01OverviewDefinition, clinical context and the essential points that orientate the chapter.
Free perforation is loss of the local containment that distinguishes a small pericolic leak or abscess. Purulent or faecal material enters the peritoneal cavity, producing diffuse peritonitis, fluid sequestration, ileus and septic organ dysfunction. The priority is simultaneous physiological rescue and elimination of the colonic source, not completion of every diagnostic test before treatment.
The operation removes the perforated segment and controls contamination. A Hartmann procedure avoids a new anastomosis but may leave a permanent stoma; primary anastomosis, sometimes protected by diversion, is reserved for suitable physiology and tissue. Age alone cannot select the reconstruction. The final decision uses shock, vasopressor requirement, contamination, perfusion, comorbidity and available colorectal expertise.
Laparoscopic lavage must not be generalised from selected purulent contamination to frank free perforation. It does not remove a persisting colonic defect or resect occult cancer and is unsuitable for faecal peritonitis, shock or uncontrolled leakage. ACPGBI recommends resection for generalised diverticular peritonitis and treats lavage cautiously; any exceptional consideration belongs to a stable, selected purulent-peritonitis setting with expert governance or research, not the shocked case.
Key points
- Free diverticular perforation causes diffuse purulent or faecal contamination, generalised peritonitis and potentially septic shock.
- Resuscitation, intravenous antibiotics, anaesthetic preparation and operative source-control planning must proceed in parallel.
- Contrast CT helps locate perforation and alternative pathology when transfer is safe; obvious peritonitis and instability must not wait for avoidable imaging delay.
- Resect the diseased perforated segment and wash out contamination; reconstruction depends on physiology, contamination, tissue perfusion and operative expertise.
- An end colostomy may be safest in profound shock or poor tissue, whereas selected stable patients may undergo primary anastomosis with or without diversion.
- Laparoscopic lavage is not treatment for frank free faecal perforation, persistent bowel-wall leakage or shock; only a highly selected stable purulent-peritonitis case might enter expert protocol or trial discussion, with resection still the usual source-control route.
- Postoperative failure of lactate, organ function or ileus to improve should prompt a search for residual collection, missed injury, leak or stoma compromise.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Rupture of inflamed sigmoid
Progressive mural necrosis or rupture of a diverticular abscess releases gas, bacteria and purulent or faecal material into the peritoneum.
Failure of local containment
A large defect, high contamination burden or impaired host defence prevents omentum and adjacent viscera from sealing the leak.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Diffuse peritoneal inflammation
Enteric contamination activates a widespread inflammatory response, draws fluid into the abdomen and causes painful guarding and paralytic ileus.
- 2Septic circulatory failure
Vasodilatation, endothelial leak and myocardial depression reduce effective organ perfusion, producing hypotension, oliguria, confusion and raised lactate.
- 3Impaired anastomotic healing
Shock, vasopressors, oedema, contamination and poorly perfused bowel increase the risk that a new colorectal join will fail.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Involuntary guarding, rebound, pain with movement and systemic toxicity indicate contamination beyond a localised phlegmon.
Hypotension and lactate elevation despite fluid suggest circulatory and cellular dysfunction requiring vasopressor and source-control coordination.
Severe contamination, acidosis, coagulopathy and instability reduce the safety of a primary anastomosis.
Hartmann resection avoids an anastomosis but creates a stoma that may never be reversed; selected stable patients may tolerate anastomosis.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Immediate blood gas and sepsis bloodsFirst step - Why
- quantify organ dysfunction and prepare transfusion or critical care.
- Interpretation and limitations
- A falling pH or rising lactate supports urgency but surgery should not wait for normalisation.
- 02
Contrast CT abdomen pelvis - Why
- confirm free perforation when the patient can safely transfer.
- Interpretation and limitations
- Diffuse free gas and fluid guide operative planning, but peritonitis remains a clinical emergency.
- 03
Preoperative anaesthetic assessment - Why
- identify resuscitation and postoperative support needs.
- Interpretation and limitations
- Risk discussion must occur alongside treatment rather than delaying source control.
- 04
Intraoperative assessment - Why
- determine contamination, tissue viability and reconstructive safety.
- Interpretation and limitations
- The operative finding may require changing a pre-imaging plan.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Perforated colorectal cancer
Tumour rupture causes the same peritonitis but requires oncological margins and nodal resection when the emergency situation permits.
Ischaemic colonic perforation
Arterial or venous insufficiency can produce segmental transmural necrosis, often extending beyond one inflamed diverticular segment.
Upper gastrointestinal perforation
A perforated peptic ulcer may create diffuse free gas and peritonitis; CT distribution and operative exploration identify the source.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Worked case: shock with faecal perforationResuscitate and choose a safe emergency reconstructionFirst stepA 76-year-old has a rigid abdomen, confusion, blood pressure 86/54 mmHg and lactate 5.1 mmol/L. CT obtained during immediate resuscitation shows perforated sigmoid colon, free gas and widespread faecal fluid.+
- 1Activate colorectal, anaesthetic and critical-care teams, give co-amoxiclav 1.2 g intravenously every 8 hours as one NICE national-table option after checking allergy and current renal function, obtain cultures and blood-bank samples, start warmed fluid and catheterise to measure urine output; adapt coverage to local resistance and sepsis policy.
