Liver Abscess: Complications and Treatment.

Abstract

Content available: Audio Recording Liver abscess is an inflammatory space-occupying lesion of the liver caused by infectious agents. Amoebic liver abscess (ALA) and pyogenic liver abscess (PLA) are its two predominant causes. Rarely, liver abscess can be caused by fungi, mycobacteria, and other atypical organisms. ALA is the predominant cause of liver abscess in India, seen in more than 60% of cases.1 It is caused by Entamoeba histolytica with feco-oral route, the predominant mode of transmission. In this review, we describe the overview of ALA and PLA, along with its complications and management. Amoebiasis is endemic in India and primarily affects the gastrointestinal tract. ALA is the most common extraintestinal involvement in amoebiasis, seen in 3% to 9% of cases.2 The disease usually occurs in male patients in the 20 to 45 years age group. Risk factors include chronic alcohol use, diabetes, cirrhosis, and retroviral disease. The clinical presenting features include fever, pain in the abdomen, and anorexia. Jaundice can be seen in about 15% of patients with ALA and is usually associated with a large and/or multiple abscesses and compression of biliary tree by an abscess near porta hepatis or caused by concomitant alcoholic hepatitis.1 Although classically described as a solitary abscess in the right lobe of the liver, 35% of patients may have a left lobe liver abscess with or without a right lobe abscess, and 15% of patients can have multiple liver abscesses.3 Recognizing the unusual variants of ALA is important because these are generally associated with complications (Table 1).2 The clinical course of ALA is usually benign in the absence of poor prognostic markers (Table 2).1, 4 Rupture** Risk factors for rupture include left lobe liver abscess and abscess with a thin rim (<10 mm) of hepatic parenchyma. - Pleural cavity: empyema - Peritoneal cavity: peritonitis/abdominal collection - Pericardial cavity: pyopericardium - Biliary tree: spontaneously or after catheter drainage Compression - Biliary tree: jaundice - Inferior vena cava: ascites, pedal edema Vascular thrombosis - Hepatic venous thrombosis - Portal venous thrombosis - Encephalopathy - Jaundice - Serum bilirubin > 3.5 mg/dL - Serum albumin < 2 g/dL - Large volume of abscess - Multiple abscess Clinically and radiologically, ALA may be difficult to distinguish from PLA. Classically, aspiration of ALA reveals anchovy sauce–like aspirate. Microbiologically, trophozoites are rarely demonstrated in aspirate. In addition, serology for E. histolytica may be relevant in travelers returning from high-endemic areas, being of limited value in residents of highly endemic areas. Molecular and antigen testing, if available, may be useful. Noninvasive testing, such as use of polymerase chain reaction, is increasingly being used for detection of E. histolytica DNA in other body fluids, such as blood, pus, saliva, and urine.5 Newer tests such as lateral flow assays using markers in serum can potentially be used for rapid noninvasive diagnosis of ALA if available on a widespread basis.6 Management of ALA comprises medical management, radiological drainage, and surgical management (Fig. 1). In the absence of formal guidelines on management, evidence for guiding treatment decisions, such as timing and indications of radiological intervention, is limited. Tissue amebicides such as nitroimidazoles form the mainstay of management of all patients with ALA (Table 3). Oral or intravenous (IV) administration (in patients unable to take orally [PO]) of metronidazole results in resolution of fever, toxemia, and pain in 80% of 90% of patients with uncomplicated ALA within 48 to 72 hours of treatment. Tinidazole is better tolerated and has the advantage of shorter duration of treatment. Other options include nitazoxanide, which has an advantage of being both tissue and luminal amebicide. The treatment with tissue amebicides should be followed with luminal amoebicidal agents to eradicate the luminal amebae and to prevent subsequent tissue invasion and spread of the infection through cyst.7 The indications for drainage of liver abscess together with medical management are: (1) left lobe liver abscess, (2) abscess with thin rim of hepatic parenchyma (<10 mm) around it, (3) multiple liver abscesses, (4) impending rupture recognized on imaging, and (5) nonresponse to medical therapy after 3 to 5 days. In the absence of these high-risk features, the evidence for