Diverticular disease

Question 1

What is the incidence of diverticulosis? What proportion of those get diverticulitis? And complicated diverticulitis?

Answer 1

Diverticulosis in <20% by 40, 60% by age 60

Increasing incidence

86% of Western diverticulosis is left-sided (and same for symptomatic disease); 40% of Asians >60yrs have right-sided

Diverticulitis occurs in 4-15% of those with diverticulosis

25% of those with diverticulitis have complicated diverticular disease - abscess (15%), stricture (105%), fistula (<5%), perforation (1.5%)

Question 2

What is the aetiology and pathophysiology of diverticular disease?

Answer 2

• predominantly a disease of industrialised societies assoc w ageing population & Western diet; genetic factors may play a role, in addition to geographical location and lifestyle factors (smoking & obesity)
• diverticula develop at four well-defined points around the circumference of the colon, the sites at which the vasa recta penetrate the circular muscle layer
  
  • these vessels enter the wall on each side of the mesenteric taeniae and on the mesneteric border of the two antimesenteric taenia
  • this results in protrusion of the mucosa and submucosa through the layers of the muscle - termed a pseudo/false diverticulum
• several theories about pathogenesis; potential aetiological factors include:
  
  • luminal trauma
  • compromised colon wall integrity
  • increased colonic pressures/disordered motility
  • altered bacterial flora
• changes in structure & composition of colonic tissue
  
  • compared to normal colons, pts w diverticular disease have thickened circular muscle, shortened taenia & narrowing of lumen
  • the thickened circular muscle is from increased elastin deposition; also greater rates of collagen cross-linking - may cause tissues to become stiffer –> loss in compliance of submucosa, making it more susceptible to injury
  • collagen cross-linking increases w age (more common in older pts) and changes to collagen cross-linking and elastin deposition may also explain why pts w connective tissue disorders are more prone to diverticulosis earlier in life
• pts w diverticulosis also have higher intraluminal pressures in sigmoid vs controls; can lead to increased risk of injury to mucosa
  
  • in high fibre diet, motility faster & intraluminal pressures lower - may explain why a high fibre diet is protective against diverticular disease
• more recent studies suggest other potential contributing factors incl chronic inflammation, gut microbiome & genetics
• diverticulitis results from micro or macro-perforation of a colonic diverticulum
  
  • primary process now thought to be erosion of diverticular wall by increased intraluminal pressure or inspissated food particles (as opposed to obstruction of a diverticulum by a faecolith)
  • leads to inflammation and focal necrosis –> micro/macroperforation
  • leads to pericolonic inflammation as there is extravasation of faeculant fluid
  • inflammation frequently mild & walled off by pericolic fat and mesentery –> may lead to localised abscess or, if adjacent organs are involved, a fistula or obstruction
  • poor containment of inflamed diverticulum or abscess –> free perforation or peritonitis
• bleeding: as diverticulum herniates, the penetrating vessel responsible for the wall weakness at that point becomes draped over the diverticulum, separated from the lumen only by mucosa
  
  • over time, the vasa recta is exposed to injuyr along its luminal aspect -> segmental weakening of artery, predisposing to rupture into lumen

Question 3

What is the modified Hinchey criteria and what is its use?

Answer 3

• 0 = mild clinical diverticulitis
• Ia = colonic wall thickening/confined pericolic inflammation
• Ib = confined small (<5cm) pericolic abscess
• II = pelvic, distant intra-abdo ro retroperitoneal abscess
• III = generalised purulent peritonitis
• IV = generalised faeculant peritonitis

Correlate with postop morbidity and mortality and are also predictive of recurrence when managed nonoperatively, but limited bc presence of faeculant peritonitis can only be determined at time of surgery

Question 4

What is the radiological classification of acute diverticulitis?

Answer 4

Ambrosetti

• Moderate diverticulitis
  
  • localised sigmoid colon diverticulitis (wall >5mm)
  • inflammation localised to pericolic fat
• Severe diverticulitis
  
  • moderate diverticulitis and any of
    
    • abdominopelvic abscess
    • extraluminal gas
    • extraluminal contrast extravasation