ICD code T63.123S – Venomous lizard envenomation from assault, sequela

Key takeaways

T63.123S covers the sequela of a toxic effect of venom of a venomous lizard other than a gila monster, inflicted by assault.

The 7th character S marks a visit for a residual condition, so that condition is coded first and T63.123S follows it.

Gila monster venom uses T63.113S, and rattlesnake venom belongs to a separate family, T63.01-, so species documentation decides the code.

The code already carries the external cause and the assault intent, so no Chapter 20 cause code is needed at a sequela visit.

ICD-10 code T63.123S: quick reference summary

ICD-10 code T63.123S is a billable code for the late effect of a venomous lizard bite inflicted during an assault. The lizard is any venomous species except the gila monster. The code is always sequenced after the residual condition treated at the visit. The table below collects the facts coders check most often.

Breaking down each character of T63.123S

Each character in T63.123S narrows the code a step further. Misreading one of them sends the claim to the wrong animal, intent, or encounter type.

The Alphabetic Index sends “Lizard (bite) (venom)” to T63.12-, while the gila monster has its own entry at T63.11-. In practice, the Mexican beaded lizard (Heloderma horridum) is the species most often coded to T63.12-. When the note says only “lizard bite” and describes no venom effect, query the provider before choosing any T63 code.

The path below shows the three answers in the note that lead to T63.123S, and where each other answer sends the claim.

Where T63.123S sits in the T63.1 hierarchy

Subcategory T63.1 splits into three reptile groups, and each group carries four intents and three encounter types. The sequela codes below show where T63.123S sits among its closest neighbors.

Rattlesnake venom does not belong anywhere in this table. It is coded in T63.01-, so the assault sequela of a rattlesnake bite is T63.013S. ICD-10-CM also has no separate code for diamondback rattlesnakes, so every rattlesnake species shares the T63.01- codes.

What the S sequela character means

The S 7th character applies when the patient is treated for a condition that arose as a direct result of the original toxic effect. ICD-10-CM Official Guidelines Section I.C.19.a describes it with the example of scar formation after a burn.

For T63.123S, the sequela is the residual problem that remains once the acute envenomation has been treated. The table compares the three encounter types for the same assault.

The most common error is using D for a return visit about a residual condition. A patient treated for the bite months ago who now presents with hand stiffness has a sequela encounter. The guidelines also set no time limit on when a sequela code can be used.

Correct coding sequence for sequela encounters

1. Code the residual condition first, such as L90.5 for a scar or M25.641 for stiffness of the right hand.
2. Code T63.123S second to identify the toxic effect that caused it.
3. Add no external cause code for the mechanism or intent, because T63.123S already includes both.
4. Leave out place of occurrence, activity, and status codes, which are reported only at the initial encounter.

Required companion codes when billing T63.123S

T63.123S never works as a standalone code, yet its companion list is short. The residual condition is the only required partner, and a claim scrubber can flag a claim that arrives without one.

Two external cause codes cause most of the confusion. W59.11XS means “Bitten by nonvenomous snake, sequela,” and category W59 excludes contact with venomous reptiles. Y04 describes assault by bodily force, such as a fight or a human bite, so it does not describe a lizard envenomation either.

Clearinghouse front-end edits check code pairs like these before the payer sees them. Adding a W59 code next to T63.123S breaks an Excludes1 note, which those edits can flag.

Excludes notes and what T63.123S does not cover

The Tabular List places no Excludes note on T63.1 or T63.12 themselves. The boundaries come from the T51-T65 block, category T63, and the external cause categories nearby.

• Excludes1 at T51-T65: Contact with and (suspected) exposure to toxic substances (Z77.-). A Z77 code describes exposure without a toxic effect, so it is never coded with T63.123S.
• Excludes2 at T63: Ingestion of toxic animal or plant (T61.-, T62.-). A patient who ate toxic animal matter is coded in those categories, not in T63.
• Includes at T63: The bite or touch of a venomous animal, and being pricked or stuck by a thorn or leaf.
• Intent note at T51-T65: When no intent is documented, code to accidental (T63.121S). Use undetermined (T63.124S) only when the record states that intent cannot be determined.
• Excludes1 at W59: Contact with venomous reptile (T63.0-, T63.1-). A nonvenomous lizard bite goes to W59.01-, with the injury itself coded from the S section.
• Use additional code at T51-T65: Report all associated manifestations of the toxic effect, and Z18.- for any retained foreign body.

