
When “Appendicitis” Is Endometriosis in Disguise
Right-sided “appendicitis” pain dismissed again? It may be endometriosis of the appendix—what it feels like, why tests miss it, and what to do next.
If your right-sided pain keeps getting dismissed... you’re not imagining it
Right-lower-abdominal pain (the classic “appendicitis area”) can be terrifying—especially when it comes on suddenly, sends you to urgent care or an emergency department, or shows something alarming on a CT scan. If you live with endometriosis or adenomyosis, that fear can be mixed with frustration: “Is this just my usual pain, or is something actually wrong?”
Here’s an important—and practical—truth: endometriosis can grow on the appendix and can look exactly like acute appendicitis or even an appendiceal mass on imaging. A recent case report in Cureus highlights how easily this can be missed, and why you deserve a care team that keeps endometriosis on the table as a possibility.
What “appendix endometriosis” can feel like in real life
When endometriosis affects the appendix, your symptoms may overlap with common GI and appendix problems. Some people describe:
- Sharp or cramping pain in the right lower abdomen
- Pain that flares with your period (or began that way and later became more constant)
- Nausea, bloating, bowel changes, or pain with bowel movements
- Pain that doesn’t fit neatly into “GI” or “gynecologic” boxes
In the case described, the person’s right-sided pain started with menses and then became persistent, which is a pattern many patients recognize: cyclical pain that gradually becomes more frequent or continuous.
Why scans and bloodwork can still miss it
One of the most frustrating parts: imaging often can’t reliably tell appendiceal endometriosis apart from appendicitis or even a tumor.
In the case report, a CT scan showed an enlarged right-lower-quadrant structure that looked suspicious for acute appendicitis, and there was also concern about a possible malignant appendiceal mass. That is a common nightmare scenario for patients—being told, “We’re worried this could be cancer,” and then waiting for answers.
The key patient-centered point is this: there may be no distinctive radiology features that scream “this is endometriosis.” Even if you’ve already been diagnosed with endometriosis elsewhere, the appendix may not be the first thing clinicians think about.
Blood tests don’t necessarily clear things up either. In this report, CA-125 was elevated, but CA-125 is nonspecific—it can rise for many reasons (including endometriosis or any inflammatory process), and it cannot confirm what an appendiceal mass is.
How the diagnosis is actually confirmed
If imaging can’t reliably distinguish appendiceal endometriosis, what can?
Pathology. In the case report, the definitive answer came only after surgery, when the appendix tissue was examined: the pathology showed a 2.8 cm endometriotic mass involving the appendix wall, and importantly, it was negative for dysplasia and malignancy.
This matters for your decision-making because it explains why some situations move quickly to surgery: when imaging suggests appendicitis, a complicated infection, or a mass that could be malignant, clinicians often can’t “watch and wait” safely.
If this happens to you, it’s not “just random”—it can be a clue
A big takeaway from this case is that appendiceal endometriosis may be a sign of more widespread disease, especially if you have symptoms beyond the appendix area. If not suspected, the surgeons operating for what they think is appendicitis may not even look in the pelvis and certainly not the deep pelvis.
After the appendiceal surgery, pelvic MRI in this patient showed multiple other issues that commonly travel together:
- Adenomyosis
- Uterine fibroids (leiomyomas)
- An ovarian endometrioma (a cyst associated with endometriosis)
If you’ve had unexplained right-sided abdominal pain plus heavy bleeding, cramping, deep pelvic aching, painful sex, infertility concerns, or bladder/bowel pain—this combination can be a signal to step back and reassess the whole picture, not just the appendix.
Could It Be Appendix Endometriosis?
Our specialists are here to help you understand your condition and explore your treatment options.
Schedule Your EvaluationWhat treatment typically looks like (and what “success” may mean)
For appendiceal endometriosis that presents like appendicitis or a concerning mass, treatment often ends up being surgical removal of the appendix (appendectomy), because:
- it treats the immediate problem (appendicitis-like symptoms or mass concern)
- it provides tissue for diagnosis (pathology)
- it can remove a pain generator
In the case report, surgical exploration and histology were consistent with advanced (stage IV) endometriosis, and the patient later reported resolution of pain after subsequent surgery.
A reality check that protects you: this is one person’s experience. It doesn’t guarantee that surgery will fully resolve pain for everyone, and it doesn’t tell us how long relief lasted. But it does support something many patients already learn the hard way—when endometriosis is outside the uterus/ovaries, it can drive symptoms that won’t be fixed by “IBS treatment” alone.
