The technical distinction at the heart of the study is more consequential than it might first appear. In minimally invasive ventral hernia repair, the mesh can be placed in several anatomical planes: intraperitoneal, where the prosthesis lies directly against the bowel within the peritoneal cavity; preperitoneal, tucked between the peritoneum and the abdominal wall; retro-muscular, positioned behind the rectus muscles; or onlay, placed superficial to the fascia. Techniques that keep the mesh outside the peritoneal cavity have been gaining popularity, largely because intraperitoneal placement carries well-documented short-term drawbacks, including increased postoperative pain driven by fixation tackers and early recurrences linked to mesh migration. Still, the most appropriate mesh position remains genuinely controversial, and the long-term consequences of each choice have never been rigorously compared.

The concern driving ORION is adhesion formation. When mesh sits intraperitoneally, it is in permanent contact with viscera, and animal studies have shown that even composite meshes designed to resist adhesion provoke fibrous bands in that space. Imaging studies and surgical revisions in these patients frequently reveal adhesions between bowel and mesh, and the clinical consequences can be serious: bowel entrapment, chronic pain, obstruction, and, most acutely, visceral injury during later operations. Surgeons performing adhesiolysis—the careful division of scar tissue—in a patient with prior intraperitoneal mesh face a landscape where loops of intestine may be densely fused to the prosthesis itself. Most existing research has focused on hernia-related outcomes such as recurrence and infection, potentially underreporting the downstream morbidity that adhesions generate over years.

The ORION investigators, a collaborative group led by researchers at the University of Milan and IRCCS Istituto Auxologico Italiano and endorsed by the European Hernia Society, have formulated a clear primary hypothesis: that prior intraperitoneal mesh placement is associated with a higher risk of intraoperative visceral injury during adhesiolysis at subsequent minimally invasive abdominal surgery than prior extraperitoneal placement. Their secondary hypotheses extend the comparison further, predicting that intraperitoneal placement brings a greater burden of adhesion-related complications, longer adhesiolysis time, higher conversion rates from minimally invasive to open surgery, and—among patients reoperated for recurrence—higher rates of chronic post-surgical pain and neuropathic features at ninety days.

The study design is deliberately pragmatic. ORION is a prospective, multicentre, observational study recruiting surgical centres across Europe, with data collection running from 1 March 2026 to 28 February 2027. Any European hospital performing elective or emergency minimally invasive abdominal surgery can participate, and there is no minimum patient quota per centre. Eligible patients are adults who previously underwent minimally invasive mesh-based ventral hernia repair—whether primary, recurrent, or incisional—with either intraperitoneal or extraperitoneal mesh, and who now require further minimally invasive abdominal surgery for any reason, from cholecystectomy to colorectal resection to gynecologic procedures. This broad capture is intentional: it reflects the real-world risk of adhesiolysis-related visceral injury across the full spectrum of abdominal operations, not just hernia redo surgery.

Participants are divided into two pre-specified cohorts. Cohort A comprises patients undergoing minimally invasive surgery for indications other than recurrent hernia repair, and these patients are assessed only up to discharge, with in-hospital outcomes recorded. Cohort B comprises patients undergoing minimally invasive repair of a recurrent ventral or incisional hernia, and this group receives scheduled follow-up at thirty and ninety days. The investigators restricted post-discharge follow-up to the recurrence cohort to prevent indication-driven heterogeneity in outcome ascertainment, a design choice that preserves internal validity for early morbidity analyses while maintaining external validity for the primary intraoperative endpoint, which is captured across all procedures performed after prior mesh placement.

The primary outcome is precisely defined: adhesiolysis-related visceral injury, meaning intraoperative damage to bowel, bladder, or solid organs during the division of adhesions. Injuries are categorized as serosal tears, full-thickness bowel injuries such as enterotomy or perforation, or other visceral injuries involving organs like the bladder, spleen, liver, or stomach. Notably, omental injury or division is considered inherent to adhesiolysis and is recorded separately rather than counted as a primary event. Secondary outcomes include the incidence of adhesion-related complications such as bowel obstruction, the duration of adhesiolysis in minutes, the rate and reasons for conversion to open surgery, and a detailed characterization of adhesions using the Peritoneal Adhesion Index, with the abdomen mapped into five regions and adhesion tenacity graded as flimsy, moderate, or dense.

