Module 2: GI: Intestinal Obstruction, Hirsch Disease, Diverticulosis, Pseudo, Amoebic and Ischemic Bowel

Question 1

Starting off intestinal obstruction is more common in small or large bowel?

Answer 1

Small bowel

Question 2

There are numerous causes for small bowel obstruction. What are the extramural/mechanical causes (most common)?

Answer 2

• -Peritoneal disease/adhesions from surgery – bands of adhesive tissue
• -Intussusception –telescoping of proximal bowel segment into distal
• -Volvulus: twisting of the bowel loop

Question 3

What are the luminal causes for small bowel obstructions?

Answer 3

Muconium ileus in infants with CF

Gallstone ileus: stone lodges in the terminal ileum often forms a cholecystoduodenal fistula

Question 4

What are the intramural (inside the wall) causes for small bowel obstruction?

Answer 4

Inflammatory conditions

• -Crohn’s
• -TB
• -Ischemic strictures
• -Radiation damage
• -Polypoid or infiltrative neoplasms

Question 5

Finally what are the pseudo-obstruction causes for small bowel obstruction?

Answer 5

Functional obstruction
Failure of propulsion
Paralytic ileus following peritoneal irritation (surgery)
–bowel not moving but nothing is really blocking it, something is wrong with the SM

Question 6

Now moving on to the large intestine. The first pathology to be discussed is Hirschsprung’s Disease. What is the presentation and what population is it found in?

Answer 6

Most common cause of congenital intestinal obstruction

• -delayed passage of meconium in newborn, constipation, abdominal distention
• -more common in males with down syndrome

Question 7

What is the pathogenesis for Hirschsprung’s Disease?

Answer 7

Defect in migration and survival of neuroblasts – congenital absence of ganglion cells in submucosal and myenteric plexus — functional obstruction — dilatation and hypertrophy proximal to affected segment (congenital megacolon)
–rectum is always affected

Question 8

What is the investigation for Hirschsprungs Disease and Complications?

Answer 8

Investigation: rectal biopsy with Calretinin stain

Complications; enterocolitis, perforation — peritonitis

Question 9

Moving on to another important topic in regards to large intestine pathology is Diverticulosis. What is diverticulosis, etiology and what part of the population do we see it in?

Answer 9

Population: common in Western World (50% of individuals over 60 years old) men
Diverticulosis: Acquired pseudo-diverticulum: involves mucosa and a small amount of submucosa (not the entire bowel wall)
Etiology: is idopathic but predisposing factors: elderly on a low fiber diet or long standing history of constipation
–associated with AD polycystic kidney disease!!!!

Question 10

What is the pathogenesis for Diverticulosis?

Answer 10

Decreased dietary fiber — sustained bowel contractions and increased intraluminal pressure — herniation of the colonic wall at sites of focal defects

Question 11

What is the presentation for a patient with Diverticulosis?

Answer 11

Asymptomatic

–incidental finding of colonoscopy

Question 12

What is the most common location for Diverticulosis?

Answer 12

Sigmoid colon (flask like structures) 
--hence why when it turns into diverticulitis there is LLQ pain.

Question 13

What are the complications of Diverticulosis?

Answer 13

1. Bleed – bright red blood in stool (hematochesia)
2. Fistula formation
   - -colonvaginal fistula
   - -enterocolonic fistula (small bowel and colon)
   - -colovesicle fistula (colon and bladder), patinet will have gas bubbles in urine called pneumoaturia and fecal matter in the urine, fecaluria, and this is why patients will get recurrent UTIs (E.coli)
3. Fecal impaction leads to acute diverticulitis
   - -LLQ pain , fever, WBCs elevated (neutrophils)
4. Diverticulitis abscess: collection of pus with SPIKING fevers
5. Never turns into cancer
6. Chronic diverticulitis: stricture formation and obstruction

Question 14

What are the complications associated with recurrent acute diverticulitis?

Answer 14

Turns into chronic inflammation forming fibrosis

–stricture formation which leads to intestinal obstruction to perforation to peritonitis to E. coil sepsis to DIC

Question 15

Moving on to the next large intestine pathology is pseudomembrane colitis. What is the etiology for this?

Answer 15

Gram Positive Clostridium Difficile (part of normal flora) after long standing broad spectrum abx use
–seen in hospitalized patients

Question 16

What is the pathogenesis for pseudomembrane colitis?

Answer 16

Exotoxin mediated:

• -denuded (Stripped) surface epithelium and superficially damaged crypts distended by macrophages exudate erupt forming a mushrooming cloud
• -they coalesce to produce pseudomembrane (fibrin, PMNs and necrotic debris)

Question 17

What is the most common location for pseudomembrane colitis?

Answer 17

Rectosigmoid colon

Question 18

How do patients present with pseudomembrane colitis?

