GIT

Question 1

Normal gastrointestinal embryology

Answer 1

Foregut- esophagus to duodenum at level of pancreatic duct and common bile duct insertion (ampulla of VATER)

Midgut- lower duodenum to proximal 2/3 of transverse colon

Hindgut- distal 1/3 of transverse colon to anal canal above pectinate line

Midgut development: 6th week - physiologic herniation of midgut through umbilical ring, 10th week returns to abdominal cavity and rotates around SMA, total 270’ counterclockwise

Question 2

Ventral wall defect

Answer 2

development defects due to failure of rostral fold closure (sternal defects (ectopia cordis), Lateral fold closure (omphalocele, gastroschisis), or caudal fold closure- bladder extrophy

Question 3

Gastroschisis

Answer 3

Extrusion of abdominal contents through abdominal folds (typically right of umbilicus)

Not covered by peritoneum or amnion
Not associated with chromosomal abnormalities, favorable prognosis

Question 4

Omphalocele

Answer 4

Failure of lateral walls to migrate at umbilical ring–> persistent midline herniation of abdominal contents into umbilical cord

Surrounded by peritoneum abdominal contents are sealed

Associated with congenital anomalies (trisomies 13, 18, Beckwith Wiedermann syndrome) and other structural abnormalities (cardiac GU, neural tube)

Question 5

Tracheoesophageal anomalies

Answer 5

Esophageal atresia (EA) with distal tracheoesophageal fistula (TEF) is the most common 85%
and often presents as polyhydramnios in utero (baby cant swallow amniotic fluid. Continue to make urine cause the umbilical blood supply

Neonates drool, choke, and vomit with first feed

TEFs allow air to enter in stomach

Cyanosis 2’ to laryngospasm (to avoid reflux related aspiration, failure to pass nasogastric tube into stomach

in H type, the fistula- like above but can get food in

pure EA - nothing gets into stomach

Question 6

Intestinal atresia

Answer 6

presents with bilious vomiting and abdominal distension within 1st 1-2 days of life.

Duodenal atresia- failure to recanalize, abdominal xray shows double bubble (stomach pyloric sphincter dudenum and atretic portion of duodenum. Associated with Down syndrome

Jejunal/ileal astresia- disruption of mesenteric vessels (typically SMA)–> ischemic necrosis of fetal intestine –> segmental resorption –> bowel becomes discontinuous. Xray shows dilated loops of small bowel with air fluid levels

Question 7

Hypertrophic pyloric stenosis

Answer 7

Most common cause of gastric outlet obstuction in infants (1/600)
olive shaped mass in epigastric region, visible peristaltic waves, and nonbilious projectile vomiting at 2-6 weeks old. More common in first born males, associated with exposure to macrolides

Results in hypokalemic hypochloremic metabolic alkalosis (2’ to vomiting of gastric acid and subsequent volume contraction)

treatment - pylorotomy

Question 8

Pancreas and spleen embryology

Answer 8

Pancreas- derived from foregut. Ventral pancreatic bud contributes o uncintate process and main pancreatic duct

The dorsal pancreatic bud alone becomes body, tail, isthmus and acessory pancreatic duct, both ventral and dorsal buds contricute to pancreatic head

Annular pancreas- abnormal rotation of ventral pancreatic bud forms a ring of pancreatic tissue- encircles 2nd part of duodenum, may cause duodenal narrowing and vomiting

Pancreas divisum- ventral and dorsal parts fail to fuse at 8 weeks. common anomaly - mostly asymptomatic, but may cause abdominal pain pancreatitis

Spleen spleen is mesentery of stomach, but has foregut supply from splenic artery

Question 9

Falciform ligament

Answer 9

Connects liver to anterior abdominal wall

Ligamentum teres hepatis- derived from fetal umbilical vein), patent paraumbilical veins

Derivative of ventral mesentery

Question 10

Hepatoduodenal ligament

Answer 10

connects liver to duodenum

Contains portal triad : proper hepatic arter, portal vein, common bile duct

Derivative of ventral mesentery
Pringle maneuver- ligament compressed manually or with vascular clamp in omental foramen, to control bleed from hepatic inflow source

Part of lesser omentum

Question 11

Gastrohepatic ligament

Answer 11

connects the liver to lesser curvature of stomach

contains gastric vessels

Derivative of ventral mesentery separates greater greater and lesser sacs on the right, may be cut during surgery to access lesser sac, part of lesser omentum