For the recurrence cohort, the study digs into questions that have rarely been examined with such granularity. Investigators will document the anatomical or technical mechanism behind each hernia recurrence—central mesh failure, marginal recurrence, or mesh migration—and record how the recurrence was managed, including whether the same mesh type was reused, which anatomical plane was chosen, and which fixation methods were employed. Quality of life will be measured with the EuraHS-QoL scale at thirty and ninety days. Most distinctively, ORION incorporates validated neurological outcome measures: chronic post-surgical pain is defined as an increase of at least three points on the Visual Analogue Scale in the surgical area compared with the pre-operative baseline, new since surgery and unexplained by complications such as recurrence, infection, or obstruction. Suspected neuropathic features will be screened with the DN4 questionnaire, sensory changes around port sites will be recorded, and opioid use at day thirty will be tracked.

The statistical framework is built to detect clinically meaningful differences. A sample of 345 patients per group, 690 in total, provides ninety percent power to detect a ten percent absolute difference in adhesiolysis-related visceral injury rates, assuming an event rate of twenty-five percent in patients with prior intraperitoneal mesh and fifteen percent in those with prior extraperitoneal mesh. Relative risks will be calculated with log-binomial regression, adjusting for clinical and sociodemographic variables that differ between groups, while logistic regression models will assess associations between mesh position and chronic pain or opioid use. The investigators acknowledge the assumptions are pragmatic, drawn from available reoperation data after laparoscopic ventral hernia repair, because robust comparative estimates remain scarce.

The team is candid about the limitations inherent in an observational, non-randomized design. Because patients are identified at a subsequent operation rather than at the index repair, the study has no denominator of all originally treated patients and cannot estimate absolute risks per index procedure; the reported relative risks are conditional on reoperation and may be affected by selection bias, making the findings hypothesis-generating rather than definitive. Extraperitoneal repair is also a more recent technique, so intraperitoneal cases will tend to involve a longer interval since the original operation, and time and surgical era will be treated as covariates. Unblinded intraoperative assessment may introduce detection bias, and a twelve-month recruitment window cannot capture late complications such as adhesion-related bowel obstruction that may emerge years later. Even so, if ORION confirms that mesh position shapes the hazards of future surgery, its findings could reshape how surgeons weigh the long-term costs of intraperitoneal repair, inform the selection of mesh type and fixation strategy, and give renewed attention to the under-recognized neurological sequelae of abdominal wall reconstruction.

Subject of Research: Prospective multicentre observational study comparing long-term outcomes of intraperitoneal versus extraperitoneal mesh placement in ventral hernia repair

Article Title: The ORION study protocol: impact of prior intraperitoneal versus extraperitoneal mesh placement on subsequent minimally invasive abdominal reoperations

Article References: Pelfini, E., Lauricella, S., Nisi, A., Dionigi, G., & Brucchi, F. (2026). The ORION study protocol: impact of prior intraperitoneal versus extraperitoneal mesh placement on subsequent minimally invasive abdominal reoperations. Journal of Abdominal Wall Surgery, 5, Article 17325. https://doi.org/10.3389/jaws.2026.17325

Image Credits: AI Generated

DOI: 10.3389/jaws.2026.17325

Keywords: ventral hernia repair, mesh placement, intraperitoneal mesh, extraperitoneal mesh, adhesions, adhesiolysis, visceral injury, minimally invasive surgery, hernia recurrence, chronic post-surgical pain, European Hernia Society, observational study

Abdominal cocoon syndrome is a condition in which a fibrocollagenous membrane gradually encases loops of the small bowel, constricting them into a clustered mass that behaves like a mechanical bottleneck for digestion. The result is recurrent or complete small bowel obstruction, one of the most common surgical emergencies encountered worldwide. Obstruction of the small intestine is usually caused by postoperative adhesions, hernias, malignancy, or inflammatory bowel disease, but cocoon syndrome stands apart because it can strike patients who have never had abdominal surgery, a detail that makes clinicians far less likely to suspect it. The syndrome was first described in the medical literature in 1978, and its etiology remains poorly understood, though an inflammatory cascade is thought to stimulate fibroblast proliferation and collagen deposition, eventually producing the dense encapsulating layer that gives the disease its name.

