Ureterolithiasis in a Double Yellow-headed Amazon Parrot (Amazona ochrocephala)
American Association of Zoo Veterinarians Conference 1999
Patricia M. Dennis, MSL, DVM; R. Avery Bennett, DVM, MS
Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA


Ureterolithiasis has not been reported in avian medicine literature. Diagnosis of this disease in other species by the use of palpation, radiography, or ultrasonography has been reported.2-4 The purpose of this case report is to discuss the diagnosis and surgical treatment of ureterolithiasis in a double yellow-headed Amazon parrot (Amazona ochrocephala) that presented to the Veterinary Medical Teaching Hospital (VMTH), University of Florida.

The bird presented to the VMTH with a 3-yr history of straining to urinate and defecate. The bird had a recent onset of depression and inappetence. Radiographs made by the referring veterinarian 3 yr prior to presentation showed mineral-dense opacities in the dorsal caudal coelomic cavity. Radiographs made 1 yr prior to presentation showed enlargement of the kidneys and more caudal location of the mineralized opacities.

On physical examination the bird was quiet and alert. Skin was dry, flaky and feathers were dull. The cloaca was surrounded by pasted urates. The area around the cloaca was featherless and inflamed. No other abnormalities were noted on physical examination. Complete blood count showed a leukocytosis (WBC 20,000 cells/μl) with a heterophilia (15,600 cells/μl) and a lymphopenia (2,800 cells/μl). The biochemical profile showed an elevation in aspartate transaminase (AST 706 u/L).

A left lateral celiotomy was performed to remove the mineralized material. A prominent, white, fluid-filled tubular structure in the region of the left kidney and ureter was identified. The structure, based on biopsy and histologic examination, was the left ureter. The ureter contained a firm 2 cmx1 cmx1.5 cm yellowish-white mineralized mass which was removed. The ureter was explored but no other masses were located. Following surgery, a ventrodorsal radiograph was made to determine whether all masses had been removed. One calculus could be seen in the caudodorsal lateral coelomic cavity. Four days following the initial surgery, the remaining ureterolith was removed by a cloacotomy and ventral midline celiotomy.

At a follow-up examination 10 days after the second surgery, an excretory urogram was made. There was evidence of normal peristaltic movement of the right ureter on several radiographic views. On the 10-min post-injection radiographs, the left ureter was homogenously opacified and measured approximately three times the width of the right ureter.

Surgical removal of the ureteroliths was complicated by the anatomy of the bird. Removal of the ureteroliths was not possible through a single surgical approach. Use of other techniques to remove ureteroliths, such as extracorporeal shock wave lithotripsy,1 is not possible due to the presence of air sacs.

The underlying cause of ureteroliths is unknown, though vitamin A deficiency has been suggested as a possible etiology.5 The ureter, being an epithelial lined structure, is a possible site for the development of squamous metaplasia in response to vitamin A deficiency. In this case, no epithelium was seen on histologic examination of the ureteral tissue, so the presence of squamous metaplasia could not be determined. Other possible causes of the ureteroliths include chronic dehydration or bacterial infection.

Literature Cited

1.  Block, G., L.G. Adams, W.R. Widmer, and J.E. Lingeman. 1996. Use of extracorporeal shock wave lithotripsy for treatment of nephrolithiasis and ureterolithiasis in five dogs. J Am Vet Med Assoc. 208:531–536.

2.  Brown, N.O., J.L. Parks, and R.W. Green. 1977. Canine urolithiasis: retrospective analysis of 438 cases. J Am Vet Med Assoc. 170:414–418.

3.  Ehnen, S.J., T.J. Divers, D. Gillette, and V.B. Reef. 1990. Obstructive nephrolithiasis and ureterolithiasis associated with chronic renal failure in horses: eight cases (1981–1987). J Am Vet Med Assoc. 197:249–253.

4.  Gaschen, L., C. Ketz, J. Lang, U. Weber, L. Bacciarini, and I. Kohler. 1998. Ultrasonographic detection of adrenal gland tumor and ureterolithiasis in a guinea pig. Vet Radiol Ultrasound. 39:43–46.

5.  Orosz, S. 1997. Urogenital disorders: anatomy of the urogenital system. In: Avian Medicine and Surgery. WB Saunders, Co., Philadelphia, Pennsylvania, Pp 616–617.


Speaker Information
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Patricia M. Dennis, MSL, DVM
Small Animal Clinical Sciences
College of Veterinary Medicine
University of Florida
Gainesville, FL, USA

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