Nursing Assessment: Gastrointestinal System

Chapter 39


Nursing Assessment


Gastrointestinal System


Paula Cox-North




Learning Outcomes



1. Describe the structures and functions of the organs of the gastrointestinal tract.


2. Describe the structures and functions of the liver, gallbladder, biliary tract, and pancreas.


3. Differentiate the processes of ingestion, digestion, absorption, and elimination.


4. Explain the processes of biliary metabolism, bile production, and bile excretion.


5. Link the age-related changes of the gastrointestinal system to the differences in assessment findings.


6. Select significant subjective and objective assessment data related to the gastrointestinal system that should be obtained from a patient.


7. Identify the appropriate techniques used in the physical assessment of the gastrointestinal system.


8. Differentiate normal from abnormal findings of a physical assessment of the gastrointestinal system.


9. Describe the purpose, significance of results, and nursing responsibilities related to diagnostic studies of the gastrointestinal system.



Key Terms
















Reviewed by Phyllis Christianson, MN, APRN-BC, GNP, Senior Lecturer, University of Washington, School of Nursing, Seattle, Washington; and Marian Sawyier, RN, MSN, Staff Nurse, University of New Mexico Hospital, Albuquerque, New Mexico.


The gastrointestinal (GI) system (also called the digestive system) consists of the GI tract and its associated organs and glands. Included in the GI tract are the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus. The associated organs are the liver, pancreas, and gallbladder (Fig. 39-1).


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FIG. 39-1 A, Location of organs of the gastrointestinal system. B, Parts of the stomach.


Structures and Functions of Gastrointestinal System


The GI tract extends approximately 30 ft (9 m) from the mouth to the anus. It is composed of four common layers. From the inside to the outside, these layers are (1) mucosa, (2) submucosa, (3) muscle, and (4) serosa (see Fig. 39-1). The muscular coat consists of two layers: the circular (inner) layer and the longitudinal (outer) layer.


The GI tract is innervated by the parasympathetic and sympathetic branches of the autonomic nervous system. The parasympathetic (cholinergic) system is mainly excitatory, and the sympathetic (adrenergic) system is mainly inhibitory. For example, peristalsis is increased by parasympathetic stimulation and decreased by sympathetic stimulation. Sensory information is relayed via both sympathetic and parasympathetic afferent fibers.


The GI tract has its own nervous system: the enteric (or intrinsic) nervous system. The enteric nervous system is composed of two nerve layers that lie between the mucosa and the muscle layers. These neurons have receptors for pressure and movement.


The GI tract and accessory organs receive approximately 25% to 30% of the cardiac output at rest and 35% or more after eating. Circulation in the GI system is unique in that venous blood draining the GI tract organs empties into the portal vein, which then perfuses the liver. The vascular supply to the GI tract includes the celiac artery, superior mesenteric artery (SMA), and the inferior mesenteric artery (IMA). The stomach and duodenum receive their blood supply from the celiac axis. The distal small intestine to mid larger intestine receives its blood supply from branches of the hepatic and SMAs. The distal large intestine through the anus receives its blood supply from the IMA. Because such a large percentage of the cardiac output perfuses these organs, the GI tract is a major source from which blood flow can be diverted during exercise, stress, or injury.


The abdominal organs are almost completely covered by the peritoneum. The two layers of the peritoneum are the parietal layer, which lines the abdominal cavity wall, and the visceral layer, which covers the abdominal organs. The peritoneal cavity is the potential space between the parietal and visceral layers. The two folds of the peritoneum are the mesentery and the omentum. The mesentery attaches the small intestine and part of the large intestine to the posterior abdominal wall and contains blood and lymph vessels. The omentum hangs like an apron from the stomach to the intestines and contains fat and lymph nodes (see eFig. 39-1 on the website for this chapter).


The main function of the GI system is to supply nutrients to body cells. This is accomplished through the processes of (1) ingestion (taking in food), (2) digestion (breaking down food), and (3) absorption (transferring food products into circulation). Elimination is the process of excreting the waste products of digestion.



