ConditionWhole body & general
Post-Operative Complications: What Is Normal and What Is Not
Post-operative complications are problems that develop after surgery, such as bleeding, infection, blood clots, lung problems, urinary retention or a reaction to anesthesia. Different complications tend to appear at predictable times: bleeding and breathing problems in the first day, lung and urinary issues in the first few days, wound infections and blood clots later. Knowing that timeline helps you tell normal recovery from warning signs. Most complications are minor and treatable, especially when reported early.
Also called: Postoperative complications, surgical complications, complications after surgery, post-surgical problems
At a glance
- What they are
- Unplanned problems after an operation, from mild (nausea, constipation) to serious (clots, leaks, sepsis).
- Most common
- Wound problems, pneumonia or collapsed lung segments, urinary retention or infection, blood clots, ileus and delirium.
- Timing matters
- Different problems peak at different days after surgery.
- Higher risk
- Older age, smoking, obesity, diabetes, heart or lung disease, emergency or long operations.
- What helps
- Walking early, deep breathing, clot prevention, wound care and reporting warning signs fast.
When to get help
Call 911 or go to the ER
- Sudden shortness of breath, chest pain, coughing up blood or fainting, which can be a pulmonary embolism: call 911 or your local emergency number
- Heavy bleeding that soaks through dressings, or a rapidly swelling, tense wound
- Confusion, a racing heart, fast breathing and fever or feeling very cold, which can be sepsis
- Severe belly pain that is getting worse, with a rigid belly, after abdominal surgery
See a doctor within a day or two
- A fever of 38.3 °C (101 °F) or higher, or 38 °C (100.4 °F) lasting more than a day
- A wound that is red, hot, increasingly painful, leaking pus or opening up
- Swelling, pain or warmth in one calf or thigh
- Unable to pass urine for 6 to 8 hours, or unable to keep fluids down
- No gas or bowel movement for more than 3 days with bloating and vomiting
Book a routine appointment
- Pain that is controlled but not improving after the first week
- Mild constipation from pain medicines
- Low mood, poor sleep or poor appetite weeks after surgery
Usually safe to manage at home
- Mild incision soreness, bruising, a little clear or pink drainage, tiredness and mild nausea in the first days
Complications by time after surgery
| When | Common problems | Typical signs |
|---|---|---|
| First 24 hours | Bleeding, anesthesia reactions, breathing problems, low blood pressure, nausea and vomiting, urinary retention | Rapid pulse, dizziness, swelling at the wound, drowsiness, inability to pass urine |
| Days 1 to 3 | Atelectasis (collapsed lung segments), delirium, ileus (sluggish bowel) | Low-grade fever, shallow breathing, confusion, bloating |
| Days 3 to 5 | Pneumonia, urinary tract infection | Fever, productive cough, burning urine |
| Days 5 to 7 and beyond | Wound infection, anastomotic leak after bowel surgery, abscess | Fever, red hot wound, worsening belly pain |
| Days 5 to 30 | Deep vein thrombosis and pulmonary embolism | Calf swelling, sudden breathlessness, chest pain |
| Any time | Medicine reactions, C. difficile diarrhea after antibiotics | Rash, watery diarrhea |
| Weeks to months | Incisional hernia, scarring, chronic pain | Bulge at the scar, persistent pain |
Fever after surgery: the "5 Ws"
Surgeons often use this memory aid to think through the cause of a fever by its timing:
- Wind (days 1 to 2): lung problems such as atelectasis or aspiration
- Water (days 3 to 5): urinary tract infection, especially with a catheter
- Wound (days 5 to 7): surgical site infection
- Walking (day 5 and later): blood clots in the legs or lungs
- Wonder drugs (any time): drug reactions, including antibiotics
A low-grade temperature on the first day is very common and often just the body's inflammatory response to surgery.
What is normal after surgery
- Pain at the incision that gradually improves day by day
- Mild bruising and swelling around the wound
- A small amount of clear, pink or light-red drainage for the first few days
- Tiredness for several weeks, more after major surgery
- Reduced appetite, mild nausea and constipation, especially with opioid pain medicine
- A sore throat after a breathing tube
- Disturbed sleep and low mood in the first couple of weeks
Major complications explained
Bleeding
Most bleeding happens within the first 24 hours. Signs include soaking dressings, a swelling collection of blood (hematoma), dizziness and a racing pulse. Blood thinners increase risk. Small hematomas often resolve. Larger ones may need draining or a return to the operating room.
