Avian radiography and disease (Proceedings)

Skeletal

     a. Metabolic bone disease: Inadequate calcium and Vitamin D3 intake may present as generalized osteopenia and/or folding fractures. This is most often seen in young birds, and in females with high egg production. Some species such as African Gray parrots have higher requirements for D3 and calcium and are therefore more susceptible to MBD.1

     b. Fractures

          1. Long bone fractures are common and readily identifiable on radiographs. The most common long bone fracture of companion psittacines is the tibiotarsal bone. In raptors, coracoid fractures are common and can be difficult to identify.

          2. Skull fractures can be difficult to identify. Fractures of the jugal arch, pterygoid bone and quadrate bone may be identifiable radiographically. Fractures of the cranium can seldom be identified unless they are displaced, and even then multiple views may be needed.

     c. Polyostotic hyperostosis is found to varying degrees in many species when the female is ovulatory. The calcium storage in bone changes the pneumatic appearance to a solid mineral dense appearing medullary canal. The long bones of the legs are most often affected, and the long bones of the thoracic limbs are also involved in more pronounced cases. In females where the calcium/Vitamin D3 is insufficient, a moth-eaten appearance to these bones often occurs.

     d. Arthritis is common in older birds as a degenerative process, and septic arthritis may also occur. The amount of bony proliferation with degenerative joint disease in birds is less obvious radiographically than in mammals. Septic arthritis in birds often presents radiographically as an enlarged joint space and requires arthrocentesis to confirm.

     e. Osteosarcoma is not as often reported in birds as it is in mammals. It does not metastasize readily, though it is locally aggressive. Radiographically, most cases are predominately lytic in appearance.

Respiratory disease

     a. Air sacculitis may present radiographically as thickeneda ir sac walls or granulomas within the air sacs.

     b. Ruptured air sacs are obvious on physical examination, and this finding is reflected by the radio-opaque space occupying subcutaneous areas on radiographs.

     c. Syringeal foreign bodies are difficult to detect radiographically. The syrinx is a "busy" area and superimposition of surrounding structures occurs. The syrinx generally lies between the second and third thoracic vertebrae.

     d. Pneumonia can be detected by a patchiness in the lungs and loss of the typical honeycomb pattern. Air bronchograms cannot occur due to the presence of air capillaries rather than aveloi.

Cardiovascular

     a. Microcardia is usually associated with hypovolemia.

     b. Cardiac enlargement due to chamber enlargement can be determined by cardiac/thoracic width ratio measurement on the V/D view. Echocardiology is generally required to confirm functional cardiac disease.

     c. Pericardial effusion can be suspected on radiographs but confirmation usually requires ultrasound

     d. Athlerosclerosis can be suspected radiographically when the greater vessels are enlarged (increased diameter) and when there is increased radio- opacity. Unfortunately, without angiography, atherosclerosis cannot be confirmed antemortem.

Gastrointestinal

     a. Crop foreign bodies are common in young birds. While still hand feeding, aggressive bobbing may dislodge tubing from the syringe. This tubing may become lodged in the crop, or migrate farther down the GI tract. Birds may also ingest a variety of foreign materials. Size, length or texture may prevent the material from moving out of the crop.

     b. Esophageal strictures may occur due to trauma, chemical or heat burns, infections or neoplasia

     c. Proventricular Dilatation Disease will often affect the neural ganglia of the GI tract, causing abnormal dilation and stasis of the proventriculus.

     d. Mycobacterial infections in psittacines are often concentrated in the GI tract, and significant thickening of the GI may occur.

     e. Ventricular foreign bodies result when foreign material is ingested and is able to pass through the crop. The outflow of the ventriculus is of a diameter that does not generally allow particles to pass that are too large to continue to exit the GI. Therefore, GI obstruction of the intestine from foreign boy ingestion is uncommon

     f. Intestines – note than in a normal bird, no gas should be detectable in the small or large intestines.

Hepatomegaly

     a. Hepatic lipidosis is commonly found in two situations.

          1. Young birds, particularly cockatoos that are fed a formula excessively high in calories.

          2. Adult birds with chronic malnutrition and obesity, with Amazon parrots overrepresented.

     b. Hepatomegaly is also associated with several systemic diseases, including:

          1. Chlamydiosis

          2. Herpes virus

          3. Polyomavirus

          4. Chronic active hepatitis (early)

          5. Spleen of psittacines is spherical and is a hemopoetic organ only (no blood storage). Therefore, enlargement generally indicates infection.

Urinary

     a. Nephromegaly may occur due to tumor, infection, granuloma, cyst or post-renal obstruction. The kidneys are normally surrounded by air, and with nephromegaly, the surrounding air is reduced or absent. With no central medullary area to the kidney divisions, contrast media does not collect. Therefore excretory urograms are less distinct, but still can be useful. Injection of contrast media into the medial metatarsal vein produces a more pronounced opacification than does injection of the contrast into a vein in the cranial part of the body.

     b. Increased renal density may be radiographically evident with renal gout, renal calcification or dehydration.

Reproductive

     a. Testes of males enlarge to some degree with seasonal hormonal activity. The degree of this enlargement is somewhat species-specific. Testicular tumors occur that may present as increased mass-effect in the area of the cranial division of the kidney. If a Sertoli cell tumor is present, it may produce estrogen and result in cere color change to brown in budgerigars and possible polyostotic hyperostosis in other avian species.

     b. Ovarian disease is very common in captive psittacines. If the ovary is enlarged it will cause cranioventral displacement of the ventriculus. Chronic hyperestrogenism often leads to ovarian disease, which may include cystic ovaries, soft-shelled retained eggs, egg yolk peritonitis, ovarian neoplasia and abdominal herniation. Ultrasound may be helpful in differentiating these conditions, but the presence of air sacs often limits its usefulness.