Embryonic Nephroma   (Kidney)


I am writing this report to inform veterinarians and owners about this odd finding.  I received a call from one of our clients concerned about her 14 year old pregnant alpaca.  The female had begun to pass blood on the fecal pile.  The owner also noted this female had been bullied by other animals that morning.  No other abnormalities were noted.

I responded to the farm within 45 minutes and upon arrival the animal had expired.   External exam revealed blood from the vagina.  The owner requested a necropsy.   Exam of the animal was unremarkable except for the abdomen.
There was a lot a free blood in the abdominal cavity and a grossly enlarged right kidney.   The fetus was normal on appearance and development.  The right kidney (of the dam) appeared enlarged, necrotic, and friable.  Many blood filled
cavities were present on the kidney surface.  I removed the kidney and took a sample for histopathology.  The enlarged kidney weighed 5.9 pounds!  My cause of death for this alpaca was neoplasm rupture and acute blood loss.

Histopathology results confirmed embryonic nephroma.  Much of the mass was necrotic and apparently very friable, with a large blood supply.  While these tumors are present from birth, they are often asymptomatic and usually
only a problem when rupture occurs, as in this case.

The histopathologic appearance of this neoplasm varies considerably throughout.  In many areas, an epithelial component predominates.  These components form well differentiated to primitive tubules lined by cuboidal to polygonal cells.  They also form solid, branching cords, or loose, rounded cells with very little stroma.  Within tubular areas are sometimes
present epithelial cells forming glomerular-like structures, but lacking capillaries.   In other areas, sparsely cellular connective tissue is predominant.   Throughout the mass are necrotic and hemorrhagic areas.

This neoplasm is caused by abnormal development of the fetal kidney.  The animal lived a good life and gave birth to many crias.  The left kidney had developed normally so function was intact.  The animal was able to prosper
despite only having 1 functional kidney.  As mentioned, problems only occurred when the mass ruptured.  You can discuss preventative options with your veterinarian.   I hope this information sheds some light on a little
known anomaly.

Eric E. Chapman, DVM
(970) 565-7567

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