upfront drainage is controversial. Faster resolution of clinical and biochemical features is seen in some but not in other randomized trials comparing the strategy of combination of drainage and medical management with that of medical management alone. A recent systematic review found a combination strategy to be effective in reducing the abdominal pain and local tenderness, but not in resolution of fever, healing of abscess, and length of hospital stay, with benefits limited to abscesses of more than 5 cm.8 Hence routine drainage of abscess is not recommended in patients with ALA but may be used in selected patients with size greater than 5 cm. Percutaneous catheter drainage (PCD) is preferred over percutaneous needle aspiration, particularly in larger abscess (>10 cm), subcapsular location, high risk for rupture, and if superinfected. Even for complications such as rupture into peritoneum, there is evidence that conservative management with PCD results in better outcomes than surgery.9 Catheter removal is usually recommended when the drainage output is less than 10 mL/day.10 Duration of catheter removal may vary; however, earlier removal is not associated with a higher healing rate.11 The higher mortality associated with surgery combined with the widespread availability of image-guided drainage has limited the role of surgery in the management of ALA. Surgery can be considered in those with no response to appropriate antibiotics and PCD drainage. Clinical and biochemical resolution occurs rapidly in patients with ALA with optimal management. Radiological resolution is often delayed and does not warrant additional therapy. Relapses are uncommon in ALA.12 PLA occurs in the setting of abdominal/biliary tree infections or in the presence of systemic bloodstream infections. Patients with PLA usually have more pronounced systemic features with multiple liver abscess on imaging compared with those with ALA. Unlike ALA, the principles of treatment of PLA involve drainage of abscess, use of appropriate antibiotics, and control of primary source of infection (Table 4).13 The differentiating features of ALA and PLA are summarized in Table 5. Causative organism - Klebsiella pneumoniae - Escherichia coli - Pseudomonas - Enterobacter - Proteus - Streptococcus** Causative agents in case of bloodstream infections. - Staphylococcus** Causative agents in case of bloodstream infections. Associated conditions - Biliary tract infection: cholangitis in biliary obstruction, acute cholecystitis - Abdominal infections: diverticulitis, appendicitis - Hematogenous spread: endocarditis, bloodstream infection, central venous catheter–associated infection - Trauma - Postoperative conditions Predisposing host factors - Diabetes - Immunosuppression - Malnutrition - Advanced age Diagnosis - Imaging - Microbiological Antibiotics (duration: 2-6 weeks)† † Usual duration of 2 weeks of IV antibiotics followed by oral antibiotics. - Third generation cephalosporins - Aminoglycosides - Piperacillin tazobactam - Carbapenems - Vancomycin (if suspecting gram positive) - Metronidazole (for anaerobic coverage) Drainage (imaging guided) - <3-cm abscess: antibiotics alone - 3- to 5-cm abscess: percutaneous aspiration - >5-cm abscess: PCD Poor prognostic factors - Advanced age - Immunosuppression - Comorbid medical conditions, such as cirrhosis, malignancy, etc. - Abscess associated with systemic complications, such as acute kidney injury, shock, etc. Surgery - Abscess not amenable to percutaneous drainage - Rupture abscess - No improvement with antibiotics and percutaneous drainage - Underlying surgical cause of liver abscess Source control - Biliary tract obstruction: drainage of biliary tract - Diverticulitis: drainage if associated with abscess - Hematogenous spread: appropriate antibiotics, drainage if associated with abscess, removal of catheter (in cases of catheter-associated sepsis) Recent advances in interventional radiology, intensive care, and use of effective antibiotic therapy have resulted in a decline in the mortality rates of liver abscess in India from 24% in earlier series to 1% to 3% in more recent studies.1 The course of ALA is usually benign in the absence of poor prognostic factors. Management involves medical management in all patients along with drainage of abscess in certain patients with high-risk features. Unlike ALA, patients with PLA require an upfront combination of drainage and appropriate antibiotics, along with appropriate treatment of primary infection.