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What is your diagnosis?

History

A 3.5-year-old, male, intact budgerigar (Melopsittacus undulatus) presented with an acute history of unilateral feather loss around the left eye. The owner also reported blepharospasm and decreased activity level, with the bird spending more time at the bottom of the cage. The bird was housed with a female and was fed a mixture of seeds and pellets with occasional vegetables. The bird had a prior history (1.5 years earlier) of feather mites that responded to ivermectin treatment. On physical examination, the bird weighed 36 g, and feather loss and blepharospasm of the left eye were observed. The bird was bright, alert, and responsive, but there was slight, intermittent tail bobbing without open-mouth breathing, which the owner had not noticed at home. An ophthalmic examination, consisting of indirect ophthalmic exam and fluorescein stain, did not reveal any abnormalities. Based on the clinical signs and findings of the physical examination, the owner elected for conservative, empirical therapy with triple-antibiotic ophthalmic solution (OS; 1 drop OS q8h; neomycin and polymyxin B sulfates and gramicidin ophthalmic solution). Because of the change in behavior and tail bobbing, doxycycline (60 mg/kg IM q5d; Vibravenos, Pfizer, London, UK) was administered as empirical therapy for a possible respiratory infection.

The bird was reevaluated 4 days later, and results of the physical examination revealed conjunctivitis of the left eye in addition to the prior abnormalities. During the second visit, the female cage mate was observed attacking the bird on the left eye. The owner also reported the female had been more aggressive toward him. Flurbiprofen (1 drop OS q8h; Ocufen, Bausch and Lomb, Tampa, FL, USA) was added to the treatment regimen. The ophthalmic triple antibiotic was continued, and a second injection of doxycycline was administered. The owner was advised to house the male separately from the female to determine whether the presentation could be traumatic in origin.

The bird was reevaluated again 4 days later. On the third evaluation, the owner reported some improvement in the bird's attitude, but clinical signs remained unchanged. The ophthalmic treatment was continued as previously recommended, and a third injection of doxycycline was administered. A fourth evaluation was performed 10 days later. At that time, the bird had exophthalmos of the left eye (Fig 1). In addition, respiratory effort was increased, with inspiratory stertor and fluid bubbles observed on the nares. Because of the lack of response to therapy and the worsening ocular and respiratory signs, a grave prognosis was provided and euthanasia recommended. The owner elected to observe the bird for a period of time before euthanasia. Meloxicam (0.5 mg/kg PO q 12h; Metacam, Boehringer Ingelheim Vetmedica Inc, St Joseph, MO, USA) was prescribed on discharge. The bird was euthanatized 4 days later.

[FIGURE 1 OMITTED]

Diagnosis

The differential diagnoses for exophthalmos include a retrorobital mass, such as an abscess, granuloma, or neoplasia. Gross necropsy revealed the left eye protruding approximately 3 mm from the orbit as compared with 0.5 mm for the right eye. A 1-cm yellow, irregular area of the frontal bone, extending from 1 mm dorsomedial to midline with a trabecular pattern, was identified. A 2-mm pale pink to white, proliferative, somewhat lobular tissue mass was present behind the left eye and covered the floor of the orbit. On histopathologic examination, the retrobulbar mass was diagnosed as lymphosarcoma. In addition, bronchopneumonia with an intravascular neoplastic embolus was observed in the lungs. There was also evidence of a subacute lymphoplasmacytic ventriculitis.

Comments

Exophthalmos is a common avian presentation, whereas buphthalmos is rarely reported. Differential diagnoses for exophthalmos include retrobulbar neoplasia, pituitary adenoma or hyperplasia, Harderian gland adenoma, (1) and nonneoplastic masses (eg, abscesses). Buphthalmos, commonly diagnosed in canine species with glaucoma, is the enlargement of the fibrous coats of the eye and is caused by increased ocular pressure. (2)

Differential diagnoses for dyspnea in a bird are lower respiratory disease, infectious (bacterial, fungal) or noninfectious (neoplasia) in origin, or a space-occupying mass or fluid in the coelomic cavity. Pain and discomfort should also be considered.

Lymphosarcoma is the most common lymphoid neoplasia reported in psittacine and passerine birds, (3) and there are numerous reports of variations of this disease, including some affecting the ocular or periocular tissues. (4) However, lymphosarcoma is more commonly multicentric, affecting multiple tissues at once. (5) In this case, lymphosarcoma was diagnosed in a single location, the retrobulbar space. The presence of bronchopneumonia with an intravascular neoplastic embolus in the lungs is of interest. This finding could explain the respiratory signs in the bird, but there was no additional evidence to suggest whether the neoplastic embolus was an incidental finding or, perhaps, the initial stages of multicentric spread.

