Ovarian cysts can become infected, though it’s not common. The most frequent pathway involves bacteria from a pelvic infection spreading to an existing cyst, turning it into what’s called an ovarian abscess. In rarer cases, a cyst can rupture and trigger a serious inflammatory reaction in the abdomen. Understanding how these situations develop, what they feel like, and what raises your risk can help you recognize a problem early.
How an Ovarian Cyst Becomes Infected
Most ovarian cysts form during the normal menstrual cycle and resolve on their own without ever becoming infected. Infection typically happens when bacteria from elsewhere in the pelvis reach the cyst. The most common route: bacteria from sexually transmitted infections like gonorrhea or chlamydia travel upward from the cervix through the uterus and into the ovaries. This is the same process behind pelvic inflammatory disease (PID), and women with PID are significantly more likely to develop infected ovarian cysts.
Bacteria can also reach a cyst through the bloodstream or through direct introduction during medical procedures. Transvaginal ultrasound-guided procedures, egg retrieval during IVF, and aspiration of existing cysts all carry a small risk of introducing bacteria directly into ovarian tissue. Once bacteria colonize a cyst, the fluid-filled space becomes an ideal environment for them to multiply, and the cyst can transform into a pus-filled abscess.
Tubo-Ovarian Abscess: The Most Serious Form
When infection involves both the ovary and the fallopian tube, the result is a tubo-ovarian abscess (TOA). This is the most dangerous form of ovarian cyst infection and requires prompt treatment. TOAs tend to form dense walls of inflamed tissue and can grow large enough to distort the normal anatomy of the pelvis.
A primary ovarian abscess, one that forms within a cyst without involving the fallopian tube, is considerably rarer. It most often develops inside an endometrioma, a type of cyst caused by endometriosis. The weakened wall of an endometriotic cyst appears to make it more vulnerable to bacterial colonization.
Who Is at Higher Risk
Several factors increase the chance that an ovarian cyst will become infected:
- Pelvic inflammatory disease, whether active or in your history, is the single biggest risk factor.
- Endometriosis, particularly advanced stages (stage III or IV), creates cysts with fragile walls that bacteria can penetrate more easily.
- Intrauterine devices (IUDs) slightly raise the risk of ascending pelvic infection, especially in the weeks after insertion.
- Recent pelvic surgery or transvaginal procedures can introduce bacteria directly into the ovary.
- Hydrosalpinx, a condition where the fallopian tube fills with fluid, and nearby bowel infections can also contribute.
Symptoms of an Infected Cyst
An uninfected ovarian cyst often causes no symptoms at all, or just mild one-sided pelvic discomfort. Infection changes the picture dramatically. Fever is the hallmark sign, often accompanied by escalating pelvic pain that doesn’t respond to over-the-counter painkillers. The pain typically concentrates on one side of the lower abdomen but can spread across the pelvis as inflammation worsens.
Your body’s immune response to the infection shows up in blood work as elevated white blood cell counts. Normal levels sit between 4,000 and 10,000 cells per cubic millimeter; infected or ruptured cysts can push that number above 20,000. C-reactive protein, a general marker of inflammation, also rises. You might notice nausea, vomiting, or a general feeling of being unwell that goes beyond typical menstrual discomfort. Vaginal discharge, particularly if it’s unusual in color or smell, can be another clue, especially when the infection originates from an STI.
What Happens if an Infected Cyst Ruptures
Rupture is the complication that turns an infected cyst into an emergency. When cyst contents spill into the abdominal cavity, they can cause peritonitis, an intense inflammation of the lining that surrounds your abdominal organs. This can happen with infected cysts or even with certain uninfected ones. Dermoid cysts (a type that contains hair, skin cells, and fatty tissue) carry a particularly notable rupture risk: one analysis found that ruptured dermoid cysts were more than nine times as likely to cause chemical peritonitis compared to other cyst types.
Signs that a cyst may have ruptured include sudden, severe abdominal pain, lightheadedness, rapid heartbeat, and feeling faint. If the ruptured cyst was infected, signs of spreading infection like high fever, chills, and worsening pain demand immediate emergency care. Peritonitis from a ruptured cyst is a surgical emergency.
How Infected Ovarian Cysts Are Treated
Treatment depends on the size of the abscess and how quickly your body responds to antibiotics. The first step is almost always intravenous antibiotics that target a broad range of bacteria, since ovarian infections often involve multiple bacterial species simultaneously. If you respond well within the first 24 to 48 hours, your care team will typically switch you to oral antibiotics to complete a full 14-day course.
When antibiotics alone aren’t enough, which is more likely with abscesses larger than about 5.5 centimeters, the next step is draining the abscess. This can be done through a needle guided by ultrasound or CT imaging, or through minimally invasive surgery. Abscesses that don’t improve within 72 hours of antibiotics generally need one of these procedures. If there are signs the abscess has ruptured, such as worsening pain or symptoms of sepsis, surgery becomes urgent.
For postmenopausal women, surgical removal is more commonly recommended even for smaller abscesses because the risk of an underlying malignancy is higher in this age group. The surgical approach varies: minimally invasive laparoscopy is preferred when feasible, but the extensive scarring and tissue distortion caused by large abscesses sometimes requires a more traditional open procedure.
Preventing Cyst Infections
Since PID is the leading pathway to ovarian cyst infection, the most effective prevention strategy is reducing your risk of pelvic infections. Consistent use of barrier contraception lowers the chance of contracting the STIs that cause PID. If you’re diagnosed with an STI, completing the full course of treatment and ensuring your partner is treated reduces the risk of bacteria spreading to the upper reproductive tract.
If you have known endometriosis or are undergoing fertility treatments that involve transvaginal procedures, being aware of the infection risk helps you catch early symptoms before they escalate. Persistent pelvic pain with fever after any gynecological procedure warrants prompt evaluation rather than a wait-and-see approach.