Practical takeaways you can use immediately
If you have right-lower-quadrant pain (especially if it’s cyclical, recurrent, or unexplained), you’re not being dramatic to ask whether endometriosis could be involved—even if the pain feels “too high” or “too GI” to be pelvic.
Bring these questions to your clinician (ER, primary care, GI, or gynecologist—whoever is in front of you):
- “Could this be appendiceal or bowel-related endometriosis, especially since my pain is cyclical or I have known endometriosis/adenomyosis?”
- “If the CT shows an appendiceal mass, what diagnoses are you considering besides cancer and appendicitis?”
- “What is the plan to confirm the diagnosis—will pathology be done if surgery happens?”
- “If my appendix is removed, do I need follow-up with an endometriosis-experienced gynecologist to look for additional disease?”
- “If I still have pelvic pain afterward, what’s the next step—pelvic MRI, referral to an endometriosis specialist, or both?”
Red flags: when you should seek urgent care
Right-lower-quadrant pain can still be true appendicitis or other urgent conditions. Don’t self-diagnose. Seek urgent care if you have worsening localized pain, fever, vomiting, fainting, rigid abdomen, or pain that escalates quickly—especially if clinicians are worried about appendicitis or a complicated infection. A possible differentiating symptom is that in classic acute appendicitis periumbilical pain and nausea can acutely precede right lower quadrant pain.
Reality check: what we still don’t know (and why your case may differ)
This evidence comes from a single case report, which is useful for recognizing patterns but can’t tell you how common appendiceal endometriosis is, who is most at risk, or whether surgery is always the “best” option.
It also highlights a frustrating truth: even good imaging may not give a clear answer. Sometimes the only way to know what’s happening is through surgery and pathology—particularly when there’s concern for malignancy or complicated appendicitis.
What you can do is make sure your symptoms are interpreted in context: your menstrual cycle pattern, your endometriosis/adenomyosis history, and whether you have other pelvic pain features that suggest a broader endometriosis picture.
References
Ha J, Hamid F, Ahn J, Afuape N, Azhar E. The Great Mimicker: Extragonadal Endometriosis Presenting as an Appendiceal Mass and Acute Appendicitis. Cureus. 2025 Jul 25;17(7):e88718. doi: 10.7759/cureus.88718. PMID: 40861586; PMCID: PMC12375226.
Quick Answers
How is multi-organ endometriosis treated without organ removal?
In many multi-organ cases, the goal is conservative surgery: removing endometriosis while preserving the organs themselves. That typically means meticulous excision of disease from surfaces and deeper planes around the bowel, bladder, ureters, ovaries, and pelvic sidewalls—freeing organs from scar tissue and restoring normal anatomy without taking the organ out. Because endometriosis can hide in distorted or “frozen” anatomy, the safest way to preserve organs is often a highly precise approach that can dissect around vital structures.
In our practice, we use robotic excision to improve visualization and fine-control dissection, which is especially helpful when disease involves multiple compartments or has been operated on before. When endometriosis is close to structures like the ureters, bowel, diaphragm, or certain nerves, treatment planning may include coordinated work with other surgical specialists so the disease can be fully addressed in one operation while still prioritizing organ-sparing techniques.
Organ removal is usually considered only when an organ is severely damaged, there are multiple large endometriomas that can’t be safely managed with tissue-sparing techniques, fertility-safety concerns arise (like a badly damaged tube), or there’s concern for tumor or malignant change. If you’re trying to avoid organ removal, we can help map likely disease sites, clarify your priorities (pain relief, function, fertility), and outline what organ-preserving excision could realistically look like in your specific case—then build a surgical plan around that.
Why do I have painful urination and pelvic cramping between periods?
Painful urination with pelvic cramping between periods can happen when the bladder, ureters, uterus, pelvic floor, or nerves are being irritated—sometimes in a way that still follows a subtle cycle pattern even if you’re not actively bleeding. Endometriosis can contribute by affecting the bladder wall or tissues around the bladder and ureters, and symptoms don’t have to include visible blood in the urine. Importantly, urinary tract endometriosis isn’t always “obviously urinary,” and ureter involvement can be quiet while still significant, which is why we take these symptoms seriously.
