Effect of different injection rates and doses of contrast medium on the image quality of computed tomographic angiography in African grey parrots (Psittacus erithacus)

BACKGROUND

Atherosclerosis is a common cardiovascular disease in parrots but the antemortem diagnosis is challenging. In human medicine, computed tomography angiography (CTA) has been used widely for the diagnosis of atherosclerosis. By adjusting the injection rate and total dose of contrast medium, the image quality can be improved. To test the effects of different injection conditions on the image quality of major arteries, 10 African grey parrots (Psittacus erithacus) were used. Three injection rates (0.3, 0.4, 0.5 mL/s) and three doses (740, 370, 222 mg of iodine/bird) were tested while the other variables of the studies were fixed.

RESULT

A higher injection dose led to a significantly higher attenuation, image noise and diameter, with a lower signal-to-noise ratio and contrast-to-noise ratio of the six major arteries. The 370 mg of iodine/bird group showed significantly better subjective image quality. Furthermore, with increasing injection rates, the prevalence of heterogeneity decreased. However, we found an increased risk of injection failure for the 0.5 mL/s groups.

CONCLUSION

We recommend a combination of 370 mg of iodine/bird with 0.4 mL/s for clinical use to achieve better image quality for CTA.

A Spectral Computed Tomography Contrast Study: Demonstration of the Avian Cardiovascular Anatomy and Function

As part of the cardiovascular examination, all birds underwent clinical and echocardiographic examinations. Radiographs and blood samples were taken. Each bird was premedicated with midazolam and medetomidin and anesthetized with inhalation anesthesia using isoflurane. We performed computed tomographic angiography (CTA) after intravenous injection of 1 to 2 mL contrast agent per kg followed by a 1 mL saline solution flush. We were been able to identify the arteries that previous studies revealed to be most likely affected by atherosclerotic lesions: the aorta, both pulmonary arteries, and both brachiocephalic trunks. CTA was safe and is of potential diagnostic value in birds.

Heart Disease in Pet Birds - Diagnostic Options

Cardiovascular diseases are common in pet birds. Diagnosis is often made postmortem only. In any case, suspicious for cardiac disease, a full diagnostic work up should be applied. First indications are given by the anamnestic data. Relative predisposition to cardiovascular diseases is associated with the species, breed, age, gender, lifestyle, and diet. Clinical signs and examination can reveal further indications of cardiovascular diseases, but may be unspecific or even without any pathologic finding. Diagnostic imaging, at least radiography, and echocardiography are always recommended. Advanced imaging methods, especially angiocardiography, can be valuable but is also more invasive and expensive.

Mortality rate of birds following intravenous administration of iodinated contrast medium for computed tomography

OBJECTIVE

To identify potential risk factors for death following IV or intraosseous (IO) administration of contrast medium in birds undergoing CT scans.

ANIMALS

120 birds that underwent 134 contrast-enhanced CT scans.

PROCEDURES

Medical records of birds of any species that underwent a CT scan which included administration of nonionic iodinated contrast medium from June 2013 to February 2020 were included. Information on birds and use of contrast medium was extracted from the medical records as well as information on deaths following IV or IO administration of contrast medium.

RESULTS

6 birds died shortly following administration of contrast medium. Necropsies were performed in 3 birds (2 cockatiels and 1 macaw), and all had lesions associated with the respiratory tract. When body weight was used as a binary variable to compare odds of death between small birds (≤ 150 g [0.33 lb]) and large birds (> 150 g), small birds had a 97-fold increased odds (OR, 97.5; 95% CI, 9.8 to 966.0) of dying following contrast medium administration. Following 131 CT scans with contrast medium administration (3 scans were excluded because of perivascular or subcutaneous leakage of contract medium), small birds had a mortality rate of 45.4% (5/11), compared with a mortality rate of 0.8% (1/120) for large (> 150 g) birds. Other variables (ie, sex, age, anesthesia or sedation, sedation protocol, and type of contrast medium) were not significantly associated with death after contrast medium administration.

CONCLUSIONS AND CLINICAL RELEVANCE

Although the administration of contrast medium cannot be conclusively confirmed as the cause of death in these birds, the high mortality rate for small birds coupled with the temporality of the event following contrast medium administration justifies the cautious use of contrast medium in small sick psittacine birds.

Gerontology of Psittacines

With recent improvements in the husbandry, nutrition, and veterinary care of captive psittacines, the avian clinician must be familiar with common medical condition seen in geriatric parrots. A review of the theory of evolution and avian senescence is provided. Five clinically relevant medical conditions are described: organ failure, atherosclerosis, neoplasia, cataracts, and osteoarthritis.