Health Information Management

Q&A: Unrelated surgical procedure DRGs

CDI Strategies, June 25, 2015

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Q: Could you please explain unrelated surgical procedure DRGs? Also can you explain how we can differentiate between extensive operating room (OR) procedure and non-extensive OR procedure.  

A: Many CDI specialists with a clinical background are “encoder dependent,” trained to “code” using an encoder and taught to create a working MS-DRG based on “grouper” software. However, CDI specialists should understand how to manually assign a MS-DRG, too. The basics steps for assigning a MS-DRG are.

  1. Identify all the reportable diagnoses in the health record and assign their applicable ICD code (we currently use ICD-9-CM, but will transition to ICD-10-CM)
  2. Identify the principal diagnosis (the condition “after study” determined to be chiefly responsible for occasioning the admission), the remaining diagnoses are secondary diagnoses some of which may be classified by CMS as a complicating or comorbidity (CC) or major complication or comorbidity (MCC)
  3. Use the alphabetic index of diagnoses in the DRG Expert to identify the base/medical MS-DRG noting its Major Diagnostic Category (MDC)/body system (the MDC is necessary to assign the surgical MS-DRG when applicable) by scanning the MS-DRGs associated with the listed pages to see which applies to the particular scenario
  4. Identify any/all reportable procedures and their associated procedure code (ICD-9-CM Vol. 3 until we transition to ICD-10-PCS)

The UHDDS (Uniform Hospital Discharge Data set) defines reportable diagnoses and procedures. Most coders and CDI specialists are familiar with the definitions associated with diagnoses, but less familiar with those associated with procedures. Only significant procedures need to be reported. According to UHDDS, a significant procedure is one that is:

  • Surgical in nature, or
  • Carries a procedural risk, or
  • Carries an anesthetic risk, or
  • Requires specialized training

In addition, UHDDS also defines the principal procedure as:

  • One that was performed for definitive treatment, rather than one performed for diagnostic or exploratory purposes, or was necessary to take care of a complication
  • If two procedures could be principal, then the one most related to the principal diagnosis should be selected

The UHDDS definitions of significant procedures is helpful because not all procedures will affect the MS-DRG. Some procedures won’t have any impact on the MS-DRG, some procedures will change the based medical MS-DRG, and some procedures will move the case to a surgical MS-DRG.

Procedures that are diagnostic in nature are less like to impact the MS-DRG assignment because they are typically performed in the outpatient setting, which is why they are less likely to be the principal procedure. Also, the principal procedure is usually related to the principal diagnosis, meaning they usually can be found in the same MDC/body system. ICD-10-PCS has specific guidelines regarding the assignment of the principal procedure.

If a procedure was performed, determine if it is significant:

  • If there are multiple significant procedures determine the principal procedure
  • Assign the procedure code(s) and use the numeric index in the DRG Expert to see if the code is listed. If the code isn’t in the DRG Expert index of procedures, is it because of one of the two following reasons:
    •  It is not a “reimbursable” procedure (i.e., one that will not affect the MS-DRG assignment)
    • It a major operating room procedure

Let’s explore the first situation, when the procedure doesn’t affect MS-DRG assignment. In this situation, finalize the base medical MS-DRG by checking the impact of secondary diagnoses. Are there any that are classified as CCs or MCCs? Are there any query opportunities to add a diagnosis that can affect the MS-DRG? Once the secondary diagnoses are addressed, the working MS-DRG is established, which can be revised as additional secondary diagnoses and/or procedures occur during the admission.

More often than not, the procedure code will be in the numeric index of procedures. The index lists possible associated MS-DRGs. If more than one page is listed, check each of the possible associated MS-DRGs to see if any are located in the same MDC as the principal diagnosis (this is why it was important to note the MDC when assigning the base medical MS-DRG).

As long as the procedure maps to a MS-DRG that is in the same MDC as the principal diagnosis the applicable MS-DRG can be assigned. Finalize the working MS-DRG by assessing the impact of all relevant secondary diagnoses

The MS-DRG system assumes that the medical intervention/procedure will remain in the same body system (MDC) as the principal diagnosis. However, sometimes the principal procedure is not related to the principal diagnoses because it is associated with a different MDC/body system, which requires additional steps to determine the applicable MS-DRG.

  1. Turn to the “DRGs Associated with All MDCs” chapter in the DRG Expert
  2. Scan the procedure codes listed under DRG 984 Prostatic O.R. Procedure Unrelated to PDX for the procedure code associated with your case. These are codes that range from 60.0 to 60.99 within ICD-9-CM Vol. 3
  3. If the applicable code is found under DRG 984 then the case will fall within a DRG referred to as a “triplet” where either a CC or a MCC can “move” the DRG
  4. Check the remaining diagnoses codes to see if any are classified as a CC or MCC and finalize the DRG based on the value of the applicable secondary diagnoses resulting in a DRG between 984 and 986

For example, a principal diagnosis of pneumonia would lead to a base medical MS-DRG in the respiratory system MDC. A transurethral resection of the prostate (TURP) procedure is found within the numeric index to procedures, but none of its associated MS-DRGs are located within the respiratory body system. There is a mismatch between the body system of the principal diagnosis and those associated with the procedure. A scan of the procedure codes listed under MS-DRG 984 locates the applicable procedure code. The final MS-DRG assignment depends on the presence or absence of secondary diagnoses classified as a CC or MCC.

If the procedure code is not found under DRG 984, scan the list under DRG 987 Nonextensive O.R. Procedure Unrelated to PDX for the applicable procedure code. These codes span several pages within the DRG Expert. If the code is found, determine the impact of the secondary diagnoses to assign the working MS-DRG.

When the procedure code isn’t listed in the procedure indexes or the MDC didn’t match that of the principal diagnosis and was not listed under DRG 984 or DRG 987—then the assumption is the case belongs in DRGs 981-983. Assess the impact of secondary diagnoses to assign the working MS-DRG.

This final step requires a leap of faith, since it is based on a process of elimination where this is the “last resort” for DRG assignment. These DRGs are heavily scrutinized by auditors, as assignment within these DRGs can erroneously inflate reimbursement if the case is improperly assigned. Although some organizations try to avoid the reporting of DRGs 981-983, it can be an accurate MS-DRG assignment as long as the documentation supports the assignment of the principal diagnosis.

Editor’s Note: Cheryl Ericson, MS, RN, CCDS, CDIP, AHIMA Approved ICD-10-CM/PCS Trainer, CDI Education Director for HCPro Inc. and Associate Director of ACDIS for Education, answered this question. Contact her at For information regarding CDI Boot Camps offered by HCPro visit

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