Abdominal Infections

Acalculous cholecystitis

Acalculous cholecystitis is uncommon but can be fatal if missed [J Intensive Care Med 9: 235, 1994]. It may present with fever (this may be the only sign), nausea, vomiting, abdominal pain, and RUQ tenderness. LFT elevations are variable [World J Surg 1160, 1992]. It is classically considered to be more common in elderly patients and those with significant comorbidity, but can also present in non-critical care settings and in younger patients, and so may be the reason for referral to critical care. It may occur in medically or surgically critically ill patients, and following trauma, cardiac surgery, or abdominal surgery. It is also associated with a number of viral infections. Initial treatment involves aggressive antibiotic therapy and should also include consideration of percutaneous cholecystostomy which can be life-saving. Cholecystectomy amy be carried out following resolution of the acute instability. AAC is associated with higher incidence of gangrenous gallbladder (up to 50%) and perforation (up to 10%) than calculous cholecystitis, and if treatment is delayed, the risk of perforation increases appreciably.

AAC may be suspected on clinical grounds by virtue of evidence of sepsis without other source. Patients may have no symptoms other than fever. Ultrasound is often used as an early diagnostic tool.

Ultrasound diagnostic criteria require either two major criteria, or one major criterion and two minor criteria from those listed below [Gastroenterology Clinics of North America, Volume 39, Issue 2, June 2010, Pages 343–357]:

Ultrasound Major criteria

  • Gallbladder wall thickening >3 mm
  • Striated gallbladder (ie, gallbladder wall edema)
  • Sonographic Murphy sign (inspiratory arrest during deep breath while gallbladder is being insonated; unreliable if patient is obtunded or sedated)
  • Pericholecystic fluid (absent either ascites or hypoalbuminemia)
  • Mucosal sloughing
  • Intramural gas

Ultrasound Minor criteria

  • Gallbladder distention (>5 cm in transverse diameter)
  • Echogenic bile (sludge)

CT may also be used, although there is some controversy over the specificity of CT findings. For CT, the diagnostic criteria are either two major criteria, or one major criterion and two minor criteria from:

CT Major criteria

  • Gallbladder wall thickening >3 mm
  • Subserosal halo sign (intramural lucency caused by edema)
  • Pericholecystic infiltration of fat
  • Pericholecystic fluid (absent either ascites or hypoalbuminemia)
  • Mucosal sloughing
  • Intramural gas

CT Minor criteria

  • Gallbladder distention (>5 cm in transverse diameter)
  • High-attenuation bile (sludge)


  1. Barie PS, Eachempati SR. Acute Acalculous Cholecystitis. Gastroenterology Clinics of North America 2010; 39: 343-357.


C.difficile can be cultured in up to 40% of hospitalized patients [Am J Med 70: 906, 1981] but more than half of those harboring this bacteria are asymptomatic [Ann Intern Med 117: 297, 1992; Am J Med 100: 32, 1996]. Clinical manifestations include fever, abdominal pain, watery diarrhea (only bloody in 5 – 10% of cases [NEJM 330: 257, 1994]). Toxic megacolon is a rare complication but when it occurs necessitates colectomy. C.difficile is easily transmitted by hospital hands and strict adherence to disposable gloves can significantly reduce transmission [Am J Med 88: 137, 1990]. Cultures can take > 48 hours, also they do not distinguish between the toxigenic from non-toxigenic forms, the cytotoxin assay is superior

Characteristics of Various C.Difficile Assays

Test Comments
Stool Culture Does not distinguish toxigenic from non-toxigenic
Cytotoxin (ELISA) Sensitivity 85% for one sample, 95% for two. Specificity 98%Treat with metro if: 1) severe diarrhea 2) systemic signs of infection 3) cannot stop Abx