Ingestion


Ingestion is the intake of food. A person’s appetite or desire to ingest food influences how much food is eaten. An appetite center is located in the hypothalamus. It is directly or indirectly stimulated by hypoglycemia, an empty stomach, decrease in body temperature, and input from higher brain centers. The hormone ghrelin released from the stomach mucosa plays a role in appetite stimulation. Another hormone, leptin, is involved in appetite suppression. (Ghrelin and leptin are discussed in Chapter 41.) The sight, smell, and taste of food frequently stimulate appetite. Appetite may be inhibited by stomach distention, illness (especially accompanied by fever), hyperglycemia, nausea and vomiting, and certain drugs (e.g., amphetamines).


Deglutition (swallowing) is the mechanical component of ingestion. The organs involved in the deglutition of food are the mouth, pharynx, and esophagus.





Esophagus.


The esophagus is a hollow, muscular tube that receives food from the pharynx and moves it to the stomach. It is 7 to 10 in (18 to 25 cm) long and 0.8 in (2 cm) in diameter. The esophagus is located in the thoracic cavity. The upper third of the esophagus is composed of striated skeletal muscle, and the distal two thirds are composed of smooth muscle.


With swallowing, the upper esophageal sphincter (cricopharyngeal muscle) relaxes and a peristaltic wave moves the bolus into the esophagus. Between swallows, the esophagus is collapsed. It is structurally composed of four layers: inner mucosa, submucosa, muscularis propria, and outermost adventitia.


The muscular layers contract (peristalsis) and propel the food to the stomach. There are two sphincters: the upper esophageal sphincter (UES) at the proximal end of the esophagus and the lower esophageal sphincter (LES) at the distal end. The LES remains contracted except during swallowing, belching, or vomiting. The LES is an important barrier that normally prevents reflux of acidic gastric contents into the esophagus.



Digestion and Absorption


Stomach.


The stomach’s functions are to store food, mix food with gastric secretions, and empty contents in small boluses into the small intestine. The stomach absorbs only small amounts of water, alcohol, electrolytes, and certain drugs.


The stomach is usually J shaped and lies obliquely in the epigastric, umbilical, and left hypochondriac regions of the abdomen (see Fig. 39-5 later in the chapter). It always contains gastric fluid and mucus. The three main parts of the stomach are the fundus (cardia), body, and antrum (see Fig. 39-1). The pylorus is a small portion of the antrum proximal to the pyloric sphincter. Sphincter muscles (the LES and the pyloric sphincter) guard the entrance to and exit from the stomach.


The serous (outer) layer of the stomach is formed by the peritoneum. The muscular layer consists of the longitudinal (outer) layer, circular (middle) layer, and oblique (inner) layer. The mucosal layer forms folds called rugae that contain many small glands. In the fundus the glands contain chief cells, which secrete pepsinogen, and parietal cells, which secrete hydrochloric (HCl) acid, water, and intrinsic factor. The secretion of HCl acid makes gastric juice acidic. This acidic pH aids in the protection against ingested organisms. Intrinsic factor promotes cobalamin (vitamin B12) absorption in the small intestine.



Small Intestine.


The two primary functions of the small intestine are digestion and absorption (uptake of nutrients from the gut lumen to the bloodstream). The small intestine is a coiled tube approximately 23 ft (7 m) in length and 1 to 1.1 in (2.5 to 2.8 cm) in diameter. It extends from the pylorus to the ileocecal valve. The small intestine is composed of the duodenum, jejunum, and ileum. The ileocecal valve prevents reflux of large intestine contents into the small intestine.


The mucosa of the small intestine is thick, vascular, and glandular. The functional units of the small intestine are villi, minute, fingerlike projections in the mucous membrane. They contain epithelial cells that produce the intestinal digestive enzymes. The epithelial cells on the villi also have microvilli. The circular folds in the mucous and submucous layers, along with the villi and microvilli, increase the surface area for digestion and absorption.


