ICD code S91.151D – Open bite of right great toe

Key takeaways

S91.151D is a billable 7-character ICD-10-CM code, valid for FY 2026 and FY 2027.

The 7th character D marks a subsequent encounter, when active treatment is done and the patient returns for routine healing care.

The note must state that the nail is intact, because documented nail damage moves the code to S91.251D.

Pabau, our practice management software, pre-fills claims from the patient record and checks required fields before they go to Claim.MD.

What ICD-10 code S91.151D means on a follow-up claim

ICD-10 code S91.151D is the billable code for an open bite of the right great toe without nail damage, at a subsequent encounter. You use it when the patient comes back for routine healing care after the bite has already been treated.

The code sits in Chapter 19 of ICD-10-CM, inside the S91 category for open wounds of the ankle, foot and toes. Here is the full hierarchy at a glance.

Check validity for your date of service in the CDC/NCHS ICD-10-CM web tool. It publishes the official tabular list for each fiscal year update.

What S91.151D covers, and when a sibling code fits better

Inclusions and exclusions are where laterality and nail-status errors get caught, ideally before they turn into denials.

What S91.151D includes

• Wound type: Open bite (an animal or human bite that breaks the skin)
• Laterality: Right side only
• Digit: Great toe (first toe, or hallux) specifically
• Nail status: Without damage to nail (nail plate and bed intact on examination)
• Encounter type: Subsequent (the patient returns for follow-up after active treatment is complete)

What S91.151D excludes

• Nail involvement present: Use S91.251D (open bite of right great toe with damage to nail, subsequent encounter)
• Left great toe: Use S91.152D (no nail damage) or S91.252D (with nail damage)
• Initial (active treatment) encounter: Use S91.151A
• Sequela (late effects): Use S91.151S
• Lesser toes (2nd through 5th): Use S91.154D (right) or S91.155D (left) without nail damage, and S91.254D or S91.255D with nail damage
• Laceration rather than a bite: Use S91.111D (laceration without foreign body, right great toe without nail damage) or the adjacent S91.1- toe laceration codes
• Superficial bite with the skin intact: Excluded from S91.15-, so code from S90.46- or S90.47- instead

The most frequent miscode is picking S91.251D when nail involvement was never confirmed on re-examination. If the chart only says “wound check, healing well,” ask for the nail finding before you assign a code.

The decision path below runs these exclusions in the order a coder meets them in the note.

S91.151A, D or S: The 7th character follows the treatment phase

The 7th character sets the encounter type, and it is a frequent reason wound follow-up claims bounce. ICD-10-CM Official Guidelines Section I.C.19.a tie A to active treatment and D to routine care during healing.

Here is a practical test. If the note describes a wound check, dressing change or suture removal with no new decisions about the wound, D is almost always right. If the wound has reopened, become infected or needs new debridement, go back to A.

Per CMS ICD-10-CM guidance, the encounter character reflects the current phase of treatment. It does not count how many times the patient has been seen.

Neighboring S91 codes that get mixed up with S91.151D

Laterality, nail status and wound type all branch inside the S91 family. This crosswalk maps the codes most often confused with S91.151D.

A bite to the second toe on the same foot belongs to S91.154D instead, because the right lesser toes share one code. For wider browsing, the AAPC ICD-10-CM lookup filters by range and keyword. It is a quick way to confirm laterality and nail-status variants.

Clinical scenarios: When S91.151D holds and when it switches

Two visits for the same bite show how one finding changes the code.

Scenario 1: The bite heals as expected

A patient returns to a primary care office five days after a dog bite to the right hallux. The ED note documented irrigation, tetanus prophylaxis and no nail involvement. Today’s note reads: “Wound healing well, no signs of infection, nail intact, dressing changed.” Active treatment is complete, the nail is confirmed intact, and the visit is routine follow-up. S91.151D is correct.

Scenario 2: Nail damage shows up at re-examination

Same patient, same original injury. This time the provider notes a subungual hematoma and a partial nail bed laceration that weren’t visible at first. The wound now involves the nail, so the code switches to S91.251D. The chart must document the finding explicitly, because a coder can’t infer nail damage from a photograph.

Documentation that supports S91.151D at audit

ICD-10-CM guidelines expect documentation to be as specific as the code. For S91.151D, four elements must appear in the progress note. Good medical billing compliance starts with a note template that prompts for each one.

