This study focuses on the treatment for complicated diverticulitis classified as Hinchey I-IV.

The aim of this prospective observational study is to evaluate type of treatment and the success rate of treatment in acute complicated diverticulitis (ACD) at participating hospitals in Sweden and Norway. Furthermore, the effects on quality of life for this patient group will be evaluated.

Diverticular disease is among the five most common gastrointestinal disorders. Among individuals with diverticulosis the lifetime risk of suffering from diverticulitis is between 4 and 25%. The most common complications of diverticulitis are perforation, abscess formation, fistula and obstruction. Emergency surgery is necessary in up to 25% of diverticulitis patients.

The American Society of Colon and Rectal Surgeon (ASCRS, 2014) recommends abscess drainage and antibiotic treatment and later elective surgery as treatment for complicated diverticulitis, Hinchey I and II (*) for abscesses larger or equal to 5 cm while others recommend resection surgery only for Hinchey II patients. The recommendations for surgery are motivated by the belief that surgical treatment will reduce the risk for relapsing disease with intra-abdominal/pelvic sepsis by more than 40%. However, these recommendations are based on small and out-dated retrospective studies.

Perforated diverticulitis with radiologically confirmed free intraperitoneal air is a life threatening disease with significant mortality and morbidity therefore several guidelines recommend acute surgical intervention. However, a conservative non-surgical approach for the treatment of perforated diverticulitis has been shown to be effective for hemodynamically stable patients with radiologically confirmed free air. A Swedish study recently showed the incidence of complicated diverticulitis to be 9/100.000 inhabitants/year of which about one third required acute surgical intervention. The most common operation in perforated diverticulitis is Hartman's procedure, which involves removal of the involved sigmoid segment, a terminal colostomy and blind closure of the rectal stump. Also primary resection of the sigmoid colon with anastomosis is frequently used, sometimes combined with a loop-ileostomy. Laparoscopic lavage without resection has emerged as an alternative operation method. However, the SCANDIV trial showed limitations of laparoscopic lavage with a higher frequency of re-operation in the lavage group compared to primary resection after 90 days. Nevertheless, several meta-analysis based on three randomized studies showed comparable rates regarding overall mortality and morbidity in laparoscopic lavage versus resection in perforated diverticulitis.

For patients with diverticulitis complicated by fistula (colovesical, colovaginal or colo cutaneous) surgery is the recommended treatment. This condition, however, rarely presents in an acute setting.

In Scandinavia a conservative approach restricted to antibiotics and percutaneous drainage is widely accepted as solitary treatment for patients with diverticular abscesses (Hinchey I and II). Also hemodynamically stable and non-immunocompromised patients with perforated diverticulitis (Hinchey III) are often managed conservatively with antibiotics and, if required, percutaneous drainage. Acute surgical intervention is performed if the condition of the patient deteriorates during hospital stay or if the CT shows signs of faecal peritonitis (Hinchey IV). Elective surgery for patients after an episode of acute complicated diverticulitis (Hinchey I-III) is usually reserved for patients with frequent relapses or with a persisting diverticular abscess.

However, some patients have frequent relapses with abscesses which are difficult to treat and suffer for a long time until the problem is solved. This clinical experience raises the question whether the Scandinavian treatment policy might be too conservative sometimes. Although elective surgery itself can lead to new complications and eventual deterioration in quality of life, early resection might be a better option for some patients. Also the quality of life for patients after conservative management of complicated diverticulitis has not been examined in detail previously.

* I Pericolic abscess II Distant/pelvic abscess III Generalized purulent peritonitis IV Faecal peritonitis

Inclusion Criteria:

• Age ≥18 years
• Clinical symptoms and laboratory results suspicious for diverticulitis
• CT findings of complicated diverticulitis with extraluminal air, presence of abscess with or without fistula or operative findings of complicated diverticulitis in an emergency setting

Exclusion Criteria:

• patients with uncomplicated diverticulitis
• unable to give informed consent.
• language barrier

All patients 18 years and older with complicated diverticulitis that are admitted to hospital. Diagnosis verified with computed tomography.