Chapter 120 - Adrenal Glands Flashcards
Anatomy of Adrenal Gland?
- Right gland is adhered to vena cava with capsule continous with vascular adventitia
- Arterial supply - small branches from phrenicoabdominal, renal, cranial abdominal arteries and aorta. These form plexus that branch into medulla and cortex.
- Venous - Adrenal vein. R vein –> vena cava. L vein –> L renal vein
Adrenal physiology
- Zona glomerulosa - mineralocorticoids
Zona fasciculata - glucocorticoids
Zona reticularis - Sex hormone.
Glucocorticoids
- regulates metabolism
- stimulates hepatic gluconeogenesis.
- Anti-insulin effect/insulin resistance (inhibits glucose uptake and metabolism)
- Lipolysis and fat redistribution causing pot belly
- inhibits protein synthesis and enhance protein catabolism (muscle weakness).
- increase GFR
- inhibit vasopressin
- stimulate gastric acid
- suppress immune system
Adrenal physiology
Zona glomerulosa - mineralocorticoids
Zona fasciculata - glucocorticoids
Zona reticularis - Sex hormone.
Mineralocorticoids
- Electrolyte balance
- BP homeostasis
- Renin-angiotensin –> angiotensinogen –> angiotensin 1 –> angiotensin 2 –> aldosterone –> Na resorbtion, water resorbtion, K excresion
Adrenal physiology
Zona glomerulosa - mineralocorticoids
Zona fasciculata - glucocorticoids
Zona reticularis - Sex hormone.
Sex hormone
- small amounts of androgens and estrogens produced by adrenal cortical cells. Large mounts in pathologic conditions
Adrenal physiology - medulla -
Medulla - Chromaffin Cells –> catecholamines
Dogs - 60% epi, 40% nore
Cats - 70% epi, 30% nore
- Catecholamines (Dopamine, nore, epi) regulate metabolism and stress response through adrenergic receptors
- Adrenergic receptors = Alpha 1, Alpha2, beta 1, beta 2
- Epineprine 10x more potent than nore on beta 2 receptors.
Alpha receptors - located on arteries - stimulation = constriction
B1 - located in heart - simulation increase HR and contractility
B2 located in bronchioles and skeletal muscle arteries. Stimulation dilates bronchioles and skeletal muscle vessels.
Identify Adrenal mass
- Ultrasound, CT, MRI.
Diagnosis of Adrenal mass
- Maximum size 15mm
- Loses kidney bean shape
- Asymmetric shape and size compared to contralateral
- DDx - Benign cortical adenoma, malignant (pheochromo, carcinoma, metastatic), granuloma, cyst, hyperplasia
- vascular invasion = malignant
Cook 2014 -
Identify Adrenal Mass
- Incidental massses
- If mass > 20mm on CT or ultrasound, vascular invasion, , or clinbical/lab signs suggestive of adrenal gland
Masses > 20mm likely maligment, <20mm likely benign (Cook 2014) - CT 95% accurate in detecting vascular invasion.
Diagnosis of functional tumour (Table 120.1)
Cortisol
Memorise table 120.1
Cortisol secreting tumours
- Abdominal ultrasound - tumour = 1.5 - 8cm contralateral gland <0.3cm
LDDST - Suppression = <1.5ug/dL at 4 hrs or 50% less than baseline at 4-hours or 8 hours.
- No suppression seen in adrenal-dependant hyperA
- Pituitary dependant - suppress at 4 hrs then elevate at 8hrs or may have no suppression (40% cases).
- ACTH concentration may distinguidh PDH (high) or ADH (Low)
Pheochromocytoma
- Weakness and episodic collapse
- Similar U/S appearance as cortisol-secreting tumour but no contralateral atrophy
- normal adrenal function test
- Urine creatinine:Normetaneprine ratio = specific indicator
-Creatinine to epineprhine and noreepi ratios unreliable
Inhibin - secreted by ovary, testis, and adrenals.
Serum inhibin assay - ADH and PDH –> increased inhibin. Pheo - not increased in neutered dogs - 93.6% accurate.
Perioperative management Cortisol producing tumour Complications - Immune suppression - impaired wound healing - Hypertension - Hypercoagulable --> PTE - cushings - Pancretitis
cortisol producing tumour
- Trilostante 3-4 weeks before surgery to reverse metabolic derangement
- ACTH stim at 10-14 days
- 4-6 hours post dose
- Goal - post-ACTH between 2-5 ug/dL
Perioperative management
Pulmonary Thromboembolism
Pulmonary Thromboembolism
- Noted within 72hr
- dyspenea, tachypnea, lethargy, R Sided heart failure.
- Harsh lung sounds
-Alveolar or insterstitial patter
Blood gas - hypoxwmia and hypocapnia
- Prevent with anti-coags or pre-operative trilostane, or prevent venous stasis by quick GA recovery, regular walks
Tx - Anti-coags and O2, mechanical ventilation, theophilline, or sildenafil if pulmonary hypertension noted.
Perioperative management
Hypoadrenocorticism
Glucocorticoids:
Hypoadrenocorticism
Glucocorticoids:
- Occurs in all dogs with cortisol secreting tumour removal
- Treat with dex 0.1mg/kg, transition to oral pred when dog is earing. Taper pred dose. ACTH stim to guide tx
Perioperative management
Hypoadrenocorticism
Mineralocorticoid
Mineralocorticoid
- Mild HypoN and HypoK within develops within 72 hrs and is self limiting
- If Na <135 mEq/L or K > 6.5 mEq/L then DOCP given, remeasure every 25 days. Test after 7 days. If normal then stop. If not normal, give 50% DOCP
- Bilat adrenalectomy - continue pred and DOCP indefinitely
Perioperative management
Pheochromocytoma
Pheochromocytoma
- Chronic catecholamine exposure causes generalised vasoconstriction. After adrenalectomy, decreases vascular tone.
- tumour manipulation causes surge in catecholamine concentration
- Pre-olperative alpha blocket (phenoxybenzamine) reduce mortality from 48 - 13%; 2-3 weeks 0.5mgkg q12hr), dose increase every few days until signs of hypotension or drug reation, or 2.5mg/kg q12hr reached.
- Persistent tachycardia - treat with beta-adrenergic antaganist (propranolol or atenelol preop ONLY after alpha blocker commenced)
- Pathologic ventricular rhytn - treat with lidocaine.
- Hyhpotension - treatment vasodilatorsie nitroprusside
Surgical approaches
a) standard midline approach
B - Flank approach - unilateral only. 12th intercostal for RIGHT adrenalectomy superior exposure to paracostal approach (Andrade 2014, vet surg)
C - Laparascopic
Midline approach
- Caval invasion - 11-16% cortical tumours, 35-55% pheochromocytoma. More commonly R sided, 20% left sided.
- Intraoperative hypothermic in preparation for temporary occlusion of venacava - Esopaheal temp of 32 before vascular occlusion.
- cross match blood.
- thrombi enter phrenicoabdominal vein then to cava
- Suprarenal cava occlusion decreases CO by 60% leading to death. Gradual occlusion may allow collaterals to form
