From a clinical viewpoint, intra-abdominal infections can be divided into: uncomplicated and complicated. In uncomplicated intra-abdominal infections, the infectious process only involves a single organ and no anatomical disruption is present. Generally, patients with such infections can be managed with surgical resection alone and no antimicrobial therapy besides perioperative prophylaxis is necessary. In complicated intra-abdominal infections (cIAIs), the infectious process proceeds beyond the organ that is the source of the infection, and causes either localized peritonitis (often referred to as abdominal abscess) or diffuse peritonitis, depending on the ability of the host to contain the process within a part of the abdominal cavity. Complicated IAIs usually require both an invasive surgical procedure for source control and antimicrobial therapy.
Complicated IAIs remain a major challenge in clinical practice having significant morbidity and mortality.
Results of prospective trials have often overestimated the outcomes of patients with cIAIs. Treatment of patients who have cIAIs by adequate management, has generally been described to produce satisfactory results; recent clinical trials have demonstrated an overall mortality of 2% to 3% among patients with cIAIs.
However, results from published clinical trials may not be representative of the true morbidity and mortality rates of such infections. Patients who have perforated appendicitis are usually over represented in clinical trials. Furthermore patients with cIAIs enrolled in clinical trials have often an increased likelihood of cure and survival. In fact trial eligibility criteria often restrict the inclusion of patients with co-morbid diseases that would increase the death rate of patients with intra-abdominal infections.
After excluding patients with perforated appendicitis, Merlino et al. found that the cure rate among patients who had intra-abdominal infections and were enrolled in clinical trials, was much higher than that of patients who were not enrolled (79% versus 41%) and that the mortality rate was much lower (10% versus 33%).
Epidemiological studies of patients with cIAIs including severely ill subjects, have demonstrated higher mortality rates.
The CIAO Study (“Complicated Intra-Abdominal infections Observational” Study) is a multicenter study performed in 69 medical institutions throughout Europe over the course of a 6-month observational period (January – June 2012). In the CIAO study the overall mortality rate was 7.7% (166/2152).
The CIAOW Study (“Complicated Intra-Abdominal infection Observational” Study worldwide) is a multicenter investigation performed in 57 medical institutions worldwide over the course of a 6-month observational period (October 2012 – March 2013). In the CIAOW study the overall mortality rate was 10.5% (199/1.898).
The most significant independent variables predictive of patient mortality proved by both CAIO and CIAOW Study, adjusted to clinical criteria, were used to create a severity score for patients with cIAIs. In order to validate the new practical Sepsis Severity Score for patients with cIAIs including the clinical conditions at the admission (severe sepsis/septic shock), the origin of the cIAIs, the delay in source control, the setting of acquisition and any risk factors such as age and immunosuppression, between 2014 and 2015, the World Society of Emergency Surgery designed a new prospective observational study. The WISS study (WSES cIAIs Score Study) is a multicenter observational study underwent in 132 medical institutions worldwide during a four-month study period (October 2014-February 2015). Four thousand five hundred thirty-three patients were enrolled in the WISS study. The overall mortality rate was 9.2 % (416/4533).
The score is illustrated below. The statistical analysis shows that the sepsis severity score has a very good ability of distinguishing those who survived from those who died. The overall mortality was 0.63 % for those who had a score of 0–3, 6.3 % for those who had a score of 4–6, 41.7 % for those who had a score of ≥ 7. In patients who had a score of ≥ 9 the mortality rate was 55.5 %, those who had a score of ≥ 11 the mortality rate was 68.2 % and those who had a score ≥ 13 the mortality rate was 80.9 %.
Clinical condition at the admission
Severe sepsis (acute organ dysfunction) at the admission 3 score
Septic shock (acute circulatory failure characterized by persistent arterial hypotension.
It always requires vasopressor agents) at the admission 5 score
Setting of acquisition
Healthcare associated infection 2 score
Origin of the IAIs
Colonic non-diverticular perforation peritonitis 2 score
Small bowel perforation peritonitis 3 score
Diverticular diffuse peritonitis 2 score
Post-operative diffuse peritonitis 2 score
Delay in source control
Delayed initial intervention [Preoperative duration of peritonitis
(localized or diffuse) > 24 h)] 3 score
Age>70 2 score
Immunosuppression (chronic glucocorticoids, immunosuppresant agents,
chemotherapy, lymphatic diseases, virus) 3 score
Patients with cIAIs should be stratified into different risk groups for mortality based on predictable clinical parameters and comorbid conditions.
The management of lower-risk patients with intra-abdominal infections is distinct compared with patients at higher risk due to compromised physiological status, extent of intra-abdominal infection, or presence of nosocomial pathogens associated with higher-risk patients.
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