- 2Use vasopressor support after initial fluid with anaesthetic oversight, correct hypothermia and major electrolyte disturbance, and proceed to theatre without waiting for lactate normalisation.
- 3Laparotomy confirms faecal peritonitis from a perforated sigmoid diverticulum; resect the diseased colon and wash out all quadrants.
- 4Because shock persists on vasopressor, tissue is oedematous and contamination is heavy, form an end colostomy rather than a high-risk primary anastomosis.
- 5Histology confirms perforated diverticulitis with no malignancy; by 24 hours lactate is 1.9 mmol/L and urine output has recovered, while daily review confirms a viable stoma and improving organ function.
02Stable physiology with resectable contaminationIndividualise primary anastomosis after operative assessmentA 55-year-old has generalised peritonitis but blood pressure 124/72 mmHg, lactate 1.8 mmol/L and no major comorbidity; CT shows a free sigmoid perforation with purulent fluid.+
- 1Begin antibiotics and operative preparation immediately, using CT to plan rather than to justify non-operative delay.
- 2At laparotomy assess contamination, remaining bowel perfusion, tension, nutritional reserve and the experience available for emergency colorectal reconstruction.
- 3Resect the perforated sigmoid; viable well-perfused ends and stable physiology permit a primary colorectal anastomosis with a protective loop ileostomy after shared senior judgement.
- 4Perform an anastomotic integrity test, document contamination and send the specimen for histopathology because cancer can also perforate.
- 5Recovery includes falling CRP, return of bowel function and no clinical or CT evidence of leak; final pathology demonstrates diverticulitis rather than tumour.
03Persistent sepsis after emergency resectionLook for residual or new postoperative sourceThree days after Hartmann resection, vasopressor requirement rises again, lactate is 3.7 mmol/L and the abdomen is increasingly distended despite functioning stoma output on day one.+
- 1Repeat ABCDE assessment, obtain cultures, review antibiotic coverage and involve the operating surgeon and critical-care consultant immediately.
- 2Examine the wound and stoma, review drains and assess for pneumonia, urinary infection and line infection while maintaining suspicion for an abdominal source.
- 3Urgent contrast CT shows a large undrained left subphrenic collection rather than stump failure or bowel ischaemia.
- 4Drain the accessible collection radiologically, send pus for culture and adjust antibiotics to the isolated organism and renal function.
- 5Verify control by falling vasopressor dose, lactate 1.5 mmol/L, restored enteral tolerance and interval imaging showing cavity collapse.
Key medicines and prescribing safety1 treatment · regimens, roles and cautions+
Intravenous co-amoxiclav for complicated diverticulitis
One NICE national-table option for suspected or confirmed complicated acute diverticulitis is co-amoxiclav 1.2 g intravenously every 8 hours; review after imaging or within 48 hours and tailor duration to cultures, response and operative source control.Do not use after severe immediate beta-lactam hypersensitivity or prior co-amoxiclav hepatic injury; calculate renal function and reduce the dose when creatinine clearance is 30 mL/min or less, review local resistance, hepatic tests, fluid status and cultures, and seek microbiology advice for severe allergy.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Multiorgan dysfunction
Persistent septic shock can injure kidney, lung, brain, liver, myocardium and coagulation despite apparently completed surgery.
Residual intra-abdominal collection
Loculated contaminated fluid can remain after washout and present with recurrent fever, ileus or rising inflammatory markers.
Stoma or anastomotic failure
Ischaemia, retraction, stump dehiscence or anastomotic leakage can recreate abdominal sepsis and require drainage or reoperation.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Trend mean arterial pressure, lactate, urine output, acid-base status and vasopressor dose before and after source control; direction matters more than one value.
- Review antimicrobial therapy against operative cultures and the adequacy of washout, narrowing when susceptibilities and recovery permit.
- Inspect stoma colour, perfusion, output and retraction and examine for wound or abdominal signs that could indicate recurrent contamination.
- Investigate persistent fever, ileus, rising CRP or new organ dysfunction with timely imaging for a residual collection, stump leak or anastomotic failure.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Source control is treatment
Antibiotics cannot sterilise ongoing faecal contamination without drainage or removal of the perforated source.
Anastomosis is a risk decision
The safest reconstruction depends on real-time physiology and contamination rather than a universal operation.
Hartmann has long consequences
Many emergency end colostomies are never reversed, so the immediate benefit must be balanced against future function.
Normalisation is not a prerequisite
Resuscitation and surgery proceed together; waiting for perfect lactate or blood pressure delays source control.
Lavage has narrow limits
A selected stable purulent-peritonitis discussion does not justify lavage for faecal contamination, persistent perforation or shock, where resection controls the source.
11Common pitfallsFrequent interpretation and management errors.
- 01
Sending an unstable peritonitic patient through prolonged imaging can delay life-saving source control.
- 02
Choosing primary anastomosis by age alone ignores shock, contamination and tissue viability.
- 03
Treating free perforation with oral antibiotics mistakes a surgical emergency for uncomplicated disease.
- 04
Stopping surveillance after laparotomy can miss persistent collection, organ failure or stoma compromise.
- 05
Offering lavage for free faecal contamination or a continuing perforation leaves diseased bowel and ongoing leakage in a patient who needs resectional source control.