Small intestine Flashcards
root of mesentery
starts from the duodenojejunal flexure, left to L2 vertebra and runs diagonally to the sacroiliac joint to the right
motor/parasympathetic/sympathetic supply of small intestine
motor and parasympathetic - vagus ( preganglionic synapse with the intrinsic neural plexus in the wall)
sympathetic - superior mesenteric ganglion ( T9/10)
difference between jejunum and ileum in
a) wall
b)valvulae conniventes
c) arterial arcades
d) percentage of smallbowel
a) thick – thin
b) large —-small
c) simple and long vessels —- multiple and short terminal vessels
d) 40%—-60%
Peters patches are present in ?
submucosa of small intestine and are more prominent in terminal ileum
the two nerve plexus in SI?
Meissners plexus present in the submucosa
myenteric plexus sandwiched between the outer longitudinal and inner circular muscle layers of muscularis propria
transverse folds in SI
valvulae conniventes / plica semilunari / valves of kecking
length of SI
3-10 metres
water secretion and output rate of small intestine
secretes approx 10L/ day
normal output -500ml /day
absorption of —— in small intestine
1) vitamin b12
2) folic acid
3) iron
1) terminal ileum – vitamin b12-intrinsic factor complex
2) jejunum
3) if reduced to fe+2 then absorbed in SI and then transported back to blood stream as fe+3
what happens after jejunal resection to water / folic acid absorption?
water reabsorption is reduced resulting in diarrhoea until ileum adapts to increase it absorptive capacity
but folic acid absorption may fail to recover and thus may have to be supplemented
what happens after resection of terminal ileum for more than 1 metre
1) vitamin b12 absorption is reduced and results in megaloblastic anaemia unless supplemented
2)absorption of bile salts is reduced resulting in malabsorption of fats and fat soluble vitamins and increased risk of gallstones
what is the anti-epileptic drug that inhibits the mucosal enzyme system and results in folic acid deficiency ?
EPANUTIN
choledochoduodenal fistula
between cystic duct/gb and duodenum resulting in gallstone ileus
factors that inhibit spontaneous healing of fistula
distal obstruction, persistent underlying disease, epithelisation of the fistula tract, presence of foreign body, malnutrition, loss of bowel continuity
management of fistulas SNAP
Sepsis - treat accordingly
Nutrition - oral intake to be reduced to reduce the output from fistulas, IVF should be encouraged and TPN is best given via central line– monitoring input and output and electrolytes
Anatomy- fistulography using contrast, barium studies, US, CT, injected dye and biochemistry of the output
Plan - conservative management likely to heal spontaneously
drugs used to reduce secretions
somatostatin, H2 receptor antagonists, PPI’s
benign tumours of small bowel
Peutz-jeghers hamartomas, adenoma, GI stromal tumour( GIST) — have malignant potential
lipoma, fibromas, schwannoma, lymphangiona, hemangioma, neurilemmomma
Primary malignant tumours of SI
duodenum - adenocarcinoma( 40%), carcinoid 25%, lymphoma and sarcoma
rest - carcinoid 31%, adenocarcinoma, lymphoma and sarcoma
Peutz-Jeghers syndrome
1) melanin spots around lips, buccal mucosa and sometimes face and extremities
2) numerous hamartomatous polyps throughout the bowel (more in jejunum and rest of small bowel)
HARAMARTOMA- abnormal growth of normal tissue
whipples procedure for ampullary tumours
resection of gallbladder, pylorus of stomach, duodenum, pancreas and anastomosis of gastrojejunostomy and pancreaticojejunostomy and choledochojejunostomy
gastrointestinal stromal tumours ( GIST)
- malignant potential/ spindle cell neoplasms— mostly in stomach and duodenum
- KIT-CD117 positive tumours
- asymptomatic as they grow extraluminal and not cause obstruction/ bleeding, perforation and invasion
- NICE treatment - IMATINIB treatment for unresectable tumours, else resection with cuff of normal tissue
CARCINOID tumours
- terminal ileum, appendix, rectum
- neuroendocrine tumours secreting neuroendocrine substances
- seretonin secretion causes intense desmoplastic reaction
CARCINOID SYNDROME
- if carcinoid tumours starts secreting vasoactive substances and mets to liver
- secretions such as serotonins
-metabolised in liver and excreted as 5 -Hydroxyindolacetic acid ( 5-HIAA)
-symptoms : flushing, diarhhoea, bronchospasm
-CT, enema, urinary 5-HIAA raised - <1cm - local excision
>2cm- small bowel resection and anastomosis with lymphatic clearance - palliative liver/bowel resection, chemo, subcutaneous octroetide
- excellent prognosis of early and no mets, 5 year survival is 30%
Lymphoma commonly associated with
coeliac disease and immune-compromised patients
peripheral lymphadenopathy , haematological abnormality and hepatosplenomegaly indicates that the lymphoma in smallbowel is ? Primary/secondary
SECONDARY
drug induced GI ulcers
potassium supplements, NSAIDs
risk of mesenteric angiography for GI bleeding
transmural ischemia and perforation , when used with embolisation or injection of vasoconstrictor
SMA embolic occlusion typically lodge at ?— sparing which part of small bowel ?
branch of middle colic artery - sparing jejunum( supplied by small jejunal arteries that branch proximal to middle colic artery)
