Study Notes on Assessment of Digestive and Gastrointestinal Function

Assessment of Digestive and Gastrointestinal Function

Organs of the Digestive System

  • Pharynx

  • Parotid gland

  • Oral cavity (mouth)

  • Sublingual gland

  • Submandibular gland

  • Trachea

  • Esophagus

  • Diaphragm

  • Liver

  • Gallbladder

  • Common bile duct

  • Duodenum

  • Pancreatic duct

  • Ascending colon

  • Vermiform appendix

  • Stomach

  • Spleen

  • Pancreas

  • Transverse colon

  • Small intestine

  • Descending colon

  • Sigmoid colon

  • Rectum

  • Anus

Anatomy and Blood Supply of the Large Intestine

  • Aorta

  • Superior mesenteric artery

  • Inferior mesenteric artery

Functions of the Digestive Tract

  • Breakdown of food for digestion

  • Absorption into the bloodstream of small nutrient molecules produced by digestion

  • Elimination of undigested, unabsorbed foodstuffs and other waste products

Terms

  • Digestion: Begins with the act of chewing, in which food is broken down into small particles. These particles can be swallowed and mixed with digestive enzymes.

  • Absorption: The primary function of the small intestine. Vitamins and minerals absorbed are essentially unchanged, starting in the jejunum through mechanisms of active transport and diffusion across the intestinal wall into the bloodstream.

  • Elimination: The phase of the digestive process following digestion and absorption, where waste products are expelled from the body.

Major Enzymes and Secretions

  • Chewing and swallowing: Saliva and salivary amylase are involved in the breakdown of food.

  • Gastric function: Involves hydrochloric acid, pepsin, and intrinsic factor for protein digestion and vitamin B12 absorption.

  • Small intestine: Enzymes such as amylase, lipase, and trypsin are secreted, and bile helps emulsify fats.

  • Processes: Chyme formation, emulsification, and peristalsis are critical components of digestion.

Table 38-1: Major Digestive Enzymes and Secretions

  • Enzymes that Digest Carbohydrates:

    • Ptyalin (salivary amylase)

    • Source: Salivary glands

    • Digestive Action: Converts starch into dextrin, maltose, and glucose.

    • Amylase

    • Source: Pancreas and intestinal mucosa

    • Digestive Action: Further acts on starch.

    • Maltase

    • Source: Intestinal mucosa

    • Digestive Action: Converts maltose to glucose.

    • Sucrase

    • Source: Intestinal mucosa

    • Digestive Action: Converts sucrose to glucose and fructose.

    • Lactase

    • Source: Intestinal mucosa

    • Digestive Action: Converts lactose to glucose and galactose.

  • Enzymes/Secretions that Digest Protein:

    • Pepsin

    • Source: Gastric mucosa

    • Digestive Action: Digests proteins into polypeptides.

    • Trypsin

    • Source: Pancreas

    • Aminopeptidase

    • Source: Intestinal mucosa

    • Dipeptidase

    • Source: Intestinal mucosa

  • Enzymes/Secretions that Digest Fat (Triglyceride):

    • Pharyngeal lipase

    • Source: Pharynx mucosa

    • Steapsin

    • Source: Gastric mucosa

    • Pancreatic lipase

    • Source: Pancreas

    • Bile

    • Source: Liver and gallbladder

Table 38-2: Major Gastrointestinal Regulatory Substances

  • Neuroregulators:

    • Acetylcholine:

    • Stimulus for Production: Stomach distention, vagal and local nerves in the stomach.

    • Target Tissue: Gastric glands, other secretory glands, gastric, and intestinal muscle.

    • Effect on Secretions: Increases gastric acid.

    • Effect on Motility: Generally increased.

    • Norepinephrine:

    • Stimulus for Production: Stress and other stimuli.

    • Effect on Secretions: Generally inhibitory.

    • Effect on Motility: Generally decreased; increased sphincter tone.

  • Hormonal Regulators:

    • Gastrin:

    • Stimulus for Production: Vagal stimulation and calcium-containing foods.

    • Target Tissue: Gastric glands, stomach antrum, duodenum.

    • Effect on Secretions: Increases secretion of gastric acid and pepsinogen.

    • Effect on Motility: Increased.

    • Cholecystokinin:

    • Stimulus for Production: Presence of fatty acids and chyme in duodenum.

    • Target Tissue: Gallbladder and pancreas.

    • Effect on Secretions: Releases bile into duodenum and increases production of enzyme-rich pancreatic secretions.

    • Effect on Motility: Slows gastric emptying.

    • Secretin:

    • Stimulus for Production: pH of chyme in duodenum (pH < 3).

    • Effect on Motility: Decreases gastrointestinal motility.

  • Local Regulator:

    • Histamine:

    • Effect on Secretions: Increases gastric acid production.

Assessment of the GI System

Common Symptoms and Signs

  • Health History: Assess for symptoms such as:

    • Abdominal pain

    • Dyspepsia

    • Gas

    • Nausea and vomiting

    • Diarrhea

    • Constipation

    • Fecal incontinence

    • Jaundice

    • Previous GI disease reports

  • Pain Assessment:

    • Character: Duration, pattern, frequency, location, and distribution of referred abdominal pain can indicate underlying issues.

