindered immunohistochemical interpretation, particularly for lymphatic-specific PROX-1 staining. Absence of biopsy confirmation during life and reliance on a single case limit generalizability. Lack of advanced imaging (e.g., CT or MRI) also restricted comparative modality evaluation.

Conclusions:
This report identifies renal lymphangiectasia as a potential differential for bilateral renomegaly in dogs, with characteristic subcapsular septated anechoic sonographic findings. Awareness of this condition may prevent misdiagnosis with polycystic kidney disease, urinoma, or hydronephrosis. Further cases and improved histopathologic sampling are necessary to enhance recognition and understanding of this entity in veterinary patients.

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