GI USMLE

G cells

• produce gastrin

• antrum of stomach/ duodenum

• promote gastric acidity and motility

ghrelin

• hunger hormone

• produced by stomach

D cells

• somatostatin

• produced in pancreatic islets/ GI mucosa

• decrease insulin and glucagon release/ and gastric acidity

I cells

• cholecystokinin

• duodenum/ jejunum

• promote pancreatic secretions and sphincter of oddi relaxation

S cells

• secretin

• duodenum

• neutralize stomach acidity/ promote bile secretion

K cells

• glucose dependant insulinotropic peptide

• duodenum, jejunum

• promote bile secretion and gastric neutrality

motilin

• SI

• raised in fasting state 

vasoactive intestinal peptide

• parasympathetic ganglia in sphincters/ gallbladder/ SI

• promotes intestinal water and electrolyte secretion/ smooth muscle relaxation

• decrease gastric secretion

nitric oxide

promotes smooth muscle relaxation

induces lower esophageal sphincter

gastric acid

• parietal cells

intrinsinc factor

• parietal cells

• vitamin B12 binding protein

chief cells

• pepsin

• protein digestion

bicarbonate

• produced by mucosal cells of stomach/ duodenum/ salivary glands/ pancreas AND BRUNNER GLANDS (duodenum)

• neutralizes acid

cleft lip and palate

• failure of facial prominence to fuse

• seen in digeorge

aphtous ulcer

A. Painful, superficial ulceration ofthe oral mucosa

B. Arises in relation to stress and resolves spontaneously, but often recurs

C. Characterized by a grayish base surrounded by erythema

behcet syndrome

reccurent aphtous ulcers/ genital ulcers and uvitis

due to immune complex small vessel vasculitis

etiology unknown, usually seen after viral infection

oral herpes

rupture of oral mucosa vesicles → shallow painful ulcers

HSV1

often primary infection in childhood that remains dormant

can be reactivated by stress/ sun exposure

SCC mouth

• risk factors; tobacco, alcohol

• often floor of mouth

• leukoplakia/ erythroplakia are precursor lesions

mumps

bilateral inflammed parotid gland

orchitis, pancreatitis and aseptic meningitis can also present

• serum amylase increase

• orchitis carries sterility risk in teens

sialadenitis

salivary gland inflammation

most commonly due to obstructing stone → staph infection

usually unilateral

pleomorphic adenoma salivary gland

made of cartilage and epithelial tissue

most common salivary gland tumor

usually in parotid

mobile/ painless/ circumsised mass at jaw angle

high rate of reccurence

can become carcinoma → presenst w/ facial nerve damage

warthin tumor salivary gland

benign cystic tumor

abundant lymphocytes/ germinal centers

almost always parotid gland\

second most common tumor 

mucoepidermoid carcinoma

maligannt tumor salivary gland made of mucinous and squamous cells

most common malignant tumor salivary gland

usually arise in parotid

commonly affects facial nerve

tracheoesophageal fistula

congenital defect→ connection between esophagus and trachea

most common→ proximal esophageal atresia (distal esophagus arising from trachea)

presents w/ vomiting/ abdominal distention/ aspiration/ polyhydramnios 

esophageal web

thin protusion esophageal mucosa

upper esophagus most common

presents w/ dysphagia for poorly chewed food

increased risk of esophageal SCC

plummer vinson syndrome

can occur as result of esophageal web

severe iron def anemia and beefy red tongue due to atrophic glossitis

zenker diverticulum

outpouching of pharyngeal mucosa through acquired defect in muscular wall (false diverticulum)

arises above upper esophageal sphincter at junction of esophagus and pharynx

presents w/ bad breath, dysphasia and obstruction

mallory weiss syndrome

longitudinal laceration of mucosa at gastroesophageal junction

caused by severe vomiting (common causes include bulimia and alcohol)

painful hematemesis 

boerhaave syndrome

complication of amllory weiss syndrome

esophageal rupture → air in mediastinum and subq emphysema 

esophageal varices

dilated submucosal veins in lower esophagus

secondary to portal hypertension

if rupture

1. painless hematemesis

2. most common cause of death in cirrhosis 

achalasia

disordered esophageal motility

cant relax lower esophageal sphincter due to damaged ganglion in myenteric plexus

