ICD-10 Code J18.1 – Lobar pneumonia, unspecified organism (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code J18.1 – Lobar pneumonia, unspecified organism
What it is
J18.1 identifies lobar pneumonia when the infecting organism is not specified in the record. It refers to pneumonia affecting a lobe of the lung, with the cause left undocumented or unknown.
Clinical signs
Common findings include cough, fever, chest pain, shortness of breath, and focal lung consolidation on exam or imaging. Clinical features vary; refer to documentation.
When to use this code
Use J18.1 when the provider documents lobar pneumonia but does not name the organism. It also fits cases where imaging or assessment supports lobar pneumonia, yet the pathogen is not identified in the chart.
Do not assume a specific infectious agent without documentation. If the record later identifies the organism, code the more specific diagnosis instead.
Do not use for
Do not use this code when the organism is known, such as bacterial, viral, or fungal pneumonia with a documented cause. Do not use it for pneumonia described only by location if lobar involvement is not clearly stated.
Coding tip
Check the final provider diagnosis and discharge summary for organism details before assigning J18.1.