Transcript GI Function and Disorders

Lecture Topic: “GI Disorders”
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Describe the mechanical and chemical basis of motility,
absorption, and digestion in the GI tract.
Describe the physiological mechanisms involved in
anorexia, nausea, and vomiting.
List the causes of esophagitis.
Relate the causes of hiatal hernia to measures used in
treatment of the condition.
Describe the predisposing factors in development of
peptic ulcers.
Compare the pharmacologic actions of antacids,
histamine-receptor antagonists, and mucosal protective
agents as they relate to the treatment of peptic ulcer.
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Objectives (cont.)
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Compare the characteristics of Crohn’s disease and
ulcerative colitis.
Describe the causes and manifestations of peritonitis
and bowel obstructions.
List the risk factors for colorectal cancer and screening
methods as suggested by the American Cancer Society.
Describe the various causes of diarrhea.
Describe the pharmacologic action of opiates,
anticholinergics, and fiber in the treatment of diarrhea.
Describe the pharmacological action of stool softeners,
saline and stimulant cathartics, and bulk-forming
laxatives in the treatment of constipation.
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Terms
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Digestion
Absorption
Peristalsis
Peritoneum
Mesentery
Peritonitis
Ascites
Vagus nerve
Mechanoreceptors
Chemoreceptors
Aspiration pneumonia
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Gastrin
Chyme
Cholecystokinin
Dumping syndrome
Chief cells
Parietal cells
Intrinsic factor
Goblet cells
Lactase deficiency
Fat-soluble vitamins
Steatorrhea
Anorexia
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Terms
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Appendicitis
Paralytic ileus
Hematemesis
Melena
Occult blood
Dysphagia
Esophagitis
Hiatal hernia
Gastritis
Peptic ulcer
Gastroscopy
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Phenothiazines
 Compazine
 Thorazine
Antacids
Histamine antagonists
(H2 blockers)
Inflammatory bowel
disease
 Crohn’s
 Ulcerative colitis
Toxic megacolon
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Manifestations of GI Disorders
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Anorexia, Nausea, & Vomiting
 Protective
function by removing noxious
agent
 Contributes to nutritional, fluid, & electrolyte
abnormalities
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Anorexia = loss of appetite
 Hypothalamus
 Smell
 Drugs
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Manifestations (cont.)
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Nausea = unpleasant subjective sensation
 Stimulated by distention, food, or drugs
 Accompanied by pallor, sweating, & tachycardia
(vasoconstriction)
Vomiting = forceful expulsion of contents of
stomach
Vomiting Center - coordination of act in medulla; direct
stimulation by hypoxia, inflammation, & distention
 CTZ - stimulated by drugs & toxins; bradycardia, BP,
dizziness
 Phenothiazines - decreased stimulation of CTZ
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Manifestations - GI Bleeding
 Melena
- blood in stool
 Hematemesis - blood in vomitus;
bright red or “coffee-grounds”
 Occult blood - “hidden blood”,
elevation of BUN
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GI Tract - Structure &
Function
A hollow tube / Outside of Body!!!
 Digestion - breakdown of foodstuffs
 Absorption - passage of nutrients into
bloodstream
 Main organs
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 Esophagus,
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stomach, & intestine
Accessory organs
 Teeth/tongue,
salivary glands, liver, pancreas,
& gallbladder
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Digestion & Absorption Function
GI tract - largest endocrine organ in
body; hormones influence motility &
secretion of electrolytes & enzymes
 ANS control of propulsion (peristalsis)
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 Parasympathetic
(Vagus) - speeds up
 Sympathetic - slows down
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Muscle control through “sphinctors”
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Digestion and Absorption
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Saliva & Stomach - begin breakdown of
starches & lipid-soluble foodstuffs
Lysozymes & HCL - antibacterial action
Small intestine - Villi provide LARGE
absorptive surface area
CHO - disaccharides converted to
monosaccharides by brush border enzymes
 Fat - broken down by lipases & bile; fat-soluble vits
(A, D, E, K); steatorrhea = fatty stools
 Protein - broken down by pancreatic enzymes
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GI Motility
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Swallowing
 Coordinated
by medulla & pons
 Esophagus - opening of LES -- vagal
control (e.g. acetylcholine increases
constriction)
 CANNOT SWALLOW AND BREATHE AT
SAME TIME
 Dysphagia = difficulty swallowing
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Motility (cont.)
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Stomach
 Acts as reservoir
 Emptying - Hormonal (CCK) & neural
mechanisms
 Pyloric stenosis - infants or scarring
Small intestines
peristalsis - synchronized contraction & relaxation as
food bolus moves through; 12/min in jejunum
 Inflammation - increase in bowel sounds
 Surgery - Decrease in peristalsis
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GI Motility (cont.)
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Colon
 Compaction of fecal wastes
 Haustrations - mixing movements
 Mass propulsion -- defacation
 Gastrocolic reflex- wave of
peristalsis following fasting period
(usually overnight)
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Disorders of Esophagus
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Esophagitis - inflammation of mucosa
Acute causes
 ingestion of alkalis or acids
 infections such as candidiasis
 Scarring as possible sequelae
Chronic causes - reflux or local irritants
 Decrease in LES pressure
 Acid reflux
 Increase in dietary fat
 Often result of Hiatal hernia
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Hiatal Hernia
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Protrusion of stomach into chest cavity
Etiology - muscle weakness; constipation
Sliding hernia
 Tx: Small, frequent meals; antacids; no
anticholinergics (decrease LES); avoid
nicotine; metoclopramide (Reglan)
Rolling hiatal hernia
 Strangulation is a potential problem!
