Post-operative peritonitis

Post-operative peritonitis (PP) is a life-threatening hospital-acquired intra-abdominal infection with high rates of mortality.  The most common cause of PP is anastomotic leakage. It is most frequent after rectal resection but it may complicate all gastrointestinal anastomosis.  Low risk anastomoses include small bowel and right hemicolectomy; whereas other high risk anastomoses include oesophageal, total gastrectomy and pancreatic. The prevalence of anastomotic leak has been reported to be between 0.5% and 21% after colon and rectal resections, although there is lack of a clear definition for what constitutes an anastomotic leak.

Leaks are generally  classified into:

  • Radiological leaks; which are detected on routine imaging and present with none or minimal clinical signs and don’t require any specific intervention.
  • Minor clinical leaks; which are detected by clinical features such as fever, leucocytosis, intestinal contents via an abdominal drain; faecal discharge via a wound or drain site; or a high drain amylase in the case of HPB leaks. Some of these leaks will not require any specific intervention other than antibiotics and observation; whereas others will require radiological drainage or other forms of reintervention; including eventual re-operation.   These leaks inevitably lead to a prolongation of hospital stay and a delay in reinitiating oral intake.
  • Major clinical leaks; which imply severe distruption to the anastomosis and require re-intervention (usually reoperation).These leaks are potentially life threatening and require prompt treatment.

The role of prophylactic drainage has been well studied in the setting of colorectal resections. Although routine pelvic drainage in colorectal surgery has not been justified by evidence based medicine, and some reports even showed that drain itself is an independent risk factor for anastomosis leakage. Nevertheless, the choice of using drain is left to the individual surgeon’s preference in daily practice. Many surgical institutes routinely use pelvic drains after anterior resection because discoloured or enteric contents may be an early indicator of anastomotic leak. After a low rectal resection a defunctioning protective stoma may be created to minimize the impact of any anastomotic leak. The role of defunctioning protective stoma has been debated in the last years. It seems not influence the leak rate after low rectal resection, but it can mitigate clinical consequences.

In the absence of RCTs, there is expert level consensus to suggest that prophylactic drainage after esophageal resection and total gastrectomy due to the potential fatal outcome in case of anastomotic leakage in this setting.

The diagnosis of postoperative peritonitis may be difficult because there are no specific clinical signs and laboratory tests to reject or confirm the diagnosis. The atypical clinical presentation may be responsible for a delay in diagnosis and reintervention or reoperation. For example, post-operative delirium and cardiac arrthymias (such as AF) are increasingly recognised to be due to septic complications, including PP. Moreover, in patients already stressed by the previous operation, sepsis can escalate very quickly. Therefore an early diagnosis and prompt treatment is crucial to prevent the development of organ failure and improve the outcome of the patients with PP. There are many factors which conspire against the surgeon making an early diagnosis. For example, during the early postoperative period  sepsis can be difficult to distinguish from the normal post-operative inflammatory response to the operation. Other reasons, including the difficulty in clinically assessing the post-operative abdomen (due to epidural or opiate analgesia masking signs, post-operative delirium or confusion, drain sites or wound pain ) or intubation and ventilation on the ICU all cause difficulty in establishing a diagnosis.

Once anastomotic leakage or secondary peritonitis is suspected clinically, further investigations are necessary to confirm the presence and source of peritonitis.

In few instances of postoperative peritonitis, the anastomosis may be intact; however, the patient may have residual peritonitis. Reasons for this include the inadequate drainage of the initial septic focus or more commonly, the host does not have the sufficient defense capacity to control the causative infectious process. In other scenarios post-operative collections may be the result of infected hematomas or a small, tiny pin hole leak has closed.

The management of anastomotic leak mainly depends on both the clinical status of the patient.

In minor leaks with sub-clinical forms, in absence of significant sepsis, conservative management with antibiotics, total parenteral nutrition and adequate resting of the bowel is an acceptable treatment option.  These patients must be closely monitored, as deterioration in their clinical state requires urgent surgical intervention.

In stable patients localised abscess cavity can be drained under CT guidance.

Management of diffuse post-operative peritonitis is more complex. The timing and adequacy of source control are of outmost importance, as late and/or incomplete procedures may have severe adverse consequences.  All sources of contamination should be removed from the peritoneal cavity. Alternatively gastrointestinal transit should be excluded with the use of a diverting stoma. Adequate intra-peritoneal drainage should be performed.  Any attempt at anastomosis revision or salvage should generally be avoided because the risk of leakage is unacceptably high.

Surgical strategies of re-laparotomy include both “re-laparotomy on demand” (when required by the patient’s clinical condition) and planned re-laparotomy in the 36-48-hour post-operative period (when re-laparotomy is planned after first operation) . The open abdomen procedure is the easiest means to perform a planned re-laparotomy is now a viable option for treating critically ill patients with severe intra-abdominal sepsis. Open abdomen approach may be useful required for extending the concept of damage control surgery to critical patients preventing the appearance of the abdominal compartment syndrome. However the use of the open abdomen, although a lifesaving technique, presents a clinical challenge because it may be associated with significant morbidity.

In patients with postoperative peritonitis, intra-abdominal infections may be caused by several unexpected pathogens and by more resistant flora, which may include, Enterococci, extended-spectrum β-lactamases producing  Enterobacteriaceae (ESBLs) and Candida spp. Antimicrobial therapy between initial intervention and reoperation seems to be a  significant risk factor for emergence of multidrug resistant pathogens in patients with PP. The threat of antimicrobial resistance has been identified as one of the major challenges in the management of post-operative peritonitis. In these infections empiric antimicrobial regimens with broad spectrum of activity are recommended with the intent to cover the most likely pathogens, basing on local surveillance data and risk factors for resistant microorganisms. In this era of prevalent drug-resistant microorganisms, the threat of resistance is a source of major concern that cannot be ignored. In the past 20 years, the incidence of nosocomial infections caused by drug-resistant microorganisms has risen dramatically, probably in correlation with escalating levels of antibiotic exposure and increasing frequency of patients with one or more predisposing conditions, including elevated severity of illness, advanced age, degree of organ dysfunction, low albumin levels, poor nutritional status, immunodepression, presence of malignancy, and other comorbidities. In the event of intra-abdominal infection the main problem with antimicrobial resistance is posed by ESBL-producing Enterobacteriaceae. Empiric therapy directed against ESBL producers should be always recommended in post-operative  peritonitis.  Enterococci are pathogenic microorganisms that may play an important role in peritonitis and have been a subject of debate in recent years and also empiric antimicrobial therapy directed against enterococci is always recommended in patients with post-operative peritonitis.

Postoperative peritonitis is a life-threatening hospital-acquired intra-abdominal infection with high rates of mortality. Early and aggressive management of the problem can lead to satisfactory outcomes; however when the diagnosis is late or the treatment insufficient or delayed the consequences (excessive morbidity and mortality) are high. Therefore, early diagnosis and treatment is crucial to improve the outcome for  patients.

Reference

Sartelli M, Griffiths EA, Nestori M. The challenge of post-operative peritonitis after gastrointestinal surgery. Updates Surg. 2015 Dec;67(4):373-81.