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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Uncontrolled abscess sepsis or rupture
Hypotension, rising lactate, new diffuse peritonism, worsening organ dysfunction or continued sepsis despite a drain indicates failed containment or source control.
Action: Start or continue ABCDE sepsis treatment and intravenous antibiotics, obtain urgent colorectal and anaesthetic review, and use repeat CT only if safe and useful before drainage revision or emergency surgery.
Synopsis
Manage diverticular abscess as complicated diverticulitis with sepsis assessment, intravenous antibiotics, contrast CT and source-control planning based on size, location, accessibility and clinical response.
Suspected diverticular abscess requires sepsis assessment, intravenous antibiotics and contrast CT to define the infected cavity.
Record all collection dimensions, location, loculation, adjacent-organ effects and whether a safe percutaneous route exists.
For an abscess greater than 3 cm, NICE advises considering image-guided drainage when feasible or surgery.
Key red flags
Diffuse guarding or free intraperitoneal contamination means the collection is no longer safely contained and requires emergency operative assessment.
Persistent fever, pain, tachycardia or rising CRP after drainage may indicate a blocked or displaced catheter, undrained locules or continuing bowel leakage.
Hydronephrosis, bowel obstruction or worsening kidney function can result from pelvic abscess mass effect and changes the urgency of source control.
Investigation priorities
01
Contrast CT abdomen pelvisFirst step
confirm abscess size and drainage anatomy.
Management branches
Worked case: drainage of a five-centimetre pelvic abscessCombine measured anatomy with clinical response
A 68-year-old with fever and left iliac fossa pain has CT-confirmed sigmoid diverticulitis with a 5.0 cm pelvic abscess. Blood pressure is 126/70 mmHg, lactate 1.6 mmol/L and interventional radiology identifies a safe transgluteal route.
Admit, assess for sepsis, take blood cultures when appropriate and begin intravenous co-amoxiclav after checking penicillin allergy and renal function.
Review the CT jointly with colorectal surgery and interventional radiology; the collection is above 3 cm, lacks diffuse free contamination and has a safe access route.
Small abscess without a safe drain targetTreat medically and verify improvement
CT in a stable 59-year-old shows a 2.4 cm pericolic abscess without free gas, fistula, obstruction or organ dysfunction; pain and oral intake improve after admission.
Key medicines
Co-amoxiclav intravenousFor suspected or confirmed diverticular abscess, NICE lists 1.2 g intravenously three times daily; review within 48 hours or after scanning if sooner.Avoid in serious penicillin allergy, adjust for renal impairment and review hepatic history; use abscess culture and local susceptibility data to narrow treatment, with total duration based on source control and response.
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.