Lecture 11: Alteration in digestive function

clinical manifestations of gastrointestinal dysfunction

• anorexia

  • anorexia is a lack of a desire to eat despite physiologic stimuli that would normally produce hunger

• vomiting

  • vomiting is the forceful emptying of the stomach and intestinal contents through the mouth

  • several types of stimuli initiate the vomiting reflex

  • chemoreceptor trigger zone (ctz) for vomiting is in the medulla oblongata

  • 5-hydroxytryptamine (5-ht, aka serotonin) stimulates the emetic center

  • antiemetics, such as ondansetron and granisetron block the effects of 5-ht serotonin and are used to treat vomiting and nausea

• nausea

  • nausea is a subjective experience that is associated with a number of conditions

  • the common symptoms of vomiting are hypersalivation and tachycardia

• projectile vomiting

  • projectile vomiting is spontaneous vomiting that does not follow nausea or retching

  • it is caused by direct stimulation of the vomiting center by neurologic lesions involving the brainstem

• constipation

  • constipation is defined as infrequent or difficult defecation

  • normal bowel habits range from two or three evacuations per day to one per week

  • pathophysiology

    • neurogenic disorders, functional or mechanical conditions, low residue diet, sedentary lifestyle, excessive use of antacids, changes in bowel habits

• diarrhea

  • increased frequency of bowel movements

  • increased volume, fluidity, weight of the feces

  • more than three stools per day is considered abnormal (diarrhea)

  • adult intestine processes approximately 9L (2L ingested and 7L is intestinal secretion) of luminal content per day, of which 99% of the fluid is normally reabsorbed

  • with losses of more than 1000mL or more, the heart rate is greater than 100bpm and systolic bp is less than 100 mmhg

  • major mechanisms of diarrhea

    • osmotic diarrhea- nonabsorbable substance in the intestine draws water into the lumen by osmosis

      • if a person lacks the enzyme lactase and ingests lactose, the lactose will not be hydrolyzed and absorbed into the intestinal wall and result osmotic diarrhea

    • secretory diarrhea- large volume diarrhea caused by excessive mucosal secretion such as chloride

      • cholera is a form of secretory diarrhea

    • motility diarrhea- caused by resection of small intestine or surgical bypass of an area of the intestine

• abdominal pain

  • abdominal pain is a symptom of a number of gi disorders

  • the casual mechanisms of abdominal pain are mechanical, chemical mediators of inflammation, or ischemic

    • chemical mediators, such as histamine, bradykinin, and serotonin produce abdominal pain

    • edema and vascular congestion produce abdominal pain by stretching

    • ischemia caused by distention of bowel obstruction or mesenteric vessel thrombosis produce abdominal pain

  • abdominal pain can be

    • parietal pain- arise from parietal peritoneum

      • the pain is more localized and intense

    • visceral pain- arise from stimulus acting on abdominal organ

      • visceral pain is diffuse, vague, poorly localized, and dull

    • referred pain- pain felt at some distance from disease or an affected organ ex. intense gallbladder pain is felt btwn the shoulder blades

      • pain is well localized

• gastrointestinal bleeding

  • upper gastrointestinal bleeding

    • esophagus, stomach, or duodenum

  • lower gastrointestinal bleeding

    • below the ligament of treitz, or bleeding from the jejunum, ileum, colon, or rectum

  • acute blood loss is characterized by

    • hematemesis- the presence of blood in vomit

    • hematochezia- blood from rectum (frank bleeding of the rectum)

    • melena- dark tarry stool

  • occult bleeding- caused by slow chronic blood loss

disorders of motility:

• dysphagia

  • dysphagia is difficulty swallowing

  • types

    • mechanical obstructions

    • functional obstructions

      • caused by a neural or muscular disorder

  • achalasia

    • denervation of smooth muscle in the esophagus and lower esophageal sphincter relaxation

  • manifestation: during eating or drinking may cause mild or severe stabbing pain at the level of obstruction

    

• gastroesophageal reflux disease (gerd)

  • gerd is the reflux of chyme from the stomach to the esophagus

  • if gerd causes inflammation of the esophagus, it is called reflux esophagitis

  • a normal functioning lower esophageal sphincter maintains a zone of high pressure to prevent chyme reflux

  • a zone of low pressure of the lower esophageal sphincter (les) causes gastroesophageal reflux disease

  • inflammatory response to gastroesophageal reflux

  • inflammatory response to gastroesophageal reflux is defined as esophagitis

  • conditions that increase abdominal pressure can contribute to gerd

  • manifestations

    • heartburn, regurgitation of chyme, and upper abdominal pain within 1 hour of eating

• pyloric obstruction

  • pyloric obstruction is the blocking or narrowing of the opening btwn the stomach and the duodenum

