Gastroenterology 2 Flashcards
What are the 2 blood supplies to the liver? What is the percentage of each?
Portal veins (80%) and Hepatic artery (20%)
What is the venous drainage of the liver?
Central vein → Interlobular vein → Hepatic veins
What does the portal triad consist of?
Portal vein, hepatic artery, bile duct
What liver zone is closest to the portal triad?
Zone 1 (periportal)
What liver zone is closest to the central vein?
Zone 3 (centrilobular zone)
Zone 1 of the liver is affected by which disease first?
Viral hepatitis
Zone 3 of the liver is most vulnerable to what?
Ischemia
Zone 3 of the liver has a high concentration of what enzymes?
P450 enzymes in hepatocytes
Alcoholic liver disease commonly affects what zone of the liver?
Zone 3
The pancreas is formed from the fusion of what 2 structures? Where do they bud off from?
Ventral and dorsal bud; Bud off from endodermal lining of duodenum (foregut)
The Ventral bud of the pancreas forms what?
Part of head, uncinate process, Main pancreatic duct
The Dorsal bud of the pancreas forms what?
Rest of head, Body, tail, accessory duct
Why is the pancreas described as Secondarily retroperitoneal?
Forms covered in peritoneum (intraperitoneal); Later fuses with posterior wall → retroperitoneal
What is an annular pancreas?
Congenital anomaly of ventral bud → 2 lobes wrap around the duodenum in opposite directions forming a ring of pancreatic tissue
Annular pancreas can cause what?
Bowel obstruction
What is Pancreas Divisum?
Dorsal and ventral ducts do not fuse leading to 2 separate ducts (accessory duct drains majority of pancreas)
What is the presentation of Pancreas Divisum? What complication can it cause?
Often asymptomatic; Pancreatitis
What are the 3 major salivary glands?
Submandibular, Parotid, Sublingual
Where are the 3 major salivary glands located?
Submandibular and Sublingual: floor of mouth; Parotid: Behind angle of the jaw, below and in front of ears
The Submandibular gland secretes saliva into what duct?
Wharton’s duct → mouth
Saliva is made of what 6 components?
Mostly water (>90%), Mucin, glycoproteins, IgA antibody, Lysozymes, Lactoferrin
What are 2 functions of Mucin and glycoproteins in saliva?
Lubricate food; Bind bacteria
Saliva is important for what type of immunity?
Innate
2 important enzymes for digestion found in saliva are?
α amylase (digests carbohydrates) and Lingual lipase (digests lipids)
Where is amylase produced?
Saliva and pancreas
The optimal pH for salivary amylase is?
> 6
Lipid digestion is carried out by what 2 enzymes in adults? Which plays a more important role?
Salivary lipase: Minor contributor; Pancreatic lipase: Main lipase
Salivary lipase plays an important role in which demographic?
Newborns (they lower pancreatic enzyme levels)
Salivary fluid is produced by what type of cell and modified by what type of cell?
Acinar cells; Ductal cells
Initial salivary fluid contains what 4 electrolytes? Is it hypotonic, isotonic, or hypertonic compared to plasma?
Na, Cl, K, HCO3-; Isotonic (same concentration as plasma)
How do the ductal cells modify salivary fluid? Are they permeable to water?
Remove Na, Cl; Secrete K, HCO3-; Impermeable to water
As salivary fluid passes the ductal cells, the saliva becomes what?
Hypotonic from removal of Na, Cl
Composition of salivary electrolytes varies with what?
Flow rate
What happens to the composition of salivary electrolytes when there is a higher flow rate? What happens to the [Bicarb]?
Fluid becomes more like plasma because there is less time for ductal modification; [Bicarb] goes up at high flow rates because higher flow = more metabolism = more CO2 in glandular cells → more bicarbonate
What are 2 effects of aldosterone on the salivary glands?
