CPT codes form the standardized language used to describe medical services and procedures for administrative purposes across the United States healthcare system. These five-digit codes ensure uniform reporting for billing and claims processing by physicians and facilities. CPT code 73718 specifically identifies a diagnostic service utilizing Magnetic Resonance Imaging (MRI) technology. It represents an examination of the lower extremity performed without the use of intravenous contrast material.
Description and Anatomical Scope
CPT code 73718 is formally defined as a Magnetic Resonance Imaging study of the “lower extremity other than joint; without contrast material(s).” This code applies to non-articular areas of the leg, such as the thigh (femur region), the lower leg (tibia and fibula), or the foot and ankle regions when the scan is not centered on a specific joint capsule. This distinction separates it from MRI procedures focused on specific joints, like the knee or ankle, which use different CPT codes. MRI uses powerful magnetic fields and radio waves to create detailed, cross-sectional images of soft tissues, muscles, and bone marrow.
The non-contrast nature means no specialized dye is injected into the patient’s vein before or during the scan. This approach is selected when the suspected pathology is well-visualized by the intrinsic tissue contrast provided by the MRI technology. Since the procedure is non-invasive and does not involve ionizing radiation, it is a preferred method for evaluating many musculoskeletal issues.
Clinical Reasons for Ordering the Test
A physician orders CPT 73718 when a patient presents with symptoms such as persistent leg pain, swelling, or unexplained changes in function, where the suspected issue lies primarily in the muscles, tendons, or bone shaft, rather than the joint surfaces. Primary indications include the evaluation of muscle tears, such as a hamstring or calf strain, and ligament injuries outside of a joint. It is frequently used to assess soft tissue masses or characterize suspected infections like cellulitis or osteomyelitis when contrast enhancement is not initially necessary.
The scan is also effective in detecting subtle or occult bone abnormalities, such as stress fractures, which may not be visible on conventional X-rays. Because MRI provides excellent visualization of bone marrow, it can identify the early signs of a stress reaction before it progresses to a full fracture. Furthermore, it can evaluate chronic conditions like tendinopathy or investigate potential nerve entrapment syndromes in the lower limb.
Distinctions from Contrast-Enhanced MRI Codes
The defining difference between CPT 73718 and its related codes is the use of an intravenous contrast agent, typically a Gadolinium-based substance. Contrast material alters the magnetic properties of tissues, enhancing the visibility of structures on MRI images. This enhancement is useful for highlighting areas of increased blood flow, which may indicate inflammation, active infection, or the presence of a tumor.
If contrast is clinically warranted, the procedure is not billed as 73718. A non-joint MRI with contrast is coded as 73719, or 73720 if both non-contrast and contrast sequences are performed. The decision to use contrast is a clinical one, driven by the patient’s symptoms and suspected diagnosis; for example, a suspected aggressive tumor or abscess requires contrast to fully delineate its borders and activity. CPT 73718 must also be distinguished from CPT 73721, which codes for a lower extremity joint MRI without contrast.
Specific Modifiers and Documentation
For accurate administrative reporting, CPT 73718 requires the use of specific add-ons called modifiers. Since the lower extremity is a paired body part, a laterality modifier is mandatory to specify which leg was scanned: -RT for the right lower extremity or -LT for the left lower extremity. This ensures the record accurately reflects the site of the procedure for reimbursement.
The service is often split into two distinct components for billing purposes. The professional component, designated by modifier -26, covers the radiologist’s interpretation and final report generation. The technical component, indicated by modifier -TC, covers the facility’s costs, including the use of the MRI equipment, the technologists’ time, and the supplies. Proper documentation is also required, including a detailed clinical indication that establishes medical necessity and a comprehensive report detailing the findings and diagnostic impression.