What Is Postoperative Fever?

Medically Reviewed by Nayana Ambardekar, MD on June 06, 2023
Written by WebMD Editorial Contributors
3 min read

Postoperative fever is a temperature higher than 102.2 F on any day after surgery or 100.4 F on any two consecutive days after surgery. Fever after surgery is very common. Most cases are harmless and go away on their own. 

Postoperative fever occurs in up to 90% of people who have surgery. Any type of surgery causes injury and inflammation. Part of your body's response to this injury and inflammation can be fever. Aside from this inflammatory response, atelectasis is the most common cause of postoperative fever. 

Fever after surgery can be serious, so it needs to be evaluated. There are a lot of different conditions that can cause postoperative fever. Doctors use the Five Ws to classify the conditions that can cause you to run a fever after surgery.  

Wind. This category addresses problems with your lungs, including atelectasis and pneumonia. Atelectasis is one of the most common causes of postoperative fever. It happens when the little air sacs within your lungs deflate. General anesthesia can cause atelectasis because it changes your normal breathing pattern. ‌

Pneumonia is the third most common complication after surgery. It's an infection in your lungs. Pneumonia after surgery will usually lead to a longer hospital stay. In some cases, it can be dangerous and even fatal. ‌

Water. This refers to a fever caused by a urinary tract infection. If you had a urinary catheter during your surgery, you have a greater chance of getting a UTI.

Wound. Infections that happen at or near the surgical site are referred to as surgical site infections. You can have a superficial surgical site infection in the skin. It can also be a more serious infection involving the tissues and organs. 

Walking. Fevers that are caused by deep vein thrombosis fall under this category. Deep vein thrombosis happens when you get a blood clot in a vein deep inside your body, usually your leg. You have a better chance of deep vein thrombosis after surgery because you aren't moving as much as usual. A pulmonary embolism, which is a blood clot in your lungs, is also in this category. ‌

Wonder drugs. This category covers fevers caused by medicine and blood products. If you're given medicine during your surgery that causes a bad reaction, you may get a fever. It can sometimes be short-lived and clear up on its own. It may also be a serious reaction that has to be treated immediately.  ‌

There can be other causes as well, including: 

You can expect to have a slight fever in the first 2 days after you have surgery. Unless you have other symptoms as well, your doctor will probably monitor your condition. You likely won't need a workup. 

If you have other symptoms or a high or persistent fever, you will need additional tests to determine the cause. Your doctor may tests, including: 

How your medical team will treat your postoperative fever will depend on the cause. Options include: 

If you have any of the following signs of infection after your surgery, let your doctor know: 

  • Fever higher than 101 F. 
  • Pus or more drainage from your incision
  • More swelling
  • Redness or warmth at the site of your incision
  • A foul smell coming from the incision‌

You should also call if you're coughing up or vomiting blood, or if you have:  

  • Severe headache or other pain
  • Loss of appetite
  • Problems breathing
  • Dark or bloody bowel movements
  • A tear in your incision
  • Redness or pain near your incision
  • Constipation or diarrhea
  • Very tired feeling‌

Even if you don't have any of the symptoms above, call your doctor if you just generally feel worse than when you left the hospital, or if you have any other symptoms that concern you.