Adrenal cysts are fluid-filled sacs that form on or within the adrenal glands, the small hormone-producing organs that sit on top of each kidney. They account for a small fraction of all adrenal masses, and in one imaging study of over a thousand incidentally found adrenal lesions, cysts made up roughly one percent of the total.1PubMed. The incidental adrenal mass on CT: prevalence of adrenal disease in 1,049 consecutive adrenal masses in patients with no known malignancy Most are benign and produce no symptoms, but they come in several varieties with different origins, and a small number hide something more dangerous. Understanding the differences matters because it shapes whether your doctor recommends watching, testing, or operating.
The Four Types of Adrenal Cysts
Adrenal cysts have been classified into four main categories since the mid-twentieth century, based on what their walls are made of and how they form. A widely cited breakdown from autopsy data puts the proportions at roughly 45% endothelial cysts, 39% pseudocysts, 9% epithelial cysts, and 7% parasitic cysts.2BMJ Case Reports. Cystic lesions of the adrenal gland These numbers shift depending on the population studied. In a surgical series of 41 cystic adrenal tumors, pseudocysts dominated, accounting for 32 of the 41 cases.3PubMed. Cystic adrenal neoplasms Surgical series tend to skew toward pseudocysts because those are the ones most likely to grow large enough to warrant removal.
- Endothelial cysts: These are lined with cells from blood vessels or lymphatic channels. They split into two subtypes: angiomatous (from blood vessels) and lymphangiomatous (from lymphatic vessels). Lymphangiomatous cysts, also called adrenal lymphangiomas, are benign malformations of the lymphatic system.4PubMed Central. Significant growth of adrenal lymphangioma: A case report and review of the literature
- Pseudocysts: These lack a true cellular lining. They are essentially walled-off collections of old blood or fluid, often the aftermath of bleeding into the adrenal gland.
- Epithelial cysts: These are lined with glandular tissue. They are the least common non-parasitic type and are almost always benign.
- Parasitic cysts: These are caused by infection, most commonly the tapeworm Echinococcus granulosus, and are seen primarily in regions where this parasite is common.
One pathology series of five surgically removed cystic adrenal lesions found two epithelial cysts, one endothelial cyst, one pseudocyst, and a rare case of adrenal cancer arising within a pseudocyst.5PubMed Central. Cystic adrenal lesions: A report of five cases That last finding is a reminder that even though most adrenal cysts are harmless, the occasional one conceals a malignancy, which is a key reason doctors do not simply ignore them.
What Causes Adrenal Cysts to Form
The cause depends heavily on the type. Pseudocysts, the kind most frequently encountered in surgical practice, are generally thought to result from bleeding within the adrenal gland. That hemorrhage can be triggered by physical stress, trauma, surgery, or blood-clotting disorders.6PubMed Central. A Case of Hemorrhagic Adrenal Pseudocyst Mimicking Solid Tumor After the bleeding event, the body walls off the blood collection with fibrous tissue, and over time the blood breaks down into fluid. Because the wall is fibrous rather than cellular, the lesion is technically not a true cyst, hence the “pseudo” prefix.
The origins of endothelial cysts, particularly lymphangiomas, are less clear. The leading theories include malformation of lymphatic channels during development, blockage of nearby lymphatic drainage, dilation of existing lymphatic vessels, or degeneration of a hamartoma (a benign overgrowth of normal tissue).4PubMed Central. Significant growth of adrenal lymphangioma: A case report and review of the literature In practice, these cysts are often discovered incidentally during imaging done for something else entirely, and their exact cause in any individual is rarely determined.
Parasitic cysts are caused by the larval form of Echinococcus granulosus, the parasite responsible for hydatid disease.7PubMed Central. Primary hydatid cyst of adrenal gland: Case report Hydatid cysts overwhelmingly favor the liver and lungs; the adrenal gland is rarely affected.8PubMed Central. Incidentally detected hydatid cyst of the adrenal gland: A case report When an adrenal hydatid cyst does occur, it is almost always in a person living in or originally from a region where the parasite circulates in livestock and dogs.
