DRG 921 Overview

DRG 921 covers hospital admissions for complications of medical or surgical treatment that do not qualify as a Major Complication or Comorbidity and do not meet Complication or Comorbidity criteria. Typical cases include postoperative infections, adverse drug reactions, device malfunctions, and non-severe procedure-related complications requiring inpatient care. This Diagnosis-Related Group matters for Medicare payment because it groups lower-severity treatment complications into a distinct reimbursement category that affects payment relative to the principal diagnosis and resource use. Hospitals and coders must correctly capture complication codes and principal procedures to ensure appropriate Medicare inpatient payment alignment.

• Acute perioperative complication management studies: randomized or observational studies testing protocols to rapidly identify and treat common in-hospital complications arising from procedures (for example, post-procedural bleeding, device-related infections, or medication-induced adverse events) in surgical and procedural patients without major comorbidities. These trials enroll adult inpatients who develop a complication of treatment during an index hospitalization and evaluate short-term interventions, diagnostic algorithms, or care pathways to shorten time-to-resolution and reduce escalation to higher-acuity care. Results inform clinicians and payers about resource use, appropriate escalation criteria, and cost-effective acute management strategies for patients assigned to this DRG.
• Comparative effectiveness studies of process-of-care bundles to prevent escalation: pragmatic trials or multicenter cohort studies comparing different standardized in-hospital response bundles (for example, wound-care protocols, device-check algorithms, or medication-reconciliation and adverse-event monitoring bundles) intended to prevent progression from a treatable complication to a complication with CC/MCC. These studies target hospitalized patients who are at risk of or have early signs of treatment complications, assessing rates of complication resolution, length of stay, readmissions, and utilization of ICU or advanced therapies. Findings are directly relevant to hospital quality improvement, DRG case-mix management, and payer decisions about coverage for bundled care pathways that may lower downstream costs.
• Post-discharge outcomes and readmission-prevention research: longitudinal cohort studies and interventional trials testing post-acute follow-up strategies (such as structured outpatient surveillance, telehealth monitoring, or targeted home health interventions) for patients discharged after inpatient treatment complications without CC/MCC. These studies focus on functional recovery, late sequelae of the complication, 30- and 90-day readmission rates, and patient-reported outcomes in a population that had a manageable in-hospital complication but may be vulnerable to recurrence or delayed consequences. Evidence from this research guides discharge planning, transitional-care reimbursements, and payer investments in outpatient supports that reduce readmissions and total cost of care for this DRG group.