2024 ICD-10-CM Diagnosis Code J18.9

Pneumonia, unspecified organism

ICD-10-CM Code:
ICD-10 Code for:
Pneumonia, unspecified organism
Is Billable?
Yes - Valid for Submission
Chronic Condition Indicator: [1]
Not chronic
Code Navigator:

Code Classification

  • Diseases of the respiratory system
    • Influenza and pneumonia
      • Pneumonia, unspecified organism

J18.9 is a billable diagnosis code used to specify a medical diagnosis of pneumonia, unspecified organism. The code is valid during the current fiscal year for the submission of HIPAA-covered transactions from October 01, 2023 through September 30, 2024.

Unspecified diagnosis codes like J18.9 are acceptable when clinical information is unknown or not available about a particular condition. Although a more specific code is preferable, unspecified codes should be used when such codes most accurately reflect what is known about a patient's condition. Specific diagnosis codes should not be used if not supported by the patient's medical record.

Approximate Synonyms

The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis code:

  • Acute erosive gastritis
  • Acute gastroenteritis
  • Acute ulcerative gastroenteritis complicating pneumonia
  • Atypical pneumonia
  • Bilateral pneumonia
  • Chronic pneumonia
  • Community acquired pneumonia
  • Disorder of respiratory system co-occurrent with human immunodeficiency virus infection
  • Erosive gastritis
  • Foreign body pneumonia
  • Hemorrhagic pneumonia
  • Hospital acquired pneumonia
  • Infectious disease of lung
  • Infective pneumonia
  • Ornithosis
  • Ornithosis with pneumonia
  • Pleural effusion associated with pulmonary infection
  • Pneumonia
  • Pneumonia with AIDS
  • Pneumonitis
  • Postoperative lower respiratory tract infection
  • Postoperative pneumonia
  • Recurrent pneumonia
  • Respiratory disorder with AIDS
  • Unresolved pneumonia

Clinical Classification

Clinical Information

  • Bronchopneumonia

    inflammation of the lung parenchyma that is associated with bronchitis, usually involving lobular areas from terminal bronchioles to the pulmonary alveoli. the affected areas become filled with exudate that forms consolidated patches.
  • Chlamydial Pneumonia

    pneumonia caused by infections with the genus chlamydia; and chlamydophila, usually with chlamydophila pneumoniae.
  • Cryptogenic Organizing Pneumonia

    an interstitial lung disease of unknown etiology, occurring between 21-80 years of age. it is characterized by a dramatic onset of a "pneumonia-like" illness with cough, fever, malaise, fatigue, and weight loss. pathological features include prominent interstitial inflammation without collagen fibrosis, diffuse fibroblastic foci, and no microscopic honeycomb change. there is excessive proliferation of granulation tissue within small airways and alveolar ducts.
  • Hamman-Rich Syndrome

    acute idiopathic interstitial pneumonitis characterized by diffuse pulmonary alveoli damage with uniform edematous connective tissue proliferation. it is often associated with extensive fibroblastic distortion of the lung parenchyma and leads to adult respiratory distress syndrome in later stages.
  • Healthcare-Associated Pneumonia

    infection of the lung often accompanied by inflammation that is acquired through an interaction within a healthcare institution often through a therapeutic experience (e.g., use of catheters or ventilators).
  • Idiopathic Interstitial Pneumonias

    a group of interstitial lung diseases with no known etiology. there are several entities with varying patterns of inflammation and fibrosis. they are classified by their distinct clinical-radiological-pathological features and prognosis. they include idiopathic pulmonary fibrosis; cryptogenic organizing pneumonia; and others.
  • Lung Diseases, Interstitial

    a diverse group of lung diseases that affect the lung parenchyma. they are characterized by an initial inflammation of pulmonary alveoli that extends to the interstitium and beyond leading to diffuse pulmonary fibrosis. interstitial lung diseases are classified by their etiology (known or unknown causes), and radiological-pathological features.
  • Murine pneumonia virus