• can be secondary to changa disease

clinical features

• dysphasia

• high LES pressure on manometry

• bad breath

• bird beak sign on barium swallow study

increased risk esophageal SCC

GERD

acid reflux from stomach due to lower LES tone

risk factor; alcohol, tobacco, fat rich diet, caffeine, hiatal hernia 

clinical features

• heartburn

• asthma 

• damage to teeth enamel

• ulceration with stricture and barrett esophagus are late complications

barrett esophagus

metaplasia of lower esophageal mucosa from stratified squamous epithelium to noncilliated columnar epithelium with goblet cells

10% of patients with GERD have it

may progress to dysplasia and adenocarcinoma

esophageal carcinoma

adenocarcinoma- western world, barrett esophagus, lower 1/3 esophagus

SCC- most common worldwide, risk factors include hot foods, alcohol, tobacco, achalsia, esophageal web/ injury

• often upper/ middle third esophagus 

gastrochisis

congenital malformation of anterior abdominal wall

exposure abdominal content

omphalocele

persistant herniation of bowel into umbilical cord

due to failure of herniated intestines to return to body cavity during development

content covered by peritoneum and amnion of umbilical cord

pyloric stenosis 

congenital hypertrophy of pyloric smooth muscles 

classically presents 2 weeks after birth

• projectile non billious vomiting

• visible peristalsis

• olive like mass in abdomen

tx is myotomy

acute gastritis

acidic damage to stomach mucosa due to imbalance between mucosal defense and acidic environment

risk factors

• ulcers

• NSAIDs

• heavy alcohol consumption

• chemo

• shock

chronic gastritis

chronic inflammation stomach mucosa 

H pylori

• 90%

• autrum most commonly affected

• epigastric abdominal pain

• risk of ulcers/ adenocarcinoma/ malt lymphoma

• tx; triple therapy

• diagnosis; breath test/ stool antigen 

chronic autoimmune

• 10%

• type IV T cell hypersensitivity

• atrophy of mucosa w/ intestinal metaplasia

• achlorhydria w/ increased gastrin levels and antral G cells hyperplasia

• megaloblastic anemia

• raised risk adenocarcinoma

PUD

solitary ulcer

often duodenal > stomach

almost always caused by H pylori

id duodenal- and gets better w/ food 

on endoscopy; ulocer w/ brunner gland hypertrophy

if gastric- pain worsens with meals

lesser curvature of antrum

can be caused by gastric carcinoma

gastric carcinoma

adenocarcinoma

presents late

2 types

intestinal; most common type, large irregular ulcers w/ heaped up marginssome risk factors include nitrosamines in smoked food and type A blood 

diffuse; signet ring cells diffusely infiltrating gastric wall/ stomach wall thickening

bilateral ovaries can occur with this type

duodenal atresia

congenital failure of duodenum to canalize

• double distention/ double bubble sign

• billious vomiting

associated w/ down syndrome

meckel diverticulum

outpouching of all 3 layers of bowel wall due to failure of vitteline duct to involute

most common congenital anomaly of GI tract

presents within first 2 years of life w/ bleeding, volvulus, intussuspection or obstruction

volvulus

twisting of bowel along mesentery → obstruction and blood supply restriction

sigmoid colon- elders

cecum- young adults

intussuspection

telescoping of proximal segment of bowel forward into distal segment

telescoped segment pulled forward by peristalsis → obstruction and blood flow restriction/ infarct

in children- often caused by lymphoid hyperplasia secondary to rotavirus

in adults- usually caused by tumors

small bowel infarct

risk of ischemia

• transmural; w/ thrombosis/ embolism of superior mesenteric artery/ vein

• mucosal infarct occurs with marked hypotension

comes w/ abdominal pain, bloody diarrhea and decreased bowel sound

lactose intolerance

decreased function of lactase enzyme found in brush border of enterocytes

presents w/ abdominal distension and diarrhea after milk consumption

temporary deficiency is seen after small bowel infection

celiac disease

immune mediated damage of small bowel villi due to gluten exposure associated w/ HLA DQ2 and DQ8

pathogenic component of gluten is gliadin

• deaminated by TTG

• THC II → T cells mediated tissue damage

small herpes like vesicles may arise on skin due to IgA deposits at tips of dermal papillae