Question 12

Gastrocolic ligament-

Answer 12

connects the greater curvature and transverse colon

Gastroepiploic arteries, derivative of dorsal mesentery, part of greater omentum

Question 13

Gastrosplenic ligament

Answer 13

connects Greater curvature and spleen, short gastics, left gastroepiploic vessels

Derivative of dorsal mesentary , separates greater and lesser sacs on the left part of greater omentum

Question 14

Digestive tract anatomy

Answer 14

Layers of gut wall inside to out

Mucosa- (epithelium, lamina propria, muscularis mucosa)
Submucosa- includes the submucosal nerve plexus (meissner), secretes fluid
Muscularis externa- includes myenteric nerve plexus (Aurebachs) for motility
Serosa- when intraperitoneal, adventitia when retroperitoneal

Ulcers can extend into submucase, inner or outer muscular layer. Erosiion is just mucosa

Frequency of basal electrical rhythms (slow waves) which originate in the intersitital cells of cajal- Stomach 3 waves a minute, duodenum (12 waves a minute), ileum (8-9 waves a minute

Question 15

Digestive tract histology

Answer 15

esophagus- nonkeratinized stratified squamous epithelium. upper 1/3 is striated muscle, middle and lower 2/3 smooth muscle, with some overlap at transition
Stomach- gastric glands
Duodenum- contain villi, and microvili (increase absorptive surface, Brunners glands (HCO3- secreting cells of sumbucosa), crypts of lieberkuhs (contain stem cells that replace enterocytes/goblet cells and Paneth cells that secrete defensins, lysozyme, and TNF)

Jejunum- villi , crypts of lieberkuhn, and -plicae circularis
ileump- pyeyrs pathces, lymphoid aggregates in lamina propria, submucosa, plicae circulares (proximal ileum) and crypts of liberukuhns largest number of goblet cells in the small intestine

Colon- no villi, crypts of lieberkuhn with abundant goblet cells

Question 16

nutcracker syndrome

Answer 16

compression of left renal vein between SMA and Aorta, characteristic abdominal flank pain and gross hematuria (from rupture of thin walled renal varicositeis

Question 17

SMA syndrome

Answer 17

intermited obstruction symptoms when SMA and Aorta compress transverse compress transverse protrion of duodenum, typucally in conditions associated with deminished mesenteric fat (low body weight/ malnutrition

Question 18

Gastrointestinal blood supply and innervation

Answer 18

Celiac and SMA get parasympathetic from vagus

IMA- gets from pelvic innervation)

Question 19

Portosystemic anastomoses

Answer 19

Esophagus –> esophageal varices- left gastric (portal system) and esophageal (from azygous)

Umbilical–> Caput medusa (paraumbilical from portal system–> small epigastric veins of the anterior abdominal wall

Rectum-> anorectal varices Superior rectal (from portal, IMV)–> middle and inferior rectal

treat with a transjugular intra hepatic shunt (TIPS) between the portal vein and hepatic vein relieves portal hypertension by shunting blood to the systemic circulation, bypassing the liver, TIPS ccan precipitate hepatic encephalopathy due to decreased clearance of ammonia from shunting

Question 20

Pectinate Line

Answer 20

Above: visceral innervation, IMV, IMA, lymphatics drain to internal iliac LN

Below: somatic innervation, inferior rectal arteru (branch of intern al pudendal artery. Inferior rectal vein-> pudendal, internal iliac-> common iliac -> IVC. Lymphatics–> drain to superficial inguinal lN

Question 21

Anal fissures

Answer 21

Located posteriorly bc poor perfusion, innervated by pudendal nerve

Question 22

Liver tissue architecture

Answer 22

functional unit is made up of hexagonal arranged lobules surrounding the central vein with portal triads on the edges (consisting of a portal vein, hepatic artery, bile ducts as well as lymphatics)

Apical surface of hepatocytes faces bile canaliculi, basolateral surface faces sinusoids

Kupffer cells (specialized macrophages) located in sinusoids clear bacteria and damaged or senescent RBCs

Hepatic Stellate (Ito) cells in space of disse store vitamin A (when quiescent) and produce extracellular matrix (when activated), responsible for hepatic fibrosis

Zone 1 (periportal zone)- affected 1st by viral hepaptitis, best oxygenated, most resisitant to circulatory compromise (ingested toxins (cocaine)

Zone 2- intermediated zone (yellow fever)

