Home › Patient Guides › Women's Health
Bloating and Abdominal Swelling in Women: When to Investigate
Bloating after a big meal, or in the days before your period, is part of normal life. Bloating that is there most days, has lasted weeks, or means your usual clothes no longer fit is different — it deserves an answer, not another elimination diet. Here is how to tell the two apart, what actually causes persistent bloating, and what a pelvic ultrasound can (and cannot) tell you.
When bloating needs urgent care, not a booked scan
- Severe abdominal pain with vomiting, or being unable to pass wind or stool — go to A&E; this can be a bowel obstruction.
- Rapid swelling over days with breathlessness or feeling very unwell — seek same-day medical review.
- Bloating with any bleeding after menopause — the bleeding has its own strict rule: it always gets checked, promptly.
Normal bloating — and the pattern that needs a look
Bloating that comes and goes is rarely sinister: worse after meals, worse by evening, tracking the days before a period, settled by morning. The pattern that changes the advice is persistence. UK guidance is specific about it: bloating or a swollen tummy that happens persistently or frequently — most days, or more than 12 times a month — particularly in women over 50, should be assessed by a GP rather than managed with diet changes alone, because persistent bloating is one of the recognised symptoms of ovarian disease that deserves ruling out. In practice that assessment usually means an examination, a CA-125 blood test, and a pelvic ultrasound.
Other features that move bloating from "wait and see" to "get checked": feeling full very quickly when eating, a swelling that feels more one-sided than general, unintentional weight loss alongside a growing tummy, new urinary urgency, or bloating that is new and continuous after the menopause rather than cyclical.
What usually causes persistent bloating?
An honest ranking, because it shapes what to expect from investigation:
- The bowel — the most common culprit by far. Irritable bowel syndrome, constipation, gut gas and food intolerances produce exactly the "swollen by evening" pattern most women describe. Ultrasound cannot diagnose these — but it does the essential job of ruling out the structural causes first.
- Hormonal and cyclical changes. Fluid retention and gut sensitivity in the second half of the cycle make cyclical bloating extremely common in younger women.
- Gynaecological structural causes. A large ovarian cyst or bulky fibroids can physically take up space and press on the bowel — these the scan sees very well.
- Rarely, fluid in the abdomen (ascites) or a complex ovarian mass. Uncommon — and precisely the findings the scan exists to catch early.
The trouser test, the three-to-six-month wait, and the elephant in the room
Women almost never book a scan on day one of feeling bloated. In Daniela's experience they try to fix it themselves first — cutting out gluten, dropping dairy, taking probiotics — and by the time they reach the clinic they have typically been bloated for three to six months. The trigger that finally brings them in is usually the "trouser test": they can no longer button their normal jeans, or they feel they look "six months pregnant" by the end of the day, despite not gaining weight anywhere else.
The results are largely reassuring. Around 80 to 85 per cent of pelvic scans for bloating show completely normal pelvic anatomy or simple, harmless physiological cysts — in these cases the bloating is usually gastrointestinal, such as IBS, or dietary. The 15 to 20 per cent that need follow-up usually reveal large ovarian cysts, bulky fibroids physically pressing on the bowel, or — much more rarely — complex masses or fluid in the pelvis (ascites).
And the fear nobody says out loud gets addressed first. Daniela does not wait for patients to raise what they have already read online:
"I know you've been Googling your symptoms, and I know the internet immediately screams 'ovarian cancer'. It is completely understandable that you are anxious. Today, my primary job is to look very closely at your ovaries to rule that out for you. The vast majority of bloating is driven by the bowel, like IBS, or hormonal shifts, not a tumour. Let's look together and put your mind at ease."
Two distinct groups present with bloating. Women in their 20s and 30s, where it is distinctly cyclical — worse in the second half of the cycle — or linked to endometriosis; and post-menopausal women, where the bloating is usually continuous rather than cyclical. The second group is the one the clinic monitors most vigilantly for ovarian pathology.
These are general patterns and figures from our clinic's caseload, shared by Daniela Stan, Consultant Ultrasound Practitioner. They describe practice as a whole, not any individual patient, and they are not a prediction of your result or a substitute for individual medical advice.
