A Register-based Randomized Controlled Multicenter Trial of Laparo-endoscopic Bilateral Inguinal Hernia Repairs With an Asymptomatic Contralateral Hernia
Phase: NA
Conditions: Inguinal Hernia Bilateral
Sponsor: Karolinska Institutet

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Clinical Study Protocol 
Register Randomized Controlled Trial 
 
Laparo-endoscopic Bilateral Inguinal Hernia Repairs  
BILAP HERNIA Trial 
 
 
 
 

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TRIAL INFORMATION 
Principal investigators 
Maria Melkemichel 
MD, PhD  
Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet. Sweden 
Department of Breast, Endocrine tumors and Sarcoma, Karolinska University Hospital, Stockholm, Sweden 
Email: maria.melkemichel@ki.se 
Phone: +4670 159 7660 
 
Hanna De La Croix 
MD, PhD, Associate Professor  
Department of Surgery, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden  
Department of Surgery, Sahlgrenska University Hospital, Region Västra Götaland, Gothenburg, Sweden 
Email: hanna.nilsson@gu.se 
Phone: +4670 516 57 84 
 
Co-investigators 
Ramia Stolt, MD, Ursula Dahlstrand, MD, PhD, Henrik Holmberg, biostatician, associate professor, 
Johanna Österberg, MD, PhD, Pär Nordin, MD, Professor, Gabriel Sandblom, MD, associate 
professor 
Adjunct members: Filippa Widman, MD 
 
Trial Title  
A register-based randomized controlled multicenter trial of laparo-endoscopic bilateral inguinal hernia 
repairs with an asymptomatic contralateral hernia  

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Trial Code  
BILAP HERNIA Trial 
 
Trial Registration Number 
 
ClinicalTrials.gov Identifier: Not yet registered 
 
Site-Ivestigator’s and Trial Surgical units 
 
All surgical departments in Sweden that are participating in the Swedish Hernia Register and that will 
meet the surgical volume criteria for laparo-endoscopic groin hernia repairs will be invited to include 
patients.  
 
Trial Period 
 
Estimated start of inclusion: 2026/2027 
Estimated end of inclusion: 2030/2031 
 
Ethics 
 
Approval of the study protocol will be obtained by the Regional Ethics Review Board in Sweden prior 
to inclusion. All procedures performed in the study involving human participants will be in accordance 
with the ethical standards of the institutional and/or national research committee and with the 1964 
Helsinki declaration and its later amendments or comparable ethical standards. Participating 
investigators have the responsibility to give both an oral and a written patient information about the 
trial. Obtained signed informed consent from all patients are maintained before including them in the 
trial. 
 
 
 
 
 
 

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BACKGROUND 
 
Groin hernia repair is one of the most common surgical procedures with approximately 20 million 
repairs performed annually in the world1. In Sweden, over 16.000 groin hernia operations are 
prospectively registered annually in the Swedish Hernia Register (SHR)2. Over the past 30 years, the 
SHR has achieved a national completeness and data validation level of 98%3. By creating a database of 
over 400.000 operations, the SHR has had a large impact on improving the quality of hernia surgery in 
Sweden as well as internationally2. 
There are mainly two important outcomes following a groin hernia repair that could impair the 
patient’s quality of life; recurrence and chronic pain – both of them retained from the SHR and being 
main quality predictors for groin hernia repair in Sweden. 
The life time risk of undergoing a repair for a groin hernia has been estimated to be 27% for men and 
3% for women4. The prevalence of bilateral groin hernias among these has been reported up to 22%5, 
while the prevalence of an asymptomatic contralateral groin hernia in patients with symptomatic 
unilateral groin hernia has been estimated to around 15%6. Around 30% of all asymptomatic groin 
hernias are predicted to become symptomatic and require a future repair7.  
Chronic pain following groin hernia repair has been described to have a rate somewhere in the range of 
10-15 % after a groin hernia repair8.9. However, some studies have reported disturbing incidences up to 
30-60 %, confirming that chronic pain is an unfortunate problem that impairs patients’ quality of 
life10,11. 
The conditions of an asymptomatic groin hernia and an occult groin hernia may sometimes be 
exchangeable in the literature. However, it is important to distinguish the definitions from each other. 
The true incidence of occult hernias (defined as an asymptomatic hernia not detected by physical 
examination, but found intra-operatively) still remains uncertain and is suggested to be higher than 
originally expected12. In a recent systematic review by Dhanani et al., the incidence of an occult groin 
hernia was estimated to be 14.6% by the time of a laparoscopic repair13. Hence, the authors concluded 
that it was no indication for an immediate repair, since less than 10% of these occult hernias are likely 
to become symptomatic. On the other hand, Wu et al., suggested that simultaneous prophylactic repair 
of an asymptomatic contralateral hernia may prevent a repeat procedure in the future and without any 
significant side effects of patient recovery to daily life7. In a randomized controlled trial from 2006, 
O’Dwayer et al., demonstrated that a repair of an asymptomatic groin hernia has little effect on the rate 
of long-term chronic pain for patients14. Likewise, Park et al., have proposed that repairing an 