Zone 3- pericentral vein (centrilobular) zone: affected 1st by ischemia (least oxygenated), High Concentration of cyp 450, most sensitive to metabolic toxins (ethanol, CCL4, halothane, rifampin, acetaminophen). Site of alcoholic hepatitis

Question 23

Biliary structures

Answer 23

Gallstones that reach the confluence of the common bile and pancreatic ducts at the ampulla of Vater can block both the common bile and pancreatic ducts

Tumors that arise in the head of pancreas (usually ductal adenocarcinoma) can cause obstruction of common bile duct–> enlarged gallbladder with pain jaundice (Courvoidier sign)

Cholangiography shows filling defects in gallbladderand cystic duct

Question 24

Inguinal canal

Answer 24

Deep inguinal ring (internal- site of protrusion of indirect hernia
Abdominal wall - site of protrusion of direct hernia

Layers of abdominal wall from in to out
Parietal peritoneum> Extraperitoneal tissue> transversalis fascia>Transversus abdominus> internal oblique> aponeurosis of external oblique muscle> inguinal ligament

Spermatic cord/
ICE TIE (Internal spermatic fascia/transversalis, Cremasteric muscle/internal oblique, external spermatic fascia/external oblique

Question 25

Hernias

Answer 25

Protrusion of peritoneum through opening usually at site of weakness, contents may be at risk for incarceration ( not reducible back into abdomen/pelvis) and strangulation(ischemia and necrosis) tenderness, erythema, fever

Question 26

Diaphragmatic hernia

Answer 26

Abdominal structure enter the thorax Congenital defect of pleuroperitoneal membrane or from trauma- usually occurs on left side due to relative protection of right hemidiaphragm by liver, most commonyl a hiatal hernia, in which stomach herniates upward through the esophageal hiatus of the diaphragm Sliding hiatal hernia, paraesophageal hiatal hernia

Question 27

Indirect inguinal hernia

Answer 27

through the deep inguinal ring, external inguinal ring, and into the groin, enters internal inguinal ring lateral to the inferior epigastric vessels Caused by failure of processus vaginalis to close ( can form hydrocele) may be noticed in infants or discovered in adulthood much more common in males Follows the path of testicular descent Covered by all 3 layer of spermatic fascia

Question 28

Direct inguinal hernia

Answer 28

protudes theough inguinal hesselbach triangle , bulges directly through parietal peritoneum medial to the inferior epigastric vessels but lateral to the rectus abdominus goes through extrernal superficial inguinal ring only. covered by external spermatic fascia

Question 29

Femoral hernia

Answer 29

protudes below inguinal ligament through femoral canal below and lateral to Pubic tubercle, more common in females More likely to incarcerate

Question 30

Gastrin

Answer 30

G cells make it, (antrum of stomach, duodenum) Increases Gastric H secretion, growth of gastric mucosa, increased gastric motility Increased by stomach distension/ alkalinization, amino acids, peptides, vagal stimulation via gastrin-releastng peptide Decreased by acid increased by chronic PPI use, increased by chronic atrophic gastritis ( H pylori), increased in ZE syndrome--> gastrinoma)

Question 31

Somatostatin

Answer 31

made by D cells, pancreatic islets, GI mucosa Inhibits the secretion of hormones Octreotide is an analog treats agromegaly, carcinoid syndrome, variceal bleeding

Question 32

Secretin

Answer 32

S cells of duodenum Increased HcO3- neutralizes gastric acid in duodenum, allowing pancreatic enzymes to function

Question 33

Glucose dependent insulinotropic peptide

Answer 33

K cells in duodenum and jejcunum Increases insulin release, decreasess gastric acid Gastric inhibitory peptide Oral glucose load increases insulin compared to IV equivalent due to FIP secreion

Question 34

Vasoactive intestinal polypeptide

Answer 34

Parasympathetic Ganglia in sphinters, gallbadder, small intestine Increases water and electrolyte secretion Increases relaxation of intestinal smooth muscle and sphincters Relaxes intestinal smooth muscles and sphincters Vagal stimulation decreased by adrenergic input VIPOMA- pancreatic tumor that secretes VIP, Wattery diarrhea, hypokalemia, Achlorhydia

Question 35

Pancreatic secretions

Answer 35

Isotonic fluid, low flow--> high Cl-, high flow--> high HCO3- Alpha amylase- for starch digestion, secreted in active form Lipases- fat digestion Proteases- Protein digestion (includes trypsin, chymotrypsin, elastase, carboxypeptidases). Secreted as proenzyme also called zymogens Trypsinogen- converted to active enzyme trypsin--> activation of other proenzymes and cleaving of additional trypsinogen molecules into active trypsin (posidive feedback)- converted to trypsin by enterokinase/enteropeptidase a brush border enzyme on duodenal and jejunal mucosa