Answer 18

Fever
Abdominal Pain
Massive Bloody Diarrhea
Mucoid (Secretory) diarrhea: lose potassium and albumin anytime you have this kind of diarrhea

Question 19

Describe the images of slide 12.

Answer 19

Gross: Yellow pseudomembrane on the colon
Histology: Huge pseudomembrane as the top layer of the mucosa (Which destroyed the surface epithelium and superficial crypts)

Question 20

What is the best investigations for pseudomembrane colitis?

Answer 20

Stool assay for exotoxin (gram positive)
CBC: high neutrophilia
Hypokalemia: mucoid diarrhea
Hypoalbuminemia: mucoid diarrhea

Question 21

What are the complications associated with pseudomembrane colitis?

Answer 21

1. Toxic Megacolon: damaged mucosa —- exposes the submucosa plexus called Meisner’s Plexus — leads to a lack of peristalsis — leads to back up of intestinal contents —- colon becomes toxic and big — and this can perforate —- peritonitis — sepsis —DIC
2. Bleeding can lead to hypovolemic shock —- leads to acute tubular necrosis (tubules are most sensitive to ischemia) — renal failure
3. Subendocardial MI from the hypovolemic shock
4. Hypokalemia —- cardiac arrhythmia’s
5. Hypokalemia —- nerve condition problems
6. Hypoalbuminemia — leads to peripheral edema due to losing oncotic pressure

Question 22

What is the treatment for pseudomembrane colitis?

Answer 22

Flagyl

Question 23

Why is a colonoscopy not the best investigation for pseudomembrane colitis?

Answer 23

You should never do a colonoscopy on a patient with colitis they can perforate

Question 24

The next colitis to mention is Amoebic Colitis. What is the etiology for this?

Answer 24

Parasitic infection with Entamoeba Histolytica acquired via fecal-oral route (ingesting the cyst)
–stem will say that patient has travel history to the tropics

Question 25

What is the pathogenesis for Amoebic Colitis?

Answer 25

Infection with cyst (4 nuclei) — transform to trophozoite (1 nucleus + RBC via erythrophagocytosis)

• -trophozoite form is damaging
• -cyst form in infective

Question 26

What do you see on histopathology in patients with Amoebic Colitis? (PIC13)

Answer 26

Flask Shaped Ulcer in the colon
-goes into the submucosa causing colitis
Pic to right shows the erythrophagocytosis (Trophozoites and RBC)

Question 27

How do patients with Amoebic Colitis present?

Answer 27

Fever 
Abdominal Pain 
Bloody Diarrhea 
Mucoid Diarrhea 
--very similar symptoms as pseudomembrane colitis except with this condition the stem will say travel

Question 28

What investigations are done for Amoebic Colitis?

Answer 28

Stool Assay for cyst/trophozoite: best investigation

4 nuclei in the cyst, 1 nucleus in the trophozoite (Erythrophagocytosis)

Question 29

What are the complications in Amoebic Colitis?

Answer 29

1. Perforation —- peritonitis —- sepsis —DIC
2. Organism travels from GI to the liver via the portal vein because the liver drains GI then to lung and brain all forming abscesses in the liver, lung and brain (know order)
   - —organism is atypical so we get PMNs and eosinophils

Question 30

Now moving onto Ischemic Bowel Disease. What is the etiology for this ?

Answer 30

Occlusive:
Volvulus, intussusception in children
Atherosclerotic plaques with superimposed thrombosis
Systemic Embolus from left mural thrombosis
–2months after an MI
PAN vasculitis (4th most common site): transmural
Hypercoaguable states (factor V laden, protein C and S deficiencies) –nephrotic syndromes
PNH (platelet dysfunction)
Non-occlusive:
Hypovolemic shock (mucosa is infected because it is the last place to get blood): most common cause
Dehydration
Cardiac Failure

Question 31

What is the presentation for ischemic bowel disease?

Answer 31

Decrease bowel sounds
Bloody diarrhea
Fever
Lower Abdominal Pain
–pain after eating due to decreased blood flow due to atherosclerosis
High WBCs (PNMS are elevated — neutrophilia)

Question 32

What investigations are done for ischemic bowel disease/

Answer 32

Angiogram — confirm —- surgical emergency for laparotomy
Biopsy: coagulative necrosis

Question 33

What are the complications for ischemic bowel disease?

Answer 33

Perforation — peritonitis — sepsis —DIC

Question 34

Finally lets touch on Chronic Ischemic Colitis. What is the pathogenesis?

Answer 34

Chronic Inflammation and fibrosis —- stricture formation or perforation

Question 35

What is the common site for chronic ischemic colitis? and what is the presentation?

Answer 35

Common at water shed areas: splenic flexure
Presentation: intermittent attacks of pain — intestinal angina
–can mimic IBD