Objective To evaluate the application value of Laennec gap grading based on preoperative magnetic resonance imaging (MRI) in anatomic hepatectomy via the Laennec approach.

Methods The retrospective cohort study was conducted. The clinical and imaging data of 124 patients who underwent anatomic hepatectomy via the Laennec approach at Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School from January 2018 to December 2022 were collected. There were 57 males and 67 females, aged (54±13)years. All patients underwent laparoscopic or robotic-assisted anatomic hepatectomy via Laennec approach, with preoperative liver specific MRI examination. Observation indicators: (1) grading of Laennec gap in the inferior vena cava, middle hepatic vein, hepatic pedicle, and correlation analysis among them; (2) intraoperative and postoperative outcomes of patients with different Laennec gap grades; (3) correlation analysis between grades of the hepatic pedicle Laennec gap and the grades of liver fibrosis, inflammatory activity, steatosis. Comparison of measurement data with normal distribution between groups was conducted using the t test, and comparison among groups was conducted using one‑way ANOVA. Bonferroni adjusted t test was used for pairwise comparison. Comparison of measurement data with skewed distribution among groups was conducted using the Kruskal‑Wallis H test, and Dunn′s test was used for pairwise comparison. Comparison of count data was conducted using the chi‑square, continuity‑corrected chi‑square or Fisher exact probability. Correlation analysis was performed using Spearman′s correlation analysis.

Results (1) Grading of Laennec gap in the inferior vena cava, middle hepatic vein, hepatic pedicle, and correlation analysis. Among the 124 patients, the Laennec gap of the inferior vena cava was graded as 1, 2, and 3 in 59, 35, and 30 patients, respectively. No statistically significant difference was observed among these three groups in terms of gender, age, body mass index (BMI), preoperative hypertension, preoperative diabetes, history of abdominal surgery, co‑existing hepatitis C, surgical approach, or types of liver disease (P>0.05). However, a statistically significant difference was found in the incidence of co‑existing hepatitis B (P<0.05). The Laennec gap of the middle hepatic vein was graded as 1, 2, and 3 in 76, 33, and 15 patients, respectively. No statistically significant difference was observed among these groups in gender, age, BMI, preoperative hypertension, preoperative diabetes, history of abdominal surgery, co‑existing hepatitis B, co-existing hepatitis C, or types of liver disease (P>0.05). However, a statistically significant difference was found in the surgical approach (P<0.05). The Laennec gap of the hepatic pedicle was graded as 1, 2, and 3 in 47, 57, and 20 patients, respectively. No statistically significant difference was observed among these groups in gender, age, BMI, preoperative hypertension, preoperative diabetes, history of abdominal surgery, co‑existing hepatitis B, co‑existing hepatitis C, surgical approach, or types of liver disease (P>0.05). Spearman correlation analysis revealed pairwise positive correlations between the grading of the Laennec gap for the inferior vena cava, middle hepatic vein, and hepatic pedicle (P<0.05). (2) Intraoperative and postoperative outcomes of patients with different Laennec gap grades. Among the 59, 35, and 30 patients with grade 1, 2, and 3 of Laennec gap in inferio vena cava, respectively, the hepatic pedicle dissection time was (11.6±3.0)minutes, (10.1±1.9)minutes, and (8.3±2.1)minutes, and the target hepatic vein dissection time was 10(8,11)minutes, 8(8,10)minutes, and 6(5,9)minutes. The differences among the three groups were statistically significant (F=17.69, H=23.35, P<0.05). For hepatic pedicle dissection time, there were significant differences between patients with grade 3 and patients with grade 2 or grade 1 (t=3.62, 5.96,P<0.05), and there was a significant difference between patients with grade 2 and patients with grade 1 (t=2.82, P<0.05). For target hepatic vein dissection time, there were significant differences between patients with grade 3 and patients with grade 2 or grade 1 (Z=-2.47, -4.81, P<0.05), and there was no significant difference between patients with grade 2 and patients with grade 1 (Z=-2.17, P>0.05). Among the 76, 33, and 15 patients with grade 1, 2, and 3 of Laennec gap in middle hepatic vein, respectively, the hepatic pedicle dissection time was (11.1±2.9)minutes, (9.9±2.2)minutes, and (7.9±2.1)minutes, and the target hepatic vein dissection time was 10(8,11)minutes, 8(8,9)minutes, and 5(5,6)minutes. The differences among the three groups were statistically significant (F=12.60, H=32.03, P<0.05). For hepatic pedicle dissection time, there were significant differences between patients with grade 3 and patients with grade 2 or grade 1 (t=2.96, 5.02, P<0.05), and there was no significant difference between patients with grade 2 and patients with grade 1 (t=2.34, P>0.05). For target hepatic vein dissection time, there were significant differences between patients with grade 3 and patients with grade 2 or grade 1 (Z=-3.47, -5.55, P<0.05), and there was no significant difference between patients with grade 2 and patients with grade 1 (Z=-2.33, P>0.05). Among the 47, 57, and 20 patients with grade 1, 2, and 3 of Laennec gap in hepatic predicle, respectively, the hepatic pedicle dissection time was (11.8±3.0)minutes, (10.4±2.0)minutes, and (7.1±1.5)minutes, and the target hepatic vein dissection time was 9(8,11)minutes, 9(8,10)minutes, and 6(5,8)minutes. The differences among the three groups were statistically significant (F=45.12, H=12.36, P<0.05). For hepatic pedicle dissection time, there were significant differences between patients with grade 3 and patients with grade 2 or grade 1 (t=7.88, 8.52,P<0.05), and there was a significant difference between patients with grade 2 and patients with grade 1 (t=2.66, P<0.05). For target hepatic vein dissection time, there were significant differences between patients with grade 3 and patients with grade 2 or grade 1 (Z=-2.95, -3.45, P<0.05), and there was no significant difference between patients with grade 2 and patients with grade 1 (Z=-0.80, P>0.05). (3) Correlation analysis between grades of the hepatic pedicle Laennec gap and the grades of liver fibrosis, inflammatory activity, and steatosis. Spearman correlation analysis showed no significant correlation between the hepatic pedicle Laennec gap grade and the grades of liver fibrosis, inflammatory activity, or steatosis (P>0.05).

Conclusion Preoperative MRI allows for qualitative grading of the Laennec gap. A higher Laennec gap grade for the inferior vena cava, middle hepatic vein, and hepatic pedicle is associated with shorter dissection time for the hepatic pedicle and target hepatic veins.