    a species of the genus pneumovirus causing pneumonia in mice.
  • Organizing Pneumonia

    any obstructive lung disease characterized by consolidated formation of granulation tissue polyps within alveolar ducts and alveoli. it is classified as either primary (cryptogenic organizing pneumonia) or secondary organizing pneumonia. secondary organizing pneumonia after transplantation is called bronchiolitis obliterans syndrome.
  • Pneumonia

    infection of the lung often accompanied by inflammation.
  • Pneumonia of Calves, Enzootic

    chronic endemic respiratory disease of dairy calves and an important component of bovine respiratory disease complex. it primarily affects calves up to six months of age and the etiology is multifactorial. stress plus a primary viral infection is followed by a secondary bacterial infection. the latter is most commonly associated with pasteurella multocida producing a purulent bronchopneumonia. sometimes present are mannheimia haemolytica; haemophilus somnus and mycoplasma species.
  • Pneumonia of Swine, Mycoplasmal

    a chronic, clinically mild, infectious pneumonia of pigs caused by mycoplasma hyopneumoniae. ninety percent of swine herds worldwide are infected with this economically costly disease that primarily affects animals aged two to six months old. the disease can be associated with porcine respiratory disease complex. pasteurella multocida is often found as a secondary infection.
  • Pneumonia, Aspiration

    a type of lung inflammation resulting from the aspiration of food, liquid, or gastric contents into the upper respiratory tract.
  • Pneumonia, Atypical Interstitial, of Cattle

    a cattle disease of uncertain cause, probably an allergic reaction.
  • Pneumonia, Bacterial

    inflammation of the lung parenchyma that is caused by bacterial infections.
  • Pneumonia, Lipid

    pneumonia due to aspiration or inhalation of various oily or fatty substances or otherwise accumulation of endogenous lipid substances in the pulmonary alveoli.
  • Pneumonia, Mycoplasma

    interstitial pneumonia caused by extensive infection of the lungs (lung) and bronchi, particularly the lower lobes of the lungs, by mycoplasma pneumoniae in humans. in sheep, it is caused by mycoplasma ovipneumoniae. in cattle, it may be caused by mycoplasma dispar.
  • Pneumonia, Necrotizing

    severe complication of pneumonia characterized by liquefaction of lung tissue.
  • Pneumonia, Pneumococcal

    a febrile disease caused by streptococcus pneumoniae.
  • Pneumonia, Pneumocystis

    a pulmonary disease in humans occurring in immunodeficient or malnourished patients or infants, characterized by dyspnea, tachypnea, and hypoxemia. pneumocystis pneumonia is a frequently seen opportunistic infection in aids. it is caused by the fungus pneumocystis jirovecii. the disease is also found in other mammals where it is caused by related species of pneumocystis.
  • Pneumonia, Progressive Interstitial, of Sheep

    chronic respiratory disease caused by the visna-maedi virus. it was formerly believed to be identical with jaagsiekte (pulmonary adenomatosis, ovine) but is now recognized as a separate entity.
  • Pneumonia, Rickettsial

    pneumonia caused by infection with bacteria of the family rickettsiaceae.
  • Pneumonia, Staphylococcal

    pneumonia caused by infections with bacteria of the genus staphylococcus, usually with staphylococcus aureus.
  • Pneumonia, Ventilator-Associated

    serious inflammation of the lung in patients who required the use of pulmonary ventilator. it is usually caused by bacterial cross infection in hospitals.
  • Pneumonia, Viral

    inflammation of the lung parenchyma that is caused by a viral infection.
  • Pulmonary Eosinophilia

    a condition characterized by infiltration of the lung with eosinophils due to inflammation or other disease processes. major eosinophilic lung diseases are the eosinophilic pneumonias caused by infections, allergens, or toxic agents.
  • Radiation Pneumonitis

    inflammation of the lung due to harmful effects of ionizing or non-ionizing radiation.
  • Pneumovirus

