What Is the Adnexa? Anatomy, Function, and Medical Significance

Adnexa is a medical term borrowed from Latin meaning “attached parts,” and it refers to the accessory structures that sit alongside a primary organ. In clinical practice, the word appears most often in gynecology, where the uterine adnexa includes the ovaries, fallopian tubes, and their supporting ligaments. But it also shows up in ophthalmology and dermatology, where it describes an entirely different set of structures. The reason a single word covers such different anatomy is simple: “adnexa” is not naming a specific organ but a relationship, the smaller structures that serve a larger one.

The Uterine Adnexa

When a doctor mentions “adnexa” without further qualification, they almost always mean the structures flanking the uterus on each side. These include the ovaries, the fallopian tubes (also called oviducts or uterine tubes), and the ligaments that anchor everything in place. Each ovary is roughly the size of an almond and produces eggs as well as hormones like estrogen and progesterone. The fallopian tubes extend from the upper corners of the uterus outward toward the ovaries, ending in fringed, finger-like projections called fimbriae that sweep a released egg into the tube after ovulation.

Several ligaments hold the ovaries and tubes in position within the pelvis. The suspensory ligament of the ovary carries blood vessels to and from the ovary. The round ligaments, cardinal ligaments, and uterosacral ligaments stabilize the uterus itself. Under normal conditions, these ligaments are thin enough that they can be difficult to see on imaging, but when disease is present, such as endometriosis or a tumor, they thicken and become easier to spot on MRI.¹

What the Fallopian Tubes Actually Do

It is tempting to think of the fallopian tubes as passive hallways between the ovary and the uterus, but they play an active role in reproduction. The tube’s inner lining is lined with tiny hair-like structures called cilia that beat in coordinated waves, moving the egg toward the uterus. At the same time, muscular contractions in the tube wall help push things along. The tube also provides a specific chemical environment that supports fertilization and the earliest stages of embryo development. If the tube’s transport function is impaired, by infection, scarring, or structural damage, natural conception becomes far less likely.²

This is one reason why conditions affecting the adnexa, even when they seem minor, can have outsized consequences for fertility. A small adhesion from a past infection or a mild case of endometriosis may not cause dramatic symptoms but can quietly interfere with the tube’s ability to pick up and transport an egg.

Ectopic Pregnancy and Ovarian Torsion

Two of the most urgent adnexal emergencies are ectopic pregnancy and ovarian torsion, and both tend to show up in the emergency department as sudden, severe lower abdominal pain.

An ectopic pregnancy occurs when a fertilized egg implants outside the uterus, most often within a fallopian tube. This happens in roughly one to two percent of all pregnancies. If undetected, the growing embryo can rupture the tube, causing dangerous internal bleeding. About one in five ectopic pregnancies progresses to rupture.³ Early detection through blood tests and ultrasound often allows treatment with medication rather than surgery, but a ruptured ectopic pregnancy is a surgical emergency.

Ovarian torsion happens when an ovary twists on its supporting ligament, cutting off its own blood supply. It accounts for a small fraction of gynecologic emergencies, with an incidence of roughly two to five percent among women presenting with acute pelvic pain. A cyst or mass on the ovary increases the risk because the added weight makes the ovary more likely to rotate. Among torsion cases, dermoid cysts, a type of benign tumor that can contain tissue like hair, teeth, or fat, are found in about a quarter.³ Without timely intervention, torsion can lead to permanent damage to the ovary.

Adnexal Masses and How They Are Evaluated

An “adnexal mass” is one of the most common findings on a pelvic exam or ultrasound, and the vast majority are benign. Simple ovarian cysts, for instance, form routinely during the menstrual cycle and usually resolve on their own. The clinical challenge is distinguishing these harmless findings from the rare ovarian cancer.