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asymptomatic contralateral groin hernias is associated with more benefits than risks for both the patient 
and for the society5.  
In contrast to the above-mentioned advantages of patients with bilateral groin hernias undergoing a 
simultaneous prophylactic repair of the asymptomatic contralateral groin hernia, some suggest that it is 
likely that there can be an increase in operation-time and prolonged immediate postoperative pain in 
these patients compared to those that only have their symptomatic unilateral groin hernia repaired5. 
Malouf et al., could confirm that the short-term postoperative pain was higher for bilateral repairs 
compared to unilateral repairs at 2 weeks postoperative control, but this difference resolved by 6 weeks 
after surgery15. Previous reports indicate no significant differences between unilateral hernia repairs 
compared to bilateral repairs considering length of hospital stay, postoperative complications or 
duration for returning to daily activity5,16,17.  
The European Hernia Society (EHS) guidelines recommend laparo-endoscopic repair for bilateral groin 
hernias if it is feasible and in agreement with the patients, but a routine’s exploration of the 
contralateral groin is only suggested for the TAPP approach (transabdominal preperitoneal repair) and 
not for repairs performed through TEP (total extra-preperitoneal repair)18. EHS also state that although 
most patients with asymptomatic groin hernias will develop symptoms and need a future surgery, 
watchful waiting for an asymptomatic inguinal hernia is safe since the risk of hernia complications is 
low.18 
An important withdrawal with previous studies is that it is not possible to predict whether the patients 
were operated laparoscopically because of bilateral symptoms, or if occult bilateral groin hernias were 
detected due to the laparoscopic approach. 
The incidence and treatment of an asymptomatic contralateral groin hernia in patients with bilateral 
groin hernias have therefore been debated on in the past decades. The majority of bilateral hernias are 
operated laparoscopically and we are facing an increasing trend. Despite the high prevalence of bilateral 
groin hernias and asymptomatic contralateral groin hernias, there is currently no proper consensus on 
the timing of repair of the asymptomatic contralateral groin hernia.  
Therefore, we aim with this large multicenter register- randomized controlled trial via a national highly 
validated Swedish register to investigate the outcomes of asymptomatic contralateral groin hernias in 
patients with bilateral groin hernias.  
 
 

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AIM and HYPOTHESIS 
 
The aim is to investigate the differences in the outcome of chronic pain, reoperation, peri - and 
postoperative complications and patient satisfaction between laparo-endoscopic bilateral inguinal hernia 
repair with an asymptomatic contralateral groin hernia versus a laparo-endoscopic unilateral inguinal 
hernia repair without repairing the asymptomatic contralateral groin hernia in bilateral inguinal hernias 
in adults. Additionally, we aim to study the prevalence of future elective and emergency hernia repair of 
the unrepaired asymptomatic contralateral inguinal hernia.  
 
