Bowel Endometriosis: Symptoms, Diagnosis and Surgical Options

Bowel endometriosis occurs when tissue similar to the lining of the womb (endometrium) grows on or into the wall of the intestines. It is a form of deep infiltrating endometriosis (DIE) — meaning the lesions are more than 5 mm below the peritoneal surface — and it can affect the rectum, rectovaginal septum, sigmoid colon, appendix, or (less commonly) the small intestine.

This ectopic tissue still responds to your monthly hormonal cycle. Each cycle it thickens, bleeds and triggers inflammation inside the bowel wall. Over time this creates scar tissue and nodules that can distort the anatomy, narrow the bowel lumen and cause severe, cyclical symptoms.

Bowel endometriosis is present in roughly 5–12% of women with endometriosis, and in up to a third of women with severe (stage IV) disease. The rectum and rectosigmoid junction — the section of bowel just behind the uterus — are the most common sites, because that is where the pouch of Douglas sits directly against the bowel.

The hallmark of bowel endometriosis is that symptoms are cyclical — they get significantly worse in the days before and during your period. This is the single most important clue that distinguishes it from irritable bowel syndrome, which fluctuates independently of the menstrual cycle.

Many women live with these symptoms for years before the underlying diagnosis is made. The average delay from first symptom to endometriosis diagnosis in the UK is still around 8 years, and bowel disease is often the last piece to be recognised.

• Painful bowel movements during your period (dyschezia) — often described as a knife-like or burning pain deep in the rectum.
• Deep pelvic pain that radiates to the lower back or down the legs.
• Cyclical bloating that is dramatically worse premenstrually ('endo belly').
• Alternating constipation and diarrhoea, tightly linked to your cycle.
• Rectal bleeding during your period (a red-flag symptom — always investigate).
• Pain with intercourse (dyspareunia), particularly with deep penetration.
• Nausea, reflux or feeling full quickly if the small bowel is involved.
• Fatigue and low iron from cyclical blood loss.

IBS is a diagnosis of exclusion, not an explanation. When bowel symptoms are cyclical, worse on your period, or accompanied by dyspareunia, painful periods or infertility, endometriosis must be actively ruled out — not assumed away.

A useful test: keep a 3-month symptom diary alongside your cycle. If your worst bowel days consistently cluster around days 25–5 of your cycle, that pattern alone justifies a referral to a specialist endometriosis centre. See our companion piece on the endometriosis symptoms checklist for a full self-check.

Diagnosis relies on high-quality specialist imaging, not a routine pelvic scan. A standard transvaginal ultrasound often misses bowel lesions unless the sonographer is specifically trained in deep endometriosis mapping.

The gold standard is a dedicated pelvic MRI with an endometriosis protocol, ideally reported by a radiologist who specialises in the disease. MRI can map the size and depth of nodules, whether the muscularis of the bowel wall is involved, and how much of the bowel circumference is affected — all of which decide the surgical plan.

A colonoscopy is usually normal even when significant bowel endometriosis is present, because the disease invades from the outside inward. Colonoscopy is used to exclude other bowel pathology (inflammatory bowel disease, polyps, cancer), not to diagnose endometriosis itself.

The definitive diagnosis is still histological — tissue confirmation after excision — but modern imaging is accurate enough to plan surgery confidently before the operation. Read more about the imaging pathway in our guide to MRI and scans for endometriosis.

Surgery is the only treatment that removes the disease itself, and the type of operation is chosen based on how deeply the bowel wall is involved and how much of its circumference is affected. All three techniques are usually performed laparoscopically or robotically in a specialist centre.

• Shave excision — for superficial lesions on the surface of the bowel. The nodule is peeled off the muscularis without opening the bowel. Lowest complication rate, fastest recovery.
• Disc resection — for full-thickness nodules under about 3 cm that involve less than a third of the bowel circumference. A circular 'disc' of bowel wall is removed and the defect closed, without removing a whole segment of bowel.
• Segmental (bowel) resection — for large nodules, multiple lesions, or when the bowel is significantly narrowed. A short segment of bowel is removed and the two healthy ends are rejoined (anastomosis). This is the most extensive option and carries the highest complication rate, but is sometimes the only way to fully clear the disease.

Bowel endometriosis surgery should never be a solo gynaecology procedure. In the UK it is performed in BSGE-accredited endometriosis centres by a team that always includes a gynaecologist trained in advanced excision surgery and a colorectal surgeon experienced in laparoscopic bowel resection.

The MDT also typically includes a specialist radiologist, an endometriosis nurse specialist, a pain consultant, and a fertility specialist. This matters because bowel endometriosis rarely comes alone — you may also have disease on the bladder, ureters, ovaries or diaphragm that needs treating in the same operation.

When you consult with Dr Berra, she works with a colorectal surgeon and a specialist radiologist as part of the same operating team, and your imaging is reviewed jointly before any surgery is offered.

Recovery depends heavily on which technique was used. Shave excision typically means 1–2 nights in hospital and 2–3 weeks off work. Disc resection means 2–4 nights and 3–4 weeks off. A segmental resection means 4–7 nights in hospital and 6–8 weeks before returning to a desk job, longer for physical work.

The most important risk to understand is anastomotic leak — where the join in the bowel does not heal properly. This is rare (roughly 1–3% for endometriosis resections) but is the reason a temporary stoma is sometimes recommended to divert stool away from the healing join for 8–12 weeks.

Other risks include bladder dysfunction (usually temporary), ureteric injury, small-bowel obstruction from adhesions, and recurrence of endometriosis symptoms. Long-term outcomes are good: most women report a dramatic reduction in cyclical bowel pain, and quality of life scores improve substantially in published series.

For the full post-op timeline see our companion guide on recovery after endometriosis surgery.

Bowel endometriosis is associated with lower fertility rates, but it does not mean you cannot conceive. Excision surgery in a specialist centre has been shown to improve spontaneous pregnancy rates, particularly in women under 35 with no other significant cause of infertility.

If you are planning pregnancy, this needs to be part of the consultation from day one — the timing of surgery, whether to attempt IVF first, and how long to try naturally after the operation are all individual decisions. Read more in our guide on endometriosis and fertility.