Over two thousand years ago, Hippocrates,¹ observed that when an abscess of the liver is treated by cautery or incision, if the pus discharged is pure and white the patient recovers, but if it resembles less of oil as of cloves they may die! Thus, he recorded that open drainage of a nonpyogenic abscess (the pus of which was less of oil as of cloves) had a much higher mortality than that of a pyogenic abscess (the pus of which was pure and white). In spite of being aware of this fact, incision and drainage of an amoebic liver abscess was being routinely practised even as late as 19th century. In order to reduce this high mortality, Mclean in 1871 advocated simple aspiration of the pus. This was soon endorsed by Rogers,² Hooton³ and others,⁴ who expounded on its comparative safety. Thus to-day, although with the introduction of better amoebicidal drugs a more conservative attitude has developed, aspiration remains one of the primary methods of treating an amoebic liver abscess. ^4,5 However, some others contend that in recent years the percentage of patients requiring needle aspiration has fallen markedly. Table I demonstrates these changes in the attitude towards the management of amoebic liver abscess.⁶

Indications
Any amoebic liver abscess, once diagnosed, should initially be treated with amoebicidal drugs. However, if no clinical improvement occurs within 48 to 72 hours⁷ one should not delay aspirating the abscess. All large abscesses (especially those presenting as localised swellings or bulges of the right lower hemithorax), superficial abscesses, abscesses causing severe pain or having marked point tenderness or oedema and abscesses with marked elevation of the diaphragm should be aspirated as early as possible.

TABLE I

A clinical picture suggesting an impending perforation^7-9 (the pre-rupture syndrome) and cases of left lobe abscess, where fatal complications of rupture into the pericardial sac or peritoneal cavity can occur at any time⁷ are indications for immediate aspiration.
Whenever the diagnosis is in doubt, it is preferable to institute conservative treatment rather than risk entering a hydatid cyst with consequent anaphylactic shock, or a haemangioma which may result in internal haemorrhage¹⁰ It is also preferable to delay aspiration in unco-operative patients and those with bleeding disorders to prevent unfortunate accidents.

Preparation
Amoebicidal therapy must be instituted prior to aspiration.^8,11 It is also wise to carry out investigations like routine blood count, prothrombin time, bleeding and clotting time and blood grouping and cross matching.⁴ The latter few tests are often omitted in busy overcrowded Indian wards. Vit. K. may be prescribed if there is the slightest evidence of jaundice or a raised prothrombin time.

Procedure
The patient is made to fast for six to eight hours. To counteract vagal shock atropine is injected in a dose of 0.6 mg. half an hour before the procedure. As far as possible sedation with morphine or pethidine should be avoided as it may mask the early manifestations of ensuing complications. Moreover these drugs themselves may damage the liver.⁴ Injection diazepam may be given l.V. in a dose of 2 to 10 mgm. The procedure should be carefully explained to the patient.
Ideally, aspiration should be undertaken in an operation theatre and the attendant should be masked, gowned and gloved as for any other surgical procedure. Meticulous attention must be paid to asepsis^8,12,13 as bacterial infection in an amoebic abscess worsens the prognosis considerably.⁹ (To demonstrate the 'site of aspiration' in relation to prominent anatomical landmarks, the patient has not been draped as seen in many slides in this monograph).
The site for aspiration is next determined as per following criteria:

1. Presence of a pointing abscess, mass in the liver or a localised bulge of the chest wall.
2. The location of point tenderness.
3. In the absence of a definite point tenderness, the needle may be introduced either in the ninth intercostal space in the mid-axillary line or the seventh intercostal space in the mid-clavicular line.^{7,8 11-13}
4. Postero-anterior or lateral X-rays of chest would often indicate the site of puncture. Liver scan, if available, is much more useful. Ultrasonography is the most accurate investigation available to guide the needle to the right spot. This investigation also indicates the depth to which the needle has to be introduced.
5. When an abscess is pointing and the overlying skin is taut and thin, the puncture should be made in the surrounding healthy skin to avoid sinus formation and subsequent secondary infection.

