Health condition · Clinically reviewed
Diverticulitis, when diverticular disease flares.
Inflammation of colonic pouches (diverticula) — from mild uncomplicated flares treated with observation to complicated abscess, perforation and fistula needing hospital care.
Why trust this guide
- 01
Clinically reviewed
Written by our editorial team and reviewed by a registered UK clinician before publication.
- 02
Sourced from guidance
Checked against NICE, ESCP and peer-reviewed sources you can see at the end.
- 03
Current for 2026
Reflects current UK guidance on diverticulitis diagnosis, restricted antibiotic use, and surgical care.
Key facts
Diverticulitis at a glance.
The essentials, in plain English — how common it is, how it is diagnosed, when antibiotics are used and when surgery is warranted.
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How common
Diverticular disease is very common with age — most adults over 60 have some diverticula.
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Who flares
Symptomatic diverticulitis affects a minority of people with diverticular disease.
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Uncomplicated
Mild flares often need only observation — NICE (2019) restricts routine antibiotics.
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Reference test
CT of the abdomen and pelvis is the reference standard for diagnosis and grading.
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Complicated
Abscess, perforation or fistula (Hinchey grading) may need surgery.
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Prevention
A fibre-rich diet, hydration and healthy weight reduce recurrence.
Why this guide matters
A modern, measured approach.
Guidance on diverticulitis has changed — fewer antibiotics for mild flares, more careful imaging, and clearer thresholds for surgery. The three points below shape the rest of this page.
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Not every flare needs antibiotics
NICE (2019) restricts antibiotics for uncomplicated disease — observation is often enough.
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CT is the reference test
It confirms the diagnosis, grades severity and detects complications you cannot see clinically.
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Complications change everything
Abscess, perforation and fistula need hospital care and, sometimes, surgery.
How the diagnosis is made
From first symptoms to a clear plan.
The steps a UK clinician will normally follow, in order — so you know what to expect and why.
Phase 1 · Recognising
Spotting the pattern and screening for red flags
Phase 2 · Confirming
Bloods, urinalysis and a CT scan of the abdomen
Phase 3 · Managing
Colonoscopy follow-up, gastro and surgical review
- 01
Recognising
Symptom & risk history
Left iliac fossa pain, fever, change in bowel habit — plus age, prior episodes and immune status.
- 02
Confirming
Baseline bloods
Full blood count and CRP — to gauge inflammation and infection.
- 03
Confirming
Urinalysis
Screens for urinary infection and, occasionally, a colovesical fistula.
- 04
Confirming
CT abdomen & pelvis
The reference test — confirms diverticulitis, grades severity and detects complications.
- 05
Managing
Colonoscopy after recovery
Usually 6–8 weeks after resolution to exclude underlying bowel cancer.
- 06
Managing
Gastroenterology review
For recurrent flares, medication review and long-term dietary planning.
- 07
Managing
Surgical review
Required if complicated — abscess, perforation, fistula or repeated severe episodes.
Typical timeline: days for a mild flare, weeks for follow-up colonoscopy after recovery.
Symptoms
What diverticulitis actually feels like.
Left-sided abdominal pain with fever and altered bowel habit is the classic pattern — but complicated disease has its own tell-tale signs.
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Left iliac fossa pain
The classic sign — often steady, localised to the lower left abdomen.
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Fever
A raised temperature suggests active inflammation or infection.
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Change in bowel habit
Either constipation or loose stools during a flare.
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Bloating
Distension and discomfort, often worse after meals.
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Peritoneal signs
Rigid, guarded abdomen with rebound tenderness — a marker of complicated disease.
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Abscess formation
A walled-off collection of pus — may need drainage as well as antibiotics.
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Fistula (bladder, vagina)
Air or stool in urine (pneumaturia) or vaginal discharge suggests a fistula.
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Red flag: peritonitis
Rigid abdomen with sepsis — call 999. This is a surgical emergency.
Treatment
How diverticulitis is treated in the UK.
A layered plan — observation and analgesia for mild flares, hospital antibiotics or drainage for moderate disease, and surgery for complications.
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Uncomplicated: analgesia + observation
NICE (2019) advises no routine antibiotics for mild uncomplicated diverticulitis — supportive care instead.
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Selective oral antibiotics
Reserved for patients with systemic features, comorbidity or immunosuppression.
