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CCS Prep

Interstitial Lung Diseases: Definitions Required for New Codes

One of the most challenging and rewarding things about coding is that the classification systems are always changing. New coders must remember that each of the coding systems is updated at least once a year. In some cases, the revisions may be made quarterly. Besides getting the new codes themselves, coders must understand the clinical meaning of the new codes and be able to differentiate them from other similar existing codes. For the Oct. 1, 2011, update of the ICD-9-CM diagnosis codes, there were seven new codes related to interstitial lung diseases included in the Federal Register proposed rule. Here is a sampling of the conditions and their proposed new codes:

Idiopathic Pulmonary Fibrosis (IPF): The condition involves a distinct type of chronic fibrosing interstitial pneumonia of unknown cause. It's diagnosed via a number of findings, such as a surgical biopsy showing a "usual interstitial pneumonia" pattern, pulmonary function studies generally show restriction, with reduced total lung capacity or reduced vital capacity. Other known causes of interstitial lung disease must be ruled out, including drug toxicities, environmental exposures, and collagen vascular diseases. New codes include:

516.30 Idiopathic interstitial pneumonia, not otherwise specified

516.31 Idiopathic pulmonary fibrosis

Nonspecific Interstitial Pneumonitis (NSIP): This condition affects younger patients than those with IPF and may involve children. There is a more favorable prognosis, but lung function tests typically show similar but milder physiological abnormalities than those found in IPF. Most patients develop hypoxemia during exercise, along with a restrictive ventilatory defect in the majority of patients. NSIP is also called nonspecific interstitial pneumonia, which is currently indexed to code 516.8, Other specified alveolar and parietoalveolar pneumonopathies. This code should continue to be assigned if the NSIP is due to some other underlying cause, such as collagen vascular disease, hypersensitivity pneumonitis, infection, or drug-induced pneumonitis. The new code for this condition is:

516.32 Idiopathic non-specific interstitial pneumonitis

Respiratory Bronchiolitis-associated Lung Disease (RB-ILD): This condition is a combination of interstitial lung disease associated with the pathologic lesion of respiratory bronchiolitis (inflammation of the bronchioles, the smallest air passages of
the lungs). This is typically found in cigarette smokers and is characterized by the presence of pigmented intraluminal macrophages. A certain number of these macrophages are always in the lungs and keep the surface as sterile as possible by devouring bacteria and other small pieces of debris. In this condition however, the number of macrophage clusters skyrockets and fills the respiratory bronchioles, alveolar ducts, and peribronchiolar alveolar spaces. It usually affects smokers in their 40s or 50s with a history of heavy smoking and men are more often affected than women. The new code for the condition is:

516.34 Respiratory bronchiolitis interstitial lung disease

Lymphocytic Interstitial Pneumonia (LIP): LIP may also be known as lymphoid interstitial pneumonia and is characterized by the infiltration of the pulmonary interstitium (the tissue and space around the air sacs of the lungs) with lymphocytes and plasma cells. It was previously thought that this disease process would progress to lymphoma, but with advances in diagnostic techniques, only a small number of cases of LIP have been found to undergo malignant transformation. The condition is most typically diagnosed in women, the onset of which occurs with gradually increasing cough and breathlessness over 3 or more years. Lung nodules and widespread consolidation may occur. The new code for the condition is:

516.35 Idiopathic lymphoid interstitial pneumonia

Cryptogenic Organizing Pneumonia (COP): In COP, the organizing pneumonia pattern is a patchy process characterized primarily by organizing pneumonia involving the alveolar ducts and alveoli with or without bronchiolar intraluminal polyps. Patients typically present with symptoms of a relatively short duration, usually less than 3 months. There is a marked disturbance of gas exchange and hypoxemia may be present. Either sex may be affected and the mean age at onset is 55 years. The new code for the condition is:

516.36 Cryptogenic organizing pneumonia

Desquamative Interstitial Pneumonia (DIP): DIP is another disease process that involves an accumulation of macrophages, in this case in the alveoli. It is differentiated from Respiratory Bronchiolitis-associated Lung Disease (RB-ILD) by the fact that DIP affects the lung in a uniform diffuse pattern and is not focused in the bronchioles. However, the intraluminal macrophages in DIP frequently contain dusty brown pigmentation that is identical to that seen in RB, and both conditions are typically found in cigarette smokers. The new code for the condition is:

516.37 Desquamative interstitial pneumonia

Coders should be aware that the term "interstitial pneumonia" is used for certain forms of interstitial lung disease. Technically, however, the term "pneumonia" refers to inflammation of the lung tissue that is usually associated with infection. But because interstitial lung disease typically has a number of causes (most of which are not related to infection), the term "interstitial pneumonitis" is sometimes documented to refer to the inflammation that occurs in the absence of true infection. If there is a question concerning whether any documentation involving "pneumonia" is related to an infection, the physician should be queried.

Test your knowledge with the following quiz (assume new codes are valid):


1. If a condition is documented as "chronic fibrosing interstitial pneumonia of unknown cause" it should be coded as:

a. 516.36

b. 516.30

c. 516.8

d. 516.39

2. Respiratory bronchiolitis-associated lung disease (RB-ILD) is most like what other interstitial lung disease discussed?

a. Cryptogenic Organizing Pneumonia (COP)

b. Lymphocytic Interstitial Pneumonia (LIP)

c. Desquamative Interstitial Pneumonia (DIP)

d. Nonspecific Interstitial Pneumonitis (NSIP)

3. The disease process of interstitial pneumonia is identical to that found in infectious pneumonia.

a. True

b. False

This month's column has been prepared by Cheryl D'Amato, RHIT, CCS, director of HIM, hospital solutions, and Melinda Stegman, MBA, CCS, clinical technical editor, Ingenix.

Coding Clinic is published quarterly by the American Hospital Association.
CPT is a registered trademark of the American Medical Association.


1. b. Code 516.30 should be assigned when the condition involves a fibrosing interstitial pneumonia process but the cause is unknown.

2. c. Desquamative Interstitial Pneumonia (DIP) involves a similar process with accumulation of macrophages but the two conditions involve different areas of the lung.

3. b. False. The "pneumonia" that may be documented with interstitial lung diseases may refer to the inflammation that occurs in the absence of an infection.

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