Understanding Radiology Reports: X-ray and CT

Radiology Reports: The Rorschach Tests of Medicine

Interpretation of radiographic images involves a lot of subjectivity.  You may be familiar with the ink-blot-test where a person is asked to describe what they see in an image, similar to that shown above.  If you are deeply disturbed you may see the devil, if you are happy you may see flowers.  The interpretation is completely subjective, there are no hidden structures to uncover.  Fortunately, reading radiology images is not quite this subjective.  Nevertheless, a lot of subjectivity is involved in creating the interpretation.  

When one looks at a chest x-ray, some structures are well defined, like the heart, ribs, and diaphragms.  Others take a very trained eye to pick out. Like a Rorschach test, they are open to the interpretation of the radiologist.  The arrow points to a faint opacity.  A radiologist might call this pneumonia, atelectasis, “increased lung markings,” or may not think it is significant enough to mention.    

Radiological interpretations are not always absolute. The radiologist’s degree of confidence may be detectable in the descriptions.  

Three factors should be considered when reading a radiology report

1. There is often a degree of subjectivity. 
2. The radiologist probably knows very little about your medical condition. What looks like pneumonia to the radiologist is less likely to be the case in someone who has no symptoms and is having a screening x-ray for a job, for example. 
3. Defensive medicine is real. This is, mostly, a good thing. A radiologist is always biased towards reporting a questionable abnormality. It’s safer for you, and for them, to report the presence of an abnormality they are unsure is really present.  The downside of this is they report a lot of abnormalities that may or may not be of any importance.  Often this results in additional testing. 

These are descriptions of the physical characteristic of x-ray abnormalities.  It tells their appearance. These are not diagnoses or specific structures.

• DENSITY- Often used as a general description of any abnormality which is denser, more solid than, the surrounding tissues. On x-ray, it will appear whiter than the surrounding. It is a very vague term that doesn’t tell much about what they are seeing itself, without providing more description.  For that matter, an infiltrate is a density, as is a nodule, mass, or a coin you swallowed could be called densities.
• OPACITY- This has the same meaning as Density. It comes from the word ‘opaque,’ meaning something you can’t see through completely.  A steamed-up window is more opaque than a clear window.  Of course, in radiology, we are talking about the ability of X-rays, or other forms of ionizing radiation, to pass through a material, not visible light.
• LUCENCY- This is the opposite of opacity/density. An area that allows more x-ray to pass through it than the surrounding tissue. For example an area of bone that has been destroyed by a tumor or infection.
• INFILTRATE-  Think of the lung structure as similar to a kitchen sponge.  Full of small air-filled spaces.  An infiltrate is akin to water saturating part of the sponge, filling some of those spaces with fluid instead of air. This area will appear whiter (more opaque, denser) than the surrounding, air-filled sponge ( or lung). The term may be called “pneumonic infiltrate” if they think it looks like it is from an infection. But any fluid filling the air spaces can cause the same appearance. With pneumonia, the spaces are filled with mucus and products of inflammation from infection.  With congestive heart failure, they are filled with watery fluid. Not all infiltrates are pneumonia. You must consider the whole clinical picture.
• CONSOLIDATION-  This has the same meaning as an infiltrate
• LESION- Any abnormal imaging finding. It does not imply that what is seen is cancer, dangerous or benign. Just that it is not something normally seen.
• INCREASED LUNG MARKINGS- The blackest portions of a chest x-ray appear so because they are mostly air.  If you look closely or magnify the image, you will see a lot of very fine lines running through the space. These are small “lung markings.”  What you are seeing are tiny blood vessels and the lung tissue itself, which divides the lung into small air sacks. When there is inflammation or swelling of these tissues these markings become more visible.  The term “increased lung markings” on your report is not specific for a cause, although the radiologist may suggest a possible cause.

