What is liver abscess?
The liver acts as the first filtering site of absorbed luminal contents and is particularly susceptible to contact with microbial antigens of all types.
In addition to hepatotropic viruses, the liver may be affected by:
- spread of bacterial or parasitic infections from sites external to the liver;
- primary infections from spirochetes, protozoa, helminths or mycetes;
- systemic consequences of bacterial or granulomatous diseases.
Until recently most of the hepatic abscesses were a consequence of appendicitis complicated by piles in young patients. This presentation is less common today because of the earlier diagnosis and the effectiveness of antibiotic therapy. Most cases are currently cryptogenic or occur in elderly men with underlying biliary tract diseases.
Hepatic abscesses can be distinguished in bacterial, amoebic, fungal depending on whether they are due to bacteria, protozoa (amoeba) or mycetes (fungi). Bacterial abscesses are the most common and in most cases result from biliary tract infections or from an adjacent infection site.
Hepatic abscess can be defined as a pyogenic when it is caused by bacteria capable of causing purulent infections in the organism, ie with the formation of pus. Most liver abscesses of this type are polymicrobial and Escherichia coli, Klebsiella, Proteus, Pseudomonas and Streptococcus species, in particular Streptococcus milleri, are among the microorganisms responsible.
Unfortunately, however, in about 40% of the cases of pyogenic liver abscess a clear source of infection cannot be identified, therefore for these pathologies it is hypothesized that the cause may be found in the oral bacterial flora, especially in patients with severe periodontal disease.
Liver abscess symptoms
In the past, direct invasion often associated with complications of appendicitis and other intra-abdominal infections were the main causes of liver abscesses. However, better treatment and management these days have reduced the incidence and subsequently cholangitis-associated infections (bile duct infection) has become the most common cause especially in the elderly. The signs and symptoms of these conditions may appear early and therefore should be considered in the early clinical presentation of a liver abscess.
Signs and symptoms of a liver abscess include:
- Abdominal pain in the upper right quadrant, but can extend to the left side as well or present with pain referred to the right shoulder.
- Fever and chills.
- Tenderness in the liver area with a palpable enlargement of the liver (hepatomegaly).
- Anorexia – loss of appetite.
- Cough and / or hiccup due to diaphragm irritation
- Jaundice at times
- Some patients may present without abdominal pain.
Although rare, a subdiaphragmatic liver abscess may spread into the chest cavity to cause empyema (pus around the lungs) or lung abscess. The clinical features of these conditions may therefore also be present and must be investigated. Sepsis or peritonitis are other serious complications that must be considered.
Amoebic liver abscess
Amoebic abscesses or hepatic amebiasis are the predominant abscesses in developing countries and are caused by the Entamoeba histolytica protozoan. Mycotic abscesses are found mainly in the West due to the increase of immunosuppressed subjects due to HIV infection, immunosuppressive therapies, transplants.
Amoebic liver abscess, unlike its bacterial counterpart, is caused by amoebiasis. The term amoebiasis identifies a generic presence of the Entamoeba histolytica parasite within the organism; this presence can be substantially asymptomatic and harmless, and in this case we speak of commensal amoebic infection, or produce lesions of the tissues accompanied by severe symptoms, first of all dysentery. In the latter case we speak of amoebic disease.
Entamoeba histolytica is a protozoan infectious agent capable – unlike the other species of the genus Entamoeba – of penetrating the colon wall and generating both local and extraintestinal pathologies (eg necrotic liver abscesses).
After an incubation period, ranging from a few days to a few months or years (usually 2-4 weeks), amoebiasis can present with clinical pictures of variable severity from chronic moderate diarrhea, alternating with periods of constipation, to severe dysentery acute fulminant. This symptom is due to the direct attack of the amoebic trophozoites on the colon cells, which – when important – can cause blood diarrhea and the presence of mucus in the stool.
Added to this is a set of secondary symptoms of varying intensity depending on the severity of the infection:
- more or less high fever,
- weight loss,
- rectal tenesmus,
- nausea and cramped abdominal pain.
