Diagnostic Imaging in Internal Medicine

Diagnostic Imaging in Internal Medicine. 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 Article 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.

Abdominal Radiography

• 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.
• 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
• 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.


Source: Manual of Medicine
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AdMaster said...

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