• usually pts are IgA def

flattening of villi, hyperplasia of crypts and increased lymphocytes in duodenum

complications include small bowel carcinoma and T cell lymphoma

tropical sprue

damage to small bowel villi due to unknown organism resulting in malabsorption

similar to celiac but occurs in tropical regions, responds to antibiotics and damage more so in ileum/ jejunum

whipple disease

systemic tissue damage characterized by macrophages loaded with tropheryma whippelii organisms within macrophages

usually affect lamina propria of small bowel

leads to malabsorption of fat and steatorrhoea

other common involvements include arthritis, cardiac valves, lymph nodes and CNS

abetalipoproteinemia

autosomal recessve deficiency of apoliprotein B48 and B100

leads to malabsorption due to absent VLDL/ LDL

carcinoid tumor

malignant proliferation of neuroendocrine cells

low grade malignancy

can occur anywhere along gut but small bowel is most common site

polyp like nodule

seretonin secreting, metabolized by liver MAO into 5HIAA

mets to liver

carcinoid syndrome; flushing, bronchospasms, diarrhea

carcinoid heart disease; right sided valvular fibrosis (increased collagen) → tricuspid regurg and pulmonary valve stenosis

acute appendicitis

most common cause of acute abdomen

related to obstruction of appendix by lymphoid hyperplasia in children or fecalith in adults

mcburney point

rupture; peritonitis w/ guarding/ rebound tenderness

IBD

chronic relapsing

potentially due to abnormal immune response to enteric flora

young women

UC vs CD

hirschsprung disease 

defective relaxation and peristalsis of rectum and distal sigmoid colon

down syndrome association

due to congenital failure of ganglion cells to descend in myenteric and submucosal plexus

clinical failures include failure to pass meconium, empty rectal vault on DRE and megacolon

rectal colon biospy shows lack of ganglion cells

Tx; colon resection

colonic diverticula

outpouching of mucosa/ submucosa through muscularis propria

related to wall stress

usually asymptomatic, symptoms include constipation, straining…

usually older adults with low fiber diet

complications include rectal bleeding, fistula and diverticulitis

angiodysplasia

acquired malformation of mucosal and submucosal capillary beds

usually arise from cecum and right coloin due to high wall tension

rupture presents as hematochezia in older adults

hereditary hemorrhagic telangiectasia

autosomal dominant disorder

thin walled blood vessels in mouth and GI

rupture → bleeding

ischemic colitis

ischemic damage to colon at spenic flexure

artherosclerosis of SMA is most common cause

presents with postprandial pain and weight loss

infarcts lead to pain and bloody diarrhea

IBS

relapsing abdominal pain with bloating, flatulance and change in bowel habits improving w/ defecation

classically affects middle aged females

related to disturbed intestinal mobility 

can be solved by increasing fiber intake

hyperplastic colonic polyps

hyperplasia of glands

serrated appearnce on micro

most common

benign

usually left colon

adenomatous colonic polyps

neoplastic proliferation of glands

second most common polyp type

benign but may progress to adenoma-carcinoma → adenocarcinoma

• APC

• Kras

• p53

greatest risk of becoming carcinoma is polyp >2cm, sessile growth and villous histology

familial adenomatous polyp

autosomal dominant disorder

100s-1000s of polyps

due to APC mutation on chromosme 5 

colon and rectum remove prophuylactically- otherwise carcinoma by 40s

gardner syndrome

FAP w/ fibromastosis (fibroblasts in retroperitoneum) and osteomas (skull)

turcot syndrome

FAP w/ CNS tumors (medulloblastoma and glial )

juvenile polyp

sporadic hamartomatous polyp in children

usually solitary polyp that prolapses and bleeds

juvenile polyposis; many polyps in stomach and colon, incraeses carcinoma progression risk

peutz jeghers 

benign polyp through GI and mucocutaneous hyperpigmentation on lips, oral mucosa and genitalia

autosomal dominant

increases risk of colorectal, breast and gyno cancer

colorectal carcinoma

carcinoma arising from colonic/ rectal mucosa

3rd most common cancer/ 3rd most deadly

peak incidence 60s-70s

mostly arise from adenoma-carcinoma sequence

• or microsatellite instability

• or hereditary (HNPCC)- early age, right sided

screening starts at 50 w/ fecal ocult blood and colonoscopy

• left lesion; napkin ring lesion, blood streak stool

• right lesion; raised, occult bleeding and iron def anemia

colon carcinoma is risk factor for strep bovis endocarditis

CEA serum marker used to assess treatment response amd reccurence but not screening