These are names given to patterns of abnormalities that suggest a set of possible diagnoses. They are not disease diagnoses.  To make a diagnosis you also need history, physical examination, and sometimes a biopsy. The x-ray finding must fit the clinical picture.

• ATELECTASIS- This means part of the lung is not fully expanded. Think of the lung structure like a common kitchen sponge, full of little spaces but compressable. If you pushed down on part of the sponge, that small portion compresses, the air is pushed out.  If you took an x-ray of the sponge the compressed portion will appear white, not black like air-filled structures. Atelectasis can occur for various reasons and is a common finding even in healthy lungs. It can occur if you are not taking adequate inspiration, as often occurs after surgery, prolonged bed rest, rib fractures (due to pain). It can occur if fluid is pressing on the lung from outside of the lung, between the lung and chest wall (pleural effusion). It can occur if there is mucus in your smaller airways deep in the lung, blocking airflow to these segments.
• CARDIOMEGALY- This means the heart appears larger than normal.
• MASS- A well-defined density that measures 3 cm or larger in size.
• NODULE- A well-defined density that measures less than 3 cm in size. Of course, cancer is a concern when a nodule is seen.  Many turn out not to be cancer.  The risk that a single or multiple nodules represent cancer is based on its size, the patients’ risks (smoking, age, history of cancer), and on the radiologic qualities of the nodule.  Some nodules require no follow-up and can be ignored. Others require a CT scan (if initially detected on a chest x-ray).  Some require monitoring with periodic CT scan imaging to ensure they are not enlarging.  The Fleischner criteria provide follow-up guidelines.
• GRANULOMA- Small, usually less than 1 cm well-defined density, and usually benign. Often described as calcified. These are areas of local inflammation from a previous infection or inhaled bacteria or fungi (histoplasmosis, blastomycoses, TB) which your body has walled off in a shell of calcium. You may never have been sick with one of these infections, or known you were exposed to it, and still have a granuloma from it. It will not cause a future infection. There are other non-infectious causes of granuloma such as sarcoidosis. Often the cause is unknown.  Granuloma are benign, usually of no significance,  and most of the time do not need any further investigation.
• EDEMA OR PULMONARY EDEMA- This means there appears to be increased water content in the lungs.  Most commonly due to congestive heart failure, it can also be from inflammation of the lung.  First, it may only show as an increase in the size of blood vessels going to the upper lungs (this may be called PULMONARY VASCULAR REDISTRIBUTION or CEPHILIZATION).  As things worsen they may report INCREASED VASCULAR MARKINGS (also termed INTERSTITIAL EDEMA) in certain parts of the lung, indicating the linings between the air sacs are getting swollen. Finally, fluid will fill the air spaces causing the INFILTRATE appearance.  Be aware that interpretations reporting pulmonary edema are not very reliable by chest x-ray.   If the clinical picture does not suggest congestive heart failure, it probably is not cardiac pulmonary edema.
• PNEUMOTHORAX- A “collapsed” lung. This means that air has leaked into the space between the inner chest wall and the lung.  Picture a balloon blown up inside a glass jar, filling the jar completely. If you puncture the balloon with a very tiny needle, air will leak out into the space between the balloon and the glass, the balloon will decompress. But the lung is somewhat elastic, so it doesn’t necessarily completely collapse (decompress). A pneumothorax can occur from trauma, such as a stab wound to the chest. They commonly occur spontaneously, often in young, healthy tall thin males. Some people develop or are born with little “bubbles,”  called blebs, on the outside lining of their lungs. These can pop and cause a pneumothorax. People with COPD are predisposed. A sudden increase in the pressure inside the lung from vomiting, blunt injury to the chest or mechanical or bag ventilation can do this.
• PLEURAL EFFUSION- This is fluid trapped between the outside of the lung and the inside of the chest wall. Imagine our balloon blown up inside the glass jar. If you put some water in the glass jar before you tried to blow up the balloon, you would not be able to fully expand the balloon. This is the same effect a pleural effusion has.