Infection
Infections can affect the wound, lungs, urinary tract, bloodstream or deep tissues. See postoperative infection for details. Treatment ranges from opening and cleaning the wound to antibiotics and drainage of abscesses.
Blood clots
Surgery, immobility and tissue injury make blood more likely to clot. Risk is highest after hip and knee replacement, cancer surgery and long operations. Hospitals use blood thinners, compression stockings or pneumatic leg devices, and early walking to prevent clots.
Lung problems
Pain and anesthesia make people breathe shallowly, causing small areas of lung to collapse. This can lead to pneumonia. Deep breathing exercises, using an incentive spirometer every hour while awake, coughing with a pillow pressed on the wound, and getting out of bed early all help.
Bowel and bladder problems
Nausea, vomiting, urinary retention and ileus are common after anesthesia and abdominal surgery. Most settle in a few days. Opioid pain medicines cause constipation, so stool softeners or laxatives are often prescribed.
Delirium
Older adults can become confused, agitated or drowsy for a few days after surgery. Having family present, glasses and hearing aids, a regular sleep routine and avoiding unnecessary sedatives helps. Delirium needs to be reported, because it can signal infection or other problems.
Wound breakdown
The wound edges can separate (wound dehiscence), usually 5 to 10 days after surgery, especially with infection, obesity, diabetes, coughing or heavy lifting.
For a broader overview of risks by type of surgery and anesthesia, see surgical complications.
Who is at higher risk
- Age over 65 and frailty
- Smoking, which slows healing and raises lung and wound complications
- Obesity, diabetes, heart, lung or kidney disease
- Malnutrition or low protein
- Emergency surgery, long operations and major abdominal, chest or vascular surgery
- Steroids and other medicines that weaken immunity
How to lower your risk
Before surgery: stop smoking, ideally at least 4 weeks before. Control blood sugar. Walk daily to improve fitness. Ask which medicines to stop, especially blood thinners and some diabetes medicines.
After surgery:
- Get up and walk as soon as you are allowed, several times a day.
- Do breathing exercises every hour while awake.
- Take clot-prevention medicines and wear stockings as instructed.
- Keep the wound clean and dry, and wash your hands before touching it.
- Eat protein and drink fluids to support healing.
- Use pain medicine as directed so you can move and breathe deeply.
- Avoid heavy lifting for the period your surgeon advises, often 4 to 6 weeks after abdominal surgery.
Frequently asked questions
What are the most common complications after surgery?
The most common are nausea and vomiting, pain, constipation, urinary retention, wound infection, lung problems such as atelectasis or pneumonia, delirium in older adults, and blood clots. Most are minor and treatable, especially when spotted early.
Is it normal to have a fever after surgery?
A low-grade fever in the first 24 to 48 hours is common and usually reflects normal inflammation. A fever of 38.3 °C (101 °F) or higher, a fever starting several days after surgery, or fever with a red wound, cough or burning urine should be reported to your surgeon.
When should I call my surgeon after an operation?
Call for a fever of 101 °F (38.3 °C) or higher, increasing redness, pain or pus at the wound, calf swelling, vomiting that prevents drinking, inability to pass urine, or no bowel movement with bloating. Call 911 for sudden breathlessness, chest pain or heavy bleeding.
How long after surgery can complications occur?
Most complications appear within the first 30 days. Bleeding and anesthesia problems occur in the first day, lung and urinary problems within the first week, wound infections at about 5 to 10 days, and blood clots up to several weeks later. Hernias can appear months later.
How can I prevent blood clots after surgery?
Walk early and often, move your ankles and legs when sitting or lying, drink fluids, wear compression stockings if prescribed, and take any blood thinner exactly as directed. Report calf pain or swelling, or sudden breathlessness, immediately.
Sources
This guide was written from current patient and clinical guidance, including:
- American College of Surgeons: Surgical Patient Education, Recovering from Surgery
- Agency for Healthcare Research and Quality: Preventing hospital-acquired venous thromboembolism
- CDC: Surgical Site Infection Basics
- American Society of Anesthesiologists: Anesthesia risks and side effects (Made for This Moment)
- MedlinePlus: Surgery complications; Postoperative care