annular pancreas

developmental malformation in which pancreas forms ring around duodenum

risk of duodenal obstruction

acute pancreatitis

inflammation and hemorrhage of pancreas

due to autodigestion of parenchyma by pancreatic enzymes

• premature activation of trypsin → cascade activation of other enzymes

results in liquefctive hemorrhagic necrosis of pancreas and fat necrosis or peripancreatic fat

most common causes are alcohol and gallstones

clinical features include epigastric abdominal pain radiating to back, nausea and vomiting, cullens and gray hemorrhage, elevated serum amylase and lipase and hypocalcemia

complications include shock, pseudocyst, DIC, ARDS and abscess (e coli related)

chronic pancreatitis

fibrosis of pancreatic parenchyma → most often follows reccurent acute pancreatitis

• common causes include CF and alcohol

clinical features include epigastric abdominal pain radiating to back, pancreatic insufficiency → malabsorption/ vitamin def, dystrophic calcifications with chain of lakes patterns on contrast studies, secondary DM

risk of pancreatic carcinoma

amylase/ lipase not useful markers here

pancreatic carcinoma

adenocarcinoma of pancreatic ducts

older adults

risks include smoking and chronic pancreatitis

late diagnosis

symptoms include epigastric pain, weight loss, obstructive jaundice, pale stool, palpable gallbladder, secondary DM, pancreatitis, migratory thrombophlebitis (trousseau syndrome)

serum tumor marker is CA 19-99

surg- whipple

poor prognosis

biliary atresia

failure to form/ early destruction of extrahepatic biliary tree

biliary obstruction within forst 2 months of life

jaundice → cirrhosis 

cholelithiasis

aka gallstones

solid, round stones of gallbladder

due to cholesterol (most common)/ bilirubin precipitation

• supersaturation of either substances

• decreased phospholipids/ bile acids

• stasis

cholesterol stones are usually radiolucent and more common in middle aged women w/ chrons disease/ cirrhosis 

bilirubin stones are usually opaque and associated w/ extravascular hemolysis and biliary tract infections

by themselves gallstones are typically asymptomatic

biliary colic

waxing and waning RUQ pain

due to gallbaldder contracting against stone in cystic duct

symptoms relieved if stone passed

common bile duct obstruction can lead t acute pancreatitis / obstructive jaundice 

acute cholecystitis

acute inflammation gallbladder wall

impacted stone in cystic duct → dilation w/ pressure ischemia, bacterial overgrowth (e coli) and inflammation

presents w/ RUQ pain radiating to right scapula, fever w/ raised WBC, nausea, vomiting and raised serum alkaline phosphate from duct damage

risk of rupture if left untreated 

chronic cholecystitis

chronic gallbladder inflammation

due to chemical irritation from longstanding cholelithiasis

can present with or without bouts of acute cholecystitis 

charcaterized by herniation of gallbladder mucosa into muscular wall

vague RUQ pain after eating

tx is cholecystomy

porcelain gallbladder

late complication of chronic cholecystitis

shrunken, hard gallbladder due to chronic inflammation w/ fibrosis and dystrophic calcification

incraesed carcinoma risk

tx is cholecystomy 

ascending cholangitis

bacterial infection of bile duct

gram neg bacteria

presents as sepsis, jaundice, and abdominal pain

increased incidence w/ choledocholithioasis

gallstone ileus

obstruction of small bowel w/ gallstone

due to cholecystitis w/ fistual formation between gallbladder and small bowel

gallbladder carcinoma

adenocarcinoma of glandular epithelium lining gallbladder wall

gallstones are a major risk factor, esp w/ porcelain gallbladder

classically presents as cholecystitis in older women

poor prognosis

jaundice

yellow discouloration of skin

earliest sign is scleral icterus

serum bilirubin > 2.5 mg/dL

arises w/ disturbances in bilirubin metabolism

causes include

• extravascular hemolysis / ineffective erythropoiesis

• gilbert syndrome

• dubin johnson

• viral hepatitis

• biliary tract obstruction

normal bilirubin metabolism

1. rbc consumed by macrophages of reticuloendothelial system

2. protoporphyrin form heme converted to unconjugated bilirubin

3. albumin carries UCB to liver

4. UGT in hepatocytes conjugates bilirubin

5. conjugated bilirubin transferred to bile canaliculi to form bile, which is stored in gallbladder

