ICD code S80.851A – Superficial foreign body, right lower leg

Key takeaways

S80.851A is a valid, billable ICD-10-CM code for the right lower leg only. The left leg takes S80.852A, and an unspecified side takes S80.859A.

The 7th character A applies to every visit during active treatment, including follow-ups with a new provider, not just the first appointment.

Pair it with an external cause code such as W45.8XXA, and confirm right or left from the clinical note before submitting. Unspecified laterality is a known denial trigger.

Claims software such as Pabau runs claim validation that scrubs every claim for missing or invalid details before submission.

ICD-10 Code S80.851A: Definition and billable status

ICD-10 Code S80.851A is an official ICD-10-CM diagnosis code with the full descriptor Superficial foreign body, right lower leg, initial encounter. It is valid and billable for FY2027, which began on October 1, 2026. The code covers foreign material embedded in the superficial tissue of the right leg between the knee and ankle, with no open wound.

The CDC/NCHS ICD-10-CM web tool is the authoritative source for verifying current billable status and code descriptors each fiscal year.

Code breakdown: What each character means

Every character in S80.851A carries a specific meaning. Understanding the structure lets coders navigate the entire S80.85x family without memorizing every code.

Clinical scope: What S80.851A covers and what it does not

This code applies when a foreign body sits in the superficial tissue of the right lower leg. It has not reached deeper structures, and the skin surface is not broken into an open wound.

Included scenarios:

• Splinter of wood, glass, or plastic in the skin
• Gravel or dirt embedded after a fall
• Metal shard or thorn in the dermis
• Foreign body removed in the office without incision (simple extraction)

Excluded (use a different code):

• Open wound with foreign body: use S81.821A (laceration with foreign body, right lower leg, initial encounter)
• Foreign body needing deep surgical dissection: pair CPT 10121 with S81.841A (puncture wound with foreign body), or S81.821A if there is a laceration
• Superficial injury of the knee (not lower leg): use S80.25xA series
• Superficial injury of the ankle or foot: use S90.x series

The line between “superficial” and “open wound” decides the code. If the note documents a laceration, puncture, or other break in the skin caused by the injury, S80.851A is incorrect. Use the matching S81.8- open-wound code instead, and work through the three questions below in order.

7th character selection: A, D, or S

The 7th character is the single most misapplied element of this code family. The ICD-10-CM Official Guidelines for Coding and Reporting (Section I.C.19.a) define each value precisely.

The most common coder error is switching to D at the second or third visit. That happens even while foreign body removal and wound care are still ongoing. If the treating provider is still actively managing the injury, A is correct, regardless of how many visits have occurred. The switch to D happens when care transitions to routine healing checks, not when the patient returns for the second time.

Laterality: S80.851A vs S80.852A vs S80.859A

ICD-10-CM requires laterality documentation for lower leg injury codes. Submitting an unspecified laterality code when the clinical note documents “right” is a common denial trigger that payers flag during automated edits.

The same laterality pattern applies to the D and S encounter variants. If the note says “right leg” and the claim shows S80.859A, expect a payer query or denial. Verify laterality before coding, not after submission.

Companion codes for external cause, activity, and place

S80.851A goes first on the claim as the injury diagnosis. Most payers, and the CMS ICD-10-CM coding guidelines, expect secondary codes that explain how, where, and during what activity the injury occurred. Solid medical billing compliance includes these companion codes on every injury claim.

The ICD-10-CM guidelines treat external cause codes as recommended, not mandatory. Many commercial payers and workers’ compensation carriers still treat them as required for injury claims. Missing them is a common soft-denial trigger. Always check the payer’s local coverage policy before assuming they are optional.

CPT code pairings for foreign body removal

Choosing the right CPT code alongside S80.851A depends on the removal technique documented in the clinical note. A simple incision and removal fits CPT 10120, while CPT 10121 covers complicated removals. A mismatch between the ICD-10 and CPT complexity levels is a known audit risk flagged by payers and the AAPC CPT-to-ICD-10 crosswalk guidance.

