10.5 Small Bowel Flashcards
Congenital failure of duodenum to reanalyze; associated with Down syndrome
Duodenal atresis
3 clinical features of duodenal atresia
- polyhydramnios
- distention of stomach and blind loop of duodenum (double bubble sign)
- bilious vomiting
Outpouching of all three layers of the bowel wall (true diverticulum)
Meckel diverticulum
what causes meckel diverticulum?
failure of the vitelline (omphalomesenteric) duct to involute
4 rules of 2s for Meckel
2% of pop,
2 inches long,
within 2 ft of ileocecal valve,
can present w/i first 2 years
4 potential presentations of Meckel
- bleeding
- volvulus
- intussusception
- obstruction
what causes bleeding in meckel?
heterotopic gastric mucosa
twisting of bowel along its mesentery; results in obstruction and disruption of blood supply with infarction
volvulus
most common location of volvulus in elderly
sigmoid colon
most common location of volvulus in young adults
cecum
telescoping of proximal segment of bowel forward into distal segment
intussusception
in kids, most common cause of intussusception
lymphoid hyperplasia (e.g. due to rotavirus)
in kids, most common location of intussusception
terminal ileum (–>I in cecum)
in adults, most common cause of intussusception
tumor
abdominal pain + bloody diarrhea + decreased bowel sounds
small bowel infarction
three causes of small bowel infarction
- Thrombosis of SMA
- Embolism of SMA
- Thrombosis of mesenteric vein
decreased function of the lactase enzyme found in the brush border of enterocytes
lactose intolerance
normal function of lactase
lactose –> glucose + galactase
presents with abdominal dissension and diarrhea upon consumption of milk products; undigested lactose is osmotically active
lactose intolerance
Lactose intolerance on LM?
totally normal intestinal mucosa
immune-mediated damage of small bowel villi due to gluten exposure; associated with HLA-DQ2 and DQ8
Celiac disease
most pathogenic component of gluten
gliadin
once absorbed gliadin is deamidated by
tissue transglutaminase (tTG)
deamidated gliadin is presented by APCs via
MHC class II
damage in celiac mediated by
helper T cells (CD4+)
presentation of celiac in a child
abdominal distension, diarrhea, failure to thrive
presentation of celiac in an adult
chronic diarrhea and bloating, maybe dermatitis herpetiformis
what causes dermatitis herpetiformis
IgA deposition at the tips of dermal papillae
Lab findings in celiac
IgA antibodies against endomysium, tTG, or gliadin; also IgG
How would you diagnose celiac in someone with IgA deficiency (inc. incidence of this in celiac)?
IgG
duodenal biospy in celiac
flattening of villi + hypertrophy of crypts + inc. intraepithelial lymphocytes
where is damage most prominent in celiac?
duodenum (jejunum and ileum are less involved)
late complications of celiac that present as refractory dz despite good dietary control
small bowel carcinoma, T-cell lymphoma
damage to small bowel villi due to an unknown organism resulting in malabsoption
tropic sprue
unlike celiac, tropical sprue has the following characteristics
- tropical regions
- arises after infectious diarrhea
- gets better w. antibiotics
- damage most prominent in jejunum or ileum
where is damage most prominent in tropical sprue
jejunum and ileum (duodenum less commonly involved)
tropical sprue may lead to what deficiencies
vitamin B12 or foalate
systemic tissue damage characterized by macrophages loaded with Tropheryma whippelii organisms; PAS+
Whipple dx
where are the partially destroyed organisms in Whipple dz?
Macrophage lysosomes (PAS+)
common site of involvement in whipple?
small bowel lamina propria
macrophages compress what in whipple?
lacteals
macrophage compresses lacteals, so chylomicrons cannot be transferred from enterocytes to
lymphatics
whipple presents as
fat malabsorption and steatorrhea
4 whipple sites o/s small bowel
- synovium of joints (arthritis)
- cardiac valves
- lymph nodes
- CNS
AR deficiency of ApoB48 and ApoB100
abetalipoproteinemia
AR deficiency of ApoB48 and ApoB100 due to mutation in
MTP gene
abetalipo presents with malabsorption due to
defective chylomicron formation (requires B46)
abetalipo p/w absent plasma VLDL and LDL b/c
requires B100
malignant proliferation of neuroendocrine cells anywhere along gut; low-grade malignancy; chromogranin +;
carcinoid tumor
most common site of carcinoid
submucosal polyp-like nodule in small bowel
carcinoid may secrete serotonin –> portal circ. –> metabolized by
liver MAO into 5HIAA
liver MAO metabolizes serotonin to
5HIAA
what metabolite in the urine indicates carcinoid?
5HIAA
how could serotonin bypass liver metabolism in carcinoid?
met to liver
carcinoid met to liver releases serotonin into hepatic vein –>
hepato-systemic shunts –> systemic circulation
three symptoms of carcinoid
bronchospasm + diarrhea + flushing
carcinoid symptoms can be triggered by
alcohol or emotional stress
carcinoid heart disease is characterized by increased collagen where?
RIGHT HEART (TIPS)
why is carcinoid HD not seen in left heart
MAO in lung
