**3. Infected pancreatic necrosis**

The most important consideration in treating local complications is to demonstrate the presence of infection.

Because the majority of patients with sterile pancreatic or peripancreatic necrosis can be treated conservatively, regardless of the size and extension of the collections.

Drainage in a sterile collection can produce iatrogenic infection, worsening the patient's prognosis. Could only be an alternative in those patients with persistent symptoms such as abdominal pain, duodenal obstruction or jaundice [13, 14].

Necrosis infection usually occurs within 2–3 weeks of the onset of BP. Successive CT scans should be performed according to the evolution of the patient and not in a programmed way. Early onset is rare, and should be suspected if SIRS persists or recurs after 10 days-2 weeks [15]. Therefore, the suspicion of infection will be made according to the bad evolution of the patient: fever, increase of leukocytes, elevation of

### **Figure 2.**

*CT scan image showing radiological signs of pancreatic necrosis due to the presence of gas in the acute necrotic collection.*

PCR and/or procalcitonin, sudden resurgence or worsening of FO. This clinical evolution can be given by sterile necrosis, and it is often a challenge to differentiate whether we are dealing with an infected necrosis or not. Given this scenario, CT has high sensitivity to detect signs of infection (gas in the collection only appears in 12–22% of infected cases (**Figure 2**). However the signs of infection are usually sufficient to diagnose a secondary infection of pancreatic or peripancreatic necrosis. In case of diagnostic uncertainty, a positive gram stain or culture of the necrotic collection, obtained by transabdominal fine needle aspiration, may be necessary. However, the disadvantage of fine needle aspiration in this scenario is the false negative rate of 25% [16].