Some payers require an RT modifier (right side) on procedure codes to confirm laterality matches the ICD-10 diagnosis. Check the payer’s modifier policy before submission. Pairing S80.851A with CPT 10121 without documentation of deep tissue dissection is one of the most common audit triggers for this code family.

Documentation requirements for S80.851A

The clinical note must support every element of the code before submission. Vague notes like “leg wound” or “possible foreign body” do not meet the specificity threshold required by payers. Fixing a thin note before billing, instead of after a denial, is where clean claim submission pays off most.

The minimum documentation checklist:

1. Foreign body explicitly named: the note must state the specific type (e.g. “wood splinter,” “glass fragment”) not just “wound” or “injury.”
2. Anatomical site confirmed as right lower leg: “right leg below the knee” is sufficient; “leg” alone is not.
3. No open wound present: if the skin is broken, an S81.8- open-wound code applies instead of S80.851A (e.g. S81.821A or S81.841A for a foreign body).
4. Encounter type documented: active treatment (initial) vs. follow-up healing (subsequent) affects the 7th character.
5. External cause documented: how the injury occurred (activity, location, mechanism) supports the external cause codes payers expect.

Common claim denial reasons and how to fix them

S80.851A claims are denied for predictable, preventable reasons, and each one traces back to a documentation or coding error. Strong denial management workflows address these before submission. When a rejection does arrive, the denial codes on the remittance point you to the matching row below.

ICD-10-CM vs ICD-9-CM: Historical crosswalk

ICD-10-CM became mandatory for all HIPAA-covered entities on October 1, 2015. Pre-2015 claims used ICD-9-CM, which lacked the anatomical specificity of modern codes. The General Equivalence Mappings (GEMs) published by CMS provide approximate crosswalks, but they are not exact equivalents.

ICD-9’s superficial injury codes (910–919) did not capture laterality. The GEMs crosswalk helps with historical record review. Never use an ICD-9 code for a service dated on or after October 1, 2015, as CMS and commercial payers reject them.

How Pabau keeps S80.851A claims clean before submission

Getting S80.851A right still starts with a coder reading the note. Laterality, the 7th character, and the CPT pairing all come from what the provider documented, so that judgment stays with your team.

Pabau, the practice management platform we build, takes over once the claim is coded. Its claims management software runs claim validation that scrubs every claim for missing or invalid details before submission. Through its Claim.MD integration, your front desk can also check a patient’s eligibility before the visit.

When the payer responds, ERA settlement posts the remittance back against the claim. Your team reconciles payments and spots denials without keying each remittance in by hand.

Reduce S80.851A denials before they happen

Pabau’s claim validation scrubs every claim for missing or invalid details before submission, so fewer S80.851A claims come back from the payer.

Book a demo

Conclusion

S80.851A holds up on review only when the note supports every character. Name the foreign body, confirm the right lower leg, and keep the A for as long as active treatment continues.

The trade-off worth remembering sits on the procedure side. Bill CPT 10121 against a superficial code only when the note describes deep dissection. Once the skin is broken, move to an S81.8- open-wound code.

Claim validation catches missing or invalid details before a claim leaves the practice, but the coding call stays with your coders. Book a demo to see how Pabau’s claim validation and Claim.MD eligibility checks fit your injury-coding workflow.

Continue your research

Need to understand denial codes after a rejection? Denial codes in medical billing explains the most common CARC and RARC codes that appear when S80.851A claims are rejected.

Billing a complicated removal? CPT code 10121 covers the complicated foreign body removal code and what the note must show to support it.

Want to reduce claim rejections across the practice? Revenue cycle management covers the end-to-end workflow from coding through payment posting that keeps denial rates low.

Looking for clearinghouse options for US claims? Medical claims clearinghouse guide explains how clearinghouses work and how electronic 837P submissions reach payers.

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