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MS-DRG 399 · MDC 06 · Surgical

MS-DRG 399: Appendix Procedures without CC/MCC

Reviewed by QuickIntell RCM Editorial Team · Last reviewed

Data effective
Data currency: IPPS Table 5 FY2027 final rule (effective October 1, 2026); Definitions Manual v44 (effective October 1, 2026). Next CMS release: April 1, 2027 (v44.1 mid-year update), then the FY2028 final rule in August 2027.

Key facts for DRG 399

FY2027 relative weight
1.2030
Higher than 32% of all MS-DRGs
Change vs FY2026
+5.1%
FY2026 weight 1.1450
Geometric mean LOS
1.8 days
Arithmetic mean 2.1 days
MDC
06
Assignment of Diagnosis Codes
Severity level
without CC or MCC
Transfer policy
Not a transfer DRG

TL;DR

MS-DRG 399 is a surgical group in MDC 06 (Assignment of Diagnosis Codes) at the base severity level of its family. CMS assigns it a FY2027 relative weight of 1.2030 with a geometric mean length of stay of 1.8 days and an arithmetic mean of 2.1. Its weight moved up 5.1% from FY2026 (1.1450). That weight is higher than 32% of all surgical and medical MS-DRGs. Its CC/MCC family (DRG 397, DRG 398) spans weights 1.2030 to 2.3830. The v44 Definitions Manual assigns it through 57 operating room procedures codes.

What changed from FY2026 to FY2027

CMS recalibrates every MS-DRG weight annually from the prior year's MedPAR claims. For DRG 399 the FY2027 relative weight is 1.2030 against 1.1450 in FY2026, a rise of 5.07%, which exceeds the 2% threshold worth re-checking in contract models.

FY2026 versus FY2027 payment factors for MS-DRG 399
MetricFY2026FY2027Change
Relative weight1.14501.2030+0.0580
Geometric mean LOS (days)1.81.8+0.0
Arithmetic mean LOS (days)2.22.1-0.1
Weights shown are the FY2027 final values after the 10% cap on year-over-year reductions where applicable.

CC and MCC family

DRG 399 shares its base definition with 2 other MS-DRGs split by severity. The family's weights span 1.2030 to 2.3830, a 1.98× spread, which is the payment effect of documenting qualifying complications and comorbidities.

MS-DRGs in the same base group as DRG 399
DRGTitleFY2027 weightGMLOS
397Appendix Procedures with MCC2.38304.7
398Appendix Procedures with CC1.52202.9
399Appendix Procedures without CC/MCC1.20301.8

Grouper logic (v44 Definitions Manual)

Operating Room Procedures: 57 ICD-10 codes drive assignment to this group; the first 12 are shown.

Operating Room Procedures codes assigned to DRG 399 (sample)
ICD-10 codeDescription
0D5J0Z3Destruction of Appendix using Laser Interstitial Thermal Therapy, Open Approach
0D5J0ZZDestruction of Appendix, Open Approach
0D5J3Z3Destruction of Appendix using Laser Interstitial Thermal Therapy, Percutaneous Approach
0D5J3ZZDestruction of Appendix, Percutaneous Approach
0D5J4Z3Destruction of Appendix using Laser Interstitial Thermal Therapy, Percutaneous Endoscopic Approach
0D5J4ZZDestruction of Appendix, Percutaneous Endoscopic Approach
0D5J7ZZDestruction of Appendix, Via Natural or Artificial Opening
0D5J8ZZDestruction of Appendix, Via Natural or Artificial Opening Endoscopic
0D9J00ZDrainage of Appendix with Drainage Device, Open Approach
0D9J0ZXDrainage of Appendix, Open Approach, Diagnostic
0D9J0ZZDrainage of Appendix, Open Approach
0D9J3ZXDrainage of Appendix, Percutaneous Approach, Diagnostic

Documentation and denial exposure

As a surgical DRG, assignment depends on a qualifying operating-room procedure being coded from the operative report; a missing or non-OR procedure code drops the stay into a medical DRG in MDC 06 with a lower weight. Because this family splits by severity, auditors target CC and MCC capture: each secondary diagnosis must be documented as present, monitored, evaluated or treated during the stay to survive a DRG-validation review. Typical inpatient denial codes for this group: CARC 16 (claim lacks information needed to group the stay), CARC 50 (the admission or procedure is judged not medically necessary), CARC 97 (a service is bundled into the DRG payment).

How QuickIntell uses DRG 399 data

QuickCode groups inpatient encounters against the current v44 logic, flags CC and MCC candidates that lack supporting documentation, and shows the weight difference across the family before the claim drops. QuickScribe captures the attending's language that supports severity, and QuickRCM works DRG-validation denials with the grouper evidence attached.

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Frequently asked questions — DRG 399

What is MS-DRG 399?

MS-DRG 399 is "Appendix Procedures without CC/MCC", a surgical Medicare Severity Diagnosis-Related Group in MDC 06, Assignment of Diagnosis Codes. Medicare pays inpatient stays grouped here at the hospital's base rate multiplied by the DRG relative weight.

What is the FY2027 relative weight for DRG 399?

The FY2027 relative weight is 1.2030 (IPPS final rule Table 5, effective October 1, 2026). In FY2026 it was 1.1450, a change of +5.1%.

What is the average length of stay for DRG 399?

CMS reports a geometric mean length of stay of 1.8 days and an arithmetic mean of 2.1 days for FY2027. The geometric mean is used for transfer-payment calculations.

Which DRGs are in the same CC/MCC family as 399?

DRG 397 (Appendix Procedures with MCC, weight 2.3830); DRG 398 (Appendix Procedures with CC, weight 1.5220). The family's weights range from 1.2030 to 2.3830, so documented complications and comorbidities change payment materially.

What documentation supports the severity level of DRG 399?

DRG 399 is the base-severity assignment: no secondary diagnosis on the CC or MCC lists was coded, or the only ones present are excluded for this principal diagnosis. Revenue-integrity review here looks for undercapture, meaning conditions treated during the stay (electrolyte disorders, specified anemia, acute blood loss, pressure injuries present on admission) that were never documented to the specificity the lists require. A compliant query to the attending, not a coder assumption, is the only way to move a stay to the CC or MCC sibling.

Which codes group to DRG 399?

The v44 Definitions Manual lists 57 operating room procedures codes for this group. Examples from the operating room procedures list: 0D5J0Z3 (Destruction of Appendix using Laser Interstitial Thermal Therapy, Open Approach); 0D5J0ZZ (Destruction of Appendix, Open Approach); 0D5J3Z3 (Destruction of Appendix using Laser Interstitial Thermal Therapy, Percutaneous Approach); 0D5J3ZZ (Destruction of Appendix, Percutaneous Approach).

Is DRG 399 a post-acute transfer DRG?

No. DRG 399 is not on the FY2027 post-acute care transfer list, so the transfer per-diem policy does not apply to it.

Sources

Every figure on this page is taken from the CMS publications below, as released by the Centers for Medicare & Medicaid Services. Projection built 2026-10-01. Verify against the primary file before billing or contracting decisions.

Disclaimer

This page is an operational reference compiled from the CMS IPPS FY2027 final rule (Table 5) and the v44 ICD-10 MS-DRG Definitions Manual. Relative weights are national factors; actual payment depends on each hospital's wage-adjusted base rate, add-ons, outliers and transfer adjustments. Nothing here is legal, clinical or billing advice; verify grouping against your encoder and the published CMS files.