A comprehensive guide to inpatient coding, DRG factors, patient types, and medical record review — everything a coder needs to navigate the inpatient world with confidence.
Inpatient coding is the process of translating clinical documentation from a hospital stay into standardized ICD-10-CM/PCS codes. These codes drive reimbursement, quality reporting, and resource allocation for admitted patients.
What Is IPDRG?
IPDRG stands for Inpatient Diagnosis-Related Group. It is a Medicare payment classification system that groups hospital cases with similar clinical characteristics and resource use into a single payment category. Each DRG carries a specific weight that determines reimbursement.
The final DRG is determined after all diagnoses and procedures are coded and submitted on the claim.
DRG Factors
Key Factors That Drive DRG Assignment
Principal Diagnosis
The condition established after study to be chiefly responsible for the admission — the single most important DRG driver.
Secondary Diagnoses
Comorbidities (CC) and Major Comorbidities (MCC) that significantly affect resource use and can upgrade the DRG weight.
Procedures (ICD-10-PCS)
Significant OR procedures performed during the stay can shift the case to a surgical DRG, dramatically changing reimbursement.
Patient Demographics
Age, sex, and discharge disposition (e.g., home, SNF, expired) are factored into specific DRG groupings.
Patient Types
Inpatient Patient Types
👶 Newborn
Birth encounters coded with liveborn infant codes (Z38.x). Separate DRG groupings apply for normal newborns vs. those requiring significant care.
🧒 Child / Pediatric
Patients under 17. Age-specific DRGs may apply. Pediatric conditions often have unique coding guidelines distinct from adult rules.
🧑 Adult
Patients 18 and older. The majority of inpatient cases. Standard DRG groupings apply based on diagnosis, procedure, and CC/MCC status.
♂ / ♀ Sex-Specific
Certain DRGs are sex-specific (e.g., obstetric, reproductive). Correct sex assignment is critical to avoid claim edits and denials.
Account Types
Concurrent vs. Discharge Coding
Discharge (All Account)
Coding is performed after the patient has been discharged. The complete medical record — including the discharge summary and all final reports — is available. This is the most common inpatient coding workflow and allows for the most accurate and complete code assignment.
Concurrent Coding
Coding is performed while the patient is still admitted. Coders review available documentation in real time to identify potential DRG opportunities, query physicians early, and support case management. The record is incomplete, so codes are preliminary and updated at discharge.
Record Review
Medical Records to Review — Part 1: Admission & Clinical Notes
01
Admission Order
The folder/order confirming inpatient admission status. Required to validate the encounter as a true inpatient admission for DRG billing.
02
ED Documentation
Review symptoms, conditions, and any procedures performed in the ED: laceration repair, intubation, PICC line, TPA, BiPAP. Also review MDM (Medical Decision Making) notes for complexity level.
03
H&P (History & Physical)
Includes HPI, PMH, ROS, PSH, Social History, GI/GE exam, Physical Exam, Home Medications, Allergies, Vital Signs, and Assessment/Plan.
04
Consultation & Progress Notes
Review Assessment/Plan sections and any bedside procedures documented by consulting or attending physicians throughout the stay.
Record Review
Medical Records to Review — Part 2: Reports & Ancillary
Operative & Anesthesia Reports
If a surgical procedure was performed, the operative report is essential for ICD-10-PCS coding. The anesthesia report confirms procedure type and duration.
Radiology Reports
X-ray, CT, MRI, Ultrasound, Cardiac Cath, LP, and Thrombectomy reports provide diagnostic findings and procedure confirmation critical for accurate coding.
Lab & Pathology Reports
Lab reports (including COVID test results) and pathology reports confirm diagnoses. Pathology is essential when malignancy or tissue diagnosis is involved.
Medication Summary
The medication list reveals conditions not always documented in notes — insulin use may indicate diabetes, anticoagulants may indicate DVT/AFib, etc.
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Coding Steps
How to Code an Inpatient Record
1
Review Full Record
Read the Discharge Summary first for the hospital course and final diagnoses, then review all supporting documentation.
2
Identify Principal Dx
Apply UHDDS guidelines to select the condition chiefly responsible for admission after study — not necessarily the admitting diagnosis.
3
Assign Secondary Dx & Procedures
Code all CCs, MCCs, and significant procedures (ICD-10-PCS). Query the physician if documentation is unclear or incomplete.
4
Verify DRG & Submit
Run through the DRG grouper, confirm discharge disposition, validate all codes, and submit the clean claim.
Summary
Inpatient Coding — Key Takeaways
DRG = Payment
Every inpatient case resolves to a DRG. Principal diagnosis, CCs/MCCs, procedures, age, sex, and disposition all drive the final grouping.
Review All 20 Records
From the Admission Order to the Discharge Summary — every document contributes to accurate, complete, and compliant code assignment.
Accurate inpatient coding starts with a thorough record review — the Discharge Summary tells the story, but every note, report, and record fills in the details that drive the DRG.