Differences that Impact MS-DRGs: Crohn’s Disease with Intestinal Abscess

In my last blog, I got to indulge myself and say the things people love to hear about ICD-10 and potential MS-DRG shifts: the problem lies in ICD-9, bad ICD-9 coding is the culprit in this case, and life gets better under ICD-10.

This time I am going to bite the bullet and give you a less fun example of the third type of DRG shift of the three types I introduced in my first blog in this series. The third type of shift is where a correctly coded ICD-10 record may be assigned to a different MS-DRG than the same record coded and grouped in ICD-9 because of important differences in the ICD-10 classification itself.

In this example of a patient with Crohn’s disease (aka enteritis) and intestinal abscess, a correctly coded record requires two codes in ICD-9 (something in the range of 555.0-2.9 Regional enteritis of intestine plus 569.5 Abscess of intestine). Either the enteritis or the abscess code may be listed as the principal diagnosis, depending on whether the reason for admission was primarily for treatment of the abscess or for the Crohn’s disease.

When the Crohn’s disease code is listed as the principal diagnosis, the abscess of intestine code as a secondary diagnosis is a CC, and the record is assigned to DRG 386 Inflammatory bowel disease with CC. However, when the abscess of intestine code is listed as the principal diagnosis, the record is assigned quite a bit higher in the DRG hierarchy, to DRG 372 Major gastrointestinal disorders and peritoneal infections with CC.

A single stand-alone code for intestinal abscess is available in ICD-10: K63.0 Abscess of intestine, so one would think coding and predicted reimbursement would be identical. However, there are specific ICD-10 combination codes for Crohn’s disease with intestinal abscess (e.g., K50.014 Crohn’s disease of small intestine with abscess). These are the correct codes to use for abscess with underlying Crohn’s disease. Since the ICD-10 combination code is one code rather than two, there is no such thing as a sequencing option—whether the patient is admitted for treatment of the abscess or for treatment of the underlying Crohn’s disease, the code is the same.

One code, one MS-DRG option. In ICD-10 MS-DRGs, Crohn’s disease with abscess codes are assigned to the same MS-DRG as all the other Crohn’s disease codes. When listed as the principal diagnosis, the Crohn’s disease with abscess code is assigned to DRG 386 Inflammatory bowel disease with CC.  The CC is automatically assigned because it is on a list called “PDX is its own CC” in ICD-10 MS-DRGs. (This list is unique to the ICD-10 MS-DRGs in order to ensure that ICD-10 combination codes containing what would have been a separate ICD-9 code and that would have been a CC or MCC in the ICD-9 MS-DRGs will still yield the same CC/MCC status. It’s a good idea to check it out if you haven’t seen it yet.) Getting the CC you would have gotten in ICD-9 is excellent. Seeing an ICD-10 test record with a predicted MS-DRG of 386 instead of 372 is not so excellent.

This may be one of those unavoidable differences in predicted ICD-10 reimbursement where acceptance is the way to go. Because both the underlying Crohn’s disease and its associated intestinal abscess are specified in a single ICD-10 code, it is not possible to get creative with the sequencing and change MS-DRG assignment, even if the documentation supports it. That result has its good side—the coding profession spends a lot of mental energy on these ICD-9 chicken and egg sequencing conundrums, and from that point of view it is nice to see one of them go away. But somewhere out there is a giant Pez dispenser of gray areas in coding/classification/reimbursement: you get rid of one and the next one pops out.

Read on if you want to hear more, with this important caveat: this is about correct coding, not about how to squeeze more money out of the MS-DRGs.

It is not clear from current coding guidelines and classification whether the combination codes for Crohn’s disease with abscess include K61.1 Rectal abscess. ICD-9 classifies rectal abscess separately from intestinal abscess with code 566 Abscess of anal and rectal regions. Coded as the principal diagnosis in both ICD-9 and ICD-10, rectal abscess codes end up in the basement of the MS-DRG hierarchy for digestive system codes, at DRG 394 Other digestive system diagnoses w CC.

So the bottom line is, if the Crohn’s disease combination codes include rectal abscess (in other words, one code in ICD-10 is the correct way to code) and the rectal abscess code was the principal diagnosis in ICD-9 (two codes in ICD-9), then your predicted reimbursement is actually higher under ICD-10, at 386 Inflammatory bowel disease with CC instead of 394 Other digestive system diagnoses w CC.  However, if the Crohn’s disease combination codes do not include rectal abscess (two codes in ICD-10 is the correct way to code, same as ICD-9) and the rectal abscess is coded as the principal diagnosis in both ICD-9 and ICD-10, predicted reimbursement does not shift and you end up with the same MS-DRG in both cases, 394 Other digestive system diagnoses w CC . Yes, sometimes ignorance is bliss.

Rhonda Butler is a Senior Clinical Research Analyst with 3M Health Information Systems.

2 responses to “Differences that Impact MS-DRGs: Crohn’s Disease with Intestinal Abscess

  1. Rhonda, One question about the above blog. There is a coding guideline published in multiple Coding Clinic about Crohn’s disease and it’s manifestations. Per multiple Coding Clinics 2nd Q 1997, 3rd Q 1999, 4th Q 2012. if the Crohn’s disease is the underlying cause of the abscess, the Crohn’s disease must be the PDx. Actually the coding guideline is, if a patient has any complication/manifestation secondary to Crohn’s, the Crohn’s will always be the PDx.. So, wouldn’t all Crohn’s disease and it’s manifestation/complications still be grouped to MS-DRG 385, 386 or 387?

    • Kim, You are absolutely right, thanks for bringing it up. Although there is not an explicit “code first” note associated with the intestinal abscess code directing the coder to sequence Crohn’s disease as the principal diagnosis, there is a fair amount of Coding Clinic advice on the subject of Crohn’s disease with associated manifestations. All advice directs the coder to sequence the Crohn’s first before a documented manifestation of Crohn’s. But there still must be confusion on the subject, or else the ICD-9 data is not telling us something we need to know (i.e., whether or not the intestinal abscess and Crohn’s disease were in fact related). The MedPAR data show that a significant number of records are coded with intestinal abscess listed as principal diagnosis and Crohn’s disease as a secondary diagnosis. Hence the predicted DRG shifts. It is possible some portion of these records are in fact unrelated diagnoses: for instance the patient has an abscess of the large intestine and Crohn’s disease of the small intestine. We can’t know from the ICD-9 codes alone. But we absolutely know with the new ICD-10 combination codes when Crohn’s disease manifests with an intestinal abscess, because it is all right there in a single detailed code.

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