Computed Tomography, Various Sites(Abdomen, Angiography, Biliary Tract and Liver, Brain and Head, Cardiac Scoring, Chest, Colon, Kidneys, Pancreas, Pelvis, Pituitary, Spine, Spleen)
Synonym/Acronym
Computed axial tomography (CAT), computed transaxial tomography (CTT), helical/spiral CT.
Rationale
To visualize and assess internal organs/structures for abnormal or absent anatomical features, abscess, aneurysm, cancer or other masses, infection, or presence of disease. Used as an evaluation tool for surgical, radiation, and medical therapeutic interventions.
Patient Preparation
There are no activity restrictions unless by medical direction. Instruct the patient to fast and restrict fluids, as ordered, for 2 to 4 hr prior to the procedure; CT studies performed without contrast usually do not require the patient to fast before the procedure (e.g., CTA). Fasting may be ordered as a precaution against aspiration related to possible nausea and vomiting. The American Society of Anesthesiologists has fasting guidelines for risk levels according to patient status. More information can be located at www.asahq.org. The Canadian Anesthesiologists’ Society has fasting guidelines for preprocedural fasting. Related information can be located at https:/
Note: Protocols regarding the use of iodinated contrast medium in patients with impaired kidney function and who are receiving metformin or drugs containing metformin for type 2 diabetes may vary by facility; the drug may be discontinued on the day of the test and continue to be withheld for 48 hr after the test. Kidney function should be assessed per facility protocol before use of metformin is resumed (e.g., Cr, eGFR, hydration or clinical assessment).
Regarding the patient’s risk for bleeding, the patient should be instructed to avoid taking natural products and medications with known anticoagulant, antiplatelet, or thrombolytic properties or to reduce dosage, as ordered, prior to the procedure. Number of days to withhold medication is dependent on the type of anticoagulant. Note the last time and dose of medication taken. Protocols may vary among facilities.
Normal Findings
General
Cardiac Scoring
General
Abdomen
Angiography
Brain and Head
Chest
Pelvis
Spine
Spleen
Timely notification to the requesting health-care provider (HCP) of any critical findings and related symptoms is a role expectation of the professional nurse. A listing of these findings varies among facilities.
Study type: X-ray, special/CT with or without contrast.related body system:
Computed tomography (CT) is a noninvasive procedure used to enhance certain anatomic views of an organ with its surrounding structures and vessels. The table is moved in and out of a circular opening in a doughnut-like device called a gantry, which houses the x-ray tube and associated electronics. A beam of x-rays irradiates the patient as the table moves in and out of the scanner in a series of phases. The x-rays penetrate liquids and solids of different densities by varying degrees. Multiple detectors rotate around the patient to collect numeric data associated with the density coefficients assigned to each degree of tissue density. The imaging system’s computer converts the numeric data obtained from the scanner into digital images. Air appears black; bone appears white; and body fluids, fat, and soft tissue structures are represented in various shades between black and white.
Cardiac Scoring CT
Cardiac scoring CT is used to enhance certain anatomic views of the heart for quantifying coronary artery calcium content. Coronary artery disease (CAD) occurs when the arteries that carry blood and oxygen to the heart muscle become clogged or built up with plaque. Plaque buildup slows the flow of blood to the heart muscle, causing ischemia and increasing the risk of heart failure. The cross-sectional views of the arteries demonstrate the location and degree of plaque accumulation (calcium score). The Agatston score is the most frequently used scale to quantitate the amount of calcium in atherosclerotic plaque. The score is graded in levels from 0 to greater than 400, where a score of 0 is associated with a finding of no evidence of CAD, and a score of greater than 400 is associated with a finding of extensive evidence of CAD. Levels of 1 to 10, 11 to 100, and 101 to 400 respectively define minimal, mild, and moderate evidence of CAD. For additional information regarding screening guidelines for atherosclerotic cardiovascular disease (ASCVD) refer to the study titled “Cholesterol, Total and Fractions.”
