I. [Pathogenesis
Bacterial liver abscess is a purulent infection in the liver caused by septic bacteria, also known as septic liver abscess. The common pathogenic bacteria in adults are Escherichia coli, Aspergillus, Pseudomonas aeruginosa, Streptococcus, Staphylococcus and anaerobic bacteria. In children, Staphylococcus aureus and Streptococcus, and to a lesser extent, Friedländer pneumoniae.
Pathogenic bacteria into the liver, can be through the following routes.
1, the biliary system: the most important route of infection for our patients at present. In cases of acute purulent cholangitis complicated by choledocholithiasis, biliary ascariasis or schistosomiasis, the bacteria can travel up the bile duct and infect the liver to form liver abscesses.
2.Portal vein system: abdominal infection (such as gangrenous appendicitis, septic pelvic inflammatory disease, etc.), intestinal infection (such as ulcerative enteritis, bacillary dysentery, etc.), hemorrhoid infection, etc. can cause thrombophlebitis of the portal vein, and its septic emboli can enter the liver along the portal vein system and cause liver abscess. Due to the wide application of antibiotics, infections by this route have become rare.
3.Lymphatic system: If there are purulent lesions in the adjacent parts of the liver such as cholecystitis, subphrenic abscess and perforation of the stomach and duodenum, bacteria can invade the liver through the lymphatic system.
4.Blood infection: When septic infection in any part of the body, such as upper respiratory tract infection, acute osteomyelitis, subacute endocarditis, boils and carbuncles are complicated by bacteremia, the pathogenic bacteria can enter the liver from the hepatic artery.
5, direct invasion: When there is open injury to the liver, bacteria can be directly invaded through the wound. Sometimes after a closed injury to the liver forms a subperitoneal hematoma of the liver, the original bacteria in the liver can convert the hematoma into an abscess.
6.Other ways of unknown causes: many liver abscesses do not have obvious causes, such as occult liver abscess. There may be some kind of infectious foci in the body, and when the resistance of the organism is weakened, accidental bacteremia causes inflammation and abscess in the liver. It has been reported that 25% of occult liver abscesses are associated with diabetes mellitus. Sometimes the bacterial culture result of liver abscess is negative, which cannot be excluded due to inappropriate culture technique for anaerobic bacteria.
II. [Clinical manifestations
Bacterial liver abscesses mostly have no typical clinical manifestations, and the acute inflammatory period is often masked by the primary disease. The disease generally has an acute onset, and due to the rich blood flow in the liver, once the purulent infection occurs, a large amount of toxins enter the blood circulation and cause systemic septic toxic reaction. Clinically, it is often followed by some kind of pioneering disease (such as biliary ascariasis) followed by sudden chills, high fever and pain in the liver area. The main clinical manifestations are as follows.
1, chills and high fever: mostly the earliest symptoms, but also the most common symptoms. Patients at the beginning of the onset of the sudden chills, followed by high fever, fever is mostly flaccid, body temperature in 38 ~ 40 ℃, up to 41 ℃, chills and fever with a lot of sweating, pulse rate increases, several times a day, repeated episodes.
2. Pain in the liver area: inflammation causes enlargement of the liver, resulting in acute swelling of the liver peritoneum and persistent dull pain in the liver area; the time of appearance may occur before or after the appearance of other symptoms, or may occur simultaneously with other symptoms; severe pain often indicates a solitary abscess; abscesses are persistent dull pain in the early stage and often sharp sharp pain in the later stage, and those aggravated with breathing often indicate abscesses at the top of the liver diaphragm; sometimes pain may radiate to the right shoulder. Left liver abscess may also radiate to the left shoulder.
Weakness, poor appetite, nausea and vomiting: Gastrointestinal symptoms such as weakness, poor appetite, nausea and vomiting are more common due to the accompanying systemic toxic reaction and continuous consumption. A few patients showed more serious illnesses such as mental depression in a short period of time, and a few patients showed symptoms such as diarrhea, abdominal distension or more persistent erratic symptoms.
4.Signs: pressure pain in the liver area and hepatomegaly are most common; percussion pain in the right lower chest and liver area; sometimes reactive pleurisy or pleural effusion on the right side; if the abscess is located on the surface of the liver, the intercostal skin in its corresponding area is red, full, painful to palpation and sunken edema; if the abscess is located in the right lower part, it is common to have fullness in the right quarter rib area or right upper abdomen, and even a limited elevation is seen, and often an enlarged liver or fluctuating In late stage patients, ascites may appear, which may be due to portal vein circulation affected by portal phlebitis and compression of surrounding abscesses, as well as damage to hepatic function, long-term depletion resulting in malnutrition and low protein. Patients with secondary biliary obstruction are associated with jaundice. In other causes of purulent liver abscess, once jaundice appears, it indicates serious condition and poor prognosis. The above are typical manifestations of liver abscess, and it is worth pointing out that due to the current advancement of treatment technology and early application of antibiotics, the above typical manifestations are not common anymore, and abdominal pain, weakness and night sweats are often the main symptoms.
