4.5 Adrenal

Question 1

Anatomy and blood supply

Answer 1

4-6 cm long, limbs 3-6 mm thick
Cortex (90% of gland) from mesoderm, divided into zona glomerulosa (aldosterone), fasiculata (cortisol), reticularis (epiandrosterone)
Medulla from neuroectoderm, secretes adrenaline and noradrenaline
Adrenal arteries: superior (inferior phrenic), middle (aorta), inferior (renal)
Adrenal venous drainage - right to IVC, left to left renal vein

Question 2

Adrenal adneoma

Answer 2

2-10% at autopsy, 1% at abdominal CT; majority non-functioning
If no malignancy, lesion < 10 HU at CT Sn 71% Sp 98% for adenoma
Wash out by >60% (absolute) (40% relative (to enhanced) at 15 minute CT
MR - if non-functioning, isointense T1W and iso-/hyperintense on T2W to liver, with drop off on out of phase

Question 3

Adrenal myelolipoma

Answer 3

Rare, benign, encapsulated, always non-functioning
Can haemorrhage spontaneously and become necrotic
Demonstrate intralesional fat
US: hyperechoic
CT: heterogeneous ± calcification (20%; especially post haemorrhage)
MR: high T1W if fat or haemorrhage, drop off out of phase if fat

Question 4

Adrenal cysts

Answer 4

20% bilateral; may calcify even at > 1 year post haemorrhage

Causes:
Spontaneous, especially if coagulopathic;
Post-traumatic (right > left), burns, sepsis (DIC - Waterhouse Freidrichsen), post adrenal venography (10% risk)
Haemorrhagic metastases (melanoma)

Question 5

Phaeochromocytoma

Answer 5

Catecholamine secreting from chromaffin cells of medulla
85% adrenal, 8% paraaortic, 5% organ of Zuckerkandl, 1% urinary bladder
Cause headaches, palpitations, sweating, tremor, anxiety, HTN (but only 0.1% HTN caused by phaeo)
Increased vanilmandelic acid on 24 hour urine (50%)

Usually > 3 cm, solid, hypervascular; rarely calcified / cystic
Uptake on MIBG (80% Sn), octreotide, PET
Enhances strongly on CT; ‘light bulb’ very high signal on T2W MR
Bx: may precipitate hypertensive crisis

Rule of tens: 10% bilateral / familial / malignant / extra-adrenal; 98% intra-abdominal

If extra-adrenal, called paragangliomas, 40% malignant, most common at organ of Zuckerkandl (aortic bifurcation)

Syndromes: MEN (5%; usually bilateral and almost always intraadrenal) 2 and 3, NF, vHL, Sturge-Weber, Carney’s Triad, tuberous sclerosis

Question 6

Adrenal carcinoma

Answer 6

Rare, can be functioning (causes Cushing’s, virilisation) or non-functioning
Association with MEN 1
Bimodal peak - paediatric and 40 y/o
Generally large (>12 cm), haemorrhage is poor prognostic indicator
20-30% calcified, generally heterogeneous enhancement on CT

Question 7

Adrenal Metastasis

Answer 7

If known malignancy, 38-57% adrenal nodules are metastatic (usually lung, breast, renal, melanoma)
Frequently bilateral; generally large, heterogenous and poorly marginated
Delayed washout on CT, no drop off on chemical shift imaging
PET most accurate - uptake > liver on PET (but clear cell renal, carcinoid and bronchoalveolar may be false negative)

Question 8

Adrenal lymphoma

Answer 8

NHL most commonly, 70% bilateral

Question 9

Cushing’s Syndrome

Answer 9

70% due to adrenal hyperplasia: 90% ACTH pituitary adenoma, 10% ectopic ACTH (lung, islet cell pancreatic, ovarian)
20% adrenal adenomas (2-4 cm)
10 % adrenal cortical carcinoma (but only 10% of these cause Cushing’s)

Nonspecific adrenal hyperplasia - acromegaly (100%), hyperthyroidism (40%), HTN (15%)

Question 10

Conn’s Syndrome

Answer 10

Due to aldosterone excess; F > M, usually 40 y/o
HTN, hypokalaemia, polyuria, hypernatraemia
Primary (Conn’s disease)

75% due to aldosterone-secreting adenoma (small, low attenuation, eccentric);

25% adrenal cortical hyperplasia
Secondary: RAS, reninoma

Question 11

Causes of adrenal failure

Answer 11

Primary (cortical destruction = Addison's):
Autoimmune
Infection (fungal, TB; enlarges if acute and calcifies if chronic)
Drug-induced
Bilateral adrenal haemorrhage
Metastasis
Sarcoidosis
Haemochromatosis
Amyloidosis

Secondary (due to inadequate pituitary stimulation)

Question 12

Adrenal infections

Answer 12

TB (calcification ± soft tissue mass ± necrosis)
Histoplasmosis
Meningococcus
Echinococcus

Question 13

MEN and Carney’s Triad

Answer 13

All autosomal dominant
MEN 1: adrenal cortical nodules / functioning adenoma, PTH hyperplasia / adenoma, pancreatic islet cell tumour, pituitary adenoma, carcinoid tumour ± multiple lipomas ± thyroid nodules
MEN 2A: Phaeochromcytomas (more frequently extra-adrenal), medullary thyroid carcinoma, PTH hyperplasia / adenoma
MEN 2B: Phaeochromcytomas (more frequently extra-adrenal), medullary thyroid carcinoma, soft tissue neuromas, ganglioneuromatosis of small intestine, Marfanoid habitus
Carney’s triad: Gastric leimyogenic neoplasms, extra-adrenal phaeochromocytomas / paragangliomas, pulmonary chondromas

Question 14

Adrenal collision tumour

Answer 14

Co-existing histologically different (benign and malignant) tumours in same gland