Adrenal Cyst

What an adrenal cyst is

The adrenal glands make cortisol, aldosterone, adrenaline and small amounts of sex hormones. A cyst is a sac with a thin wall filled with fluid or old blood. Adrenal cysts are rare compared with solid adrenal nodules such as adenomas. They are found at any age, most often between 30 and 60, and somewhat more often in women.

Types of adrenal cysts

Some adrenal tumors, including pheochromocytomas, adrenal cancers and metastases, can have cystic or bleeding areas that look like cysts. That is why every adrenal cyst is evaluated carefully.

Symptoms

Most adrenal cysts cause no symptoms. When they do, it is usually because of size or bleeding:

• a dull ache in the flank, back or upper belly
• a feeling of fullness or early satiety from pressure on nearby organs
• a lump felt in the upper abdomen (very large cysts)
• sudden severe pain if bleeding or rupture occurs

High blood pressure, sweating episodes, weight gain or other hormonal symptoms suggest that the lesion is a hormone-producing tumor rather than a simple cyst.

Causes

The exact cause of most adrenal cysts is unknown. Contributing factors include:

• bleeding in the adrenal gland, from injury, blood thinners, severe stress or infection, or bleeding into an existing tumor. See adrenal hemorrhage
• abnormal blood or lymph vessels
• parasitic infection with Echinococcus, see echinococcosis

Diagnosis

Imaging

• CT scan: shows a well-defined, low-density lesion with a thin wall. Wall calcification is common in pseudocysts.
• MRI: helpful to confirm fluid content and look for solid parts, blood products or a thick wall.
• Ultrasound: sometimes the first test to spot it.

Features that raise concern for a tumor include a thick or irregular wall, solid components that enhance with contrast, internal septations, size over about 5 to 6 cm, and growth over time.

Hormone tests

Because a cystic pheochromocytoma or other functioning tumor can look like a cyst, specialists usually check:

• plasma or urine metanephrines for pheochromocytoma
• a 1 mg overnight dexamethasone suppression test for cortisol excess
• aldosterone and renin if you have high blood pressure or low potassium

Needle aspiration of an adrenal cyst is generally avoided until pheochromocytoma has been excluded, because it can trigger a dangerous surge of adrenaline. Serology tests are used if a hydatid cyst is possible.

Treatment

Watchful waiting

Small (generally under 5 cm), simple-appearing cysts that make no hormones and cause no symptoms can be monitored with a repeat scan, typically after 6 to 12 months. Many never change.

Surgery

Removal is usually recommended when a cyst:

• causes pain or pressure symptoms
• is larger than about 5 to 6 cm
• grows on follow-up
• has bled or ruptured
• has solid parts, a thick wall or other features that could mean a tumor
• produces hormones
• is a hydatid cyst

Laparoscopic (keyhole) surgery is the standard approach. Depending on the cyst, the surgeon removes the cyst wall (cyst unroofing or excision) or the whole adrenal gland (adrenalectomy). Most people go home within 1 to 3 days. Hydatid cysts are treated with antiparasitic medicine as well as surgery.

Outlook

The outlook is excellent. The vast majority of adrenal cysts are benign, and removal is curative when needed. Only a small minority of surgically removed cystic adrenal lesions turn out to be cancerous, usually those with solid parts on imaging.

Frequently asked questions

Is an adrenal cyst cancer?

Almost never. Most adrenal cysts are benign. Rarely, a tumor such as a pheochromocytoma or adrenal cancer has cystic areas that look like a cyst. Imaging features and hormone tests help doctors decide whether a cyst is simple or needs removal.

What symptoms does an adrenal cyst cause?

Most cause no symptoms and are found by chance. Large cysts can cause a dull ache in the flank, back or belly, or a feeling of fullness. Sudden severe pain can mean bleeding into the cyst and needs urgent care.

Does an adrenal cyst need surgery?

Not usually. Small, simple, non-hormone-producing cysts are monitored. Surgery is advised for cysts that are large (over about 5 to 6 cm), growing, painful, bleeding, producing hormones, or that have solid parts on scans.

What is the difference between an adrenal cyst and an adrenal adenoma?

An adrenal cyst is a fluid-filled sac. An adrenal adenoma is a solid, benign growth of adrenal cells that sometimes produces hormones. Both are usually found by chance on scans and both need hormone testing.

Can an adrenal cyst go away on its own?

Some pseudocysts formed after bleeding can shrink as old blood is reabsorbed, but most adrenal cysts stay the same size for years. A repeat scan shows whether a cyst is stable, shrinking or growing.