III. [Diagnosis
Diagnosis is generally not difficult, and bacterial liver abscess should be considered in any person with septic disease who suddenly develops obvious chills and high fever, pain in the liver area with percussion pain, hepatomegaly, and increased white blood cells suggesting bacterial infection. The following examinations can help the diagnosis of liver abscess.
1.X-ray examination: X-ray examination can reveal an increase in the shadow of the liver, and if the abscess is located in the right hepatic lobe, diaphragm elevation, restricted movement, blurred rib-diaphragm angle or a small amount of fluid in the chest cavity, right lower lung inflammation or pulmonary atelectasis can be observed. Sometimes gas-fluid planes may be present at the abscess site, mostly suggesting that the abscess is caused by gas-producing bacterial infection. Abscesses in the left lobe of the liver may present with compression of the gastric cardia and gastric lesser curvature. The presence of a subdiaphragmatic abscess is also taken into account when there is restricted diaphragmatic movement, loss of the angle of the rib diaphragm, and a small amount of fluid in the chest cavity.
2.Ultrasonic examination: the abscess site has a typical dark area of liquid echogenicity or a plane of fluid within the abscess. It is also important to understand the location, size and depth of the abscess cavity from the body surface in order to determine the best puncture point and the direction and depth of needle entry for the abscess, or to provide an access option for surgical drainage. However, multiple liver abscesses smaller than 1 cm are often difficult to detect by ultrasound and should be noted during clinical diagnosis. From an ultrasonographic point of view, it also needs to be differentiated from other cystic lesions. In general, liver cysts have neat and clear cystic walls and uniform intracapsular density. In contrast, the cavity wall of liver abscess is irregular, the boundary is not clear, and the cavity often contains multiple echogenic areas.
3.CT examination: CT examination can discover the size and shape of abscess, show the exact location of abscess in the liver, and provide clear and intuitive imaging data for clinicians to perform abscess puncture and surgical drainage. The main manifestation is the appearance of hypodense areas in the liver, with CT values slightly higher than those of liver cysts, and most of the boundaries are not very clear. After contrast injection, its peripheral enhancement is obvious and the boundary is more clearly defined. The typical performance of enhancement scan is the ring enhancement of abscess wall (target sign), and the appearance of “target” sign strongly indicates that abscess has been formed.
4.MRI examination: early stage of liver abscess has long T1 and T2 relaxation time characteristics in MRI examination due to the presence of edema. In the T1 weighted image, it appears as a low signal intensity area with unclear boundary, while in the T2 weighted image, the signal intensity increases. When an abscess is formed, the abscess is a low intensity signal area on T1 weighted images; the abscess wall is inflammatory granulation connective tissue, which also has a low signal intensity but is slightly higher than the abscess part; the inflammatory edematous liver tissue surrounding the abscess wall forms a slightly lower signal intensity foci than the abscess wall ring. On T2 weighted images, the signal intensity of the abscessed and edematous tissues increases significantly, and there is a slightly lower signal intensity annular abscess wall in between.
IV. [Common complications
Common complications are rupture of the abscess and penetration into the adjacent organs. It may penetrate into the thoracic cavity to produce abscess chest and pleural bronchial fistula, or penetrate into the abdominal cavity and pericardial cavity; sometimes it may also penetrate into the stomach, duodenum, colon, kidney and pancreas; in a few cases it may penetrate into the vena cava, hepatic vein, thoracic duct or abdominal wall, etc. Embolism, thrombosis and abscess formation in other parts may also occur. It is rare to cause rupture of intrahepatic vessels discharged from the bile duct, i.e. biliary bleeding.
V. [Treatment
1.Drug treatment:
(1) anti-infection in the treatment of the primary lesion at the same time, the use of high doses of effective antibiotics to control inflammation; currently advocate the planned combination of antibiotics, such as the first selection of drugs effective for aerobic and anaerobic bacteria, pending bacterial culture and drug sensitivity results and then select sensitive antibiotics.
(2) maintain water-electrolyte balance should be actively rehydrated to correct water and electrolyte disorders;
(3) Liver protection therapy;
(4) Improve the immunity of the body: give vitamins B, C and K. If necessary, repeatedly enter small doses of fresh blood and plasma several times to correct hypoproteinemia, improve liver function and infuse immunoglobulin.
(5) Chinese herbal medicine treatment: Generally, Chinese herbal medicine treatment is added to the above methods of treatment.
(2) B-ultrasound-guided percutaneous aspiration of pus or placement of drainage tube.
