Evaluating the Optimal Timing of Trans-Anal Irrigation for Low Anterior Resection Syndrome Post-rectal Cancer Surgery

• Water-based transanal irrigation system (Device): The procedure involves the introduction of water into the rectum and colon via the anus, which stimulates colonic reflex activity and acts as a mechanical bowel washout, thereby facilitating faecal evacuation. The device will deliver a controlled amount of warm water using a catheter - cone or balloon catheter - while sitting on the toilet. Once the desired amount of water has been introduced, the patient will expel the water and bowel contents. The procedure will take approximately 15-30 minutes, depending on the individual patient's response.

Primary outcomes

• Compare the effectiveness of two treatment regimens, initiated within different time frames following ostomy closure, in reducing the number of bowel movements in 24 hours. [From baseline to 3 months]: The difference in the change from baseline (V0) in the number of bowel movements (i.e. defecations) in 24 hours at 3 months after stoma closure (V2) between the early TAI group and the late TAI-treated group.

Secondary outcomes

• Efficacy of early administration of TAI in reducing the symptoms of LARS in the longterm period (up to 9 months). [From baseline to 9 months]: The difference in the change from baseline (V0) in the number of bowel movements in 24 hours at 6 and 9 months (V3 and V4) after stoma closure between the early TAI group and the late TAI-treated group.
• Efficacy of early administration of TAI in prevent LARS chronicity (prevent the increase of specific symptoms of LARS at all time points). [From baseline to 9 months]: The difference in the change from baseline (V0) in the Low Anterior Resection Syndrome (LARS) score (with a focus on the individual components of fecal urgency, incontinence, and incomplete evacuation) at various time points (V2, V3, V4) between the two groups (early TAI and late TAI-treated group). The LARS score ranges from 0 to 42 points. Patients are classified into one of three categories: no LARS (0-20 points), minor LARS (21-29 points) or major LARS (30-42 points).
• Efficacy of early administration of TAI improving quality of life at all time points [From baseline to 9 months]: Changes in quality of life (QoL) scores (across all domains of the Short Form-36 (SF-36) questionnaire) from baseline (V0) at all time points (V2, V3 and V4), and an evaluation of differences between the two groups. SF-36 scores for each domain range from 0 to 100, with higher scores indicating a more favourable health state.
• Efficacy of early administration of TAI improving patient satisfaction at all time points [From baseline to 9 months]: Change in patient satisfaction at all time points from baseline (V0) using a visual analogue scale (VAS), and evaluation of the differences between the two groups. The VAS consists of a 10 cm line with two endpoints representing 0 = completely unsatisfied and 10 = completely satisfied.
• Evaluate how various factors, such as the timing of TAI initiation, type of anastomosis, prior neoadjuvant radio-chemotherapy, and other patient baseline characteristics, influence LARS symptoms [From baseline to 9 months]: The variation in Low Anterior Resection Syndrome (LARS) scores in relation to factors such as the time at which TAI was initiated, the type of anastomosis, previous neoadjuvant radio-chemotherapy, and other baseline patient characteristics in the two groups was examined. The LARS score ranges from 0 to 42 points. Patients are classified into one of three categories: no LARS (0-20 points), minor LARS (21-29 points) or major LARS (30-42 points).

Other outcomes

• Safety and tolerability [From baseline to 9 months]: Evaluation of the frequency and severity of adverse events (AEs), serious adverse events (SAEs), devicerelated adverse events (ADEs) and serious device-related adverse events (SADEs) in the two groups

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Adults aged ≥ 18 years
* Colorectal resection for rectal cancer with a protective ostomy
* Integrity of the colorectal or coloanal anastomosis, as confirmed by each center's standard procedure
* LARS score > 30 (major LARS)
* Not previously treated with TAI (except for enemas)
* Completion of training on TAI irrigation by trained medical/nursing staff
* Use of only the Peristeen® Plus device for TAI
* Written informed consent

Exclusion Criteria:

* Neurological diseases
* Psychiatric disorders
* Refusal to consent to follow-up
* Current or planned pregnancy
* Known allergy to latex
* Presence of contraindications as outlined in the device's Instructions for Use (IFU), such as ischemic colitis, acute inflammatory bowel disease, or acute diverticulitis.