The goal of this observational study is to study the emergency surgical treatment of diverticular disease in Sweden outside clinical trials. The main questions it aims to answer are:

• Which is the preferred surgical method of acute diverticular disease in Sweden?
• Which are the short and long-term outcomes of the different surgical methods?

Researchers will compare the different methods to see if there is a surgical operation that is superior for the treatment of acute diverticulitis.

A retrospective study of patients who were admitted to a Swedish hospital between 1st July 2014 and 31st December 2020 with an ICD-10 code for diverticular disease of the large intestine (K57.2- K57.9) will be included. Patients who underwent procedures relevant to diverticulitis will be identified and therefore will be included. Procedures will be grouped into two categories: Laparoscopic peritoneal lavage (Group I), and sigmoid resection with or without stoma (Group II).

The cohort will be studied from 1st January 1997 until the index date aiming to assess comorbidities, previous abdominal surgeries, and admissions for diverticular disease. A Charlson Comorbidity Index (CCI) system adjusted for Swedish ICD-10 version will be used to calculate a composite score to reflect comorbidity.

Inclusion Criteria:

• All patients aged 18 years or older who were admitted to a Swedish hospital between 1st July 2014 and 31st December 2020 with an ICD-10 code for diverticular disease of the large intestine (K57.2- K57.9).
• Emergency admissions.
• Patients who underwent procedures relevant to diverticulitis.

Exclusion Criteria:

• Patients who were diagnosed with colorectal cancer before the index date.
• Patients with synchronous operations that are supposed to be irrelevant to acute diverticulitis.

The study will be based on a national cohort gathered from National Patient Register, the National Cancer Register and the Cause of Death Register, obtained by the Swedish National Board of Health and Welfare.