The digestive enzymes on the brush border of the microvilli chemically break down nutrients for absorption. The villi are surrounded by the crypts of Lieberkühn, which contain the multipotent stem cells for the other epithelial cell types. (Stem cells are discussed in Chapter 13.) Brunner’s glands in the submucosa of the duodenum secrete an alkaline fluid containing bicarbonate. Intestinal goblet cells secrete mucus that protects the mucosa.



Physiology of Digestion.


Digestion is the physical and chemical breakdown of food into absorbable substances. Digestion in the GI tract is facilitated by the timely movement of food through the GI tract and the secretion of specific enzymes. These enzymes break down foodstuffs to particles of appropriate size for absorption (Table 39-1).



The process of digestion begins in the mouth, where the food is chewed, mechanically broken down, and mixed with saliva. Approximately 1 L of saliva is produced each day. Saliva facilitates swallowing by lubricating food. Saliva contains amylase (ptyalin), which breaks down starches to maltose. Salivary gland secretion is stimulated by chewing movements and the sight, smell, thought, and taste of food. After swallowing, food is moved through the esophagus to the stomach. No digestion or absorption occurs in the esophagus.


In the stomach the digestion of proteins begins with the release of pepsinogen from chief cells. The stomach’s acidic environment results in the conversion of pepsinogen to its active form, pepsin. Pepsin begins the breakdown of proteins. There is minimal digestion of starches and fats. The food is mixed with gastric secretions, which are under neural and hormonal control (Tables 39-2 and 39-3). The stomach also serves as a reservoir for food, which is slowly released into the small intestine. The length of time that food remains in the stomach depends on the composition of the food, but average meals remain from 3 to 4 hours.




In the small intestine, carbohydrates are broken down to monosaccharides, fats to glycerol and fatty acids, and proteins to amino acids. The physical presence and chemical nature of chyme (food mixed with gastric secretions) stimulate motility and secretion. Secretions involved in digestion include enzymes from the pancreas, bile from the liver (see Table 39-1), and enzymes from the small intestine. Enzymes on the brush border of the microvilli complete the digestion process. These enzymes break down disaccharides to monosaccharides and peptides to amino acids for absorption.


Both secretion and motility are under neural and hormonal control. When food enters the stomach and small intestine, hormones are released into the bloodstream (see Table 39-3). These hormones play important roles in the control of HCl acid secretion, production and release of digestive enzymes, and motility.


Absorption is the transfer of the end products of digestion across the intestinal wall to the circulation. Most absorption occurs in the small intestine. The movement of the villi enables the end products of digestion to come in contact with the absorbing membrane. Monosaccharides (from carbohydrates), fatty acids (from fats), amino acids (from proteins), water, electrolytes, vitamins, and minerals are absorbed.



Elimination


Large Intestine.


The large intestine is a hollow, muscular tube approximately 5 to 6 ft (1.5 to 1.8 m) long and 2 in (5 cm) in diameter. The four parts of the large intestine are shown in Fig. 39-2.


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FIG. 39-2 Anatomic locations of the large intestine.

The most important function of the large intestine is the absorption of water and electrolytes. The large intestine also forms feces and serves as a reservoir for the fecal mass until defecation occurs. Feces are composed of water (75%), bacteria, unabsorbed minerals, undigested foodstuffs, bile pigments, and desquamated (shed) epithelial cells. The large intestine secretes mucus, which acts as a lubricant and protects the mucosa.


Microorganisms in the colon are responsible for the breakdown of proteins not digested or absorbed in the small intestine. These amino acids are deaminated by the bacteria, leaving ammonia, which is carried to the liver and converted to urea, which is excreted by the kidneys. Bacteria in the colon also synthesize vitamin K and some of the B vitamins. Bacteria also play a part in the production of flatus.


The movements of the large intestine are usually slow. However, propulsive (mass movements) peristalsis also occurs. When food enters the stomach and duodenum, gastrocolic and duodenocolic reflexes are initiated, resulting in peristalsis in the colon. These reflexes are more active after the first daily meal and frequently result in bowel evacuation.