  • pyloric obstruction can be acquired or congenital

  • manifestations

    • epigastric pain and fullness, nausea, succession splash (a specific sound heard in physical exam, occurs when theres a lot of fluid or gas trapped in the stomach), vomiting, and with a prolonged obstruction, malnutrition, dehydration, and extreme debilitation

• intestinal obstruction and ileus

  • an intestinal obstruction is any condition that prevents the flow of chyme through the intestinal lumen or failure of normal intestinal motility in the absence of an obstructing lesion

  • an ileus is an obstruction of the intestines

    • intestinal obstruction is a physical blockage often due to adhesions, tumors, or hernias. ileus is a functional issue (impaired intestinal motility, lack of normal muscle movement) w/o a physical obstruction

  • simple obstruction- mechanical blockage of lumen by lesion

  • functional obstruction- failure of mobility

  • small intestinal obstruction

    • caused by adhesions, hernia, and tumors

      • adhesions is the most common type of small intestine obstruction

    • intestinal obstruction at the pylorus or high in the small intestine cause metabolic alkalosis by an excessive loss of hydrogen ions normally absorbed from gastric juice

    • cardinal symptoms of small intestinal obstruction are colicky pain caused by distention followed by vomiting

  • large bowel obstruction

    • caused by colon cancer (90% of the time), mesenteric ischemia, and other inflammatory disease

      

gastritis:

• inflammatory disorder of the gastric mucosa

• it can be

  • acute gastritis- is usually injury of protective mucosal barrier by drugs (ex. aspirin inhibits prostaglandin, which normally stimulate production of mucosa)

    • manifestations: vague abdominal pain, epigastric tenderness and bleeding

  • chronic gastritis- tends to occur in elderly

    • in chronic gastritis inflammatory cytokines such as tumor necrosis alpha (tnf-), interleukins (il-6, il-8, il-10), and leukotrienes are released

    • manifestation: older adults experience hemorrhage or perforation

peptic ulcer disease:

• a peptic ulcer is a break or ulceration in the protective mucosal lining

• a peptic ulcer may occur in esophagus, stomach, or duodenum

• a peptic ulcer can be

  • acute

  • chronic

  • superficial- do not penetrate the muscularis mucosa

    • erosions

  • deep

    • true ulcers

• duodenal ulcers

  • most common of the peptic ulcers

  • developmental factors:

    • helicobacter pylori is the primary cause of duodenal ulcers

      • toxins and enzymes that promote inflammation and ulceration

    • hypersecretion of stomach acid and pepsin

      • can be due to greater than usual number of parietal cells in the gastric mucosa

    • use of nsaids

    • high gastrin levels- gastrin levels remain high longer than normal after eating

    • acid production by cigarette smoking

    • failure of the feedback mechanism occurs, whereas acid in the gastric antrum inhibits gastrin release

  

gastric ulcer:

• gastric ulcers tend to develop in the antral region of the stomach, adjacent to the acid secreting mucosa of the body

• pathophysiology

  • characterized by an increase in concentration of bile salts that damages the mucosal barrier by permitting hydrogen ions to diffuse into the mucosa, where they disrupt permeability and cellular structure

  • gastric secretion tends to be normal or less than normal

malabsorption syndromes:

• maldigestion

  • failure of the chemical processes of digestion

• malabsorption

  • failure of the intestinal mucosa to absorb digested nutrients

• maldigestion and malabsorption frequently occur together

• lactase deficiency

  • inability to break down lactose into monosaccharides and therefore prevent lactose digestion and monosaccharides absorption

  • fermentation of lactose by bacteria causes gas (cramping pain, flatulence, etc.) and osmotic diarrhea

• fat soluble vitamin deficiencies

  • vitamin a

    • night blindness

  • vitamin d

    • decreased calcium absorption, bone pain, osteoporosis, fractures

  • vitamin k

    • prolonged prothrombin time, purpura, and petechiae

  • vitamin e

    • uncertain

ulcerative colitis:

• chronic inflammatory disease that causes ulceration of the colonic mucosa

  • sigmoid colon and rectum

• suggested causes

  • infectious, immunologic (anticolon antibodies), dietary, genetic (supported by family studies and identical twit studies)

• symptoms

  • diarrhea (10-20/day), bloody stools, cramping

• treatment

  • broad spectrum antibiotics and steroids

  • immunosuppressive agents

  • surgery

• an increased colon cancer risk demonstrated

  

appendicitis:

• inflammation of the vermiform appendix

• possible causes

  • obstruction, ischemia, increased intraluminal pressure, infection, ulceration, etc.

