creation date: 2026-06-16 05:29
tags: Pathologies
Diverticulitis
Background
Definitions
Colonic diverticulitis refers to inflammation in and adjacent to a diverticulum.
Diverticulosis refers to the presence of diverticula, which are sac-like protrusion of colonic mucosa.
Diverticular disease refers to clinically significant and symptomatic diverticulosis due to diverticulitis or its complications.
Pathogenesis
The pathogenesis of diverticulosis is unclear. Diverticula develop at weak points in the muscle wall. Theories suggest development involves:
- Genetics
- Gut microbiome
- Abnormal colonic motility
In western populations, diverticulosis is typically left-sided and “false” (mucosa and submucosa herniate through. In contrast, Asian populations see more predominantly right-sided diverticula and include all layers of the colon wall. Migration studies has suggested an ethnicity-related association more so than geographic.
The development of diverticulitis was previously thought to involve the obstruction of diverticula causing pressure and perforation but is now thought to be rare. Newer theories suggest chronic inflammation from chronic systemic conditions, in addition to gut microbiome factors, may cause diverticulitis to develop.
Risk Factors
Epidemiology
Prevalence is age related, with number and size increasing with age. The prevalence within individuals <50 is rising.
Approximately 4% of patients with diverticulosis develop diverticulitis.
Risk factors for diverticulosis
- Age >60
- Male
- Smoking
- Elevated BMI
Risk factors for diverticulitis
- Diet (high intake of red meat or Western dietary pattern)
- Lack of physical activity
- BMI
- Smoking
- Immunosuppression (eg. corticosteroids, chemotherapy)
- NSAIDs
- Menopausal hormone therapy
- Opiates
Clinical Presentation
Signs & Symptoms
Acute diverticulitis manifests as:
- Sudden onset, constant abdominal pain (most typically in LLQ)
- Fever
In rarer cases, findings may include:
- Palpable mass (from abscess)
- Change in bowel habits (constipation, diarrhea)
- Urinary symptoms (urgency, frequency, dysuria)
History & Physical Exam
History should include:
- Prior colonoscopy
Physical should include a pelvic exam as appropriate for ruling out other abdominal pathology.
Diagnosis
Criteria
Diagnosis of diverticulitis is made with abdominal CT with PO and IV contrast.
- Localized bowel wall thickening (>4 mm)
- Pericolonic fat stranding secondary to inflammation
- Presence of colonic diverticula
Work-up
Laboratory studies
Routine tests include:
- CBC (leukocytosis)
- Electrolytes
- Urinanalysis
- CRP (elevated)
In patients with suspected perforation and diffuse peritonitis:
- ALT/AST
- ALP
- Bilirubin
- Amylase/lipase
Stool studies are only performed to rule out infectious etiologies.
Imaging
An abdominal CT scan with oral and IV contrast is routinely performed. An ultrasound may also be performed if CT is unavailable.
Exclusion of underlying malignancy
Colonoscopy is not indicated for acute diverticulitis due to the risk of perforation. A colonoscopy can be performed to if there is clinical suspicion for malignancy 6-8 weeks after, once symptoms are completely resolved.
Differential
Differential diagnoses include those causing abdominal pain.
Red Flags / Complications
Complications of diverticulitis can be found on CT during diagnosis:
- Bowel obstruction (dilated loops of bowel with air-fluid levels around pericolonic inflammation)
- Abscess (fluid collections surrounded by area of inflammation)
- Fistula (extracolonic air collections within non bowel organs)
- Perforation and peritonitis (free air)
Management
Inpatient Treatment
Indications
- CT shows complications
- CT should uncomplicated diverticulitis but with one or more of:
- Sepsis/SIRS
- Severe abdominal pain with failure to control in the ED
- Age >70 years
- Significant comorbidities
- Immunosuppression
- Intolerance of oral intake secondary to bowel obstruction or ileus
- Poor adherence to care or unreliability for return
- Failed outpatient treatment
Treatment
Treatment of diverticulitis
Antibiotics therapy starts with IV options against gram-negative rods and anaerobes:
- Low-risk: ceftriaxone 2g IV once daily PLUS metronidazole 500 mg IV q8h
- High-risk: pip-tazo 4.5 g IV q6h OR ceftazidime 2g IV q8h PLUS metronidazole 500 mg IV q8h
Following stabilization of inflammation (resolution of abdominal pain and tenderness; typically 3-5 days), antibiotics are transitioned to PO for a total 10-14 day antibiotics course (including IV days):
- Ciprofloxacin PLUS metronidazole
- Amoxicillin-clavulanate
Other adjuncts to therapy are:
- IV fluids for volume deficits until tolerating PO liquids
- Pain control
Inpatient diet should be:
- Bowel rest until clinical improvement
- Liquid diet
- Progress to solids as tolerated
Treatment of complications
The management depends on the complication. In general, frank perforation, obstruction, and fistula will likely require surgical management.
Microperforations and abscesses may be able to be managed nonsurgically. In particular, smaller abscesses (<4 cm) can trial antibiotic therapy alone. Larger abscesses may require percutaneous drainage.
Disposition
Discharge can be considered after significant clinical improvement after 2-3 days of IV antibiotics. Criteria for discharge are:
- Normal vitals
- Resolution of severe abdominal pain
- Resolution of significant leukocytosis
- Tolerance of oral diet
- Resumption of bowel movements
Outpatient Treatment
For patients who do not meet indication for inpatient treatment, antibiotic therapy is not indicated.
Outpatient therapy consist of:
- Pain management
- Liquid diet
Antibiotics may be considered in cases of major comorbidities, immunocompromised status, or signs of systemic disturbance. Typical courses are 4-7 days:
- Amoxicillin-clavulanate 875-125 mg q8h
- Ciprofloxacin 500 mg q12h PLUS metronidazole 500 mg q8h
For patients with no improvement or new onset fever and/or worsening pain, admission for inpatient care and CT scan for new complications are indicated.