Post-operative complications
Read the operation note, then think by day: bleeding early, chest and urine in the middle, leaks and clots later.
A 58-year-old man is day 5 after an anterior resection for rectal cancer. He was eating yesterday. Now he has new lower abdominal pain, temperature 38.4 °C, pulse 118 and irregular (new AF), BP 104/66. The pelvic drain fluid has turned brown and smells. CRP has risen from 140 on day 3 to 290 mg/L today.
What has happened, and what do you do in the next hour?
- Read the operation noteWhat was done, how long, blood loss, drains, concerns, the surgeon's plan.
- A–ESeptic or peritonitic: resuscitate, cultures, antibiotics, surgical registrar now.
- Think by day after surgeryDay 0–1 bleeding, days 3–5 chest and urine, days 5–10 leak, abscess, wound, DVT and PE.
- Look everywhereWound, drains, abdomen, chest, calves, cannulas, catheter, fluid and drug charts.
- BloodsCBC, CRP, urea and electrolytes, magnesium, lactate, group and save or cross-match.
- ImagingCT with contrast for leak or collection, CTPA for PE.
- Clear handoverOperation, day, problem, findings, what's done, the plan.
- Fast pulse and low BP in the first 24 hours
- New AF, fever, ileus or rising CRP after bowel surgery
- Sudden breathlessness or chest pain
- Pink fluid from a laparotomy wound or bowel visible
- New leg weakness or numbness after an epidural or spinal
- Falling urine output despite fluids
- Bleeding
- Anastomotic leak or collection
- Pulmonary embolism
- Peri-operative MI (often painless)
- Burst abdomen
- Epidural haematoma or abscess
- Abdominal compartment syndrome
- Delirium from a hidden cause
| Fluid challenge | 500 mL crystalloid over 15 minutes (250 mL if frail or heart failure), reassess |
| Leak or post-op sepsis | Piperacillin-tazobactam 4.5 g IV 8-hourly, or per local policy |
| Clot prevention | Enoxaparin 40 mg subcutaneously daily (20 mg if creatinine clearance below 30), per surgeon's plan |
| CRP | Normally peaks day 2–3 then falls, a rise after day 3 is a warning |
| Primary bleeding | During surgery |
| Reactive bleeding | First 24 hours as BP returns |
| Secondary bleeding | Days 7–10, usually from infection |
| Anastomotic leak | Usually days 3–8 |
| Wound dehiscence | Often days 5–10, pink serous fluid first |
Check every dose against a current drug reference and your hospital protocol.
On this page
Start with the operation note
The operation note and anaesthetic chart tell you:
- What was done, and whether it was elective or emergency.
- Length of surgery and blood loss.
- Anastomoses, drains, stomas and where they are.
- Difficulties (adhesions, contamination, bleeding).
- The surgeon's instructions: antibiotics, anticoagulation, diet, drains, what to watch for.
Complications by time
- Hours–Day 1Bleeding (reactive), hypotension, anaesthetic effects, retention, nausea
- Day 1–3Atelectasis, low urine output, electrolyte disturbance, ileus, delirium
- Day 3–5Pneumonia, UTI, cannula infection, early leak
- Day 5–10Anastomotic leak, abscess, wound infection, dehiscence, DVT and PE, secondary bleeding
- Weeks to monthsIncisional hernia, adhesions, chronic pain
Common problems and causes
| Problem | Think of |
|---|---|
| Low BP | Bleeding, dehydration, sepsis, epidural, MI, arrhythmia, PE, drugs |
| Fast pulse or new AF | Pain, bleeding, sepsis, leak, PE, fluid overload, low potassium or magnesium |
| Low urine output | Blocked catheter, dry, AKI, retention, abdominal compartment syndrome |
| Fever | By day (see below) |
| Ileus | Opioids, low potassium or magnesium, immobility; prolonged ileus may be a leak or collection |
| Confusion | Infection, pain, retention, constipation, hypoxia, drugs, alcohol withdrawal |
| Breathlessness | Atelectasis, pneumonia, PE, fluid overload, MI |
| Wound problems | Infection, haematoma, seroma, dehiscence |
| Leg swelling | DVT |
Fever by day after surgery
| Day | Likely causes |
|---|---|
| 0–2 | Normal inflammatory response, atelectasis, transfusion reaction, early aspiration |
| 3–5 | Pneumonia, UTI, cannula or line infection |
| 5–10 | Wound infection, anastomotic leak, collection or abscess, DVT or PE |
| Any time | Drug fever, C. difficile, cellulitis at cannula sites, dengue or malaria in season |
See temperature spike.
