You evaluate an otherwise healthy 56-year-old man in the emergency department with a 4-day history of worsening left lower quadrant abdominal pain and fever. He has no evidence of peritonitis or sepsis. Computed tomography (CT) imaging of the abdomen and pelvis reveals sigmoid diverticulitis without abscess. The patient is admitted for a trial of bowel rest and broad-spectrum intravenous antibiotics. After 48 hours, the patient worsens clinically and undergoes sigmoid colectomy, end colostomy, and oversewing of the distal rectal stump (Hartmann procedure).
Six days later, while on call for the general surgery service, you are asked to evaluate the same patient who has been recovering uneventfully until now. He complains of new mild pelvic discomfort, anorexia, and difficulty voiding. His bowel function has not yet returned. He has a low-grade fever, mild tachycardia, and moderate right lower quadrant tenderness to deep palpation. A CBC with differential reveals leukocytosis with neutrophil predominance. CT of his abdomen and pelvis with oral and intravenous contrast reveals a 6-cm rim-enhancing pelvic fluid collection surrounding the rectal stump (see Figure 17-1).
Axial CT of a postoperative pelvic fluid collection.
1. Does this patient have an abscess or does he have a phlegmon?
2. Would this fluid collection be classified as primary, secondary, or tertiary?
An intra-abdominal abscess (IAA) is a contained collection of infected fluid within the confines of the peritoneal cavity, with or without associated pockets of gas. A phlegmon, in contrast, is an inflammatory mass without identifiable fluid. The patient in the case vignette has IAA.
There are several ways to classify IAA, although the etiologic classification is the most common:
- Primary IAAs are monomicrobial infections that arise spontaneously without any identifiable breach of the gastrointestinal tract. Spontaneous bacterial peritonitis is an example of a primary IAA.
- Secondary IAAs result from spontaneous, surgical, or iatrogenic violation of the gastrointestinal tract and account for the overwhelming majority of abscesses encountered by the surgeon. Diverticular abscesses are a common example of secondary IAA.
- Tertiary IAAs are recurrent infections following treatment of primary or secondary abscesses. These recalcitrant IAAs typically contain antibiotic-resistant nosocomial infections.
Given the relative infrequency of primary and tertiary abscesses, this chapter will focus on secondary IAA, and more specifically on intraperitoneal secondary IAA, which is present in the patient in the case vignette.
IAA may present with a wide range of clinical manifestations. Classic findings for spontaneous IAA include fever, lethargy, leukocytosis, and abdominal pain or fullness. Rarely, IAA may present with overt peritonitis or sepsis. The local inflammation can cause changes in bowel habits, including nausea, vomiting, diarrhea, or constipation. Similarly, a prolonged postoperative ileus can often be the initial manifestation of postoperative IAA, as is the ...
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