Inguinal hernia is one of the most common conditions in general surgery. In clinical practice, surgeons frequently face a dilemma: during the evaluation of a patient with unilateral symptomatic inguinal hernia, a contralateral asymptomatic defect is discovered-either preoperatively on physical examination or intraoperatively during laparoscopy. The question then becomes: how should this incidental finding be managed? Epidemiological data show that the incidence of such contralateral asymptomatic hernias can be as high as 20%. The management strategy for these hernias has changed considerably over time. Although traditional "watchful waiting" was once widely adopted, long-term follow-up studies have demonstrated that approximately 70% of asymptomatic patients eventually require surgery due to symptom progression, and increasing age is associated with higher surgical risks. Consequently, with the widespread adoption of laparoscopic techniques, simultaneous repair of asymptomatic hernias during the initial surgery has become a common clinical choice.

However, this decision raises a critical question: how can the surgeon balance the need to repair the existing anatomical defect against the risk of introducing new long-term complications from the intervention? This makes the choice of repair material particularly important. Currently, synthetic polypropylene meshes, with their proven effectiveness in reducing recurrence rates, are considered the gold standard for inguinal hernia repair. However, as permanent implants, they may be associated with long-term complications-chronic postoperative pain and foreign body sensation, which affect patients' long-term quality of life.

Biologic meshes offer a different option. Derived from decellularized extracellular matrix, they are designed as temporary scaffolds that guide autologous tissue regeneration and ultimately degrade. Theoretically, this avoids a permanent foreign body reaction and may reduce long-term discomfort. Nevertheless, the clinical value of biologic meshes in inguinal hernia repair remains controversial. Some studies suggest that biologic meshes reduce chronic pain and improve quality of life; others show no difference in pain or recurrence rates compared with synthetic meshes. Meta-analyses have not demonstrated clear superiority of biologic over synthetic meshes in overall complications, recurrence, or chronic pain, and the heterogeneity among existing studies is high.

The BIOLAP randomized clinical trial, published in JAMA Surgery in 2025, provided high-level evidence for symptomatic bilateral hernias. It showed that in laparoscopic inguinal hernia repair, biologic mesh did not significantly reduce postoperative pain. Moreover, it was associated with a significantly higher 2-year recurrence rate (11.2% vs. 2.5%) and a higher seroma rate (33.4% vs. 21.6%). However, a key question remains: can these conclusions be directly extrapolated to the setting of contralateral asymptomatic hernia repair, where the therapeutic goal is to maximize long term comfort rather than to relieve existing symptoms? The investigators previously conducted an exploratory single-center randomized controlled study (n=52, BiSOH) that addressed this question preliminarily. In that trial, the biologic mesh group had significantly lower inguinal pain scores at both 1 month and 6 months, with pain decreasing over time in both groups. Quality of life measured by SF-36 was significantly better in the biologic mesh group at both follow-up time points, and the EQ-5D score was higher at 6 months. These findings suggest that biologic mesh may offer advantages in chronic pain control and quality of life for occult hernia repair, contrasting with the BIOLAP conclusions. However, the single center design and methodological limitations prevented confirmation of the primary endpoint difference, highlighting the need for a multicenter, high-quality clinical trial.

Currently, international guidelines lack high level evidence on the optimal mesh type for simultaneous repair of contralateral asymptomatic hernias. Therefore, this multicenter, randomized, single-blinded, parallel-controlled trial was designed to compare biologic versus synthetic meshes in this specific scenario. The hypothesis is that the use of a biologic mesh (porcine UBM/SIS composite) reduces chronic pain on the asymptomatic side at 6 months without increasing recurrence, compared with a synthetic mesh (self-gripping polyester).

The biologic mesh is a porcine urinary bladder matrix and small intestinal submucosa composite (UBM/SIS) manufactured by ZR Medtech (Suzhou, China). It is a non-cross-linked, acellular, collagenous matrix produced through patented decellularization and antigen removal processes. It has been used for various soft tissue defect repairs.

Inclusion Criteria:

• Age 18 to 80 years
• Unilateral symptomatic inguinal hernia with contralateral asymptomatic hernia (diagnosed either preoperatively as a clinically asymptomatic hernia or intraoperatively as an occult hernia)
• Planned for laparoscopic transabdominal preperitoneal (TAPP) repair and consent to simultaneous repair of the contralateral asymptomatic hernia
• Written informed consent obtained

Exclusion Criteria:

• Incarcerated or strangulated hernia requiring emergency surgery
• Inability to receive porcine-derived devices (religious or ethnic reasons)
• Participation in other interventional trials within the last 6 months
• Acute systemic infection or skin disease near the surgical site
• Chronic pain syndrome or long-term use of analgesic medications
• Pregnancy, planned pregnancy, or breastfeeding
• Any condition judged by the investigator as unsuitable for trial participation

Individual participant data (IPD) that underlie the results reported in the primary publication will be shared after de-identification. The study protocol, statistical analysis plan, and informed consent form will also be shared.

Data will be available beginning 6 months after publication of the primary results.

Data will be made available to researchers who provide a methodologically sound proposal, for purposes of achieving the aims in the approved proposal. Proposals should be directed to the corresponding author.

the trial as long as the symptomatic side has not developed a recurrences.