The chronic pain, reoperation, peri - and postoperative complications and patient satisfaction is 
hypothesized to be equal between bilateral inguinal hernia repairs with an asymptomatic contralateral 
inguinal hernia compared to unilateral symptomatic inguinal hernia repairs.  
 
 
STUDY OBJECTIVES 
 
The exposure  
Method of repair, containing two groups of allocation repairs;  
 
Bilateral repair (exposure – intervention arm) 
Unilateral repair (unexposure – standard arm) 
 
Primary outcome 
PROM - Patient-reported chronic pain postoperatively [Time Frame: 1 year after surgery] 
 
To compare chronic pain 1 year after surgery between laparo-endoscopic bilateral inguinal hernia repair 
with an asymptomatic contralateral inguinal hernia (bilateral arm) versus a laparoscopic unilateral 
inguinal hernia repair (unilateral arm) without repairing the asymptomatic contralateral inguinal hernia 
in bilateral groin hernias in adults.   
 
Secondary outcomes  
To compare the two arms with regard to; 
• Risk of reoperation of the hernia repair [Time Frame: within 2, 5 and 10 years] 
• Perioperative complications (safety) [Time Frame: Intraoperatively] 

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• Postoperative complications (safety) [Time Frame: 30 days after surgery] 
• Rate of future elective hernia repair of the unrepaired asymptomatic contralateral 
inguinal hernia [Time Frame: within 1, 2, 5 and 10 years] 
• Rate of future emergency hernia repair of the unrepaired asymptomatic contralateral 
inguinal hernia [Time Frame: within 2 years] 
• Comparting all women in the study population to the men according to above 
outcomes [Time Frame: different for outcomes] 
• Rate and characteristics of found femoral hernias in the total study population 
[Time Frame: Intraoperatively] 
• Time of surgery [Time Frame: Intraoperatively] 
• PROM - Patient satisfaction [Time Frame: 1 after surgery] 
 
METHOD 
 
Trial design  
The study is a register-based randomized controlled multicenter trial with patients that have bilateral 
inguinal hernias whereas one of the hernias (called the contralateral groin hernia) is asymptomatic. 
Patients are either randomized to a repair undergoing laparo-endoscopic bilateral inguinal hernia repair 
of both hernias or only a laparo-endoscopic unilateral inguinal hernia repair of the symptomatic 
inguinal hernia (Figure 1). The name of the trial is; the BILAP HERNIA Trial. Inclusion, 
randomization and follow-up will be conducted through a national register; the Swedish Hernia 
Register (SHR). At each participating unit, all patients who fulfill the inclusion criteria and none of the 
exclusion criteria will be invited in the study. After oral and written consent (see attachment A), the 
patients will be included in study. They will be given a question about pain to answer (Figure 2) before 
surgery and this will be recorded in their baseline characteristics. Patients are then randomized intra-
operatively through the SHR to one of the allocation arms. During operation all patient and hernia 
characteristics are filled in prospectively by the operation-team in SHR according to the SHR register 
(see attachment B), forming the patients CRF (Clinical Research Form). 1 year after surgery, all 
participants will be sent out a PROM questionnaire according to the incorporated routine in the SHR 
(see attachment C) including questions addressing chronic pain and patient satisfaction.  
 

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Figure 1. Schematic illustration of the randomization and allocation arms 
 
Estimate the pain you experienced from your groin hernia prior to surgery.   
1.No pain 
2.Pain that could easily be ignored 
3.Pain that could not be ignored but did not influence daily activities 
4.Pain that could not be ignored, which affected concentration and performance of daily activities 
5. Pain that inhibited most daily activities 
6. Pain that required rest or bed rest 
7. Pain so severe that you were forced to seek medical attention 
Figure 2. PROM addressing pain before surgery 
 
The Swedish Hernia Register  
The Swedish Hernia Register (SHR) has near national coverage of surgical units across Sweden. More 
than 98% of all groin hernia operations from 90 surgical units performed in Sweden are registered in the 
SHR. It is a nationwide database of more than currently 400,000 groin hernia procedures2. Procedures 
are recorded prospectively by the surgeon during the operation and patients are identified using a personal 
identity-number, unique for each citizen in Sweden. The SHR is linked to the Swedish population registry 
to obtain accurate follow-ups. 10% of the aligned surgical units are checked independently each year. 
Validity of the SHR has been reported to be 98 % correct variables and a 97 % cover rate for procedures 
in the participating units, demonstrating that the SHR is a highly validated register3. 