Defecation is a reflex action involving voluntary and involuntary control. Feces in the rectum stimulate sensory nerve endings that produce the desire to defecate. The reflex center for defecation is in the sacral portion of the spinal cord (parasympathetic nerve fibers). These fibers produce contraction of the rectum and relaxation of the internal anal sphincter. Defecation is controlled voluntarily by relaxing the external anal sphincter when the desire to defecate is felt. An acceptable environment for defecation is usually necessary, or the urge to defecate will be ignored. If defecation is suppressed over long periods, problems can occur, such as constipation or fecal impaction.


Defecation can be facilitated by the Valsalva maneuver. This maneuver involves contraction of the chest muscles on a closed glottis with simultaneous contraction of the abdominal muscles. These actions result in increased intraabdominal pressure. The Valsalva maneuver may be contraindicated in the patient with a head injury, eye surgery, cardiac problems, hemorrhoids, abdominal surgery, or liver cirrhosis with portal hypertension.



Liver, Biliary Tract, and Pancreas


Liver.


The liver is the largest internal organ in the body, weighing approximately 3 lb (1.36 kg). It lies in the right epigastric region (see Fig. 39-5 later in the chapter). Most of the liver is enclosed in peritoneum. It has a fibrous capsule that divides it into right and left lobes (Fig. 39-3).


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FIG. 39-3 Gross structure of the liver, gallbladder, pancreas, and duct system.

The functional units of the liver are lobules (see eFig. 39-2 on the website for this chapter). The lobule consists of rows of hepatic cells (hepatocytes) arranged around a central vein. The capillaries (sinusoids) are located between the rows of hepatocytes and are lined with Kupffer cells, which carry out phagocytic activity (removal of bacteria and toxins from the blood). Interlobular bile ducts form from bile capillaries (canaliculi). The hepatic cells secrete bile into the canaliculi.


About one fourth of the blood supply comes from the hepatic artery (branch of the celiac artery), and three fourths comes from the portal vein. The portal circulatory system (enterohepatic) brings blood to the liver from the stomach, intestines, spleen, and pancreas. The portal vein carries absorbed products of digestion directly to the liver. In the liver the portal vein branches and comes in contact with each lobule.


The liver is essential for life. It functions in the manufacture, storage, transformation, and excretion of a number of substances involved in metabolism. The liver’s functions are numerous and can be classified into four main areas (Table 39-4).



TABLE 39-4


FUNCTIONS OF THE LIVER









































Function Description
Metabolic Functions
Carbohydrate metabolism Glycogenesis (conversion of glucose to glycogen), glycogenolysis (process of breaking down glycogen to glucose), gluconeogenesis (formation of glucose from amino acids and fatty acids).
Protein metabolism Synthesis of nonessential amino acids, synthesis of plasma proteins (except gamma globulin), synthesis of clotting factors, urea formation from ammonia (NH3) (NH3 formed from deamination of amino acids by action of bacteria in colon).
Fat metabolism Synthesis of lipoproteins, breakdown of triglycerides into fatty acids and glycerol, formation of ketone bodies, synthesis of fatty acids from amino acids and glucose, synthesis and breakdown of cholesterol.
Detoxification Inactivation of drugs and harmful substances and excretion of their breakdown products.
Steroid metabolism Conjugation and excretion of gonadal and adrenal corticosteroid hormones.
Bile Synthesis
Bile production Formation of bile, containing bile salts, bile pigments (mainly bilirubin), and cholesterol.
Bile excretion Bile excretion by liver about 1 L/day.
Storage Glucose in form of glycogen. Vitamins, including fat soluble (A, D, E, K) and water soluble (B1, B2, cobalamin, folic acid). Fatty acids. Minerals (iron, copper). Amino acids in form of albumin and beta-globulins.
Mononuclear Phagocyte System
Kupffer cells Breakdown of old RBCs, WBCs, bacteria, and other particles. Breakdown of hemoglobin from old RBCs to bilirubin and biliverdin.