Question 36

Carb absorption

Answer 36

Only monosaccharieds (glucose, glactose, fructose) are absorbed by enterocyted Glucose and galactose are taken up by SGLT1 (Na dependent) Fuctose is taken up via facilitated diffusion by GLUT5, All are transported to blood by GLUT2 D-xylose absorption test: simple sugar that requires intact mucosa for absorption, but does not require digestive enzymes. So as long as your mucosa isnt damaged you should be able to take it up

Question 37

Vitamin and mineral absorption

Answer 37

Iron- absorbed as Fe++ in duodenum Folate- absorbed in small bowel Vitamin B12- Absorbed in terminal ileum along with bile salts, requires intrinsic factor Iron Fist Bro- small bowel disease (vit B 12 deficienct after terminal ileum resection) Hepcidin inhibits ferroportin1

Question 38

Peyers patches

Answer 38

unencapsulated lymphoid tissue found in lamina propria and submucosa of ileum Contain specialized M Cells that sample and present antigens to immune cells (DCs ) B cells stimulated in germinal centers of peyer patches differentiate into IgA secreteing plasma cells, which ultimately reside in lamina propria IgA receives protective secretory component and is then transported across the epithelium to the gut to deal with intraluminal antigen

Question 39

Bile

Answer 39

Composed of bile salts (bile acids conjugated to glycine or taurine, making them water soluble) Phospholipids, cholesterol, bilirubin, water and ions Cholesterol 7ahydroxylase catalyzes rate limiting step of bile acid synthesis ``` Functions- digestion and absorption of lipids and fat soluble vitamins Cholesterol excretion (bodys 1' means of eliminating cholesterol) Antimicrobial activity (via membrane disruption) ``` decreased absorption of enteric bile salts at distal ileum (as in short bowel syndrome, crohn disease), prevents nnormal fat absotption Calcium, which normally binds oxalate, binds fat instread so free oxalate is absorbed by gut --> increased frequency of calcium oxalate kidney stones

Question 40

Bilirubin

Answer 40

heme is metabolized by heme oxygenase to biliveridin (makes bruise green/yellow) which is subsequently reduced to bilirubin Unconjugated bilirubin is removed from blood by liver, conjugated with glucuronate and excreted in bile Some of the conjugated bilirubin that ends in the gut is converted by urobilinogen (brown color stool) stercobilin and 20% is recycled back to kidney (excreted as urobilin)

Question 41

Sialolithiasis

Answer 41

Stones in salivary gland duct Parotid, submandibular, sublingual Usually submandibular gland (wharton duct) Presents as recurrent pre/periprandial pain and swelling Caused by dehydration or trauma NSAIDs, gland massage, warm compresses, sour candies (to promote salivary flow) Sialadenitis- inflamation of salivary gland due to obstruction, infection, immune mediated mechanisms

Question 42

Salivary gland tumors

Answer 42

parotid gland, usually benign if submandibular or sublingual its malignant Facial paralysis or pain suggests malignancy Pleomorphic adenoma- benign mixed tumor, most common slivary gland tumor, composed of chondromyxoid stroma and epithelium and recurs if incompletely excised or ruptured intraoperatively. may undergo malignant transformation mucoepidermoid carcinoma- malignant, mucinous and squamous components Warthin tumor- papillary cystadenoma lympho- geminal center in smokers, typically in smokers, bilateral in 10%

Question 43

Achalasia

Answer 43

Failure of LES to relax due to degeneration of inhibitory neurons (containing NO and VIP) in the myenteric Auerbachs plexus of the esophageal Wall Uncoordinated/absent peristalsis with high LES resting pressure-> progressive dysphagia to solids and liquids (vs obstructive) Dilated associated with increased risk of esophageal cancer 2' from Chagas or extraesophageal malignancies (mass effect)

Question 44

Diffuse esophageal spasm

Answer 44

Spontaneous, nonperistaltic (uncoordinated) contractions with normal LES pressure dysphagia, angina like chest pain corkscrew esophagus Nitrates and CCB

Question 45

Eosinophilic esophagitis

Answer 45

Infilitration of eosinophisl in esophagus often in atopic patients Food allergens--> dysphagia, food impaction esophageal rings and linear furrows often seen on endoscopy, typically unresponsive to GERD

