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colon.

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Serotonin (5-hyclroxytryptamine)

Purpose: used to derect carcinoid rumor.

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Reference value, 50-200 ng/ml

Venous blood levels of serotonin 3re measured, as carcinoid

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rumors secrete excess amouncs of serotonin.

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·Text or abbreviations in parentheses signify synonyms to the test names.

Source: Data from LM Malarkey, ME McMorrow. Nurse's Manual of Laboratory Tests and Diagnostic Procedures. Philadelphia: Saunders,

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2000,412-431.

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GASTROINTFSflNAL SYSTEM 511

used to measure functional aspects of secretion, digestion, absorption,

and elimination within the GI tract.' Table 8-6 summarizes diagnostic

procedures used to visualize the GI tract.

Examination of the hepatic (liver), biliary (gallbladder and cystic

ducts), pancreatic, and splenic systems involves numerous laboratory

tests and diagnostic procedures, which are often performed concurrently to fully delineate the etiology of a patient'S clinical presentation. Because of the common location of these organs and shared access to the biliary tree, di ease or dysfunction in one organ can

often extend into the other organs.)

Clinical Tip

Laboratory tests used to examine the liver are frequently

referred to as liver (llllction tests or LFTs.

Hepatocellular injury results in cellular damage in the liver, which

causes increased levels of the following enzymes: aspartate aminotransferase (previously called serum glutamic-oxaloacetic transaminase), alanine aminotransferase (previollsly called serum glutamate pyruvate transamhlose), and lactate dehydrogenase.4

Hepatocellular dysfunction can be identified when bilirubin levels

are elevated or when clotting times are increased (denoted by an

increased prothrombin time). The liver produces clotting facrors and,

therefore, an increased prothrombin time implicates impaired production of coagulation facrors.

Cholestasis is the impairment of bile flow from the liver to the

duodenum and results in elevarions of the following serum enzymes:

alkaline phosphatase, aspartate transaminase (previously known as )'glutamille-oxaloacetic transaminase or y-glutamyl trallspeptidase), and S!-nucleoridase.4

Table 8-7 summarizes the laboratory tests performed ro measure

hepatic, biliary, and pancreatic function, whereas Table 8-8 summarizes the diagnostic procedures performed to visllalize these organs.

Additional diagnostic procedures used ro evaluate the GI system

are laparoscopy, magnetic resonance imaging (MRI), and positron

emission tomography (PET) scans. These methods are described in

the following sections.

Table 8-6. Diagnostic Procedures for the Gastroinrestinal (GI) System"

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N

Test

Description

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Barium enema (BE)

Purpose: To investigate and identify pathologic conditions that change the

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Reference value: No lesions, deficits, or

structure or function of the colon (large bowel).

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abnormalities of the colon are noted.

The colon is emptied of feces, and contrast medium (barium) is instilled rec

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tally. Fluoroscopic and x-ray images are then taken to idemify the presence

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of any structural anomalies.

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Barium swallow (esophagography)

Purpose: To idenrify pathologic conditions that change the structure or

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Reference value: No structural or functional

function of the esophagus.

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abnormalities are visualjzed.

The patient takes repeated swallows of barium liquid while x-ray and

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fluoroscopic images are taken in vertical, semivertical, and horizontal

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positions to examine the passage of contrasr medium during swallowing

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and peristaltic movement of the esophagus.

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Colonoscopy (lower panendoscopy)

Purpose: To perform routine screening of the colon for the presence of polyps

Reference value: No abnormalities of strucor rumors and to investigate the cause of chronic diarrhea or other

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ture or mucosal surface are visualized in

undiagnosed Gl complaints.

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the colon or terminal ileum.

Patients are sedated, and an endoscope is inserted inro the rectum and passed

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through the various parts of the colon. Tissue biopsy may be performed

during this procedure.

Computed romography of the GI rraer (ef

Purpose: Used to detect intra-abdominal abscesses, rumors, infarctions,

scan, computerized axial romography

perforation, obstruction, inflammation, and diverticulitis. Metastases ro

[CATJ)

the abdominal cavity can also be detected. lntravenous or oral contrast

may be used during the procedure.

Esophageal manometry

Purpose: To evaluate esophageal motor disorders that could be causing dysphagia

Reference value: Lower esophageal sphincalong with evaluating postoperative outcomes of esophageal surgery.

ter (LES) pressure: 12-25 mm Hg.

LES pressures are measured with an endoscope that is inserted inro the

esophagus either nasally or orally.

Esophageal acidity test (T ucde test)

Purpose: To document gastroesophageal reflux or evaluate the outcomes of

Reference value: Esophageal pH of 6 or

medical-surgical anrireflux managemenc.

higher.

The pH of the esophagus is measured with an endoscope.

Acid perfusion test (Bernstein test)

Purpose: To determine that heartburn is of esophageal rather than cardiac origin.

Reference value: Negative.

N. hydrochloric acid is instilled into the esophagus through the endoscope.

Complaints of hearrburn with acid instillation confirm the esophageal

origin.

Esophagogastroduodenoscopy (EGD, upper

Purpose: To identify and biopsy tissue abnormality, to determine the location

gastrointestinal endoscopy)

and cause of upper GI bleeding, to evaluare the healing of gastric ulcers, to

Reference value: No abnormal structures or

evaJuate the stomach and duodenum after gastric surgery, and to

functions are observed in the esophagus,

investigate the cause of dysphagia, dyspepsia, gastric ourlet obstruction, or

stomach, or duodenum.

epigastric pain.

An endoscope is passed through the mouth into the esophagus to the

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stomach, pylorus, and upper duodenum. Tissue biopsy can be performed