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, a non-complicated diverticulitis is characterised 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 II and IV - see Hinchey classification of acute diverticulitis) signs and symptoms also become generalised, and indistinguishable from other causes of generalized peritonitis.

Diverticulitis is the result of obstruction of the neck of the diverticulum, with subsequent inflammation, perforation and infection. 2 Initially inflammation and infection are contained by inflammatory phlegmon. The infection may later progress to abscess formation and/or generalised peritonitis.

CT is the modality of choice for the diagnosis and staging of diverticulitis. Appearances include: 2

  • pericolic stranding, often disproportionately prominent compared to the amount of bowel wall thickening 3
  • segmental thickening of the bowel wall
  • enhancement of the colonic wall 
    • usually has inner and outer high-attenuation layers, with a thick middle layer of low attenuation
  • diverticular perforation 
    • extravasation of air and fluid into the pelvis and peritoneal cavity
  • abscess formation (seen in up to 30% of cases)
    • may contain fluid, gas or both
  • fistula formation
    • gas in the bladder
    • direct visualisation of a fistulous tract

Recognised complications include: 1

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

Surgical treatment

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 are 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.

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

General imaging differential considerations include

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Article Information

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

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    Perforated divert...
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    Case 6: with abscess
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    Case 7: sigmoid diverticulitis on MRI
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    Case 10: with perforation
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    Case 12: with pericolonic abscess
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    Case 16: jejunal diverticulitis
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    Case 17: with pericolic abscess
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    Case 21: caecal diverticulitis
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    Case 23: acute diverticulitis
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    Case 22: colovesical fistula
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