Wednesday, August 7, 2013

Three things I learned: endocrine disease in companion animals

SAT readers will recognise this CT image as that of a cat, Bart, who had an adrenal tumour (circled). Adrenal glands, when they aren't pathologically enlarged, can be very tricky to find on ultrasound unless you know the landmarks.

Here at SAT we have learned two things about learning three things: 
  1. Attending a lecture with the aim of learning and recalling three things definitely helps us retain the information (maybe a little study tip there?)
  2. Its VERY difficult to limit our learning to three things. So for those of you who are good at counting, please give us a little leeway...
Small animal specialist Dr Christine Griebsch gave a comprehensive talk about the use of trilostane to manage hyperadrenocorticism. Her protocol is a little different to the traditional management regime.

  • Recent studies have shown that twice daily administration of trilostane at a lower dose resulted in better control of signs, and that the ideal time to run the ACTH stim test was 2-3 hours post administration rather than 4-6.
  • At follow up she looks at the history, physical exam, ACTH stim and electrolytes 1-2 weeks following commencement of treatment, then at 3-4 weeks, 6-8 weeks 12 weeks and every 3-6 months thereafter.

Small animal resident Dr Joanna Whitney gave an excellent talk on the diagnosis and management of diabetic ketoacidosis. 
  • The most important thing that I learned was that of all dogs diagnosed with DKA, 70% have concurrent disease (commonly pancreatitis, bacterial UTI or hyperadrenocorticism) and in cats 90% have concurrent disease (commonly hepatic lipidosis, chronic renal insufficiency, pancreatitis, bacterial infection) or it may be a complication of glucocorticoid administration.
  • So it seems logical that work up of a DKA patient, aside from the general tests such as CBC/MBA/UA, should include urine culture and sensitivity, cPLI or fPLI, abdominal ultrasound, thoracic radiographs and possibly an ACTH stim test.

Finally, diagnostic imaging specialist Dr Mariano Makara gave a very passionate talk about imaging adrenal glands. As he said when one is learning ultrasound, the adrenals and the pancreas are the holy grail as they can be so difficult to locate. He used some amazing CT images to give an anatomical review of the location of the adrenals, and fortunately there are plenty of landmarks for these.
The adrenals are
  • -          Caudally in contact with the renal veins
  • -          Ventrally in contact with the phrenicoabdominal veins
  • -          Dorstally bordered by the psoas muscle
  • The right adrenal is in contact with the caudal vena cava (medially) and the right kidney (laterally) – this is a lot harder to locate as it is more cranial and tends to be protected by the rib cage.
  • The left adrenal is in contact with the aorta (medially) and the left kidney (laterally).

Once you find them, as he explained, interpretation is not too difficult…they should have a short axis of 0.6mm in a small breed dog and 0.7mm in a large breed, and enlarged adrenals look puffed up. Adrenal masses generally look quite distinct.
CT is often required to confirm invasion of the caudal vena cava by an adrenal tumour, and this is something that Dr Makara recommends for any dog about to undergo adrenalectomy.

You can read more about Bart's adrenal tumour - and his concurrent brain tumour - both successfully treated - here.




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