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Biliary Tract.


The biliary tract consists of the gallbladder and the duct system. The gallbladder is a pear-shaped sac located below the liver. The gallbladder’s function is to concentrate and store bile. It holds approximately 45 mL of bile.


Bile is produced by the hepatic cells and secreted into the biliary canaliculi of the lobules. Bile then drains into the interlobular bile ducts, which unite into the two main left and right hepatic ducts. The hepatic ducts merge with the cystic duct from the gallbladder to form the common bile duct (see Fig. 39-3). Most of the bile is stored and concentrated in the gallbladder. It is then released into the cystic duct and moves down the common bile duct to enter the duodenum at the ampulla of Vater. In the intestines, bilirubin is reduced to stercobilinogen and urobilinogen by bacterial action. Stercobilinogen accounts for the brown color of stool. A small amount of conjugated bilirubin is reabsorbed into the blood. Some urobilinogen is reabsorbed into the blood, returned to the liver through the portal circulation (enterohepatic), and excreted in the bile.



Bilirubin Metabolism.

Bilirubin, a pigment derived from the breakdown of hemoglobin, is constantly produced (Fig. 39-4). Because it is insoluble in water, it is bound to albumin for transport to the liver. This form of bilirubin is referred to as unconjugated. In the liver bilirubin is conjugated with glucuronic acid. Conjugated bilirubin is soluble and is excreted in bile. Bile also consists of water, cholesterol, bile salts, electrolytes, and phospholipids. Bile salts are needed for fat emulsification and digestion.


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FIG. 39-4 Bilirubin metabolism and conjugation.



Gerontologic Considerations


Effects of Aging on Gastrointestinal System


The process of aging changes the functional ability of the GI system (Table 39-5). Diet, alcohol intake, and obesity affect organs of the GI system, making it a challenge to separate the sole effects of aging from lifestyle. Xerostomia (decreased saliva production), or dry mouth, affects many older adults and may be associated with difficulty swallowing (dysphagia).1 Many factors can lead to a decrease in appetite and make eating less pleasurable. These include a decrease in taste buds and salivary gland secretion, diminished sense of smell, and caries and periodontal disease leading to loss of teeth.



TABLE 39-5


GERONTOLOGIC ASSESSMENT DIFFERENCES
Gastrointestinal System





































































Expected Aging Changes Differences in Assessment Findings
Mouth
Gingival retraction Loss of teeth, dental implants, dentures, difficulty chewing
Decreased taste buds, decreased sense of smell Diminished sense of taste (especially salty and sweet)
Decreased volume of saliva Dry oral mucosa
Atrophy of gingival tissue Poor-fitting dentures
Esophagus
Lower esophageal sphincter pressure decreased, motility decreased Epigastric distress, dysphagia, potential for hiatal hernia and aspiration
Abdominal Wall
Thinner and less taut More visible peristalsis, easier palpation of organs
Decreased number and sensitivity of sensory receptors Less sensitivity to surface pain
Stomach
Atrophy of gastric mucosa, decreased blood flow Food intolerances, signs of anemia as result of cobalamin malabsorption, slower gastric emptying
Small Intestines
Slightly decreased motility and secretion of most digestive enzymes Complaints of indigestion, slowed intestinal transit, delayed absorption of fat-soluble vitamins
Liver
Decreased size and lowered position Easier palpation because of lower border extending past costal margin
Decreased protein synthesis, ability to regenerate decreased Decreased drug and hormone metabolism
Large Intestine, Anus, Rectum
Decreased anal sphincter tone and nerve supply to rectal area Fecal incontinence
Decreased muscular tone, decreased motility Flatulence, abdominal distention, relaxed perineal musculature
Increased transit time, decreased sensation to defecation Constipation, fecal impaction
Pancreas
Pancreatic ducts distended, lipase production decreased, pancreatic reserve impaired Impaired fat absorption, decreased glucose tolerance


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Age-related changes in the esophagus include delayed emptying resulting from smooth muscle weakness and an incompetent LES.2 Although motility of the GI system decreases with age, secretion and absorption are affected to a lesser extent. The older patient often has a decrease in HCl acid secretion (hypochlorhydria) and a subsequent reduction in the amount of intrinsic factor secreted.


