Radiology Coding Alert

he CPT 1999 manual added the new code 78588, which is described as pulmonary perfusion imaging, particulate, with ventilation imaging, aerosol, one or multiple projections. The addition of this new, bundled code to the existing series of nuclear medicine codes for respiratory system or pulmonary studies continues to confuse some coders and raise questions about when to use one or more of the existing codes, or when to use the new, bundled code. Choosing the right code depends on the coders understanding of the following:

the relationship between perfusion and ventilation imaging procedures;

how existing codes were used in the past to describe combinations of perfusion and ventilation lung studies; and

how existing codes are bundled into 78588.

Perfusion and Ventilation in Nuclear Medicine Imaging

Nuclear medicine lung studies by perfusion and ventilation techniques are often used to diagnose pulmonary embolism (ICD-9 415.1 ). Lung studies are also used to evaluate bronchopulmonary sequestration (747.3 or 748.5), and pulmonary trauma (e.g., 861.20, unspecified internal lung injury).

Pulmonary perfusion imaging refers to a procedure that consists of injection of a radioactive particulate to determine lung perfusion or the adequacy of blood flow throughout lung tissue, especially the lung arteries. The patient is injected intravenously with technetium 99-M macroaggregates or particles. This is a radioactive tracer that goes to the lungs and becomes trapped in the small capillary vessels of the lungs. If there is a blood clot in one of the pulmonary arteries, the radioactive particles are blocked from entering this area of lung tissue. On imaging, this pattern shows up as a filling defect on the lung scan. This is useful in detecting pulmonary emboli or clots lodged in the pulmonary arteries.

Pulmonary ventilation imaging involves a procedure whereby the patient inhales a radioactive material in either a gaseous or aerosol (i.e., under-pressure) form. While the perfusion data provide an indication of how well blood is flowing to lung tissue and arteries, ventilation data provide an indication of how well air is flowing through the respiratory system. A balance between rate of ventilation and perfusion of pulmonary capillaries is essential for proper respiratory system function. In other words, perfusion and ventilation are closely related lung studies.

The ventilation data help the radiologist to interpret the perfusion lung scan. Ventilation imaging is generally performed in conjunction with perfusion imaging to enhance the accuracy of the results.

Coding Before the Inception of the New Code

Before 1999, coders reported pulmonary perfusion imaging with CPT Codes 78580 for the lung perfusion study and either 78586 (single projection) or 78587 (multiple projections) for a lung ventilation study depending on the number of projections. (A projection refers to the image of a three-dimensional object on a plane, as in a radiograph.) Thus, describing the more typical clinical procedure often required more than one code to capture both pulmonary perfusion imaging, particulate and pulmonary ventilation imaging, aerosol, multiple projections.

Review of the respiratory system coding series for nuclear medicine reveals a gap. The 1998 CPT manual provided a series of codes to describe ventilation studies performed by one of two methods, either with gaseous radioactive xenon or with inhaled radioactive aerosol. The codes describing ventilation studies with the gaseous method are 78591 (pulmonary ventilation imaging, gaseous, single breath, single projection), 78593 (pulmonary ventilation imaging, gaseous, with rebreathing and washout, with or without single breath, single projection), and 78594 (pulmonary ventilation imaging, gaseous, with rebreathing..., multiple projections). The codes describing perfusion studies with ventilation studies are 78584 (pulmonary perfusion imaging, particulate, with ventilation, single breath) and 78585 (pulmonary perfusion imaging, particulate, with ventilation, rebreathing and washout, with or without single breath). Also, codes describing lung ventilation studies with aerosol are 78586 (pulmonary ventilation imaging, aerosol; single projection) and 78587 (multiple projection). What is missing is a code that describes lung perfusion with aerosol ventilation. Thus, the new, bundled code 78588 was developed to improve the accuracy of coding this situation with a single code.

What about continued use of the codes that existed prior to using 78588? Use the code that most accurately describes the procedure(s) actually performed. If the radiologist per-
formed the bundled procedure described by pulmonary per-
fusion imaging, particulate, with ventilation imaging, aerosol, one or multiple projections, then the new code 78588 describes this exactly and the prior practice of using 78580 with 78587 would be unbundling. If the radiologist performs only a portion of the bundle, the appropriate CPT code should be selected from the respiratory system imaging series 78580-78599 that most accurately describes the procedure performed.

For example, if the procedure is a pulmonary ventilation imaging using aerosol and a single projection, the correct code to report is 78586 (pulmonary ventilation imaging, aerosol; single projection). Since a code is available to accurately describe the procedure, the coder should not report code 78588 with a -52 modifier to indicate reduced services.

The coder should also note that the description for code 78588 states single or multiple projections. Thus, code 78588 should be reported only one time for any number of projections performed.