Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
2 min synopsisUK scopeSources checked 8 Sept 2026Clinical review pending
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Sepsis, peritonitis or obstruction in suspected diverticulitis
Generalised rigidity, hypotension, altered mental state, rising lactate, persistent vomiting with distension, or CT evidence of free perforation demands immediate resuscitation and colorectal review.
Action: Begin ABCDE treatment, obtain intravenous access and blood cultures when this does not delay care, give intravenous broad-spectrum antibiotics, and coordinate urgent source-control assessment with surgery and anaesthesia.
Synopsis
Diagnose suspected acute diverticulitis clinically, identify sepsis or complicated disease, and use contrast CT in secondary care when inflammatory markers or the examination suggest abscess, perforation, fistula or obstruction.
Suspect acute diverticulitis when pain becomes constant in the left lower quadrant with focal tenderness, fever or bowel-habit change.
Assess physiology and the abdomen before assigning severity; peritonism, sepsis, vomiting, distension or fistula symptoms suggest complicated disease.
In secondary care, raised inflammatory markers should prompt contrast CT within 24 hours to confirm the diagnosis and define complications.
Key red flags
Generalised guarding or rigidity indicates possible uncontained perforation and must not be managed as uncomplicated disease.
Hypotension, confusion, oliguria or rising lactate signifies organ hypoperfusion and requires parallel sepsis resuscitation and source-control planning.
A tender mass, faecaluria, persistent vomiting or marked distension suggests abscess, fistula or obstruction requiring urgent imaging and specialist assessment.
Investigation priorities
01
Contrast CT abdomen pelvisFirst step
confirm disease and identify complications.
Management branches
Worked case: CT defines uncomplicated diseaseConvert clinical suspicion into a severity decision
A 70-year-old has 48 hours of constant left iliac fossa pain, temperature 38.2°C, focal tenderness without generalised guarding, blood pressure 132/76 mmHg and CRP 146 mg/L.
Record full observations, examine for peritonism and assess hydration, renal function, immune status, comorbidity and ability to take oral treatment.
Arrange contrast CT within 24 hours because the inflammatory markers are raised and the patient is being assessed in secondary care.
CT-defined abscess managementUse collection size and access to plan source control
A stable inpatient with CT-confirmed sigmoid diverticulitis has a 4.2 cm pericolic abscess, temperature 38.3°C and no diffuse free gas or generalised peritonism.
Key medicines
Co-amoxiclav oralFor acute uncomplicated diverticulitis when antibiotics are indicated, give 500/125 mg by mouth three times daily for 5 days.Avoid in serious penicillin allergy; adjust for renal impairment, check hepatic history and review sooner if symptoms worsen or oral treatment is not tolerated.
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 8 Sept 2026; clinical approval remains outstanding.