↑ Na absorption; ↑ K secretion
Secretion of saliva is increased by what 2 systems? Which one has a greater effect?
Sympathetic AND parasympathetic; PNS has a greater effect (activated by food, smell, etc.)
What receptors are important in the regulation of saliva?
Muscarinic receptors (M1 and M3)
What are the effects of Muscarinic antagonists on saliva secretion?
Causes dry mouth
What are the effects of Muscarinic agonists on saliva secretion?
Increase saliva production
What is the drug class of Atropine and Scopolamine?
Muscarinic antagonist
What is the drug class of Pilocarpine? What condition is it used to treat?
Muscarinic agonist; Sjogren’s syndrome
Cholinesterase poisoning will have what effect on saliva production?
Increase salivation
What is sialolithiasis?
Salivary duct stones
Sialolithiasis is most common in what gland?
Submandibular
What are 3 risk factors for Sialolithiasis?
Dehydration, Diuretics, Anticholinergic medication
What is the treatment for Sialolithiasis?
Hydration, NSAIDs; rarely surgery
Sialadenitis often occurs secondary to what?
Obstructing stone
What pathogen most often causes Sialadenitis? It often contains what type of pathogen as well?
S. Aureus; Anaerobes
What is the common treatment for Sialadenitis caused by S. Aureus and anaerobes?
Nafcillin (Staph coverage); Metronidazole or Clindamycin (anaerobes)
What is a key feature of mumps?
Parotitis, often bilateral causing facial swelling
Salivary tumors are usually present in which gland? How does it present?
Parotid; Presents as facial swelling
How does a benign salivary tumor present vs an invasive one?
Benign: mobile, painless (not invading the nerve); Invasive: painful (may involve facial nerve → paralysis)
What is the most common salivary gland tumor? How does it usually present?
Pleomorphic Adenoma (benign mixed tumor, rarely undergoes malignant transformation); Painless, mobile mass at the angle of the jaw
What types of cells are found in a Pleomorphic Adenoma?
Epithelial and stromal tissue cells; Epithelial: Glandular cells (left); Stromal: Cartilage, sometimes bone (right)
What is a risk factor for Pleomorphic Adenoma? What is the treatment?
Risk factors: Prior radiation; Treatment: Surgery +/- radiation
Reoccurrence is uncommon in Pleomorphic Adenoma [T/F]. Why?
F; Tumor often has irregular margins and cells are left behind after surgery
What is the second most common salivary tumor?
Warthin’s tumor
What is another name for Warthin’s tumor?
Papillary Cystadenoma Lymphomatosum
Warthin’s tumor usually occurs in what gland?
Parotid
What is a key risk factor for Warthin’s tumor?
Smoking (8x more common)
What are 2 key histological findings seen in Warthin’s tumor?
Cysts surrounded by dense lymphoid infiltrate; Lymph tissue can aggregate into germinal centers
What is the most common malignant salivary tumor?
Mucoepidermoid Carcinoma
What is the key risk factor for Mucoepidermoid Carcinoma? What gland is it normally found?
Prior radiation; Parotid (can cause paralysis and pain)
What 3 cell types are found in Mucoepidermoid Carcinoma?
Squamous (epidermoid) cells, Mucus-secreting cells, Intermediate hybrid cells
Where do hernias commonly occur?
In areas of discontinuity of the abdominal wall i.e. inguinal canal, esophagus, umbilicus
What is the mnemonic for the femoral vessels? What does it stand for?
NAVeL (lateral to medial); Nerve-artery-vein-lymphatics
What are the anatomic borders for the femoral triangle?
Superior: Inguinal ligament; Medial: Adductor longus; Lateral: Sartorius
What is the femoral sheath? What does it contain?
Tunnel of fascia below the inguinal ligament; Femoral vein, artery, and ring (Does not contain nerve)
What is found within the femoral canal?
Lymph vessels and deep inguinal nodes
What is the femoral ring? What is the importance of this landmark?