A CT scan may be repeated after administration of contrast medium given orally, by IV injection, or rectally. CT becomes invasive when contrast medium is used. The cross-sectional views, or slices, of the vascular system that supports major organs (brain, heart, liver and biliary tract, lungs, kidneys and adrenal glands, pancreas, spleen, thyroid gland) and anatomical areas such as the abdomen, chest, head, neck, arms, legs, and spine can be reviewed individually or as a three-dimensional image to allow differentiations of solid, cystic, or vascular obstructions as well as identification of suspected hematomas and aneurysms. Contrast is used to differentiate, enhance, or “light up” areas of interest depending on the type of study to be performed, type of contrast medium to be used, and method of administration. The medium works by creating a contrast between areas of interest based on density; penetration of the x-rays is weaker in areas where the contrast medium is detected by the scanner, showing the blood vessels, organs, and tissue as whitish areas that either outline the area of interest or completely fill it.
Oral ingestion of contrast medium can be used for opacification to distinguish the bowel, adjacent abdominal organs, other types of tissue, and blood vessels as the medium moves through the digestive tract. IV injection of contrast medium is used for evaluation of blood flow through vessels and greater enhancement of tissue density and organ visualization. These images are helpful when blood vessels are heavily calcified, and the images give the most precise information regarding the true extent of stenosis. They can also evaluate intracerebral aneurysms. Small ulcerations and plaque irregularity are readily seen with CTA; the degree of stenosis can be closely estimated with CTA because of the increased number of imaging planes. Multislice or multidetector CT scanners continuously collect images in a helical or spiral fashion instead of a series of individual images, as with standard scanners. Helical CT can collect many images over a short period of time (seconds), is sensitive in identifying small abnormalities, and produces high-quality images. Images can be recorded on photographic or x-ray film or stored in digital format as digitized computer data.
CT Colonography (Virtual Colonoscopy)
The procedure is used primarily to detect polyps, which are growths of tissue in the colon or rectum. Some types of polyps increase the risk of colon cancer, especially if they are large or if a patient has several polyps. Compared to conventional colonoscopy, CT colonography is less effective in detecting polyps smaller than 5 mm, more effective when the polyps are between 5 and 9.9 mm, and most effective when the polyps are 10 mm or larger. This test may be valuable for patients who have diseases rendering them unable to undergo conventional colonoscopy (e.g., bleeding disorders, lung or heart disease) and for patients who are unable to undergo the sedation required for traditional colonoscopy. The procedure is less invasive than conventional colonoscopy, with little risk of complications and no recovery time. CT colonography can be done as an outpatient procedure, and the patient may return to work or usual activities the same day.
CT colonography and conventional colonoscopy require the bowel to be cleansed before the examination. The screening procedure requires no contrast medium injections, but if a suspicious area or abnormality is detected, a repeat series of images may be completed after IV contrast medium is given. These density measurements are sent to a computer that produces a digital analysis of the anatomy, enabling HCP to look at slices or thin sections of certain anatomic views of the colon and vascular system. A drawback of CT colonography is that polyp removal and biopsies of tissue in the colon must be done using conventional colonoscopy. Therefore, if polyps are discovered during CT colonography and biopsy becomes necessary, the patient must undergo bowel preparation a second time.
Brain and Head CT
In some cases, scans may be repeated after multiple types of contrast are administered. For example, xenon-enhanced CT scanning is an imaging method used to assess cerebral blood flow. Xenon-133 is an odorless, colorless radioactive gas that can be either inhaled or injected. The isotope moves rapidly through the blood into the brain. The diffused gas demonstrates how much blood goes to each area of the brain. Sensitivity of stroke detection in the acute phase is increased by using Xenon. Combinations of diagnostic modalities are also becoming more common. Positron emission tomography (PET) and single-photon emission tomography (SPECT) are types of nuclear medicine studies that offer insights into functionality such as movement of blood flow or uptake and distribution of metabolites into tumors.
PET/CT and SPECT/CT are imaging applications that superimpose PET or SPECT and CT findings. The images are collected and produced by a single gantry system. The coregistered or image fusion of PET/CT or SPECT/CT findings can provide a detailed combination of anatomical and functional images. Images can be recorded on photographic or x-ray film or stored in digital format as digitized computer data. The CT scan can be used to guide biopsy needles into areas of suspected tumors to obtain tissue for laboratory analysis and to guide placement of catheters for angioplasty or drainage of cysts or abscesses. Tumor staging and progression, before and after therapy, and effectiveness of medical interventions may be monitored by PET/CT or SPECT/CT scanning. The images can be reevaluated and manipulated for further detailed examination without having to repeat the procedure.