  • Common Manifestations of GI Disease:

    • Abdominal pain

    • Dyspepsia

    • Gas

    • Nausea and vomiting

    • Changes in bowel habits and stool characteristics

    • Jaundice

    • Ascites

    • Engorged veins

Change in Bowel Habits and Stool Characteristics

  • Indicators of colonic dysfunction or disease.

  • Can manifest as constipation or diarrhea.

Past Health, Family, and Social History

  • Inquire about:

    • Oral care and dental visits

    • Lesions in the mouth

    • Discomfort with certain foods

    • Alcohol and tobacco usage

    • Use of dentures

Physical Assessment of the GI System

  • Oral Cavity Assessment:

    • Lips, gums, tongue.

  • Abdominal Assessment:

    • Four quadrants method:

    • Inspection

    • Auscultation: Normal sounds range from 5-30 per minute, with abnormal findings such as borborygmi (growling sounds).

    • Percussion:

      • Dullness indicates solid structures.

      • Tympany indicates air-filled areas.

    • Palpation:

      • Evaluate for tenderness, pain, rebound tenderness, and edema.

    • Key Signs: Murphy's sign for gallbladder tenderness, McBurney's sign for appendicitis, and Bloomburg's sign for rebound tenderness.

Division of the Abdomen into Quadrants or Regions

  • Helps in localizing abdominal pain and performing assessments.

Diagnostic Tests of the GI System

Types of Tests

  • Serum Laboratory Studies

  • Stool Tests

  • Breath Tests

  • Abdominal Ultrasonography

  • Genetic Testing

  • Imaging Studies: Includes CT, PET, MRI, scintigraphy, and virtual colonoscopy.

  • Upper GI Tract Study

  • Lower GI Tract Study: Barium enema for contrast studies.

GI Motility Studies

  • Involves assessing movement within the GI tract.

Endoscopic Procedures

  1. EGD (Esophagogastroduodenoscopy)

  2. Colonoscopy

  3. Anoscopy, Proctoscopy, and Sigmoidoscopy

  4. Small-bowel Enteroscopy

  5. Endoscopy through an Ostomy

  6. Manometry and Electrophysiologic Studies: Used to evaluate esophagus, stomach, duodenum, rectal pressures.

Nursing Interventions for GI Diagnostic Tests

  • Inform the provider of known medical conditions or abnormal lab values that may impact the procedure.

  • Assess hydration status pre-, during, and post-procedure, ensuring appropriate education on hydration maintenance.

  • Provide health information and procedural education to patients and significant others.

  • Offer post-procedure care instructions and activity restrictions.

  • Alleviate discomfort and anxiety for patients undergoing these tests.

Liver Function Tests

  • Blood Tests: Measure serum enzyme activity, serum concentrations of proteins (albumin, globulins), bilirubin levels, ammonia, clotting factors, and lipids.

  • Liver Biopsy and Paracentesis: Used to assess liver function and disease.

Normal Values for Liver Function Tests

  • Serum Bilirubin (Direct): Range: 0.1 – 0.4 mg/dL, assesses liver's ability to conjugate and excrete bilirubin (abnormal in liver/biliary disease).

  • Total Serum Bilirubin: Range: 0.3 – 1 mg/dL.

  • Urine Bilirubin: <0.25 mg/24h.

  • Total Serum Protein: 7 - 7.5 g/dL.

  • Serum Albumin: 3.5 – 5.2 g/dL.

  • Serum Globulin: 2.3 – 3.5 g/dL.

  • Prothrombin Time/INR:

    • Normal PT: 11 – 13 s

    • Normal INR: <1.1.

  • Alkaline Phosphatase: Adults: 52-142 u/L, measures biliary obstruction in absence of bone disease.

  • Alanine Aminotransferase (ALT): 10-40 U/mL, released from damaged liver cells.

  • Aspartate Aminotransferase (AST): 8-40 U/mL.

  • Gamma-Glutamyl Transferase (GGT): 0-30 U/L, indicative of alcohol abuse or biliary cholestasis.

  • Ammonia (plasma): 15-45 mcg/dL, elevated in liver failure as liver converts ammonia to urea.

Questions and Answers

  • Question #1: Physiological processes NOT performed in the small intestine?

    • Options: A. Fat breakdown B. Carbohydrate breakdown C. Water and electrolyte reabsorption D. Peristalsis

    • Correct Answer: C.

  • Question #2: Is lipase an enzyme that aids in protein digestion?

    • Correct Answer: False.

  • Question #3: What is ingestion?

    • Options:
      A. Occurs when food is taken into the GI tract via the mouth and esophagus
      B. Occurs when enzymes mix with ingested food
      C. Occurs when small molecules pass through the intestinal walls
      D. Occurs after digestion and absorption when waste products eliminated

    • Correct Answer: A.

  • Diagnostic Tests of GI System Summary: Focus on the methods for investigating GI health, from laboratory tests to imaging and endoscopy.

  • Nursing Interventions: Crucial for promoting patient safety and comfort before, during, and after procedures. Hydration and patient education remain priorities.