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PROM questionnaire  
 
Between 2012 and 2018 a questionnaire assessing patient-reported outcome measures (PROMs) was 
sent out 1 year after surgery to all patients that had undergone a groin hernia repair from units 
participating in the SHR. The previous response rates have approximately been up to 72%. The 
distributed questions are extracted from the Inguinal Pain Questionnaire (IPQ)19 and is a short-form 
questionnaire. A short-form questionnaire has shown to be exchangeable to the longer original version 
of IPQ20. This provides the unique opportunity to determine prospective collected patient-reported 
pain outcomes through a register. Studies reflecting the results of surgeons not specialized in hernia 
surgery are lacking today on assessing pain patients between different method of repairs, and especially 
on a large number of unselected hernias. This routine, by sending out PROM 1 year to all patients that 
has been undergone a groin hernia repair has now in 2025 again been incorporated in the SHR and will 
continue forward to be. The PROM questionnaire consists today of more questions (see attachment C).  
The population-based SHR offers a unique possibility to study this through a randomized controlled 
trial and send out the questionnaire again within a trial. Patients are followed from operation to re-
operation, death or migration. Due to the personal identity-number, unique for each citizen in Sweden, 
patients can be followed until a reoperation for recurrence or pain and if a future elective or emergency 
repair has been done and registered within the framework of the SHR.  
 
Definition of a symptomatic and asymptomatic inguinal hernia  
A symptomatic inguinal hernia is defined as a clinical detectable reducible bulge (very small or large) in 
the groin above the inguinal ligament with symptoms of bulging, pain and discomfort.  
 
An asymptomatic inguinal hernia is defined as a clinical detectable reducible bulge (very small or large) 
in the groin above the inguinal ligament where the patient has no symptoms of bulging, pain or 
discomfort. In some cases, the patients have not even noticed their asymptomatic hernia.  
 
If preoperative imaging detects an inguinal hernia but the patient does not exhibit a clinically 
identifiable hernia during examination, this situation is not classified as an asymptomatic hernia. 
Preoperative imaging is not always reliable for diagnosing hernias, and clinical examination remains a 
critical component in assessment. 
 
Selection of the study population 
All adult patients referred for a groin hernia to outpatient clinical are eligible to the study and screened 
for inclusion. An unaware asymptomatic contralateral groin hernia might be present in the outpatient 

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clinic after examination by the surgeon. Patients randomized to only a unilateral hernia repair will be 
followed-up through the register to investigate both the risk of emergency hernia repair and the risk of 
a future elective repair of the asymptomatic not repaired hernia.  
 
Inclusion criteria 
• Elective laparo-endoscopic surgery of bilateral primary inguinal hernia in both men and women above 
and 18 years old, whereas one of the hernias is asymptomatic in a surgical center that perform > 50 
laparo-endoscopic groin hernia repairs per year22. 
 
Exclusion criteria 
• Recurrent groin hernias (earlier repair in the groin) 
• Femoral hernias (both symptomatic and asymptomatic) 
• Combined femoral groin hernias   
• Detected femoral hernia during surgery (they will be recommended to be operated with a bilateral 
repair) 
• Another operative procedure at the same time 
• A history of open lower abdominal surgery (except appendectomy) like prostate surgery 
• ASA fitness grade > 3 
• Patients that cannot undergo general anesthesia  
• Pregnancy 
• Age < 18 years 
• Infected wounds 
• Emergency operation (incarcerated hernia) 
• Inability to fill in questionnaires due to language barriers or condition as Alzheimer’s  
 
Femoral hernias 
According to current guidelines, patients with femoral hernias (groin hernias below the inguinal 
ligament) are recommended for surgery whether they are symptomatic or asymptomatic18. This is due 
to literature reporting an increased rate of emergency repairs for femoral hernias. Femoral hernias are 
more common in women compared to men, whereas the most common groin hernias are still indirect 
inguinal hernias in both genders. It is not always easy to distinguish between a femoral and an inguinal 
hernia prior to surgery.  
 

