PassFinals
General Surgery

Bowel Perforation

A full-thickness breach of the gut wall spills gas and enteric contents into a sterile cavity, so chemical irritation is followed by bacterial peritonitis and sepsis.

In a nutshell

Bowel perforation spills gas and enteric contents into the peritoneum, causing peritonitis and often sepsis. Resuscitate on the NICE NG253 sepsis pathway, give broad-spectrum intravenous antibiotics within 1 hour, then get the patient to CT and to theatre. Antibiotics never close a hole.

Classic presentation

A 72-year-old taking long-term ibuprofen with sudden epigastric pain that is now generalised, lying rigidly still with a board-like abdomen, heart rate 118 and free gas under the right hemidiaphragm.

Key points

  • Free gas is visible on a plain film in only 30 to 85% of perforations, so a normal erect chest radiograph excludes nothing.
  • Sit the patient upright for 10 to 20 minutes before the erect chest film, so free gas has time to rise under the diaphragm.
  • Up to 12% of perforations have a normal CT. If suspicion persists, repeat with water-soluble contrast by mouth or nasogastric tube.
  • Peritonitis is absent in about a third of perforated peptic ulcers, so a soft abdomen does not rule out a hole.
  • RCS England sets the standard NELA audits: a consultant surgeon and a consultant anaesthetist in theatre whenever predicted mortality is 5% or more.
  • NELA found only 15.4% with suspected sepsis got antibiotics within 1 hour, and only 8.4% of the most urgent reached theatre within 6 hours.
  • Assess frailty within 4 hours of admission. A Clinical Frailty Scale of 5 or more counts as frail and means an escalation plan.
  • Penicillin and cephalosporin cross-reactivity is up to 10% for first and early second-generation agents, and 2 to 3% for third-generation.

First-line investigation

Venous gas with lactate plus the sepsis blood set and cultures, then contrast-enhanced CT of the abdomen and pelvis. The erect chest radiograph is quicker but misses many perforations.

Management

Resuscitate and start the sepsis clock

  • Score NEWS2 (National Early Warning Score 2). Seven or more is high risk: urgent FY2-level review, venous gas with lactate, cultures, FBC, CRP, U&E and clotting.3
  • Balanced crystalloid such as Hartmann's: 250 mL over 10 to 15 minutes, reassess, repeat to a 1,000 mL maximum, then senior clinical decision maker.3
  • Oxygen to 94 to 98%, or 88 to 92% if at risk of hypercapnic respiratory failure. Nil by mouth. Catheterise and chart hourly urine output.10,3
  • Broad-spectrum intravenous antibiotics within 1 hour of calculating NEWS2. Refer to the senior surgical decision maker at the same time, not afterwards.3,4
  • Morphine 5 mg by slow intravenous injection every 4 hours, titrated to response, or 10 mg by mouth or intramuscularly; 5 mg if frail or elderly.18,8

Choose the antibiotic

  • BNF peritonitis regimen: piperacillin with tazobactam 4.5 g intravenously every 8 hours alone, increased to every 6 hours in severe infection.12,13
  • Or gentamicin 5 to 7 mg/kg once daily, adjusted to serum concentration, with metronidazole 500 mg intravenously every 8 hours. Clindamycin may replace the metronidazole.12,14,15,16
  • Colonic or diverticular source (NICE NG147): co-amoxiclav 1.2 g intravenously three times a day, or cefuroxime 750 mg three or four times daily with metronidazole 500 mg.5
  • Allergy to both penicillins and cephalosporins: ciprofloxacin 400 mg intravenously two or three times a day with metronidazole 500 mg three times a day.5,17
  • Review the intravenous antibiotic at 48 hours, or sooner after scanning, and step down to oral. Up to 14 days for a CT-confirmed abscess.5,10

Image and stratify

  • Contrast-enhanced CT of the abdomen and pelvis now. Do not wait for creatinine or fluid pre-loading; RCEM says neither is a prerequisite.8,1
  • RCS England asks for the radiologist's report within 1 hour of the scan. NELA found only about half of urgent scans met that.7,9
  • Surgical review by ST3 or above within 30 minutes of referral for suspected gastrointestinal perforation or faeculent or purulent peritonitis.8
  • Calculate predicted mortality before theatre with the NELA (National Emergency Laparotomy Audit) risk calculator. Five per cent or more is high risk.9,7

Control the source, against a clock

  • Source control underway within 3 hours in septic shock, and within 6 hours in sepsis without shock. Antibiotics do not close a hole.7,4
  • NCEPOD classes perforated bowel with peritonitis as Urgent: theatre within hours of the decision to operate, normally once resuscitation is complete.19
  • A consultant surgeon and a consultant anaesthetist present, with direct critical care admission afterwards, whenever predicted mortality is 5% or more.7,9
  • Consultant review within 14 hours of admission, and consultant discussion within 1 hour if predicted mortality exceeds 10% or the patient is not responding.20

