ICD-10 Code A36.85 – Diphtheritic cystitis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A36.85 – Diphtheritic cystitis
What it is
This code identifies cystitis caused by diphtheria infection. Use it when the bladder inflammation is documented as diphtheritic, not as a routine urinary tract infection.
Clinical signs
Clinical features vary; refer to documentation. You may see bladder inflammation with urinary discomfort, frequency, or hematuria when diphtheritic involvement is confirmed.
When to use this code
Use A36.85 when the clinician documents diphtheritic cystitis or bladder involvement due to diphtheria. Apply it only when the record clearly links the cystitis to diphtheria infection. If the note is nonspecific, check documentation before coding.
Do not use for
Do not use this code for uncomplicated cystitis, bacterial UTI, or urinary symptoms without confirmed diphtheritic cause. Check documentation if the bladder condition is listed only as suspected.
Coding tip
Look for explicit wording tying cystitis to diphtheria before assigning A36.85.