A total of 36 male New Zealand White Rabbit weighting 2.77 ± 0.15 kg were purchased from New Zealand. All rabbits were maintained separately in galvanized wire pens (35 × 35 × 60 cm) with freely accessible feeders (ad libitum) and a freshwater outlet under the same management and hygienic conditions, namely a regimen of 12 h light and 12 h dark, natural ventilation, an average temperature of 25°C and a relative humidity of 50%. All surgeries were performed under chloral hydrate anesthesia, and all efforts were made to minimize suffering.

4-0 non-absorbable suture (Prolene Polypropylene Suture) and 4-0 absorbable suture (STRATAFIX™ Symmetric Monocryl™ Plus) from Ethicon.

Rabbits were randomly divided into 3 groups (N = 36) after a 1-week acclimation. Rabbits in all groups underwent side-to-side jejunoileal anastomosis plus proximal loop ligation except for the control group (the mesenteric defects is closed with different sutures). Body weight and food intake after surgical procedures were monitored and recorded.

After overnight fasting and water deprivation, the animals were anesthetized with pentobarbital sodium intravenously at the ear margin (30 mg/kg). The abdomen was shaved and an incision of approximately 10 cm was made from the subxiphoid process to the mid-abdomen, thereby entering the abdominal cavity.

The total length of the small intestine, measured from the Treitz ligament to the ileocecal valve, was recorded, and 30% of this length was calculated. Starting 15 cm distal to the Treitz ligament, an isoperistaltic side-to-side anastomosis was performed with the distal small intestine to restore intestinal continuity (bypassing 30% of the total small bowel length). The enteric anastomoses were completed using 3-0 absorbable sutures. Subsequently, the intestinal tract was ligated 1 cm away from the anastomotic site with 0 silk suture (Figures 1A–C). The mesenteric defect was then closed using continuous suturing, with 4-0 non-absorbable suture in one group (Figure 1D) and 4-0 absorbable suture in another (Figure 1E). Finally, the abdominal cavity was closed in two layers using 3-0 non-absorbable sutures.

Following skin preparation and disinfection, a 10-cm midline incision was made to access the peritoneal cavity, and the intestine was gently manipulated. The abdominal cavity was closed in two layers using 3-0 surgical sutures.

The operative time for rabbits in all groups was maintained within 12 ± 10 min. Postoperatively, the animals were placed in individual cages to recover from anesthesia. All rabbits were fasted for the first 24 h following surgery, after which they were provided unrestricted access to standard chow and tap water from the first postoperative day until the conclusion of the experiment.

All rabbits were weighed once a month and euthanized by exsanguination under deeply anesthetize (30 mg/kg pentobarbital sodium intravenously at the ear margin) after 3 months. The lifespan of a New Zealand rabbit is approximately 7–8 years, compared to about 80 years in humans (7). A 3-month experimental period in rabbits is roughly equivalent to 2.5–3 years in humans. Therefore, we consider the 3-month observation period to be justified.

The abdominal cavity was opened to examine the mesenteric defect adhesions and assess any changes in the suture material in both groups. The degree of adhesion was evaluated using a semi-quantitative grading method based on Blauer's criteria (8) (Table 1).

A 2 cm × 0.5 cm piece of mesenteric tissue at the site of normal tissue and mesenteric hiatus was taken and its maximum tension was measured with instruments for measuring tensile force (Figure 2A).

Mesenteric tissue samples were first fixed with a 4% paraformaldehyde solution. Tissues were obtained after fixation and paraffin blocks were obtained after routine procedures. The resulting 5 µm serial sections were stained with H&E. The sections were then viewed with an Olympus BX 51 light microscope.

The changes in Food intake, Body weight, and Adhesion scores are expressed as mean ± standard deviation (SD).Differences between the groups were assessed by one-way analysis of variance (ANOVA, LSD post-test). P < 0.05 was assumed significant difference. Statistics were performed using SPSS, version 18.0, statistical software (SPSS Inc., Chicago).

The SSJIBL model was successfully established in all rabbits within the experimental groups. All animals survived the surgical procedure and completed the 12-week follow-up period (Figures 2B,C). Notably, we observed that the bypassed segments of the small intestine exhibited varying degrees of atrophy in nearly all groups after 12 weeks (Figure 2D). Additionally, in Group Absorbable Suture, one rabbit developed severe ascites following the SSJIBL procedure (Figure 2E).

All New Zealand rabbits were dissected after 12 weeks, and no internal hernia was observed in both experimental and negative control group.

Adhesion scores were significantly higher in groups Absorbable Suture and Non-absorbable Suture than in group NC, but there was no significant difference between groups Absorbable Suture and Non-absorbable Suture (Figure 3A).

The maximum maximal tension of the normal mesenteric tissue was similar to that of the mesenteric tissue at the site of the closed mesenteric hiatal hernia and was not statistically different, both in group Absorbable Suture and group Non-absorbable Suture (Figure 3B).

Based on the H&E staining, we can see adipocytes between the tissues of all three groups and an infiltration of inflammatory cells in both Group Absorbable Suture and Non-absorbable Suture, which, according to our guess, is the reason for the formation of firmer adhesions (Figure 4).