Diverticulitis

Common in older patients
Muscle abnormality in sigmoid colon with out pouching from colonic wall
Deposition of elastin in taeniae cause contraction and shortening of bowel with corrugation of mucosa and circular muscle layers – this causes thickening of sigmoid with interdigitating folds
Diverticula arise at points of weakness where the vasa recta penetrate the circular muscle layer
Each diverticulum is a pouch of mucous membrane with vey thin covering of longitudinal muscle
Commonest in sigmoid colon, localized to proximal colon in 10% cases
Diverticulitis
- Most common complication
- Due to fecal retention within diverticulum
- Leads to ischemic necrosis with microperforation
- Formation of pericolic abscess
- Adherence of chronic inflammatory mass may result in fistula formation (adjacent to urinary bladder)
- Rarely abscess can perforate directly into peritoneal cavity (fecal peritonitis)
Bleeding can occur from a diverticulum
- More common from wide-mouthed right side colon diverticula

USG: in diverticulitis, graded compression at colic site shows the pericolic abscess
CT
- High attenuation
- Mimics polyp on 3D endoluminal view
- Diverticulitis
  - Diverticular changes
  - Colonic wall thickening
  - Inflammatory reaction in pericolic fat with ‘fat stranding’ and edema
  - Fluid tracks along root of mesentery
  - Abscess in 35% cases. <3 cm treated with antibiotics. 4 cm or more benefits from catheter drainage
Distinguishing diverticulitis from malignancy is difficult
- Long segment lesions favor inflammation rather than malignancy
Fistula often involves urinary bladder
- Conventional contrast enema may be used
- CT/MRI sufficient
- Air in urinary bladder, abscess in urinary bladder wall, bladder wall thickening or adherent adjacent colon may be seen
Giant cyst formation
- Rare complication
- Pseudocyst with no epithelial lining due to expansion of a walled-off subserosal perforation (Differential: duplication cyst)