Match the operation to the cause

  • Diverticular perforation with generalised peritonitis: laparoscopic lavage or resection, discussed with the patient. Faecal peritonitis found at operation means resection.5
  • Diverticular abscess larger than 3 cm: percutaneous drainage or surgery. Smaller than 3 cm: antibiotics, switching to oral where possible.5
  • Perforated peptic ulcer with significant pneumoperitoneum, contrast extravasation or peritonitis: repair as soon as possible, especially after delay or above age 70.1
  • Non-operative management only in extremely selected cases where the perforation has sealed, confirmed on a water-soluble contrast study, under specialist observation.1,4

Not improving

  • No response within 1 hour of any intervention: the senior clinical decision maker attends in person, critical care is involved, the responsible consultant is informed.3
  • Persistent fever, ileus, pain or organ failure after source control means an undrained collection or an anastomotic leak until repeat imaging proves otherwise.4,2

Narrow, and treat the cause

  • Narrow the antibiotic once the source is confirmed or cultures return. A Clinical Frailty Scale of 5 or more triggers an escalation plan and a resuscitation decision.10,7
  • Perforated ulcer: stop the NSAID, start a proton pump inhibitor at the BNF dose, and test for Helicobacter pylori.1,5
  • Then colorectal or inflammatory bowel follow-up, cancer investigation, stoma care, nutrition, and an honest conversation about ceilings of treatment.7,5

Exam traps

  • The sepsis bolus is 250 mL, not 500 mL. NICE NG253 changed it in 2025; the 500 mL bolus in CG174 is for hypovolaemia.
  • A negative erect chest radiograph never excludes perforation. Small, sealed and retroperitoneal leaks produce no gas under the diaphragm at all.
  • A minor rash more than 72 hours after a penicillin is probably not allergy. Do not withhold a beta-lactam from a septic patient for it.
  • NCEPOD calls perforated bowel with peritonitis Urgent, meaning hours; RCS and NELA call gastrointestinal perforation Immediate. Two scales, same message: not tomorrow.
  • Laparoscopic lavage is an option for diverticular perforation with generalised peritonitis, but faecal peritonitis found at operation commits you to resection.
  • Do not delay contrast CT for renal function or fluid pre-loading. RCEM says neither is a prerequisite in the emergency setting.
  • Morphine is listed under acute abdomen in the BNF contra-indications, yet withholding analgesia is a recognised failing. Give it, then re-examine.
  • NICE advises avoiding NSAIDs and opioids in diverticular disease because they may raise perforation risk. That is advice for the stable outpatient.

Illustrations

Free air under the diaphragmAn erect chest radiograph showing a crescent of free gas beneath the right hemidiaphragm, illustrating pneumoperitoneum from a perforated viscus while noting that a negative film does not exclude perforation.Clinical Cases, Wikimedia Commons · CC-BY-SA-2.5

