A six-year, eight-month-old male neutered rabbit was presented to the veterinarian as a transfer from the emergency provider after suffering an acute collapse.

History

The rabbit had been found by the owner underneath the bed 48 hours prior, listless. Until then the owner had no concerns – the rabbit had been eating, drinking and toileting normally.

Aside from chewing cardboard periodically, no known toxin exposure had occurred.

Examination

The rabbit presented to the clinic quiet and responsive, with a heart rate of 180bpm and respiratory rate of 200bpm.

Abdominal palpation was comfortable and gut sounds were present bilaterally. Nephromegaly was present, with the left kidney being markedly enlarged, with no other abnormalities on palpation. The rabbit had lost 1.5kg over 12 months and, on presentation, had a body condition score of 3/9.

Aside from bilateral protrusion of the nictitating membranes, skin, eyes and ear examination was unremarkable.

The rabbit started to seizure 30 minutes after being admitted to the hospital and a blood sample was taken (Table 1). Blood glucose was measured as too low to read.

Midazolam was given IV, along with a slow glucose bolus administered over 10 minutes (1ml of 50% solution diluted with 2ml sodium chloride 0.9%). The seizure resolved, so a constant rate infusion (CRI) of 5% glucose at 2ml/kg/hour was then initiated, but had to be increased to 4ml/kg/hour soon after due to persistently low blood glucose measurements.

Approximately 30 minutes after starting the latter CRI, the rabbit sat up in sternal recumbency, ate hay and herbs, and defecated normal faecal pellets.

Over the next few hours the rabbit’s demeanour appeared variable and blood glucose only increased to 3.6mmol/L despite another IV glucose bolus. A second seizure occurred later that evening, which resolved on administration of an IV glucose bolus.

Due to the rabbit’s inability to maintain normoglycaemia, treatment for a suspected insulinoma was started using diazoxide at 8mg/kg orally twice daily. Coupled with diazoxide, the rabbit received gabapentin 5mg/kg twice daily, fenbendazole 20mg/kg once daily and ranitidine 4mg/kg twice daily, all orally.

Over the next 24 hours, the rabbit’s blood glucose levels ranged between 3mmol/L and 14.7mmol/L, and the rabbit improved clinically with no more seizures seen, although periods of hyperaesthesia were noted when the rabbit was touched.

Trimethoprim sulphonamide was added to the treatment regime at 30mg/kg orally twice daily as swelling and erythema were found in the pinna, possibly linked to previous catheter sites. The rabbit developed diarrhoea, so cholestyramine 2g mixed with 20ml water orally once daily, and a high-fibre paste were added as therapeutics.

A blood sample was taken which showed mild hyperglobulinaemia and elevated creatinine (Table 2).

Abdominal ultrasonography was performed to evaluate the kidney architecture, which detected increased echogenicity of the pelvis and capsule of both kidneys. Hyperechoic streaks were consistent through the medulla, indicative of chronic renal disease. Both kidneys were enlarged with the following measurements:

• left kidney: 3.16cm × 2.18cm (normal length 2.86cm +/- 0.33mm; width 1.72cm +/- 0.19mm)
• right kidney: 3.91cm × 2.73cm (normal length 2.87cm +/-0.34 mm; width 1.62cm +/- 0.17 mm)

Medical treatment continued, and the rabbit gradually improved clinically and started to pass more normal faeces. On day three, a decision was made to discontinue the glucose CRI – but once stopped, the rabbit’s glucose levels remained low; between 1.8mmol/L and 2.4mmol/L.

Steroid treatment was discussed, as the most likely differential diagnosis was an insulinoma. Adverse side effects and risks – such as immunosuppression – were discussed with the owner, but this was advised over surgical exploration and possible treatment due to the concurrent renal pathology.

Dexamethasone 0.5mg/kg SC was administered, followed by prednisolone at 2mg/kg orally twice daily on day four. The glucose CRI was also reinstated, and the blood glucose levels fluctuated between 2.9mmol/L and 10.1mmol/L. No seizures had been reported since day one.

Unfortunately, over the following 48 hours the rabbit deteriorated clinically, appearing subdued and weak. A repeat blood sample was taken, which showed significantly elevated renal parameters suggestive of renal failure, and euthanasia was elected based on the grave prognosis (Table 3).

Insulinoma in rabbits

Insulinomas are functional insulin-secreting tumours of the pancreas originating from the beta-cells.

While heavily documented in ferrets and dogs, tumour prevalence is rarely reported in other species – only two cases in the literature have documented insulinomas in rabbits (Foxx et al, 2022; Harcourt-Brown and Harcourt-Brown, 2012). Treatment often involves the use of glucocorticoids, but surgical excision is recommended in ferrets and dogs (Bonagura et al, 2000).

Both glucocorticoid and thiazide therapeutics were well-tolerated in this case, but the severity of the renal failure ultimately prohibited surgical intervention and, therefore, gave the rabbit a grave prognosis that resulted in a recommendation of euthanasia.

Insulinoma should be added to any differential when seeing neurological and hypoglycaemic cases in rabbits.

• Some drugs mentioned in this article are used under the cascade.