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IV antibiotics + admission
For moderate disease — hospital care, intravenous fluids and antibiotics.
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Percutaneous abscess drainage
Image-guided drainage of collections above roughly 4 cm — usually with antibiotic cover.
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Emergency surgery for perforation
Faecal or purulent peritonitis needs urgent operative treatment.
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Elective sigmoid resection
Considered after recurrent complicated episodes or persistent fistula.
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High-fibre diet + hydration
Once recovered, gradual return to a fibre-rich diet with plenty of fluid reduces recurrence.
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Colonoscopy follow-up
Typically 6–8 weeks after the flare settles — to exclude an underlying tumour.
What this guide is based on
The sources behind every claim on this page.
UK national guidance and specialist society standards, current at the time of last review.
Key references
Guidelines and standards we relied on.
A quiet reminder
This guide is for information, not medical advice.
Your GP, gastroenterologist or surgeon knows your history and can tell you which parts apply to you. If in doubt, seek assessment — especially with any red-flag features.
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NICE. Diverticular disease: diagnosis and management (NG147).
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European Society of Coloproctology. Guidelines on diverticular disease.
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Royal College of Surgeons. Emergency general surgery standards.
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Bowel Research UK. Patient information on diverticular disease.
Red flags
When it is more than a flare.
Most flares settle. These are the patterns that need urgent assessment or emergency care — do not push through them.
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Peritonitis
Rigid, boardlike abdomen with severe pain — a surgical emergency, call 999.
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Sepsis
High fever, low blood pressure, confusion — needs immediate hospital care.
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Massive PR bleeding
Large-volume bleeding from the back passage — attend A&E.
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Fistula to bladder (pneumaturia)
Air or stool in the urine — needs urgent surgical review.
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Fistula to vagina
Faecal discharge from the vagina — needs urgent surgical review.
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Abscess larger than 4 cm
Usually needs drainage as well as antibiotics.
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Recurrent complicated episodes
Repeated flares with complications may need elective surgery.
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Immunosuppression
Steroids, chemotherapy or transplant meds raise the threshold to treat and admit.
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Pregnancy with a flare
Any suspected flare in pregnancy needs specialist assessment.
Living with it
A common condition, very manageable in most people.
Four things that make the biggest difference day to day — diet, weight, medication awareness, and knowing when to seek review.
A quiet reminder
Small, steady habits beat crash changes.
Gradual fibre increases, regular fluids and consistent activity are more protective than an intense reset that does not last.
- 01 Diet
Rebuild fibre slowly
After a flare settles, reintroduce fruit, vegetables, pulses and wholegrains gradually with plenty of water.
- 02 Weight
Small changes, steady weight
Healthy weight and regular movement lower the risk of future flares.
- 03 Meds
Know your triggers
Discuss NSAIDs, steroids and opioids with your GP — some medicines raise flare and perforation risk.
- 04 Reviews
Reassess if the pattern changes
New severe pain, bleeding or fever deserves prompt review — do not wait it out.
Frequently asked
Everything we get asked about diverticulitis.
Quick answers on antibiotics, imaging, surgery, colonoscopy follow-up and how to reduce the chance of another flare.
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What is diverticulitis?
Inflammation or infection of small pouches (diverticula) that form in the wall of the colon — most often the sigmoid. It ranges from a mild uncomplicated flare to complicated disease with abscess, perforation or fistula.
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Do I always need antibiotics?
No. NICE guidance (2019) advises against routine antibiotics for mild uncomplicated diverticulitis — supportive care is usually enough. Antibiotics are used for systemic features, comorbidity, immunosuppression or complicated disease.
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What test confirms it?
A CT scan of the abdomen and pelvis is the reference test — it confirms the diagnosis, grades severity (Hinchey classification) and detects complications like abscess or perforation.
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Will I need surgery?
Most people do not. Surgery — usually a sigmoid resection — is reserved for perforation, uncontrolled sepsis, fistula or repeated complicated episodes.
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Why do I need a colonoscopy afterwards?
Usually 6–8 weeks after the flare settles, to make sure no underlying bowel cancer has been missed in the inflamed segment.
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How do I lower the chance of it coming back?
A fibre-rich diet, good hydration, healthy weight, regular activity and, where possible, avoiding NSAIDs all reduce recurrence.
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