Читать книгу Canine and Feline Epilepsy - Luisa De Risio - Страница 82

Neurological signs consistent with hypoglycaemia (blood glucose concentrations below 60 mg/dl or 3 mmol/l) and concurrent hyper-insulinaemia (serum insulin concentration greater than 20 μU/ml) are suggestive of insulinoma. When a dog suspected of having an insulinoma is normoglycaemic, it should be fasted under close observation and blood glucose concentration should be measured every 1 to 2 h. Most dogs with insulinoma would develop hypoglycaemia within 12 h of fasting. When hypoglycaemia (blood glucose concentration <60 mg/dl or <3mmol/l) is detected, blood should be collected for measurement of insulin concentration and the dog should then be fed (Hess, 2010). Some dogs require repeated insulin measurements to confirm the suspicion of insulinoma. In one study hyperinsulinaemia was detected in 76% of dogs with insulinoma when insulin was measured once and in 91% of dogs when insulin was measured twice (Leifer et al., 1986). Fructosamine concentration can help to detect chronic hypoglycaemia as this parameter reflects the blood glucose concentrations over the previous 1–2 weeks and it has been reported to be significantly decreased in dogs with insulinomas. The clinical diagnosis of insulinoma can be further supported by identification of a pancreatic mass with abdominal ultrasonography or contrast-enhanced computed tomography (Figs 4.1, 4.2a, b). The sensitivity of abdominal ultrasonography in detecting insulinoma ranges from 28% to 75% (Goutal et al., 2012). Contrast-enhanced ultrasonography may increase the diagnostic yield of ultrasound. Ultrasound-guided fine-needle aspirate cytology represents a relatively noninvasive tool to support the diagnosis of insulinoma. The definitive diagnosis is made following histological examination of the tumour after surgical resection.

Fig. 4.1. Ultrasonographic image of the right craniodorsal abdomen obtained using an intercostal approach in a 7-year-old, male boxer presented for seizures. An irregularly rounded 16 mm diameter hypoechoic nodule (between calipers) is present within the cranial aspect of the right limb of the pancreas. Note that in order to optimize the image of the nodule normal anatomic landmarks such as the duodenum (arrow) and the pancreatic vessels are only partly demonstrated in the image. (Photo courtesy of Andrew Halloway)

Fig. 4.2. Pre- and post-contrast CT images of the abdomen of a dog with an insulinoma in the left limb of the pancreas. On the pre-contrast image (a) the lateral aspect of the left limb of the pancreas is focally enlarged by a 15 mm diameter nodule (arrow). The nodule is slightly hypo-attenuating to adjacent normal pancreas. The post-contrast image (b) was obtained during the arterial phase of angiography. There is marked enhancement of the periphery and medioventral aspect of the mass. The dorsolateral aspect of the mass does not enhance (arrow). (Photo courtesy of Fraser McConnell, University of Liverpool)