• epigastric and rlq pain

  • rebound tenderness

• the most serious complication is peritonitis

obesity:

• obesity is an increase in body fat mass

  • body fat index > 30

• a major cause of morbidity, death, and increased health care costs

• risk factor for many diseases and conditions

• hypothalamus- regulates eating behavior, energy metabolism, and body fat mass

• hormones that control appetite and weight

  • insulin, leptin, peptide yy (decreases appetite by inhibiting nyp/agrp neurons), adiponectin, and resistin

  • ghrelin (stimulate apetide by activating nyp/agrp)

  • agouti-related protein stimulates eating and decrease metaboloism

• leptin resistance- not responding to leptin

anorexia nervosa and bulimia nervosa:

• characterized by abnormal eating behavior, weight regulation, and disturbed attitudes toward body weight, body shape, and size

• anorexia nervosa is characterized by:

  • fear of becoming obese despite weight loss

  • underweight

  • can lead to starvation induced cardiac failure

• bulimia nervosa is characterized by

  • recurrent episodes of binge eating with fears of not being able to stop eating

  • self induced vomiting

liver disorders:

• portal hypertension

  • portal hypertension is abnormally high blood pressure in the portal venous system due to resistance to portal blood flow

  • the most common clinical manifestation of portal hypertension is esophageal bleeding

  • consequences

    • varices

      • lower esophagus, stomach, rectum

    • splenomegaly is an enlargement of the spleen

      • the most common manifestation of splenomegaly is thrombocytopenia

    • ascites- accumulation of fluid in the peritoneal cavity

      • impaired excretion of sodium by the kidneys promotes water retention

      • decreased oncotic pressure and increased hepatic sinusoidal hydrostatic pressure causes movement fluid into the peritoneal cavity

      • decreased blood flew to the kidneys activates aldosterone, which retains sodium

• jaundice (icterus)

  • obstructive jaundice

    • extrahepatic obstruction

    • intrahepatic obstruction

  • hemolytic jaundice

    • prehepatic jaundice

    • excessive hemolysis of red blood cells or absorption of a hematoma

      

viral hepatitis:

• systemic viral disease that primarily affects the liver

• the early (prodromal) clinical manifestations of hepatitis are fatigue, fever, hyperalgia, and vomiting

• types of hepatitis:

  • hepatitis a

    • formally known as infectious hepatitis

  • hepatitis b

    • formally known as serum hepatitis

  • hepatits c, d, e, and g

hepatitis a:

• hepatitis a virus can be found in the feces, bile, and sera of infected individuals

• usually transmitted by the fecal oral route

• risk factors

  • crowded, unsanitary conditions

  • food and water contamination

hepatitis b:

• transmitted through contact with infected blood, body fluids, or contaminated needles

• maternal transmission can occur if the mother is infected during the first trimester

• the hepatitis b vaccine prevents transmission and development of hepatitis b

hepatitis:

• sequence

  • incubation phase- varies (ex. for hep a its 30 days and for hep b its 60-180 days)

  • prodromal (preicteric) phase- when first symptoms appear after exposure

  • icteric phase- begins about 2 weeks after prodromal phase

  • recovery phase

cirrhosis:

• irreversible inflammatory disease that disrupts liver function and even structure

• decreased hepatic function due to nodular and fibrotic tissue synthesis (fibrosis)

• biliary channels become obstructed and cause portal hypertension. due to the hypertension, blood can be shunted away from the liver, and a hypoxic necrosis develops

• alcoholic

  • the oxidation of alcohol damages hepatocytes

  • hepatic fat accumulation is seen in alcoholic cirrhosis

  • pathophysiology

    • alcohol is transformed to acetaldehyde, which promotes liver fibrosis

    • mitochondrial function is impaired, decreasing oxidation of fatty acids

    • acetaldehyde inhibits export of proteins from the liver

disorders of the gallbladder:

• obstruction of inflammation (cholecystitis) is the most common cause of gallbladder problems

• cholelithiasis- gallstone formation

  • types

    • cholesterol (most common) and pigmented (cirrhosis)

  • risks

    • obesity, middle age, female, native american ancestry, and gallbladder, pancreas, or ileal disease

disorders of the pancreas

• pancreatitis

  • inflammation of the pancreas

  • associated with several other clinical disorders

    • caused by an injury or damage to pancreatic cells and ducts, causing a leakage of pancreatic enzymes into the pancreatic tissue

  • these enzymes cause autodigestion of pancreatic tissue and leak into the bloodstream to cause injury to blood vessels and other organs

  • pathophysiology

    • pancreatic acinar cells metabolize ethanol, which generates toxic metabolites

    • injury to the pancreatic acinar cells permit leakage of pancreatic enzymes, which digest pancreatic tissue

    • when gallstones are present, bile flows into the pancreas contributing to attacks

  • manifestations and evaluation

    • epigastric pain radiating to the back

    • fever and leukocytosis

    • hypotension and hypovolemia

      • enzymes increase vascular permeability

    • characterized by an increase in a patients serum amylase level

cancer of the gastrointestinal tract:

• in gi tract cancer mutation of p53 gene occurs

• esophagus

• stomach

• colon and rectum

• liver

• gallbladder

• pancreas

colon cancer:

• manifestation

  • mahogany colored blood mixed with stool

  • pain

  • anemia