    a genus of the family paramyxoviridae (subfamily pneumovirinae) where the human and bovine virions have neither hemagglutinin nor neuraminidase activity. respiratory syncytial virus, human is the type species.
  • Pulmonary Alveoli

    small polyhedral outpouchings along the walls of the alveolar sacs, alveolar ducts and terminal bronchioles through the walls of which gas exchange between alveolar air and pulmonary capillary blood takes place.
  • Streptococcus pneumoniae

    a gram-positive organism found in the upper respiratory tract, inflammatory exudates, and various body fluids of normal and/or diseased humans and, rarely, domestic animals.
  • Rickettsiaceae

    a family of gram-negative bacteria belonging to the order rickettsiales.
  • Eosinophils

    granular leukocytes with a nucleus that usually has two lobes connected by a slender thread of chromatin, and cytoplasm containing coarse, round granules that are uniform in size and stainable by eosin.
  • Erosive Gastritis

    gastritis that is characterized by erosion of the mucosal surface.
  • Acute Interstitial Pneumonia|AIP|Acute Interstitial Pneumonitis

    a rare, rapidly progressing interstitial lung disorder characterized by diffuse and bilateral alveolar damage. patients present with sudden onset of dyspnea and rapid development of respiratory failure. management is supportive and hospitalization and mechanical ventilation are usually required.
  • Aspiration Pneumonitis|Aspiration Pneumonia|Aspiration Pneumonia

    inflammation of the lungs due to the inhalation of solid or liquid material.
  • Bird Fancier's Lung|Avian Hypersensitivity Pneumonitis|Bird fancier's lung|Bird-Breeder's Lung|Pigeon-Breeder's Lung

    hypersensitivity granulomatous pneumonitis caused by the inhalation of avian antigens that are present in the dust of the droppings and feathers of many species of birds. in the acute phase it manifests as fever, chills, dyspnea, cough, and chest tightness. chronic exposure may lead to interstitial lung fibrosis.
  • Chemical Pneumonitis

    inflammation of the lungs caused by the inhalation or aspiration of chemicals.
  • Extrinsic Allergic Alveolitis|Allergic Pneumonitis|Hypersensitivity Pneumonitis

    an inflammatory interstitial lung disease caused by hypersensitivity reaction to inhalation or ingestion of antigens. the antigens are usually related to the patient's occupation. it can present as an acute illness with flu-like symptoms, subacute with repeated episodes of pneumonia, or chronic with dyspnea and productive cough. the majority of patients recover following the cessation of the exposure to the antigen that causes the disease. chronic exposure may eventually progress to interstitial lung fibrosis.
  • Fibrotic Hypersensitivity Pneumonitis|fHP

    interstitial lung fibrosis resulting from chronic hypersensitivity pneumonitis.
  • Grade 1 Pneumonitis, CTCAE|Grade 1 Pneumonitis

    asymptomatic; clinical or diagnostic observations only; intervention not indicated
  • Grade 2 Pneumonitis, CTCAE|Grade 2 Pneumonitis

    symptomatic; medical intervention indicated; limiting instrumental adl
  • Grade 3 Pneumonitis, CTCAE|Grade 3 Pneumonitis

    severe symptoms; limiting self care adl; oxygen indicated
  • Grade 4 Pneumonitis, CTCAE|Grade 4 Pneumonitis

    life-threatening respiratory compromise; urgent intervention indicated (e.g., tracheotomy or intubation)
  • Grade 5 Pneumonitis, CTCAE|Grade 5 Pneumonitis

