Laparotomy performed for both emergency of elective surgery may by complicated by intrabdominal collection, anastomotic leakage, infarction and others. This conditions are able to induce peritoneal inflammation. Inflamed peritoneum are able to produce excess of lactate that the investigators can measure by collecting fluid from peritoneal drainage.

Drainage were left in abdomen for monitoring intrabdominal condition until the passage of stool or flatus. Minimum drainage of serum is present daily also in uncomplicated post operative period.

Serum lactate relates with increased systemic anaerobic metabolism such as SIRS, sepsis and systemic hypoperfusion and it is easy to measure with a blood gas analysis.

The investigators hypothesized that the increases of peritoneal/ serum lactate ratio could be an earlier, sensible, non-invasive, and economical marker of post surgical complications. The decision whether and when to perform a relaparotomy in secondary peritonitis is largely subjective and based on professional experience. Actually no existing scoring system aids in this decision.

The aim of this study is to demonstrate that this ratio could be and useful tool for the surgeon in this decisional process.

Post operative intraabdominal sepsis due to surgical complications is associated with an important mortality and morbidity. Early diagnosis is crucial to improve outcome. Relaparotomy could be necessary to eradicate the intraabdominal focus of sepsis or hypoperfusion. The relaparotomy must be performed early after the diagnosis of surgical complications before the onset of multi organ failure.

This prospective observational study includes the post operative period of consecutive patients requiring both major elective surgery and urgent laparotomy.

Demographic data, presence and nature of underlying disease and surgical diagnosis will be recorded on admission and study inclusion.

Daily after study inclusion, the investigators measure: venous blood gases, blood lactate and lactate presents in the fluid collected from the abdomen. Possum and SAPSII scores will be calculated daily or when a patient develops a rapid clinical deterioration.

The investigators follow patients with complicated or uncomplicated post operative period.

Post operative complications are defined as: mesenteric ischemia, need for reintervention, anastomotic leakage or fistula, secondary peritonitis and death.

The primary end point is to demonstrate the correlation between surgical complications and serum/abdominal lactate ratio.

The second end point is to verify the correlation between need to relaparotomy and Possum an SAPSII scores.

Inclusion Criteria:

• Post operative period of abdominal surgery (elective surgery of:colon-rectum, ileum, stomach and, pancreas)
• Post operative period after Urgent laparotomy for both traumatic and/or non traumatic acute abdomen
• Patients with signs of sepsis in the post operative period
• Patients with signs of systemic hypoperfusion in the post operative

Exclusion Criteria:

• Liver surgery
• Drainage of bile, blood and dejection from abdominal drainage
• Sepsis/ systemic hypoperfusion due to extraabdominal infection site

Patients admitted to our surgery department for the post operative period after major abdominal surgery (neoplastic and non neoplastic) or urgent laparotomy for traumatic or non traumatic acute abdomen.