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Imaging Of Endocrine Organs

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sihirlifil's version from 2017-11-16 23:45

Thyroid & Parathyroid

Question Answer
Normal thyroid anatomyPaired organs, either side of trachea. Spindle-shaped. 2.5-3x0.4-0.6cm in dog; 2x0.2-0.3cm in cat
Ultrasound technique for thyroid glandDorsal recumbency, sedated, head extended. Clip, clean, gel
Linear transducer >8MHz
How does the thyroid look on US?Spindle-shaped on either side of trachea, caudal to larynx
Finely granular, well-defined, iso- or hyperechoic to surrounding muscles (sternohyoid, sternothyroid, sternocehpalic)
Parathyroid glands at extremities
Blood supply to the thyroids?Thyroid aa & vv
Dog: Cranial & caudal
Cat: Only cranial
Can be seen with Doppler
What is this image showing?
Normal salivary gland & retropharyngeal LN
Thyroid adenocarcinoma in a dog
How do thyroid neoplasms behave in the dog?Most are not hormonally active
May metastasize to lungs, LN (check the retropharyngeal!!!)& locally invasive (do plain thoracic rads for met check)
How does adenomatous hyperplasia/adenoma behave in a CAT?Hyperthyroidism in most cases (benign hormonally active)
Elevated T4 & T3
Thyrotoxicosis
What is thyrotoxicosis?In CATS: hypertension, secondary cardiac hCMP, renal disease, cachexia
How does adenomatous hyperplasia/adenoma look?Mostly bilateral
Possibly small atrophied contralateral thyroid gland due to neg feedback from hypophysis
How is adenomatous hyperplasia/adenoma diagnosed?US examination, FNA
Scintigraphy: types of scans?RP: 99mTcO4- (Pertechnetate) IV Morphologic scan: Presence & amount of thyroid tissue (Pertechnetate is stored in thyroid but not organified, imitates iodine)
131I or 123I (Isotope of iodine) IV Functional scan (hormonally active tissue present? Iodine is organified, can destroy tissue)
Scintigraphy: what should the thyroid's uptake of RP be like?Similar to the salivary glands (localized cranial to thyroid glands)
Scintigraphy: what must also be imaged? why?Thorax; may be ectopic thyroid tissue (more common in dogs)
What's the difference in these scans?
(ventral acquisition, cat in sternal position on top of gamma camera)
Left: cat with normal thyroid glands
Right: Hyperthyroid cat with unilateral adenoma, enlarged R thyroid gland with stronly increased uptake, contralateral probably atrophied
What's going on in this scan? (6y male lab)
Large, differentiated & locally invasive thyroid carcinoma with extensive pulmonary metastases (arrow)
Involvement of retropharyngeal LN likely
What's happening with these scans?
Top left: Pre-op, hyperfunctional thyroid gland CA
Top right: Post-op, small amount of residual thyroid tissue
Bottom: Post-radioactive iodine therapy
Ectopic thyroid tissue in a cat (RARE)
Arrows? (Saggital & dorsal, CT thorax, ST window)
Ectopic thyroid tissue (cranial mediastinal mass)
Which modalities? Showing what?
Left: CT, ST window
Right: MRI
Allow assessment of size, extent & involvement of adjacent structures of a thyroid mass- important to know prior to a potential surgery(invasion of fascial planes = more difficult sx)
Anatomy of parathyroid glands4 single glands, 2 at cr & 2 at cd thyroid extremities
Size of rice corn
How do you US the parathyroid glands?First ID the thyroid (arrows), then look cranial-mid-caudal thyroid
Hypoechoic relative to thyroid
Need high freq (12MHz) linear
Parathyroid adenoma in a dog (orange arrows = thyroid)
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Adrenal glands & Pituitary