Although constipation is a common complaint of older adults, age-related changes in colonic secretion or motility have not been consistently shown.3 Factors that may increase the risk for constipation include slower peristalsis, inactivity, decreased dietary fiber, decreased fluid intake, constipating medications, and laxative abuse; neurologic, cognitive, and metabolic disorders may also play a role.4,5 (Constipation is discussed in Chapter 43.)


The liver size decreases after 50 years of age, but results of liver function tests remain within normal ranges. Age-related enzyme changes in the liver decrease the liver’s ability to metabolize drugs and hormones.


The size of the pancreas is unaffected by aging, but it does undergo structural changes such as fibrosis, fatty acid deposits, and atrophy. Both obstructive and nonobstructive gallbladder diseases increase with age.6


Older adults, especially those over 85, are at risk for decreased food intake.7 The economic inability to purchase food supplies affects nutritional intake, especially in the older adult. Economic constraints may also reduce the number of fresh fruits and vegetables consumed and thus the amount of fiber. Immobility limits the ability to obtain and prepare meals. In the United States, approximately one third of people over 60 are obese.7,8 Age-related changes in the GI system and differences in assessment findings are presented in Table 39-5.



Assessment of Gastrointestinal System


Subjective Data



Important Health Information


Past Health History.

Gather information from the patient about the history or existence of the following problems related to GI functioning: abdominal pain, nausea and vomiting, diarrhea, constipation, abdominal distention, jaundice, anemia, heartburn, dyspepsia, changes in appetite, hematemesis, food intolerance or allergies, indigestion, excessive gas, bloating, lactose intolerance, melena, trouble swallowing, hemorrhoids, or rectal bleeding. In addition, ask the patient about a history or existence of diseases such as reflux, gastritis, hepatitis, colitis, gallstones, peptic ulcer, cancer, diverticuli, or hernias.



Case Study


Patient Introduction


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iStockphoto/Thinkstock




Question the patient about weight history. Explore in detail any unexplained or unplanned weight loss or gain within the past 6 to 12 months. Document a history of chronic dieting and repeated weight loss and gain.



Medications.

The health history should include an assessment of the patient’s past and current use of medications. The names of all drugs, their frequency of use, and their duration of use are important. This is a critical aspect of history taking because many medications may not only have an effect on the GI system but also may be affected by abnormalities of the GI system. The medication assessment should include information about over-the-counter (OTC) medications, prescription drugs, herbal products, vitamins, and nutritional supplements (see the Complementary & Alternative Therapies box in Chapter 3 on p. 39). Note the use of prescription or OTC appetite suppressants.


Many chemicals and drugs are potentially hepatotoxic (Table 39-6) and result in significant patient harm unless monitored closely. For example, chronic high doses of acetaminophen and nonsteroidal antiinflammatory drugs (NSAIDs) may be hepatotoxic. NSAIDs (including aspirin) may also predispose a patient to upper GI bleeding, with an increasing risk as the person ages. Other medications such as antibiotics may change the normal bacterial composition in the GI tract, resulting in diarrhea. Antacids and laxatives may affect the absorption of certain medications. Ask the patient if laxatives or antacids are taken, including the kind and frequency.




Surgery or Other Treatments.

Obtain information about hospitalizations for any problems related to the GI system. Also obtain data related to any abdominal or rectal surgery, including the year, reason for surgery, postoperative course, and possible blood transfusions. Terms related to surgery of the GI system are presented in Table 39-7.


Related posts:

  1. Introduction
  2. Nursing Management: Sexually Transmitted Infections
  3. Nursing Management: Integumentary Problems
  4. Fluid, Electrolyte, and Acid-Base Imbalances

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Nov 17, 2016 | Posted by in NURSING | Comments Off on Nursing Assessment: Gastrointestinal System

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