Acute Diverticulitis

1 · Recognise

• Constant left iliac fossa pain with localised tenderness, often over days
• Fever, raised CRP and WCC
• Change in bowel habit, nausea, occasionally a palpable mass
• Previous episodes are common and support the diagnosis

Right-sided diverticulitis occurs — more often in younger and East Asian patients — and is regularly operated on as appendicitis.

Always consider the alternatives: colorectal cancer can present identically, which is why follow-up matters.

2 · Assess severity

• ABCDE and observations; NEWS2
• Bloods: FBC, U&E, CRP, LFT, clotting, group & save
• Blood cultures if febrile
• Urine dip and pregnancy test where relevant
• Examine specifically for generalised peritonitis — guarding and rigidity mean perforation until proven otherwise

Separate the systemically well patient with localised tenderness from the one who is septic or peritonitic, because everything downstream follows from that.

3 · Imaging

• Contrast CT abdomen and pelvis is the investigation for suspected acute diverticulitis needing admission — it confirms the diagnosis, grades severity and finds complications
• Look for: pericolic abscess, free air, fistula, obstruction
• Do not perform colonoscopy acutely — the perforation risk is real. It belongs at follow-up, to exclude malignancy
• Erect CXR only adds free air; it does not replace CT

4 · Uncomplicated disease — antibiotics are a decision, not a reflex

For CT-confirmed uncomplicated acute diverticulitis in a systemically well patient, NG147 supports either:

• Oral antibiotics and discharge, or
• No antibiotics, with discharge and safety-netting

Review the need for antibiotics rather than prescribing automatically, taking account of co-existing conditions, immunosuppression and frailty.

This is a genuine change from older practice, and an F1 who prescribes antibiotics to every LIF pain out of habit is out of step with the guideline. Where antibiotics are given, follow local antimicrobial policy.

5 · Supportive management

• Analgesia — paracetamol first line. Avoid NSAIDs and opioids where possible: both are associated with perforation in diverticular disease
• Clear fluids initially, reintroducing diet as pain settles
• IV fluids if not tolerating oral
• VTE prophylaxis
• Safety-net on discharge: return with worsening pain, fever, vomiting, or failure to improve over 48–72 hours

6 · Complicated disease

Abscess — IV antibiotics; radiologically guided percutaneous drainage for larger collections. Surgical review.

Perforation with peritonitis — resuscitate, IV antibiotics, emergency laparotomy. Hartmann's procedure remains common; primary anastomosis in selected patients.

Fistula — colovesical is commonest, presenting with pneumaturia, faecaluria or recurrent UTI. Elective surgical management.

Obstruction — from stricture; needs surgical assessment and may need imaging to exclude malignancy.

7 · After the acute episode

• Arrange follow-up colonoscopy or CT colonography after recovery in those who have not had recent imaging of the colon — the differential is colorectal cancer
• Advise a high-fibre diet once recovered, introduced gradually, with adequate fluids
• Elective resection is considered for recurrent or complicated disease, as a colorectal decision
• Explain that recurrence is common and that most episodes are managed without surgery