There are several reports of retrobulbar tumors in avian species, most of them presenting with exophthalmos, including teratomas in a lesser kestrel (Falco naumanni) (6) and a great blue heron (Ardea herodias), (7) rhabdomyosarcoma in a budgerigar, (8) and adenoma in an African grey parrot (Psittacus erithacus). (9) There is also a report of a metastatic hepatocellular carcinoma in the retrobulbar space in an Amazon parrot (Amazona species) that presented with chronic buphthalmos. (10) As mentioned previously, buphthalmos is rarely diagnosed in avian species. The Amazon parrot was diagnosed with a metastatic tumor that involved a retrobulbar mass. (10) The glaucomatous condition of the Amazon parrot was theorized to be caused by the large size of the ocular metastatic lesion and subsequent compression of the adjacent tissues, thereby strangulating the venous drainage from the eye. (10)

The lack of response to therapy and the progressive clinical signs in this case were suggestive of a neoplastic process. Radiographs and advanced diagnostic imaging modalities, such as computed tomography scan or magnetic resonance imaging could have been used to assess the mass and determine the extent of the disease. An enucleation could have been performed, followed by histopathologic evaluation of the eye and retrobulbar tissue, to obtain a definitive diagnosis. However, the size of the bird and risks associated with that procedure would have been high, and the owner was not inclined to pursue that route. Empirical palliative radiation therapy could also have been an option, but the prognosis for such treatment would have been guarded. The prognosis for this animal was grave, and although additional diagnostic tests may have provided more information about the disease process, the treatment choices were limited, and the outcome would likely have been the same.

This case was submitted by Javier G. Nevarez DVM, PhD, Doo-Youn Cho, DVM, MVSe, MS, PhD, and Thomas N. Tully Jr, DVM, MS, Dipl ABVP (Avian), from the Louisiana State University School of Veterinary Medicine, Department of Veterinary Clinical Sciences (Nevarez, Tully), and Department of Pathobiological Sciences (Cho), Skip Bertman Dr, Baton Rouge, LA 70803, USA.

Please evaluate the history, findings on the physical examination, and Figure 1. Formulate a list of differential diagnoses before continuing.

References

(1.) Lightfoot TL. Overview of tumors: Section I. Clinical avian neoplasia and oncology. In: Harrison GJ, Lightfoot TL, eds. Clinical Avian Medicine. Palm Beach, FL: Spix Publishing Inc; 2006: 560-565.

(2.) Townsend WM, Bedford PGC, Jones RG. Abnormal appearance. In: Peiffer R, Petersen-Jones S, eds. Small Animal Ophthalmology: A Problem Oriented Approach. 4th ed. London, UK: Elsevier; 2009:67-115.

(3.) Coleman CW. Lymphoid neoplasia in pet birds: a review. J Avian Med Surg. 1995;9(1):3-7.

(4.) Schnellbacher R, Wilson S. What is your diagnosis? Lymphoma. J Avian Med Surg. 2010;24(3):241-244.

(5.) Latimer KS. Oncology. In: Ritchie BW, Harrison GJ, Harrison LR, eds. Avian Medicine: Principles and Application. Lake Worth, FL: Wingers; 1994: 640-672.

(6.) Lopez RM, Murcia DB. First description of malignant retrobulbar and intracranial teratoma in a lesser kestrel (Falco naumanni). Avian Pathol. 2008;37(4):413-414.

(7.) Schelling SH. Retrobulbar teratoma in a great blue heron (Ardea herodias). J Vet Diagn Invest. 1994; 6(4):514-516.

(8.) Gulbahar MY, Ozak A, Guvenc T, Yarim M. Retrobulbar rhabdomyosarcoma in a budgerigar (Melopsittacus undulatus). Avian Pathol. 2005; 34(6):486-488.

(9.) Simova-Curd S, Richter M, Hauser B, Hatt JM. Surgical removal of a retrobulbar adenoma in an African grey parrot (Psittacus erithacus). J Avian Med Surg. 2009;23(1):24-28.

(10.) Freeman KP, Hahn KA, Jones MP, et al. Unusual presentation of an Amazon parrot (Amazona species) with hepatocellular carcinoma. Avian Pathol. 1999;28(2):203-206.
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Author:Nevarez, Javier G.; Cho, Doo-Youn; Tully, Thomas N., Jr.
Publication:Journal of Avian Medicine and Surgery
Article Type:Report
Geographic Code:1USA
Date:Sep 1, 2011
Words:1385
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