ICD-10 Code B96.21 – Shiga toxin-producing Escherichia coli [E. coli] [STEC] O157 as the cause of diseases classified elsewhere (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code B96.21 – Shiga toxin-producing Escherichia coli [E. coli] [STEC] O157 as the cause of diseases classified elsewhere
What it is
This code identifies STEC O157 as the infectious cause of another condition, not the primary diagnosis. Use it when the record names this organism as the source of a disease classified elsewhere.
Clinical signs
Clinical features vary; refer to documentation. STEC O157 is commonly associated with diarrheal illness and may be linked to hemorrhagic colitis or hemolytic uremic syndrome when documented.
When to use this code
Use B96.21 when the provider documents STEC O157 as the cause of a condition coded elsewhere, such as an intestinal infection or a complication. Pair it with the appropriate manifestation or disease code. Do not use it as the only diagnosis unless the chart clearly supports that coding approach.
Do not use for
Do not use this code for unspecified E. coli, non-O157 STEC, or when the organism is not documented. Check documentation if the record only says “E. coli” or lists a different primary diagnosis.
Coding tip
Always code the underlying condition first, then add B96.21 only when STEC O157 is explicitly documented as the cause.