Question 46

Esophageal perforation

Answer 46

most commonly iatrogenic following esophageal instrumentation Non iatrogenic causes- spontaneous ruputure, foreign body ingestion, trauma, malignancy May present with pneumediastinum subQ emphysema may be due to dissecting air (signs include crepitus in the neck region or chest wall) Boerhaave syndrome- transmural usually distal esophageal rupture due to violent retching

Question 47

esophageal strictures

Answer 47

associated w/ caustic ingestion, acid reflux, and esophagitis

Question 48

Esophagitis

Answer 48

Candida- Pseudomembrane HSV- punched out ulcers CMV- linear ulcers

Question 49

Mallory weiss syndrome

Answer 49

Partial thickness longitudinal laceration hematemisis Alcoholics and bulimeics

Question 50

Plummer Vinson sydrome

Answer 50

Dysphagia, Iron deficiengt, Esophageal webs, Sqaumous cell carcinoma Glottitis Can eat steak

Question 51

Schatzki ringa

Answer 51

rings at GE junction from GERD

Question 52

Sclerodermal esophageal dysmotility

Answer 52

esophageal smooth muscle atrophy- lower LES pressure and dysmotility ACid reflux and dysphagia-> stricture Barret esophagus and aspiration part of CREST syndrome

Question 53

Barrett esophagus

Answer 53

intestinal metaplasia nonkeratinized stratified squamous epithelium--> intestinal epithelium (nonciliated columnar with goble cells)

Question 54

Acute gastritis

Answer 54

Erosions can be caused by: NSAIDs- decrease PGE2--> decrease gastric mucosa protection Burns (Curling ulcer)- hypovolemia--> mucosal ischemia Brain injury (cushing ulcer)-> increased Vagal stimulation--> increased Ach/GRH--> H production Especially common in alcoholics and pts taking NSAIDs

Question 55

Chronic gastritis

Answer 55

Mucosal inflammation leading to atrophy (hypochlorhydia--> hypergastrinemia and intestinal metaplasia (increased risk of gastric cancer H pylori- most common, increased risk of PUD, MALT lymphoma, affects the antrum first and spreads to body of stomach Autoimmune- Ab to the HK ATPase on parietal cells and to Intrinsic factor

Question 56

Menetrier disease

Answer 56

gastric mucosa hyperplasia hypertrophied rugai- excess mucus production with protein loss and parietal cell atrophy with decreased acid production Precancerous Weight loss, Anorexia, Vomiting, Epigastric pain, Edema (protein loss) cant cut up proteins

Question 57

Gastric cancer

Answer 57

gastric adenocarcinoma, lymphoma, GI stromal tumor, and rarely carcinoid Local spread with node/liver mets late with wt loss, abdominal pain, early satiety, acanthosis nigricans, Leser-Trelat sight blood type A Diffuse- E cadherin mutation signet ring cells (mucin filled cells with peripheral nuclei), stomach grossly thickened and leathery (linitis plastica) Intestinal type- H pylori, diet, lifestyle Virchow node- involvement of left supraclavicular node Krukenberg tumor- bilat mets to ovaries Sister mary joseph nodule- subQ periumbilical mets (cause nuns cross hands on belly button) Blumer shelf- in pelvic pouch

Question 58

Gastric vs Duodenul ulcer

Answer 58

Gastric ulcer- Greater with meals, | Duodenal ulcer- better with meals cause you dilute the acid

Question 59

Ulcer complication

Answer 59

hemorrhage, lesser curvature- from left gastric artery, Posterior wall of duodenum-bleeding from gastroduodenal artery Obstruction- pyloric channel, duodenal Perforation- duodenal anterior> posterior. Pneumoperitoneum, free air under diaphragm

Question 60

Celiac disease

Answer 60

Gluten-sensitivity eneteropathy, Autoimmune-mediated intolerance of gliadin (gluten protein found in wheat)--> malabsorption and steatorrhea HLADQ2 and 8 dermatitis herpetiformis, decreased bone density IgA antitissue transglutaminase (IgA tTG) anti endomysial, anti-deamidated gliadin peptide Ab, villous atrophy, crypt hyperplasia, intraepithelial lymphocytosis distal duodenum and or proximal jejunum D-xylose- decreased

Question 61

Whipple disease

Answer 61

tropheryma whipplei PAS+ foamy macrophages in intestinal lamina propria Mesenteric node Cardiac symptoms, Arthralgias, Neurologic symptoms Diarrhea/steatorrhea