The ones you must not miss
- Bleeding
- resuscitate, blood, reverse anticoagulants, surgeon, likely theatre
- Anastomotic leak
- resuscitate, antibiotics, CT, surgeon
- PE
- CTPA
- discuss anticoagulation with surgeons
- Peri-operative MI
- ECG, troponin, cardiology
- Burst abdomen
- cover with saline packs, analgesia, theatre
- Epidural haematoma or abscess
- stop epidural, anaesthetist, emergency MRI
A new fast pulse or AF days after bowel surgery is an anastomotic leak until proven otherwise. Don't just rate-control it: examine the abdomen, look at the CRP and drains, and ask for a CT.
Bleeding after surgery
- ResuscitateTwo large cannulas, cross-match, blood early. Hb falls late.
- Call the surgeonMost need return to theatre or interventional radiology.
- Reverse anticoagulantsStop enoxaparin; reverse warfarin or DOAC per protocol.
- Tranexamic acidConsider 1 g IV if the surgeon agrees.
- MonitorPulse, BP, drains, wound, urine output, repeat Hb and clotting.
Ileus
- Vomiting, distension, no flatus, quiet abdomen.
- Nil by mouth (or sips), NG tube if vomiting, IV fluids.
- Correct potassium and magnesium; reduce opioids; mobilise.
- Prolonged ileus (beyond 4–5 days after bowel surgery) or with fever and rising CRP: CT for leak or collection.
Wound problems
| Problem | Clues | Action |
|---|---|---|
| Surgical site infection | Redness, warmth, pus, day 5–7 | Open and drain if collection, swab, antibiotics if cellulitis |
| Haematoma | Swelling, bruising, early | Observe or drain; check clotting |
| Seroma | Fluctuant, clear fluid | Usually observe |
| Dehiscence (burst abdomen) | Pink serous fluid, then bowel | Cover with saline packs, sit up, analgesia, theatre |
Investigations
| Test | Why |
|---|---|
| CBC | Bleeding, infection |
| CRP (trend) | Infection, leak |
| Urea, creatinine, electrolytes, magnesium | AKI, ileus |
| Lactate | Ischaemia, sepsis |
| Clotting, group and save | Bleeding, theatre |
| ECG, troponin | MI, AF |
| Chest X-ray | Pneumonia, atelectasis (free air is normal for a few days after laparotomy) |
| CT with contrast | Leak, collection, bleeding |
| CTPA | PE |
| Wound swab, blood and urine cultures | Infection |
Treatment
Common mistakes
- Not reading the operation note.
- Rate-controlling new AF after bowel surgery without looking for a leak.
- Waiting for the Hb to fall before treating bleeding.
- Assuming fever on day 5 is "just the chest".
- Missing a painless MI in an elderly patient with low BP.
- Ignoring new leg weakness in a patient with an epidural.
- Leaving a plan that says "review in the morning".
Handover
Operation and day, the problem, your findings, what you have done, what the surgeon said, observation frequency, and when to call.
Frequently asked questions
What causes fever on day 5 after surgery?
Wound infection, anastomotic leak, collection, pneumonia, UTI, line infection and DVT or PE.
What are the signs of an anastomotic leak?
New tachycardia or AF, fever, worsening abdominal pain, prolonged ileus, rising CRP and abnormal drain fluid, usually 3–8 days after surgery.
What is a burst abdomen?
Breakdown of the laparotomy wound, often heralded by pink serous discharge around day 5–10, with bowel appearing in the wound. Cover it with saline-soaked packs and take the patient back to theatre.
When does post-operative bleeding happen?
Reactive bleeding in the first 24 hours as BP returns to normal, and secondary bleeding at 7–10 days, usually from infection.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. On day 6 after bowel surgery, a patient has fever, tachycardia, abdominal pain and brown drain fluid. What is likely?
Answer: Anastomotic leak. Leak usually days 5–8: resuscitation, antibiotics, CT, surgery.
- UTI: Doesn't explain the drain.
- Wound haematoma: No.
- Normal recovery: No.
- Atelectasis: Earlier and chest.
2. Pink serous fluid leaks from a laparotomy wound on day 8. What does it suggest?
Answer: Dehiscence. Cover with saline gauze; burst abdomen needs theatre.
- Urine leak: No.
- Lymph leak: Unlikely.
- Seroma only: May be, but pink fluid warns of dehiscence.
- Normal healing: No.
3. Within hours of surgery, a patient is tachycardic with a falling BP and a swelling wound. What is likely?
Answer: Reactive bleeding. Primary or reactive haemorrhage occurs early; resuscitate and inform the surgeon.
