Pyogenic Abscess

 Occurs via portal vein, arterial system, or bile ducts






Etiology/Pathogenesis




• Bacterial pathogens most common in Western countries
image Klebsiella pneumoniae is now most common pathogen, followed by Escherichia coli

image Anaerobes are isolated in up to 25% of cases

image Significant number are cryptogenic


Clinical Issues




• Diabetes is major risk factor
image Other associated conditions include intraabdominal infections, biliary disease, malignancy, cirrhosis

• Presentation includes fever, chills, RUQ pain
image Elevated WBC count, ESR, CRP, bilirubin, alkaline phosphatase, transaminases

• Percutaneous drainage and antibiotics are mainstay of therapy

• Major complication is spread of infection

• Mortality ∼ 15% overall


Imaging




• Ultrasound &/or CT mainstay of diagnosis


Macroscopic




• Most abscesses are solitary; multiple abscesses occur in 25-45% of cases
image Right lobe most frequent site


Microscopic




• Abundant neutrophils, fibrin, and bile with associated fibrosis


Diagnostic Checklist




• Culture of abscess contents is critical to diagnosis and management

image
Gross Appearance
This partial hepatectomy specimen shows 2 large, irregular, yellow-tan abscesses with central green bile-stained necrosis.


image
Abscess With Bile
This section of a large liver abscess shows irregular zones of inflammation and necrosis with associated bile. Another smaller abscess containing bile is present at the top of the section image .

image
Necrosis and Acute Inflammation
In this region of the abscess, necrotic liver parenchyma is identifiable by the ghosts of residual hepatic plate architecture image. The necrotic parenchyma is infiltrated with neutrophils.

image
Fibrosis
Fibrosis may be very prominent, particularly at the edge of an abscess image, as seen in this actinomycotic abscess. Marked acute and chronic inflammation are also present.


TERMINOLOGY


Definitions




• Infection featuring localized accumulation of pus with surrounding inflammation and fibrosis
image Occurs via portal vein, arterial system, or bile ducts


ETIOLOGY/PATHOGENESIS


Predisposing Conditions




• Diabetes is major risk factor
image Other predisposing conditions include malignancy, alcohol abuse, cirrhosis, hypertension, recent surgery, immunosuppression

image Abscesses secondary to Yersinia enterocolitica or Yersinia pseudotuberculosis are often associated with underlying hemochromatosis

• Biliary disease
image Including biliary ischemia secondary to surgery or ablative procedures

• Trauma

• Intraabdominal infections

• Secondary to sepsis

• Significant number are cryptogenic


Epidemiology




• Bacterial abscesses are most common in Western countries
image Klebsiella pneumoniae is now most common pathogen, followed by Escherichia coli

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Apr 20, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Pyogenic Abscess

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