MS DRG Case of the Month #6: Answer

Optimal DRG:  616  AMPUTAT OF LOWER LIMB FOR ENDOCRINE,NUTRIT,& METABOL DIS W MCC

 This month’s case is one of the best — vis a vis being a teaching example.  Even most of our superstar docs failed to come up with the correct answer, which involved knowing the coding rules well enough to reassign the principal diagnosis, and understanding the application of SIRS in order to add a MCC.

Principal Diagnosis

· The H&P and Discharge Summary document that the patient was admitted for elective below-knee amputation resulting from osteomyelitis of the right ankle.  Osteomyelitis was clearly the condition that was most responsible for this admission.  Coding Clinic First Quarter 2004 pages 14-15 advises that ICD-9 assumes a relationship between diabetes and osteomyelitis when both conditions are present, unless the physician has indicated in the medical record that the acute osteomyelitis is totally unrelated to the diabetes.  ICD-9 coding guidelines state that the basic disease category serves as the primary code to classify both the disease (Diabetes) and its major manifestations.  Coding Clinic Fourth Quarter 1997 advises that, for diabetic osteomyelitis, Diabetes with other specified manifestations (250.8x) is sequenced first, followed by Other bone involvement in diseases classified elsewhere (731.8) and the appropriate code for osteomyelitis (730.27 in this case).  Sequencing the basic disease category code (250.80) ahead of the osteomyelitis code (730.27) results in a change from DRG 475 Amputation for Musculoskeletal System and Connective Tissue Disease with CC  to DRG 617 Amputation of Lower Limb for Endocrine, Nutritional and Metabolic Diseases with CC.

· Principal diagnosis 250.40 Diabetes with renal manifestations  (instead of 250.80 Diabetes with specific manifestations) would result in DRG 982 Extensive OR Procedure Unrelated to Principal Diagnosis with MCC.  DRG 982 has a higher case weight than DRG 617, so should 250.40 be the principal diagnosis?  Probably not, for two reasons.  First, Coding Clinic Fourth Quarter 1997 directs that the appropriate diabetes code is 250.8x.  Second, the reason for the admission was diabetic osteomyelitis, the "other specified manifestation" of diabetes to which principal diagnosis 250.80 refers.  If the patient had been admitted for diabetic nephropathy, 250.40 may have been the appropriate principal diagnosis.

Secondary Diagnoses

· It would be reasonable to query for Acute renal failure in this case.  The patient had a rapid substantial rise in creatinine postoperatively.  Acute kidney injury (584.9) would be a MCC with an Osteomyelitis principal diagnosis (730.27).  However, the MS-DRG grouper doesn't recognize Acute kidney injury (584.9) as an MCC with Diabetes principal diagnosis 250.80.  The Osteomyelitis code (730.27) and the Ulcer codes (459.11 and 707.12) are CCs with a Diabetic principal diagnosis.  Should we be happy with our Amputation with CC DRG (DRG 617) and call it a day?  Maybe not.

· The patient had a postoperative fever, coded as Post procedural fever (780.62).  The patient developed a temperature of 102, pulse of 100, respirations 22, confusion, rise in creatinine, abnormal liver function tests, and a WBC count of 16,000. No infectious condition was found or suspected. These findings are consistent with Systemic Inflammatory Response Syndrome (SIRS) due to noninfectious process with acute organ involvement (995.94), an MCC.  It seems reasonable to query for secondary diagnosis 995.94, since strong clinical indicators for SIRS are documented.