Symptoms and When They Appear
Most adrenal cysts produce no symptoms at all. They are typically found by accident when someone gets a CT scan or ultrasound for an unrelated reason, such as back pain, a kidney stone, or staging for cancer. These incidentally discovered adrenal masses, often called incidentalomas, are far more common than symptomatic ones.9Trauma. Giant adrenal pseudocyst in trauma patient
Symptoms tend to show up once cysts grow large. Cysts under about 10 cm are often asymptomatic, and it is the larger ones that begin to press on surrounding structures.10PubMed Central. Unusual cause of chronic abdominal pain in a 17-year-old female: a case report of an epithelial adrenal cyst When symptoms do appear, the most common complaint is a dull ache or pain in the flank, side, or abdomen. Some people feel fullness or bloating on one side, depending on which adrenal gland is involved. A cyst large enough to push on the stomach or intestines can cause nausea or a vague feeling of discomfort after eating.
Rarely, things go wrong quickly. A large pseudocyst can rupture, either spontaneously or after a blow to the abdomen or back. One case report describes a large pseudocyst that ruptured following blunt abdominal trauma, producing a massive bleed into the space behind the abdominal organs.11PubMed. Traumatic rupture of adrenal pseudocyst leading to massive hemorrhage in retroperitoneum Another report describes a young woman who arrived in hemorrhagic shock from the spontaneous rupture of a pseudocyst, requiring emergency surgery.12PubMed Central. Spontaneous rupture and hemorrhage of adrenal pseudocyst presenting with acute abdomen and shock These emergencies are uncommon but represent the most serious risk of leaving a very large cyst in place.
How Adrenal Cysts Are Diagnosed
An adrenal cyst usually first appears on a CT scan as a round or oval mass with fluid density. On imaging, a benign cyst shows a few characteristic features: it does not take up contrast dye the way a solid tumor does, its density on CT is close to that of water (roughly 5 to 15 Hounsfield units), and it has a thin wall.13Radiology Case Reports. Cystic adrenal mass revealing a pheochromocytoma in the setting of multiple endocrine neoplasia: A case report A thin wall (three millimeters or less) with no enhancing solid components and possibly some calcification in the wall strongly suggests a benign cyst.14PubMed. Cystic adrenal lesions: CT features
The picture gets murkier when the cyst has thick walls, irregular edges, or a mix of solid and fluid components. Pseudocysts that contain old blood can look alarmingly similar to solid tumors on imaging. Cystic adrenal cancers and metastases tend to be more heterogeneous and contain a larger solid portion than simple cysts.15PubMed Central. Adrenal Pseudocyst Masquerading as Adrenocortical Carcinoma This overlap is exactly why a cyst-looking mass on a scan does not automatically get a clean bill of health. The radiologist evaluates the full picture, but sometimes imaging alone cannot give a definitive answer.
Hormonal Workup
Whenever an adrenal mass is found incidentally, guidelines call for testing whether it is producing excess hormones. The adrenal glands make several classes of hormones, including cortisol, aldosterone, androgens, and catecholamines like adrenaline.16PubMed Central. The Landmark Series: Evaluation and Management of Adrenal Incidentalomas The standard screening usually involves a low-dose overnight dexamethasone suppression test (to check for subtle cortisol overproduction) and measurement of plasma metanephrines (to rule out a pheochromocytoma, a rare adrenaline-producing tumor). In people with high blood pressure or low potassium, aldosterone and renin levels are also checked.17International Archives of Urology and Complications. Hormonal Evaluation of Adrenal Tumors: What the General Practitioner Should Know
Most adrenal cysts turn out to be hormonally inactive. But the workup is essential because a cystic-looking mass occasionally turns out to be something else entirely, such as a pheochromocytoma that has undergone internal bleeding and now mimics a simple cyst on imaging.13Radiology Case Reports. Cystic adrenal mass revealing a pheochromocytoma in the setting of multiple endocrine neoplasia: A case report Skipping the hormonal tests could mean missing a functioning tumor that needs a completely different management approach.
