Postoperative wound infection is a complication that can develop after surgery when bacteria enter the body through the incisions a surgeon makes. Though healthcare systems worldwide work hard to prevent these infections, they remain one of the most common challenges patients face during recovery, affecting their healing time and overall wellbeing.

How Common Are Postoperative Wound Infections

Postoperative wound infections, also known as surgical site infections, represent the primary source of hospital-acquired infections among people who have had surgery. These infections are responsible for over two million hospital-acquired infections in the United States each year.^[1] Despite the hard work of healthcare providers to prevent them, between one and three out of every 100 people who undergo surgery will develop an infection at their surgical site.^[4]

Before the development of modern medicine and the understanding that germs cause infection, the rates of postoperative infections were alarmingly high. Patients often faced severe consequences including limb amputation or death. However, once healthcare professionals began using antiseptic techniques—methods that prevent the growth of disease-causing microorganisms—patient outcomes improved dramatically.^[1]

These infections continue to significantly impact both patients’ health and healthcare costs. When someone develops a surgical site infection, they typically need to stay in the hospital for an additional seven to ten days. This extended hospitalization increases medical costs by approximately twenty percent compared to surgeries without complications.^[11]

What Causes Postoperative Wound Infections

The root cause of postoperative wound infections is bacteria that enter the body through the surgical incision. There are several ways these harmful microorganisms can reach the surgical site. First, bacteria already present on your skin can spread to the surgical wound during or after the operation. Second, germs inside your body or from the organ being operated on can contaminate the area. Third, bacteria present in the environment around you during surgery can enter the wound.^[3]

Several types of bacteria are particularly responsible for causing surgical wound infections. Staphylococcus aureus is the most common culprit behind these infections. Remarkably, about thirty percent of people carry these bacteria in their noses without knowing it, and they remain harmless until they get inside the body during surgery.^[2]

Streptococcus pyogenes, also known as Group A Streptococcus, is another common cause. This is the same bacterium responsible for strep throat. These bacteria live in people’s noses and throats and can spread when individuals sneeze, cough, or talk.^[2]

Enterococci bacteria normally live in your intestinal tract where they usually don’t cause problems. However, if they move from your intestinal tract during surgery—for example, if bacteria from your large intestine spill into your belly during an abdominal operation—they can cause a surgical wound infection.^[2]

Pseudomonas aeruginosa is another bacterium that can cause surgical wound infections. These infections may occur if you have these bacteria on your skin or if they are present on medical devices such as urinary catheters or ventilators.^[2]

Risk Factors for Developing Infections After Surgery

While anyone who undergoes surgery faces some risk of developing an infection, certain groups of people and specific circumstances increase this risk considerably. Understanding these risk factors helps both patients and healthcare providers take extra precautions when needed.

People with poorly controlled diabetes are at higher risk for postoperative wound infections. High blood sugar levels can interfere with the body’s natural healing processes and weaken the immune system’s ability to fight off bacteria.^[3] Similarly, individuals who have problems with their immune system—whether due to an underlying medical condition or medications that suppress immune function—find it harder to fight off infections that develop after surgery.^[3]

Body weight plays a significant role in infection risk. People who are overweight or obese face increased chances of developing surgical site infections. The extra tissue can make surgery more complicated and may reduce blood flow to the surgical area, making healing more difficult.^[3]

Smoking is another major risk factor. Cigarette smoke contains chemicals that reduce blood flow throughout the body and decrease the amount of oxygen reaching tissues. These effects significantly slow down wound healing and increase the likelihood of infection. Patients who smoke get more infections compared to non-smokers.^[4]

Certain medications can increase infection risk as well. People taking corticosteroids—medications like prednisone used to reduce inflammation—have a higher chance of developing postoperative infections because these drugs suppress the immune system’s normal responses.^[3]

The characteristics of the surgery itself also matter. Surgeries that last longer than two hours carry increased infection risk. Additionally, certain types of operations, particularly those performed on parts of the body that naturally contain many bacteria (such as the gut), have higher rates of infection than surgeries on other areas.^[3]

Older patients face elevated risks because the immune system naturally weakens with age. Malnourished individuals also struggle more with fighting infections and healing wounds properly.^[6]

Recognizing the Symptoms of Surgical Site Infections

Knowing the signs and symptoms of a postoperative wound infection is crucial because early detection and treatment can prevent serious complications. Most surgical wound infections show up within the first thirty days after surgery, though symptoms typically develop between three and seven days following the operation.^[3][2]

One of the most noticeable symptoms is thick, cloudy discharge from the wound. This discharge is often white or cream-colored and is commonly referred to as pus. You might also notice an unpleasant odor coming from the incision area—a smell that wasn’t present before.^[2]

Changes in the appearance of your surgical site should raise concern. The skin around the wound may become red, and this redness often extends beyond the edge of the incision. The area might also become swollen and feel warm or hot when you touch it. Pain at the surgical site that worsens instead of improving is another warning sign.^[2]

Sometimes the incision line itself changes. You might notice an opening where the edges of the wound separate. This opening can get deeper, longer, or wider over time if an infection is present.^[2]

Infections don’t always stay localized to the wound. They can cause whole-body symptoms as well. Fever is common—generally defined as a temperature greater than 101 degrees Fahrenheit or 38.4 degrees Celsius. You might also experience chills, sweating, and a general feeling of being unwell.^[2]

Different Types of Postoperative Wound Infections

Not all surgical site infections are the same. The Centers for Disease Control and Prevention classifies these infections into three distinct categories based on how deep they penetrate into the body. Understanding these different types helps healthcare providers choose the most appropriate treatment approach.

