Irritable Bowel Syndrome/Diverticulitis

Question 1

IBS

Answer 1

Defined by Rome III: recurrent abdominal pain/discomfort + improvement with defecation + onset associated with change in frequency and form of stool 3x/month

Question 2

4 categories of IBS

Answer 2

irritable bowel + consitpation, irritable bowel + diarrhea, irritable bowel + mixed, unclassified

Question 3

IBS epi

Answer 3

females>males, 5-20% in developed countries –> most commonly diagnosed GI condition

Question 4

Why is IBS important?

Answer 4

no decrease in life expectancy but reduced QOL and high cost of health-care utilization/work absenteeism

Question 5

Etiology of IBS

Answer 5

mixed: motility, visceral sensitivity, genetic, fecal flora, inflammation, food, psychosocial

Question 6

What is the neuronal cause of visceral hypersensitivity?

Answer 6

excessive/prolonged excitation of afferent pathways resulting in neuronal sensitization anywhere in the neuronal pathway –> CNS dysregulation + abnormal stimulus increases perception of symptoms in IBS

Question 7

What antibiotic can improve IBS without constipation

Answer 7

Rifaximin –> alters microbiome, thus changing IBS

Question 8

What is post-infectious IBS?

Answer 8

increased risk of IBS after infections

Question 9

What is SIBO?

Answer 9

small intestinal bacterial overgrowth –> fermentation –> tx of SIBO reduces IBS

Question 10

In IBS-D, ___ is produced. In IBS-C, ___ is also produced.

Answer 10

hydrogen and methane

Question 11

T/F Fiber can increase IBS symptoms

Answer 11

F–> tx for IBS as long as not fermentable or doesn’t breakdown into SFCA –> can increase motility

Question 12

How do lipids cause IBS symptoms?

Answer 12

increase motility and sensitivity

Question 13

T/F Gluten can cause symptoms in IBS patients with celiac disease?

Answer 13

T

Question 14

Intestinal inflammation w/mast cells and lymphocytes are common in some patients with _____.

Answer 14

IBS-D and postinfectious IBS

Question 15

How does intestinal inflammation cause mucosal permeability leading to IBS?

Answer 15

inflammation releases mediators that change tight junction proteins leading to outflow of antigens across intestinal wall –> increased activation of immunocytes + increased sensitivity and motility

Question 16

Which genes are connected to IBS?

Answer 16

TNFS and IBS + TLR9 and post-infectious IBS, bile acid synthesis KLB and IBS-D, some neurotransmitters and cytokines, guanylate cycle C and obvi HLA DQ2/8

Question 17

T/F early adverse life events can lead to IBS

Answer 17

T due to sustained neurological dysfunction

Question 18

T/F IBS patients tend to have more anxiety, depression, phobia, somatization

Answer 18

T

Question 19

What is a diverticulum?

Answer 19

sac like protrusion of colonic wall

Question 20

What is diverticulosis?

Answer 20

you’ve got diverticulas

Question 21

A typical colonic diverticulum is true/false

Answer 21

false –> does not have all layers of wall, just mucosa

Question 22

Congenital diverticuli are true/false

Answer 22

true –> have all layers

Question 23

What are the usual symptoms of diverticulosis?

Answer 23

usually asymptomatic

Question 24

Main colonoscopic finding in US?

Answer 24

diverticula!

Question 25

Western nations have left/right sided diverticuli

Answer 25

left --> acquired

Question 26

Asian nations have right/left sided diverticuli

Answer 26

right --> congenital

Question 27

Where do most patients have diverticulosis?

Answer 27

descending and sigmoid colon --> but uneven distribution in colon

Question 28

Etiology of diverticulosis

Answer 28

anatomic weakness, low fiber, nt's, increased intraluminal pressure, disordered motility

Question 29

Point of anatomic weakness in bowel wall

Answer 29

points at which vasa recta penetrate circular muscle layer

Question 30

Law of Laplace

Answer 30

p = kt/R | P = pressure, K = conversion factor, T = wall tension, R = bowel radius

Question 31

Why is the sigmoid colon common for diverticulosis?

Answer 31

small radius = higher pressure a la laplace --> risk factor

Question 32

____ muscle reduces functional length of colon

Answer 32

longitudinal

Question 33

____ muscle controls peristalsis

Answer 33

circular

Question 34

What happens to muscle in diverticulosis?

Answer 34

increased elastin deposition --> thickened taenia coli = highly contractile normal muscle + thickened circular muscle = luminal narrowing --> bowel division into segments/compartments + increased collage deposition --> increased rigidity --> decreased compliance/accommodation to increased pressure

Question 35

What collagen is deposited in diverticulosis?

Answer 35

collagen III due to MMP and inhibitor imbalance especially with age

Question 36

T/F segmentation is exaggerated in diverticulosis

Answer 36

T --> outpouchings of colon cause diverticula formation

Question 37

How does disordered colonic motility manifest in diverticulosis?

Answer 37

increased smooth muscle with age --> increase in segmental contraction + lower # of cajal cells = disordered contraction

Question 38

What NT changes occur in diverticulosis?

Answer 38

increased excitatory: serotonin + ACh decreased inhibitory: NO, VIP = increased motility and pressure

Question 39

3 factors in developing symptoms in diverticular disease

Answer 39

1. diet (low fiber, high fat/meat) 2. low physical activity 3. obesity

Question 40

Symptomatic diverticular disease

Answer 40

inflamed diverticulum, segmental colitis (SCAD), symptomatic uncomplicated diverticular disease (SUDD

Question 41

Persistent GI symptoms from DD w/o overt macroscopic colitis or diverticulitis.

Answer 41

SUDD --> e.g. fecal stasis leads to abnormal metabolites and chronic inflammation

Question 42

Pathophysiology of diverticulitis

Answer 42

erosion of diverticular wall --> inflammation --> focal necrosis --> perforation perforations: 1. contained = obstruction or fistula 2. not contained = peritonitis

Question 43

T/F DD can overlap with IBS

Answer 43

T --> similar constellation of causes and DD can lead to IBD in 10% of cases

Question 44

T/F there can be visceral hypersensitivity in DD

Answer 44

T --> post inflammatory increases neuropeptides and alterations in enteric innervation

Question 45

How does diverticular bleeding occur?

Answer 45

blood vessel exposed in luminal injury --> eccentric intimal thickening and thinning of media --> segmental artery weakness --> rupture into lumen