Abstract

Captive orangutans (Pongo pygmaeus, Pongo abelii) often suffer from upper respiratory tract diseases such as the common cold, sinusitis, or airsacculitis. While the diagnosis of airsacculitis is facilitated by obvious clinical signs, diagnosis of sinusitis is difficult and requires advanced imaging tools. The present study describes the use of computed tomography (CT) to compare the normal anatomy to the appearance of upper respiratory tract disease in orangutans.

For sinus evaluation in the orangutan, a high-resolution CT scanning technique is recommended with a slice thickness <0.75 mm and a slight overlap reconstruction. Image evaluation is recommended in the coronal plane and with a bone window set at the width of 1500 HU and the level of 300 HU. In the CT images, two paranasal sinuses were identified, which drain through recognizable ostia into the middle meatus and upper meatus of the nasal cavity. Using computed tomography, orangutans with a history of upper respiratory tract disease had numerous alterations within the sinuses. Alterations included thickened mucosal membranes, severe bone destruction, and fluid or pus-filled sinuses. All currently examined animals with airsacculitis also had a sinusitis, suggesting a possible relationship between these two diseases (e.g., sinusitis may be a predisposing factor for airsacculitis).

The current data suggests that CT scanning of the head represents an advanced imaging technique for early diagnosis of upper airway diseases in orangutans, and thus might allow the initiation of treatment to prevent complications such as airsacculitis.

Acknowledgments

The authors thank all participating zoos, curators, and keepers for their special care and help for this work.