Abdominal Infections
This chapter describes abdominal infections that you are likely to encounter in the ICU, including infections of the biliary tree (acalculous cholecystitis), bowel (Clostridium difficile infections), and peritoneal cavity (postoperative infections).
I. Acalculous Cholecystitis
Acalculous cholecystitis accounts for less than 15% of cases of acute cholecystitis (1), but it is more common in critically ill patients, and it has a mortality rate (about 45%) that rivals septic shock (1,2).
A. Predisposing Conditions
Common conditions associated with acalculous cholecystitis include the postoperative period, trauma, circulatory shock, and prolonged bowel rest (4 weeks or longer) (1,2).
Bowel rest during total parenteral nutrition (TPN) is usually less than 4 weeks in duration, so TPN should not be a risk factor for acalculous cholecystitis (3).
Possible mechanisms include hypoperfusion, gallbladder distension from diminished contractions, and a change in the composition of bile.
B. Clinical Features
Right upper quadrant pain and tenderness are common,
but can be absent in one-third of patients with acalculous cholecystitis (4).
Other common findings include fever (100%), elevated bilirubin (90%), hypotension (90%) and multiorgan failure (65–80%) (1,2).
Blood cultures are positive in 90% of cases (4) and gram-negative aerobic bacilli are isolated in almost all cases.
C. Diagnosis
Ultrasound is the favored diagnostic test for acalculous cholecystitis.
Sonographic features include distension of the gallbladder (diameter >40 mm in the short-axis view), wall thickening (>3 mm), and the presence of sludge (a mixture of particulate matter that has precipitated from bile) (5). These features are shown in Figure 32.1. The presence of sludge is nonspecific, and is seen in critically ill patients without cholecystitis.
D. Management
Empiric antibiotic therapy should be started as soon as the diagnosis is confirmed. The recommended antibiotics are piperacillin-tazobactam, or a carbapenem (e.g., meropenem) (2). (See Chapter 44, Sections III and VI for dosing recommendations.)
Laparoscopic cholecystectomy is favored in clinically stable (non-ICU) patients, but percutaneous cholecystostomy
is the safest and most successful intervention in critically ill patients (7).
 FIGURE 32.1 Sonogram showing a short-axis view of the gallbladder in a patient with acalculous cholecystitis. See text for explanation. |
II. Clostridium Difficile Infection
Clostridium difficile infection (CDI) is the most common healthcare-associated infection in the United States, and is also the leading cause of nosocomial diarrhea worldwide (8). The incidence of CDI almost doubled during the past decade (9).
A. Pathogenesis
C. difficile is a spore-forming, toxin-producing, gram-positive, anaerobic bacillus. It does not inhabit the bowel in healthy subjects, but colonizes the bowel when the normal microflora has been altered (e.g., by antibiotic therapy).
CDI is transmitted via the fecal-oral route, and patient-to-patient transmission occurs on the hands of hospital personnel. The use of disposable gloves for patient contact reduces the transmission of CDI (10).
C. difficile is not an invasive organism, but releases cytotoxins that damage the bowel mucosa. This leads to inflammatory infiltration of the bowel wall and a secretory diarrhea. Severe inflammation produces raised, plaque-like lesions on the mucosal surface of the bowel. These are called “pseudomembranes,” and the condition is called pseudomembranous colitis.
Antibiotic use is the most noted risk factor for CDI, but gastric acid suppression is emerging as a significant risk factor because it promotes the fecal-oral transmission of C. difficile (see next).
5. Gastric Acid Suppression
Gastric acidity plays a major role in eradicating organisms that invade the upper GI tract (see Chapter 3, Section I-C-3, and Figure 3.1), and there are several reports showing an increased incidence of CDI associated with the use of acid-suppressing drugs, particularly proton pump inhibitors (11,12,13). In fact, the marked increase in the incidence of CDI mentioned earlier coincides with the marked increase in the use of proton pump inhibitors for prophylaxis of stress ulcer bleeding, and it is possible that the recent surge in frequency and severity of CDI is a reflection of the escalating use of proton pump inhibitors in hospitalized patients (14).
B. Clinical Features
The clinical features of CDI are shown in Table 32.1. The information in this table is taken directly from the most recent clinical practice guidelines on CDI (15). The following points deserve mention:
The diarrhea in CDI is watery (not grossly bloody), and is often foul-smelling.
Toxic megacolon is a life-threatening complication of CDI. Clinical features include the abrupt onset of ileus and marked abdominal distension, with rapid progression to circulatory shock. Emergent surgical intervention is mandatory, and the preferred surgical procedure is subtotal colectomy (8).Related posts:
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