GI: Small Bowel Flashcards
what is duodenal atresia
congenital failure of duodenum to canalize
duodenal atresia is associated with what congenital disorder
Trisomy 21
what are 3 clinical features of duodenal atresia
- polyhydramnios
- distension of stomach and blind loop of duodenum (‘double bubble’ sign)
- bilious vomiting
What is Mechel Diverticulum
outpouching of all 3 layers of the
What causes Meckel diverticulum
failure of vitelline duct to involute
what is the ‘rule of 2s’
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
what is the most common congenital anomaly of the GI tract
Meckel Diverticulum
what is volvulus
twisting of bowel along its mesentery
Volvulus causes what
obstruction and disruption of blood supply with infarction
what is the most common location of volvulus
sigmoid colon ( elderly) cecum ( young adults)
What is intussusception
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
What is the most common cause of intussusception in children?
lymphoid hyperplasia (e.g., due to rotavirus)
What is the most common cause of intussusception in adults?
tumor
What is small bowel infaraction
small bowel is highly susceptible to ischemic injury
What are clinical features of small bowel infarction
abdominal pain
bloody diarrhea
decreased bowel sounds
when causes transmural infarction to occur in small bowel infarction
thrombosis/embolism of superior mesenteric artery or thrombosis of mesenteric vein
when causes mucosal infarction to occur in small bowel infarction
marked hypotension
what is lactose intolerance
decreased function of lactase enzyme found in brush border of enterocytes
role of lactase
normally breaks down lactose into glucose and galactose
clinical presentation for lactose intolerance
abdominal distension and diarrhea upon consumption of milk
- undigested lactose is osmotically active
when do people become lactose intolerance
- congenital ( rare autosomal recessive disorder)
- acquired ( develops late childhood)
- temporary ( after small bowel infection- lactase is highly susceptible to injury )
what is celiac disease
immune-mediated damage of small bowel villi due to gluten exposure
HLA-DQ2 and DQ8
what is gluten present in and what is the pathogenic component
wheat and grains
gliadin
how is gliadin a pathogenic component
- absorbed, gliadin is deamidated by tissue transglutaminase (tTG)
- deamidated gliadin is presented by MHC class II
- helper T cells mediate tissue damage
children clinical presentation for celiac disease
abdominal distension
diarrhea
failure to thrive
adult clinical presentation for celiac disease
chronic diarrhea and bloating
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
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
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
What are late complications of celiac disease even with good diet restriction
small bowel carcinoma and T-cell lymphoma
What is tropical sprue
damage to small bowel villi due to an unknown organism resulting in malabsorption
what is the difference b/w tropical sprue and celiac disease
Tropical sprue has
- occurs in tropical regions ( caribbean)
- arises after infectious diarrhea and responds to antibiotics
- damage is prominent in jejunum and ileum ( secondary vitamin B12 or folate deficiency may ensue)
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)
where does Whipple disease occur
small bowel lamina propria (common)
- synovium of joints ( arthritis)
- cardiac valves
- lymph nodes
- CNS
what is the pathogenesis of Whipple disease
- macrophages compress lacteals
- chylomicrons cannot be transferred from enterocytes to lymphatics
- results in fat malabsorption and steatorrhea
What is abetalipoproteinemia
autosomal recessive deficiency of apolipoprotein B-48 and B-100
clinical features of abetalipoproteinemia
- malabsorption - due to defective chylomicron formation ( requires B-48)
- Absent plasma VLDL and LDL ( require B-100)
What is carcinoid tumor
malignant proliferation of neuroendocrine cells
low grade malignancy
carcinoid tumor cells contain what
neurosecretory granules that are positive for chromogranin
where does carcinoid tumor most likely occur
- small bowel most commonly ( submucosal polyp-like nodule)
- arise anywhere along gut
What do carcinoid tumor secrete
serotonin
- released into portal circulation and metabolized by liver monoamine oxidase (MAO) into 5-HIAA–> excreted in urine
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
metastasis of carcinoid tumor to liver can result in what other disease
Carcinoid syndrome and carcinoid heart disease