The Tunisian patient’s history was notable precisely for its emptiness. He denied any prior abdominal surgery, peritoneal dialysis, abdominal trauma, appendicitis, gastrointestinal perforation, foreign-body ingestion, peptic ulcer disease, or inflammatory bowel disease. He took no chronic medications, including corticosteroids, nonsteroidal anti-inflammatory drugs, or opioids, and had no diabetes, hypertension, or autoimmune disorders. His family history was unremarkable for gastrointestinal disease or tuberculosis. On admission he appeared mildly dehydrated, with a distended, tympanic abdomen and diffuse tenderness but no signs of peritonitis. Laboratory tests showed mild leukocytosis of 13,000 cells per cubic millimeter, with otherwise normal electrolytes and inflammatory markers. Abdominal radiography revealed multiple air-fluid levels consistent with partial small bowel obstruction, prompting further imaging.

Contrast-enhanced computed tomography proved decisive. The scan demonstrated hydro-aeric distension of intestinal loops up to 57 millimeters in diameter, with progressive tapering in the right iliac fossa and moderate free fluid in the pelvis and left paracolic gutter. The characteristic finding, described in the literature as the cauliflower or cocoon sign, is a cluster of small bowel loops surrounded by a fibrotic sac, and the authors note that contrast-enhanced CT is considered the imaging modality of choice because of its ability to demonstrate this pattern. Even so, the diagnosis can remain elusive. Many cases in the published literature, including several in the review accompanying this report, were confirmed only during surgery, because the radiologic features are nonspecific and the syndrome itself is so rare that few radiologists or surgeons encounter it more than once in a career.

The patient was initially managed conservatively with nasogastric decompression, fluid resuscitation, and correction of electrolyte imbalance, a standard first-line approach for partial bowel obstruction. But his obstructive symptoms persisted after 48 hours, and the surgical team decided that exploratory laparotomy was indicated. Inside the abdomen, they found the small intestine encased within a dense, whitish fibrous membrane forming a cocoon-like sac. There was no mesenteric lymphadenopathy, no caseous nodules, and no purulent fluid, findings that helped argue against an infectious cause. The surgeons performed careful adhesiolysis, the deliberate freeing of adhesions, and total excision of the fibrotic capsule without bowel resection, because all loops were viable and regained peristalsis after release. Peritoneal fluid and membrane biopsies were sent for microbiological and histopathological evaluation, including acid-fast bacillus staining, culture, and adenosine deaminase assay, all of which came back negative for tuberculosis.

That tuberculosis work-up was not a formality. Secondary forms of abdominal cocoon syndrome are associated with peritoneal dialysis, tuberculosis, autoimmune diseases, and chronic infections, and the authors emphasize that clinicians evaluating recurrent small bowel obstruction should actively exclude tuberculous peritonitis, which can closely mimic the idiopathic form. They recommend a detailed tuberculosis history, chest imaging, and, when suspicion exists, targeted investigations such as ascitic or peritoneal fluid acid-fast bacillus smear, adenosine deaminase assay, culture, and molecular testing with CB-NAAT or GeneXpert. During surgery, representative peritoneal biopsy and fluid sampling for histopathology and microbiology are strongly recommended, because macroscopic appearance alone may not reliably exclude tuberculosis. In this case, histopathologic examination confirmed fibrocollagenous tissue without granulomatous inflammation, supporting an idiopathic diagnosis.

The postoperative course was swift. The patient was monitored for the return of bowel function, abdominal distension, and signs of infection, and oral intake resumed on postoperative day two after the passage of flatus. He received prophylactic antibiotics, ceftriaxone combined with metronidazole for 48 hours, along with analgesia, and was discharged on postoperative day four with normal bowel transit. At follow-up visits at two and six weeks he remained asymptomatic, and he expressed satisfaction with the outcome while providing written consent for publication of his clinical details and images. The authors report that early operative management of this syndrome generally results in excellent postoperative recovery and minimal recurrence, and their patient’s trajectory illustrates that point in practice.