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Patients with a known symptomatic or an asymptomatic femoral hernia prior surgery is an exclusion 
criterion in this trial. If a femoral hernia is found intra-operatively, the patient should be excluded, and 
it is recommended to repair the asymptomatic contralateral groin hernia, as there is an increased risk 
that this hernia is also femoral.  
 
Preoperative and Perioperative process 
Participants will be given a question to answer addressing the grade of pain in the groin hernia prior to 
surgery (Figure 2) before surgery and this will be recorded in their baseline characteristics. Participants 
are then randomized intra-operatively through the SHR to one of the allocation arms (see below). 
During operation all patient and hernia characteristics are filled in prospectively by the operation-team 
in SHR according to the SHR register (see attachment B), forming the patients CRF (Clinical Research 
Form). 
 
Randomization process 
Patients will be recruited to participate in the study during the clinical outpatient meeting with the 
surgeon if there is an indication for surgery. At each participating unit, all patients who fulfill the 
inclusion criteria and none of the exclusion criteria are invited in the study. After oral and written 
consent, the patients are included in the study. The randomization will take place intraoperatively after 
identifying the type of hernia at the symptomatic side. If no femoral hernia is found – randomization 
will take place. The patient is allocated to one of the arms. Each hospital will receive the same 
relationship (1:1, block randomization) between bilateral repair and unilateral repair.  
 
Sample size estimation 
The chronic pain rate 1 year after surgery in previous hand-full studies are ranging from 10-15% and up 
to 18% for women following groin hernia repair. We hypothesize that there is no significant difference 
in chronic pain rate 1 year after surgery between bilateral repair and unilateral repair as a non-inferiority 
trial. We assume a 12% chronic pain rate in both groups. If there is truly no difference between the 
standard and the intervention group for the binary primary outcome, then 2074 patients are required to 
be 80% sure that the upper limit of a one-sided 97.5% confidence interval (CI) (or equivalently a 95% 
two-sided CI) will exclude a difference in favor of the standard group of more than 4% (non-inferiority 
margin). In any case, the number of patients in each group must be increased by 10% to cover the 
expected patient drop off of the primary outcome of patient-reported chronic pain (this number has 
been decreased from earlier cohort studies of 30% to 10% due to that this trial will have reminders to 
the patients of the PROM questionnaire and an assumption of being included in a trial can increase the 
response rate). The estimated total amount of patients would be 2200.  Approximately 16,000 groin 

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hernia repairs are performed annually in Sweden and approximately 3700 endo-laparoscopic repairs (25 
surgical units of total 85) are being performed annually in surgical units that perform > 50 endo-
laparoscopic groin hernia repairs per year (medium to high volume centra)22.  The prevalence of an 
asymptomatic contralateral groin hernia in patients with symptomatic unilateral groin hernia has been 
estimated to be around 15%. This gives the trial approximately 555 patients to include annually and 
with some not meeting the inclusion criteria, we estimate an inclusion of approximately 450 patients 
annually. To include 2200 patients, the estimated inclusion period will be 4,8 years.  
 
Multicenter trial 
The study is a multicenter trial including several surgical units that can represents different regions in 
the Swedish nation. For authorship a substantive contribution to the work according to the ICMJE 
recommendations will be required. A minimum of 50 laparoscopic groin hernia repairs annually are 
required by the participating surgical unit to be included as a surgical unit in the trial.   
 
