Extraintestinal amoebiasis

When Entamoeba histolytica spreads outside a patient's gut, it usually involves his liver. Here it can cause an ''abscess' filled with liquid necrotic liver. To start with this is yellow or yellow-green, later it becomes a syrupy dark reddish-yellow (''anchovy sauce'). The central area of necrosis is surrounded by zones of progressively less damaged tissue and amoebae. The term amoebic liver ''abscess' is a bad one, because there is no pus.

His main symptom is gradually increasing pain in his right hypochondrium, or epigastrium. There is an 80% chance that his abscess is in the right lobe of his liver, where you will be able to detect it clinically, unless it is very deep.

Provided that there are no complications, metronidazole usually treats an uncomplicated liver ''abscess' very effectively, but if it does not, you will have to aspirate it or, rarely, to drain it. The major risk is that it will suddenly rupture into his peritoneal cavity, or through his diaphragm into his lung or pericardium. Rupture into the peritoneal cavity is a dramatic catastrophe, with collapse and peritonitis, like the perforation of a peptic ulcer. Although the contents of an abscess are sterile, they cause an acute inflammatory reaction in the peritoneum. Sometimes, an ''abscess' leaks into the peritoneum slowly, which makes the diagnosis more difficult.

The common mistakes are: (1) Not to do a sigmoidoscopy, or not to recognize amoebic ulcers when you do see them. (2) Not to remember the existence of acute necrotizing amoebic colitis with perforation. (3) Not to use all the evidence you can to diagnose a liver abscess.

EXTRAINTESTINAL AMOEBIASIS LIVER ABSCESS CLINICAL FEATURES. The patient is usually male (8:1 chance), and may be a child. In endemic areas (Durban) amoebic ''abscesses' are not uncommon in babies.

The pain in his right upper quadrant, or his lower right chest, is constant, not colicky, and does not radiate. It slowly gets worse, and is seldom severe. If it is in his chest, deep breathing and coughing make it worse.

Fever, anorexia, weakness, and loss of weight steadily progress. There is only a 30% chance that he has had diarrhoea with blood and mucus during the previous year. Often, he has some associated disease, such as tuberculosis, malnutrition, or alcoholism.

His liver is tender, smooth, diffusely enlarged, and without an obvious lump. Palpation may cause him much distress. Pressure over his lower 5 ribs in his right anterior axillary line is painful. Examine also for dullness at his right base, and decreased breath sounds.

SPECIAL TESTS. Leucocytosis (90% chance). Anaemia (haemoglobin [lt]100 g/l, 50%). Raised ESR. Raised serum alkaline phosphatase (50%). Look for amoebic ulcers with a sigmoidoscope (20%). You are unlikely to find amoebae in his stools.

X-RAYS. Look for a pleural effusion, and elevation of the right dome of his diaphragm (80%).

THE DIFFERENTIAL DIAGNOSIS includes a hepatoma, cholecystitis, a hydatid cyst, and a pyogenic liver abscess.

Suggesting a hepatoma (32.26)[md]a hard nodular mass, liver less painful and less tender, no fever or low fever (fever only occurs with very rapidly growing tumours), a bruit, bloody ascites.

Suggesting cholecystitis, perhaps with spreading suppuration (13.3)[md]the patient more often female, pain is colicky, tenderness is localized to the gall-bladder region, there may be a history of intolerance to greasy foods, jaundice.

Suggesting a hydatid cyst (31.13)[md]the mass arises from one or other lobe, rather than enlarging it diffusely; it grows slowly and is largely asymptomatic; it is smooth, tense, and cystic; tenderness is minimal, there is no fever, and his general condition is good. All this may change rapidly, if it becomes infected.

Suggesting a pyogenic liver abscess[md]a short history; he is severely ill and has a spiking fever.

Suggesting a perinephric abscess (5.11a)[md]the swelling is low down over his liver on the right; the distinction may be very difficult. Aspiration may establish the site.

CHEMOTHERAPY. See Section 31.10. If he is very ill, give him metronidazole and dehydroemetine (or emetine).

LIVER ASPIRATION [s7]FOR AMOEBIC ABSCESS INDICATIONS. (1) To confirm the diagnosis, if, for example, his response to metronidazole has been poor. (2) As a method of treatment when an abscess is very large, or might burst. Aspiration is only necessary in about 20% of cases. Your chances of finding ''pus' are about 80%. You will fail if it is very deep.

METHOD. Using local anaesthesia and full aseptic precautions, pass a wide-bore ([mt]1 mm) spinal needle on a 50 ml syringe, through healthy skin, over the site of greatest swelling, or maximum tenderness. Or, if there is no swelling, insert it in his 9th intercostal space in his mid axillary line. Push it in to a depth of not more than 8 cm.

If you don't find ''pus' on your first attempt, insert it in a slightly different direction. The pus may be thick and aspiration difficult, or you may withdraw several litres with ease. Don't inject any drugs.

If you obtain more than 250 ml, repeat the aspiration a few days later. You have only about a 10% chance of finding amoebae in the pus. They are more often found in the wall of the cavity.

