Diverticular disease Flashcards
What is diverticular disease?
- common condition in which many diverticula develop in the large bowel
- almost always in the sigmoid colon
- incidence rises with increasing age
- particularly common in western world, occurring in 50% of ppl 60+
What is a diverticulum?
- plural: diverticula
- a pouch of colonic mucosa that has herniated through the muscularis propria
- and has come to lie in the subserosal (pericolic) fat outside the bowel wall
- note the outer wall of diverticula is supported only by a thin layer of subserosal connective tissue
- so diverticula are prone to perforation when they are obstructed and/or inflammed
What are the 2 factors important for diverticula formation?
-
areas of weakness in the colonic wall:
- there are natural defects in the circular muscle layer where blood vessels pass through to supply the submucosa and mucosa
-
raised intraluminal pressure due to insufficient dietary fibre:
- fibre binds salt and water in the colon resulting in bulky, moist faeces that are easily propelled through colon
- movement of faeces from a low fibre diet along colon requires increased muscular effort which results in muscular hypertrophy and inc intraluminal pressure. As a consequence, diverticula are more likely to form
What is the most common site for diverticula formation and why?
- sigmoid colon
- has the smallest diameter of any portion of large bowel
- therefore site where intraluminal pressure highest
What is the difference between diverticulosis and diverticulitis?
- osis = diverticula are present but asymptomatic
- itis = an acutely inflammed diverticulum, the most common presentaton
So how is acute diverticulitis initiated (pathophys)?
- when faecal matter impacts and obstructs neck of diverticulum
- this leads to trapping of bacteria
- consequent bacterial replication in occluded lumen
- -> infection and mucosal injury
- local trauma (‘rubbing’) to mucosa by faecolith may also cause mucosal injury
- mucosal injury initiates an acute inflammatory response, resulting in acute diverticulitis
What are the clinical features of acute diverticulitis?
- abdominal pain (usually LIF)
- malaise
- fever
- localised tenderness
- no peritonisim
How does an abscess form from acute diverticulitis? What is an abscess?
- an abscess is a localised collection of pus within a newly-formed cavity in the tissue
- acute inflammatory response process may extend beyond diverticulum into surrounding subserosal tissue -> formation of a pericolic abscess
- the cavity forms bc of breakdown and destruction of body’s tissue
- pus consists of inflammatory cells (mainly neutrophils) admixed w/ cellular debris, fbirin and oedema fluid
What can the pericolic abscess lead to?
- pericolic abscess may perforate into the abdominal cavity
- resulting in bacerial peritonitis
- alternatively, an inflamed diverticulum may perforate directly into the abdominal cavity, also resulting in faecal peritonitis
- inflamed diverticula are particularly prone to perforate bc the wall of the diverticulum is supported only by a thin layer of subserosal tissue
Why might a fistula form from diverticulitis?
- rarlely, as a consequence of inflammation
- fistula is an abnormal connection between two epithelial surfaces
- fistula may form between sigmoid colon and bladder
- this presents clinically as faecaluria (passing faecal matter in urine)
- fistulae may also form to the vagina
Why might a stricture form as a consequence of diverticular disease?
because of:
- smooth muscle hypertrophy and hyperplasia due to low fibre diet
- fibrosis around diverticula (repeated episodes of inflammation heal by fibrosis)
both of these factors lead to a reduction in the diameter of the lumen ie. a stricture - they present with clinical features of bowel obstruction
What important GI symptom is diverticular disease a common cause of?
- lower GI bleeding
- the small blood vessels are stretched over dome of diverticula
- can rupture causing bleeding
- bleeding from diverticula is typically painless and spontaneous
- in most cases blood loss from diverticula is small
- occasionally it may be massive
What other disease may diverticular disease also mimic and how do we rule this out?
- may clinically closely mimic colorectal cancer
- intermittent abdo pain + altered bowel habit
- both conditions affect broadly similar age groups
- positive FOB and iron deficiency anaemia (due to ongoing bleeding from diverticula)
‘Diverticular’ strictures should be biopsied to rule out colon carcinoma
What is the management of diverticulitis?
- mild attacks treated w/ oral Abx
- more significant episodes managed in hospital
- pts are made NBM, IV fluids + IV Abx (a cephalosporin + metronidazole) given
What investigations can be done for diverticulitis?
- FBC → raised WCC
- CRP → raised
- Erect CXR → may show pneumopertioneum (perforation)
- AXR → dilated bowel loops, obstruction or abscesses
- CT → best modality for suspected abscesses
- Colonoscopy → avoided initially due to inc risk of perforation in diverticulitis
