Viral, bacterial infections and enterotoxins have been proposed as etiopathogenetic factors causing PBCTherefore we prospectively investigated the number and size of lymph nodes (LN) expressed as the total lymph node volume @NV) within the hepatoduodenal ligament (HDL) in 48 consecutive patients with PBC and in 43 healthy controls (hc). Methods: In the present study the LN in the liver hilus were evaluated by high resolution ultrasound (Acuson 128, 3.5 MHz) in 48 consecutive patients with PBC (age: 54 f 9 years, 5 male, 43 female) and in 43 hc (53 f 8 years, 6 males, 37 females). The tLNV of all detected LN was recorded for each region. The stages I-IV of PBC were biochemically and histologically proven in all patients. Results: In 43/48 patients with PBC (89.6%) and in 39/43 hc (90.7%) adequate visualization of the liver hilus was achieved. LN were detected in all patients with PBC and in 26139 hc (66.7%). The mean tLNV (mtLNV) was 22 f 16 cm3 in the PBC group compared to 1.9 f 2.0 cm' in the hc (p <O.OOOl). The mtLNV in patients with PBC stage I, II, III, and IV were: stage I (n = 7): 7. I & 4.0 cm3, II (n = 20): 17.5 f 10.8 cm', III (n = 15): 34.2 * 17.4 cm3, and IV (n = 6): 27.4 * 8.3 cm3, respectively. The differences between tLNV in patients with PBC stage I and II (p = O.OOS), stage II and III (p = 0.002) were signiticant, whereas no significance was observed between patients with stage III and IV @ = 0.2). Conclusion: Enlarged lymph nodes within the hcpatoduodenal ligament are sonographically detectable in almost all patients with PBC. This lymph node enlargement could reflect extrahepatic immunological activity and may be a marker of disease activity and could be helpful in the diagnosis and staging of PBC.