Mass removal in a sun bear - Veterinary Practice
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Mass removal in a sun bear

A breakdown of the surgical removal of a mass, recovery and complication of necrotic infection in a Borneo sun bear, Helarctos malayanus

Sun bears, Helarctos malayanus, are the smallest species of bear and are found in Southeast Asia. Listed as vulnerable to extinction (IUCN, 2016), they are often poached illegally in the wild, with cubs taken as “pets”. The Borneo Orangutan Survival Foundation (BOSF) is one of the organisations providing in situ support and conservation of this species. This article will discuss the author’s experience of working with a sun bear, Meli, at the BOSF.

FIGURE (1) An unidentified mass on the left flank of a sun bear, Meli

Meli was an adult female sun bear that was not spayed and was believed to be around four years of age. During the author’s time at BOSF, Meli had a mass of unknown causation on her left flank that had been present for an unknown period of time (Figure 1). However, it was found to be increasing in size and irritating to the patient. On viewing, the mass seemed to have had either a potential causation puncture wound or an area where patient interference had occurred; however, this could not be confirmed until a full examination could be performed under general anaesthesia.


Meli was provided with a sedative medication of ketamine (120mg/kg) and medetomidine (3mg/kg) via blow dart into her right hind gluteus muscle (Figure 2). Her weight was estimated at 45kg but was found to be 33kg on weighing prior to surgery – a significant decrease since she was previously weighed. Even though she had been fasted for 12 hours prior to surgery, Meli had a period of vomiting post-darting. The time for the medication to take effect was around 40 minutes before she was safely able to be transported to the clinic for surgery.

In the clinic, an intravenous catheter was placed into her jugular vein, and she was then provided with propofol for full induction. Once fully induced, she had an endotracheal tube placed and was maintained on isoflurane and oxygen during the procedure (Figure 3). Intravenous fluids were provided at a rate of 10ml/kg/hr. The entire procedure, from darting through to recovery in the enclosure, was around four hours. A pulse oximeter was used throughout the surgery, and Meli maintained an oxygen saturation of around 98 percent, an average respiration rate of 18 and an average heart rate of 68. Her temperature never dropped below 37.6°C, and no external heating was used due to the climate.

Examination and mass removal

FIGURE (4) The surgical site of the mass post-removal

When the mass was fully examined, it was found that the marks seen on the mass were likely to have been from patient interference instead of a puncture wound. The mass was removed surgically with adequate margins taken, and the surgical site was closed with a polyglycolic acid suture (Figure 4). The mass was then sent for external histology and, in the interim, Meli was placed on a course of meloxicam (3.5mg/kg SID), amoxicillin-clavulanic acid (650mg/kg BID) and metronidazole (1000mg/kg BID).

During general anaesthesia, Meli reacted during one aspect of the surgery, and therefore more ketamine was provided for analgesia. Overall, her general anaesthesia was stable with only a small period of cardiac dysrhythmia when she responded to pain during the procedure. Her recovery from anaesthesia was uneventful, and she was provided with atipamezole to speed up her recovery once she was back within her enclosure.  

Recovery and complications

FIGURE (5) The discolouration of Meli’s inner thigh prior to the primary surgical debridement

Initially, Meli made a slow but steady post-surgical recovery, which was partly due to her refusal to take medication hidden in the food items offered to her, with her favourites (scrambled egg and melon) both failing to hide the taste of the antibiotics. However, after a few days, her carers reported an area of discolouration on her inner right thigh (Figure 5). Unfortunately, it was impossible for the veterinary team to get a clear view of this area due to her wariness following the darting. As this discoloured area was clearly bothering her, with consistent grooming patterns seen throughout the days of observation, the decision was made to sedate, assess and treat her as required. Meli was sedated and placed under general anaesthesia following the protocols listed earlier.

On inspection, the area was found to have a small puncture wound, and it was discovered that the skin around it was necrotic (Figure 6A). The affected skin was removed, and the rest was sutured together; however, concerns were noted about the likelihood of wound breakdown. A swab of the affected area was taken and sent away for examination.

On recovery, Meli was provided with an increase in analgesia. Her ability to exercise was also limited further to minimise the risk of skin tearing around the suture site. Unfortunately, the wound reopened and several days later, it had worsened beyond the ability to allow secondary healing to occur (Figure 6B). A pus-like substance was also reported to be present. As such, the decision was made to re-anaesthetise and perform a further surgical debridement of the wound site (Figure 6C). Further sutures were placed, but only at the ends of the wound, as a decision was made to allow the central region to heal via secondary intention to minimise stress due to wound location (Figure 6D).

After several months, Meli had made a full recovery, and both surgical sites were fully healed (Figure 7). She possessed full movement and no sign of the mass has been reported as returning.

Final thoughts

Due to the remote location of BOSF and the fact that the samples had to be sent to an external human hospital for analysis, the time for the results to be returned was comparatively prolonged. When the mass result came back, it was found to be a multicentric squamous cell carcinoma in situ, effectively Bowen’s disease.

In addition, the necrotic skin bacteria was reported as Aeromonas hydrophila which was antibiotic resistant. As a result, Meli was placed on a course of tetracycline for three weeks. Aeromonas hydrophila is a relatively common Gram-negative bacterium in tropical climates and is particularly prevalent in areas with high-standing water, eg tropical rainforests.

It is theorised that Meli somehow had a small puncture wound or bite in the inner part of her thigh before introducing the bacteria through grooming.


International Union for Conservation of Nature (IUCN)


Sun bear. IUCN Red List

Adam Gregory

Head Nurse at Great Western Exotics

Adam Gregory, Bsc (Hons), CertHE, DMZAA, RVN, DipVNZS, APVN (Zoo, Wildlife, Small Mammal, Avian, Reptile and Amphibian), NCert (Anaesth), has attained experience globally as both a zoo keeper and a veterinary nurse, leading to combine the two areas into his current role. He has developed a particular interest in anaesthesia of non-domestic species.

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