The adrenal glands are small, triangular-shaped structures situated atop each kidney, playing a profound role in maintaining bodily balance. These endocrine glands produce hormones, including cortisol, which manages metabolism and the body’s stress response, and adrenaline, central to the “fight-or-flight” mechanism. A cyst is a closed, sac-like pocket of tissue that can form anywhere in the body and is often filled with fluid. Adrenal cysts are a relatively rare finding, with incidence rates reported to be less than 1% in the general population, though they are increasingly recognized due to modern imaging technology.
What Exactly Are Adrenal Cysts?
An adrenal cyst is a fluid-filled sac that develops within the tissue of the adrenal gland. Unlike solid adrenal masses, these lesions are characterized by their liquid contents and typically have a thin wall. The size of these cysts can vary considerably, ranging from just a few millimeters to massive lesions over 20 centimeters in diameter.
The majority of adrenal cysts, estimated at over 90%, are benign, meaning they are non-cancerous. Most cysts are also considered non-functional, meaning they do not produce excess hormones that would disrupt the body’s endocrine system. The distinction between a purely cystic, benign lesion and a solid or hormonally active tumor is a primary focus during the diagnostic process.
Understanding the Different Types and Origins
Adrenal cysts are classified into four main categories based on their origin and the composition of their walls. Endothelial cysts and pseudocysts represent the two most common types, while epithelial and parasitic cysts occur much less frequently.
Endothelial Cysts
Endothelial cysts, also known as true cysts, are often the most common type found in autopsy studies, accounting for nearly half of all cases. They possess a distinct inner lining of endothelial cells, often arising from dilated blood or lymphatic vessels, known as lymphangiomas or hemangiomas. They are generally thin-walled and filled with clear or serous fluid.
Pseudocysts
Pseudocysts are the most frequent type encountered in surgical practice. Unlike true cysts, pseudocysts lack a cellular lining and are instead surrounded by a fibrous wall. Their formation is commonly attributed to a prior hemorrhage or bleeding event within the adrenal gland, possibly triggered by trauma or infection.
Other Types
Epithelial cysts, which are very rare, possess a lining of epithelial cells and may be associated with polycystic diseases. Parasitic cysts are extremely uncommon in developed nations but are typically caused by the larval stage of the tapeworm Echinococcus granulosus, leading to a hydatid cyst.
How Adrenal Cysts Are Detected
Most adrenal cysts are discovered entirely by chance when a patient undergoes abdominal imaging for an unrelated health concern. These accidentally found masses are referred to as “adrenal incidentalomas” and represent the most common pathway to diagnosis. Small cysts usually do not produce any symptoms, allowing them to remain undetected.
When symptoms do occur, they are typically caused by a larger cyst pressing on nearby organs or structures, a phenomenon known as mass effect. Patients may experience vague symptoms such as flank or back pain, a feeling of abdominal fullness, or general discomfort. In rare cases, a sudden hemorrhage into the cyst can cause acute, severe pain.
Diagnostic Imaging
Diagnostic imaging, using Computed Tomography (CT) scans and Magnetic Resonance Imaging (MRI), is used to characterize the mass. A simple, benign cyst typically appears as a homogeneous, fluid-filled structure with a thin, smooth wall and no internal enhancement after a contrast agent is administered. Imaging is particularly important to rule out solid components, which would raise suspicion for a malignant tumor that has undergone cystic change.
Biochemical Workup
A biochemical workup is a standard part of the diagnostic process for any adrenal mass. This involves blood and urine tests to measure hormone levels, such as cortisol, aldosterone, and catecholamines. This testing confirms that the cyst is non-functional and is not causing hormonal overproduction.
Management and Treatment Options
For the majority of small, asymptomatic adrenal cysts that exhibit clear benign features on imaging, the standard management approach is watchful waiting. This involves regular monitoring, typically with repeat imaging scans and hormonal testing to ensure the cyst does not grow significantly or become hormonally active.
Intervention is usually considered when the cyst is large, generally exceeding 5 to 6 centimeters in diameter, or if it is causing persistent symptoms like pain. Treatment is also indicated if imaging suggests suspicious features, such as thick walls, solid components, or if the biochemical workup reveals hormonal overproduction.
Surgical Excision
Surgical excision is the definitive treatment for symptomatic or suspicious cysts. This procedure is often performed using minimally invasive techniques, such as laparoscopic adrenalectomy, which involves small incisions and a quicker recovery time. The surgeon may perform a simple enucleation to remove only the cyst or a total adrenalectomy, which removes the entire adrenal gland, depending on the cyst’s size and involvement with the surrounding tissue.
Percutaneous Aspiration
A less common, temporary option is percutaneous aspiration, where a needle is used to drain the fluid from the cyst. While this can provide immediate relief for symptomatic cysts, it is often not a lasting solution because the fluid reaccumulates in a significant percentage of cases. Aspiration is rarely used as a primary long-term solution.