  • Hypersensitivity Pneumonitis due to Other Organic Dusts|Hypersensitivity pneumonitis due to Other organic dusts

    evidence of hypersensitivity pneumonitis due to other organic dusts.
  • Hypersensitivity Pneumonitis due to Unspecified Organic Dust|Hypersensitivity pneumonitis due to unspecified organic dust

    evidence of hypersensitivity pneumonitis due to unspecified organic dust.
  • Idiopathic Interstitial Pneumonia|IIP|Idiopathic Interstitial Pneumonitis

    non-infectious inflammation of the interstitial lung tissue of unknown etiology. this category includes desquamative interstitial pneumonia, usual interstitial pneumonia, lymphocytic interstitial pneumonia, acute interstitial pneumonia, and nonspecific interstitial pneumonia.
  • Interstitial Pneumonia|Interstitial Pneumonitis

    inflammation of interstitial lung tissue, usually associated with infection.
  • Lymphocytic Interstitial Pneumonia|Diffuse Hyperplasia of Bronchus-Associated Lymphoid Tissue|LIP|Lymphocytic Interstitial Pneumonitis|Lymphocytic interst. pneumonitis|Lymphocytic interstitial pneumonitis

    interstitial pneumonia characterized by the presence of bibasilar pulmonary interstitial infiltrates composed of lymphocytes and plasma cells. it may be associated with autoimmune and lymphoproliferative disorders. signs and symptoms include fever, cough, and dyspnea. symptomatic patients may require immunosuppressive treatment.
  • Pneumonitis

    an inflammatory process affecting the lung parenchyma. it is a milder form of lung inflammation compared to pneumonia.
  • Pneumonitis, CTCAE|Pneumonitis|Pneumonitis

    a disorder characterized by inflammation focally or diffusely affecting the lung parenchyma.
  • Radiation-Induced Pneumonitis

    pneumonitis that is associated with irradiation.
  • Steroid-Refractory Pneumonitis

    pneumonitis that does not respond to corticosteroid therapy.
  • Ornithosis

    disease caused by the chlamydophila psittaci bacteria, usually transmitted from birds to humans.

Index to Diseases and Injuries References

The following annotation back-references for this diagnosis code are found in the injuries and diseases index. The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10-CM code(s).

Convert J18.9 to ICD-9-CM

  • ICD-9-CM Code: 486 - Pneumonia, organism NOS
    Approximate Flag - The approximate mapping means there is not an exact match between the ICD-10 and ICD-9 codes and the mapped code is not a precise representation of the original code.

Patient Education


What is pneumonia?

Pneumonia is an infection in one or both of the lungs. It causes the air sacs of the lungs to fill up with fluid or pus. It can range from mild to severe, depending on the type of germ causing the infection, your age, and your overall health.

What causes pneumonia?

Bacterial, viral, and fungal infections can cause pneumonia.

Bacteria are the most common cause. Bacterial pneumonia can occur on its own. It can also develop after you've had certain viral infections such as a cold or the flu. Several different types of bacteria can cause pneumonia, including:

  • Streptococcus pneumoniae
  • Legionella pneumophila; this pneumonia is often called Legionnaires' disease
  • Mycoplasma pneumoniae
  • Chlamydia pneumoniae
  • Haemophilus influenzae

Viruses that infect the respiratory tract may cause pneumonia. Viral pneumonia is often mild and goes away on its own within a few weeks. But sometimes it is serious enough that you need to get treatment in a hospital. If you have viral pneumonia, you are at risk of also getting bacterial pneumonia. The different viruses that can cause pneumonia include:

  • Respiratory syncytial virus (RSV)
  • Some common cold and flu viruses
  • SARS-CoV-2, the virus that causes COVID-19

Fungal pneumonia is more common in people who have chronic health problems or weakened immune systems. Some of the types include:

  • Pneumocystis pneumonia (PCP)
  • Coccidioidomycosis, which causes valley fever
  • Histoplasmosis
  • Cryptococcus

Who is at risk for pneumonia?