Treatment of C.difficile

First, stop the offending antibiotics if possible. Treatment should only be necessary if the patient has severe diarrhea, systemic signs of infection, or you cannot stop antibiotic therapy. To treat C.difficile colitis, start with oral metronidazole 500 mg q6h x 7 days (avoid IV metro because it can contribute to VRE emergence). Surgical intervention can be required if sepsis, peritonitis, and/or MOF develop. Avoid antiperistaltic agents. Expect fever to resolve in 24 hours and diarrhea within 4-5 days [NEJM 346: 334, 2002]. Relapses occur in 25% of cases, but 75% of these will respond to the same antibiotic if repeated [Lancet ID 5: 549, 2005]

Prevention of C.difficile

Prevention is primarily by rational antibiotic use and possibly the use of probiotics (in one study, 1 g of lyophilized yeast PO qday lead to a 50% reduction in C.difficile colitis [Gastroenterology 96: 981, 1989]). A recent meta-analysis said that more definitive studies need to be complete before recommendations can be made [BMJ 324: 7350, 2002]. Another review concluded that L. rhamnosus GG and S. boulardii are effective in preventing antibiotic-associated diarrhea, and that S. boulardii in combination with susceptible antibiotics decreases recurrence of C.difficile infection [Best Pract Res Clin Gastroenterol 17:775, 2003]. However, a subsequent double-blind, controlled trial was inadequately powered to show significant benefit of adding L. plantarum 299v to metronidazole treatment of C.difficile (recurrence in 4 of 11 L. plantarum-treated vs 6 of 9 placebo-treated patients) [Scand J Infect Dis 35:365, 2003]. In elderly patients receiving antibiotics for various indications, the combination of Lactobacillus and Bifidobacterium species decreased C.difficile toxin-positive diarrhea to 2.9% compared with 7.3%in the placebo-treated group [Int Microbiol 7:59, 2004]. However, the overall rate of C.difficile toxin detection remained alarmingly high (46% with probiotics, 78% placebo) in unselected patients, including those without diarrhea. At the opposite end of the age spectrum, in a large prospective study of 465 patients 1 to 5 years of age receiving antibiotic treatment with sulbactam-ampicillin or azithromycin, S. boulardii decreased the rate of diarrhea from 18.9% (placebo) to 5.7% (p < 0.05) [J Trop Pediatr 50:234-236, 2004]. The combination of the probiotic (L. sporogens) and prebiotic (fructo-oligosaccharide) decreased the incidence of diarrhea in 120 children receiving clinically indicated antibiotics from 71% (placebo group) to 38% (combination probiotic/prebiotic group) and decreased the duration of the diarrhea from 1.6 to 0.7 days [Minerva Pediatr 55:447, 2003]. In vitro studies demonstrate that three nondigestible oligosaccharides enhanced growth of Bifidobacterium species while suppressing C.difficile in the presence or absence of clindamycin [Appl Environ Microbiol 69:1920, 2003]. Clinical applications of these promising results are limited by the lack of proper comparative studies with available probiotic preparations and dose-response studies

Abdominal Abscess

Abdominal abscesses generally follow trauma or abdominal surgery. They are difficult to detect clinically, often presenting with fever of unclear etiology. Localized tenderness may be present in as few as 33% of cases, with an abdominal mass in only 10% [Surg Clin North Am 74: 693, 1994]. Thus, CT scan is the most valuable diagnostic test – sensitivity and specificity are > 90% [J Intensive Care Med 9: 151, 1994]. In the post-op period blood and irrigant collections can be misread, thus one should wait until a week post-op before diagnosing with a CT scan [Surg Clin North Am 74: 693, 1994]

Utility (or lack thereof) of Clinical Exam in Intra-Abdominal Abscess

Clinical Finding Frequency
Localized abdominal tenderness (exam) 36%
Pleural Effusion (CXR) 33%
Extraluminal air or air-fluid level (KUB) 13%
Basilar atelectasis (CXR) 12%
Palpable abdominal mass (exam) 7%
Mechanical bowel obstruction (KUB) 4%

Surg Clin North Am 74: 693, 1994

Treatment is drainage, empiric antibiotic therapy while waiting culture results (monotherapy has been shown to be as effective as multi-drug therapy, consider UnaSyn, cefoxitin, and imipenem [Ann Surg 214: 543, 1991])