Surgical Air Sac Resection as a Treatment for Chronic Air Sacculitis in Great Apes
Chronic air sacculitis has been documented as a prevalent problem in both free-ranging and captive great apes and monkeys.1-6,8 Air sacculitis is especially problematic in the orangutan (Pongo pygmaeus) and can lead to pneumonia which is often fatal.9 Conventional medical treatment for air sacculitis includes antibiotics, nebulization, and supportive care.3,4,7,8 More invasive measures include surgical closure of ostia to prevent the spread of pneumonia and/or air sac marsupialization to allow continual drainage.2,6-8 In cases where these treatments fail, resection of the air sac can be an alternative method of treating air sacculitis.
In the past, complete resection of the laryngeal air sac has been successfully performed in baboons (Papio anubis) without apparent clinical recurrence of infection.3,5 More recently, air sac resection has been performed in the following great apes:
An 11-year-old Sumatran male orangutan (Pongo pygmaeus abelii) housed at the Gladys Porter Zoo had recurrent air sacculitis. Prophylactic closure of the ostia had been performed at 5 years of age. Although the air sac was not distended, Pasteurella multocida was cultured from it at this time. At approximately 10 years of age, the animal developed distension of its laryngeal air sac and began having recurrent air sacculitis. Several attempts at marsupialization were unsuccessful and resulted in closure and refilling of the air sacs. Complete resection of the air sac was elected. Access to the air sac was through a horizontal incision across the neck. The air sac was completely reflected from the underlying epithelium. The use of electrocautery minimized bleeding and allowed the air sac to be easily removed in its entirety. During removal, the previously placed ostia closure sutures remained intact. The ostia were resected closer to the trachea and surgically closed. An attempt to minimize the large amount of dead space was made by tacking the skin to the underlying tissues. The incision was closed with an intradermal pattern using 2-0 absorbable suture. Surgical healing was successful, with moderate swelling in the first postoperative week and no evidence of an air sac or dead space within the first month. To date, there is no evidence of recurrence or surgical complications.
A 31-year-old female Sumatran orangutan (Pongo pygmaeus abelii) from the National Zoological Park had recurrent air sacculitis. Repeated marsupialization of the laryngeal air sac was unsuccessful, and a previously closed right ostia reopened. Air sac resection was performed, leaving a small amount of air sac to marsupialize around the open right ostia. The marsupialized air sac was later completely resected due to reinfection. Once the air sac was completely removed and the surgical site healed, no further complications from air sacculitis recurred. This animal was later euthanatized due to complications associated with gastrointestinal adenocarcinoma. At necropsy, the resection site looked excellent with no evidence of residual infection.
A 12-year-old male bonobo (Pan paniscus) had a history of intermittent soft tissue swellings at the thoracic inlet that did not fully resolve with short-term courses of antibiotics. Upon presentation at the Columbus Zoo, the infected air sac was again treated with oral antibiotics but began to slough, revealing a large, semi-fluid air sac abscess. Surgical resection of the infected air sac was performed, ligating the air sac at its connections with the larynx. Lateral extensions of the sac were dissected into the axillary regions where they could not be traced further. These were ligated at the most distal region identified. The area was copiously flushed with saline and the incision closed. The incision later dehisced and healed by secondary intention. Recovery from the surgery was uncomplicated, and no change in vocalizations were noted. Followup for the next 10 years did not show any recurrence of abscesses in this region.
Air sac resection is an uncomplicated and successful treatment modality for chronic air sacculitis in great apes and should be considered in cases of recurrence and/or chronicity. Surgical removal of the air sac provides a viable therapy for a chronic infection and prevention of the spread of the infection to the lower respiratory tract. It also alleviates the often-unsightly drainage from marsupialization sites, therefore improving public viewing while on exhibit. To date, no untoward effects have been noted from air sac resection. However, long-term sequelae may not yet be known, especially in the young male orangutan as it reaches sexual maturity.
Special thanks go to Carol Erwin, MD, Brownsville Medical Center, Brownsville, TX for performing the air sac resection at the Gladys Porter Zoo and Bud Siemering, DVM, South Paws Veterinary Clinic, Springfield, VA for performing the air sac resection at the Smithsonian National Zoological Park.
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