Key sources

  1. WSES (World Society of Emergency Surgery): perforated and bleeding peptic ulcer guidelines (World Journal of Emergency Surgery 2020, volume 15, article 3; free gas on plain film in 30 to 85% of perforations, a normal CT in up to 12%, water-soluble contrast when imaging is negative, indications and timing for surgery, and the limits of non-operative management. Used because no dedicated current NICE guideline on perforated peptic ulcer was identified)Published 7 Jan 2020
  2. Association of Coloproctology of Great Britain and Ireland (ACPGBI): consensus guidelines in emergency colorectal surgery (Colorectal Disease 2021, volume 23, pages 476 to 547; the UK consensus on emergency colorectal decision making, including containment, source control and the choice between repair, resection, anastomosis, stoma and drainage. Free full text hosted by PubMed Central)Published 20 Jan 2021
  3. NICE NG253: suspected sepsis in people aged 16 or over, recognition, assessment and early management (Recommendation 1.6.2 on the NEWS2 risk bands; 1.8.1 on samples before antimicrobials; 1.8.2 on urgent assessment and testing; 1.8.3 on broad-spectrum intravenous antibiotics within 1 hour of calculating NEWS2; 1.8.4 to 1.8.9 on the balanced-crystalloid bolus of 250 mL over 10 to 15 minutes, repeated to 1,000 mL with reassessment after each and a senior clinical decision maker beyond; 1.8.15 on no response within 1 hour)Published 19 Nov 2025
  4. NICE NG253: finding and controlling the source of infection (Section 1.11; recommendation 1.11.3 on imaging the abdomen and pelvis when no source is found, and 1.11.4 on involving the surgical team or interventional radiologist early, seeking senior advice on timing and intervening as soon as possible)Published 19 Nov 2025
  5. NICE NG147: diverticular disease, diagnosis and management (Recommendation 1.2.5 on avoiding NSAIDs and opioids; 1.3.5 on contrast CT within 24 hours of admission; 1.3.11, 1.3.13 and 1.3.14 with table 2 of intravenous antibiotics and their doses; 1.3.19 and 1.3.22 to 1.3.25 on abscesses; 1.3.26 and 1.3.27 with table 3 on perforation, lavage, resection and anastomosis)Published 27 Nov 2019
  6. Radiology Masterclass: abdominal X-ray, free gas and pneumoperitoneum (UK radiology teaching resource accredited under the Royal College of Radiologists CPD scheme and written by a consultant radiologist; the erect chest radiograph technique, the 10 to 20 minute upright interval before exposure, detection of as little as 1 mL of gas, and Rigler's, football and falciform ligament signs)Updated 1 Jul 2023
  7. Royal College of Surgeons of England (RCS England): The High-Risk General Surgical Patient, Raising the Standard (Key recommendation 1 on antimicrobials within 1 hour and a radiologist's report within 1 hour of emergency abdominal CT; key recommendation 4 defining high risk as a predicted hospital mortality of 5% or more; key recommendation 8 on source control underway within 3 hours in septic shock or 6 hours in sepsis, with a consultant surgeon and consultant anaesthetist present; the risk assessment section on the NELA risk model; the frailty section on assessment within 4 hours and a Clinical Frailty Scale of 5 or above)Published 1 Dec 2018
  8. Royal College of Emergency Medicine (RCEM): advisory statement on the management of adults presenting to the emergency department who may require an emergency laparotomy (Table 1, adapted there from RCS England 2018: gastrointestinal perforation and faeculent or purulent peritonitis in the immediate-surgery group, surgical review by ST3 or above within 30 minutes of referral, and immediate CT request. Also that renal function tests and precautionary fluid pre-loading are not prerequisites for emergency contrast CT, and that relief of pain and vomiting should be prioritised)Published 1 Oct 2024
  9. NELA (National Emergency Laparotomy Audit): Tenth Patient Report, executive summary (Covers 23,560 patients in 176 hospitals between 1 April 2023 and 23 April 2024. Table 2.1 groups pneumoperitoneum, peritonitis and gastrointestinal perforation as RCS Immediate; 52.9% of patients were high risk, with a consultant surgeon present for 96.4% and a consultant anaesthetist for 92.3%; 15.4% with suspected sepsis received antibiotics within 1 hour; 8.4% of the most time-critical reached theatre within 6 hours and 75% waited more than 10.2 hours; about half of urgent CT scans were reported within 1 hour; 30-day mortality 8.1%)Published 1 Oct 2024
  10. NICE NG253: antibiotic therapy, intravenous fluid and oxygen (Recommendation 1.9.1 on reviewing and narrowing the antibiotic once the source or microbiology is known, 1.9.2 and 1.9.7 on using local antimicrobial guidance when the source is clear, and 1.10.1 on oxygen saturation targets of 94% to 98%, or 88% to 92% for those at risk of hypercapnic respiratory failure)Published 19 Nov 2025
  11. NICE CG174: intravenous fluid therapy in adults in hospital, key priorities for implementation (Resuscitation key priority: for patients needing intravenous fluid resuscitation, a crystalloid containing sodium 130 to 154 mmol/litre given as a 500 mL bolus over less than 15 minutes. This is the hypovolaemia bolus, not the sepsis bolus)Published 10 Dec 2013 | Updated 5 May 2017
  12. BNF treatment summary: gastro-intestinal system infections, antibacterial therapy (Recommended antibacterials for peritonitis (a cephalosporin with metronidazole, gentamicin with metronidazole, gentamicin with clindamycin, or piperacillin with tazobactam alone) and for complicated acute diverticulitis)
  13. BNF: piperacillin with tazobactam (Adult intravenous dose for septicaemia and complicated infection, the dose-equivalence note, renal dose adjustment, and the allergy and cross-sensitivity section for all penicillins)
  14. BNF: gentamicin (Adult once-daily intravenous dose adjusted by serum concentration, dosing at extremes of body weight, and therapeutic drug monitoring requirements)
  15. BNF: metronidazole (Adult intravenous dose for anaerobic infection)
  16. BNF: clindamycin (Adult intravenous dose for peritonitis and intra-abdominal sepsis, with the maximum single infusion dose)
  17. BNF: cefotaxime (Allergy and cross-sensitivity for all cephalosporins: cross-reactivity with penicillins reported in up to 10% of penicillin-allergic patients for first and early second-generation cephalosporins, and 2 to 3% for third-generation)
  18. BNF: morphine (Adult dose for acute pain by mouth, intramuscularly and by slow intravenous injection, the reduced dose in frail and elderly patients, and the contra-indications, which include acute abdomen)
  19. NCEPOD: Classification of Intervention (The four categories Immediate, Urgent, Expedited and Elective, with target times to theatre. Perforated bowel with peritonitis is given as the worked example of Urgent, meaning within hours of the decision to operate and normally once resuscitation is complete, with laparotomy for perforation as the typical procedure)
  20. NCEPOD (National Confidential Enquiry into Patient Outcome and Death): Acute Bowel Obstruction, Delay in Transit (Recommendation 2: consultant review as soon as clinically indicated and at the latest within 14 hours of admission, with consultant discussion within 1 hour for high-risk patients, defined there as a mortality risk greater than 10% or a patient who is unstable and not responding as expected. NCEPOD attributes the standard to RCP London and NHS England)Published 9 Jan 2020

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.