eventually leading to multi-organ system failure. To this end, further scoring systems have
been developed to determine the probability that tertiary peritonitis is in fact present
postsurgically. Two such systems, the Sepsis-Related Organ Failure Assessment and the Goris
scores, attempt to objectively sum the failure of the respiratory, cardiovascular, nervous, renal,
hepatic, and coagulation systems. Even though first postoperative day scores are elevated in
patients both with and without tertiary peritonitis, subsequent second and third day scores are
seen to fall in those without the disease, whereas remaining steady in patients later diagnosed
by reoperation with tertiary peritonitis (4). Although these findings may be interesting and
statistically significant, their clinical application—in overall terms of mortality avoided—
remains to be proven. By pausing for evidence of changing widespread system failure over
time, the clinician risks losing the opportunity to avoid medical catastrophe.
Radiologic tools, then, become a mainstay of the physician’s investigation. Two such
studies, gallium-67 (Ga-67) scintigraphy and computed tomography (CT) scan, are commonly
used for the detection of intra-abdominal infection. On the whole, CT is generally the preferred
choice. At 97.1% accuracy, it is the more accurate of the two, with an enviable specificity of
100%. Isotope scans suffer in terms of accuracy for the postoperative patient because of false-
positive uptake in areas of surgical injury. Moreover, CT has the potential to contribute both
diagnostically and therapeutically in the care of patients, as will be discussed later. Finally, CT
may be done on demand, whereas Ga-67 scintigraphy requires one to two days for
concentration of the isotope at the site of infection. Scintigraphy, however, is not entirely
without its own merits.
With a sensitivity of 100% relative to 93.7% for CT, it is superior for uncovering early
infection prior to the development of discreet fluid collections. Also, it is worth considering
that in centers where indium-111 (In-111) and technitium-99m (Tc-99m) exametazine-labeled
leukocyte scans are available, a higher level of scintigraphy accuracy may be attained, albeit at
greater expense. Furthermore, as an incidental advantage, nucleotide scanning has been
known to reveal extra-abdominal infections such as pneumonia and cellulitis that might
imitate tertiary peritonitis (5). Therefore, one might consider this as a second option for the
relatively stable patient, in which CT has failed to provide a definitive answer but signs and
symptoms persist. Other studies, such as plain film, are impaired by the nonspecific finding of
intra-peritoneal free air and other features that might normally be expected in the
postoperative patient (6).
Microbiology and Pathogenesis
The flora of tertiary peritonitis is different from that of secondary peritonitis. Whereas a culture
of secondary peritonitis might produce a predominance ofEscherichia coli, streptococci, and
bacteroides—all normal gut flora—tertiary peritonitis is more apt to culturePseudomonas,
coagulase-negativeStaphylococcus,Enterococcus, andCandida(7,8). The obvious explanation for
these differences is the mode of infection: secondary peritonitis is typically community
acquired, but tertiary peritonitis occurs in an ICU setting. Time spent in the ICU necessarily
implies that the patients affected are critically ill and likely already treated with antimicrobials.
Some theorize that disease begins when the gut is weakened by surgical manipulation,
hypoperfusion, antibiotic elimination of normal gut flora, and a lack of enteral feeding, thereby
creating an opportunity for selected resistant native bacteria to translocate across the mucosal
border (9). In fact, independent risk factors for postsurgical enterococcal infection include
APACHE II scores greater than 12 and inadequate antibiotic coverage (8). Therefore, empiric
antibiotic therapy should be broadly launched to cover the wide range of likely organisms, and
later targeted to the specific determined pathogen and sensitivity. Appropriate first agents
include, among others, carbapenems or the anti-pseudomonal penicillins, or a regimen of
aminoglycosides with either clindamycin or metronidazole for the penicillin-allergic patient (6).
Treatment
When possible in selected patients, the treatment of tertiary peritonitis may be accomplished
by image-guided percutaneous drainage of intra-abdominal abscesses, generally using CT.
Percutaneous drainage is not without its inconveniences: complications such as fistulas,
cellulitis, and obstructed, displaced, or prematurely removed drains occur in 20% to 40% of
Intra-abdominal Surgical Infections and Their Mimics in Critical Care 261