Related and easily confused codes

T63.123S sits close to several codes that share part of its wording. This comparison shows what each one means and when it applies instead.

Documentation requirements for sequela encounters

A T63.123S claim holds up only when the note supports every part of the code. The record needs to carry four elements.

1. Explicit causal linkage: The provider states that the current condition is a sequela of the prior envenomation. “Scar of right hand, sequela of beaded lizard envenomation” meets this standard, while “history of lizard bite” does not.
2. Animal identity: The note names a venomous lizard other than a gila monster, or at least a venomous lizard with the species unknown. “Gila monster” points to T63.113S instead.
3. Assault intent: The record states that another person caused the bite. Without that statement, the intent defaults to accidental.
4. The residual condition: The note names the condition treated today, clearly enough to support the code sequenced before T63.123S.

When any element is missing, query the provider before coding rather than inferring it. That habit keeps the claim defensible in an audit.

Common claim denials and how to avoid them

Most T63.123S denials trace back to sequencing, species, or intent. The table lists the common patterns and the fix for each.

CARC 16 (claim lacks information or has submission errors) and CARC 11 (diagnosis inconsistent with the procedure) are the usual signals of a coding problem. The full list of denial reason codes helps you tell a coding denial from a coverage one.

Electronic remittance advice files carry these codes for every claim you submit. Sorting them by code shows a repeating pattern, and a denial management process fixes it at the source instead of one claim at a time.

Coding scenarios: T63.123S in practice

Three scenarios show where T63.123S applies, where a sibling code is correct, and the most common 7th-character error.

Scenario A: hand scar after an assault with a beaded lizard

A patient presents ten months after another person forced a pet Mexican beaded lizard to bite their right hand. The emergency department treated the envenomation at the time. The provider documents: “Scar of right hand, sequela of beaded lizard envenomation during an assault.”

Correct code sequence: L90.5 (scar conditions and fibrosis of skin) first, then T63.123S. The beaded lizard places the case in T63.12-, the assault sets the sixth character to 3, and the residual scar calls for the S character. No external cause, place, or activity code is added.

Scenario B: gila monster bite coded as another lizard

A patient returns eight months after an assault in which the attacker used a gila monster. The note reads: “Chronic right hand pain, late effect of gila monster envenomation (assault).” The billing team selects T63.123S because the chart mentions a lizard.

Correct code sequence: M79.641 (pain in right hand) first, then T63.113S. The gila monster has its own subcategory, T63.11-, so T63.123S is incorrect here. Reserve T63.12- for venomous lizards the note does not identify as a gila monster.

Scenario C: T63.123A used for a residual condition visit

A patient bitten by a beaded lizard during an assault two years ago visits a new practice for stiffness in the right hand. The billing team selects T63.123A because this is the patient’s first visit to that practice.

Why this is wrong: The A character means active treatment of the toxic effect, not a first visit to a new provider. The envenomation resolved long ago, so the correct sequence is M25.641 (stiffness of right hand) first, then T63.123S.

How Pabau keeps T63.123S sequela claims clean

Without a check before submission, a sequencing or species error on T63.123S usually surfaces only when the denial arrives. The claim then needs correcting, resubmitting, and chasing, weeks after the visit.

Practice management software like Pabau keeps insurer details on the patient record and sends US claims to Claim.MD without leaving the system. Your team codes the residual condition and T63.123S against the same record the provider documented.

Pabau’s claims management for billers then tracks each claim’s status in one dashboard. A rejected T63.123S claim shows up quickly, so your team can fix the code order and resubmit from the same screen.

Reduce coding-related denials on sequela claims

Pabau connects the patient record to your claims workflow, so billing teams can check sequencing and the 7th character before claims reach the payer.

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Conclusion

T63.123S is a narrow code, and it holds up when three facts in the note line up. The animal is a venomous lizard other than a gila monster, the bite came from an assault, and today’s condition is a residual effect.

When one of those facts is missing, a provider query costs minutes, while a denial costs a resubmission cycle. Check species, intent and sequence before the claim leaves, and it only has to go out once.

Book a demo to see how Pabau helps your billing team submit and track sequela claims from the patient record.

Continue your research

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