The position of the patient is determined by the site chosen for the puncture. If anterior or lateral, the patient lies semi-recumbent leaning against a back-rest; if, however, the site is posterior, the patient is made to lean forward on a cardiac table. The selected area after being subjected to meticulous surgical toilet is infiltrated with 4 to 5 ml. of 5% Xylocaine using a 4" twenty four gauge needle. Infiltration should include the diaphragm and tissues upto the capsule of the liver. Adequate time of about 5 minutes should be allowed for the anaesthetic to act.
In a small percentage of cases, the periphery of the abscess is so close to the chest wall, that pus is struck even with the small needle through which the local anaesthetic is given.
A small puncture with a stab knife maybe made in the skin at the site of needle puncture. This reduces any chance of needle carrying skin bacteria into abscess cavity and permits free movement of the needle inside to aspirate the entire contents completely.
Percutaneous aspiration may be done with any large bore (No. 18) or lumbar puncture needle. Paul¹⁴ recommends the use of a fine bore to minimise hepatic haemorrhage. He maintains that the pus has viscosity of thick lubricating oil and therefore, can flow through a small bore needle.
While the needle is being introduced or withdrawn, the patient is asked to take shallow breaths throughout the procedure and hold his breath to -minimise liver trauma. While aspirating, every attempt should be made to avoid traversing the pleural or peritoneal cavity.⁸
Once the needle enters the abscess cavity, pus often gushes out if it is under pressure. A 20 ml. syringe is now attached and used to create a negative force which can be regulated according to the resistance to the flow of pus.¹⁴ A bi-valve greatly facilitates the procedure.¹² If pus is not encountered even after inserting the needle in two or three directions, the procedure should be abandoned. The practice of multiple exploratory thrusts in different directions should be deplored. When an abscess just cannot be located, laparotomy is safer.⁹ However, the latter is rarely ever necessary in centres where nuclear or ultrasonic liver scans are available. According to Desa,¹⁵ 10 cms. is the limit to which an aspirating needle may be inserted so that inadvertent puncture of the portal radicle is averted. If the site of entry is carefully planned, almost every abscess is within this limit. Abscesses at a distance of 12.5 cms., which would need exploratory operation have also been described.¹⁵
The procedure should be abandoned if the patient appears distressed.
Aspiration is continued until no more pus can be evacuated. Cases are on record where 6,100 mis. Of pus were aspirated at four different sessions.¹⁶ The last part of the aspirate commonly has a more bloody appearance and at this stage the patient may experience an aching pain in the liver or over the right shoulder. Occasionally he may even start coughing. The terminal aspirate is particularly rich in trophozoites and, therefore, should be sent immediately for smear and culture. It is usually not possible to evacuate completely as the abscess walls cannot collapse much. However, healing occurs even in the presence of residual pus. As this pus is not under pressure, there is no risk of a leak along the aspiration track.¹⁴ Injecting amoebicidal drugs into the abscess cavity in no way hastens healing but may ensure that no spread of amoebic infection follows the needle tract.
The puncture wound is sealed with tincture Benzoin Co. or gauze. A tight plaster may be put covering the right lower chest. A similar objective is achieved if the patient is Iying on the side with the weight of the chest pressing the site of puncture. Analgin may be injected to alleviate pain. For the first twelve to twenty four hours a half-hourly watch is kept on the temperature, pulse, respiration and abdominal girth so that signs of haemorrhage or peritonitis are not missed. For the same reason it is preferable to avoid sedation. Once haemorrhage or peritonitis are diagnosed, blood transfusion should immediately be started and preparation made for laparotomy.

Complications
The complications more commonly encountered are secondary infection and haemorrhage.
Aspiration constitutes one of the routes by which bacteria can enter an amoebic liver abscess and secondarily infect it.⁹ (The other routes are haematogenous⁹ or after rupture into the lung, viscus, etc.). Watsona⁷ also suggested that secondary bacterial infection is often endogenous in origin occurring after primary aspiration, due to disintegration of the lining wall of the cavity, allowing the entrance of portal blood containing organisms from the damaged bowel.
Clinically, if the patient remains toxic and the fever does not settle down inspite of vigorous therapy, a secondary infection should be suspected. If aspiration is now repeated the pus is usually found to be thinner, yellowish in colour and may have an odour. A Gram stained slide may demonstrate the organism.
When such a complication occurs, vigorous treatment with specific antibiotics (dictated by a culture sensitivity test) should be administered in addition to the normal amoebicidal therapy. Aspiration will greatly aid recovery. Most cases will respond to this line of treatment. If the patient shows no improvement or the amount of pus aspirated at each session does not diminish, open drainage may be considered.⁹
Haemorrhage could occur during or after the procedure and could be associated with tear of the liver substance. Intrahepatic haematoma (Fig. 1), peritonitis, pleural effusion, pneumothorax and death due to vagal shock have been described. Amoebic ulcer formation at the site of aspiration has also been reported.

