HEPATITIS 237 



Fundamentally, however, the two kinds may not differ from 

 each other, since the large single abscess may become multiple 

 by infecting adjacent liver tissue giving rise to the develop- 

 ment of secondary abscesses. By coalescence a number of 

 small abscesses may by peripheral extension form a large 

 single abscess. 



Etiology. Liver abscess is always the result of infection 

 by microorganisms (staphylococci, streptococci) which reach 

 the liver in one of several ways: (a) Traumatism. In 

 small animals injuries, direct or indirect, frequently give rise 

 to abscess of the liver. Direct injuries, such as punctured 

 wounds, gunshot wounds, etc., permit the entrance of 

 pyogenic organisms. Indirectly contusions or rupture of 

 the liver, which reduce the resistance to infecting organisms 

 which may be circulating in the hepatic or portal blood. 

 Such usually produces a single, small or medium-sized abscess. 



(6) Diseases of contiguous organs often occasion the forma- 

 tion of abscess in the liver. Examples are: Gastric or 

 duodenal ulcer with perforation; abdominal organs which 

 have been operated and infected, and suppurative conditions 

 of adjacent organs. 



(c) Infection via the portal or hepatic circulation. Multi- 

 ple abscesses result from gangrene or abscess of the lungs, 

 purulent pleuritis, purulent and fetid bronchitis, etc. These 

 processes give rise to many infectious einboli which lodge in 

 the liver forming abscesses. 



(<7) Infection via the biliary ducts. Here abscess forma- 

 tion is due to the infection carried in through the bile ducts, 

 or by direct extension of ulcerative and suppurative processes 

 in the biliary tract to the adjacent liver tissue. 



(c) In some cases infection may take place through the 

 lymphatics. 



Pathology. Tin- appearance of the liver will vary greatly, 

 depending upon the mode of infection, the virulence of the 

 infecting material, and the location and number of abscesses. 



Abscesses resulting from traumatism, ulcerative and 

 suppurative processes in adjacent organs are usually single, 

 small or of moderate size, and mostly superficial. These 

 abscesses are in isolated areas, a focus of inflammation sur- 



