Diverticulitis

Diverticulitis is one of the presentations of diverticular disease and is most often a complication of colonic diverticulosis. Differentiating one from the other is critical since uncomplicated diverticulosis is mostly asymptomatic and acute diverticulitis is a potentially life-threatening illness.

On imaging, non-complicated diverticulitis is characterized by a focal fat stranding adjacent to a colonic diverticulum, usually the sigmoid. A small amount of extraluminal fluid and gas locules may be present. 

Diverticulitis is a complication of diverticulosis, and the demographics of the condition are therefore similar, with elderly patients being most at risk.

Symptoms of diverticulitis usually begin in the left iliac fossa with unremitting pain and accompanying tenderness. An ill-defined mass may also be palpable representing the inflammatory phlegmon

As the disease progresses and becomes more generalised (stage III and IV - see Hinchey classification of acute diverticulitis), signs and symptoms also become widespread and indistinguishable from other causes of generalised peritonitis.

Diverticulitis is the result of obstruction of the neck of the diverticulum, with subsequent inflammation, perforation, and infection 2. Early changes of local inflammatory phlegmon may later progress to abscess formation and generalised peritonitis.

Although CT is the modality of choice for the diagnosis and staging of diverticulitis, a dedicated ultrasound study may be able to confidently characterize this condition.

  • diverticula are characterized as bright bowel outpouching (also referred as bowel bright “ears”) showing some degree of acoustic shadowing due to the presence of gas or inspissated feces 4
  • echogenic and non-compressible fat suggesting an inflammatory process of the surrounding fat planes 4
  • thickened bowel wall (>4 mm) 4
  • presence of organized collections imply abscess and thus complicated diverticulitis, which requires further CT assessment
  • pericolic stranding, often disproportionately prominent compared to amount of bowel wall thickening 2,3
  • segmental thickening of bowel wall
  • enhancement of colonic wall 
    • usually has inner and outer high-attenuation layers, with a thick middle layer of low attenuation
  • diverticular perforation 
    • extravasation of gas and fluid into pelvis and peritoneal cavity
  • abscess formation (seen in up to 30% of cases)
    • may contain fluid, gas or both
  • fistula formation (usually a chronic complication)
    • gas in the bladder
    • direct visualization of a fistulous tract

Treatment depends on a host of factors, especially patient co-morbidities and stage of the disease.

For localised disease (stage I and II) conservative management with IV antibiotics and rehydration usually suffices. If the first attack of diverticulitis is treated successfully without surgery, most patients do not go on to have further episodes (66-75%). But some have multiple repeated attacks and go on to require surgery 1.

If the abscess is large, then percutaneous drainage under CT or US may be beneficial (successful in 70-90% of cases) 1.

Recognised complications include 1-5:

Surgery is the treatment of choice in patients:

  • who progress to stage III or IV
  • who fail medical management
  • in whom carcinoma cannot be excluded
  • who have multiple (2 or more) attacks
  • who develop fistulas

Surgical options depend on whether surgery is elective or emergent and on the quality of bowel preparation. For elective surgery, the aim is to perform a single-stage segmental colectomy (usually sigmoid colectomy) with a primary end to end anastomosis. In emergent cases, either on-table lavage with primary anastomosis or a two-stage procedure is performed. The two-stage procedure consists of a Hartmann colectomy with end colostomy and rectal stump closure, which is subsequently closed by a second operation. This carries a mortality of less than 5% 1.

General imaging differential considerations include:

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Article information

rID: 6201
Synonyms or Alternate Spellings:
  • Inflamed diverticulum
  • Colonic diverticulitis

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Cases and figures

  • Case 1
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  • Case 2
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  • Case 3: sigmoid diverticulitis on ultrasound
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  • Perforated divert...
    Case 4: with local perforation
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  • Case 5: sigmoid diverticulitis on MRI
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  • Case 6: with abscess
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  •  Case 8
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  • Gas-filled fistul...
    Case 7: with perforation into anterior abdominal wall
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  •  Case 9
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  • Case 10: with perforation
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  • Case 11
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  • Case 12: with pericolonic abscess
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  • Case 13
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  • Case 14
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  • Case 15
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  • Case 16: jejunal diverticulitis
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  • Case 17: with pericolic abscess
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  • Case 18
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  • Case 19
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  • Case 20
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  • Case 21: cecal diverticulitis
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  • Case 22: colovesical fistula
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  • Case 23: acute diverticulitis
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  • Case 24
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  • Case 25
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  • Case 26
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