OPEN DRAINAGE [s7]FOR AMOEBIC LIVER ABSCESSES INDICATIONS. This is rarely necessary if you have given him metronidazole, and aspirated his abscess adequately. (1) You think he has a deep-seated amoebic liver abscess, but have not proved it, and he is deteriorating on medical treatment. (2) The pus is too thick to aspirate. (3) Very large abscesses, which need repeated aspiration. (4) An abscess in the left lobe which may perforate into his pericardium. (5) Secondary infection of the abscess. (6) The diagnosis is uncertain; you think he may have a hydatid cyst, which might rupture and cause a possibly fatal anaphylactic shock, if you tried to aspirate it through his abdominal wall. (7) In an emergency, after an abscess has ruptured into his peritoneal cavity.

DRAINAGE. Make a subcostal incision, and insert an aspirating needle directly into the abscess cavity, to identify it. Push artery forceps into it, open them and suck out the pus. Take some material from the advancing edge of the lesion, and examine a warm wet specimen for amoebae.

A drain may not be necessary, but if there is much discharge, insert a tube drain, and bring this out through his abdominal wall.

If his abscess is very large, his liver will recede from his abdominal wall as you drain it, and end up as a shrunken blob, in his right upper abdomen, 20 cm from the incision through which the drain will go. To prevent gut sticking to the drain, cover it with omentum.

Remove the drain soon, probably in 6 or 7 days, to minimize the risk of secondary infection from outside. Meanwhile, continue chemotherapy.

IF YOU HAVE ULTRASOUND with which to localize the abscess, introduce a multiholed plastic catheter with a three way tap, and aspirate it, until it is apparently empty. Every few days, introduce a suitable contrast medium through the tube, take a film to outline the cavity, and aspirate it empty. Consider injecting an amoebicide. Continue until the cavity is empty and then remove the tube.

DIFFICULTIES [s7]WITH EXTRAINTESTINAL AMOEBIASIS If he has a SUDDEN PAIN like a perforated peptic ulcer, his abscess has probably ruptured into his peritoneal cavity. Resuscitate him, and start intensive amoebicidal treatment. When his general state is satisfactory, open his abdomen.

Make an upper right paramedian or Kocher's incision. Explore his liver, as best you can, and look for the site of the rupture[md]a ragged area with chocolate-coloured fluid pouring from it. Suck out as much of this you can. Mop up what you cannot aspirate. Irrigate all the crevices of his peritoneum with several litres of warm saline with tetracycline (6.2). Slosh it around and suck it out. Do a thorough lavage, and close his abdomen. Close the main incision with tension sutures. Continue metronidazole, and treat his peritonitis with nasogastric suction, etc. (6.2).

If he has TENDER ILL-DEFINED MASSES IN STRANGE PLACES, suspect that his abscess has leaked into his peritoneal cavity. Give him intensive medical treatment, and monitor his abdomen closely. Mark the outline of any mass, and check its size regularly.

If an ABSCESS PRESENTS ON HIS CHEST WALL, it will ultimately rupture through his skin, which may become infected with amoebae, and form a chronic ulcer as in A, Fig. 31-10. He should respond to metronidazole.

If he has an ULCERATING SKIN LESION round a sinus from his liver, caecum, or anus, remember the possibility of CUTANEOUS AMOEBIASIS. Metronidazole cures cutaneous amoebiasis so fast, that you can use it as a diagnostic test. Tuberculosis, malignancy, and fungi are commoner causes in most areas. In the perianal area ulcerating skin lesions are usually non-specific.

If he develops a SEVERE COUGH AND DYSPNOEA, this may, or may not, mean that he has a pleural effusion. If an effusion is small, it will resolve as his liver abscess improves. If it is large (unusual), aspirate it. If necessary, insert a tube drain, connected to an underwater seal or suction bottle. His liver sticks to his diaphragm and his lung, so he is more likely to cough up amoebic pus (see below), than for pus to enter his pleural cavity.

If he COUGHS UP ''ANCHOVY SAUCE', his liver abscess has ruptured into a bronchus. Although this may drain the abscess, it may also flood his bronchial tree and kill him. X- ray his chest; the appearances are characteristic, with pus tracking in his greater fissure. Give him metronidazole, aspirate his liver abscess, and use postural drainage.

If his liver abscess DISCHARGES INTO HIS PERICARDIUM it usually does so from an abscess in his left lobe. Pericardial rupture is not uncommon in endemic areas, is often not recognized, and is usually fatal. Watch for abscesses in the left lobe, and aspirate them (6.1a).

If his ABSCESS BECOMES SECONDARILY INFECTED, one reason may be that you punctured his transverse colon on your way to his liver.

Fig. 31-11 HYDATID CYSTS OF THE LIVER. A, to F, some of the cysts you may find. C, will need a thoraco-abdominal incision. G, a patient with a single cyst. H, abdominal distension due to multiple hydatid daughter cysts throughout the peritoneal cavity. After Goinard et al.