This is perhaps the commonest of all affections of the liver. The names Nutmeg liver and Red atrophy ue sometimes given in cases of prolonged passive hyperemia, these names indicating certain appearances presented by the tissue. Passive hyperemia occurs when any obstruction exists in the circulation of such a nature as to interfere with the return of blood from the inferior vena cava to the right side of the heart. The commonest cause is valvular disease of the heart, especially mitral disease, but it also results from obstruction to the pulmonary circulation as in bronchitis and emphysema, etc. In these cases there is a general engorgement of the systemic venous circulation, with increase of blood-pressure in the veins. As the normal circulation in the liver is unusually slow, and the blood-pressure low, any increase in the blood-pressure in the general venous circulation will tell particularly on the vessels of the liver, and we may even suppose that the blood passing up the inferior cava may in such cases regurgitate into the hepatic vein.

The result of this is very great distension of the hepatic vein and its radicles - the central or intralobular veins. The distension extends to the capillaries, which, as in Fig. 404, are sometimes found enormously dilated. The dilated capillaries by pressure cause Atrophy of the hepatic cells, and it often happens that the central parts of the lobules are entirely occupied by enormously dilated capillaries, while the hepatic cells are hardly visible (see figure). The remains of the hepatic cells frequently contain brown Pigment granules. The atrophy of the hepatic cells in these regions may be complete, only a few pigment masses representing them. Sometimes, instead of a simple atrophy we have Patty degeneration of the hepatic cells, localized in the central parts of the lobules.

Passive hyperemia of the liver.

Fig. 404. - Passive hyperemia of the liver. One lobule and parts of two others are shown. In the central parts of the lobules there is almost nothing but dilated capillaries containing blood-corpuscles; a few atrophied and pigmented hepatic cells being visible. At the peripheral parts of the lobules the hepatic cells are seen, many of them pigmented, x 50.

Sometimes in addition to these changes there is a hypertrophy of the connective tissue surrounding the lobules, but this is usually inconsiderable, and it is a mistaken view that a cirrhosis of the liver arises out of passive hyperemia.

To the naked eye the organ appears unduly red. On close examination even of the general surface, but more specially of the cut surface, it is seen that there are minute areas of a deep red colour corresponding with the central parts of the lobules, and these are surrounded by zones of a grey or yellowish colour. The result is that the lobules are, as it were, mapped out by these contrasting colours, and are for the most part individually visible to the naked eye. Sometimes several adjacent lobules are almost completely occupied by dilated vessels, and there is a narrow ring of normal tissue around each, so that the portion of liver has, as a whole, an almost cavernous structure and presents a deep red colour on section. It is these variations in colour and figuring which give the cut surface the appearance of the section of a Nutmeg.

In parts where there has been great loss of the proper tissue, the liver may appear to the naked eye after death partially atrophied. During life the dilated veins and capillaries are distended with blood, but after death, tlje blood-pressure- being removed, these may, to some extent, collapse. In this way the surface has sometimes a granular appearance, which may be mistaken for that of cirrhosis, but it will be noticed that the depressed or atrophied parts have a deep red colour.