This observational study was conducted across five surgical centers in Italy, including both academic and community hospitals, from January 2017 to December 2022. The study aimed to evaluate outcomes in patients with acute perforated sigmoid diverticulitis classified as Hinchey Stage III or IV. All consecutive patients aged 18 years or older who presented with acute perforated sigmoid diverticulitis and underwent emergency colonic resection were included. Patients were excluded if they had Hinchey Stage I or II diverticulitis, postoperative confirmation of malignancy, or underwent laparoscopic surgery. This approach ensured a well-defined patient cohort for consistent and reliable analysis.

This multicenter, prospective observational study evaluated clinical outcomes in adult patients with acute perforated sigmoid diverticulitis classified as Hinchey Stage III or IV, who underwent emergency open colonic resection in five surgical centers in Italy. The study period extended from January 2017 to December 2022 and involved both academic and community hospitals, providing a representative overview of real-world surgical practice.

All consecutive patients aged 18 years or older with a clinical and radiological diagnosis of Hinchey III-IV perforated sigmoid diverticulitis were considered for inclusion. Eligible patients were required to be clinically stable at presentation, enabling them to undergo either primary anastomosis with diverting loop ileostomy or Hartmann's procedure , based on surgeon judgment and intraoperative findings.

Exclusion criteria included:

• Hinchey Stage I or II diverticulitis
• Postoperative confirmation of malignancy as the primary cause of the perforation
• Laparoscopic procedures instead of open resections
• Patients with severe hemodynamic instability, septic shock, or uncontrolled sepsis The primary objective was to compare short- and long-term outcomes between primary anastomosis with diverting loop ileostomy and Hartmann's procedure, including postoperative morbidity and mortality, quality of life, stoma reversal rates, and hospital readmissions. Secondary endpoints included surgical site infections, length of hospital stay, and long-term complications such as parastomal hernia.

This structured design ensured a well-defined and homogeneous study cohort for outcome comparison, allowing for the generation of meaningful real-world evidence on the optimal surgical management of complicated diverticulitis.

Inclusion Criteria:

• Adults aged ≥18 years
• Clinical diagnosis of perforated sigmoid diverticulitis (Hinchey Stage III or IV)
• Clinically stable and suitable for undergoing emergency colonic resection
• Eligible to receive either primary anastomosis with diverting loop ileostomy or Hartmann's procedure
• Informed consent provided by the patient or a legal surrogate

Exclusion Criteria:

Hinchey Stage I or II diverticulitis

• Postoperative confirmation of malignancy as the primary cause of perforation
• Laparoscopic surgery instead of open colonic resection
• Unstable patients with severe sepsis, septic shock, or significant hemodynamic compromise

The study population consists of adult patients (≥18 years) who presented with acute perforated sigmoid diverticulitis (PSD) classified as Hinchey Stage III or IV and underwent emergency open colonic resection. All participants were clinically stable at the time of surgery and were eligible to receive either primary anastomosis with diverting loop ileostomy (PADLI) or Hartmann's procedure (HP).

Patients with Hinchey Stage I-II diverticulitis, postoperative confirmation of malignancy, laparoscopic surgery, or hemodynamic instability were excluded to ensure a well-defined and homogeneous study cohort for consistent outcome analysis.

Individual participant data (IPD) will not be shared. The decision not to share IPD is based on institutional policies and ethical considerations related to patient confidentiality and data protection. Additionally, no data-sharing infrastructure has been established within the current study protocol, and there are no plans at this time to develop such a framework.