The treatment of patients with diverticulitis has changed significantly in recent years. Patients may be treated on an outpatient basis in the absence of systemic signs. If they demonstrate mild abdominal tenderness, low-grade fever, and the ability to tolerate oral intake, reliable patients can be treated with oral antibiotics, low residue diet, and close follow-up. Antibiotics should be directed toward typical lower gastrointestinal flora. Oral antibiotic regimens, based on consensus rather than randomized trials, include gram-negative coverage typically with a fluoroquinolone or sulfa-based drug. Anaerobic coverage should be provided with metronidazole or clindamycin. Patients not meeting outpatient criteria will need to be hospitalized for intravenous fluids and antibiotics. Immunocompromized patients will also benefit from inpatient treatment. Intravenous antibiotic regimens such as ampicillin-sulbactam, timentin-clavulanate, or piperacillin/tazobactam are appropriate in this setting. For patients who require intravenous antibiotics but have a demonstrated beta-lactam intolerance, alternative regimens consist of a fluoroquinolone and metronidazole or monotherapy with a carbapenem. Subsequent to successful treatment of acute diverticulitis with conservative therapy, approximately 1/3 of patients will experience another episode. After a second episode, another 1/3 of patients will be subjected to a third attack. Of all patients with diverticulitis, about 1/5 will ultimately require operative intervention [17].

Elective resection can be safely performed 4–6 weeks after the most recent episode has resolved. Guidelines from the American Society of Colorectal Surgeons (ASCRS) taskforce in 2000 recommended segmental resection after two uncomplicated attacks of diverticulitis or after a single episode of complicated diverticulitis. This traditional surgical dictum has been called into question since that time. In a study from the Lahey Clinic, Hall et al. demonstrated that although diverticulitis recurrence was common (36%) following an initial attack that was managed medically, complicated recurrence was uncommon (3.9%) over a follow-up period of 5 years. Right-sided diverticulitis also had a low rate of recurrence [18]. Family history of diverticulitis, length of involved colon >5 cm, and a retroperitoneal abscess were independent risk factors associated with recurrence. In light of these and other data [19] we have become more liberal in our application of expectant management, but still generally endorse the guidelines from the ASCRS while also taking into consideration:

Overall, morbidity after open colectomy for diverticulitis ranges from 9 to 54%, while mortality ranges from 0 to 1.2%. Risk factors for morbidity after elective left colectomy for diverticular disease are [20]:

Traditionally, patients afflicted with an episode of diverticulitis are initially treated with bowel rest. Once the clinical picture begins to improve they are instructed to consume a clear liquid diet. The diet is then advanced as tolerated. A more aggressive approach limits the concept of bowel rest, with immediate resumption of a low-residue diet instead. Once an acute flare has subsided, a high fiber maintenance diet has been advocated. This may decrease both the formation of diverticula and the chance of a symptomatic recurrence. This recommendation is based on the idea that long-term fiber supplementation produces a bulky stool that results in a larger diameter colon, thereby decreasing segmentation and subsequent pressure, which may be protective in the formation of diverticula. The data in support of this and other dietary measures is not conclusive. Other anecdotal recommendations are to avoid caffeine, alcohol, and tobacco but the data do not indicate that these are risk factors [21]. Additional dietary restrictions frequently given to patients are to avoid seeds, corn, and nuts. While this advice makes intuitive sense, these small difficult to digest particles could become lodged in a diverticulum and predispose a patient to diverticulitis or perforation, a large observational study did not reveal an association with diverticular disease [22].

Small localized and intramural abscesses may resolve without intervention. Larger abscesses (>3 cm) are best managed with percutaneous drainage. After source control has been achieved, clinical improvement should occur within 48 h. In the absence of clinical improvement or if the condition of the patient worsens, repeat imaging may identify a previously undetected abscess, or worsening of an existing abscess, which would prompt a change of therapy. Conservative management of diverticulitis has grown more aggressive, recognizing the benefits of converting an emergency surgical intervention into an elective one. Advances in imaging, critical care, parenteral nutrition, and interventional techniques have lent themselves towards this goal. Mutch et al. examined the efficacy of nonoperative management in acute complicated diverticulitis [23]. Complicated diverticulitis was defined as having an associated abscess or free air diagnosed by CT scan. Out of 136 patients, 28% required percutaneous drainage, and 27% required parenteral nutrition. In total, only 5% (seven patients) failed medical management and required urgent surgery. Forty-eight percent then went on to have elective resections of their diverticular disease. Contraindications to a nonoperative approach include hemodynamic instability, generalized peritonitis, CT scan with significant free air and fluid, or immunosuppression. Operative intervention is also required for clinical deterioration after a period of expectant management.