Ultrasound is the first-line imaging tool. To bring consistency to how radiologists interpret what they see, the American College of Radiology developed the Ovarian-Adnexal Reporting and Data System, known as O-RADS. This system assigns each finding a score from 0 to 5, ranging from incomplete assessment up to high risk of malignancy, with a management recommendation for each category.⁴ Multiple validation studies have confirmed that O-RADS categories correlate well with actual malignancy rates, and the system produces consistent results regardless of a radiologist’s experience level.⁵

A head-to-head comparison of scoring systems found that O-RADS achieved about 95% sensitivity and 89% specificity for distinguishing benign from malignant ovarian tumors on ultrasound.⁶ A separate model called ADNEX, developed by the International Ovarian Tumor Analysis group, showed similarly strong performance, with pooled sensitivity around 91% and specificity around 84% across studies.⁷ The practical takeaway is that a skilled ultrasound exam, interpreted with a standardized scoring system, catches the overwhelming majority of cancers while sparing most women with benign findings from unnecessary surgery.

When Ultrasound Is Not Enough

If an ultrasound finding is ambiguous, an indeterminate or “can’t tell” result, MRI is the next step. MRI is better at characterizing the tissue composition of a mass, which helps determine whether it is likely benign or malignant. A meta-analysis found that MRI achieved about 94% sensitivity and 91% specificity for telling benign from malignant ovarian tumors, outperforming CT on both measures.⁸ European guidelines recommend MRI specifically for cases where ultrasound is inconclusive, while CT is reserved for staging once cancer is suspected or confirmed.⁹

MRI’s advantage is that it increases specificity, the ability to correctly identify benign masses as benign, which reduces the number of women who undergo surgery only to learn they never had cancer.¹⁰ CT, by contrast, is better suited for mapping the spread of confirmed disease to guide surgical planning.

Surgery for Adnexal Conditions

When surgery is needed for an adnexal mass, ovarian cyst, or other condition, the choice is generally between laparoscopy (small incisions with a camera) and laparotomy (a larger traditional incision). A comparative study found that laparoscopic surgery resulted in significantly less blood loss and faster recovery than open surgery for the same procedures. However, when surgeons performed a cystectomy (removing a cyst while preserving the ovary) laparoscopically, there was a higher rate of the cyst rupturing during the procedure compared to open surgery.¹¹ This trade-off matters because cyst rupture can complicate things if the cyst turns out to be cancerous, which is why surgeons are cautious about the approach when malignancy cannot be ruled out preoperatively.

For large adnexal cysts, which can sometimes grow to impressive sizes, techniques have evolved to handle them laparoscopically using specialized suction methods that allow the cyst to be drained and removed through very small incisions, reducing operative time and recovery compared to opening the abdomen.¹²

Adnexal Problems in Children and Adolescents

Adnexal conditions are not limited to adults. Ovarian torsion, while rare in children, is particularly tricky to diagnose because younger patients often cannot clearly describe their symptoms or provide a detailed medical history. Imaging becomes essential. On ultrasound, classic signs in a child include an ovary that appears larger than expected, follicles pushed to the edges of the ovary, and an ovary that has shifted to the midline of the pelvis rather than sitting in its usual position on one side.¹³

A distinctive feature in pediatric cases is that torsion can happen in a completely normal ovary, without any cyst or mass. In adult women, torsion almost always involves an underlying lesion. When a pediatric ovary does have a mass, it is benign in the overwhelming majority of cases, with the risk of malignancy falling below two percent. The surgical priority in children is preserving the ovary and future fertility, which is typically achieved by untwisting the ovary rather than removing it, sometimes along with removal of a cyst or fixation of the ovary to prevent recurrence.¹⁴ Delayed diagnosis in children can lead to loss of the ovary, so awareness that torsion can occur even in the absence of a mass is important for clinicians who evaluate pediatric abdominal pain.

