The Definitive Guide to the CPT Code for MRI Sacrum and Coccyx

If you are navigating the complex world of medical billing, radiology, or even just trying to understand an estimate for your own healthcare, you have likely landed here with one pressing question: what is the correct CPT code for an MRI of the sacrum and coccyx?

It seems like a simple question, but in the world of medical coding, simplicity is often an illusion. The sacrum and coccyx, the triangular bone at the base of your spine and the tiny tailbone below it, occupy a unique anatomical space. They are part of the spine, yet they are also the terminal end of it. This ambiguity often leads to confusion for billers, schedulers, and patients alike.

Getting this code right is crucial. Using the wrong code can lead to denied claims, delayed treatments, and unnecessary financial stress. In this guide, we will strip away the complexity. We will look at the specific codes, the clinical reasons for the scan, the nuances of bundling, and how to ensure your billing is as accurate as the MRI images themselves.

We will explore this topic in a way that is clear, accessible, and reliable. Whether you are a medical coder, a radiology practice manager, or a patient trying to make sense of your medical bills, this article is designed to be your trusted resource.

Understanding the Anatomy: Sacrum and Coccyx

Before we dive into the numbers, it helps to understand what we are actually coding for. The sacrum is a large, triangular-shaped bone formed by the fusion of five vertebrae. It sits like a keystone between the two hip bones, forming the back of the pelvis. Below the sacrum is the coccyx, or tailbone, a small triangular bone typically made of three to five fused vertebrae.

When a physician orders an MRI of this region, they are usually looking for specific issues. These might include fractures (especially after a fall), tumors, infections, sacroiliitis (inflammation of the sacroiliac joints), or degenerative conditions. Because these bones are so close to the sacroiliac joints and the lumbar spine, the imaging protocol and the coding can sometimes overlap.

The Primary CPT Code: 72198

After extensive research and alignment with the American Medical Association’s (AMA) Current Procedural Terminology (CPT) manual, the most accurate and specific code for this procedure is CPT 72198.

CPT 72198 is officially defined as: Magnetic resonance (eg, proton) imaging, pelvis; without contrast material(s), followed by contrast material(s) and further sequences.

This is the code specifically designated for an MRI of the pelvis. But why is it a “pelvis” code and not a “spine” code? This is where the nuance comes in.

When a radiologist performs an MRI that centers on the sacrum and coccyx, the anatomical region being imaged is technically the pelvic region. The sacrum and coccyx are considered part of the bony pelvis. Therefore, the CPT code set for the pelvis (72195-72198) is the correct family to use, rather than the lumbar spine codes (72148-72158).

The MRI Pelvis Code Family (72195 – 72198)

To fully understand where 72198 fits, it is helpful to look at the entire family of MRI pelvis codes. These codes are distinguished by the use of contrast material (dye).

Important Note: The specific contrast codes have been updated. While many resources still list 72198, the current standard for an MRI of the sacrum and coccyx that requires both non-contrast and contrast sequences is CPT 72197. For a non-contrast study, CPT 72195 is appropriate.

Why the Lumbar Spine Codes Are Incorrect

A common mistake is to use a lumbar spine MRI code, such as CPT 72148 (MRI lumbar spine without contrast), for a sacrum and coccyx study.

This is incorrect for several reasons. The lumbar spine codes cover the region from the lowest thoracic vertebrae down to the top of the sacrum (L1 through L5/S1 junction). While the sacrum is technically continuous with the lumbar spine, a dedicated sacrum and coccyx MRI requires a different field of view.

A radiologist using a “spine” protocol will focus on the spinal canal, nerve roots, and intervertebral discs. A “pelvis” protocol for the sacrum and coccyx focuses on the bone marrow, the sacroiliac joints, and the soft tissues of the gluteal region.

Using the wrong code can lead to:

• Claim Denials: Payers will see a mismatch between the procedure performed and the code billed.

• Incorrect Reimbursement: Spine codes and pelvis codes have different relative value units (RVUs), meaning they reimburse differently.

• Audit Risks: Consistent miscoding can trigger audits from Medicare or commercial payers.

Clinical Scenarios and Appropriate Coding

To make this more concrete, let’s look at a few scenarios. These real-world examples illustrate how you would choose the correct CPT code based on the physician’s order and the clinical indication.

Scenario 1: Trauma or Fracture

A patient falls down a flight of stairs and lands directly on their tailbone. They have severe pain localized to the coccyx. The ordering physician writes an order for an “MRI sacrum and coccyx without contrast” to rule out a fracture.

• Recommended Code: CPT 72195 (MRI pelvis without contrast)

• Reasoning: A non-contrast study is typically sufficient to evaluate for bone marrow edema indicative of a fracture. Contrast is rarely needed for straightforward trauma cases.

Scenario 2: Suspected Infection or Tumor

A patient presents with fever, unexplained lower back pain, and a history of cancer. The oncologist suspects a possible metastasis or osteomyelitis (bone infection) in the sacrum. The order specifies an “MRI sacrum and coccyx with and without contrast.”