It is applicable to single large abscess, and the abscess cavity is punctured with a thick needle under the guidance of B ultrasound. After repeatedly flushing and aspirating the pus, a catheter can also be placed for regular flushing and drainage after surgery until the pus cavity is less than 1.5 cm and then removed. This method is simple, less invasive, and also has satisfactory efficacy, and is especially suitable for elderly and frail patients and critically ill patients. Puncture for pus aspiration or placement of a catheter for drainage is not a complete substitute for surgical drainage for the following reasons.
(1) If the pus in the abscess cavity is viscous, it will cause poor drainage.
(2) Thick drainage tubes may cause bleeding in the tissue or wall of the pus cavity.
(3) Incomplete drainage of multiple separated pus cavities.
(4) Primary lesions such as bile duct stones cannot be treated at the same time.
(5) The wall of abscess is not easily collapsed after pumping or drainage of thick-walled abscess.
3.Surgical treatment
The former is applicable when the abscess is large or the symptoms of systemic toxicity are still serious or complications appear after the above treatment, such as abscess penetrating into the chest cavity, penetrating into the abdominal cavity causing peritonitis or penetrating into the bile duct, etc.; the latter is applicable to chronic liver abscesses that are difficult to be treated by non-surgical therapy due to their thick walls and limited to one liver lobe.
(1) Abscess incision and drainage: the following procedures are commonly used.
The pus cavity was placed with double cannula negative pressure suction; the pus cavity and around the drainage tube were filled or covered with large omentum; the drainage tube was drained from the abdominal wall by another poke. The pus is sent for bacterial culture. It is the most commonly used method at present.
②Extraperitoneal abscess incision and drainage: liver abscesses located in the right anterior lobe of the liver and the left outer lobe of the liver, which have become closely adherent to the anterior peritoneum, can be drained by using an anterior extraperitoneal approach. It is no longer commonly used because it cannot show the peritoneal cavity.
(iii) Posterior lateral abscess incision and drainage: for abscesses on the top or posterior side of the diaphragm in the right lobe of the liver. After obtaining the pus, a long curved hemostatic forceps is inserted into the abscess cavity in the direction of the puncture and the pus is drained. Other procedures as above are no longer commonly used.
(2) Hepatic lobectomy: Applicable to.
(i) chronic thick-walled abscesses of long duration, where it is difficult to collapse the abscess cavity by incision and drainage of the abscess, and where the invalid cavity remains for a long time and the wound does not heal;
②After incision and drainage of liver abscess, sinus tracts remain for a long time, and pus flows continuously and cannot heal by itself;
③ Combined with a liver segment bile duct stones, the liver due to repeated infection, tissue destruction, atrophy, loss of normal physiological function;
(iv) Those with multiple abscesses in the left outer lobe of the liver resulting in serious destruction of liver tissue. The treatment of liver abscess by lobectomy should pay attention to not to spread the inflammatory infection to the operation field or abdominal cavity, especially the treatment of the liver section should be careful and proper, and the drainage of the operation field should be smooth, once the local infection will lead to complications such as biliary fistula and bleeding of the liver section. Emergency hepatic lobectomy for liver abscess has the risk of spreading inflammation, and surgical indications should be strictly controlled.
VI. [Prognosis
The prognosis of patients with bacterial liver abscess is closely related to their age, physical condition, primary disease, number of abscesses, early or late start of treatment, thoroughness of treatment and the presence of complications. The prognosis of young and elderly patients is worse than that of young adults, and the morbidity and mortality rate is higher. The morbidity and mortality rate of multiple liver abscesses is significantly higher than that of single liver abscesses. According to some statistics, there were 106 deaths (75.7%) among 140 cases of multiple liver abscesses, while there were only 28 deaths (23.9%) among 117 cases of solitary liver abscesses. The type of germs and virulence also have a close relationship with the prognosis of liver abscesses. Liver abscesses caused by bacteria such as Escherichia coli, Staphylococcus, Streptococcus, and Pseudomonas aeruginosa have a high mortality rate, and those infected with strains that are not sensitive to multiple drugs have a poor prognosis. The morbidity and mortality rate is higher in poor general condition and malnutrition and in those with significant hepatic impairment, such as hypoproteinemia and hyperbilirubinemia. The morbidity and mortality rate is higher in liver abscesses with complications, such as subdiaphragmatic abscesses, abscesses breaking into the abdominal cavity leading to diffuse peritonitis, biliary hemorrhage, or combined abscess thorax or lung abscess. On the contrary, those with solitary abscesses with mild symptoms and no complications have a good prognosis. Therefore, the requirements for the treatment of bacterial liver abscess are early diagnosis, early treatment, timely use of effective antibiotics, effective drainage of pus, thorough treatment of the primary lesion and strengthening of systemic supportive therapy, etc., which can greatly reduce the morbidity and mortality rate. In recent years, due to the rapid development of medical science and technology, the morbidity and mortality rate of bacterial liver abscess has been significantly reduced due to the continuous improvement of diagnosis and treatment level.