Path of the Lower GI Tract -Mesa

Question 1

What is the blood supply to the small intestine (other than the duodenum)?

Answer 1

SMA

Question 2

What supplies the duodenum?

Answer 2

pancreaticoduodenal A from the Celiac A

Question 3

What supplies the colon from the cecum to the splenic flexure? Splenic flexure to the rectum?

Answer 3

• cecum to the splenic flexure: SMA

- Splenic flexure to the rectum: IMA

Question 4

Which areas of the colon are susceptible to ischemia?

Answer 4

Watershed areas (Marginal A) and the distal sigmoid (pudendal and superior rectal AA)

Question 5

Where are rings of kerckring (plicae) found?

Answer 5

small intestine

Question 6

What are the 4 layers of the small intestine?

Answer 6

• Mucosa: epithelium, lamina propria, muscularis mucosa
• Submucosa: loose connective tissue, Meissner’s plexus
• Muscularis Propria: inner circ., outer long.
• Serosa: fibroelastic tissue, mesothelium

Question 7

Where are the Brunner’s glands found?

Answer 7

duodenal mucosa only

Question 8

What is the Rule of 2’s associated with Meckel’s diverticulum?

Answer 8

2 inches long, 2 feet from ileocecal valve, 2 times as common in males than females, 2% of population, 2% symptomatic, 2 types of ectopic tissue: gastric and pancreatic

Question 9

What is Hirschsprung Disease?

Answer 9

• aganglionic megacolon
• failure of neural crest cells to migrate tot he colon –> lack of parasympathetic ganglionic cells –> functional obstruction and colonic dilation proximal to affected segment (can get toxic mega colon)

-plain film radiograph may reveal marked colonic dilation proximal to effected bowel segment

Question 10

What is the most common cause of bowel obstruction?

Answer 10

Adhesions (due to previous surgeries)

Question 11

What segment of the colon is most susceptible to volvulus?

Answer 11

Sigmoid colon

Question 12

What are the 2 types of causes of ischemia/infarction?

Answer 12

• non-occlusive (hypoperfusion–> shock, drugs, marathon runner)
• occlusive (arterial/venous thrombus or embolism, iatrogenic)

Question 13

What are the most frequent predisposing factors of hemorrhoids?

Answer 13

• strained defecation and pregnancy

- other: portal HTN and neoplasms

Question 14

How does dysentery differ from diarrhea?

Answer 14

• dysentery is low volume, painful, bloody diarrhea

- diarrhea=inc in stool mass, frequency or fluidity (>3 + loose stool/day)

Question 15

What are the characteristics of secretory diarrhea? What are the causes of secretory diarrhea?

Answer 15

->500mL/day, isotonic, persistent with fasting

• Viral damage to mucosa (Rotavirus, Norovirus, Adenovirus)
• Enterotoxins, bacterial (V. cholera, E. coli, B. cereus, C. perfringens)
• Neoplasms secreting GI hormones
• Excessive laxatives

Question 16

What are the potential causes of osmotic diarrhea? How does it respond to fasting?

Answer 16

• Increased stool osmolality
• Disaccaridase (lactase) deficiency
• Bowel preps
• Antacids, egs., MgS04

-Abates with fasting

Question 17

What are the characteristics of exudative diarrhea? What causes it?

Answer 17

-purulent bloody stools, persists with fasting

• Bacterial damage to GI mucosa (Shigella, Salmonella, C. jejuni, E. histolytica)
• IBD
• Typhilitis (Caecitis, immunosuppression colitis), chemo, AIDS, kidney transplant

Question 18

What are the most common causes of malabsorption diarrhea? Where can the disturbances take place?

Answer 18

• celiac sprue
• Pancreatic insufficiency
• Crohn’s

disturbances:

• Intraluminal digestion
• Terminal digestion
• Transepithelial transport
• Lymphatic transport

Question 19

What is Celiac Disease? What HLA is associated with it?

Answer 19

sensitivity ot gluten–> perpetual inflammation and progressive mucosal atrophy and villous flattening

HLA-DQ2 and DQ8

Question 20

What is the most common disaccaridase deficiency? What are the different types?

Answer 20

• Lactase*

- types: congenital (rare, mutation for lactase gene) and acquired (down regulation of lactase gene expression)

Question 21

What is Abetalipoproteinemia?

Answer 21

• mutation in MTtP gene –> inability to make chylomicrons from FFAs and monoglycerides
• deficiencies in Vit A, D, E, K
• acanthocytes (Burr cells) because can’t make cell membranes

Question 22

What are the 3 ways you can get bacterial enterocolitis?

Answer 22

• ingestion of bacterial toxins (staph, vibrio, clostridium)
• ingestion of bacteria which produce toxins (traveller’s diarrhea, E. coli)
• Infections by enteroinvasive bacteria (EIEC, shigella, C. diff)

Question 23

Which pathogen can cause dysentery with a low inoculum and i passed person to person?

Answer 23

Shigellosis (salmonella is not bloody)

Question 24

What are the different types of E. coli and how do they affect people?

Answer 24

• Enterotoxigenic: traveller’s diarrhea, non-invasive, toxins
• Enterohemorrhagic: O157:H7, non-invasive and toxins
• Enteroinvasive: invasion of epithelium and NO toxins
• enteroaggregative: adhere to brush border and produces toxins

Question 25

What is Whipple’s Disease? What will happen if it is not treated with antibiotics?

Answer 25

• Rare infection, Tropheryma whippelii, gram + intracellular actinomyces
• Organism-laden macrophages in lamina propria and LNs cause lymphatic obstruction

*fatal without antibiotics

Question 26

What is the most common cause of gastroenteritis in infants/children worldwide?

Answer 26

Rotavirus

2nd: adenovirus

Question 27

In which IBD are there granulomas in the mucosa?

Answer 27

Crohn’s Disease

Question 28

Which IBD can lead to malabsorption?

Answer 28

Crohn’s

Question 29

Which IBD can cause pseudo polyps?

Answer 29

Ulcerative colitis (UC)

Question 30

What is needed for confirmation of acute appendicitis?

Answer 30

Need neutrophils in muscularis for confirmation of diagnosis