Re-Thinking the Definition of Complicated Intra-Abdominal Infection

To the Editor:

We read with great interest the recent Surgical Infections article published by Mazuski et al [1]. The authors revised the guidelines on the management of intra-abdominal infection (IAI) in 2010 [2].

In the guideline, the authors discussed the definition of uncomplicated and complicated IAI (cIAI). Infections limited to a hollow viscus were called uncomplicated IAI, whereas those that extended into a normally sterile area of the abdomen were defined as cIAI [1]. According to this definition, the classification of IAI is mainly dependent on the anatomic characteristics of infection.

We are afraid that the definition of cIAI is not fully appropriate. The aim of the IAI classification is to identify the severity of the disease so that enough attention from the clinician can be raised. We think a judgment only depending on the existence of peritonitis and the need for surgical intervention is questionable. For example, acute appendicitis might induce peritonitis, but it is not tough enough for special attention from the clinician. Yet for acute obstructive suppurative cholangitis with hemodynamic instability that would not lead to peritonitis, it is fatal and, in this case, immediate hemodynamic support is essential [3]. Another typical example is Clostridium difficile colitis. In this case, the infection does not extend beyond the hollow viscus but can induce sepsis, acute kidney failure, and disturbance of consciousness [4]. It is a severe IAI that needs more attention than peritonitis.

From another perspective, organ function might be another important factor when judging the IAI classification. In our opinion, organ/system dysfunction or anatomic structural abnormality induced by IAI can also be categorized as cIAI, which we named pan-cIAI. It may enlarge the range of cIAI but can evoke more attention at the beginning of disease. The organ/system includes the kidney, liver, gut, respiratory system, hemodynamics, coagulation, consciousness, and so on. The anatomic structural abnormality can be the perforation of the hollow viscus, fluid collections or vascular erosion after IAI, pancreatic pseudocyst, and so on. Moreover, IAI is a dynamic process. The pan-cIAI can be turned into an uncomplicated IAI after the rectification of organ/system functions. Early recognition and intervention of organ/system dysfunction can prevent or delay the deterioration of IAI.

In conclusion, a proper definition of cIAI should be considered to attract enough attention from the clinician, especially when it comes to organ dysfunction. A timely improvement of organ function may benefit patients.