Experiencing endometriosis pain on the right side may indicate which structures are affected by the condition, and provide diagnostic clues.

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Endometriosis occurs when tissue similar to that of the uterine lining, the endometrium, grows in locations outside of the uterus. Like your endometrium, these cells respond to hormone changes in the body. They grow, bleed, and shed in alignment with your hormone cycles.

Endometriosis lesions create a chronic inflammatory reaction that causes pain and may lead to scarring or adhesions, bands of scarring between two or more organs.

If you live with endometriosis, you may experience localized pain, including on the right side of your body. But this isn’t always the case, and pain may be due to other causes.

In addition to intense pain and discomfort, symptoms of endometriosis may include:

  • irregular period bleeding
  • bleeding or spotting between periods
  • gastrointestinal challenges (constipation, diarrhea, nausea, bloating)
  • pain during or after sex
  • pain when urinating or defecating
  • fatigue

Although there’s no cure for endometriosis, treatment is available. Hormone therapy, surgery, and pain management can help reduce symptoms and improve your quality of life.

According to a 2018 case report, approximately 95% of diaphragmatic endometriosis lesions occur on the right side. This may sometimes explain pain on that side of the body.

Endometriosis cells may develop almost anywhere, causing pain specific to their location. When endometriosis affects your diaphragm, it’s known as diaphragmatic endometriosis.

Your diaphragm is the large muscle separating your abdominal cavity from your chest cavity. It’s essential to breathing, allowing air movement in and out of your lungs.

Current research suggests diaphragmatic endometriosis may be more common than previously thought, accounting for as many as 4.7% of endometriosis diagnoses.

Endometriosis that affects your diaphragm on the right side may cause right-sided pain in your abdomen, chest, or up into your shoulder.

Experiencing endometriosis pain only on the right side of your body doesn’t necessarily mean you’re living with diaphragmatic endometriosis, however. This is just one possible explanation for endometriosis pain on that side of the body.

Endometriosis typically causes pain and symptoms specific to its location. This means lesions on your bladder, for example, could cause central pelvic pain or discomfort when urinating.

Most people develop endometriosis in areas within the pelvis. Common sites include:

In rare cases, endometriosis can develop in more distant locations, such as the lining of the abdominal wall or the chest cavity.

Some endometriosis sites, like the diaphragm, may cause referred pain, or pain that’s felt in areas away from the source. This happens due to shared nerve networks in the body transferring pain signals from one location to another.

In diaphragmatic endometriosis, the diaphragm is directly connected through the chest cavity to the neck region by a primary nerve branch called the phrenic nerve. This is why otherwise unexplained shoulder pain is sometimes a symptom of diaphragmatic endometriosis.

Feeling pain on the right side of the body isn’t limited to endometriosis. Pain occurs whenever specialized nerve endings in your body respond to stimuli like pressure, irritation, or disease processes.

Endometriosis is just one possible cause of pain on the right side of your body. Many other conditions can cause similar sensory experiences, including:

Currently, exploratory surgery is the only way to confirm endometriosis, though advancements in nonsurgical detection options are in development.

If you believe you’re experiencing endometriosis pain on the right side only, speaking with your healthcare professional may be the first step to ruling out other possible explanations.

Understanding more about endometriosis and right-sided pain can help you discuss this symptom with your doctor.

Can endometriosis pain be only on one side?

It’s possible to experience endometriosis pain on only one side. Endometriosis typically causes pain relative to its location, meaning right-sided lesions can cause pain on the right side only, and left-sided lesions may cause only left-sided pain.

Experiencing pain on one side of the body in endometriosis does not mean you only have endometriosis on one side.

Does endometriosis always cause pain?

Endometriosis can be asymptomatic, meaning it does not cause pain or noticeable symptoms. It’s also possible to have some endometrial lesions that cause pain while others do not.

How do you know if your pain is endometriosis?

Exploratory surgery can diagnose endometriosis. Your healthcare professional investigates the interior of your pelvis using laparoscopy or open surgery. Endometriosis lesions are identified and staged based on size and how many locations are affected.

What causes period pain on the right side only?

Pain on the right side that occurs explicitly during your period can be caused by endometriosis as well as other conditions affecting the reproductive system. Other possible causes of right-sided period pain include ovarian cysts, fibroids, PID, ovulation pain, adenomyosis, or cancer.

What pain mimics endometriosis?

Endometriosis can cause a variety of pain symptoms that may mimic the pain of numerous other conditions, including those unrelated to the reproductive system, like IBS.

Adenomyosis is a condition similar to endometriosis that may present with overlapping symptoms. It occurs when endometrial tissue infiltrates the deeper muscle layers of the uterus, causing pain, menstrual irregularity, and fertility challenges.

It’s possible to experience endometriosis pain on the right side only. Pain can be specific to one side of your body if lesions or scarring are also located on that side of your body.

Pain only on the right side does not mean endometriosis is only on your right side, however, and endometriosis is not the only cause of right-sided pain. Other reproductive conditions, as well as other non-gynecological conditions, can cause similar symptoms.