• Laterality: “Right” must be documented. A great toe with no side codes to S91.153D, and an unspecified toe codes to S91.159D.
• Wound type: The note must name an “open bite” or “bite wound.” A note that says only “open wound” doesn’t support a bite code.
• Nail status: The note states that the nail plate is intact and the nail bed undamaged. Without it, a coder can’t rule out S91.251D.
• Encounter type: The note shows healing or monitoring care, not new active treatment. It should say that initial wound management is complete.

Medicare Administrative Contractors (MACs) may also ask for wound assessment findings to support medical necessity. That means wound size, depth, drainage and the condition of the surrounding tissue. Recording them at every visit also covers most commercial payer audits without separate addenda.

The ICD List reference shows the official code notes, including Excludes1 entries that affect paired diagnoses.

What payers expect on S91.151D follow-up claims

Medicare, Medicaid and commercial plans generally cover S91.151D follow-up visits. The claim needs a fitting E/M or wound care CPT code and documented medical necessity.

Prior authorization isn’t usually required for routine wound follow-up. Still, a MAC’s Local Coverage Determinations (LCDs) for debridement, especially 97597 and 97598, may set documentation thresholds.

How the claim moves from note to payment

Like any medical billing cycle, an S91.151D claim follows a fixed path. Each hand-off is a point where it can stall.

1. The provider signs a progress note covering laterality, wound type, nail status and treatment phase.
2. The coder assigns S91.151D plus the CPT code for the work done at the visit.
3. The diagnosis goes into box 21 of the CMS-1500, and a pointer links it to each service line.
4. A clearinghouse checks the format and payer edits, then routes the claim to the payer.
5. The payer adjudicates it, and the remittance shows whether each line paid, denied or adjusted.

Why S91.151D claims get denied, and how to fix them

Most S91.151D denials fall into four groups. Each traces back to the note or the code pairing, so the fix is usually quick. Strong denial management workflows catch these patterns early.

Before you submit: A five-point check

A clean claim on the first attempt starts with a short review before it leaves the practice. Run these five checks on every S91.151D claim.

• Side and digit: The note says right great toe, in those words.
• Nail finding: The plate and bed are documented as intact.
• Phase: The note shows healing-phase care with no new active treatment.
• CPT fit: The service suits a follow-up visit, and any debridement carries wound size.
• Pointer: S91.151D is linked to every service line it supports.

CPT codes that pair with ICD-10 code S91.151D

The CPT code depends on what the provider does at the follow-up, not simply that the patient attended. The ICD-10 code explains why the visit happened. The CPT code describes the service.

Debridement policies vary by payer, so check coverage criteria in CMS ICD-10 coding guidance and your MAC’s LCDs first. Our CPT code library has billing guides for several of these codes, including 97597 for selective debridement.

How Pabau keeps S91.151D follow-up claims moving

Many practices code a wound follow-up from the note, then retype the codes into a separate billing tool. Each rekeyed field is another chance to lose the D or the right side.

Pabau removes that retyping. Its claims software for practices pre-fills the claim from the patient record, with ICD-10 and CPT lookup libraries a search away. Required-field checks run before the claim can be sent, so a missing membership number or authorization code is caught in-house.

US claims go out through Claim.MD, with eligibility checks up front and remittance tracking afterward. Treatment notes and forms stay on the same patient record as the claim. When a payer asks, the documentation behind S91.151D is easy to find.

Send wound follow-up claims without retyping codes

Pabau pre-fills claims from the patient record, checks required fields, and submits US claims through Claim.MD. Your team stops rekeying codes for every wound follow-up.

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Conclusion

S91.151D rewards the coder who reads the note before the code book. When the side, the nail and the phase are all written down, the claim stands. When one is missing, query the provider before you bill, because a corrected claim costs more than a short delay.

The trade-off is a few extra words in every wound note. That habit is cheaper than an appeal, and it keeps the code from drifting to a less specific sibling.

Want claims that pre-fill from the record and check required fields first? Book a demo to see Pabau’s claims workflow for wound follow-ups.

Continue your research

Need to reduce claim denials across your billing workflow? Denial management in healthcare covers the most common denial patterns and how to build a prevention-first billing process.

Submitting claims electronically for the first time? How a medical claims clearinghouse works explains the role of clearinghouses like Claim.MD in validating and routing claims to payers.

Want a cleaner first-pass claim? What is a clean claim explains what a claim needs to pass payer edits on the first submission.

Billing debridement at a wound follow-up? CPT code 97597 explains how selective debridement is billed and documented.

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