Imaging of the pituitary gland in dogs with pituitary-dependent hyperadrenocorticism.

Detailed imaging of the pituitary gland is a prerequisite for a successful outcome of transsphenoidal hypophysectomy in dogs because it allows for accurate preoperative localization and assessment of the size of the pituitary gland. Cisternography allows assessment of even small increases in the height of the pituitary gland, but the magnitude of suprasellar expansion of pituitary tumors cannot be assessed with this technique. Large pituitary tumors with suprasellar expansion can readily be detected with conventional contrast-enhanced computed tomography (CT), while pituitary microadenomas can be localized with dynamic contrast-enhanced CT. Dynamic examination of the entire pituitary may be possible with spiral dynamic CT. Magnetic resonance imaging (MRI) of the canine pituitary gland provides a clear differentiation between the pituitary gland and the surrounding structures, but it remains to be investigated whether in dogs MRI can replace dynamic CT for the detection of microadenomas and whether it allows accurate localization of the pituitary gland relative to the surgical landmarks.