Cath Lab Digest

In clinical practice, two of the most common types of infected wounds podiatrists see are ulcerations and postoperative incision sites. In order to resolve these infections and ultimately close these wounds, one must have a strong understanding of the etiology of infected ulcerations and post-op infections, how to assess these wounds and how to select appropriate treatment options.

With this in mind, let’s start by discussing pedal ulcerations. Pedal ulcerations provide a portal for pathogen entry and therefore can lead to the development of infection in the deep soft tissues and bone.^1,2 If the infective process is not addressed, it can threaten preservation of the limb and life. Early detection of an infected ulceration is imperative to a good clinical outcome. Performing a thorough examination and using appropriate diagnostic modalities are essential when it comes to differentiating between a local soft tissue or osseous infection versus an ascending and/or systemic infection. Doing so will help you determine the appropriate medical and/or surgical intervention.³

Before you begin the examination, it’s important to obtain a thorough patient history as well as a focused history of the wound. Specifically, it’s essential to document any history of recent trauma, delay in treatment, prior infections or immune deficiencies that would place the patient at an increased risk for infection.

Inspection of the wound and the periphery should reveal any erythema, lymphangitis, drainage, exposed deep tissues or necrosis. Inspecting the wound will also give you clues as to the etiology of the wound site. For example, you may identify hyperkeratotic or macerated tissues to the wound periphery or perhaps note the functional position and nature of the foot type. During the examination of the wound, one should also be able to recognize induration, fluctuance (underlying abscess), crepitus (soft tissue emphysema), increased skin temperature, tenderness, bulla, edge undermining or odor. Hypotension, tachycardia, elevated temperature and altered mental status can be the first clues in determining the severity of a systemic infection and possible progression into septicemia.

Pertinent Diagnostic Pointers For Infected Ulcers

Serological testing may include but is not limited to glucose levels, hemoglobin A1c, CBC with differential, sedimentation rate, renal (electrolytes, blood urea nitrogen (BUN), creatinine) and hepatic profiles.⁴ One may submit deep wound tissue cultures and blood cultures with sensitivities for the standard aerobic and anaerobic assessment as well as fungi and acid-fast bacilli tests.⁵ When it comes to soft tissue wound cultures, the best way to obtain them is via curettage of the base of a cleaned lesion. Superficial swabs should be avoided.⁶ In general, swab cultures only collect the surface contaminating organisms. Tissue biopsy and culture, fluid aspiration cultures and a possible bone biopsy are better alternatives for culturing the infecting organism. A bone culture is indicated when one suspects osteomyelitis. It is usually performed in conjunction with a bone biopsy, which is considered the gold standard for diagnosis.^5,7,8
Differentiating between colonized and contaminated wounds in the lower extremity can be a significant clinical challenge. The Agency for Health Care Policy and Research (AHCPR) Clinical Practice Guideline defines the difference as the concentration of organisms in the wound. An infected wound contains a larger number of microorganisms than a contaminated wound and is generally considered infected when the number of organisms per gram of tissue exceeds 10⁶.⁹