Editing Liver abscess


Three types of abscess, differentiated by causative organism:

* Pyogenic
* Amoebic
* Fungal

== '''Pyogenic abscesses''' ==

* '''Risk factors'''
** Diabetes
** Underlying hepatobiliary disease (cirrhosis)
** CKD
** History of malignancy
** Liver transplant
*** Specifically risks are:
**** Hepatic infarction from vascular thrombosis or anastomotic stenosis
**** Ischaemic cholangiopathy
**** Biliary anastomotic stricture
*** Treatment is similar to non-transplant setting
* '''Aetiology'''
** Cryptogenic process (43%)
*** ?undiagnosed abdominal disease, resolved infectious process, host factors making infection more likely
*** ERCP is only indicated in patients with some sort of finding suggesting a malignancy
*** Need a thorough workup for cause
** Biliary ductal system (ascending cholangitis) - 38% - mostly underlying malignancy, in non-transplant setting
*** Risks - biliary-enteric anastomosis, Caroli disease, biliary ascariasis, any biliary tract surgery
** Seeded through portal blood flow (5%) 
*** Diverticulitis, appendicitis, pancreatitis, IBD, PID, perforated viscus, omphalitis, CRC
** Haematogenous spread - hepatic artery (3%)
*** Endocarditis, pneumonia, osteomyelitis
*** More common in immunosuppressed patients
** Injury from trauma or liver-directed therapy (2%)
** Direct extension from adjacent disease (1%) 
*** Cholecystitis, subphrenic abscess, perinephric abscess, perforation of bowel directly into liver

* '''Pathophysiology'''
** Abscess occurs when an inoculum of bacteria exceeds the liver's ability to clear it, resulting in tissue invasion, neutrophil infiltration, and formation of an organised abscess
** Sources described above
*** Biliary - usually occurs as biliary obstruction causing stasis, colonisation, infection, and ascension (ascending suppurative cholangitis). Mostly intra-hepatic stones in Asia and malignancy in Western countries.
*** Ascending PV infection - has become much less frequent after antibiotics
*** Systemic - micro-abscess formation is quite common at autopsy in patients dying of sepsis
*** Trauma - intra-hepatic haematoma or necrosis can become an abscess, can present several weeks post-injury
** 75% of cases involve the right hemi-liver (unknown reason), caudate 5%, left hemi-liver 20%. Bilobar involvement is uncommon.
** Typically 1mm-4cm
** Most commonly gram-negative aerobes, and anaerobes
*** Abscesses from pyelophlebitis or cholangitis are usually poly-microbial, while systemic infections are usually mono-microbial
*** Sterile in 10-20%
**

* '''Presentation'''
** Classic presentation is fever, jaundice and RUQ pain (seen in only 10%)
** Malaise, anorexia, nausea
** Jaundice is often due to underlying biliary disease
** Diaphragmatic symptoms - cough, dyspnoea
** ALP mildly elevated in 80%, bilirubin elevated in 20-50%, transaminases mildly elevated in 60%
** Endogenous endophthalmitis - specific to Klebsiella, most common in diabetics

* '''Complications'''
** Rupture - peritonitis
* '''Imaging'''
** CXR
*** Elevated right hemidiaphragm
*** Right pleural effusion
*** RLL atelectasis
*** Abnormal extraluminal gas in RUQ
*** PV gas if pylephlebitis is source (GIT -> PV)
** USS
*** Sensitivity 80-95%
*** Not as good for lesions high up in the dome of the liver
** CT
*** Sensitivity 95-100%
*** Gas, rim enhancement
**
** MRI/MRCP
*** Equally sensitive to CT
* '''Differential diagnosis'''
** Sub-phrenic or other intra-peritoneal abscess
** Amoebic abscess
*** Sometimes not possible to differentiate - need to aspirate or trial anti-amoebic antibiotics
** Echinococcal cyst/hydatid disease (differentiate on imaging)
**
* '''Management'''
** Principles
*** Treat abscess and its primary source
*** Test for amoebic serology if indicated
*** Abx and drainage
** Medical
*** BCs then Abx
*** Base Abx on presumed source
**** Colonic - cef/met
**** Biliary - taz
**** Consider meropenem if recurrent cholangitis
**** Liver transplant - cover fungi
**** Skin or endocarditis - vanc for MRSA
*** Extended duration Abx - up to 6/52, but duration is not well-defined
** Drainage (almost always required)
*** Percutaneous (successful in 66-90% of cases)
**** Send pus for culture, including mycobacterium and fungi if immunosuppressed
**** Success rate seems to be higher with drainage catheter rather than one-off aspiration (100% vs 60%)
**** Contraindications: multiple large abscesses >5cm (however generally still worth trying), intra-abdominal source requiring surgery, ascites, requirement for transpleural drainage, coagulopathy, proximity to vital structures.
*** Surgical
**** Indications: percutaneous contra-indicated, failed non-op therapy, surgery required for something else, abscesses >5cm
**** Remember to send histo looking for entamoeba and cancer
**** Very rarely, partial hepatectomy is required
***** Infected hepatic malignant neoplasm
***** Hepatolithiasis
***** Intra-hepatic biliary stricture
***** Severe destruction from infection
* '''Prognosis'''
** Mortality now <10%



