Inpatient Billing Services
Inpatient coding operates under an entirely different reimbursement system than outpatient billing. Hospital inpatient stays are paid through DRGs (Diagnosis-Related Groups) under the Inpatient Prospective Payment System (IPPS), where a single payment covers the entire admission based on the principal diagnosis, secondary diagnoses, procedures performed, and patient demographics. The coder’s job isn’t to list every CPT code — it’s to capture the correct MS-DRG assignment by identifying the principal diagnosis, all relevant complications and comorbidities (CCs/MCCs), and the procedures that influence DRG grouping. Getting the DRG wrong by even one severity level can swing reimbursement by $5,000-$15,000 per admission.
The distinction between CCs (complications/comorbidities) and MCCs (major complications/comorbidities) is the single highest-impact coding decision in inpatient work. An admission for pneumonia coded with an MCC (such as respiratory failure or sepsis) groups to a significantly higher-paying DRG than the same admission without an MCC. But the MCC must be clinically supported in the documentation — physicians must document the condition, its clinical significance, and the treatment provided. Query programs that ask physicians to clarify documentation are the primary revenue recovery tool in inpatient coding.
Inpatient billing at a glance
Common inpatient procedures we bill daily.
Medical Admissions
Surgical DRGs
Critical Care & ICU
Inpatient billing challenges we solve every day.
Inpatient is one of the most complex specialties to bill. High-value procedures, strict documentation requirements, and frequent payer policy changes mean even experienced in-house billers miss revenue. For coding standards, see the CMS Inpatient Prospective Payment.
CC/MCC Capture and Physician Query Programs
The difference between a DRG with an MCC and without can be $5,000-$15,000 in payment. Physicians routinely under-document conditions that qualify as CCs or MCCs — documenting “elevated creatinine” instead of “acute kidney injury” (an MCC), or “confusion” instead of “acute encephalopathy” (an MCC). A compliant query program that asks physicians to clarify ambiguous documentation is the single most effective revenue recovery tool in inpatient coding. Evolution generates targeted, clinically specific queries — never leading questions — that capture the true severity of illness while maintaining audit defensibility.
Principal Diagnosis Selection
UHDDS guidelines require the principal diagnosis to be “the condition established after study to be chiefly responsible for occasioning the admission.” When a patient presents with chest pain and is found to have a STEMI, the principal diagnosis is the STEMI, not the chest pain — even though chest pain was the reason for the ED visit. Incorrect principal diagnosis selection groups the admission to the wrong DRG. In cases with multiple competing conditions (e.g., sepsis vs. pneumonia vs. respiratory failure), the sequencing rules are complex and the financial impact is significant. Evolution applies official coding guidelines to every admission to ensure principal diagnosis accuracy.
ICD-10-PCS Procedure Coding Complexity
Inpatient procedures are reported using ICD-10-PCS, a 7-character coding system that is fundamentally different from CPT. Each character position represents a specific attribute: body system, root operation, body part, approach, device, and qualifier. Selecting the wrong root operation (excision vs. resection vs. extraction) or wrong approach (open vs. percutaneous endoscopic) changes the DRG assignment. Spine surgery alone has hundreds of possible PCS combinations based on vertebral level, approach, and device. Evolution’s inpatient coders are trained specifically in PCS logic and validate every procedure code against the operative report.
Present on Admission (POA) and Hospital-Acquired Conditions
Every secondary diagnosis on an inpatient claim must carry a POA indicator — was this condition present when the patient arrived, or did it develop during the hospitalization? Conditions not present on admission that qualify as Hospital-Acquired Conditions (HACs) — pressure ulcers, catheter-associated UTIs, surgical site infections — cause the DRG to lose its CC/MCC status, reducing payment. Incorrectly marking a condition as “not POA” when it was actually present costs the hospital the CC/MCC bump. Evolution reviews admission documentation carefully to assign accurate POA indicators and protect against inappropriate HAC penalties.
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