GI Pathophysiology

Normal Digestion

Digestive system:
Alimentary tract/ gut
Long hollow tube through the gut
Accessory structures: salivary glands, liver, gallbladder, pancreas
Upper: mouth, esophagus, stomach
Lower: intestines
Inside the gut food, fluid, secretions processed

*First broken down
*Then nutrients, water, electrolytes absorbed into blood for cells and wastes collected

Upper GI tract:
Swallowing, cranial nerves V, IX, X, XII
Epiglottis covers larynx
Respiration ceases
Food > esophagus > stomach

Expandable muscular sac
Capacity 1 – 1.5 liters food/fluid
Empty stomach walls fold into rugae
Gastric glands have parietal cells that secrete hydrochloric acid (ph 2)
Parietal cells also excrete intrinsic factor to absorb B12
Chief cells secrete pepsinogen
Food + secretions =chyme
Gastric empties slowly, 1-3 ml pass into the duodenum

Secretions from the liver and exocrine pancreas added to chyme


Liver: This is one busy organ!!!
Metabolic factory
Liver reassembles nutrients into materials needed by the body
Large organ covered by fibrous capsule (distention cause pain)
Liver cells can regenerate but may not function correctly
As blood flows through the liver nutrients are gathered for storage
Minerals iron, copper, vitamins A, B6, B12, D, K and folic acid
Blood components are monitored as blood circulates through
Iron and amino acids replaced as needed
Blood glucose levels maintained
High levels of blood glucose are converted to glycogen (glycogenesis)
Low levels of blood sugar lead to breakdown of glycogen (glycogenolysis)
Gluconeogenesis conversion of fat and protein into glucose
Conversions of needed amino acids
Synthesis and control of clotting factors, lipoproteins, cholesterol for steroids
Aldosterone and estrogen are inactivated and prepared for excretion
Ammonia (nitrogen wasted resulting from protein metabolism) > urea
Drugs and alcohol are detoxified
Damaged or old erythrocytes removed, iron, protein recycled
Blood reservoir (can release large amounts of blood as needed in emergency)
Produces bile necessary for digestion, vehicle for removal of bilirubin, cholesterol
Bile salts necessary for breakdown of fat soluble vitamins A, D, E, K
Gallbladder is a bile storage facility

Pancreas: Endocrine gland and digestive organ!
Exocrine pancreas, digestive organ,
Cells secrete digestive enzymes, electrolytes, water into small intestine

Lower digestive tract:
3 sections duodenum, jejunum, ileum
Digestion continues in the duodenum where enzymes added and ph alkaline
Ileum is where nutrients are absorbed
Ileum contains large amounts of lymphoid tissue, Peyer’s patches
Villi and microvilli tiny projectiles which increase surface absorption area
Ileocecal valves is where the small intestine enters the large intestine
At this point is a pouch… appendix

Large intestine:
Absorption of large amounts of water and electrolytes
Ascending, transverse, descending colon
Sigmoid colon, rectum, anal canal ending with the anus
Feces consists of fiber, sloughed mucosal cells, bacteria
Rectum stores feces until distention stimulates the defecation reflex

Anorexia loss of appetite
Nausea unpleasant subjective feeling
Vomiting emesis – forceful expulsion of chyme, vomiting center in the medulla
Vomiting activated by:
Unpleasant sights or smells, ischemia
Pain, stress
Increased intracranial pressure
Inner ear disturbance
Stimulation of medulla by drugs, toxins, chemicals
Drugs or toxins of digestive mucosa

Characteristics of vomitus:
Presence of blood – hematemesis – coffee grounds
Yellowish, greenish bile from duodenum
Deeper brown from lower intestine – obstruction

Excessive frequency of stools, loose watery consistency
Presence of blood, mucous pus important diagnostic information
Large volume diarrhea often from infection
Small volume diarrhea w/ blood, mucous, pus = inflammatory bowel disease
Steatorrhea – fatty diarrhea, bulky, greasy, loose stool (malabsorption syndrome)

Blood in stool
Frank – red blood
Occult – hidden
Melena – dark colored stool from bleeding higher in digestive tract

Bowel patterns individualistic and influenced by diet, activity
Increased age, weakness of smooth muscle
Inadequate fiber
Inadequate fluid
Failure to respond to defecation reflex
Muscle weakness, inactivity
Neurological disorders
Drugs, opiates
Antacids, iron meds
Obstruction caused by tumors
Chronic constipation can lead to fecal impaction

