Laterality: Right, Left, Bilateral, or Unspecified — and What Happens Across Two Encounters

Official source

“Some ICD-10-CM codes indicate laterality, specifying whether the condition occurs on the left, right or is bilateral. If no bilateral code is provided and the condition is bilateral, assign separate codes for both the left and right side. If the side is not identified in the medical record, assign the code for the unspecified side.”

Age-related nuclear cataract is the plain case: H25.11 right eye, H25.12 left eye, H25.13 bilateral, H25.10 unspecified eye. Both eyes affected is one code, H25.13 — not H25.11 plus H25.12. The two-unilateral pattern is only for categories with no bilateral option.

Official source

“When a patient has a bilateral condition and each side is treated during separate encounters, assign the ‘bilateral’ code (as the condition still exists on both sides), including for the encounter to treat the first side. For the second encounter for treatment after one side has previously been treated and the condition no longer exists on that side, assign the appropriate unilateral code for the side where the condition still exists (e.g., cataract surgery performed on each eye in separate encounters). The bilateral code would not be assigned for the subsequent encounter, as the patient no longer has the condition in the previously-treated site. If the treatment on the first side did not completely resolve the condition, then the bilateral code would still be appropriate.”

So with bilateral cataracts: H25.13 for the first surgery (both eyes still have the condition), then H25.12 for the second surgery on the left eye once the right has been resolved. The code follows what the patient still has, not what is being operated on that day.

Official source

“When laterality is not documented by the patient’s provider, code assignment for the affected side may be based on medical record documentation from other clinicians. If there is conflicting medical record documentation regarding the affected side, the patient’s provider should be queried for clarification. Codes for ‘unspecified’ side should rarely be used, such as when the documentation in the record is insufficient to determine the affected side and it is not possible to obtain clarification.”

This is one of the few places the Guidelines let a code rest on another clinician’s documentation. The unspecified-side code is the last resort, after the rest of the record and a query.

1. Check whether the code carries laterality.
2. Report the documented side; both sides → the bilateral code where one exists, otherwise both unilateral codes.
3. For a bilateral condition treated one side at a time, use the bilateral code until one side is resolved, then the unilateral code for the remaining side.
4. If the provider did not state the side, use other clinicians’ documentation; query if it conflicts; unspecified side only when clarification is impossible.

1. Age-related nuclear cataract, both eyes, first surgery on the right. H25.13 — the condition still exists on both sides.
2. Second surgery, left eye, right eye resolved. H25.12.
3. Cataract, side not stated by the provider; the operative note names the left eye. H25.12 on the other clinician’s documentation; query if the record conflicts.

• Right plus left codes when a bilateral code exists.
• The unilateral code for the first of two planned surgeries.
• The bilateral code at the second surgery after the first side is resolved.
• Unspecified side without attempting clarification.

• The side or sides affected, from the provider or another clinician.
• Whether the first-treated side has been resolved, for the second encounter.
• Conflicting statements of side, which require a query.