The Principal Diagnosis Effect

Cathie Wilde, RHIA, CCS - Director, Coding Services Outsourcing Leave a Comment

A sixty-nine year old male is admitted with severe abdominal pain and is found to have diverticulitis. He undergoes an open sigmoidectomy with pathology report revealing a peridiverticular abscess. The patient has other secondary conditions such as COPD, hypertension, Stage II chronic kidney disease, hypothyroidism and GERD. The coder codes K57.32 for the diverticulitis figuring the abscess will not make a difference since with ICD-10-CM diverticulitis with abscess is now a combination code (K57.20). So she does not bother to query the physician regarding the pathology finding of abscess. Grouping the chart under MS-DRGs with the appropriate codes finds the following:

Principal Dx K57.32
Secondary Dxs J44.9 I12.9 N18.2 E03.9 K21.9
Principal Procedure 0DTN0ZZ DRG 331 Weight 1.6623


However, had the coder queried the physician regarding the abscess finding on the pathology report and it was confirmed, the MS-DRG grouping would look like this:

Principal Dx K57.20
Secondary Dxs J44.9 I12.9 N18.2 E03.9 K21.9
Principal Procedure 0DTN0ZZ DRG 330 Weight 2.5405


The above is one example how the reimbursement methodology for Medicare Severity Diagnosis Related Group (MS-DRG) has been affected by the implementation of ICD-10. There are certain codes when assigned as Principal Diagnosis that act as their own complication/comorbidity (CC) or major complication/comorbidity (MCC). Some of these diagnoses include:

  • B37.7              Candidal sepsis
  • L89.313           Pressure ulcer of right buttock, stage 3
  • I25.110            Atherosclerosis heart disease of native coronary artery with unstable angina
  • K50.112          Crohn’s disease of large intestine with intestinal obstruction
  • K80.30            Calculus of bile duct with cholangitis, unspecified, without obstruction
  • N11.1              Chronic obstructive pyelonephritis

Note: the links above are for FY 2017

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