Dry tap
Failure to aspirate pus indicates wrong technique, improper localisation of the abscess or a mistaken diagnosis. On some occasions, an abscess may he filled with a solid jelly like substance which will not flow through any canula no matter how wide. Such lesions are, however, rare.

Repeated aspiration
The number of aspirations required in any patient is dictated by the clinical response. In general it may be said that if more than 200 ml. pus is removed, further aspiration in two to three days' time should be done.
Repeated aspiration is usually indicated in patients with a large abscess in whom the symptoms persist or worsen a few days after the primary aspiration. Persistence of X-ray signs after primary evacuation of a sufficient quantity of pus also constitutes an indication for repeating the aspiration.
Rao et al¹⁸ while treating thirty cases of amoebic liver abscess, carried out from four to as many as twenty aspirations, their average being eight in number. At any one time, they continued to aspirate until no more pus could be obtained. (However, in this series, resolution of an amoebic liver abscess, by injecting air as a negative Contrast medium, was being studied.)

Laparotomy aspiration
Sometimes laparotomy may he necessary for aspirating an abscess not safely approachable percutaneously. This situation arises more often in left lobe abscesses and in infants and children in whom multiple abscesses inaccessible to percutaneous aspiration are more frequent.
In some inferior surface abscesses, not easily approachable percutaneously, the aspiration needle may be guided by direct peritoneoscopic visualization thereby avoiding surgery (Fig. 29 Section III
On occasions, when an unsuspected intrahepatic amoebic abscess is found at an operation undertaken for some other diagnosis, it should be evacuated by needle aspiration. If no bacteria are seen in a smear of an aspirate appearing to be amoebic in nature, open drainage should be avoided.
Aspiration is not mandatory for recovery in all cases of amoebic liver abscess.^8,19-21 Nevertheless, removal of pus often promptly relieves the pain and greatly improves the patient's clinical condition. Adequate aspiration hastens recovery⁹ although addition of needle aspiration to conservative amoebicidal therapy does not significantly alter the resolution time of an amoebic liver abscess. ²²

References

1. Aphorisms, 45 Sec. 7 [IN] Adams, The Genuine Works of Hippocrates, Wilhams & Wilkins CO., Baltimore, 1939.
2. Rogers, L, Brit. Med. J., 1903, 2,1246.
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4. Ochsner, A, and DeBakey, M E, Surg cyn. Obst. (I.A.S.), 1939, 69, 392.
5. Bailey, H. and Love M, A Short Practice Of Surgery, 17th Edition, Ed. by A G H Rains and H D Ritchie, H K Lewis & Co., London, 1977.
6. Bautista O'Farrill, J. Proc. Internat. Conf. on Amoebiasis, 1975, Ed. by Sepulveda, B. and Diamond, L s, Instituto Mexicano Del Seguro Social, Mexico, 1976.
7. Bockus, H L, Gastroenterology Vol. IV, 3rd Edition, W B Saunders & CO., Phiiad., 1976.
8. Davis L, Christopher's Text book of Surgery, 11th Edition, W B Saunders & CO., Igakussion Asian ed, Tokyo, 1968.
9. Wilmot, A J. Clinical Amoebiasis, Blackwell Scientific Publications, Oxford, 1962.
10. Vakil, R J. A Text book Of Medicine, 17th Edition, Ass. Phys. Ind., India, 1973.
11. Schwartz, S L, Principles Of Surgery, Vol. II, 2nd Edition, McGraw-Hill Book Co, New York, 1974.
12. Sherlock, s, Diseases Of the Liver and Biliary System, 5th Edition, Blackwell Scientific Publications, oxford, 1977.
13. Ochsner, A, "Infections of the Liver" in Maingot's Abdominal Operations, Vol. I, 5th Edition, Appleton Century Crofts, Publishing Division Prentice Incorporation, New York, 1974.
14. Paul Milroy, Brit J Surg, 1960, 47, 502.
15. Desa, A E, Progress Drug Res., 1974, 18, 77.
16. Islam, N. J. Trop. Med. Hyg, 1967, 70, 68.
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18. Rao, R S, Murthy, K J R. et al, Am. J Gastroent., , 60, 372.
19. Cohen, M G. and Reynold, T B, Gastroent., 1975, 69, 35.
20. Griffin, F M, New Eng. J Med., 1973, 289, 869.
21. Turrill, F L, and Burnham, J R. Am J. Surg, 1966, 11, 424.
22. Sheehy, T W. Parmley, L F. et al, Gastroent.,1968, 55, 26.