New Tool for Infection Risk After Colorectal Surgery

Kate O'Rourke

March 08, 2016

BOSTON — Researchers say they have developed a tool that can identify patients at low risk of developing intra-abdominal infections after colorectal resection. The tool may help to identify candidates for early hospital release.

"The current risk assessment for IAI [intra-abdominal infection] is inadequate," said Eran Sadot, MD, a fellow at Memorial Sloan Kettering Cancer Center (MSKCC), New York City.

He presented the tool here at the Society of Surgical Oncology (SSO) 2016 Cancer Symposium. The intra-abdominal infection risk prediction model uses five factors, including hypophosphatemia, or low phosphate level (< 2.5 mg/dL), which is considered a novel indicator of infection risk.

Dr Sadot explained why a predictive tool would help in this setting.

He said that between 5% and 15% of patients who undergo colorectal surgery develop intra-abdominal infections, including anastomotic leaks, fistulas, and intra-abdominal abscesses.

These infections, which typically become evident 5 days after surgery, are associated with prolonged hospital stays and higher costs, as well as an increase in short-term mortality and a decrease in long-term survival. Early identification of these infections can lead to early interventions to limit sepsis. Importantly, patients at low risk for the infections may be candidates for early discharge.

To identify risk factors for intra-abdominal infections, the researchers analyzed data from 7423 patients who underwent a first colorectal resection at MSKCC between 2005 and 2015.

The main indications for surgery were colon cancer (42%) and rectal cancer (26%). Intra-abdominal infections occurred in 5% of patients.

The researchers identified five independent predictors of intra-abdominal infections: hypophosphatemia on day 3 post surgery, abnormal white blood count on day 3 post surgery, body mass index more than 30 kg/m2, combined liver surgery, and estimated blood loss of more than 400 mL. Hypophosphatemia at day 3 was independently associated with a 40% increase in intra-abdominal infections; abnormal white blood count on day 3 was associated with a 90% increased risk.

The researchers used these factors to develop a risk score that categorizes patients as being at low risk, moderate risk, or high risk for intra-abdominal infections. Compared with the low-risk group, moderate- and high-risk cohorts had double and triple the rates of intra-abdominal infections (5%, 10%, and 17%, respectively; P < .001). "The negative predictive value for this model was 95%," said Dr Sadot.

Table. Intra-abdominal Infections Risk Score

Risk Score Predicted Risk for Intra-abdominal Infection Risk Group Predicted Risk for Intra-abdominal Infection
0 5% Low 5%
1 5%    
2 9% Moderate 10%
3 15%    
4 17% High 17%
5 21%    
Risk score assigns one point for any of the following: hypophosphatemia on day 3 post surgery, abnormal white blood count on day 3 post surgery, body mass index >30 kg/m2, combined liver surgery, and estimated blood loss >440mL,


"The IAI risk prediction model that includes this variable, hypophosphatemia, accurately identified low-risk patients, which are ideal candidates for early discharge," said Dr Sadot.

He noted that early postoperative hypophosphatemia has been shown to be associated with poor outcomes in various patient populations, but the association between hypophosphatemia and intra- abdominal infections after colorectal resection is a novel finding.

Dr Sadot also said that the model may be used in conjunction with enhanced recovery after surgery protocol pathways to safely reduce hospital length of stay.

Sandra Wong, MD, a surgeon at Dartmouth-Hitchcock Medical Center, in New Hampshire, said the study was interesting but left her with more questions than answers.

"The finding is novel — hypophosphatemia has not been evaluated in the context of anastomotic leak or intra-abdominal abscess," she said. "There has been interest in hypophosphatemia following liver resection (with an association to hyperphosphaturia), with varying implications for clinical outcomes."

She pointed out that the tool was derived from retrospective data, and more questions need to be answered before the tool could be useful in clinical practice.

"What is the impact of [phosphate] replacement therapy, and what data should guide degree of replacement?" asked Dr Wong. "The main questions include how predictive this lab value is over other clinical signs and if early prediction can help with rescue before more serious complications occur or if such rescue can mitigate the severity of a possible complication."

Society of Surgical Oncology (SSO) 2016 Cancer Symposium: Abstract 82, presented March 6, 2016.


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