Understanding the Differences Between Modifiers 58 and 78 in Medical Coding One of the most…
Understanding Modifiers 50, 51, and 59
If you’re a medical coder, understanding medical coding modifiers is essential for submitting accurate claims and receiving correct reimbursement. Modifiers 50, 51, and 59 are among the most commonly used—and often misunderstood—CPT modifiers in the coding world.
Let’s simplify what each of these modifiers means, when to use them, and how they impact your coding accuracy and payment success.
Modifier 50 – Bilateral Procedure
Modifier 50 is used when the same procedure is performed on both sides of the body during a single session. This usually applies to paired organs or limbs, such as arms, legs, kidneys, or breasts.
✅ Example:
A patient undergoes a mastectomy on both breasts. You would append Modifier 50 to show that the surgery was performed bilaterally.
This modifier is common for arthroscopies, joint procedures, and other surgeries involving symmetrical body parts.
⚠️ Important: Only use Modifier 50 if the CPT code description does not already specify “bilateral.”
When understanding medical coding modifiers, remember that Modifier 50 focuses on procedures performed on both sides—mirror image work done in one session.
Modifier 51 – Multiple Procedures
Use Modifier 51 when more than one procedure is performed during the same encounter, especially when the procedures are unrelated.
You’ll report the primary procedure normally, and apply Modifier 51 to the additional procedures.
✅ Example:
A patient has abdominal surgery and a leg procedure during the same visit. You would apply Modifier 51 to the second procedure code.
Modifier 51 signals to the payer that multiple procedures were medically necessary, even though secondary services might be reimbursed at a reduced rate.
Understanding where Modifier 51 fits in your workflow is a core part of understanding medical coding modifiers and how to apply them correctly during complex encounters.
Modifier 59 – Distinct Procedural Service
Modifier 59 identifies procedures or services that are not typically reported together but are appropriate to bill separately under specific circumstances. It’s used to indicate that a service was distinct and independent from another performed on the same day.
Use Modifier 59 when no other modifier fits, and you need to clarify that a procedure should be unbundled.
✅ Example:
During a colonoscopy, a biopsy is performed at a different site. You’d use Modifier 59 to differentiate the biopsy from the main procedure.
💡 Modifier 59 is essential to avoid bundling and ensure accurate payment for services that might otherwise be denied or grouped.
A solid grasp of Modifier 59 is key to understanding medical coding modifiers that deal with distinct services.
Summary of Modifiers 50, 51, and 59
Here’s a quick way to remember each one:
- Modifier 50 = Bilateral procedures (same procedure, both sides)
- Modifier 51 = Multiple procedures (same session, unrelated)
- Modifier 59 = Distinct procedures (not bundled, separate)
Understanding medical coding modifiers like these ensures proper documentation, clean claim submission, and improved reimbursement outcomes. Even small misuses can lead to denials or payment reductions—so applying them correctly is critical.
- Novitas Solutions – Modifier 50 Fact Sheet: https://www.novitas-solutions.com/webcenter/portal/MedicareJL/pagebyid?contentId=00144531
Modifier 51: Multiple Procedure Novitas Solutions – Modifier 51 Fact Sheet:
- https://www.novitas-solutions.com/webcenter/portal/MedicareJH/pagebyid?contentId=00144532
- Modifier 59: Distinct Procedural Service
Centers for Medicare & Medicaid Services (CMS) – Proper Use of Modifiers 59, XE, XP, XS, and XU:
by Shika Reeves – AMCI Editorial Intern