Due to the alternation of periods of constipation with others of constipation, non dissenteric amoebiasis can be confused with irritable bowel syndrome or diverticulitis. Amoebic dysentery can instead be confused with shigellosis, salmonellosis, schistosomiasis or ulcerative colitis
Thanks to the synthesis of specific proteases, the amoebae have the potential to attack the extracellular matrix and open a gap in the intestinal wall, entering the portal circle through which they reach the liver, where they can cause necrotic liver abscesses. The patient suffering from amoebiasis can therefore complain of pain on the liver (with hepatomegaly) and ascending colon.
What causes liver abscess?
Biliary tract infections (eg cholangitis, cholecystitis) represent the most common identifiable cause of liver abscess. Liver infection can occur via the bile duct, along a penetrating vessel or from an adjacent septic focus. The pyogenic hepatic abscess can be a late complication of endoscopic sphincterotomy for bile duct stones or appear after 3-6 weeks after a biliodigestive anastomosis operation.
Pyogenic liver abscesses can complicate recurrent pyogenic cholangitis, which are more frequent in East and South-East Asia and are characterized by recurrent episodes of cholangitis, intrahepatic calculus formation and, in many cases, by parasitic biliary infections.
Less commonly the hepatic abscess represents a complication of bacteremia originating from underlying abdominal pathologies, such as diverticulitis, perforated or penetrating peptic ulcer, gastrointestinal tumors, chronic intestinal inflammatory diseases or peritonitis, or more rarely by bacterial endocarditis.
Occasionally, a pyogenic liver abscess may be the form of presentation of a hepatocellular carcinoma or gallbladder or the complication of chemoembolization of a hepatic neoplasm. In about 40% of cases of pyogenic liver abscess an obvious source of infection cannot be identified.
Oral bacterial flora has been proposed as a potential cause in these cases, especially in patients with severe periodontal disease.
Most pyogenic abscesses are polymicrobial. The most frequently isolated microorganisms are Escherichia coli, Klebsiella, Proteus, Pseudomonas and Streptococcus species, in particular Streptococcus milleri. With the improvement of culture methods and earlier diagnosis the number of identified cases caused by anaerobic microorganisms has increased.
The most commonly identified anaerobic species are Bacteroides fragilis, Fusobacterium necrophorum and anaerobic streptococci. The pyogenic abscesses associated with recurrent pyogenic cholangitis may be caused by Salmonella typhi; Clostridium and Actinomyces species are uncommon causes of liver abscess and rare cases are caused by Yersinia enterocolitica, septic melioidosis, Pasteurella multocida, Haemophilus parainfluenzae and Listeria species.
Liver abscesses caused by Staphylococcus aureus infection are more common in children and in patients with septicemia or decreased resistance to infections. Fungal abscesses may occur in immune-compromised patients, particularly those with hematological malignancies.
Entamoeba histolytica liver abscess
Every year, around 65,000 deaths are directly attributable to ancylostomatidae infections, another 60,000 to Ascaris infections, while Entamoeba histolytica causes about 70,000 deaths a year.
Intestinal parasites are among the major causes of morbidity in children between 5 and 14 years, being able to induce malabsorption of nutrients and chronic blood loss, with long-term effects on body-weight growth and cognitive development, and sometimes giving rise to surgical complications (intestinal obstruction, rectal prolapse, abscesses).
Most parasites are ubiquitous, although the greatest spread is in tropical and subtropical countries for the reasons mentioned above. Until a few decades ago, Mediterranean countries were an endemic area for several parasites: among others, Entamoeba histolytica / dispar.
Ultrasound diagnostics, scintigraphy and computerized axial tomography support the detection of the presence and localization of the hepatic amebic abscess and can be considered diagnostic when associated with a specific antibody response to E. histolytica.
The diagnosis of amoebic liver abscess it can also be based on the exploratory puncture and macroscopic evaluation of the pseudo-purulent material (color “paste of anchovy”), the negativity of the cultures for bacteria, and the search for amoebic trophozoites, which is inconstant.
It is an infection caused by a protozoan, Entamoeba histolytica that exists in two forms: the cystic form, of resistance and infecting, and the trophozoites responsible for the pathogenic effects. The parasite can act as a commensal or invade the tissues, causing an intestinal or extraintestinal disease.
