TREATMENT OF A RETROPERITONEAL ABSCESS BY OMENTALIZATION IN AN ORANGUTAN (PONGO PYGMAEUS PYGMAEUS

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Norin Chai, DVM., MSc., MSc.V., PhD, Dipl. ECZM (ZHM)

 

Norin Chai, DVM., MSc., MSc.V., PhD, Dipl. ECZM (ZHM)

Clinical case

 

A 38-yr-old female wild-born Bornean orangutan (Pongo pygmaeus pygmaeus) with no major clinical problems, presented with chronic lethargy and difficulty in locomotion. The animal was housed at the Me´nagerie du Jardin des Plantes- National Museum of Natural History (Paris, France) with two males and two females, all captive-born. The orangutan developed mild lethargy, anorexia, and at times, mental deficits. Clinical signs progressed from weakness and less frequent ambulation to permanent dorsal recumbency, lateral recumbency, or both.

On day 1, 1 wk after the onset of clinical signs, the orangutan was immobilized with 300 mg of ketamine hydrochloride (4.8 mg/kg i.m.) by Blow dart. Anesthesia was maintained by intermittent supplemental boluses of 200 mg of ketamine every 20 min (3.2 mg/kg i.v.). A constant slow rate infusion intravenously of 0.9% NaCl was administered.

The orangutan’s respiratory rate, heart rate, and pulse oximetry were monitored with a hand-held pulse oximeter. Physical examination and palpation revealed a mild chronic periodontal disease and a left retroperitoneal mass. Hematology, serum biochemistries, thyroid panel, and transthoracic echocardiogram were within normal limits. Serologic titers for herpes simplex type II, herpes B, and herpes SA8; human and simian immunodeficiency; measles; and rubella were negative. Lateral and ventrodorsal abdominal radiographs demonstrated no clear and remarkable lesion other than mild arthrosis on the lumbar vertebras.

blood sampling

TREATMENT OF A RETROPERITONEAL ABSCESS BY OMENTALIZATION IN AN ORANGUTAN (PONGO PYGMAEUS PYGMAEUS)

Abdominal ultrasonography revealed a mass composed by two hypoechogenic cavities with regular margins compatible with a 12-cm X 8-cm X 8-cm left retroperitoneal abscess, cranial and dorsal to the bladder. Guided by ultrasonography, aspirate from the fluid pocket resulted in the collection of purulent liquid. A cytology examination of the fluid revealed high cellularity, with an inflammatory cell population composed entirely of neutrophils and a heterogeneous bacterial population composed of high numbers of cocci and bacilli, often observed intracellularly.

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TREATMENT OF A RETROPERITONEAL ABSCESS BY OMENTALIZATION IN AN ORANGUTAN (PONGO PYGMAEUS PYGMAEUS)

The specimen was sent for bacterial culture and sensitivity. On the basis of these findings, a diagnosis of a retroperitoneal abscess, pyometra, or both was made. The animal received 40 mg of meloxicam (0.64 mg/kg s.c.). An exploratory laparotomy revealed a normal uterus, a retroperitoneal abscess, and enlarged lymph nodes. The abscess was adhered to the bladder, the mesentery, and the soft tissues adjacent to the mass. The mass ruptured upon handling, thus releasing a substantial quantity of pus into the abdominal cavity. The abdominal and abscess cavities were drained using surgical suction. The volume of pus was estimated to be approximately 500 ml. The site was initially rinsed with sterile 0.9% NaCl. Suction was used to evacuate the fluid, and the process was repeated several times. In addition, 800 mg of gentamicin (12.8 mg/kg) was then poured into the abdominal cavity and evenly distributed. Digital exploration of the abscess revealed a ramification close to the vertebral canal.A lumbar-sacral fistulization was suspected. Because of the difficulty separating the abscess from its attachments, only a small portion of the visible membrane was removed. Two bacterial species were cultured from the initial ultrasoundguided aspirate of purulent fluid: Streptococcus and Escherichia coli. Both of these organisms were susceptible to cephalosporins and fluoroquinolones. Histologic examination of the membrane confirmed an inflammatory component rather than a neoplastic process.

The decision was made to create a physiologic drain of the abscess with a functioning omental flap, as described previously in humans, dogs and cats. The remaining abscess cavity was then packed with omentum. The omentum was attached to the abscess membrane with two simple large sutures by using an absorbable suture material. The abdominal wall was closed in two layers (peritoneum and muscular layers) with a continuous suture pattern by using a monofilament nonabsorbable suture material. The skin was closed by a hypodermic running suture, and a simple interrupted suture pattern by using an absorbable suture material. After completion of the surgery, and while still immobilized, the animal was administered 40 mg of meloxicam (0.64 mg/kg s.c.) and 5 ml of a solution containing ascorbic acid, thiamine, pyridoxine, and niacin (Nutra B, Fort Dodge; 0.2 ml/kg i.m.). Systemic antibiotics were administered via injection and include 560 mg of cefovecin (8.58 mg/kg s.c.) and 540 mg of danofloxacine (8.28 mg/kg s.c.). In total, 1,200 mg of ketamine had been administrated to the orangutan to achieve a 125-min period of anaesthesia. The total surgical time was 50 min, and recovery was uneventful and rapid. The animal was placed in its enclosure in lateral recumbency. Forty-five minutes after the last ketamine bolus, the animal demonstrated normal activity and was moving and sitting. A postsurgical analgesia treatment was initiated with 45 mg of meloxicam (0.69 mg/kg p.o., s.i.d. for 5 days.

In humans, retroperitoneal abscesses are not common clinical conditions. The causes of retroperitoneal abscesses include psoas abscess, necrotizing fasciitis, pancreatitis, perforated acute appendicitis, and duodenal diverticulum perforation. The abscesses are often diagnosed by a computed tomography scan. Draining of the abscess without any surgery may be sufficient in some cases, such as a psoas abscess. However, in rare cases, retroperitoneal abscesses may be lethal, even after surgical drainage. In both dogs and cats, retroperitoneal abscesses are usually unilateral. They can be associated with trauma, infection, and depositions of foreign material during surgical procedures and urinary extravasation. In this report, culture isolation of Streptococcus and E. coli suggests that infection was consistent with an ascending bacterial infection from the lower urinary tract, reproductive system, or digestive system. However, no cultures of other organs or fluids were performed to attempt to localize the source of infection. Actually, omentalization is considered to be the treatment of choice for prostatic and pancreatic abscesses in dogs as well as for large and chronic nonhealing wounds, uterine abscesses, and idiopathic chylothorax in a cat. The omentum contains aggregates of blind lymphoid capillaries that provide lymphatic drainage of the peritoneal cavity.  This treatment has not been reported previously in orangutans. Omentalization was successful in providing a continuous method of fluid drainage for this retroperitoneal abscess, with minimal requirement for postoperative procedures of the animal.