Clinicians have a wide array of radiologic
modalities at their disposal to aid them in noninvasive diagnosis.Despite the
introduction of highly specialized imaging modalities, radiologic tests such as
chest radiographs and ultrasound continue to serve a vital role in the
diagnostic approach to patient care.At most institutions, computed tomography
(CT) is available on an emergent basis and is invaluable for initial evaluation
of patients with trauma, stroke, suspected CNS hemorrhage, or ischemic
stroke.Magnetic resonance imaging (MRI) and related techniques (MR angiography,
functional MRI, MR spectroscopy) are providing remarkable resolution of many
tissues including the brain, vascular system, joints, and most large organs. This
chapter will review the indications and utility of the most commonly utilized
radiologic studies used by internists.
Chest Radiography
• Can be obtained quickly and should be part of the
standard evaluation for patients with cardiopulmonary complaints.
• Is able to identify life-threatening conditions
such as pneumothorax, intraperitoneal air, pulmonary edema, and aortic
dissection.
• Is most often normal in a patient with an acute
pulmonary embolus. • Should be repeated in 4–6 weeks in a patient with an acute
pneumonic process to document resolution of the radiographic infiltrate.
• Is used in conjunction with the physical exam to
support the diagnosis of congestive heart failure.Radiographic findings
supporting the diagnosis of heart failure include cardiomegaly, cephalization,
Kerley B lines, and pleural effusions.
• Should be obtained daily in intubated patients to
examine endotracheal tube position and the possibility of barotrauma.
• Helps to identify alveolar or airspace disease.Radiographic
features of such diseases include inhomogeneous, patchy opacities and
air-bronchograms.
• Helps to document the free-flowing nature of
pleural effusions.Decubitus views should be obtained to exclude loculated
pleural fluid prior to attempts to extract such fluid.
AbdominalRadiography
• Should be the initial imaging modality in a
patient with suspected bowel obstruction.Signs of small-bowel obstruction on
plain radiographs include multiple air-fluid levels, absence of colonic distention,
and a “stepladder” appearance of small-bowel loops.
• Should not be performed with barium enhancement
when perforated bowel, portal venous gas, or toxic megacolon is suspected.
• Is used to evaluate the size of bowel: 1.Normal
small bowel is _3 cm in diameter. 2.Normal caliber of the cecum is up to 9 cm,
with the rest of the large bowel up to 6 cm in diameter.
Ultrasound
• Is more sensitive and specific than CT scanning
in evaluating for the presence of gallstone disease. Can readily identify the
size of the kidneys in a patient with renal insufficiency and can exclude the
presence of hydronephrosis. • Can expeditiously evaluate for the presence of
peritoneal fluid in a patient with blunt abdominal trauma.
• Is used in conjunction with doppler studies to
evaluate for the presence of arterial atherosclerotic disease.
• Is used to evaluate cardiac valves and wall
motion.
• Should be used to localize loculated pleural and
peritoneal fluid prior to draining such fluid.
• Can determine the size of thyroid nodules and
guide fine-needle aspiration biopsy.
• Is the modality of choice for assessing known or
suspected scrotal pathology.
• Should be the first imaging modality utilized
when evaluating the ovaries.
Computed Tomography
• CT of the brain should be initial radiographic
modality in evaluating a patient with a potential stroke.
• Is highly sensitive for diagnosing an acute
subarachnoid hemorrhage and in the acute setting is more sensitive than MRI.
• CT of the brain is an essential test in
evaluating a patient with mental status changes to exclude entities such as
intracranial bleeding, mass effect, subdural or epidural hematomas, and
hydrocephalus.
• Is better than MRI for evaluating osseous lesions
of the skull and spine.
• CT of the chest should be considered in the
evaluation of a patient with chest pain to rule out entities such as pulmonary
embolus or aortic dissection.
• CT of the chest is essential for evaluating lung
nodules to assess for the presence of thoracic lymphadenopathy.
• CT with high-resolution cuts through the lungs is
the imaging modality of choice for evaluating the lung interstitium in a
patient with interstitial lung disease.
• Can be used to evaluate for presence of pleural
and pericardial fluid and to localize loculated effusions.
• Is an essential test in a patient with
unexplained abdominal pain to evaluate for conditions such as appendicitis,
mesenteric ischemia or infarction, diverticulitis, or pancreatitis.
• CT of the abdomen is also the test of choice for
evaluating for nephrolithiasis in a patient with renal colic.
• Is the test of choice for evaluating for the
presence of an abscess in the chest or abdomen.
• In conjunction with abdominal radiography, CT is
part of the evaluation of a patient with a bowel obstruction and can help
identify the cause of such an obstruction.
• Can identify abdominal conditions such as
intussusception and volvulus in a patient with abdominal pain. • Is the imaging
modality of choice for evaluating the retroperitoneum.
• Should be obtained expeditiously in a patient
with abdominal trauma to evaluate for the presence of intraabdominal hemorrhage
and to assess injury to abdominal organs.
Magnetic Resonance Imaging
• Is more useful than CT in the evaluation of ischemic
infarction, dementia, mass lesions, demyelinating diseases, and most nonosseous
spinal disorders.
• Provides excellent imaging of large joints
including the knee, hip, and shoulder.
• Can be used, often with CT or angiography, to
assess possible dissecting aortic aneurysms and congenital anomalies of the
cardiovascular system. Cardiac MRI is proving useful to evaluate cardiac wall
motion and for assessing cardiac muscle viability in ischemic heart disease.
• Is preferable to CT for evaluating adrenal masses
such as pheochromocytoma and for helping to distinguish benign and malignant
adrenal masses.
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