== '''Amoebic liver abscess (extraintestinal manifestation of Entamoeba histolytica infection)''' ==
'''Epidemiology'''

* 55% of those in endemic areas are infected, but <50% of those are symptomatic
* Mexico, India, Africa, parts of central and south America

'''Risk factors'''

* Most common in adult men (20-40), despite more even gender balance for colonic amoebic disease
* Migrants from India, Africa, Mexico, Central/South America
** Generally uncommon in short-term travellers
* HIV or other immunosuppression

'''Pathophysiology'''

* Entamoeba histolytica infection - protozoan, existing as a trophozoite or cyst
* All other species in the genus Entamoeba are non-pathogenic, and not all strains of histolytica are virulent
* Faecal-oral transmission - ingestion of mature cyst, excystation occurs in small bowel which releases trophozoites which migrate to large bowel. These produce cysts, which are passed in faeces.
* Asymptomatic carriers - cysts confined to intestinal lumen
* Symptomatic - cysts invade through intestinal mucosa
* Liver is most common extraintestinal manifestation
** Also brain and lungs
* Liver abscesses occur in 1% of patients with amoebiasis (ascends via portal system)
* Mostly causes a single focus in right lobe
** Liquefactive necrosis
** Fluid described as 'anchovy sauce' and is odourless unless secondary bacterial infection has occurred
** Progressive hepatic necrosis continues until the Glisson capsule is reached, which is resistant to hydrolysis by the amoebae; therefore the cavity tends to abut the liver capsule when found
** Chronic abscesses can develop a fibrous capsule and even calcify
* Patients rapidly develop anti-amoebic antibodies, but this does not appear to halt progression of disease

'''Presentation'''

* Between months to several years after return from endemic area
* Usually 1-2 weeks RUQ pain, high fever.
** Cough, sweating, malaise, weight loss, anorexia, hiccough
* Hepatomegaly, point tenderness over liver
* Be aware of rupture risk - peritonitis, but can also extend into chest
* Can also cause hepatic vein/IVC thrombosis
* Leukocytosis without eosinophilia
* Elevated ALP +/- other LFTs, hyperbilirubinaemia is unusual
* 10-20% have diarrhoea
*

'''Diagnosis'''

* Definitive diagnosis is with identification of E. histolytica trophozoites in pus or serum antibodies
* Aspiration is diagnostic only 10-20% of the time
* Abnormalities will be seen on USS or CT or MRI
** CXR - abnormal in 50% - elevated hemidiaphragm, atelectasis, pleural effusion
** USS - round, well-defined hypoechoic mass
** CT - low-density mass with peripheral enhancing rim
** MRI - low T1, high T2
** Will be seen as 'cold' on a liver radionucleotide scan as opposed to a 'hot' pyogenic abscess
** Can take up to 2 years for complete radiologic resolution
** Most commonly posterior right lobe, mostly solitary subcapsular lesions
** If in left lobe, concern for pericardial extension
* Commonly also see raised right hemidiaphragm on CXR
* Confirm with serological or antigenic testing - can take 7 days to become positive but 99% sensitivity after that
** Currently difficult to differentiate between active acute infection and past infection
* Maybe stool microscopy 
*

'''Differential diagnosis'''

* See pyogenic abscess section for differentiating features
* Echinococcal disease - differentiate based on imaging/serology
* Malignancy - usually no symptoms from mass

'''Management'''

* Principles
** Drainage is only necessary if:
*** No clinical response after 5-7 days of Abx
*** Abscess at high risk for rupture (5cm in diameter, or in the left liver)
*** Deterioration - diagnosis confirmation needed
** Drainage is actually rarely required
** If no response to medication, could have bacterial coinfection - usually responds in 3 days
* Don't commonly see trophozoites in aspirate but you can do other antigen/PCR testing
* Treat with tissue agent (to eliminate liver organisms) + luminal agent (to eliminate intraluminal cysts, even if not seen in the stool)
** Tissue agent - metronidazole 400mg PO TDS  7-10 days
*** Tinidazole also an option
** Luminal - eg paramomycin 25-30 mg/kg per day, in 3 divided doses, for 7 days
** If no improvement, consider aspiration/drainage or extended course
* Peritoneal rupture (size of abscess is most important risk factor)
** Percutaneous drainage of collections
** Laparotomy if doubtful diagnosis, hollow viscus perforation, fistulisation resulting in haemorrhage or sepsis, failure of conservative therapy
* Pleural rupture
** Thoracentesis
* Look for other extraintestinal manifestations
** Pleuropulmonary infection
** Cardiac infection
** Brain abscess
** Cutaneous infection

'''Follow-up'''

* Should do follow-up imaging to ensure resolution
* May take up to 9 months to resolve



== '''Fungal abscesses''' ==

* Risk factors
** Almost always immunosuppressed patients, typically from chemotherapy
** Solid organ or bone marrow transplant
** Indwelling stents/drains
* Causative agents
** Typically Candida (80%)
** Aspergillus
** Cryptococcus
* Treatment
** Antimicrobials
*** Step down to oral fluconazole
*** Beware of combined fungal/bacterial abscesses
** Drainage
*** Aspiration
*** Drainage
*** Surgical drainage

[[Category:Liver]]