Fluid and electrolyte
Dehydration and hypovolemia complications of GI disturbances
Na+ lost in vomiting and diarrhea
K+ lost with diarrhea
Acid base imbalances
Vomiting leads to a loss of hydrochloric acid resulting in metabolic alkalosis
Severe vomiting change to metabolic acidosis duodenal secretions w/ bicarbonate lost

Upper digestive burning sensation w/ inflammation and ulceration
Visceral pain fibers autonomic nervous system, pallor, nausea, vomiting
Dull aching pain RUQ stretching liver capsule
Cramping, diffuse pain inflammation, distention of intestines
Colicky pain from smooth muscle spasm, inflammation obstruction, ex. Gallstone
Somatic pain receptors linked to spinal nerves cause reflex spasm
Referred pain – perceived pain is distant from the origin

Specific or general
B12 deficiency due to no intrinsic factor
Iron deficiency due to malabsorption, diet, liver damage or bleeding
Wasting syndrome
Special, fad diets

Diagnostic tests:
Radiographs w/ contrast medium
Fiberscoptic endoscopy, sigmoidoscopy, colonoscopy
Stool specimens
Gastric washings
Blood tests, liver function,

Common therapies:
Dietary modifications – gluten free diet, reduce alcohol, coffee
Stress reduction
Antacids, acid reduction, laxatives,
Antiemetics, antidiarrheals, antimicrobial, anti-inflammatory
Coating agents

Gastroesophageal reflex (GERD)
Flow of gastric contents into the esophagus
Often w/ hiatal hernia
Severity depends on sphincters
Episodes of heartburn 30-60 minutes after eating
Reflux leads to inflammation, ulceration, fibrosis, stricture
Eliminate caffeine, alcohol, fatty foods, cigarettes
Avoid spicy food, meds may help

Gastric mucosa red, inflamed, edematous
May be ulcerated and bleeding
Infection, virus or bacteria
Food allergies
Spicy, irritating foods
Excessive alcohol intake
Ingestion of aspirin, corrosive, toxic substances
Radiation, chemotherapy

Gastroenteritis (Oh, no, ughhhhhhhh)
Involvement of stomach and intestines in an inflammatory process
Usually infection but can be allergy
Inflammation stimulates vomiting
Inflammation of intestines increases motility
Fever, malaise
Microbes in fecally contaminated food/water
Some seasonal, rotaviruses, winter months
Careful handwashing and food handling vital
Common infections transmitted by food and water:

Clostridium difficile C-diff – gram + bacillus, spore until reaches intestine
Escherichia coli E coli – normal resident, some types secrete enterotoxin
Norwalk virus
Clostridium botulinum

Peptic ulcers:
Stomach or duodenum
*Normally mucosal barrier epithelial cells that regenerate quickly covered by athick layer of bicarbonate rich mucous
Factors contributing to breakdown:
Bacterium Helicobacter pylori, H pylori, secretes cytotoxins, enzymes damage mucosa
In adequate blood supply stress, smoking, shock, poor diet, alcohol intake
Excessive glucocorticoid or med predisone
Ulcerogenic agents – aspirin, NSAIDS
Chronic gastritis
Ulcer can erode a blood vessel causing hemorrhage
Perforation > peritonitis
Obstruction – stricture, scar

Burning, aching 2-3 hours after meals
Relieved by ingestion of food, antacids
Iron deficiency anemia
Nausea, vomiting, heartburn, weight loss

Diet changes, habits
Antimicrobials – tetracycline, clarithromycin
Acid reducing meds – Tagamet (H2 receptor/antagonist), prilosec (proton pump inhibitor)
Surgery gastrectomy, pyloroplasty

Cholelithiasis gallstones
Cholecystitis – inflammation of gallbladder
Cholangitis – inflammation related to infection
Choledocholithiasis – obstruction

Obesity, multiparity, high cholesterol, 3Fs …forty, fat, fertile
Colicky pain RUQ
Nausea, vomiting
Acute - Obstruction, infection, rupture
Chronic – intolerance of fatty foods, belching, bloating, mild epigastric ache

