It is estimated that approximately 15% to 20% of the subjects with sigmoid diverticulosis will develop acute diverticulitis, with diverticular abscess as the most common complication of sigmoid diverticulitis.

While cases with free perforations and diffuse peritonitis require emergency surgery, in cases with contained perforation and abscess formation, the approach is initially conservative. Due to its relative rarity, the treatment of diverticular abscess is not based on high-quality scientific evidence. Abscess size of 4-6 cm is generally accepted as reasonable cutoff determining the choice of treatment between antibiotic therapy and antibiotic therapy plus percutaneous drainage of the abscess.

A subgroup of patients will fail the conservative approach and require a surgical rescue strategy. However, the real incidence for conservative treatment failure after non-operative management of acute diverticulitis with abscess remain poorly understood, the knowledge of which could improve decision-making processes, treatment strategies, patient counseling, and even modify the planned treatment strategy in patients deemed at highest risk.

The early recognition of patients who show clinical signs of ongoing and worsening intra-abdominal sepsis due to perforation is important to ensure the success of this strategy. In the light of these, knowledge of risk predictors for failure is of utmost importance.

Owing the contrasting evidence summary, we set up a multicenter retrospective cohort study that merges the cases from twelve high-volume centers for emergency surgery in Italy to assess the short-term outcomes of initial non-surgical treatment strategies for AD with abscess formation (Hinchey Ib and II) in a large number of patients, and identify risk factors associated with adverse outcomes, to help facilitate appropriate patient selection and assess the optimal treatment strategy for this peculiar subgroup of patients.

The purpose of this study is to describe the incidence and risk factors for conservative treatment (antibiotics alone or antibiotics plus percutaneous drainage) failure after non-operative management of acute diverticulitis with abscess using a large multicenter patient series.

The present study is designed as a multicenter retrospective observational study conducted at twelve secondary and tertiary Italian teaching surgical centers on CT-diagnosed hemodynamically stable patients (≥18 years) with perforated acute diverticulitis with abscess (with or without extraluminal air) initially treated non-surgically.

The rate of failure of non-operative treatment for complicated acute diverticulitis patients with abscess formation and the risk factors of failure of the non-surgical treatment will be assessed.

Failure of the conservative treatment is defined as lack of clinical improvement in the general conditions of the patient during index hospital admission, requiring urgent surgery to treat intra-abdominal sepsis.

Inclusion Criteria:

1. Adult (≥18 years of age) patients
2. Patients diagnosed with acute diverticulitis with radiological findings of contained perforation (modified Hinchey classification Ib and IIa/b).
3. Patients who are initially managed conservatively according to contemporary guidelines.

Exclusion Criteria:

1. Patients with perforated diverticulitis with peritonitis (Hinchey III or IV stages).
2. Patients with clinically assessed generalized peritonitis.
3. Patients diagnosed with colonic cancer mimicking acute diverticulitis with abscess.
4. Requirement for urgent or emergent surgery decided immediately following hospital admission.

The patient cohort consists of adult (≥18 years of age) patients with a diagnosis of acute diverticulitis complicated by localized intra-abdominal abscess formation with pericolic or pelvic localization and/or localized pericolic extraluminal air, corresponding to the modified Hinchey classification Ib and IIa/b. These patients should be managed conservatively according to contemporary guidelines, but still have a high probability for failure of conservative treatment.