- Wound infection: Later.
- Pneumonia: Later.
- Anastomotic leak: Later.
- DVT: Later.
4. On day 5 after a right hemicolectomy, a patient has fever 38.8 °C, tachycardia, abdominal pain and rising CRP. What is the most likely cause?
Answer: Anastomotic leak. Postoperative fever timing: day 0–2 — physiological inflammatory response, atelectasis, transfusion reaction; day 3–5 — pneumonia, UTI, line infection; day 5–7 — anastomotic leak, intra-abdominal abscess, wound infection; after day 7 — DVT/PE, abscess, drug fever. Anastomotic leak presents with fever, tachycardia, ileus, abdominal pain, rising CRP; CT with contrast confirms. Treat with resuscitation, antibiotics, drainage or relaparotomy.
- Atelectasis: Atelectasis occurs on days 1–2.
- Transfusion reaction: Transfusion reactions occur during transfusion.
- Drug fever: Drug fever is a diagnosis of exclusion.
5. On day 8 after a midline laparotomy, salmon-pink serous fluid discharges from the wound. What does this indicate?
Answer: Impending wound dehiscence. Serosanguinous (‘pink’) discharge from a laparotomy wound 5–10 days after surgery heralds fascial dehiscence. Full dehiscence (burst abdomen) exposes bowel: cover with sterile saline-soaked dressings, analgesia, return to theatre for mass closure. Risk factors: obesity, malnutrition, steroids, diabetes, infection, raised intra-abdominal pressure (cough, ileus), poor technique (closure < 4:1 suture:wound length).
- Superficial wound infection: Superficial infection shows pus and erythema.
- Seroma only: A seroma is not salmon-pink and does not signal fascial breakdown.
- Normal healing: This is not normal healing.
6. What is the main biochemical role of vitamin C in collagen synthesis?
Answer: Hydroxylation of proline and lysine. Vitamin C is a cofactor for prolyl and lysyl hydroxylase, which hydroxylate proline and lysine in the rough endoplasmic reticulum. Hydroxyproline stabilises the triple helix. Without it, collagen is weak, causing scurvy: bleeding gums, perifollicular haemorrhages, poor wound healing and corkscrew hairs.
- Glycosylation of hydroxylysine: A later step, not vitamin C dependent.
- Cleavage of procollagen peptides: Done by procollagen peptidases outside the cell (defective in some Ehlers–Danlos).
- Cross-linking by lysyl oxidase: Lysyl oxidase needs copper (Menkes disease).
- Assembly of the triple helix: Follows hydroxylation; not directly vitamin C dependent.
7. During anaesthesia with a volatile agent and suxamethonium, a patient develops muscle rigidity, rising end-tidal CO₂, tachycardia and a high temperature. What is the treatment?
Answer: Stop the trigger and give dantrolene. This is malignant hyperthermia: an inherited (autosomal dominant, usually RYR1) defect in the ryanodine receptor causes uncontrolled calcium release in muscle. Triggers are volatile anaesthetics and suxamethonium. Dantrolene blocks the ryanodine receptor. Hyperkalaemia, acidosis and rhabdomyolysis follow if untreated.
- Switch to propofol, continue, cool: Stopping the trigger is right, but dantrolene is essential; surgery should be finished quickly.
- Give neostigmine to reverse: Neostigmine does not affect the muscle hypermetabolism.
- Paracetamol and surface cooling alone: Fever control alone does not stop the calcium leak in muscle.
- Give IV calcium gluconate: Calcium is not the treatment; the problem is excess calcium release.
References and dose sources
- NICE NG89 — venous thromboembolism: reducing the risk
- NICE NG180 — perioperative care in adults
- NICE CG174 — intravenous fluid therapy in adults
- Ringer's lactate (Hartmann's solution) dosing: Drugs.com: Lactated Ringer's dosage (see also our ringer's lactate (hartmann's solution) dose page)
- Piperacillin-tazobactam dosing: Drugs.com: Piperacillin/tazobactam dosage (see also our piperacillin-tazobactam dose page)
- Enoxaparin dosing: Drugs.com: Enoxaparin dosage (see also our enoxaparin dose page)
- Paracetamol dosing: Drugs.com: Acetaminophen (paracetamol) dosage (see also our paracetamol dose page)
- Ondansetron dosing: Drugs.com: Ondansetron dosage (see also our ondansetron dose page)
- Magnesium sulfate dosing: Drugs.com: Magnesium sulfate dosage (see also our magnesium sulfate dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.