Opening to femoral canal; Site of femoral hernias
Testes descend through what structure to the scrotum?
Inguinal canal (processus vaginalis)
What is found in the spermatic cord?
Vas deferens, arteries, veins, nerves
What are the 3 fascial layers of the spermatic cord?
External spermatic fascia, Cremasteric fascia, Internal spermatic fascia
The inguinal canal contains what key structure in males vs females?
Males: spermatic cord; Females: round ligament
What structure forms the floor of the inguinal canal?
Inguinal ligament
What is an Indirect Inguinal Hernia? What is the origin in relation to the epigastric vessels?
Abdominal contents travel through inguinal canal (covered by all layers of the spermatic fascia); Origin is lateral to epigastric vessels
What is the Processus Vaginalis? What happens to it during the newborn period and during infancy?
Outpouching of peritoneum where testes descend; Remains open in newborn period and closes in infancy (replaced by fibrous tissue)
After the processus vaginalis is replaced with fibrous tissue, it remains as the what?
Tunica vaginalis testis (serous covering of testes)
If the processus vaginalis fails to close, it may result in what?
Indirect inguinal hernia
Most common type of inguinal hernia is what?
Indirect
Indirect Inguinal Hernia is most common on the what side?
Right (Persistent processus vaginalis more common on right)
Indirect Inguinal Hernias are more common in what demographic?
Men
What are 2 risk factors for indirect inguinal hernia in adulthood? In newborns?
Adults: Heavy lifting, Constipation; Newborns: Mechanical ventilation
What is a Direct Inguinal Hernia? What is the origin in relation to the epigastric vessels?
Bowel bulges ‘directly’ through abdominal wall (Hesselbach’s triangle); Origin is medial to epigastric vessels
What is another name for the external inguinal ring? Where is it located?
Superficial inguinal ring; Terminal end of the inguinal canal, just superior to the pubic tubercle
Direct inguinal hernias are caused by breakdown of what?
Transversalis fascia
Direct Inguinal Hernias are covered by what fascia?
External spermatic fascia only
Direct Inguinal Hernias travel through the what ring?
Superficial/external ring
What are the anatomic boundaries of Hesselbach’s triangle?
Inguinal ligament, Inferior epigastrics, Rectus abdominis; Floor: Transversalis fascia
Direct Inguinal Hernias usually occur in what demographic?
Older men
What is a femoral hernia?
Bowel protrudes through femoral ring below inguinal ligament
Femoral hernias are more common in what demographic?
Women
There is a high risk for what complication in femoral hernia?
Incarceration (bowel trapped in hernia sac since femoral ring is small opening)
What are 2 complications of inguinal hernias?
Incarceration: bowel cannot be reduced; Strangulation: blood flow cut off, bowel becomes ischemic/necrotic → urgent surgery is indicated
How are inguinal hernias usually diagnosed?
Clinically (US/CT sometimes used)
What is the treatment for inguinal hernias?
Surgery: primary closure, mesh placement
What is a ventral hernia? What are 2 subtypes?
Bowel protrusion through ventral abdominal wall; Umbilical, incisional hernias
What is a major risk factor for hiatal hernia?
Obesity
Hiatal hernia can lead to what condition?
GERD
Majority of hiatal hernias are what type?
95% are Type I (sliding hiatal hernia)
What is a Sliding hiatal hernia?
Herniation through hiatus; Displacement of GE junction above diaphragm, fundus remains below GE junction
Sliding hiatal hernia has a what appearance?
Hourglass
What is a Paraesophageal hiatal hernia?
Protrusion of stomach fundus due to defect in ‘phrenoesophageal membrane’; GE junction is in normal location
What is a classic finding in Paraesophageal hiatal hernia?
Bowel sounds in lung fields
What is the cause of congenital diaphragmatic hernia? In utero herniation can lead to what?
