What is the most common cause of hepatic abscess in adults in the USA?

Most Common Cause of Hepatic Abscess in the USA

In the United States, biliary tract disease is the most common cause of pyogenic hepatic abscess, accounting for approximately 29-52% of cases, with the incidence increasing significantly in recent decades due to more aggressive management of hepatobiliary and pancreatic malignancies. 1, 2

Primary Etiologies in the USA

The etiology of hepatic abscesses in the United States has evolved over the past several decades:

Biliary Tract Disease (Most Common)

• Biliary tract disorders represent the leading cause of pyogenic liver abscesses, including cholangitis from common bile duct stones, inflammatory strictures, and malignancies 1, 2
• Approximately 29% of cases in earlier series, increasing to over 50% in more recent cohorts as hepatobiliary malignancies and their aggressive management have become more prevalent 1, 2
• Biliary obstruction from any cause—stones, tumors, or post-procedural complications—creates the pathway for bacterial seeding of the liver 3

Portal Venous Seeding

• Portal venous seeding from intra-abdominal infections is the second major pathway, particularly from diverticulitis and appendicitis 3
• Other intra-abdominal infections commonly serve as the underlying source 4

Malignancy-Associated Abscesses

• Underlying malignancy has increased dramatically as a contributing factor, present in 52% of patients in recent series (1973-1993) compared to only 28% in earlier decades (1952-1972) 1
• Most of these malignancies (81%) are hepatobiliary or pancreatic cancers 1
• This shift reflects more aggressive surgical and interventional approaches to hepatobiliary malignancies 1

Important Clinical Context

Changing Epidemiology

The incidence of hepatic abscesses in the USA increased from 13 to 20 per 100,000 hospital admissions between the early 1970s and 1990s 1. This trend reflects:

• More aggressive management of hepatobiliary malignancies 1
• Increased use of biliary interventions (ERCP, stenting) that can lead to iatrogenic abscesses 5
• Better diagnostic capabilities with CT and ultrasound 1

Bacteriology Patterns

The microbiology has also shifted in the USA:

• Streptococcal species are now most common (53% of recent cases vs. 30% historically) 1
• Klebsiella remains prevalent (33% in some series) 2
• Enterococcus is common (29% of cases) 2
• Pseudomonas has increased (30% vs. 9% historically) 1
• Mixed bacterial and fungal infections have risen dramatically (26% vs. 1%), particularly in immunocompromised patients and those with malignancy 1

Critical Pitfalls to Avoid

Do not overlook biliary pathology when managing hepatic abscesses—radiologic investigation must identify not only the abscess but also underlying biliary obstruction or disease, as failure to address the biliary source leads to treatment failure and recurrence 6, 4

Post-procedural abscesses after ERCP or biliary surgery can develop anywhere from 10 days to 14 months after the procedure and require both abscess drainage and management of the underlying biliary pathology 6, 5

Abscesses with biliary communication will not heal with percutaneous drainage alone and require endoscopic biliary drainage (sphincterotomy plus stent or nasobiliary catheter) 4, 3

Geographic and Demographic Considerations

While amebic liver abscess caused by Entamoeba histolytica is the most common cause globally (particularly in endemic areas), it is relatively uncommon in the USA except in travelers or immigrants from endemic regions 7. In the USA, pyogenic (bacterial) abscesses dominate, with biliary disease as the primary etiology 1, 2, 7.