Superficial incisional infections are the most common type, accounting for more than half of all surgical site infections. These infections affect only the skin and the tissue just below the skin’s surface. Despite being the least serious type, they still require proper treatment to prevent them from spreading deeper.^[2]

Deep incisional infections extend beyond the skin and affect deeper soft tissues such as muscles and the fascial planes—the layers of connective tissue that separate and enclose muscles. An infection that develops after surgery on the breastbone (sternum) is an example of a deep incisional infection. These infections are more serious than superficial ones and often require more aggressive treatment.^[2]

Organ or space infections are the most serious type. These infections affect organs or the spaces between organs in the body. During surgery, a surgeon sometimes needs to gently move an organ aside to access the surgical area, which can lead to this type of infection. Organ or space infections occur in areas beyond where the incision was made but still related to the surgical procedure.^[2]

Preventing Postoperative Wound Infections

Prevention is always better than treatment when it comes to postoperative wound infections. Both healthcare providers and patients play crucial roles in reducing infection risk through various measures taken before, during, and after surgery.

Before surgery, there are several important steps you can take. If you smoke, making every effort to quit before your operation significantly reduces your infection risk. Healthcare providers often recommend having a bath or shower before coming to the hospital, using regular soap and water to clean your skin thoroughly.^[4] Some hospitals provide special antibacterial solutions or washcloths for patients to use before surgery.^[7]

One surprising but important recommendation is to avoid shaving near the surgical site. Shaving with a razor can irritate your skin and create tiny cuts that make it easier for bacteria to enter your body. If hair removal is necessary, healthcare providers should use alternative methods rather than razors.^[4]

During your hospital stay, proper hand hygiene is one of the most effective ways to prevent infections. Both healthcare workers and visitors should wash their hands with soap and water or use alcohol-based hand sanitizer before and after touching you or your surgical area. Don’t hesitate to remind healthcare providers to wash their hands if you don’t see them do so—it’s your right to speak up about your safety.^[4]

Family members and friends should never touch your surgical wound or dressings. Healthcare providers should wear gloves when caring for your wound, and the surgical site should remain covered with clean dressings to protect it from bacteria.^[4]

Healthcare providers may give you antibiotics just before or during surgery to help prevent infection. These prophylactic antibiotics—medications given to prevent rather than treat infection—are carefully timed to be present in your bloodstream when the surgical incision is made. However, continuing antibiotics for more than twenty-four hours after surgery has not been shown to provide additional protection against infections.^[11]

Once you go home, continuing to follow proper wound care instructions is essential. Always wash your hands before touching or caring for your surgical wound. Keep the area clean and dry according to your healthcare provider’s specific instructions. Make sure you understand how to care for your wound before leaving the hospital, and know who to contact if you have questions or concerns.^[4]

Maintaining a healthy diet supports your body’s natural healing processes. Stay well-hydrated by drinking enough water throughout the day. Continue to avoid tobacco products, as smoking during recovery significantly slows wound healing.^[4]

How the Body Heals After Surgery

Understanding how your body naturally heals wounds after surgery can help you appreciate why proper wound care is so important. Wound healing is a complex process that occurs in three main phases, each with distinct characteristics and purposes.

The first stage is the inflammatory phase, which is your body’s immediate response to the surgical injury. Right after surgery, blood vessels around the wound expand, increasing blood flow to the area. This is why the surgical site often looks red and feels warm to the touch. The extra blood brings special cells called neutrophils and macrophages—these act like a cleanup crew, fighting off bacteria and clearing away dead tissue. You’ll notice signs of inflammation including redness, heat, swelling, and possibly some pain. These are all normal parts of the healing process.^[17]

Next comes the proliferative phase, when the wound really starts to rebuild. New tissue called granulation tissue forms, made of collagen and other important substances that fill in the wound. New blood vessels develop through a process called angiogenesis, which helps bring nutrients to the healing area. The edges of the wound begin to pull together and shrink, and new skin starts to cover the wound.^[17]

Finally, the remodeling phase can last for months after surgery. During this time, the new tissue strengthens and matures. Collagen fibers reorganize themselves, making the wound area stronger. The wound might look healed on the outside, but inside your body continues working hard to restore the area’s strength. Over time, the wound area will regain most of its original strength, and blood supply returns to normal.^[17]

Any factor that disrupts these normal healing phases—such as infection, poor nutrition, inadequate blood flow, or continued smoking—can significantly delay recovery and lead to complications.