Part 9: Most Common DRG’s with Recommendations – DRG 640

This is the next most common DRG with recommendations found in HIA reviews in 2021. Just to recap, HIA reviewed almost 50,000 inpatient records and over half a million codes in 2021. We will look at the top DRG’s with recommendations and see what can be done to prevent DRG changes going forward. Each coding tidbit will contain some tips for coding within the DRG or diagnosis area. 


#9: DRG 640—Miscellaneous disorders of nutrition, metabolism, fluids, and electrolytes with MCC

DRG 640 (Miscellaneous disorders of nutrition, metabolism, fluids, and electrolytes with MCC) was the number 9 most common DRG with recommendations from HIA in 2021.


Records reviewed: 398
DRG recommended changes: 53
Accuracy of DRG 640: 86.68%


There are over 100 diagnoses that if reported as the PDX would group to DRG 640. The most common that coders see is malnutrition, dehydration, hypovolemia, hyper/hyponatremia, fluid overload, and other electrolyte abnormalities. More than 41 million Americans suffer from malnutrition. Research shows that 75% of Americans are chronically dehydrated. One of the documents stated that if you are thirsty, you are dehydrated. Thirst is the bodies trigger when you are becoming dehydrated. Did you know that dehydration and hypovolemia are NOT the same? And, Yes you can have both at the same time. Hypovolemia is when the extracellular fluid volume is reduced. Dehydration refers to total-body water loss.


Reasons for DRG 640 recommendations:

The majority of the recommendation from DRG 640 (Miscellaneous disorders of nutrition, metabolism, fluids, and electrolytes with MCC)  were due to MCC’s or PDX changes (more than half required physician query to support the recommendation).

  • The most common reason for change was recommendations to delete the reported MCC. The majority did require a physician query to support the MCC that had been reported at original coding. There were only a couple that were removed due to clear documentation in the medical record. What this means is that MCC’s are being reported on records that the physician documentation does not support. Queries were recommended for clarification of inconsistent or unclear documentation on most. Remember when a possible condition is mentioned in the record, it must either be a confirmed diagnosis at the time of discharge or still listed as a possible condition at the time of discharge.
  • The next most common reason for DRG recommendations was to re-sequence or add a new PDX. About half of these recommendations did require a physician query to clarify the recommended PDX.
  • The two most common DRG’s that were recommended were DRG 641 (Miscellaneous disorder of nutrition, metabolism, fluids, and electrolytes without MCC).

What can coders do to improve the accuracy of reporting DRG 640?

The most important thing that a coder can do is to make sure that there are no questions that could be raised regarding any diagnosis that is used to calculate the DRG. Ask yourself these questions when coding:

  • Validate all MCC’s to ensure that documentation is in the medical record to support that these conditions should be reported. If there’s a chance that the condition may be ruled out, a query should be sent for clarification. When only 1 MCC is present on a record it is always best practice to double check to ensure that the condition meets reporting requirements as well as clinical validity so that it is protected in any audits.
  • If there is a question about a diagnosis in the record that does impact the DRG, a query should be sent or coders should follow the procedure for their facility to escalate the record to a senior reviewer or physician liaison.
  • Verify the reasons for the patient’s admission. When multiple conditions necessitate the admission, and equally meet the criteria for principal diagnosis, any of these may be sequenced first. The circumstances of inpatient admission always govern the selection of principal diagnosis. The principal diagnosis is defined in the Uniform Hospital Discharge Data Set (UHDDS) as “that condition established after study to be chiefly responsible for occasioning the admission of the patient to the hospital for care.”
  • Look for underlying etiology for the conditions and follow any chapter specific guidelines or index directives.
  • Query anytime there is ambiguous of conflicted documentation prior to coding finalization
  • Bottom line is to protect the DRG at final coding by making sure that it is correct, and that there will be no question after final billing about the ICD-10-CM and/or ICD-10-PCS codes that were reported.

Coders should review the entire medical record to look for any conflicting documentation and clarify this prior to final coding. Clarification prior to final coding will decrease audit recommendations and denials. Remember, denials are costly to the facility with all the time that is spent trying to appeal.



ICD-10-CM Official Guidelines for Coding and Reporting FY 2022

ICD-10-PCS Official Guidelines for Coding and Reporting FY 2022

The information contained in this coding advice is valid at the time of posting. Viewers are encouraged to research subsequent official guidance in the areas associated with the topic as they can change rapidly.

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