CPT Code 90999: Unlisted Dialysis Procedure, Inpatient or Outpatient

CPT 90999 covers unlisted dialysis procedures not defined by existing codes. Read the guide to learn documentation and billing rules, plus related codes.

Use Code

What is CPT code 90999?

CPT code 90999 describes dialysis-related services or procedures that lack a specific code within the standard dialysis coding set. It is typically used by qualified health care professionals to report unusual, new, investigational, or highly specialized dialysis services in ESRD facilities or other clinical settings. Unlike defined codes for peritoneal dialysis procedures or standard hemodialysis (e.g., CPT 90935), 90999 requires clear clinical justification due to its unspecified nature.

Providers might use CPT 90999 for services such as unique dialysis-aided continuous renal replacement therapies (CRRT), specialized combined extracorporeal therapies, or novel dialysis modalities that address specific clinical needs not covered by existing codes. Proper documentation to substantiate the medical necessity and appropriateness of this unlisted code is essential for payer acceptance.

What is an unlisted dialysis procedure?

An unlisted dialysis procedure is a renal replacement therapy or dialysis-related intervention without an established CPT code. Such procedures include experimental treatments, specialized apheresis with dialysis components, hybrid dialysis methods, or certain continuous renal replacement therapies (CRRT). They are typically necessary in complex clinical situations, often involving end stage renal disease (ESRD) patients who require treatments beyond routine dialysis to manage their condition.

CPT code 90999 documentation requirements

Due to its classification as an unlisted service, CPT code 90999 requires comprehensive documentation to justify its use.

Detailed description of the procedure

Provide an in-depth narrative explaining precisely what the dialysis session performed involved, including step-by-step details.

Clinical rationale for unlisted code selection

Clearly state why no existing dialysis-related CPT code adequately describes the procedure performed. Describe the clinical context and necessity for this unique service.

Date, duration, and clinical setting

Document the exact date of service, total treatment duration, and clinical setting (inpatient, outpatient, ESRD facilities).

Comparison with existing CPT codes

Include a comparative analysis indicating how this procedure differs significantly from similar established dialysis codes, like peritoneal dialysis procedures or standard hemodialysis.

Equipment and supplies used

Specify any specialized equipment, consumables, or technology essential for the dialysis procedure, especially those not typically employed in conventional dialysis treatments.

A detailed cover letter or supplementary report is often required to facilitate appropriate payer assessment.

CPT code 90999 billing guidelines

Billing CPT 90999 accurately requires adherence to specific payer guidelines and comprehensive supporting documentation.

Prior authorization requirement

Most payers, including Medicare, mandate prior authorization due to the non-specific nature of this code. Confirm approval before performing or billing the procedure.

Mandatory supporting clinical documentation

Attach detailed clinical justification and procedural descriptions to claims to clearly support the use of this unlisted dialysis procedure.

No assigned RVU or standard payment rate

Unlike standard dialysis codes, 90999 has no relative value unit (RVU). Payment is determined individually by payers based on submitted documentation and comparative codes.

Use of comparative codes for pricing

Payers frequently require referencing similar dialysis services for pricing comparisons. Identify a comparable standard dialysis code (e.g., CPT 90935 or 90945) and document why the chosen comparator is suitable.

Modifiers for CPT code 90999

Usually, code 90999 is not used with modifiers, but some may apply depending on payer-specific policies and clinical circumstances:

Modifier KX: Indicates dialysis sessions exceeding standard frequency limits, applicable for additional payments.
G modifiers (G1-G5): Specify frequency of dialysis treatments (typically for ESRD patients receiving dialysis seven or more times monthly).
XE, XP, XS, XU: Indicate distinct procedural encounters or non-overlapping dialysis services to clarify separate claims submitted for unusual dialysis treatments.

Confirm modifiers with payer-specific guidelines, such as those outlined in the Medicare Benefit Policy Manual, to avoid claim denials or payment delays.

Other relevant CPT codes

When possible, providers should select the most appropriate dialysis-specific CPT codes. Related codes include:

90935: Hemodialysis procedure with single physician evaluation during the treatment.
90937: Hemodialysis with repeated evaluations during the treatment week.
90945: Single evaluation for peritoneal dialysis procedures.
90947: Peritoneal dialysis with multiple provider evaluations during the week.
99212–99215: These codes for office visits may be used for separate evaluation and management services provided to dialysis patients outside of the dialysis session itself, when not bundled with other dialysis procedures.

Frequently asked questions

Use CPT code 90999 only when the dialysis-related procedure or service performed is not described adequately by any existing dialysis-specific CPT codes.

Yes, typically prior authorization is required due to the unspecified nature of the procedure. Always verify payer-specific rules before billing.

Payment for CPT 90999 depends entirely on submitted clinical documentation and comparative analysis with similar dialysis codes. Payers individually review claims to establish appropriate reimbursement.