Hepatic abscesses

Posted By Wael Nemattalla
Hepatic abscesses

55 years old male with fever and right upper quadrant pain.

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  • Wael Nemattalla 2014-01-01 12:50:46

    Hepatic abscess





    Hepatic abscesses, like abscesses elsewhere, are localised collections of necrotic inflammatory tissue caused by bacterial, parasitic or fungal agents 1.





    Epidemiology and pathology

    The frequency of individual infective agents as causes of liver abscesses are intimately linked to the demographics of the affected population.

    In developing countries, parasitic abscesses are most common, including 2 :

    • amoebae (anchovy paste appearance of drained contents)

    • echinococcal (hydatid disease of the liver)

    • protozoa

    • helminiths

    In developed countries, liver abscesses are rare in healthy individuals, with imported infections from visits overseas accounting for the majority of cases. In 'home grown' cases, bacterial abscesses are most common, usually in the setting of co-morbidity such as:

    • infection elsewhere (most common)

    o abdominal sepsis most common 1

    • immunocompromised

    o diabetes mellitus found in up to 15% of patients with hepatic abscess 1

    o HIV/AIDS

    o elderly

    o chemotherapy / transplant recipients

    o malignancy

    • trauma

    • ERCP 3

    • cryptogenic : 15% 1

    Most abscesses in this setting are polymicrobial, with the most common bacterial agents are 1:

    • gram negative aerobic and anaerobic organisms

    o Escherichia coli

    o Klebsiella pneumoniae

    o bacteroides

    • gram positive

    o anaerobic and microaeorphilic streptococci

    o enterococci





    Clinical presentation

    The typical presentation is one of right upper quadrant pain, fever and jaundice. Anorexia, malaise and weight loss are also frequently seen. Depending on the immune status of the patient, and the organism involved, presentation may be dramatic or insidious.



    Radiographic features

    As a general rule, bacterial and fungal abscesses are often multiple, whereas amoebic abscesses are more frequently single. Amoebic abscesses are more common in a sub-diaphragmatic location and are more likely to spread through the diaphragm and into the chest.



    Plain film

    A plain abdominal radiograph is poor for evaluating liver abscesses. Indirect signs visible include:

    • gas within the abscess or biliary tree (pneumobilia) or beneath the diaphragm

    • right sided pleural effusion

    • calcification (hydatid cyst)



    Ultrasound



    Liver abscesses are typically poorly demarcated with a variable appearance, ranging from predominantly hypoechoic (still with some internal echoes however) to hyperechoic. Gas bubbles may also be seen 7. Doppler will demonstrate absence of central perfusion.

    In patients with monomicrobial K pneumoniae abscesses, the lesion may appear solid and mimic a hepatic tumour 6.



    CT



    As with other modalities, appearance of liver abscesses on CT is variable. In general they appear as peripherally enhancing, centrally low density lesions 8. Occasionally they appear solid, or contain gas. Segmental perfusion abnormalities, with early enhancement may be seen 8.



    MRI



    Signal characteristics include

    • T1

    o usually hypointense centrally

    o heterogeneous

    o may be slightly hyperintense in fugal abscess

    o enhancement of the capsule, although this may be absent in immunocompromised patients 5

    o multiple septations may be present

    • T2 - tends to have hyperintense signal

    • DWI - tends to to have high signal within the abscess cavity 9

    • ADC - tends to have low signal within the abscess cavity 9



    Treatment and prognosis



    Medical antimicrobial therapy is required in all cases, and sometimes suffices if abscesses are small.

    Radiology has a major role to play in the percutaneous drainage of hepatic abscesses, which can be performed either under ultrasound or CT guidance.

    Surgery is limited to those patients where percutaneous drainage is impossible or has proven ineffective. Additionally, the source of the abscess may require surgical treatment at which time the abscess may also be drained.

    Prognosis is highly variable, depending of not only the organism involved and size of the abscess, but also the co-morbidities present. Figures range from 9-80% 3





    source:

    http://radiopaedia.org/articles/hepatic-abscess-1

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