Surgical technique – Laparo-endoscopic inguinal hernia repair  
Both transabdominal preperitoneal (TAPP) and total extraperitoneal (TEP) repair are minimally 
invasive mesh techniques considered in this study. The surgeon can select the method they are most 
skilled in, but to qualify for participation, the surgical unit must perform a minimum of 50 procedures 
annually using either technique. In both approaches, it is essential to place a large-pore flat or 
preformed mesh (≥ 15x10 cm) in the preperitoneal space to cover all potential hernia orifices in the 
groin. No specific mesh or fixation method is mandated, though current evidence recommends 
atraumatic fixation (for example resorbable sutures or tackers or glue) when using lightweight mesh, 
particularly in bilateral hernias or large defects (>3 cm). 
 
Both procedures require general anesthesia, with the patient positioned supine and legs elevated. Local 
anesthesia is applied prior to trocar insertion. The techniques differ primarily in how they access the 
preperitoneal space, but standardized dissection and meticulous parietalization are consistent in both. 
All connective tissue is dissected to expose Retzius and Bogros spaces while reducing direct, indirect, or 
femoral hernia content. For hernias, the sac is dissected from the transversalis fascia in Hesselbach’s 
triangle for direct hernias or from the spermatic cord for indirect hernias, ensuring not to injure the 
genital branch of the genitofemoral nerve. Any lipomas in the cord or round ligament should be 
excised, and irreducible femoral hernias may require incision of the lacunar ligament. The peritoneum is 
reflected to expose the "inverted Y" structure of the inferior epigastric vessels and the vas deferens (or 
round ligament in females). An adequate space for the mesh is created by cutting the arcuate ligament 
laterally.  

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TAPP Procedure   
 
TAPP accesses the abdominal cavity to place the mesh between the peritoneum and posterior 
abdominal wall via a peritoneal incision. Three trocars are insized in a supraumbilical position, spaced 
6–8 cm apart. A 5 or 10 mm 30° laparoscopic camera is used, and pneumoperitoneum (10-15 mmHg) 
is established through open laparoscopy or CO2 insufflation via a Veress needle. A large peritoneal flap 
is prepared through an arcuate incision, facilitating adequate exposure of the myopectineal orifice for 
correct mesh positioning. The peritoneum is closed over the mesh using barbed sutures or glue, but not 
tackers of any kind. Pressure may be lowered before closure. 
 
TEP Procedure   
TEP is performed without entering the abdominal cavity, placing the mesh directly into the 
preperitoneal space. A subumbilical incision is made to access the anterior rectus sheath, which is then 
incised, allowing lateral retraction of the muscle to reveal the posterior sheath. A 10 mm 30° 
laparoscopic camera is introduced via a trocar to create the preperitoneal space using telescopic blunt 
dissection. Two additional 5 mm trocars are placed in the lower midline, ensuring adequate spacing. 
Fatty tissue in the preperitoneal space should remain in contact with the inguinal floor. The pubic 
symphysis is identified, and Cooper’s ligament is bluntly dissected which will opens both the space of 
Retzius and the space of Bogros, allowing for mesh placement without covering the bladder. The 
peritoneum is mobilized to expose the triangle of doom adequately. A mesh large enough is placed to 
cover the inguinal and femoral areas. 
Bilateral Repairs and Randomization 
 
The randomization takes place intraoperatively after identifying the type of hernia at the symptomatic 
side. If no femoral hernia is found – randomization will take place. In randomized bilateral repairs 
(intervention group), the surgeon alternates sides after addressing the symptomatic side, standing on 
the opposite side of the hernia in both TAPP and TEP procedures. Dissection must be completed on 
both sides before inserting the mesh, with two overlapping meshes used for bilateral hernias. No trocar 
position changes are required, although additional trocars may be added in TAPP if necessary. The 
control group, receiving unilateral repairs, cannot undergo surgery on the contralateral side for occult 
hernias.  
 
 

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Postoperative outcomes and follow-up 
The postoperative regime will be similar in the two allocation arms of repairs. Participants can be 
operated either as outpatients or inpatients due to the patients' comorbidity.  
 