Inflammation of pancreas, autodigestion
Premature activation of the pancreatic enzymes in pancreas itself
Gallstones, alcohol abuse

Severe epigastric pain worse when lying
Signs of shock
Low grade fever
Abdominal distention, decreased bowel sounds

Oral intake stopped
Bowel distention relieved
Shock, electrolytes replaced

Hepatitis with a vowel comes from the bowel!
Inflammation of liver
Idiopathic (fatty liver)
Infection (hepatitis)
Viruses result in cell inflammation and necrosis
Hepatic cells may regenerate or fibrous scar tissue develop

Mild to severe
Preicteric stage:
Fatigue, malaise, anorexia, nausea, muscle aches, RUQ pain
Icteric stage:
Stools lighter, urine darker, skin pruritic
Liver enlarged, tender, achy
Blood clotting impaired
Reduction in signs

Progressive destruction of liver tissue
Congenital, genetic disorders or metabolic

Alcoholic liver disease
Biliary cirrhosis immune disorders
Post necrotic cirrhosis, chronic hepatitis, exposure to toxic chemicals
Metabolic disorders – hemachromatosis
Damage related to inflammation, necrosis, fibrosis

Fatigue, anorexia, weight loss, anemia, diarrhea
Dull ache URQ
Frequent infections, delayed healing,

Malabsorption syndrome
Genetic link
Lack of intestinal enzyme which breaks down gluten (wheat, barley, rye, oats)
Gluten free diet

Chronic Inflammatory Bowel Disease:

Crohn’s disease
Genetic link
Similarities with ulcerative colitis
Chrohns often develops during adolescence
Characterized by remissions/exascerbations
Primarily small intestines, skip lesions
Inflammation leads to thick, ‘rubber hose’ wall, narrow lumen, obstruction
Inflammation increases intestinal motility, decreases absorption
Hypoproteinemia, avitaminosis, steatorrhea
Adhesions, ulcers, abscesses

Diarrhea, cramping,
Pain, tenderness RLQ
Anorexia, weight loss, fatigue, malnutrition, delayed growth and development

Ulcerative colitis
Inflammation begins in rectum and progresses back through colon
Small intestine rarely involved
Tissue edematous, ulcerations develop
Granulation tissue forms, vascular, fragile, bleeds easily
Tissue destruction interferes with absorption of fluid and electrolytes
Concern with megacolon and possible dysplasia leading to colon cancer

Diarrhea, cramping, blood, mucous
Severe episodes blood and mucous alone passed
Tenesmus – frequent urge to defecate
Rectal bleeding, anemia, weight loss

Limit stress
Meds – anti-inflammatories, glucocorticoids
Antimotility agents
Nutritional supplements TPN may be needed
Antimicrobials for secondary infections
Immunotherapeutic agents
Ileostomy or colostomy

Inflammation of the vermiform appendix
Obstruction with gallstone, or fecalith
Fluid builds up w/ microbial growth
Appendiceal wall inflamed, exudate, decreased venous exchange = ischemia
Abscess formation or perforation and rupture into peritoneal cavity

Periumbilical pain > to RLQ pain
Nausea, vomiting
After rupture pain subsides
Low grade fever, leukocytosis
Peritonitis = ‘boardlike’ abdomen, tachycardia, hypotension
Surgical removal w/ antibiotics

Inflammation of peritoneal membrane chemical irritation or bacterial invasion
Peritoneum large expanse sterile vascular tissue
Inflammation provides means for dissemination throughout the abdominal cavity
Membrane becomes edematous, red, leaky from the many blood vessels
Leaking large amounts of fluids into peritoneal cavity = third spacing
Fluid becomes purulent
Nausea, vomiting
Obstruction, ileus

Pain esp. w/movement, pt restricts breathing
Dehydration, hypovolemia
Low blood pressure (hypotension)
Abdominal distention, rigid abdomen
Decreased bowel sounds = ileus or obstruction

Surgery, drains
NG suctioning to V distention


Gould, B. E., & Dyer, R. M. (2011). Pathophysiology for the health professions (4 ed.). St. Louis, Missouri: Saunders Elsevier.

Story, L. (2012). Pathophysiology: A practical approach. Sudbury, MA: Jones & Bartlett Learning .


Normal Digestion


GERD/Hiatal hernia




Celiac disease


Ulcerative colitis