In the United States, pneumonia is the leading cause of death from infectious disease, and the sixth leading cause of death overall. Different causes of pneumonia affect the clinical symptoms that patients have. For example, pneumonia caused by Mycoplasma pneumonia usually results in different symptoms from pneumonia caused by streptococcus pneumonia.
With outpatients, the three leading identifiable causes of pneumonia are Mycoplasma pneumonia, respiratory viruses, and streptococcus pneumonia. With inpatients, the leading identifiable cause of pneumonia is streptococcus pneumonia, followed by respiratory viruses and then Mycoplasma pneumonia. For both inpatients and outpatients, however, pneumonia is attributed to unknown causes 37% and 44% of the time.
Diagnostic imaging is used in different ways in the diagnosis of pneumonia. Though most people first think of chest x-rays as the standard tool for diagnosing pneumonia, computed tomography and ultrasound are also used when pneumonia is a possibility.
Chest Radiography and Diagnosis of Pneumonia
When bacterial pneumonia is suspected, chest x-rays that include lateral views as well as posteroanterior views are the preferred form of diagnostic imaging. Most opaque features on chest radiographs due to pneumonia show up within 12 hours, but disease activity level isn’t necessarily correlated with what lung infiltrates look like on x-rays.
Age and a person’s immune status affect the radiologic features that show up in cases of pneumonia. Typically, radiographs show patches of bronchial wall thickening, nodular opacities, and pleural effusions. X-rays alone aren’t sufficient for definitively diagnosing viral pneumonia, but can be used in combination with clinical findings for accurate diagnosis of viral pneumonia.
Computed Tomography in Pneumonia Diagnosis
Computed tomography, or CT, is being used more in the diagnosis of pneumonia, but it’s not the ideal form of diagnostic imaging except in specific cases. CT is good for evaluating indistinct abnormal opacities that show up on chest x-rays, for evaluating patchy or “ground glass” opacities, for confirming the presence of pleural effusion, and for examining patients who have unusually low neutrophil counts. Still, the overall diagnostic imaging and clinical picture must be considered together.
CT has recently been shown to be valuable in diagnosing Middle East respiratory syndrome (MERS), which is a severe respiratory illness with a high mortality rate. CT scans of people with MERS show bilateral changes to the subpleural and basilar airspaces as well as extensive ground glass opacities. Consolidation, however, is seen less frequently in patients with MERS.
How Ultrasound Can Be Used in Diagnosing Pneumonia
Ultrasound is another diagnostic imaging technique that can be used in the diagnosis of pneumonia. Specifically, it can assist with differentiating between consolidation and effusion in the lungs. Consolidated lung tissue may look hypoechoic on ultrasound images, because texture varies more when there is good aeration, but tissues look more homogeneous where consolidation is present.
Generally, diagnostic imaging with ultrasound in suspected cases of pneumonia is limited to finding and quantifying para-pneumonic effusions. If present, additional diagnostic techniques can be used. Lung ultrasound is particularly useful in diagnosing and following the progress of pneumonia in children. It is considered a complementary tool to chest x-rays because if ultrasound shows anything that needs to be followed up, x-rays can be done, but in some cases x-rays can be avoided, reducing children’s exposure to radiation.
X-rays are not the only diagnostic imaging tools used in suspected cases of pneumonia. Computed tomography can be used when a higher level of detail is required, and ultrasound can be used to determine whether x-rays should be taken with pediatric patients to help limit the amount of ionizing radiation children are exposed to.
Dr. Kenneth P. Morrison – Ultrasound Specialist
Diagnostic imaging plays a critical role in treating pneumonia and other infectious diseases. The owner-operator radiologists of SteleRAD have decades of combined experience in diagnostic imaging, including radiography, ultrasonography, and computed tomography. This experience means that patients are more likely to receive the right type of diagnostic imaging for their situation to maximize effectiveness and safety.
Dr. Kenneth P. Morrison is one of SteleRAD’s subspecialists in Ultrasound and CT. He is a member of the American Institute of Ultrasound in Medicine, and the Society of Radiologists in Ultrasound.
Dr. Fibkins studied computed tomography/ultrasound/magnetic residence in his fellowship training at The University of Pennsylvania. To learn more about Dr. Morrison and SteleRAD’s Ultrasound subspecialists, click here.
SteleRAD provides services to hospitals, imaging centers, and physician groups throughout South Florida. If you would like to learn more about our services, please call 954-358-5250 or contact us online at any time.