Adrenal and other endocrine surgical disorders

Overview

The adrenal gland has an outer cortex (steroid hormones) and an inner medulla (catecholamines). Surgical disease is usually a tumour that over-secretes a hormone or an incidental mass seen on a scan.

This chapter also covers the "other endocrine" topics in the same TOS line: pancreatic neuroendocrine tumours (insulinoma, gastrinoma), carcinoid and the MEN syndromes. Expect one MCQ.

Surgical anatomy

• Both glands sit on the upper poles of the kidneys inside Gerota's fascia.
• Right adrenal: behind the IVC and under the liver. Its short right adrenal vein drains straight into the IVC, which makes right adrenalectomy riskier.
• Left adrenal: near the upper pole of the kidney and the renal pedicle, under the tail of the pancreas and the spleen. The left adrenal vein drains into the left renal vein.
• Arteries come from three sources: the inferior phrenic, the aorta and the renal artery.

Adrenal incidentaloma

• An adrenal mass found by chance on a scan done for another reason. Seen in about 1% of scans, more with age.
• More than three-quarters are non-functioning adenomas. Others: Cushing's adenoma, phaeochromocytoma, metastasis, carcinoma, Conn's adenoma.

Work-up of every incidentaloma:

1. Is it secreting? Overnight dexamethasone suppression test or urinary cortisol; urinary or plasma metanephrines; potassium with aldosterone and renin (if hypertensive).
2. Could it be malignant? Size and CT appearance. A low-density (fat-rich) lesion is an adenoma; a large, irregular, heterogeneous one suggests carcinoma.

Management:

• Functioning tumour: remove (after proper preparation).
• Non-functioning, over 4 cm, or growing: remove (risk of carcinoma rises with size).
• Non-functioning under 4 cm: repeat imaging and hormones over the next 2 years; stop if stable.

Primary hyperaldosteronism (Conn's syndrome)

• Hypertension with suppressed renin; often (not always) hypokalaemia and metabolic alkalosis. Many patients have a normal potassium.
• Causes: adrenal adenoma (classic Conn's, usually 1-2 cm) or bilateral adrenal hyperplasia.
• Screening test: plasma aldosterone to renin ratio (stop interfering drugs first). Then confirm and do CT/MRI.
• Adrenal vein sampling shows which side is secreting when imaging is unclear (often not needed in patients under 40 with a clear one-sided adenoma).

Blood pressure still stays raised in some patients after adrenalectomy, though it becomes easier to control.

Cushing's syndrome

• Features: moon face, plethora, buffalo hump, central obesity, purple striae, thin skin and bruising, proximal weakness, hypertension, diabetes, osteoporosis.
• Tests: loss of normal day-night cortisol rhythm (raised midnight cortisol), failure to suppress after dexamethasone, raised 24-hour urinary cortisol. Then ACTH level separates dependent from independent.
• Low ACTH: CT/MRI of the adrenals. High ACTH: MRI pituitary, then petrosal sinus sampling or chest/abdomen CT for an ectopic source.

Treatment:

• Pituitary adenoma: trans-sphenoidal surgery.
• Adrenal adenoma: adrenalectomy.
• Severe disease or unfit for surgery: metyrapone or ketoconazole (block steroid synthesis).
• Bilateral adrenalectomy when other treatment fails; this can lead to Nelson's syndrome (enlarging pituitary tumour, high ACTH, skin pigmentation).

Patients with Cushing's need thromboprophylaxis and antibiotic prophylaxis because of high infection and clot risk.

Adrenocortical carcinoma

• Rare, aggressive; often large (over 5-6 cm), with necrosis and haemorrhage.
• About 60% secrete cortisol. Tumours that make several hormones or sex steroids (virilisation or feminisation) are likely malignant.
• Treatment: open radical resection; mitotane for advanced disease. Prognosis poor at later stages.

Adrenal insufficiency (Addison's disease)

• Signs appear only once about 90% of the cortex is destroyed. Causes: autoimmune (commonest in developed countries), tuberculosis (important in Pakistan), metastases, bleeding (Waterhouse-Friderichsen in meningococcal sepsis).
• Chronic: tiredness, weight loss, pigmentation (skin creases, buccal mucosa), low BP, low sodium, high potassium, low glucose.
• Test: short Synacthen (ACTH stimulation) test: cortisol fails to rise.
• Addisonian crisis: shock, vomiting, abdominal pain and fever, which can mimic an acute abdomen. Do not wait for results: give IV hydrocortisone 100 mg 6-hourly and large volumes of IV saline.
• Long-term: oral hydrocortisone and fludrocortisone; double the dose when ill (sick-day rules) and give steroid cover for surgery.

