Imaging Endocrine Systems

Question 1

what imaging modalities are used to evaluate endocrine organs

Answer 1

1. ultrasound
2. CT
3. nuclear scintigraphy
4. MRI

Question 2

what is ultrasound used to evaluate

Answer 2

parenchymal structure and characteristics and screening for disease in:
- adrenal glands
- pancreas
- thyroid
- parathyroid

Question 3

what is CT used to evaluate

Answer 3

identifying masses and surgical planning

Question 4

what is nuclear scintigraphy used to evaluate

Answer 4

functional imaging of the thyroid (hyperthyroidism)

Question 5

what is MRI used to evaluate

Answer 5

pituitary gland

Question 6

what are the borders of the adrenal glands

Answer 6

LEFT:
- cranial: cranial mesenteric and celiac arteries
- caudal: renal vein/artery
- medial: aorta
- phrenicoabdominal vein runs across the middle

RIGHT:
- cranial: right liver
- caudal: renal vein/artery
- medial: caudal vena cava, portal vein
- phrenicoabdominal vein runs across the middle

Question 7

what is the normal shape of the adrenal glands

Answer 7

smooth with rounded margins

dogs: left is peanut shaped, right is oval/boomerang shaped

cats: jelly bean shaped

Question 8

normal size of adrenal glands

Answer 8

dogs: 0.4-0.75 cm
cats: 0.3-0.5 cm

Question 9

echogenicity of the adrenal glands

Answer 9

hypoechoic or isoechoic to the spleen

mineralization can be normal in the cat but ALWAYS abnormal in the dog

Question 10

what does hyperadrenocorticism (Cushing’s) look like on US

Answer 10

pituitary dependent: bilateral adrenal enlargement

adrenal dependent: heterogenous mass in one adrenal with contralateral atrophy

iatrogenic: bilateral adrenal atrophy

secondary changes: vacuolar hepatopathy (enlarged and hyperechoic), mineralization of surrounding structures

Question 11

what does hypoadrenocorticism (Addision’s) look like on US

Answer 11

typical Addisons: bilateral adrenal atrophy

atypical Addisons: bilateral normal or small adrenal glands (only fasciculata is affected)

Question 12

what does a pheochromocytoma look like on US

Answer 12

heterogenous, solid (non-cavitary) mass in the adrenals
- can NOT differentiate cortical vs medullary
- if >2-4 cm and invasive –> malignant

Question 13

where is the pancreas located

Answer 13

pyloroduodenal junction (between duodenum and stomach/colon)

Question 14

what does diabetes mellitus look like on US

Answer 14

no visible changes to the pancreas (signs of pancreatitis possible)

Question 15

is ultrasound usually done to diagnose diabetes mellitus

Answer 15

NO - mostly used if previously diagnosed diabetes is difficult to control

look for signs of secondary underlying disease preventing control of diabetes

Question 16

what secondary findings are common with diabetes mellitus

Answer 16

• hyperechoic liver
• pyelectasis (dilated renal pelvis)
• emphysematous cystitis

Question 17

emphysematous cystitis

Answer 17

gas in the bladder wall/lumen from gas producing bacteria

Question 18

what does insulinoma look like on US

Answer 18

small, hypoechoic nodules (difficult to identify)

often metastasizes to the liver and adjacent lymph nodes - easier to identify than primary tumor

Question 19

what are the borders of the thyroid gland

Answer 19

• medial: larynx and trachea
• lateral: carotid artery
• caudal: medial retropharyngeal lymph nodes

Question 20

what is the normal size of the thyroid gland

Answer 20

dogs: 0.4-0.6 cm
cats: 0.2-0.3 cm

Question 21

what is the normal shape of the thyroid gland

Answer 21

ellipsoid/fusiform with smooth margins

Question 22

echogenicity of the thyroid gland

Answer 22

isoechoic/slightly hyperechoic to the lymph nodes and homogenous

Question 23

what does hyperthyroidism look like on US

Answer 23

unilateral or bilateral enlargement
(functional hyperplasia, nodular hyperplasia, adenoma, carcinoma)

Question 24

is hyperthyroidism more common in cats or dogs

Answer 24

cats - usually benign

if in dogs - usually malignant but non-functional

Question 25

what imaging is most commonly done to diagnose hyperthyroidism

Answer 25

nuclear scintigraphy - ingestion of radioactive tracer coupled to a metabolically active molecule that gets taken up by the thyroid gland and detected on scintigraphy

Question 26

what markers are used to ID hyperthyroidism on nuclear scintigraphy

Answer 26

radioactive iodine or pertechnetate

Question 27

what information does nuclear scintigraphy provide

Answer 27

if hyperthyroidism is unilateral or bilateral

presence of ectopic thyroid tissue

Question 28

what does a thyroid carcinoma look like on US

Answer 28

variably sized mass with cavitations, highly vascularized, and locally invasive into adjacent vessels

Question 29

where is the parathyroid located

Answer 29

adjacent to or within the thyroid near the cranial or caudal poles

NOT ALWAYS VISIBLE ON US

Question 30

normal shape and size of the parathyroid

Answer 30

< 2 mm
oval to round with smooth margins

Question 31

echogenicity of the parathyroid

Answer 31

very hypoechoic/anechoic

Question 32

what does hyperparathyroidism look like on US

Answer 32

enlarged parathyroid glands from hyperplasia or adenomas (NOT carcinomas)

does not change shape or echogenicity - only gets bigger

> 4 mm is likely adenoma not hyperplasia

Question 33

how does the pituitary gland appear on CT and MRI

Answer 33

CT: contrast enhancing region
MRI: T1 hyperintense, strongly contrast enhancing