What a pelvic ultrasound can — and can't — tell you about bloating
The scan's central job for a bloated patient is the ovary check: a transvaginal ultrasound examines each ovary closely for cysts and masses, measures the uterus and any fibroids, and looks for free fluid in the pelvis. Those are exactly the structural causes worth ruling out — and it does so in a single appointment, with the findings explained to you in the room. If your swelling involves the upper tummy as much as the pelvis, a combined abdomen and pelvis ultrasound covers the liver, kidneys and other organs in the same visit.
What the scan cannot do is see into a gas-filled bowel — ultrasound does not image bowel gas well, which means it cannot diagnose IBS, trapped wind or food intolerance. That is not a flaw in the plan; it is the plan. A normal scan tells you and your GP, with confidence, that the structural causes are excluded — which turns a vague, anxious symptom into a focused bowel conversation. Your GP may also pair the scan with a CA-125 blood test; current NICE guidance sets age-specific CA-125 thresholds and recommends ultrasound as part of the same work-up.
If your bloating comes with pelvic pain, our pelvic pain guide covers that decision in the same way; and if you want to know what the internal scan itself feels like, every question is answered here.
Bloating and scans: your questions answered
Is constant bloating always something serious?
No — most persistent bloating turns out to be bowel-related (IBS, constipation, intolerance) or hormonal, and most scans for bloating are reassuring. But "usually benign" is a statistic, not a diagnosis: persistent bloating is also a recognised symptom of ovarian disease, which is why it should be checked rather than managed indefinitely with diet changes.
When should I worry about bloating?
When it stops being occasional: bloating most days, or more than 12 times a month, for around three weeks or more — especially over 50 — plus any of feeling full quickly, one-sided swelling, weight loss, new urinary urgency, or continuous (rather than cyclical) bloating after menopause. Any of those warrants a GP visit or a scan, not another month of experimenting.
Can an ultrasound see IBS or trapped wind?
No — ultrasound cannot image a gas-filled bowel, so it cannot diagnose IBS. What it does brilliantly is exclude the structural causes: ovarian cysts, fibroids and fluid. A normal scan doesn't end the story; it redirects it to the right one — usually a bowel-focused conversation with your GP.
What is the difference between bloating and ascites?
Bloating is a sensation of swelling, usually from gas, bowel content or hormonal fluid shifts, and it typically varies through the day. Ascites is actual free fluid collecting in the abdomen — it tends to be continuous, progressive and visible. Ultrasound distinguishes the two immediately, which is one of the most useful things the scan does for a persistently swollen tummy.
Will I need a CA-125 blood test as well?
Often, yes — for persistent bloating, UK guidance pairs the ultrasound with a CA-125 blood test, particularly in women over 40, using age-specific thresholds. CA-125 can be raised by many benign conditions, so it is interpreted alongside the scan, never alone.
Do I need a GP referral for a private scan?
No. You can self-refer — same-day appointments are usually available, you receive instant verbal results in the room, and the written report follows within 24 hours, ready to take to your GP for the next step in either direction.
Failed the trouser test?
If your bloating has outlasted the diet experiments, the structural check is one appointment.
What the pelvic scan checks
Abdomen & pelvis combined scan
Self-referral, same-day appointments at 29 Weymouth Street, Marylebone · £235 all-inclusive · instant verbal results, written report within 24 hours · 020 3633 4902
Sources and further reading
- NICE Guideline NG12 — Suspected cancer: recognition and referral (2015, amended 15 April 2026): recognition of ovarian cancer symptoms including persistent abdominal distension/bloating, and the age-banded CA-125 thresholds with urgent direct-access ultrasound. Accessed 11 July 2026.
- NHS.uk — patient information on bloating, ovarian cancer symptoms and irritable bowel syndrome. Accessed July 2026.
This article is general health information, not a diagnosis or individual medical advice. It was prepared by the Sonoworld clinical team from the practice experience of Daniela Stan, Consultant Ultrasound Practitioner, and against the national guidance listed above. If your symptoms match the warning signs at the top of this page, seek urgent medical care rather than booking a routine scan. Sonoworld Diagnostic Services, 29 Weymouth Street, Marylebone, London W1G 7DB — CQC-registered.