The Ocular Adnexa

In ophthalmology, “adnexa” refers to the structures that surround and support the eyeball itself. These include the eyelids, the lacrimal gland (which produces tears), the extraocular muscles that move the eye, the connective tissue known as fascia, and the orbital fat that cushions the eye in its socket.¹⁵ Every time you blink, look sideways, or shed a tear, you are using your ocular adnexa.

These structures have their own set of diseases. Chronic inflammations affecting the orbit and ocular adnexa can present as masses, cysts, or abscesses. One review of 55 such cases found that the majority were granulomatous inflammations, with chalazion, a blocked eyelid gland that forms a bump, being the most common, followed by infectious causes including tuberculosis.¹⁶

Lymphoma can also develop in the ocular adnexa. The most common subtype is extranodal marginal zone B-cell lymphoma, a slow-growing cancer that tends to arise in tissue outside of lymph nodes.¹⁷ The orbit itself is the most frequently involved site, followed by the conjunctiva and lacrimal glands.¹⁸ Ocular adnexal lymphoma often looks like a painless swelling around the eye and can be mistaken for a benign condition, which is why biopsy is essential for any persistent orbital mass.

Systemic autoimmune diseases can also target the ocular adnexa. Pyoderma gangrenosum, a condition more commonly associated with skin ulcers on the legs, can occasionally affect the eyelids. When it does, it tends to respond to immunosuppressive therapy, with surgical repair of the eyelid reserved for after the inflammation has quieted.¹⁹

The Skin Adnexa

Dermatologists use “adnexa” to describe the structures embedded within the skin: hair follicles, sebaceous (oil) glands, sweat glands (both eccrine and apocrine), and nails. These are the appendages that the skin produces and maintains, and each has a specific job. Hair follicles and their associated sebaceous glands are found over most of the body surface. Sebaceous glands produce sebum, a mixture of lipids that protects the skin surface against environmental damage. Research increasingly suggests these glands do more than just lubricate: they appear to play roles in immune regulation and even energy metabolism.²⁰

Eccrine sweat glands help regulate body temperature and are distributed nearly everywhere on the skin. Apocrine sweat glands are concentrated in the armpits and groin and produce a thicker secretion that, when broken down by skin bacteria, is largely responsible for body odor. These distinctions become clinically relevant because tumors can arise from any of these adnexal structures, and the type of gland a tumor originates from helps determine its behavior and treatment.

Skin adnexal tumors are a broad family of growths that range from completely benign to malignant. They are classified by which type of normal skin structure they resemble: hair follicle tumors, sebaceous gland tumors, or sweat gland tumors.²¹ Tumors arising from apocrine or eccrine glands are particularly varied and can look unremarkable on the surface, making them easy to underestimate. Their outward appearance and even their appearance under a dermatoscope are often nonspecific, so a biopsy with specialized pathological examination is required for accurate diagnosis.²² This is one area where clinical judgment alone falls short and the microscope is genuinely indispensable.

How Skin Adnexa Differ Across Species

The skin appendages familiar to humans, hair follicles and sweat glands, are part of a broader evolutionary story. Mammals evolved hair follicles from ancestral epidermal structures that invaginated into the dermis, adopting a growth pattern from base to tip that allows continuous renewal. Birds went through a parallel process, producing feather follicles from similar developmental pathways. Both innovations serve the same fundamental purpose: maintaining a stable body temperature.²³ This shared origin explains why researchers studying skin biology often work across species. Insights into how sebaceous glands function or malfunction in domestic animals, for example, have informed understanding of similar gland diseases in humans, since the underlying biology is remarkably conserved.

Reptiles and amphibians, by contrast, have relatively few skin appendages. Their skin is generally glandular in a diffuse way rather than organized into distinct adnexal units. The rich collection of hair follicles, glands, and nails that defines mammalian skin is, in evolutionary terms, a relatively recent elaboration, one that allowed mammals to thrive in a wide range of climates by fine-tuning temperature regulation, waterproofing, and sensory input through specialized skin structures.