Acute diverticulitis is managed according to two questions: whether the disease is uncomplicated or complicated, and how vulnerable the patient is to a poor course. Diverticular bleeding is a separate problem, managed by stopping the haemorrhage and lowering the chance that it returns.
Uncomplicated diverticulitis
Uncomplicated diverticulitis is inflammation confined to the colonic wall and the pericolic fat, without abscess, perforation, fistula or obstruction. An immunocompetent patient who is not frail, can keep fluids down and has no signs of systemic infection can usually be treated at home, with review within 7 days or sooner if the condition deteriorates. A clear liquid diet is reasonable during the acute phase, advancing as symptoms improve; a patient who cannot advance the diet after 3–5 days should be reassessed.
Antibiotics are no longer routine in mild uncomplicated diverticulitis. In immunocompetent patients without signs of systemic inflammation, randomised trials and a meta-analysis found no difference in time to resolution, progression to complications, recurrence or need for surgery between antibiotics and no antibiotics, so current guidelines recommend against prescribing them, a strong recommendation based on high-quality evidence. Antibiotics are still advised when the course is more likely to be difficult: immunosuppression, frailty or comorbidity, refractory symptoms or vomiting, a C-reactive protein above 140 mg/L, a white-cell count above 15 × 10⁹/L, or CT showing a fluid collection, a longer inflamed segment or pericolic extraluminal gas. When antibiotics are needed, oral administration is preferred wherever possible, and the regimen covers Gram-negative organisms and anaerobes — commonly a fluoroquinolone with metronidazole, or amoxicillin–clavulanate alone — usually for 4–7 days, and longer in immunocompromised patients.
Complicated diverticulitis
Complicated diverticulitis is disease that has extended beyond the colonic wall: an abscess, perforation with peritonitis, a fistula or an obstruction. It always needs antibiotics, and the further decision is whether the infected collection can be controlled without an operation.
An abscess is judged by size. A small collection, roughly 4–5 cm or less, can be given a trial of antibiotics alone under close observation, because antibiotics reach it well enough; a larger one is usually drained percutaneously together with antibiotics, since drug penetration into a larger cavity is poor. If the patient worsens or the collection does not shrink, surgery follows.
Perforation with generalised peritonitis is a surgical emergency, and the operation is chosen by how well the patient is. A stable patient without major comorbidity may have a primary resection with an anastomosis, with or without a protecting stoma, whereas a critically ill or multimorbid patient is usually treated with a Hartmann’s procedure — resection of the diseased segment and an end colostomy. Laparoscopic peritoneal lavage and drainage can avoid a stoma, but it carries a higher rate of reoperation and intra-abdominal abscess, so it is reserved for selected patients.
Diverticular bleeding
Diverticular bleeding stops on its own in most patients, so management begins with resuscitation and transfusion when required. Colonoscopy after bowel preparation is both diagnostic and therapeutic: it identifies the responsible diverticulum and lets the endoscopist apply haemostasis, usually by clipping, band ligation, epinephrine injection or thermal therapy. Band ligation and direct placement of clips are associated with lower rates of early rebleeding than indirect clipping. When endoscopy cannot control the bleeding, transcatheter arterial embolisation or surgery is used.
Preventing recurrence
After a first episode of diverticulitis, a further episode is common, and the risk rises with each recurrence. To lower it, patients should eat a high-quality diet, keep a normal body mass index, stay physically active, stop smoking, and avoid regular use of non-steroidal anti-inflammatory drugs, except aspirin taken for secondary cardiovascular prevention. 5-aminosalicylic acid, probiotics and rifaximin have not been shown to prevent recurrence and are not recommended. Elective segmental resection should not be offered because of the number of episodes alone; it is a personalised decision that weighs the severity and pattern of the disease, the patient’s preferences and quality of life, and the risks of surgery, and it reduces but does not eliminate the risk of further diverticulitis. Patients should also understand that the most dangerous presentation is usually the first: complicated diverticulitis is more often the first episode than a recurrence.