Anyone can get pneumonia, but certain factors can increase your risk:

  • Age; the risk is higher for children who are age 2 and under and adults age 65 and older
  • Exposure to certain chemicals, pollutants, or toxic fumes
  • Lifestyle habits, such as smoking, heavy alcohol use, and malnourishment
  • Being in a hospital, especially if you are in the ICU. Being sedated and/or on a ventilator raises the risk even more.
  • Having a lung disease
  • Having a weakened immune system
  • Have trouble coughing or swallowing, from a stroke or other condition
  • Recently being sick with a cold or the flu

What are the symptoms of pneumonia?

The symptoms of pneumonia can range from mild to severe and include:

  • Fever
  • Chills
  • Cough, usually with phlegm (a slimy substance from deep in your lungs)
  • Shortness of breath
  • Chest pain when you breathe or cough
  • Nausea and/or vomiting
  • Diarrhea

The symptoms can vary for different groups. Newborns and infants may not show any signs of the infection. Others may vomit and have a fever and cough. They might seem sick, with no energy, or be restless.

Older adults and people who have serious illnesses or weak immune systems may have fewer and milder symptoms. They may even have a lower than normal temperature. Older adults who have pneumonia sometimes have sudden changes in mental awareness.

What other problems can pneumonia cause?

Sometimes pneumonia can cause serious complications such as:

  • Bacteremia, which happens when the bacteria move into the bloodstream. It is serious and can lead to septic shock.
  • Lung abscesses, which are collections of pus in cavities of the lungs
  • Pleural disorders, which are conditions that affect the pleura. The pleura is the tissue that covers the outside of the lungs and lines the inside of your chest cavity.
  • Kidney failure
  • Respiratory failure

How is pneumonia diagnosed?

Sometimes pneumonia can be hard to diagnose. This is because it can cause some of the same symptoms as a cold or the flu. It may take time for you to realize that you have a more serious condition.

Your health care provider may use many tools to make a diagnosis:

  • A medical history, which includes asking about your symptoms
  • A physical exam, including listening to your lungs with a stethoscope
  • Various tests, such as
    • A chest x-ray
    • Blood tests such as a complete blood count (CBC) to see if your immune system is actively fighting an infection
    • A Blood culture to find out whether you have a bacterial infection that has spread to your bloodstream

If you are in the hospital, have serious symptoms, are older, or have other health problems, you may also have more tests, such as:

  • Sputum test, which checks for bacteria in a sample of your sputum (spit) or phlegm (slimy substance from deep in your lungs).
  • Chest CT scan to see how much of your lungs is affected. It may also show if you have complications such as lung abscesses or pleural effusions.
  • Pleural fluid culture, which checks for bacteria in a fluid sample that was taken from the pleural space
  • Pulse oximetry or blood oxygen level test, to check how much oxygen is in your blood
  • Bronchoscopy, a procedure used to look inside your lungs' airways

What are the treatments for pneumonia?

Treatment for pneumonia depends on the type of pneumonia, which germ is causing it, and how severe it is:

  • Antibiotics treat bacterial pneumonia and some types of fungal pneumonia. They do not work for viral pneumonia.
  • In some cases, your provider may prescribe antiviral medicines for viral pneumonia
  • Antifungal medicines treat other types of fungal pneumonia

You may need to be treated in a hospital if your symptoms are severe or if you are at risk for complications. While there, you may get additional treatments. For example, if your blood oxygen level is low, you may receive oxygen therapy.

It may take time to recover from pneumonia. Some people feel better within a week. For other people, it can take a month or more.

Can pneumonia be prevented?

Vaccines can help prevent pneumonia caused by pneumococcal bacteria or the flu virus. Having good hygiene, not smoking, and having a healthy lifestyle may also help prevent pneumonia.

NIH: National Heart, Lung, and Blood Institute

[Learn More in MedlinePlus]

Code History

  • FY 2024 - No Change, effective from 10/1/2023 through 9/30/2024
  • FY 2023 - No Change, effective from 10/1/2022 through 9/30/2023
  • FY 2022 - No Change, effective from 10/1/2021 through 9/30/2022
  • FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016. This was the first year ICD-10-CM was implemented into the HIPAA code set.


[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.