Abdominal Abscess Treatment & Management

Antibiotic therapy involves the administration of parenteral empirical antibiotics. Begin therapy prior to abscess drainage, and conclude therapy when all systemic signs of sepsis have resolved. Because abscess fluid usually contains a mixture of aerobic and anaerobic organisms, direct initial empiric therapy against both sets of microbes. This may be accomplished with antibiotic combination therapy or with broad-spectrum, single-agent therapy. Specific therapy is then guided by the results of cultures retrieved from the abscess.^[3]

In patients who are immunosuppressed, candidal species may play an important pathogenic role, and treatment with amphotericin B may be indicated.

Drainage

Drainage of pus is mandatory and is the first line of defense against progressive sepsis. Percutaneous CT-guided catheter drainage has become the standard treatment of most intra-abdominal abscesses. It avoids possibly difficult laparotomy, requires anesthesia, prevents the possibility of wound complications from open surgery, and may reduce the length of hospitalization. It also obviates the possibility of contamination of other areas within the peritoneal cavity. CT-guided drainage delineates the abscess cavity and may provide safe access for percutaneous drainage. When performed by experienced hands, it also prevents the possibility of injury to adjacent viscera or blood vessels.^{[7, 8]}

A diagnostic needle aspiration initially is performed to confirm the presence of pus, which makes performing Gram stain and culture possible. A large-bore drainage catheter is then placed in the most dependent position. In patients who are critically ill, initial percutaneous drainage can control sepsis and improve hemodynamics prior to definitive surgical treatment (if this becomes necessary). Initial catheter drainage also may drain a peridiverticular abscess enough to make a single-stage resection and bowel anastomosis possible, thus avoiding multiple-stage procedures. A visualized collection may be sterile (eg, bile, hematoma) or infected, and CT-guided aspiration is most helpful in distinguishing between these states.^[9]

After surgical drainage, clinical improvement should occur within 48-72 hours. Lack of improvement within this time frame mandates a repeat CT scan to check for additional abscesses. Surgical drainage becomes mandatory if residual fluid cannot be evacuated with catheter irrigation, manipulation, or additional drain placement.

Criteria for removal of percutaneous catheters include resolution of sepsis signs, minimal drainage from the catheter, and resolution of the abscess cavity as demonstrated by an ultrasonogram or a CT scan. Persistent drainage usually reflects the presence of an enteric fistula, and a CT scan with contrast should be performed. Frequently, this fistula can be documented by sinography.

Complications of percutaneous drainage include bleeding or inadvertent puncture of the GI tract.

Percutaneous drainage is effective in 90% of patients who have a single unilocular abscess with no enteral communication. Complex abscesses that include multiple loculations or interloop abscesses or those associated with an enteric fistula may require surgery.

Surgical intervention also may be indicated for abscesses with tenacious contents, such as infected hematoma, infected pancreatic necrosis, or fungal abscesses.

Surgical intervention

Surgical drainage is an option if percutaneous drainage fails or if collections are not amenable to catheter drainage. The surgical approach may be either laparoscopic drainage or open (laparotomic) drainage.

Laparoscopic drainage for a massive intra-abdominal abscess is minimally invasive, permitting exploration of the abdominal cavity without the use of a wide incision; purulent exudate can be aspirated under direct vision.^[10]

With accurate preoperative localization, direct open surgical drainage may be possible through an extraperitoneal open approach. This technique reduces the risk of bowel injury, contamination spread, and bleeding. It also allows for a faster return of bowel function.

The transperitoneal open approach is made safer by the judicious use of preoperative antibiotics. Although contamination of otherwise uninfected sites remains a major concern, this complication is particularly reduced if the organisms involved are sensitive to the chosen drugs. Transabdominal exploration of the entire peritoneal cavity allows fibrin debridement. It also permits complete bowel mobilization to locate and drain all synchronous abscesses, which occur in as many as 23% of patients.

Transperitoneal exploration is indicated for multiple abscesses not amenable to CT-guided drainage, such as interloop collections or an enteric fistula feeding the abscess. In the latter situation, draining the abscesses with an enteric communication may be possible for several days prior to performing a laparotomy to control the fistula. This may allow some resolution of the inflammatory process, thus making surgery less difficult.

Pelvic abscesses often are palpable as tender, fluctuant masses impinging on the vagina or rectum. Draining these abscesses transvaginally or transrectally is best to avoid the transabdominal approach.

During the course of a laparotomy, the surgeon must use digital or direct exploration to be certain that all loculations are broken down and that all debris (eg, hematoma, necrotic tissue) is evacuated. Irrigation must be complete, and a Penrose or sump drain should be placed to allow continued evacuation and collapse of the abscess cavity postoperatively.

Improved clinical findings within 3 days after treatment indicate successful drainage. Failure to improve may indicate inadequate drainage or another source of sepsis. If left untreated, the septic state inevitably produces multiple organ failure.

The transabdominal open approach to intra-abdominal abscesses can be exceedingly difficult. Matted bowel, adhesions, and loss of anatomical integrity can pose severe problems. This is especially true when susceptible viscera, such as a loop of small bowel, intermittently adhere to the abscess wall or cavity. Therefore, whenever possible, CT-guided drainage is a valuable initial step.

For excellent patient education resources, visit eMedicine's Infections Center. Also, see eMedicine's patient education articles Abscess and Antibiotics.

The introduction of CT scanning for the diagnosis and drainage of intra-abdominal abscesses has led to a dramatic reduction in mortality rates. (See images below.) Sequential, multiple system organ failure is the main cause of death. Incidence of death is correlated to the severity of the underlying cause, a delayed diagnosis, inadequate drainage, and unsuspected foci of infection in the peritoneal cavity or elsewhere. Risk factors for morbidity and mortality are multiple surgical procedures, age older than 50 years, multiple organ failure, and complex, recurrent, or persistent abscesses.^{[1, 11]}