Uncomplicated sigmoid diverticulitis is a common disease in Western countries. Traditional management includes inpatient administration of either oral or intravenous antibiotics with resumption of oral intake as symptoms improve. Recent literature has however questioned both inpatient and antibiotic treatment. Indeed, both inpatient and antibiotic treatment are associated with non-negligible risks to patients. The aim of this trial is to assess the feasibility of a randomized controlled trial designed to determine whether nonantibiotic treatment of uncomplicated diverticulitis is safe in the outpatient setting.

Uncomplicated sigmoid diverticulitis is a common disease in Western countries. Traditional management includes inpatient administration of either oral or intravenous antibiotics with resumption of oral intake as symptoms improve. Recent literature has however questioned both inpatient and antibiotic treatment. Indeed, both inpatient and antibiotic treatment are associated with non-negligible risks to patients. The aim of this trial is to assess the feasibility of a randomized controlled trial designed to determine whether nonantibiotic treatment of uncomplicated diverticulitis is safe in the outpatient setting. It is designed as a pilot non-inferiority blinded randomized controlled trial. The estimated length of this pilot trial is 1 year. The target population is capable adults of who have a CT-diagnosed episode of uncomplicated diverticulitis who present to the Jewish General Hospital Emergency room.

Inclusion Criteria:

1. Age ≥ 18 and < 90 years old
2. Capable of giving informed consent
3. Lower abdominal pain and/or tenderness
4. Confirmed affection of left colon, including descending and sigmoid colon
5. Confirmed episode of acute uncomplicated diverticulitis on computed tomography (CT) scan defined as wall edema with or without fat stranding. Limited pericolic air with bubbles less than 5 mm in size, and less than 5cm from the colon wall, will be included as uncomplicated diverticulitis. Scan must be performed prior to enrollment and assessment for illegibility. The initial scan is not a study-specific procedure.

Exclusion Criteria:

1. CT scan shows complicated diverticulitis as defined by the presence of intraperitoneal free perforation (i.e. intraperitoneal contrast extravasation if intra-rectal contrast given, free air under diaphragms, disseminated intraperitoneal air), abscess, obstruction, fistulisation, and phlegmon.
2. Suspicion of colorectal cancer on CT scan
3. Immunosuppression (including but not exclusively insulin-dependent diabetes mellitus, chronic liver disease, ongoing chemotherapy, chronic renal failure with hemodialysis, corticosteroid and immunosuppressive medication)
4. Pregnancy and breastfeeding
5. Any comorbid infection requiring
6. High fever (≥ 38.5 ºC)
7. Significant leukocytosis (> 15 g/dL)
8. Abdominal pain worsening in the emergency, impeding ambulation and/or eating
9. Evidence of generalized peritonitis on physical exam
10. Intolerance to oral intake and/or persistent vomiting
11. Marked abdominal distension and/or signs of ileus on CT scan
12. Noncompliance/unreliability for return visits/lack of support system
13. Failed outpatient treatment not previously included in study within last 30 days
14. Cognitive, social or psychiatric impairment
15. For patients aged 65 years or older, a Charlson Comorbidity Score ≥ 5 as calculated on the following website: https://www.thecalculator.co/health/Charlson-Comorbidity-Index-(CCI)-Calculator-765.html 19-20.