Nephroblastomas, also known as embryonal nephromas, are the most commonly reported renal tumor in chickens, and frequently associated with the avian leukosis virus (ALV). Renal carcinomas, adenoma, cystadenoma, fibrosarcoma, lymphosarcoma, and other neoplasms can also occur.
The predominant clinical sign that points towards the possibility of renal tumor is unilateral or bilateral leg lameness or paralysis, with no history of trauma. The chicken may still be able to move their leg from front to back, but just can't stand on it. This clinical sign results from compression on the ischiadic nerve by the mass of the tumor.
The musculature in the affected leg(s) may atrophy from disuse, and the entire leg may become paretic. Affected birds may have trouble resting or sleeping due to discomfort. Their appetite, however, often remains relatively normal. Other less specific clinical signs which may occur are abdominal enlargement, apathy, weight loss, dyspnoea, and diarrhea, resulting from the intracoelomic pressure or organ displacement. Once clinical signs develop, most chickens can live an additional 3 to 6 months if they're provided proper palliative care.
- Radiographs: Are useful in assessing the size, location, and radiopacity of the kidneys. Two views are recommended---right or left lateral and ventrodorsal. Correct patient positioning is essential.
- Ultrasound: Can be useful if the patient has ascites, which compresses the air sacs, allowing the ultrasonographic imaging of the kidneys. Otherwise, the presence of the air sacs makes it difficult to view kidneys in birds using ultrasound imaging.
In mammals, nephrectomy is the treatment of choice for unilateral renal tumors. However, this is not the case in birds. Surgical removal of kidneys in birds is virtually impossible due to their location and intricate relationship with the surrounding blood vessels and nerves. There are also no effective medical management options for renal tumors in birds. Palliative care through the use of analgesics for pain management (for nerve compression by the renal mass), corticosteroids, and special care for immobility may help make the remainder of their lives more comfortable. Ultimately, euthanasia must be considered once husbandry modifications and analgesia fail to ensure appropriate quality of life for the bird.