These symptoms can also come from conditions that overlap with (or mimic) endometriosis, such as bladder pain syndrome/interstitial cystitis, pelvic floor overactivity, adenomyosis-related uterine cramping, or other pelvic pain drivers. In our evaluation process, we focus on your full flare pattern—what triggers it, how it relates to your cycle, and whether urine tests have been repeatedly negative—then use targeted exam and the right imaging (often expertly interpreted ultrasound and/or MRI) to map what’s actually going on.
If you’re noticing recurring burning with urination, pressure, cramping, or symptoms that predictably flare mid-cycle or before your period, that pattern is useful diagnostic information—not something to dismiss. You can explore our urinary symptom and diagnostic evaluation resources to see how we approach “UTI-like” symptoms with negative cultures, and you’re welcome to reach out to schedule a consultation so our team can help you sort out whether this is bladder/ureter endometriosis, a look-alike condition, or a combination.
Why do I look pregnant from bloating with constant pelvic pressure?
Feeling so bloated you “look pregnant” along with constant pelvic pressure usually points to more than simple gas—often it’s a pelvic condition creating inflammation, swelling, or a sense of bulk. Endometriosis can irritate the bowel and pelvic lining, trigger scarring that tethers organs, and create the classic “endo belly” sensation that comes and goes (sometimes not perfectly cyclical). Pelvic pressure can also happen when endometriosis involves deeper tissues or nearby organs like the bladder, ureters, or rectum.
Just as important: these symptoms can be driven by endometriosis neighbors or coexisting conditions, especially adenomyosis and fibroids, which can make the uterus feel heavy, full, or “bulky” and add pressure on the bladder and bowel. Ovarian cysts and other benign pelvic findings can contribute, and IBS-like bowel sensitivity can overlap so closely that symptoms alone don’t reliably sort out what’s causing what. Our team focuses on mapping the full picture—uterus, ovaries, bowel, bladder, and pelvic support structures—so treatment targets the true driver(s), not just the most obvious diagnosis.
If this pressure/bloating is persistent, worsening, or changing your ability to eat, move your bowels, or urinate comfortably, it’s a strong reason to pursue a deeper evaluation rather than being told it’s “normal.” You can explore our educational content on bowel symptoms, bladder symptoms, and overlapping conditions, and reach out to schedule a consultation so we can review your history, imaging, and symptom pattern and outline a plan aimed at lasting relief.
Why do I get low back and leg pain during my period?
Low back and leg pain that predictably flares with your period can happen when pelvic inflammation irritates pain pathways that “refer” into the back, hips, buttocks, and down the leg. In some patients, endometriosis can be part of that story—either indirectly (pelvic inflammation and scarring increasing pressure and sensitivity around nearby nerves) or more directly if disease is affecting areas close to major nerves.
When period-related leg pain resembles sciatica—deep buttock pain, tingling, burning, or pain radiating down the back of the thigh—it raises the possibility of endometriosis-related sciatic irritation or pelvic floor involvement (often described as piriformis-type pressure on the nerve). These symptoms may start before bleeding, peak during the period, and linger afterward, and in more significant cases can be associated with weakness or changes in walking.
Because back and leg pain can also come from the spine, hips, or muscles, the key is the pattern and the full symptom “constellation,” including pelvic pain, bowel/bladder symptoms, or pain with sex. Our team can help you sort out whether your pain fits an endometriosis/adenomyosis pattern and, if needed, plan next-step evaluation such as targeted imaging and a strategy focused on lasting relief rather than temporary suppression.
Can endometriosis cause infertility and pelvic pain in your 20s?
Yes. Endometriosis can absolutely show up in your late 20s and it can be a driver of both chronic pelvic pain and fertility challenges. Pain can include severe or worsening period cramps, pain with sex, bowel or bladder pain, and “flare” patterns that track with your cycle—although symptom severity doesn’t always match how much disease is present.
Endometriosis can affect fertility in several ways, including adhesions that distort tubo‑ovarian anatomy, inflammation and immune signaling that interferes with fertilization or embryo development, and ovarian factors—especially when endometriomas are involved. For some patients, the uterine environment also matters, particularly when adenomyosis is present alongside endometriosis. In our practice, we focus on listening to your full symptom and fertility story and then building an evaluation that looks for endometriosis while also checking for common look‑alikes or coexisting issues, so we can tailor a plan to your goals—whether that’s pain relief, preserving fertility, or both.