Defective formation of pleuroperitoneal membrane → hole in diaphragm; Pulmonary hypoplasia
What is the prognosis of congenital diaphragmatic hernia?
Variable, often poor due to associated pulmonary complications
What is a Paraesophageal hiatal hernia?
Protrusion of stomach fundus due to defect in the phrenoesophageal membrane. GE junction is in normal location.
What is a classic finding in Paraesophageal hiatal hernia?
Bowel sounds in lung fields.
What is the cause of congenital diaphragmatic hernia?
Defective formation of pleuroperitoneal membrane leading to a hole in diaphragm.
What can in utero hernation lead to?
Pulmonary hypoplasia.
What is the prognosis of congenital diaphragmatic hernia?
Often fatal.
What is bile made of?
Mostly water, phospholipids, electrolytes, bile salts, and bilirubin.
What is a triglyceride made of?
1 glycerol and 3 fatty acids.
Bile salts act as _____?
Surfactant.
How are bile salts formed?
Taurine and glycine conjugated to bile acids (cholic acid, chenodeoxycholic acid) to form bile salts.
Where are bile acids synthesized?
Only in liver (>90% classic pathway, <10% acidic pathway).
What is the rate limiting enzyme in the classic pathway of bile acid synthesis?
7-α hydroxylase.
What does 7-α hydroxylase require?
Cytochrome P450 enzymes, NADPH, and oxygen.
Where does most lipid absorption occur?
In the jejunum.
Bile salts undergo ______?
Enterohepatic circulation.
What are the two outcomes of bile salts?
95% absorbed and recycled, 5% excreted in stool.
Where are bile salts absorbed?
By active transporters in the terminal ileum.
What are three functions of bile salts?
Emulsification of fats, excretion of cholesterol, and antimicrobial activity.
How is cholesterol excreted from the body?
Convert cholesterol to bile salt (conjugated bile acid) and excrete in stool.
What are three bile acid resins?
Cholestyramine, colestipol, colesevelam.
What is the function of bile acid resins?
Retains bile acids in the stool to prevent reabsorption.
What is the mechanism by which bile salts prevent bacterial overgrowth?
Disrupts bacterial cell membranes.
What is cholestasis?
Disrupted bile flow to intestines.
What are two lab findings in cholestasis?
Direct (conjugated) hyperbilirubinemia and elevated alkaline phosphatase (ALP).
What are four symptoms of cholestasis?
Jaundice, pruritus, dark urine, and clay-colored stools.
What are two long term consequences of cholestasis?
Fat malabsorption and decreased fat soluble vitamins.
Alkaline Phosphatase is produced by what cells?
Bile duct epithelial cells.
Bile obstruction leads to an increase or decrease in Alkaline Phosphatase?
Increase.
What are the levels of alk phos and AST/ALT in cholestasis?
↑ alk phos»_space; ↑ AST/ALT.
What does ↑ AST/ALT»_space; ↑ Alk Phos indicate?
Primary abnormality relates to hepatocytes.
What does ↑ Alk Phos»_space; ↑ AST/ALT indicate?
Primary abnormality relates to bile ducts.
What is the best first test for cholestasis?
Right upper quadrant ultrasound.
What are normal AST/ALT and Alk phos levels?
AST/ALT: ~50IU/L, Alk phos: ~100 IU/L.
What are three extrahepatic causes of cholestasis?
Gallstone, pancreatic mass, biliary strictures.
What are four intrahepatic causes of cholestasis?
Primary biliary cirrhosis, cholestasis of pregnancy, contraceptives, erythromycin.
Describe Heme metabolism.
Heme is released from old RBCs, macrophages convert it to bilverdin, then to bilirubin.
Bilirubin is carried by what protein in the blood?
Albumin.
What enzyme conjugates bilirubin in the liver?
UDP glucuronyltransferase.
What does UDP glucuronyltransferase add to unconjugated bilirubin?
Glucuronic acid, forming bilirubin monoglucuronide and bilirubin diglucuronide.