Needle Biopsy
In some cases, doctors may consider a needle biopsy to sample the cyst fluid or wall tissue. Endoscopic ultrasound-guided fine-needle aspiration has shown high technical success rates for adrenal lesions, with reviews reporting no major complications and only rare minor bleeding events.18PubMed Central. Endoscopic ultrasound-guided fine-needle aspiration in the diagnosis of adrenal lesions However, biopsy is not routine for every adrenal cyst. It tends to be reserved for cases where the imaging is ambiguous and the results could genuinely change the treatment plan, such as distinguishing a benign cyst from a metastasis in a person with a known cancer history.
Treatment Options
Treatment depends on the cyst’s size, whether it is producing symptoms, whether it might be hormonally active, and how confident doctors are that it is benign. For small, clearly benign-looking, asymptomatic cysts, observation with periodic imaging is the standard approach. Many of these cysts stay the same size for years and never cause trouble.
When Surgery Is Recommended
Surgery comes into the picture when a cyst is large, growing, symptomatic, or suspicious for malignancy. Most guidelines use a size threshold of about 4 cm to begin considering surgical removal for adrenal incidentalomas in general, though in practice there is variation. Some guidelines set the threshold higher, and the recommended size range for laparoscopic removal spans from under 4 cm up to 12 cm depending on the source.19PubMed Central. Adrenal Incidentaloma Controversial Size Recommendations For masses that look clearly benign on imaging (a thin-walled, water-density cyst with no solid parts), many surgeons are comfortable monitoring even when the size exceeds 4 cm. But a 4-cm cutoff has been shown to capture all primary malignant adrenal tumors in at least one surgical series while avoiding unnecessary operations for benign disease.20PubMed. Revisiting adrenal mass size as an indication for adrenalectomy
The standard surgical approach for an adrenal cyst is laparoscopic adrenalectomy, which removes the entire adrenal gland along with the cyst through a few small incisions. In selected cases, adrenal-sparing surgery is possible. A series of 39 laparoscopic adrenal-sparing procedures performed over a decade included 13 patients with adrenal cysts. All the cysts turned out to be benign, and there were no major surgical complications in any of the 39 patients.21PubMed. LAPAROSCOPIC ADRENAL-SPARING SURGERY CASE SERIES: PARTIAL ADRENALECTOMY AND CYST RESECTION Sparing part of the gland can be especially valuable if the other adrenal gland is absent or compromised, since you need at least some adrenal tissue to produce essential hormones.
Percutaneous Drainage and Sclerotherapy
Not everyone with a symptomatic adrenal cyst needs a full operation. A less invasive alternative is to drain the cyst through the skin under imaging guidance, sometimes followed by injecting alcohol (ethanol) into the cavity to destroy its lining and reduce the chance of refilling. One reported case involved a man whose cyst came back nine months after laparoscopic surgery; he was then treated successfully with percutaneous aspiration and ethanol ablation, and remained symptom-free with a minimized cyst at six-month follow-up.22PubMed Central. Postsurgical large adrenal cyst recurrence: treatment by means of percutaneous alcohol ablation This approach is considered an effective alternative when patients are not good candidates for surgery or when a cyst recurs after an initial operation.
Adrenal Cysts in Children
Adrenal cysts in infants and children deserve separate mention because the range of diagnoses is different. In newborns, a cystic-looking adrenal mass is most often the result of adrenal hemorrhage during birth. Cystic tumors, particularly neuroblastoma, ganglioneuroma, and pheochromocytoma, are also possibilities in the pediatric population.23PubMed Central. Cystic adrenal lesions: focus on pediatric population (a review) The key to telling them apart is the follow-up imaging pattern: an adrenal hemorrhage typically shrinks and resolves within one to two weeks, while a tumor stays the same size or grows.
