This was a randomized, multicenter, controlled, double-blind superiority clinical trial involving patients undergoing rectal cancer surgery and requiring an end colostomy without mesh. Participants were randomized to undergo one of two exteriorization techniques. The study protocol was approved by the regional ethics committees of the participating hospitals, in accordance with the Declaration of Helsinki. All patients provided written informed consent. The study was registered at ClinicalTrials.gov (Identifier: NCT04397783) and adhered to the CONSORT 2010 guidelines for randomized controlled trials (RCTs).

Five tertiary hospitals participated in the study. All surgical procedures were performed in accredited colorectal surgery units and were conducted or supervised by surgeons certified by the European Society of Coloproctology (ESCP).

Inclusion criteria: Patients with rectal cancer scheduled to undergo a permanent end colostomy following abdominoperineal resection, intersphincteric rectal resection, or a Hartmann procedure, aged 18 to 85 years, and undergoing surgery via laparotomy, laparoscopy, or robotic surgery.

Exclusion criteria: Patients scheduled for other types of stomas (e.g., temporary or non-end colostomies), those requiring emergency or palliative surgery, patients with a history of previous hernias or mesh implants (except for inguinal hernia), those undergoing surgery involving the extraction of the surgical specimen through the colostomy site, and patients whose colostomies were not previously marked by a nurse stomatherapist.

Preoperative preparation, patient positioning, anesthetic management, and postoperative care followed local protocols, with the surgical approach determined at the surgeon’s discretion. The descent of the splenic flexure was left to the surgeon’s judgment, though this information was recorded in the case report form (CRF).

To standardize the surgical technique for colon exteriorization and colostomy formation, a demonstration video and an instructional booklet were created.

Using the previously marked site by a nurse stomatherapist, a circular disc of skin and a small amount of subcutaneous tissue, large enough to allow the stoma to sit comfortably, was excised. The colostomy was exteriorized through a transperitoneal and transrectus route within the rectus sheath. While exteriorization through the external oblique muscle was not an exclusion criterion, this information was also included in the CRF.

In the longitudinal incision group, a longitudinal incision of approximately 3 cm was made on the aponeurosis of the anterior rectus sheath, depending on the colon’s diameter. Two interrupted Prolene 2/0 sutures (Ethicon, Johnson & Johnson) were placed at the superior and inferior edges of the incision for reinforcement.

In the cruciate incision group, a longitudinal incision approximately 3 cm in length was made on the aponeurosis of the anterior rectus or external oblique. Additionally, a transversal incision of about 2 cm in length (1 cm on each side) was made.

When the stoma was located above the semilunar line, the posterior rectus sheath was incised in a manner similar to the anterior surface, but without reinforcement stitches for cases involving the longitudinal incision.

The lengths of the incisions in the aponeurosis, as well as the diameter of the colon and stoma, were recorded in the CRF.

The height of the stomal nipple was at least 1–2 cm and was not fixed either intraperitoneally or to the lateral edges of the fascial opening. Mucocutaneous suturing with interrupted absorbable sutures was used to secure the stoma to the skin.

The primary objective was to compare the PH rate at 2 years of follow-up, diagnosed through physical examination and CT scan. PH was defined as any clinically detectable bulge in the vicinity of the colostomy, identified by digital palpation within the stoma, with the patient in the supine position at rest and during the Valsalva maneuver. CT scans were performed following the protocol of each center and reviewed by radiologists who were blinded to the type of surgery, and the findings were classified according to the Moreno-Matias scale [21].

The secondary objectives were to analyze the rate of symptomatic and clinically relevant PH at 2 years post-surgery, the incidence of early complications related to the stoma and its construction one month post-surgery, the incidence of postoperative complications assessed according to the comprehensive complication index (CCI) scale [22], readmissions, need for interventions due to PH, and the quality of life analysis using the EORTC QLQ-C30 scale [23].

Prospective data collection was conducted, and patients were followed up according to the study protocol using individual case report forms (CRFs). Demographic information, known risk factors for PH, co-morbidities, and surgical data were collected. Postoperative complications were recorded at one-month post-surgery, and at 12 and 24 months, data on readmissions, stoma complications, PH diagnosis via physical examination and CT scan, the presence of symptoms associated with PH, reinterventions for PH, and quality of life scores were also collected. All data were systematically recorded in the Redcap platform.

The primary objective of the study was to assess whether there were statistically significant differences between the two colostomy techniques. Assuming a clinical incidence of parastomal hernia (PH) of 50% with the conventional cross-shaped incision and an expected incidence of 20% with the reinforced longitudinal incision, a type I error (α) of 0.05, and a power of 80% (β = 0.20), the required sample size was calculated to be 84 patients (42 in each group). Accounting for an expected 10% loss to follow-up, the total sample size was adjusted to 94 patients (48 in each group).

Randomization was performed using sealed envelopes with a 1:1 allocation ratio. The envelopes were prepared in bundles of twenty per hospital by the Hospital Universitario Donostia, without the involvement of the investigators. Neither the patient nor the surgeon assessing the patient postoperatively were informed of the treatment group to which the patient had been assigned.

The STATA 18.0 statistics software program was used. Continuous quantitative variables are expressed as mean and standard deviation or median and first-third quartile range, in cases where the data do not follow a normal distribution. Categorical variables are summarized through absolute frequency and relative frequency. Quantitative variables are analyzed using the Student t or Mann–Whitney U test; categorical variables were compared with Chi-square test or Fisher’s exact test. All hypothesis tests are bilateral, with a significance level of 0.05.