Liver abscess

Objectives: Aetiological diagnosis of amoebic and pyogenic liver abscess by microscopic examination and culture with identification and susceptibility test of the isolated organism.

The aspiration should not be done if the patient is uncooperative, has a bleeding disorder, an infection in overlying skin, pleura, lung or peritoneum, or a severe extrahepatic obstruction.

Test material: Creamy to yellowish-green pus or reddish-brown gelatinous material.

Equipment: Sterile gauze sponge, antiseptic solution, medicine cup, sterile towels, sterile gloves, syringe, needles, lidocaine 1%, scalpel with blade, wide-bore needle or Potain's aspirator, plaster.

Procedure: 1. The aspiration should be done in the operating theatre taking strict aseptic precautions, and only by a physician experienced in the procedure.

2. Place the patient in a left dorso-lateral position with the right arm abducted over the head.

3. If available, needle aspiration should be carried out using ultrasound guidance. If ultrasound examination is not available, the exploratory puncture should be carried out at the site of localized tenderness, pain, oedema, pneumonic crepitus, pleuritic or peritoneal friction. If no localizing sign is present, the needle should first be inserted in the anterior axillary line in the eight or ninth costal interspace, but not more than 8 cm deep, as the distance of the inferior vena cava from any part of the chest wall in adults is only 10 cm.

4. Abscess may be aspirated with a wide-bore needle fitted on to a 50 mL syringe, but it is much more comfortable for the patient to remove large abscesses with a Potain's aspirator.

5. The Potain's aspirator consists of a graduated glass bottle fitted with a rubber cork pierced by a T-shaped tube with two stopcocks (no. 1 and no. 2). Both stopcocks are connected via rubber tubing - no 1 is connected to a syringe pump and no. 2 to the aspirating needle. The air from the glass bottle is exhausted by the metal pump, while stopcock no. 1 is kept closed. After the needle has been introduced into the abscess cavity, the stopcocks no. 1 and no. 2 are opened and the necrotic material enters the exhaust bottle by suction.

6. Put on sterile gloves, drape with sterile towels, and disinfect the puncture site two times with skin antiseptic solution and let it dry in between.

7. Infiltrate with local anaesthetic from the skin through the intercostal muscles to the liver capsule, keeping the bevel of the needle at the upper edge of the rib. Do not advance the needle through the capsule into the liver.

8. Make a 4 mm skin incision with the scalpel blade.

9. Affix the needle on the syringe, or assemble the Potain's aspirator.

10. Introduce the aspirating needle through the skin incision and through intercostal muscles. The patient is asked to breathe superficially while the needle is advanced gently into the liver pointing against the abscess, or medially and cephalad if the abscess is not identified. The needle swings with the respiration when the the needle is inside the liver.

11. When it is felt that the needle is inside a space, the needle is inside the abscess cavity and the aspiration can begin. As much of the necrotic material as possible should be removed, but not more than 1000 mL in each trial.

12. 2-5 mL of the necrotic material should be collected in a sterile specimen tube and sent for culture and sensitivity test, and the last few mL of aspirated material should be collected separately and sent for examination for amoeba trophozoites.

13. When the aspiration is finished, the needle is removed and the puncture site is covered with a broad bandage.

14. If no material is found at the initial trial, one or two other directions may be tried, but it is unwise to persist with more trials. It is better to repeat the attempt one or two days later making use of ultrasound or scintigraphic examination to aid localization.

If more than 250 mL of material is withdrawn initially, or if swelling or local tenderness recurs, aspiration should be repeated at two- or three-day intervals.

15. If the material has a foul odor and is cream-, yellow- or green-stained, it indicates a pyogenic abscess or a secondary infected amoebic abscess. Bile-stained material indicates communication with the biliary system; the response in these patients is notoriously slow and large quantities of fluid are sometimes obtained even after repeated aspirations.

16. If no pus is found, a decision must be made to carry out open drainage or to continue conservative therapy.

Open drainage is indicated, if

1. pus is too thick or contains slough

2. pus is too much (500-1000 mL per day)

3. pus is infected

4. spontaneous rupture

17. If there is more than 200 mL of aspirate, further aspiration will be needed and this may be repeated daily.

Complications: 1. Haemorrhage into abscess cavity, haemobilia, bile peritonitis, hepato-portal AV fistula

Aetiology: Laceration of blood and bile vessels due to trauma, bleeding disorder, bile leak, respiratory motion.

Prevention: Check coagulation parameters, pass needle gently into the liver, have patient hold breath during aspiration.

2. Secondary bacterial infection

Aetiology: Introduction of organisms into cavity.

Prevention: Use meticulous aseptic technique.

3. Pneumothorax

Aetiology: Lung laceration due to respiratory motion.

Prevention: Have the patient hold breath during aspiration.

4. Haemothorax

Aetiology: Laceration of intercostal vessels or lung.

Prevention: Pass the needle through the intercostal space at the upper edge of the rib.

5. Injury to other viscera

Aetiology: Improper needle placement.

Prevention: Precise determination of liver and abscess before aspiration.

Storage: Specimens for bacteriological investigation may be stored in the refrigerator (2-8 °C). Specimens for parasitological investigation should be kept warm (32-35 °C).

Transportation: The specimen for parasitological investigation should immediately be brought to the laboratory, preferably in a thermos flask (3235° C).

Reporting: Positive findings of amoebae in the aspirate will be reported immediately. A negative culture report will be sent out two days after the specimen is received.

Comments: The indications for aspiration are:

1. a palpable mass or ultrasonic demonstrated mass;

2. persistent localized tenderness;

3. clinical and radiographic evidence of a markedly raised hemidiaphragm;

4. failure of signs and symptoms to remit with specific therapy.

    Aspiration of "pus" in which amoebae can be identified is diagnostic. Intestinal symptoms are often absent, and stools show amoebae in only 10 per cent of cases. Secondary infection may occur, especially after surgical intervention. Pyogenic liver abscess is usually secondary to bacteremia, septicemia or suppurative cholangitis, but there is a number of cases in which no cause is found. The main organisms isolated are Escherichia coli, anaerobic streptococci, Staphylococcus aureus, Streptococcus faecalis, and sometimes Salmonella typhi. In the Far East, suppurative cholangitis and liver abscess may be associated with liver flukes or immature lung flukes. Ascaris may invade the bile duct and cause cholangitis and liver abscess, but this is rare.

    Most amoebic liver abscesses are situated in the upper and back part of the right lobe. Small liver abscesses will probably resolve on specific therapy alone. Large abscesses require drainage which is best achieved by closed aspiration with a wide-bore needle. Unless specific and adequate therapy is given, the condition will recur.