GI: Small Bowel Flashcards

1
Q

what is duodenal atresia

A

congenital failure of duodenum to canalize

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2
Q

duodenal atresia is associated with what congenital disorder

A

Trisomy 21

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3
Q

what are 3 clinical features of duodenal atresia

A
  1. polyhydramnios
  2. distension of stomach and blind loop of duodenum (‘double bubble’ sign)
  3. bilious vomiting
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4
Q

What is Mechel Diverticulum

A

outpouching of all 3 layers of the

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5
Q

What causes Meckel diverticulum

A

failure of vitelline duct to involute

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6
Q

what is the ‘rule of 2s’

A

Meckel Diverticulum

  • 2% population
  • 2 inches long and located in small bowel within 2 feet of the ileocecal valve
  • present during 2 years of life with bleeding ( heterotopic gastric mucosa), volvulus, intussusception, or obstruction (mimics appendicitis)

MOST CASES ARES ASYMPTOMATIC

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7
Q

what is the most common congenital anomaly of the GI tract

A

Meckel Diverticulum

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8
Q

what is volvulus

A

twisting of bowel along its mesentery

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9
Q

Volvulus causes what

A

obstruction and disruption of blood supply with infarction

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10
Q

what is the most common location of volvulus

A
sigmoid colon ( elderly)
cecum ( young adults)
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11
Q

What is intussusception

A

telescoping of proximal segment of bowel forward into distal segment

  • telescoped segment is pulled forward by peristalsis, resulting in obstruction and disruption of blood supply with infarction
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12
Q

What is the most common cause of intussusception in children?

A

lymphoid hyperplasia (e.g., due to rotavirus)

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13
Q

What is the most common cause of intussusception in adults?

A

tumor

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14
Q

What is small bowel infaraction

A

small bowel is highly susceptible to ischemic injury

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15
Q

What are clinical features of small bowel infarction

A

abdominal pain
bloody diarrhea
decreased bowel sounds

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16
Q

when causes transmural infarction to occur in small bowel infarction

A

thrombosis/embolism of superior mesenteric artery or thrombosis of mesenteric vein

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17
Q

when causes mucosal infarction to occur in small bowel infarction

A

marked hypotension

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18
Q

what is lactose intolerance

A

decreased function of lactase enzyme found in brush border of enterocytes

19
Q

role of lactase

A

normally breaks down lactose into glucose and galactose

20
Q

clinical presentation for lactose intolerance

A

abdominal distension and diarrhea upon consumption of milk

- undigested lactose is osmotically active

21
Q

when do people become lactose intolerance

A
  1. congenital ( rare autosomal recessive disorder)
  2. acquired ( develops late childhood)
  3. temporary ( after small bowel infection- lactase is highly susceptible to injury )
22
Q

what is celiac disease

A

immune-mediated damage of small bowel villi due to gluten exposure
HLA-DQ2 and DQ8

23
Q

what is gluten present in and what is the pathogenic component

A

wheat and grains

gliadin

24
Q

how is gliadin a pathogenic component

A
  1. absorbed, gliadin is deamidated by tissue transglutaminase (tTG)
  2. deamidated gliadin is presented by MHC class II
  3. helper T cells mediate tissue damage
25
children clinical presentation for celiac disease
abdominal distension diarrhea failure to thrive
26
adult clinical presentation for celiac disease
chronic diarrhea and bloating
27
how is the skin impacted with celiac disease
dermatitis herpetiformis : small, herpes-like vesicles on skin - due to IgA deposition at tips of dermal papillae
28
what is a laboratory finding for celiac disease
- IgA antibodies against endomysium, tTG, or gliadin | - IgG abs present, useful for diagnosis in individuals with IgA deficiency
29
what is seen in duodenal biopsy in celiac disease
flattening of villi, hyperplasia of crypts, and increased intraepithelial lymphocytes - damage more prominent in duodenum; jejunum and ileum are less involved
30
What are late complications of celiac disease even with good diet restriction
small bowel carcinoma and T-cell lymphoma
31
What is tropical sprue
damage to small bowel villi due to an unknown organism resulting in malabsorption
32
what is the difference b/w tropical sprue and celiac disease
Tropical sprue has 1. occurs in tropical regions ( caribbean) 2. arises after infectious diarrhea and responds to antibiotics 3. damage is prominent in jejunum and ileum ( secondary vitamin B12 or folate deficiency may ensue)
33
What is whipple disease
- systemic tissue damage characterized by macrophages loaded with Tropheryma whippelii organisms - partially destroyed organisms are present in macrophage lysosomes ( positive for PAS)
34
where does Whipple disease occur
small bowel lamina propria (common) - synovium of joints ( arthritis) - cardiac valves - lymph nodes - CNS
35
what is the pathogenesis of Whipple disease
1. macrophages compress lacteals 2. chylomicrons cannot be transferred from enterocytes to lymphatics 3. results in fat malabsorption and steatorrhea
36
What is abetalipoproteinemia
autosomal recessive deficiency of apolipoprotein B-48 and B-100
37
clinical features of abetalipoproteinemia
1. malabsorption - due to defective chylomicron formation ( requires B-48) 2. Absent plasma VLDL and LDL ( require B-100)
38
What is carcinoid tumor
malignant proliferation of neuroendocrine cells | low grade malignancy
39
carcinoid tumor cells contain what
neurosecretory granules that are positive for chromogranin
40
where does carcinoid tumor most likely occur
- small bowel most commonly ( submucosal polyp-like nodule) | - arise anywhere along gut
41
What do carcinoid tumor secrete
serotonin | - released into portal circulation and metabolized by liver monoamine oxidase (MAO) into 5-HIAA--> excreted in urine
42
What is special about metastasis of carcinoid tumor to liver
serotonin bypass liver metabolism | - serotonin is released into hepatic vein, leaks into systemic circulation via hepato-systemic shunts
43
metastasis of carcinoid tumor to liver can result in what other disease
Carcinoid syndrome and carcinoid heart disease