If you experience excessive pain at your surgery site, you may have an infection.

Even the most careful patients can still suffer from a surgical site infection. Surgical site infections can originate at the incision point – the part of the wound that is open to the elements throughout the procedure and provides the main temporary barrier for the healing tissues – yet they can also be found in any area of the body that is part of the surgery. If you are unfamiliar with the different types of infections that can occur at surgical sites, familiarize yourself with the main categories of issues, as well as the complications that go along with each.

Types of Surgical Site Infections

There are a wide variety of surgical site infections (SSI) that can occur due to complications from a surgery, yet there are three main categories:

Organ SSI

As the name suggests, organ SSIs are those that occur in the organs – such as the liver, kidneys, intestines and the like – that are part of the surgery process. SSIs that occur in the space between organs can also be considered organ SSIs, as long as they are not infections that originate in the skin, muscle or fascia, according to Johns Hopkins Medicine.

Identifiers: Organ SSIs often produce discharge, such as white or yellow pus. Since these are often contained within the wound, the pus can either come through the drainage or create an abscess in the skin from the collection of pus. Because it is usually hidden from sight, it is best to visit with a clinician to examine whether X-rays are needed to find the infection site.

Deep Incisional SSI

Infections that are categorized as deep incisional often occur in the areas just below the first tissue layers – this includes the muscle tissue, fascia and fat beneath. It can also include the deep tissue that supports the muscle. According to the Centers for Disease Control and Prevention, deep incisional SSIs can occur much later in the healing process – anywhere from 30 to 90 days after the surgery has taken place.

Identifiers: These SSIs are often come with a fever and excess tenderness at the wound site. If the wound discharges pus, this pus could create a spontaneous discharge from any wound opening, or, like the organ SSIs, it could prompt an abscess. A clinician will want to likely take a culture of the pus or other discharge to identify the causing factors.

Superficial Incisional SSI

This is an infection that occurs at the point where the surgeons made the incision. They infect the skin, tissues and muscles that may have been part of the incision process, and usually take place within 30 days of the surgery, according to the CDC.

Identifiers: Because these infections take place at or near the surface, they are often one of the easier SSIs to treat. However, if they are not treated early, they could spread to deeper layers of the wound, creating larger (and often more costly) infections to treat. Clinicians that suspect a superficial incisional SSI may take a culture to figure out what types of bacteria or germs are causing the issue, according to Johns Hopkins.

As a final note: Pus is not a normal healing factor for any surgical wound. No matter what type of SSI you believe you have, pus should be a warning sign that your surgical wound is not healing properly, and needs further medical attention.