CPT code 78645: CSF shunt study, shunt patency assessment2026 Medicare rate & RVUs

Medicare pays $285.24 for 78645 nationally in the office. Local office rates run $246.74–$402.69.

Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.

What 78645 covers

This study evaluates flow through an implanted cerebrospinal fluid shunt, commonly when symptoms or other findings raise concern for obstruction or malfunction. A nuclear medicine team administers radiotracer through the shunt access point and obtains images to follow its movement through the shunt pathway. The study may help assess whether flow is occurring and where it appears impaired.

Report 78645 for the shunt-focused radionuclide evaluation, rather than a study directed at general CSF circulation, ventricular imaging, or leak localization. Documentation should identify the clinical concern, the shunt evaluated, the radiotracer administration and imaging performed, and the interpretation of tracer progression. CMS recognizes professional and technical components: report modifier 26 for the interpretation, modifier TC for equipment and staff, or no component modifier for the global service. The professional and technical components are separately priced.

This summary was written with AI assistance from CMS physician fee schedule data and checked against the CMS billing rules shown here. Rates on this page come directly from CMS files.

Where 78645 pays more and less

The same RVUs, adjusted for each area’s costs. Open a locality for its calculation, history and nearby areas.

109 of 109 payment localities

78645 rates by state

Office rate range in each state. Select a state to see its payment localities.

How the 78645 rate is calculated

Each of 78645’s three RVUs is multiplied by a geographic index (GPCI) for the payment locality, added up, and multiplied by the conversion factor. Drag the indexes or enter a ZIP to see what moves the rate.

Payment rules and modifiers for 78645

The CMS indicators that decide how 78645 is paid alongside other services.

What modifiers do to the payment

When to use modifier 26

78645 compared with similar codes

How to choose

78630CSF scanCisternography

Choose 78645 for radionuclide evaluation of an implanted shunt. Code 78630 addresses CSF circulation through cisternography.

78635CSF imagingVentricular flow study

Code 78635 is directed at ventricular CSF imaging; 78645 follows tracer through a CSF shunt.

78650CSF leak imagingLeak detection and localization

Code 78650 is used for imaging directed at CSF leakage. Use 78645 when the clinical question concerns shunt flow or patency.

Codes related to 78645

Related codes aren’t interchangeable: bill the code that matches the service performed.

Where these rates come from

FeeBase calculates base physician payments from CMS work, practice-expense and malpractice RVUs, adjusted by each locality’s geographic indexes and the conversion factor. Services without a published rate are labeled, never given a made-up amount. Amounts are Medicare allowed amounts before claim adjustments: not a patient’s bill or a commercial rate.

CMS RVU26D · effective Oct 1, 2026 through the day before Jan 1, 2027

Open CMS sourceHow we calculate rates