As early as 1902, Rogers¹ had put forth the hypothesis of direct extension of amoebic infection from the hepatic flexure to the liver, because he had noticed an abscess in the right lobe very near the surface.
In the past, many authorities have described an amoebic liver abscess reaching the surface before it ruptures. Based on my experience in the autopsy room and clinical wards, I am convinced that amoebic liver abscesses are of two types (i) deep (intrahepatic) and (ii) superficial.
Figure 8 shows an example of common, deep seated liver abscess seen at the autopsy. Figure 3 in Section 11 shows an example of a superficial abscess causing a bulge on the surface of the liver as seen at autopsy. Figure 9 is another such example. Figure 9a shows such an abscess as seen in the lateral view of the X-ray chest.

The importance of a superficial abscess is:

1. It is likely to rupture much earlier than a deep seated abscess, since the latter will take some time to reach the surface.
2. Superficial abscess of the right lobe is more likely to cause a "pre-rupture" syndrome which has been discussed in an earlier section (Fig. 9b).
3. A superficial abscess may not show a clear cut cold area on the liver scan, thus making the diagnosis difficult.
4. Many of the intrahepatic abscesses will respond to drugs without aspiration, while most of the superficial abscesses must be tapped to avoid rupture, a complication which worsens the prognosis.

Superficial abscess of the left lobe
A superficial abscess on the anterior surface may present in the epigastrium (Fig. 10).
As discussed in an earlier section, a superficial abscess on the superior surface often ruptures into the pericardium or the left pleural cavity before it is detected.

Superficial abscess of the right lobe
One of our patients presented with pain and tenderness in the right lower chest and the right shoulder. All the symptoms and signs were consistent with an abscess on the superior surface of the right lobe. I.H.A. test was positive in a dilution of 1: 2024. X-ray chest (Fig. 11) showed a small pleural effusion and the pleural tap yielded 300 ml. of straw coloured fluid. Liver scan (Figs. 12 a,b,c) did not show a clear cut cold area though the superior surface did not appear to be absolutely normal. Diagnostic liver aspiration yielded 30 ml. of very thick brownish pus (Fig. 13). The above case is, an example of superficial abscess of the superior surface of the right lobe (Refer Chapter 3-section 111).
Figures 14 a,b,c,d,e show the X-ray, the scan and aspirates of a similar patient. This was a young lady in early pregnancy in whom tapping of the liver abscess revealed 40 ml. of thick brownish pus while pleural tap revealed 200 ml. of straw coloured fluid.
Another patient had a tender superficial swelling in the right flank (Fig. 15). I.H.A. test was positive in 1 :2024 dilution. The liver scan did not show a well defined cold area, yet hepatic aspiration revealed 180 ml. of brown pus. This is an example of a superficial abscess of the inferior surface. (Refer section 111).
Thus, if a patient diagnosed clinically as amoebic liver abscess has signs at the right base of the chest or a superficial lump in the liver and the serological tests are in favour of amoebic liver abscess, there should be no hesitation in doing a tap, though the liver scan may not show a well defined cold area.

References

1. Rogers L, Brit Med J. 1902, 2, 844