Since the mid-1990s it is evident that two distinct species, E. histolytica and E. dispar exist in nature and are morphologically indistinguishable from one another. Differentiation is possible based on gene analysis or isoenzymes patterns. E. histolytica currently remains the only pathogenic species, while E. dispar behaves as an exclusively commensal parasite.
Abscess treatment antibiotics
In the presence of a pyogenic abscess, early diagnosis and treatment with antibiotics improves the result, even if the mortality rate is very high and is between 5 and 30%. It is therefore necessary to proceed immediately with the administration of broad-spectrum antibiotics such as penicillin, aminoglycoside and metronidazole before having the results of the culture while a third-generation cephalosporin can be administered to elderly patients or in cases where renal function is compromised.
In the presence of an amoebic abscess the most indicated treatment is Metronidazole which is effective in 95% of treated cases, in this case the mortality rate does not exceed 3%.
However, antibiotic treatment may not be sufficient for total healing, in this case it is therefore necessary to proceed with a drainage guided by an ultrasound scan or a CT scan.
Antibiotic treatment of biliary and abdominal infections can be broad spectrum, for example associating ampicillin with an amino glycoside if the biliary origin is suspected. However, it is always advisable to carry out a crop analysis in order to pinpoint the most suitable antibiotic for treating the infection.
In patients with abscess who continue to be febrile 72 hours after starting metronidazole therapy, consideration should be given to the need for non-surgical aspiration. Amoebic abscesses can sometimes require surgical drainage if there is a risk of rupture or if the abscess continues to enlarge despite the therapy.
Flagyl (Metronidazole) antibiotic for abscess
Flagyl (Metronidazole) is an antibiotic that is effective against bacteria that do not tolerate the oxygen of the air (anaerobic bacteria). Flagyl is also active against some other microorganisms. Flagyl affects the cells of the microorganisms so that they die. Flagyl must be dosed 2 or 3 times a day – depending on the type of infection – to maintain an even concentration in the body.
Flagyl tablets are used in a variety of infectious diseases including infections of the vagina and gum infections, as well as in certain gastrointestinal infections and in Mb Crohn (a special inflammation of the colon and rectum). The tablets can also be given in conjunction with operations to avoid or treat infections.
Metronidazole contained in Flagyl may also be approved for the treatment of other conditions not mentioned in this product information. Ask your doctor, pharmacist or other healthcare professional if you have any further questions and always follow their instructions.
In the treatment of amebiasis in adults the recommended dose is 1500 mg of Metronidazole per day, divided into three daily administrations for a period that can vary from 5 to 10 days depending on the individual pharmacological response. In children, however, it is recommended to use 35 to 50 mg / kg / day, divided into three daily administrations for a period of 10 days.
During treatment with Flagyl it is recommended to avoid alcohol intake, because unpleasant consequences such as headache, nausea, vomiting, abdominal cramps and sweating may occur. To avoid these possible side effects it is advised not to take alcohol either during treatment, or in the three days following the end of treatment with Flagyl.
Flagyl also interacts with anticoagulants, such as Warfarin, altering its efficiency; therefore, it is advisable to monitor the plasma levels of the anticoagulant when it is administered simultaneously with Flagyl.
Liver abscess treatment duration
Antibiotics are usually sufficient for the treatment of multiple small abscesses. Surgical drainage may be required for larger abscesses, particularly the massive solitary abscess. Percutaneous drainage (through the skin) can sometimes be considered appropriate. Some antibiotics such as metronidazole can also be used for an amoebic abscess and antifungal drugs can be started after the drainage of a fungal abscess.
Without timely treatment, there is a risk that the spread of the infection and the rupture of an abscess has poor vision and is often fatal.
5-nitroimidazoles are used: a daily dose of 2 grams of Metronidazole (in children 15 mg / kg) for 3 days or Tinidazole 2 g in a single dose (in children 50-75 mg / kg).
Furazolidone is available in pediatric suspension for children and newborns (2 mg / kg three times a day for 7-10 days).
Paromomycin can be used during pregnancy, but in the case of mild illness, it is recommended to postpone treatment until after delivery. Relapses attributable to phenomena of drug resistance to each of the aforementioned products are described.
Author: Dr. Eddie Louie , Infectious Diseases & Immunology, Internal Medicine, Phone: (212) 682-9202