6. bile released in small bowel to aid digestion

7. excreted via poop and pee → make them colour that they are 

extravacsular hemolysis/ ineffective erythropoiesis

causes jaundice

elevated UCB is too much for liver to process

dark urine

increased risk of pigmented bilirubin gallstones

physiologic jaundice of newborn

causes jaundice

elevated UCB

treatment is phototherapy

untreated→ neuro deficits and death

gilbert syndrome

causes jaundice

elevated UCB

autosomal recessive

jaundice during stress (severe infection)

crigler najar syndrome

causes jaundice

elevated UCB

abscence of UGT

kernicterus, usually fatal

dubin johnson syndrome

def of bilirubin canalicular transport protein

autosomal recessive

causes jaundice

elevated CB and alkaline phosphatase

low urine urobilinogen

dark urine and pale stool

pruritus

hypercholesterolemia

steatorrhea

viral hepatitis

inflammation of liver parenchyma, other causes tha hepatitis include EBV and CMV

• raised UCB and CB

• jaundice

inflammation disrupts hepatocytes and small bile ductules

dark urine

raised liver enzymes

nausea/ vomiting

acute hepatitis

symptoms last under 6 months

inflammation of liver lobules/ portal tracts → apoptosis of hepatocytes

chronic hepatitis

symptoms last over 6 months

inf of portal tract

can progress to cirrhosis

hep A

fecal oral

travellers

acute

• anti IgM- active inf

• anti IgG- protective

hep E

fecal oral

contaminated water/ undercooked seafood

acute

• anti IgM- active inf

• anti IgG- protective

in pregnancy- liver failure/ necrosis 

hep B

parental transmission/ needles

chronic disease in 20% cases

hep C

parental transmission

risk from transfusion almost inexistant due to screening of blood supply

chronic disease common

• HCV RNA confirms infection

• low RNA indicates recovery

• persistance of RNA → chronic disease 

hep D

dependant on Hep B for infection

superinfection upon existing hep B more severe > coinfection

cirrhosis

end stage liver damage charcaterized by disruption of normal hepatic parenchyma by bands of fibrosis and regenerative nodules of hepatocytes

• fibrosis mediated by TGF-B from stellate cells

portal HPT leads to

• ascites

• congestive splenomegaly/ hypersplanism

• portosystemic shunts/ esophageal varices/ hemmorhoids

• hepatorenal syndrome

decreased detox leads to

• mental status change/ asterixis

• gynecomastia/ spider nevi

• jaundice

decreased protein synthesis leads to

• hypoalbumineria

• coagulopathy

alcohol related liver disease

damage to hepatic parenchyma due to consumption of alcohol

fatty liver- accumulation of fats in hepatocytes

alcoholic hepatitis; chemical injury

• acetaldehyde mediates damage

• characterized by swelling of hepatocytes and formation of mallory bodies, necrosis and acute inf

• presents w/ painful hepatomegaly and elevated liver enzymes

cirrhosis is a long term complication

non alcoholic fatty liver disease

fatty changes, hepatitis and/or cirrhosis developping without alcohol exposure OR OTHER KNOWN INSULTS

associated w/ obesity

diagnosis of exclusion

ALT> AST

hemochromatosis

excess body iron → deposition in tissue (hemosiderosis)

hemochromatosis is the organ damage

due to autosomal recessive defect in iron absorption (primary) in HFE/ C282Y gene or chronic transfusion (secondary)

presents in late adulthood

• traid; cirrhosis, secondary DM and bronze skin

• other findings include dilated cardiomyopathy, arrhytmia and testicule atrophy

• high serum ferritin/ iron/ % sat

• low serum TIBC

on biopsy; brown deposits liver 

• prussian blue stain distinguishes iron from lipofuscin (by product from turnover/ wear and tear) of peroxidized lipids

increasec risk of carcinoma

tx; phlebotomy

wilson disease

autosomal recessive defect of ATP7B in atp mediated hepatocyte copper transport

• lack of copper transport into bile and lack of copper incorporation into ceruloplasmin

copper builds up in hepatocytes, leaks in serum and deposits in tissues

• tissue damage due to free radicals

presents w/ cirrhosis, neuro damage and kayser fleisher rings in childhood

increased urinary copper/ serum copper

low serum ceruloplasmin

risk of carcinoma of liver

tx; D penicillamine 

primary biliary cirrhosis

autoimmune granulomatous destruction of intrahepatic bile ducts

• women w/ other autoimmune diseases

w/ antimitochoindrial atb

presents w/ features of obstructive jaundice

cirrhosis a late complication