Participants will be followed-up within the regime of the Swedish Hernia Register (SHR). None of the 
participants will be routinely seen in the outpatient clinic for a clinical examination.  
 
Chronic pain 
At 1 year after surgery each participant, for each inguinal hernia repair (each groin), will be requested to 
fill in a PROM questionnaire within the framework of the SHR.  
 
The question put to the participant that will address chronic pain will be item 2, extracted from the 
IPQ (Figure 2). The questionnaire will be sent out 1 year after the hernia repair to all participants in the 
trial via the SHR. Non-responders will have a reminder sent out again within 30 days. In the analysis, 
level 1-3 will be defined as no pain and level 4-7 as persistent significant chronic pain.  
Estimate the worst pain you felt in the operated groin during this past week.  
1.No pain 
2.Pain that could easily be ignored 
3.Pain that could not be ignored but did not influence daily activities 
4.Pain that could not be ignored, which affected concentration and performance of daily activities 
5. Pain that inhibited most daily activities 
6. Pain that required rest or bed rest 
7. Pain so severe that you were forced to seek medical attention 
Figure 2. PROM question addressing chronic pain 1 year after surgery, question number 2 from the IPQ.  
 
Reoperation 
Reoperation within the framework of SHR can either be for recurrence or for pain.  
The follow-up time for reoperation for recurrence will be within 2, 5 and 10 years after surgery. 
Reoperation for recurrence will be defined as a new hernia repair due to recurrence or pain in the same 
groin where the previous index inguinal hernia repair had been performed and had been registered in 

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SHR. The time from the index repair to the reoperation will be calculated in days and described in 
median.  
 
Perioperative and Postoperative complications 
Different perioperative complications within the framework of the SHR will be investigated. 
Postoperative complications will be assessed 30 days after surgery and classified according to the 
Clavien-Dindo classification within the framework of the SHR 30 after surgery will be investigated to 
see differences between the groups (see attachment B).  
 
Patient satisfaction 
A question in the PROM questionnaire will assess patient’s satisfaction with their groin hernia 
operation results. Selectable answers will be: 1) Yes, perfectible satisfied, 2) Yes, almost satisfied, 3) No, 
mainly not satisfied, 4) No, not at all satisfied. Patient dissatisfaction will be defined as a score > 2.  
 
Emergency hernia repair  
Emergency hernia repair within 2 years of the unrepaired asymptomatic contralateral inguinal hernia 
will be investigated via the SHR.    
 
A future elective hernia repair  
A future elective hernia repair of the asymptomatic contralateral inguinal hernia within 1, 2, 5 and 10 
years will be investigated via the SHR. 
 
Unrepaired asymptomatic inguinal hernia 
The unilateral inguinal hernia repair participants will be registered in the SHR for their unilateral repair 
within the trial. They will be followed until reoperation of their previous symptomatic inguinal hernia 
or until a future elective or emergency repair of the asymptomatic hernia has been performed or until 
death. This is due to the unique personal number for each citizen in Sweden.     
   
 
Trial subgroups  
The trial will have one large main study population including all inguinal groin hernias in both men and 
women to be primary analyzed. 
 
The trial will provide important clinical subgroups for analysis; 

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• All women with inguinal hernias – comparing the outcomes of chronic pain, 
reoperation, peri - and postoperative complications and patient satisfaction to all men 
• All women with inguinal hernias - investigating the prevalence and the risk of future 
elective and emergency repair of the asymptomatic contralateral inguinal hernia 
compared to the men 
• Rate and characteristics of found femoral hernias in the whole study population    
 
 
Monitoring 
The investigators at each unit are responsible to record and register patient’s variables in the SHR. A 
special demonstration of the SHR within the Trial will be given to each unit and the involved surgeons 
by the principal investigator.   
 
Statistical analysis 
The statistical analysis and presentation of the data will be described in detail using program R in 
collaboration with statistical expertise. A statistical analysis plan (SAP) has been conducted. (see 
attachment D).  
 