In a study of neonates with incidentally found adrenal masses, 13 were managed with observation alone. The masses completely disappeared in eight of them and shrank substantially in the other five.24PubMed Central. Clinical features and treatment options for pediatric adrenal incidentalomas: a retrospective single center study This high rate of spontaneous resolution means that watchful waiting is a reasonable strategy for neonatal adrenal cysts, provided the mass is small, confined to the adrenal gland, and shows no features that suggest cancer. The newborn’s pediatric team will typically repeat imaging at short intervals to confirm the mass is behaving like a resolving hemorrhage rather than a growing tumor.
Adrenal Cysts During Pregnancy
Pregnancy introduces unique complications for adrenal cysts because the management options narrow. Imaging with CT is avoided due to radiation exposure, follow-up timing becomes constrained by the pregnancy, and any surgical intervention carries risks for both the mother and the fetus. A case report describes a 26-year-old woman who developed sudden severe abdominal pain at 28 weeks of pregnancy from a hemorrhagic adrenal pseudocyst. Her doctors chose a conservative approach: they managed her symptoms, waited until she reached full term, and then performed a cesarean delivery and cyst surgery in the same session.25PubMed Central. Management of giant adrenal pseudocyst in pregnancy – A unique approach and review of literature This strategy avoided the risks of premature delivery and the need for a second operation later.
Cases like this are rare, and there is no standardized protocol. The approach depends on how far along the pregnancy is, how severe the symptoms are, and whether there are signs of active bleeding or rupture. In emergencies, surgery may be unavoidable regardless of gestational age.
Why Some Adrenal Cysts Mimic Cancer on Imaging
One of the more anxiety-provoking aspects of adrenal cysts is that they can look worrying on a scan even when they turn out to be harmless. Pseudocysts are the biggest offenders here. Because they form from internal bleeding, the old blood and debris inside them can create mixed densities and irregular internal patterns that resemble a solid tumor. A hemorrhagic pseudocyst may appear as what looks like a solid, enhancing mass, leading the radiologist to flag it as potentially malignant.6PubMed Central. A Case of Hemorrhagic Adrenal Pseudocyst Mimicking Solid Tumor
Pheochromocytomas, the adrenaline-producing tumors mentioned earlier, can also develop cystic changes. The thinking is that hemorrhage and fluid leakage inside the tumor lead to breakdown and liquefaction of the tissue, which then gets walled off and looks like a cyst on imaging.13Radiology Case Reports. Cystic adrenal mass revealing a pheochromocytoma in the setting of multiple endocrine neoplasia: A case report This is precisely why the hormonal workup matters even for something that looks like a straightforward cyst. If the metanephrine levels are elevated, the “cyst” might actually be a pheochromocytoma with a cystic disguise, and the surgical approach needs to be adjusted accordingly (including blood pressure management before and during the operation).
Similarly, adrenal cancers can occasionally have prominent cystic or necrotic components. These tend to be more heterogeneous than simple cysts and contain more solid tissue, but the overlap in appearance is real enough that the distinction sometimes cannot be made until the mass is removed and examined under a microscope.15PubMed Central. Adrenal Pseudocyst Masquerading as Adrenocortical Carcinoma The risk of malignancy in an adrenal cyst overall is low, but it is not zero, and the possibility is part of what drives the decision-making around whether to operate or observe.
Living With a Monitored Adrenal Cyst
If your doctor decides that your adrenal cyst does not need immediate removal, you will likely enter a monitoring schedule. For most people, this means repeat imaging at intervals, often at six months and then annually, to confirm the cyst is not growing or changing character. The hormonal workup may also be repeated, particularly in the first year or two. The goal of surveillance is to catch any change early, whether that is growth, the development of solid components, or the emergence of hormonal activity.
The emotional side of monitoring deserves mention. Being told you have a cyst on an organ you barely knew existed, and then being told to simply wait and recheck, can feel unsettling. Most adrenal cysts remain stable for years. The odds are strongly in favor of nothing happening, but the surveillance visits exist because the small chance of a clinically meaningful change justifies keeping an eye on things. If a cyst does grow or change appearance on a follow-up scan, that does not automatically mean cancer. It may simply mean the cyst has bled internally or accumulated more fluid, but it does prompt a fresh conversation about whether removal is warranted.