Liver Abscesses and Cysts

Epidemiology

Hepatic cysts are usually asymptomatic and are often found incidentally. Therefore, it is difficult to predict the exact prevalence. It is estimated that about 5% of the population have hepatic cysts.¹

Cystic lesions of the liver include:

• Simple cysts
• Multiple cysts due to polycystic liver disease
• Neoplastic cysts
• Hydatid (echinococcal) cysts
• Abscesses

Other cysts can occur in the liver region but these are separated from hepatic cysts because they involve the bile ducts. They include:

• Ductal cysts
• Choledochal cysts: a congenital dilatation of part or whole of the common bile duct. There is a separate article entitled Choledochal Cysts.
• Cysts related to Caroli's disease: Caroli's disease is the combination of cystic dilatation of the intrahepatic bile ducts and infantile polycystic kidney disease. It has autosomal recessive inheritance.² It can present with fever, abdominal pain and recurrent attacks of cholangitis.

Simple cysts

• Pathophysiology: thought to be congenital. Lined with biliary-type epithelium but cyst fluid doesn't contain bile. Because the fluid is continuously secreted, aspiration does not allow cure.¹
• Presentation: usually asymptomatic; can cause right upper quadrant pain and bloating symptoms if large. If very large may be palpable abdominally. Rupture, torsion and jaundice caused by bile duct obstruction are rare.¹
• Investigations: ultrasound and CT scanning can show cyst anatomy. Liver function tests may be mildly abnormal.
• Treatment: is only needed if symptoms occur. 'Deroofing' of the cyst can be performed laparoscopically, excising the portion of the wall that extends to the surface of the liver so that cystic fluid can drain into the peritoneal cavity.³

Polycystic liver disease

• Pathophysiology: adult polycystic liver disease is congenital and is usually associated with autosomal dominant polycystic kidney disease with mutations in PKD1 and PKD2 genes.¹ Rarely, cases can occur in isolation and are associated with mutations in a third gene, polycystic liver disease gene.⁴
• Presentation: kidney cysts usually occur before liver cysts and renal failure is common. However, polycystic liver disease rarely leads to hepatic fibrosis and liver failure. Hepatomegaly and abdominal pain may be present. Cysts are usually first noticed during puberty. Rupture, haemorrhage and infection are rare.
• Investigations: examination of the kidneys and renal function needs to be carried out. Liver function tests may be abnormal but liver failure is rare. Ultrasound and CT scanning will show multiple liver cysts.
• Treatment: is only needed if symptoms occur. Similar 'deroofing' procedures can be carried out as well as liver resection. However, symptom recurrence is high as new cysts form. Liver transplantation is rarely used.¹

Neoplastic cysts

• Cystadenomas and cystadenocarcinomas are rare. Cystadenoma is the premalignant lesion.
• Presentation: usually asymptomatic or vague symptoms including bloating, nausea and fullness can occur. Abdominal pain and biliary obstruction can result as they enlarge.
• Investigations: liver function tests may be normal. Carbohydrate antigen (CA) 19-9 levels may be raised. This can also be measured in cyst fluid.¹ Typical patterns may be seen on CT scanning/other imaging.
• Treatment: is by resection. Despite complete resection, cystadenocarcinomas can recur.⁵

Hydatid (echinococcal) cysts

• Pathophysiology: these are caused by infestation with the parasite Echinococcus granulosus, a tapeworm. Carnivores such as dogs and wolves act as definitive hosts. They pass out eggs with their stool which can then be ingested by sheep, cattle and humans. The egg larvae then invade the gastrointestinal tract and mesenteric vessels of these intermediate hosts and can pass to the liver. In the liver, the larvae grow and the hydatid cyst develops, producing daughter cysts. Other carnivores who eat the liver of the intermediate hosts can then become infected and adult worms can develop in their gastrointestinal tract. The parasite is found worldwide. Human infection most often occurs in those who raise sheep or cattle or who have contact with dogs.⁶
• Presentation: can be asymptomatic (for up to 10-20 years⁶) or can present with pain and large right upper quadrant mass. Large cysts can rupture into the biliary tree (causing jaundice or cholangitis), through the diaphragm into the chest, or into the peritoneal cavity (causing anaphylactic shock). Secondary infection and hepatic abscesses can result from hydatid cyst rupture. Hydatid cysts may also form in the lungs and other organs.⁶
• Investigations: eosinophilia may be present. Echinococcal antibody titres are positive in about 80% of patients.¹ A classic appearance may be seen on CT or MRI scanning (daughter cysts within a thick-walled main cavity¹).
• Treatment: is needed to prevent complications due to cyst growth and rupture. It uses chemotherapy with albendazole or mebendazole, percutaneous procedures and conventional surgery. Please refer to the separate articles entitled Hydatid Disease and Management of Hydatid Disease for treatment details.