Study period 
The study will start including trial participants year 2026/2027. Randomization of trial participants are 
estimated to be done within 5 years, 2030/20231. The follow-up of the primary outcome will be 1 year 
after surgery. The total follow-up of secondary outcomes will be 10 years after surgery.  
 
ETHICAL CONSIDERATIONS  
Guidelines for the recommended method of repair for patients with bilateral inguinal hernias with an 
asymptomatic contralateral inguinal hernia is still lacking today. Consequently, surgeons lack standard 
protocols in the clinical setting for these patients. The standard treatment is today a laparoscopic 
unilateral inguinal hernia repair with an unrepaired asymptomatic contralateral inguinal hernia. This is 
due to fear of the risk of chronic pain after surgery. However, in more high-volume laparoscopic 
surgical volume units both scenarios of bilateral and unilateral repair scan be accepted as standard 
treatments, however, with no scientific evidence. Watchful waiting of an asymptomatic inguinal hernia 
in men is considered accepted and safe and also recommended by the international guidelines if it align 
with the patient.  

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Conversely, one ethical withdrawal with this trial can be the treatment of women with bilateral inguinal 
hernias. According to current guidelines, women with a groin hernia are recommended for surgery 
whether they are symptomatic or asymptomatic or femoral or inguinal. This is due to literature 
reporting an increased rate of emergency repairs in women and for femoral hernias. Femoral hernias 
are more common in women compared to in men and are not always easy to distinguish from inguinal 
within the clinical examination. On the contrary, women report higher chronic pain rate after groin 
hernia surgery than men, up to 18%21. A chronic pain that is significant and influence daily life 
activities. Consequently, surgery on asymptomatic groin hernias in women can be debated due to the 
significant increased risk of chronic pain after surgery.  
The trials study design is conducted in such way that an asymptomatic contralateral inguinal hernia 
(femoral hernias will be excluded and repaired) will be left out and unrepaired for watchful waiting in 
some women. In contrast, the trial will have a unique possibility to study watchful waiting and the risk 
of future elective and emergency repair in women with asymptomatic inguinal hernias within a 
randomized study population, which have never before been done.  
 
PATIENT BENEFITS 
One of the main aims of the establishment of The Swedish Hernia Register (SHR), was to study 
recurrence rates nationally and improve outcomes. Today, it is proven that both quality and cost-
effectiveness of groin hernia repair have been improved in Sweden with a register participation. 
Guidelines for the recommended method of repair for patients with bilateral inguinal hernias with an 
asymptomatic contralateral inguinal hernia is still lacking today. Guidelines have stressed the need for 
reliable high-quality data from randomized trials to improve treatment recommendations for patients 
with contralateral asymptomatic hernias in bilateral inguinal hernias.  
If the results of the trial will be in align with the hypothesis, all bilateral inguinal hernias with an 
asymptomatic contralateral hernia should undergo a simultaneous bilateral repair. An improvement of 
this approach may contribute a lot to the operated patients. This may mean that fewer patients will 
need to have a future elective inguinal hernia repair. It can also mean that the risk of having an 
emergency repair may be decreased. It also reduces patient anxiety of the asymptomatic inguinal hernia 
becoming symptomatic and emergency. A potential health-economic cost effectiveness is possibly, 
whereas patients only need one operation instead of two separates.  

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We can expect that the results from this register-based randomized controlled study will have a direct 
implication on the recommendations for hernia repair standards in patients with bilateral inguinal 
hernias and may contribute to set up more standard protocols in the clinical setting.  
 
DATA-PROTOCOL PROTECTION  
The investigators at each unit are responsible and will ensure the confidentiality of the clinical study 
protocol and data of the study. Each unit/surgeon will have a personal login and password to the SHR 
for registration. Only the principal investigators will have access to all registered information in SHR 
for the study population. Unidentified data will then be used in the final statistical analysis.  
 
Revision Protocol History after Ethical approval   
 
 
 
 
 
 
 
 
 
 
 
 
 

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