Complications: GERD and strictures
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GERD
Most common disorder of GI tract
 Weak or incompetent LES, meals high
in fat
 Heartburn – often during night
 Other symptoms include wheezing,
cough, & hoarseness
 Link between GERD & asthma – vagalmediated bronchospasm, laryngeal
injury, microaspiration
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Tx of GERD
Conservative: sitting up while eating and
several hours afterward; avoidance of
high-fat meals, smoking, alcohol,
chocolate, caffeine; bending for long
periods of time; sleeping with HOB
elevated, weightloss
 Pharmacological : antacids for mild
disease; alginic acids, H2 blockers,
Proton pump inhibitors for severe
disease or strictures
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Peptic Ulcer
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Ulceration of mucosa in UGI
 Gastric vs. duodenal
Pathogenesis
 Agents: aspirin, alcohol, & H. pylori
 Destruction of mucosal barrier:
 Decrease in blood flow & bicarbonate (shock, smoking)
 Increased permeability to H+ (alcohol & aspirin)
 Decreased prostaglandins (aspirin)
 Increased sympathetic stimulation which inhibits Brunner’s
glands & mucous secretion
 Increased HCL production (histamine and gastrin secreting
tumors e.g. Zollinger-Ellison Syndrome)
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Ulcers (cont.)
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Manifestations
 Gnawing, burning pain
 Pain on empty stomach
 Pain relieved by food or antacids
Complications
 Hemorrhage
 Obstruction
 Perforation
Diagnosis
 H & P, UGI, Endoscopy
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Ulcers - Drug Management
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Antacids
 Give
30 mins. after meals
 Calcium -- constipating effect
 Neutralize pH
 Magnesium - laxative effect
 Aluminum - phosphate binders
 Alter absorption of many drugs!!!
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Ulcers - Drug Management
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Mucosal Protective Agents
 Sucralfate
(carafate)
 Polysaccharide
 Selectively binds to necrotic ulcer
 Requires acid pH for activation!!
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Anticholinergics
 Blocks
vagal stimulation of gastric acid
 Decrease GI motility
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Ulcers - Drug Management
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H2 receptor antagonists
 Blocks receptor for histamine &
gastric secretion of HCL (ex. ranitidine
(Zantac); Cimetidine (Tagamet);
Pepcid; Axid
 Liver toxicities !!!
 Psychosis/Delirium !!!
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Inflammatory Bowel
Disorders
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Chron’s & Ulcerative Colitis
Hereditary predisposition
 Early adulthood
 Remissions & exacerbations
 Diarrhea
 Weight loss
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Possible complications
 Obstruction
 Fistulas
 Toxic megacolon
 Cancer
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Chron’s Disease
Mainly affects small intestine (submucosal
layer)
 Granulomatous lesions - “cobblestone”
 Bowel - “lead-pipe rigidity”
 Nutritional deficits
 Formation of fistulas & abscesses
 Symptoms
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 Intermittent
diarrhea; colicky pain, weight loss,
F & E abnormalities; malaise; low-grade fever
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Ulcerative Colitis
Mainly confined to rectum & colon
 Spreads upward
 Primarily affects mucosal layer
 Pseudopolyps
 Symptoms:
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 Up
to 30-40 bloody, mucousy stools/day
 Fever & anorexia
 Abdominal cramping
 Weakness & fatigue
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Inflammatory Bowel Disease Diagnosis & Treatment
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Diagnosis
 Sigmoidoscopy
 Barium
enema (Chron’s)
 CT scan
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Treatment
 Sulfasalazine
 Corticosteroids
 Surgery
-- ileostomy
 Hi cal, Hi prot, Hi vit diet
 Elemental diet
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Diverticulosis
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Herniation of intestinal wall
Risk factors:
 Inactivity
 Low-fiber diet
 H/O constipation
 Symptoms
 Often asymptomatic
 Bloating/flatulence
 Diarrhea/Constipation
Treatment - Bulk in diet
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Diverticulitis
Complication of diverticulosis
 Inflammation & infection
 LLQ pain, N & V, leukocytosis
 Treatment:
 Antibiotics
 No SOLID food
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Colorectal Cancer
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2cnd most common fatal cancer!!
Risk factors:
 Advancing age
 Family history
 Diet low in fiber, Hi in refined sugar
 H/O colorectal polyps
Dx:
 Rectal exam; + occult blood; barium enema;
sigmoidoscopy
Tx: Surgery; pre-op radiation
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Appendicitis
Inflammation of appendix
 Causes: fecalith or twisting ??
 Symptoms:
 Epigastric pain -- colicky--LRQ pain
 Abrupt onset
 Nausea
 Fever
 Leukocytosis
 Rebound tenderness
 Tx: Surgery
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Bowel Obstruction
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Mechanical
 Post-op
adhesions
 External hernia
 Intussusception
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Paralytic
 Abdominal
surgery -- paralytic ileus
 Back injuries
 Pelvic fractures
 Inflammatory conditions
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Bowel obstructions (cont.)
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Manifestations
 Distention
F
& E disturbances
 Borborygmis
 Visible peristalsis
 Vomiting (projectile)
Dx: H & P; gas-filled bowel
 Tx: NG decompression; surgery
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Peritonitis
Inflammation of abdominal cavity
 Causes:
 Perforated peptic ulcer
 Ruptured appendix/diverticulum
 PID
 Gangrenous gallbladder
 Trauma
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Peritonitis (cont.)
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Symptoms:
 Pain
& tenderness
 Guarding
 Shallow breathing
 Hiccups
 Paralytic ileus
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Treatment:
 NG
decompression; NPO; antibiotics; F & E
replacement
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