Question Answer
Anatomy of the adrenal glandsLeft: Medial to kidney, cd to Cr mesenteric a., Lateral to the Ao, Cr to the l. renal a. (peanut-shaped in dog, bean-shaped in cat)
Right: Medial to R kidney, Cr to Cd mesenteric a., between CVC & Ao (boomerang in dog, bean/oval in cat)
Something to note about canine adrenal glands?Difference in shape
How do cat adrenal glands compare to each other?Same shape
Adrenal gland enlargement (neoplasia)
How does neoplasia affect the adrenal glands?Enlarges them asymmetrically, alters echogenicity, internal architecture, and shape
HAC: features of abdominal radiographs?Large abdomen
Fat deposits
Hepatomegaly
+/- calcinosis cutis
Hyperadrenocorticism (liver beyond costal arch, fat deposits)
HAC: how does it affect the liver?Steroid hepatopathy
Hepatomegaly
WHat's wrong with this liver?
Steroid hepatopathy (HAC): Hyperechoic liver due to vacuolization (liver is isoechoic to the spleen, should be hypoechoic)
What's wrong with this liver?
Hepatomegaly (HAC)
Hyperechoic & enlarged liver with rounded margins (compare to normal spleen)
Ddx for hepatomegalyHepatic lipidosis
Steroid hepatopathy
Hepatitis
Lymphoma
Mast cell infiltration
Sonographic findings of pituitary hyperadrenocorticismBilateral generalized adrenal gland enlargement
Morphology & echogenicity maintained
Caudal pole diameter >7.5mm
Further workup of PDH includes:Assessment of the hypophysis/pituitary gland
Pituitary-dependent hyperadrenocorticism (Cd pole diameter 1.6cm left, 1.2cm right)
This is a dorsal plane CT, ST window... label it
(top to bottom)
Left: Liver, R kidney, R adrenal
Right: Fundus, Celiac artery, Cr mesenteric artery, L adrenal, L kidney
Where is the pituitary gland? how can you visualize?In sella turcica of base of skull
Cannot be visualized via radio or US! Need cross-sectional imaging modalities: CT & MRI
Macroadenoma = ?Visible space-occupying lesion
Microadenoma = ?Lesions too small to ID on plain studies but show abnormal behavior in dynamic CT contrast studies
Pituitary adenocarcinoma: how to dx?CT contrast studies statically or dynamically (i.e. showing abnormal CM uptake or abnormal hypophyseal perfusion)
Macroadenomata become visible as masses, microadenomata may alter normal perfusion pattern
Which modalities? showing what?
Left: Contrast CT transverse ST window. Arrow = CM accum in pituitary gland area
Right: MRI transverse T2. Arrow = pituitary gland
Which modality? which structure?
MRI sagittal T1 with and w/o contrast, showing NORMAL pituitary gland/hypophysis
Which modality? which structure?
Transverse CT with and w/o CM, and with sagittal reconstruction
Enlarged hypophysis (macroadenoma)
Microadenomas need to be imaged how?Dynamic CT studies (masses per se are not visible)
Which modality? Problem?
MRI of hypophyseal neoplasia
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Pancreas

Question Answer
Anatomy of the pancreasLeft (gastric) & right (duodenal) lobe + body
Pancreatic duct
Pancreaticoduodenal vein (R limb)
Papilla duodeni
Size of pancreasLobe thickness 4-6.5mm (older animals have larger)
CAT: L lobe & body 5-9mm, R lobe 3-5.7mm
DOG: 3.5-16mm thickness (ref value 1cm for medium-sized dogs)
How does the pancreas look on radiographs?Generally not visible on abd rads (maybe if mesenteric fat)
How does the pancreas look on US?Difficult to differentiate from surrounding tissue
Fast patient for at least 12 hours (stomach needs to be empty)
How can you examine the pancreas?Radiology, US, CT (contrast, IV iodinated) (MRI)
Anatomy of pancreas: dogRight lobe (duodenal), left lobe (gastric), body
Right lobe larger
Anatomy of pancreas: catRight lobe (duodenal), left lobe (between spleen & splenic v., L kidney, transverse colon)
Left lobe larger
Pancreatitis (dog)
Radiographic signs of pancreatitisLocalized loss of serosal detail in R cranial abdomen (inflam of surrounding mesentery, focal effusion, peritonitis, steatitis)
Mass effect: desc duodenum displaced lat, duodenum focally gas distended (ileus), +/- stomach & colon distention
Where do you find the left lobe of the pancreas on US?Between greater curvature of the stomach & colon
Splenic vein & spleen are lat & ventral to it, tip runs towards L kidney
Left lobe larger & easier to image in cat
Where do you find the right lobe on US?Ventral & medial to R kidney
Mediodorsal to duodenum (shares mesentery). Easier to image in dog
Pancreatic duct may be imaged in long axis of pancreas (may be enlarged in older cats)
How can we use doppler with the R lobe?Allows to differentiate the pancreatic duct from the pancreaticoduodenal vein (there is flow in the vein but not in the duct)
Where do you find the body on US/Caudal to the stomach, cranial to the transverse colon
Sonographic findings of pancreatic diseasesEchogenicity: becomes hyper/hypo echoic
Size: often enlarged, atrophy in chronic
Shape: Rounded margins
Contour: inflam changes blur
Pancreatic duct may be widened
Surrounding tissue often becomes hyperechoic & blurred (steatitis of mesenteric fat --> fat necrosis)
Free fluid may surround pancreas
Problem?
Acute pancreatitis
Orange = free peritoneal fluid
US signs of acute pancreatitisMixed echogenicity (necrosis, hge) w/ hyperechoic surrounding tissue
Plump margins
Pancreatic edema (hypoechoic streakes between lobules of tissue) & free peritoneal fluid
Problem?
Chronic pancreatitis
US signs of chronic pancreatitisDiscrete lobular fibrosis, small echogenic pancreas (questionable clinical relevance)
Pancreatic nodular hyperplasia
Orange arrows = hypoechoic nodules
What is nodular hyperplasia?Benign process, higher incidence in older patients (many older cats, some dogs). Often multiple
How can you ddx nodular hyperplasia from neoplasia?Histopathology
Pancreatic neoplasia (obviously lol)
Types of pancreatic neoplasiaExocrine tumors
AdenoCA
Sarcoma (few reports)
Endocrine
Insulinoma (dogs)
Other e.g. lymphosarcoma
Pancreatic neoplasia more common in?Dogs... less rare than cats but still uncommon
Dx test of choice for pancreatic neoplasiaCT contrast study
Insulinoma
CM accumulation, hyperintense nodule
(Irregular contour of L kidney)
Why does US often fail to demonstrate insulinoma?Small size & often large/obese dogs
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