• Recommended Code: CPT 72197 (MRI pelvis without contrast, followed by contrast)

• Reasoning: Contrast is essential for characterizing masses and identifying infections. The “before and after” study allows the radiologist to see how the tissue enhances, which is critical for diagnosing tumors and infections.

Scenario 3: Sacroiliac Joint Dysfunction

A patient has chronic lower back pain that is isolated to the region over the sacroiliac (SI) joints. The order is for an “MRI sacrum and coccyx without contrast” to evaluate the SI joints.

• Recommended Code: CPT 72195 (MRI pelvis without contrast)

• Reasoning: The sacroiliac joints are best visualized on a pelvic MRI protocol. A non-contrast study is usually the first-line imaging for evaluating inflammatory or degenerative changes in the SI joints.

Modifiers and Bundling: What You Need to Know

In medical coding, a CPT code is often just the starting point. Modifiers are two-digit codes that provide additional information about the procedure. When billing for an MRI of the sacrum and coccyx, you will rarely need a modifier, but there are exceptions.

The 26 Modifier (Technical vs. Professional Component)

This is the most common modifier in radiology. When an MRI is performed, there are two distinct components:

1. The Technical Component (TC): This covers the cost of the equipment, the technologist’s time, the supplies, and the facility overhead.

2. The Professional Component (26): This covers the radiologist’s time and expertise in interpreting the images and generating the report.

If you are a facility (like a hospital or imaging center) billing for the entire service, you would typically bill the CPT code without a modifier.
If you are a radiologist billing only for their interpretation services, you would append Modifier 26 to the CPT code (e.g., 72197-26).
If you are a mobile imaging company billing only for the use of the equipment, you would append Modifier TC.

Bilateral Procedures

Unlike some procedures, MRI scans are inherently bilateral. You do not add a modifier to indicate that both SI joints were imaged. The CPT code for the pelvis already covers the entire region, including both sides.

Billing for Multiple Regions: When the Sacrum and Coccyx Are Not Alone

What happens when the ordering physician wants to see the lumbar spine and the sacrum in the same visit? This is a common scenario, especially when a patient has complex back pain that spans from the lower back down to the tailbone.

In these cases, you cannot simply bill for two separate MRIs (a lumbar and a pelvis) if they were performed in a single session. Payers generally consider this “bundling” and will not reimburse for both separately.

Here is how to handle it:

• If the order is for a “Lumbar Spine MRI” and a “Sacrum MRI”: The correct approach is often to bill a single lumbar spine code (e.g., 72148) or a single pelvis code, depending on the primary focus. You cannot bill both.

• If the protocols are distinct and the documentation supports separate, medically necessary exams: Some coders use Modifier 59 (Distinct Procedural Service) or Modifier XU (Unusual Non-Overlapping Service) to indicate that the two scans were performed for different anatomical regions and are not typically performed together. However, this is a high-risk area for audits. You must have impeccable documentation from the radiologist and the ordering physician to justify two separate MRI codes in one session.

The Role of ICD-10-CM Diagnosis Codes

A CPT code tells the payer what you did. The ICD-10-CM (International Classification of Diseases, 10th Revision, Clinical Modification) code tells the payer why you did it. For the claim to be paid, the ICD-10 code must support the medical necessity of the CPT code.

When billing for an MRI of the sacrum and coccyx, your diagnosis codes should align with the pelvic region. Common ICD-10 codes include:

• M46.1: Sacroiliitis, not elsewhere classified

• S32.2XXA: Fracture of coccyx, initial encounter for closed fracture

• S32.1XXA: Fracture of sacrum, initial encounter for closed fracture

• C79.51: Secondary malignant neoplasm of bone (if looking for metastasis)

• M86.17: Other acute osteomyelitis, ankle and foot (or specific site codes for sacrum)

• M48.08: Spinal stenosis, sacral and sacrococcygeal region

• R10.2: Pelvic and perineal pain (when the exact cause is unclear but imaging is warranted)

A mismatch between the diagnosis and the CPT code is a primary reason for denials. For example, billing an MRI of the pelvis (72197) with a diagnosis code for “low back pain” (M54.5) might raise a red flag, whereas a code for “sacroiliitis” (M46.1) clearly supports the need for a pelvic MRI.

Insurance Authorization and Pre-Certification

Before the MRI is even scheduled, the provider’s office usually handles prior authorization. This is the process of getting approval from the insurance company before the service is rendered.

During this process, the CPT code plays a starring role. The insurance company will review the CPT code (e.g., 72197) and the diagnosis code to determine if the scan is “medically necessary.”

If you are a patient, it is wise to call your insurance company to confirm:

• Is prior authorization required?

• Is the CPT code (72195, 72196, or 72197) covered under my plan?

• What is my estimated out-of-pocket cost (deductible, copay, coinsurance)?

Being proactive about these questions can save you from a surprising bill later.

Medicare and National Coverage Determinations (NCDs)

Medicare has specific guidelines for the coverage of MRI procedures. For the sacrum and coccyx, the scan falls under the broader category of MRI of the pelvis.