Liver abscesses are caused by bacterial, parasitic, or fungal organisms. In developed countries, pyogenic abscesses are the most common but worldwide, amoebae are the commonest cause.⁷

Epidemiology

A retrospective study over a 10 year period of patients >16 years old admitted to the Royal Hallamshire Hospital in Sheffield with a diagnosis of liver abscess found 4 patients with amoebic liver abscesses and 65 with pyogenic liver abscesses. They estimated an annual incidence for liver abscesses of 2.3 per 100,000 people per year in the UK.⁸

Aetiology

• Pyogenic liver abscess:
  • Can be single or multiple. The right lobe is affected twice as often as the left, 5% have bilateral involvement.⁹
  • Most secondary to infection originating in abdomen (cholangitis secondary to stones or stricture or malignancy is commonest, diverticulitis, appendicitis, crohn's disease, perforated peptic ulcer).
  • May be iatrogenic secondary to liver biopsy or a blocked biliary stent.
  • Bacterial endocarditis and dental infection are other causes.
  • No cause found in 15%
  • More common if immunocompromised
  • 15% of adults with liver abscesses have diabetes.⁷
  • Liver cirrhosis is a strong risk factor.¹⁰
  • Liver abscess is a complication of umbilical vein catheterisation in infants. In children and adolescents there is usually immune compromise or trauma.
  • Tends to be polymicrobial. Organisms usually of bowel origin with E. coli and Klebsiella pneumoniae, Bacteroides spp., Enterococci and anaerobic Streptococci the most common. Staphylococci and haemolytic Streptococci more likely if secondary to endocarditis/dental infection. Fungal (Candida spp. most common) or opportunistic organisms more likely if patient immunocompromised.⁷
• Amoebic liver abscess:
  • 10% of the world's population is chronically infected with Entamoeba histolytica.⁷ Infection occurs most commonly in tropical and subtropical areas and is more likely if there is poor sanitation and overcrowding.
  • Transmission is via the faecal-oral route. Amoebae invade intestinal mucosa and can gain access to the portal venous system.
  • E. histolytica causes amoebic colitis and dysentery but liver abscess is the most common extra-intestinal manifestation of infection.¹¹
  • Liver abscess can present without a preceding history of colitis. It can also present months to years after travel to an endemic area.
  • Affects the right lobe in 80%.⁷

Presentation

• Multiple abscesses tend to present more acutely and single ones more indolently
• Right upper quadrant pain, tenderness, hepatomegaly, possible palpable mass
• Swinging fever
• Night sweats
• Nausea and vomiting
• Anorexia and weight loss
• Cough and dyspnoea due to diaphragmatic irritation
• Referred pain to the right shoulder
• Jaundice (in 25% of cases, commoner with disease of the biliary tree and multiple abscesses)⁹
• Pyogenic liver abscesses can present as pyrexia of unknown origin in some people who may not have right upper quadrant pain; pain is a prominent feature in amoebic liver abscess
• Check history for travel to an Entamoeba histolytica endemic area

Differential diagnosis

• Causes of pyrexia of unknown origin (PUO)
• Metastatic malignancy affecting the liver
• Hepatocellular carcinoma
• Biliary disease including cholecystitis
• Bacterial pneumonia
• Gastritis

Investigations

• Raised white cell count
• Raised ESR
• Mild normochromic normocytic anaemia
• Abnormal liver function tests (raised alkaline phosphatase, low albumin, raised serum transaminases, raised bilirubin)
• Blood culture is positive in 50%⁹
• Stools can contain entamoeba cysts or trophozoites
• Serology should be carried out if Entamoeba histolytica suspected
• Raised right hemidiaphragm on CXR. May be atelectasis or pleural effusion.
• Ultrasonography can show abscess and also allow guided percutaneous aspiration and drainage. Aspirated fluid should be sent for culture and sensitivity. It also allows biliary tree examination.
• CT scanning can show the abscess, allow guided aspiration and drainage and show other intra-abdominal abscesses or a possible cause such as diverticular disease, appendicitis etc. It is good for the detection of small abscesses.
• ERCP can show the site and cause of biliary obstruction and allow stenting and drainage.
• Investigation should always seek to determine the underlying cause.

Treatment

• Antibiotics:
  • Pyogenic liver abscess: broad spectrum antibiotics should be started before waiting for culture results. Use a penicillin, an aminoglycoside and metronidazole. A third generation cephalosporin can be considered in the elderly or if renal function is impaired.⁷ Antibiotic therapy can be modified once culture results are available. Treatment may be needed for up to 12 weeks and should be guided by the clinical picture and radiological monitoring.
  • Amoebic liver abscess: metronidazole is the treatment of choice. 95% of patients with amoebic liver abscess recover with this alone. Most patients show a response to treatment within 72-96 hours.¹² Diloxanide furoate should be prescribed for 10 days to eliminate intestinal amoebae after the abscess has been successfully treated.
  • Antifungal agents such as amphotericin B are used if fungal abscess is suspected.
• Drainage:
  • Most patients with pyogenic liver abscess, and those will very large amoebic abscesses, may not recover with antibiotics alone and need drainage guided by ultrasonography or CT.
  • Percutaneous aspiration can be carried out for small abscesses; larger abscesses may need catheter drainage which is also CT or ultrasound guided. Drainage should also be carried out if there is impending rupture.
  • Open surgery may be necessary if the abscess has ruptured and there are signs of peritonitis or if there is a known abdominal pathology such as appendicitis.
• Supportive measures:
  • Fluids
  • Nutrition
  • Pain relief

Complications

• Overwhelming sepsis
• Rupture of the abscess into adjacent structures (pleural, peritoneal and pericardial spaces)
• Secondary infection of amoebic liver abscesses

Prognosis

• Pyogenic liver abscess: early diagnosis and treatment with antibiotics improves outcome but mortality rates are still 5-30%.⁹ Factors that affect prognosis include presence of shock or disseminated intravascular coagulation (DIC), immunodeficiency, diabetes, associated malignancy, ineffective surgical drainage.⁷
• Amoebic liver abscess: since the introduction of rapid diagnosis and effective medical treatment, mortality rates have fallen to 1-3%.^{12,13,14,15,16,17,18}

In the Hallamshire series described above, mortality rate was 12.3%.⁸