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236 GI disorders 02/27/01 1
Lecture Topic: “GI Disorders”
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.) 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
Digestion Absorption Peristalsis Peritoneum Mesentery Peritonitis Ascites Vagus nerve Mechanoreceptors Chemoreceptors Aspiration pneumonia
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 Appendicitis Paralytic ileus Hematemesis Melena Occult blood Dysphagia Esophagitis Hiatal hernia Gastritis Peptic ulcer Gastroscopy
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
Anorexia, Nausea, & VomitingProtective function by removing noxious
agentContributes to nutritional, fluid, & electrolyte
abnormalities Anorexia = loss of appetite
HypothalamusSmellDrugs & disease
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Manifestations (cont.) Nausea = unpleasant subjective sensation
Stimulated by distention, food, or drugsAccompanied 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
Esophagus, 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)Parasympathetic (Vagus) - speeds upSympathetic - slows down
Muscle control through “sphinctors”
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Digestion and Absorption
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
SwallowingCoordinated by medulla & ponsEsophagus - 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.)
StomachActs as reservoirEmptying - Hormonal (CCK) & neural
mechanismsPyloric 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.)
ColonCompaction of fecal wastesHaustrations - mixing movementsMass propulsion -- defacationGastrocolic reflex- wave of
peristalsis following fasting period (usually overnight)
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Disorders of Esophagus
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 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 herniaStrangulation 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 – vagal-
mediated 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
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.) Manifestations
Gnawing, burning painPain on empty stomachPain relieved by food or antacids
ComplicationsHemorrhageObstructionPerforation
DiagnosisH & P, UGI, Endoscopy
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Ulcers - Drug Management
AntacidsGive 30 mins. after mealsCalcium -- constipating effectNeutralize pHMagnesium - laxative effectAluminum - phosphate bindersAlter absorption of many drugs!!!
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Ulcers - Drug Management
Mucosal Protective AgentsSucralfate (carafate)PolysaccharideSelectively binds to necrotic ulcerRequires acid pH for activation!!
AnticholinergicsBlocks vagal stimulation of gastric acidDecrease GI motility
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Ulcers - Drug Management
H2 receptor antagonistsBlocks 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
Chron’s & Ulcerative Colitis Hereditary predisposition Early adulthood Remissions & exacerbations Diarrhea Weight loss
Possible complicationsObstructionFistulasToxic megacolonCancer
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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
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:
Up to 30-40 bloody, mucousy stools/dayFever & anorexiaAbdominal crampingWeakness & fatigue
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Inflammatory Bowel Disease - Diagnosis &
Treatment Diagnosis
SigmoidoscopyBarium enema (Chron’s)CT scan
TreatmentSulfasalazineCorticosteroidsSurgery -- ileostomyHi cal, Hi prot, Hi vit dietElemental diet
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Diverticulosis Herniation of intestinal wall Risk factors:
InactivityLow-fiber dietH/O constipation
SymptomsOften asymptomaticBloating/flatulenceDiarrhea/Constipation
Treatment - Bulk in diet
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Diverticulitis
Complication of diverticulosis Inflammation & infection LLQ pain, N & V, leukocytosis Treatment:
AntibioticsNo SOLID food
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Colorectal Cancer 2cnd most common fatal cancer!! Risk factors:
Advancing ageFamily historyDiet low in fiber, Hi in refined sugarH/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 painAbrupt onsetNauseaFeverLeukocytosisRebound tenderness
Tx: Surgery
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Bowel Obstruction Mechanical
Post-op adhesionsExternal hernia Intussusception
ParalyticAbdominal surgery -- paralytic ileusBack injuriesPelvic fractures Inflammatory conditions
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Bowel obstructions (cont.)
ManifestationsDistentionF & E disturbancesBorborygmisVisible peristalsisVomiting (projectile)
Dx: H & P; gas-filled bowel Tx: NG decompression; surgery
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Peritonitis
Inflammation of abdominal cavity Causes:
Perforated peptic ulcerRuptured appendix/diverticulumPIDGangrenous gallbladderTrauma
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Peritonitis (cont.) Symptoms:
Pain & tendernessGuardingShallow breathingHiccupsParalytic ileus
Treatment:NG decompression; NPO; antibiotics; F & E
replacement
