Related narrative: Multiple Liver Abscesses
The etiology of liver abscess can be pyogenic, amebic or fungal. Other fluid containing liver lesions include echinococcal, benign and malignant cysts. Pyogenic abscess is most commonly biliary (stone disease, instrumentation) in origin (40-50%), followed by arterial (eg. dental cleaning bacteremia), portal (pylephlebitis, eg. perf. appendix, diverticulitis) and direct extension (eg. perf. ulcer) routes (~8% each). A small percent (~3%) arise from trauma, and the rest (~30%) are cryptogenic.
The incidence of pyogenic liver abscess is 15/100,000 admissions, the majority (>50%) are right-sided, solitary and polymicrobial. Patients commonly present with fever, chills, abdominal pain, elevated white blood cell count and weight loss. Over half present with jaundice and a third have hepatomegaly. Alkaline phosphatase, AST and ALT are commonly elevated. Immunocompromised patients (HIV, cancer, diabetes, liver transplant) are more susceptible to hepatic abscess following bacteremia. Interventions such as hepatic artery embolization and chemoembolization, cryotherapy, and radiofrequency ablation (RFA) increase the risk. Patients with biliary-enteric anastomoses are also at increased risk.
The gram-negative E. coli and klebsiella are common (>10%) and commonly associated with biliary etiology. Less common gram negatives include pseudomonas, proteus, enterobacter, citrobacter and serratia. Staph aureus is commonly associated with hematogenous seeding. Common gram positives include the microaerophilic strep milleri group, enterococcus, strep viridans. Staph aureus and beta hemolytic strep are less common. Staph is most commonly associated with hematogenous spread. Bacteroides is the most common anaerobe, while fusobacterium, anaerobic strep., clostridium spp. and lactobacilli are also seen and are commonly associated with colon disease.
Diagnosis is confirmed by CT scan which has a 95-100% sensitivity, and treatment consists of drainage, broad-spectrum antibiotic coverage (fluroquinolones, clindamycin, metronidazole, ampicillin, vancomycin in combination or single agent such as zosyn, imipenem or timentin) and treatment of the underlying pathology. Percutaneous drainage plus antibiotics is the treatment of choice if there is no intraabdominal pathology requiring surgical intervention. ERCP for decompression and stenting may be added if there is biliary etiology not requiring immediate surgery. Open surgical drainage may be required if the abscesses are inaccessible percutaneously, if attempts have failed or if antibiotics fail to resolve the process after percutaneous drainage. Depending on the location of the abscesses, an anterior subcostal, posterior 12th rib, or transthoracic (dome lesions) may be used for open drainage. Intraoperative ultrasound helps localize abscesses, especially those that are deep. Drainage includes aspiration for gram stain and culture, walling off the rest of the abdomen with lap pads, blunt finger dissection, biopsy of the wall for amebic trophozoites, microabscesses and malignancy and closed suction drains.
Amebic abscess due to entamoeba histolytica starts with ingestion of the cystic stage, digestion of the cyst wall by pancreatic enzymes, release of the trophozoites, multiplication in the GI tract, penetration of the mucosa, travel via veins and lymphatics to the liver. The organisms aggregate in the liver parenchyma where they cause thrombosis, necrosis and abscess formation. The liquid liver debris within the abscess result in the typical "anchovy paste" contents. The center of the abscess is sterile and the outer rim contains the invasive organisms. The disease is common in young men from endemic areas (Asia, Central America) and is associated with ethanol abuse and immunocompromise. The abscess may rupture into the abdomen, pericardium or pleura. Liver function tests may be normal, and white count elevated without eosinophilia. Indirect hemaglutination assay and immunoassay for antibodies help confirm the diagnosis. Treatment is presumptive (metronidazole, 750mg. PO TID X10d) and aspiration is done only if the diagnosis is uncertain, there is failure to respond within 3-5 days, if the abscess is > 5 cm or there is high risk of rupture. Open drainage is rarely required. The majority of patients defervesce within 72 hours, and 90% are cured within 10 days. Non-responders may be treated with chloroquinalone or emetine. A small percent (2-4%) will develop secondary bacterial infection. After primary treatment, a luminal-acting amebicide is given to eliminate asymptomatic colonization. CT resolution of the cavity may lag and follow-up CT is not necessary if the patient is asymptomatic.
Fungal abscess is commonly associated with immunocompromise, biliary malignancy, indwelling stents and frequent courses of antibiotics. Candida, aspergillus and cryptococcus are likely causes. Treatment is with systemic antifungal agents such as amphoteracin B, and treatment options include simple aspiration, percutaneous and open drainage. Mortality with antifungal treatment is 20% vs. 62% untreated, and outcome is directly related to treatment before fungemia ensues.
Hydatid (echinococcus) cysts are commonly seen in men in the 40s from endemic areas (middle east and South America), and the majority (75%) are right-sided and solitary. Primary hosts for echinococcus are dogs, sheep and elk/caribou, and humans are intermediate hosts. The ova pass from feces to humans where they invade the duodenal wall and pass via the portal vein to the liver. They may also invade lungs, bone and brain. The liver cyst consists of an active inner germinal layer with a gelatinous outer lamina. The liver forms a reactive fibrous pericyst, half of which are calcified. The germinal layer produces protoscolices (hydatid sand) which form daughter cysts. A third of hydatid cysts expand and may rupture into the biliary tree, into the peritoneal cavity or through the diaphragm. ELISA assay, complement fixation and indirect hemagglutination tests confirm the diagnosis. Eosinophilia is common.
Medical treatment of hepatic disease with benzimidazoles alone has less than a 30% success rate (higher for extrahepatic). Three months of medical treatment prior to surgical intervention is indicated to decrease complications from intraoperative exposure to cyst fluid. Scolicidal injection can be done with hypertonic saline, cetrimide or chlorhexidine unless there is a biliary connection. The area is walled-off with hypertonic saline-soaked gauze prior to aspirating and opening the cyst to prevent anaphylactic reaction to the cyst contents. After evacuation the cavity can be filled with omentum. Laparoscopic treatment may be successful with anterior cysts with a heavily calcified wall.
Benign hepatic cysts are commonly (60%) solitary, asymptomatic and do not undergo malignant transformation. Enlargement beyond 5 cm may cause compression symptoms. Percutaneous drainage of symptomatic cysts has a 100% recurrence rate and may result in secondary infection. Injection of sclerosing agents has a 20% recurrence rate. Liver cysts are the most common extrarenal manifestation of polycystic kidney disease. Laparoscopic unroofing and omental packing is effective treatment for accessible symptomatic cysts. Biopsy of the wall is done to rule out malignancy.
Neoplastic hepatic cysts arise from the bile duct mucosa, and malignant transformation of biliary cystadenoma. Females are more commonly affected, and age at diagnosis is usually over 40. Lesions may be solitary and occur throughout the liver parenchyma. Treatment may involve enucleation or resection (segmentectomy, lobectomy).
Traumatic cysts may contain blood or bile, be within the parenchyma or subcapsular. No treatment is indicated for asymptomatic patients. Aspiration or unroofing may be indicated for compressive symptoms. Bile leak into the cavity needs to be identified and controlled at the time of intervention.
Townsend: Sabiston Textbook of Surgery, 17th ed, 2004, Saunders, chapt 50
Pyogenic liver abscesses: mortality-related factors.
Percutaneous needle aspiration of multiple pyogenic abscesses of the liver: 13-year single-center experience.
Christy Quietmeyer, surgical chief resident