Liver biopsy guided by endoscopic ultrasound (EUS-LB) is an effective and safe technique for the study of liver diseases. However, there is limited scientific evidence regarding the technique (number of passes) and the difference in biopsy between the two lobes. Objective: To compare: 1) diagnostic yield, histological quality, and safety based on the number of passes, and 2) histological quality between the right liver lobe (RLL) and left liver lobe (LLL).

This is a retrospective, single-center study based on a prospective cohort of patients who underwent EUS-LB with a 19G-FNB needle between October 2020 and March 2025. For Objective 1, patients were divided into two groups: 3-4 passes (Group A) vs 2 passes (Group B). All patients were analyzed for the second objective.

A total of 168 patients were included (113 in Group A and 55 in Group B), with a median age of 57 years (range 45.25–66), and 109 women (64.9%). The overall diagnostic yield was 97.6%, with a median number of portal tracts (NPT) of 16.5 (range 10–24) and a median specimen length (SL) of 10 mm (range 10–15). The overall adverse events rate was 6.5%. No differences were observed in diagnostic yield or adverse events between Group A and B: (98.2% vs. 96.4%) and (6.2% vs. 7.3%), respectively. Regarding histological quality, no differences were found between the two groups in terms of total NPT, total SL, or NPT in the RLL/LLL. However, SL in the LLL was significantly shorter in Group B (median 10 (range 7.25–15) vs 7 (range 5–10) in group A; p=0.014). No histological differences were found between the two lobes; NPT/SL in the RLL: 7 (range 5–12)/10 (range 7–13) vs NPT/SL in the LLL: 8 (range 5–12)/10 (range 7–12.5).

Performing 2 passes by EUS-LB would be enough to achieve a high diagnostic yield. In cases of difficulty and/or technical impossibility, puncturing a single lobe would not affect the histological quality of the sample.