Congenital adrenal hyperplasia

• Autosomal recessive; 21-hydroxylase deficiency in about 95%.
• Low cortisol leads to high ACTH and excess androgens: ambiguous genitalia in girls, salt-wasting crisis in newborn boys, early puberty.
• Treat with hydrocortisone and fludrocortisone.

Phaeochromocytoma

• Catecholamine-secreting tumour of the adrenal medulla (chromaffin cells). Outside the adrenal it is called a paraganglioma (e.g. organ of Zuckerkandl, carotid body).
• Classic "10% tumour": about 10% each are bilateral, extra-adrenal, malignant, familial and in children. Genetic testing now shows more are inherited than this rule suggests, so offer it, especially under 50.
• Familial associations: MEN 2A and 2B (RET), von Hippel-Lindau, neurofibromatosis type 1, SDH gene paraganglioma syndromes.

Features

• Headache, palpitations and sweating (classic triad), episodic or sustained hypertension, pallor, anxiety, weight loss, high glucose.
• Attacks can be set off by anaesthetic induction, abdominal pressure, contrast, metoclopramide, tricyclics, opiates.
• In pregnancy, an unrecognised phaeochromocytoma carries a very high maternal death rate.

Diagnosis

1. Biochemistry first: plasma metanephrines or 24-hour urinary metanephrines (catecholamine breakdown products). Repeat at least twice.
2. Localise: CT or MRI (bright on T2).
3. MIBG scan (iodine-123 metaiodobenzylguanidine) or PET finds extra-adrenal, multiple and metastatic tumours.

Preoperative preparation

• Alpha-blockade first: phenoxybenzamine (non-selective, irreversible), increased step by step until the patient has mild postural hypotension. Doxazosin is an alternative.
• Allow volume expansion (salt and fluids) because the patient is chronically vasoconstricted and hypovolaemic.
• Beta-blocker only after alpha-blockade, for tachycardia.

Surgery and after

• Laparoscopic adrenalectomy is standard; open approach for very large (over about 8-10 cm) or suspected malignant tumours.
• Ligate the adrenal vein early to reduce catecholamine release; expect a sudden fall in BP once the vein is tied.
• Postoperatively, watch in HDU for hypotension (needs fluids, sometimes noradrenaline) and hypoglycaemia (rebound insulin).
• Lifelong yearly metanephrine testing for recurrence.

Neuroblastoma (children)

• Malignant tumour of neural crest cells of the sympathetic chain; about a third arise in the adrenal medulla.
• Usually under 5 years. Abdominal mass that crosses the midline, often calcified; proptosis and periorbital bruising ("raccoon eyes"), bone pain, bluish skin nodules. Most have metastases at presentation.
• Urinary VMA and HVA raised; MIBG scan for staging.
• Treatment by risk group: surgery alone for low risk; chemotherapy and surgery for higher risk.

Pancreatic neuroendocrine tumours

• Gastrinoma triangle: most gastrinomas lie in the area bounded by the cystic duct/CBD junction, the 2nd and 3rd parts of the duodenum, and the neck of the pancreas; many are in the duodenal wall.

Carcinoid (small-bowel and appendix neuroendocrine tumours)

• Common sites: appendix (often found by chance at appendicectomy) and terminal ileum.
• Carcinoid syndrome (flushing, diarrhoea, wheeze, right-sided valve disease) usually means liver metastases, because serotonin from the gut is otherwise broken down in the liver.
• Test: 24-hour urinary 5-HIAA; chromogranin A; somatostatin-receptor imaging.
• Treatment: resection; octreotide for symptoms. Appendiceal tumours under 1-2 cm at the tip are cured by appendicectomy; larger ones need right hemicolectomy.

MEN syndromes

Quick revision

• Incidentaloma: test hormones; remove if functioning, over 4 cm or growing.
• Never biopsy an adrenal mass before excluding phaeochromocytoma.
• Conn's: aldosterone/renin ratio; adenoma = adrenalectomy; hyperplasia = spironolactone.
• Cushing's disease (pituitary) is the commonest endogenous cause; steroids the commonest overall.
• Phaeochromocytoma: metanephrines, CT/MRI, MIBG; phenoxybenzamine first, then beta-blocker.
• Addisonian crisis: IV hydrocortisone and saline immediately.
• Insulinoma: Whipple's triad, 72-hour fast, raised C-peptide.
• MEN 1: 3 Ps. MEN 2: medullary thyroid cancer + phaeochromocytoma (RET).

Written by The House Job from standard references (Bailey & Love).

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