Chest CT
Studies have demonstrated that in high-risk patients, annual screening with low-dose CT scans (LDCT) helps lower the risk of death from lung cancer.
Abdomen
Angiography
Biliary Tract and Liver
Brain and Head
Cardiac Scoring
Chest
Colon
Kidneys
Pancreas
Pelvis
Pituitary
Spine
Spleen
Contraindications
Pregnancy is a general contraindication to procedures involving radiation.
Patients who are claustrophobic.
Patients with conditions associated with adverse reactions to contrast medium (e.g., asthma, food allergies, or allergy to contrast medium). Although patients are asked specifically if they have a known allergy to iodine or shellfish (shellfish contain high levels of iodine), it has been well established that the reaction is not to iodine; an actual iodine allergy would be problematic because iodine is required for the production of thyroid hormones. In the case of shellfish, the reaction is to a muscle protein called tropomyosin; in the case of iodinated contrast medium, the reaction is to the noniodinated part of the contrast molecule. Patients with a known hypersensitivity to the medium may benefit from premedication with corticosteroids and diphenhydramine; the use of nonionic contrast or an alternative noncontrast imaging study, if available, may be considered for patients who have severe asthma or who have experienced moderate to severe reactions to ionic contrast medium.
Patients with moderate to marked renal impairment (glomerular filtration rate less than 30 mL/min/1.73 m2), or with conditions associated with preexisting renal insufficiency (e.g., chronic kidney disease, single kidney transplant, nephrectomy, diabetes, multiple myeloma, treatment with aminoglycosides and NSAIDs), because iodinated contrast is nephrotoxic.
Patients with moderate to marked renal impairment (glomerular filtration rate less than 30 mL/min/1.73 m2) and who are also taking metformin, which may put them at risk for development of drug-induced lactic acidosis, a dangerous and sometimes fatal adverse effect of metformin (related to renal impairment that does not support sufficient excretion of metformin).
Patients who are chronically dehydrated before the test, especially older adults and patients whose health is already compromised, because of their risk of contrast-induced acute kidney injury.
Patients with pheochromocytoma, because iodinated contrast may cause a hypertensive crisis.
Patients with bleeding disorders or receiving anticoagulant therapy, because the puncture site may not stop bleeding.
Factors That May Alter the Results of the Study
Abnormal Findings Related to
Identification of abnormal findings is assisted by comparison of parameters such as size, shape, symmetry, density, and location. For example, areas of altered density in either an expected or unexpected location may indicate enlargement of an organ or the presence of blood or other fluids, tumors, or cysts. Comparison by type of abnormal findings may also assist in evaluating areas of altered density. For example, well-defined round or oval areas, smaller in size and having lower density than a primary tumor, may indicate a cyst; a crescent-shaped area of abnormal density that alters the proximity of the liver to the Glisson capsule may indicate a hematoma; areas of less than normal density may indicate hepatic lesions; and dilation of the associated ducts may indicate an obstruction.
Abdomen
Angiography
Biliary Tract and Liver
Brain and Head
Cardiac Scoring
Calcified plaque in the coronary arteries is similar in composition to bone and if present will appear as areas of whiteness depending on the amount of accumulated calcification.
Chest
Colon
Kidneys
Pancreas
Pelvis
Pituitary
Spine
Spleen
Potential Nursing Problems: Assessment & Nursing Diagnosis
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Before the Study: Planning and Implementation
Teaching the Patient What to Expect
Procedural Information
Potential Nursing Actions
Make sure a written and informed consent has been signed prior to the procedure and before administering any medications.
Safety Considerations
After the Study: Implementation & Evaluation Potential Nursing Actions
Avoiding Complications
Treatment Considerations
General
Pain
CT Abdomen and CT Angiography
Cardiac Output
CT Biliary Tract and Liver
Fluid Volume
CT Brain and Head
Cerebral Tissue Perfusion
Cardiac Scoring and CT Chest
Fluid Volume
CT Colonography
Bowel Elimination
CT Kidneys
Infection
CT Pancreas
Nutrition
CT Pituitary
Infection, risk
CT Spine
Mobility
CT Spleen
Nutritional Considerations
Clinical Judgement
Follow-Up and Desired Outcomes