What is conjugated bilirubin also called?
Bilirubin diglucuronide.
What is the purpose of bilirubin conjugation?
Produces more water soluble compounds that facilitate excretion with bile.
What are two functions carried out by bacteria in bilirubin metabolism?
Convert unconjugated bilirubin back and produce urobilinogen.
What is the fate of the majority (80-90%) of urobilinogen?
Converted to stercobilin and excreted in feces.
What happens to the urobilinogen not excreted in feces?
Reabsorbed by intestines and taken up by liver, small amount converted to urobilin.
What is the Van den Bergh reaction?
Coupling of bilirubin with a diazonium salt to form a colored complex.
Can serum conjugated bilirubin directly undergo the Van den Bergh reaction?
Can.
Can serum unconjugated bilirubin directly undergo the Van den Bergh reaction?
Cannot.
What are the levels of bilirubin (conjugated) and urobilinogen in a normal urine dipstick?
Bilirubin: Normal absent, Urobilinogen: Normally a small amount.
What is the earliest sign of jaundice?
Scleral icterus.
What is a normal total bilirubin level and at what level does jaundice appear?
Normal: <1.0 mg/dL, Jaundice: >3mg/dL.
What are four possible causes of dark urine?
Hematuria, rhabdomyolysis, elevated conjugated bilirubin, dehydration.
What are three general causes of increased bilirubin?
Hemolysis, biliary obstruction, liver disease.
What three lab findings are present in hemolysis hyperbilirubinemia?
Increased unconjugated bilirubin, no urine bilirubin detected, increased urobilinogen.
What are four lab findings present in biliary obstruction hyperbilirubinemia?
Elevated serum direct bilirubin, urine bilirubin detected, ↑ AlkP, absent urobilinogen.
Why is bilirubin fractionation unreliable for liver disease?
Often mixed increase of direct/indirect.
Name two primary liver diseases that can cause unconjugated hyperbilirubinemia.
Chronic hepatitis, advanced cirrhosis.
Name three primary liver diseases that can cause conjugated hyperbilirubinemia.
Viral hepatitis, alcoholic hepatitis, NASH.
How do urobilinogen levels present early vs late in primary liver disease?
Early: increase, Late: decrease.
How does rifampin cause hyperbilirubinemia?
Competes with bilirubin for uptake by liver, blunt hepatic uptake of unconjugated bilirubin.
What enzyme is defective in Gilbert’s Syndrome?
UDP-glucuronyltransferase.
What is the clinical presentation of Gilbert’s Syndrome?
Jaundice can occur with increased bilirubin production, no serious clinical consequences.
What is Crigler-Najjar Syndrome?
Severely reduced/absent UGT enzyme leading to inability to conjugate bilirubin.
What is the clinical presentation of Crigler-Najjar Syndrome Type I?
Usually presents in infancy with jaundice and kernicterus.
What type of bilirubin can cause Kernicterus?
Unconjugated.
How does unconjugated bilirubin cause Kernicterus?
It is fat soluble and can cross the blood-brain barrier, acting as a neurotoxin.
Crigler-Najjar Syndrome Type II is less severe compared to which type?
Crigler-Najjar Syndrome Type I.
What is the treatment for Crigler-Najjar Syndrome Type II?
Phenobarbital or clofibrate to induce liver glucuronidation.
What is Dubin-Johnson Syndrome?
Defective liver excretion of conjugated bilirubin due to an abnormal gene.
What are three findings in Dubin-Johnson Syndrome?
↑ conjugated bilirubin, bilirubin in urine, liver turns black.
What is the treatment for Dubin-Johnson Syndrome?
No treatment required, benign condition.
What is Rotor’s syndrome?
Similar to Dubin-Johnson but milder with impaired liver excretion of conjugated bilirubin.
What differentiates Rotor’s syndrome from Dubin-Johnson?
No black liver.
