Toxic effect of harmful algae and algae toxins, undet, sqla

This code signifies the long-term or residual health problems resulting from exposure to harmful algae or their toxins, when the intent (accidental, intentional self-harm, assault) of the exposure is unknown. These sequelae can manifest as chronic neurological issues, persistent gastrointestinal disturbances, or lasting dermatological conditions that developed after the initial toxic event.

Apply this code for patients presenting with chronic health issues directly attributed to a past exposure to harmful algae or their toxins, where the original exposure event's circumstances (e.g., accidental ingestion, environmental contact) were never definitively determined. This is appropriate when the acute phase of the toxic effect has passed, and the patient is now experiencing the lasting consequences.

• Always assign this code as a secondary diagnosis, following the code for the specific sequela (e.g., chronic gastritis, peripheral neuropathy).
• Ensure documentation clearly links the current condition to a past, undetermined toxic algal exposure.
• Do not use this code for acute toxic effects; it is exclusively for residual or late effects.