To place the case in context, the team reviewed English-language literature on abdominal cocoon syndrome published between January 2015 and June 2024, searching PubMed and Google Scholar and including only single case reports and small case series with sufficient clinical detail. The synthesis, spanning cases from Pakistan, the United Kingdom, China, Greece, Egypt, Saudi Arabia, Iraq, Turkey, Kuwait, Morocco, India, Thailand, and Ethiopia, highlights that the syndrome predominantly affects young to middle-aged males from tropical and subtropical regions. Yet the collected cases also show the disease’s range of severity: some patients presented with straightforward obstruction, while others arrived with bowel perforation, internal fistulas, ischemic segments, or extensive small bowel necrosis. In a Thai series of three patients, one died, underscoring that delays in diagnosis can carry fatal consequences. Notably, the review also documents that idiopathic forms in middle-aged and older adults, like the Tunisian patient, are increasingly reported, even though the classic textbook portrait involves younger men.

Treatment remains an area of active debate. In early stages or in cases with intermittent symptoms, conservative management with bowel rest, hydration, nutritional support, and nasogastric decompression may be attempted. But when obstruction is complete or conservative measures fail, surgery is mandated, and the definitive procedure involves adhesiolysis and careful removal of the fibrous membrane encasing the intestine. There is growing interest in laparoscopic approaches, which offer reduced postoperative pain, faster recovery, and shorter hospital stays, and one case in the review achieved an excellent outcome with laparoscopic adhesiolysis. However, minimally invasive management is technically challenging because of dense adhesions and the risk of bowel injury, so case selection is crucial and conversion to open surgery may be required if safe dissection cannot be ensured. In the present case, the authors considered laparoscopy but deferred it because marked intestinal distension and dense adhesions on imaging made open laparotomy the safer approach. In patients with advanced liver cirrhosis or other comorbid conditions, perioperative morbidity is significantly heightened and approaches must be tailored accordingly.

The authors acknowledge the limits of the evidence base. No definitive pathophysiologic mechanism or molecular biomarker exists to distinguish idiopathic from secondary forms before surgery, CT sensitivity for early or partial disease is limited, and because the condition is so rare, treatment algorithms are largely derived from isolated case reports rather than comparative studies. Recurrence is exceptional but may occur when fibrotic tissue excision is incomplete or persistent inflammation promotes re-encapsulation, so the team advises structured follow-up with clinical evaluation at three and twelve months and abdominal imaging if symptoms return. Medical therapies aimed at modulating peritoneal fibrosis, including short courses of corticosteroids or tamoxifen, have been reported anecdotally but require validation, and the authors call for future multicenter registries to define optimal surveillance intervals and identify predictive factors for recurrence. Their central message for clinicians is straightforward: abdominal cocoon syndrome deserves a place on the differential diagnosis for any patient with recurrent or unexplained small bowel obstruction, especially those who have never undergone abdominal surgery, because timely recognition, careful bowel-preserving membrane excision, and structured postoperative monitoring can convert a potentially dangerous condition into one with an excellent outcome.

Subject of Research: Abdominal cocoon syndrome as a rare cause of small bowel obstruction

Article Title: Small bowel obstruction secondary to abdominal cocoon syndrome: Case report and review of the literature

Article References: Ben Ismail, I., Sghaier, M., Amari, R., Yaakoubi, J., Zenaidi, H., & Zoghlami, A. (2026). Small bowel obstruction secondary to abdominal cocoon syndrome: Case report and review of the literature. Heliyon, 12(15), Article e45437. https://doi.org/10.1016/j.heliyon.2026.e45437

Image Credits: AI Generated

DOI: 10.1016/j.heliyon.2026.e45437

Keywords: abdominal cocoon syndrome, sclerosing encapsulating peritonitis, small bowel obstruction, case report, computed tomography, adhesiolysis, fibrous membrane, tuberculosis, general surgery, Heliyon, idiopathic peritoneal sclerosis, laparotomy