Medicare typically covers MRI when it is used to evaluate:

• Malignant neoplasms

• Fractures not visible on X-ray

• Osteomyelitis

• Soft tissue masses

Medicare does not generally cover MRI for non-specific back pain without “red flags” (such as trauma, fever, or neurological deficit) that indicate a more serious underlying condition. The ordering physician must document these red flags clearly in the patient’s medical record to support the necessity of the MRI.

Frequently Asked Questions (FAQ)

Q1: Is there a specific CPT code for an MRI of just the coccyx?

No. There is no standalone CPT code for an MRI of only the coccyx. Because the coccyx is anatomically attached to the sacrum, any MRI of the coccyx is considered an MRI of the pelvis (codes 72195-72197).

Q2: What is the difference between CPT 72197 and 72198?

Historically, 72198 was used for an MRI of the pelvis with contrast. In the current CPT manual, 72197 is the standard code for an MRI of the pelvis without contrast, followed by contrast. Always consult your current CPT manual and payer policies, as using an outdated code like 72198 may result in a denial.

Q3: Can I bill for an MRI of the sacrum and an MRI of the lumbar spine on the same day?

Potentially, but it is complex. You would need to append a modifier like -59 or -XU to the secondary code to indicate it was a distinct and separate service. However, many payers consider this bundled. It is best to contact the payer in advance or ensure the radiology report clearly documents the medical necessity for two separate anatomical exams.

Q4: What is the “professional component” modifier for radiology?

The professional component modifier is -26. It is appended to the CPT code (e.g., 72197-26) when a radiologist is billing only for their interpretation services, typically when the MRI was performed at a hospital or facility that bills for the technical component.

Q5: How long does an MRI of the sacrum and coccyx take?

Typically, the scan itself takes between 30 and 45 minutes. If contrast is required, you should add an additional 15-20 minutes for the injection and post-contrast sequences.

Q6: Does an MRI of the sacrum and coccyx require a special diet or preparation?

Generally, no. Unlike a CT scan, there is no need to fast unless you are receiving contrast and your facility has specific protocols. You will be asked to remove any metal objects, jewelry, or clothing with metal fasteners.

Tips for Avoiding Claim Denials

Navigating the administrative side of radiology can be stressful. Here are a few practical tips to help ensure a smooth process from order to payment.

1. Verify the Order: Ensure the order is specific. An order for “MRI lumbar spine” when the actual need is for the sacrum will create a discrepancy. If the order is vague, ask for clarification before the patient arrives.

2. Confirm Laterality is Not an Issue: Since the code is for the pelvis, you do not need to specify left or right. This simplifies things compared to coding for extremities.

3. Document Contrast Necessity: If you are using contrast (CPT 72197), ensure the ordering physician or radiologist has documented the medical necessity (e.g., “rule out tumor,” “evaluate for osteomyelitis”) in the order. This is a common audit trigger.

4. Stay Updated: CPT codes can change annually. While the 72195-72197 family has been stable, it is crucial to use the most current year’s CPT manual for coding.

5. Educate Front-Office Staff: The staff scheduling the MRI and obtaining prior authorization should understand that the sacrum/coccyx falls under “pelvis” codes. This prevents them from seeking authorization for a lumbar spine MRI when it is not appropriate.

A Note on Patient Experience

While our focus is on coding, it is important to remember that behind every CPT code is a person. For patients, an MRI can be an anxious experience. The machine is loud and confining, and the wait for results can be stressful.

If you are a patient reading this to understand your upcoming procedure, you should know that an MRI of the sacrum and coccyx is a routine, non-invasive procedure. You will lie on your back on a table that slides into the MRI machine. You may be given a “call button” to hold in case you feel uneasy. The technologist will communicate with you throughout the scan via an intercom.

Understanding the code (72195, 72196, or 72197) can also empower you to verify with your insurance that everything is in order before the big day, giving you one less thing to worry about.

Additional Resource: The ACR Appropriateness Criteria

For those seeking a deeper, more clinical perspective, the American College of Radiology (ACR) Appropriateness Criteria is an invaluable resource. This evidence-based guide helps referring physicians and radiologists determine the most appropriate imaging exam for a given clinical condition.

For conditions like low back pain, sacroiliitis, or suspected fractures, the ACR provides ratings on whether an MRI, CT, X-ray, or other modality is the best choice. You can access these criteria through the ACR website. They serve as a gold standard for justifying medical necessity.

Link to ACR Appropriateness Criteria

Conclusion

Finding the correct CPT code for an MRI of the sacrum and coccyx comes down to understanding anatomy and the structure of the CPT manual. The procedure is classified under pelvic MRI, with the most common codes being 72195 for non-contrast studies and 72197 for those requiring contrast.

Accuracy in coding ensures proper reimbursement, reduces administrative headaches, and supports the overall efficiency of the healthcare system. By focusing on the specifics of the exam and aligning them with the correct code family, providers can minimize denials and patients can better understand the process. Remember, when in doubt, clear communication between the clinical team, the billing department, and the patient is the key to success.