Complications and Comorbidities (CC/MCC) — Inpatient Profee Reference

Complications and Comorbidities (CC/MCC) — Inpatient Reference

Summary

CC (Complication or Comorbidity) and MCC (Major Complication or Comorbidity) designations are CMS-assigned severity levels applied to secondary diagnoses that affect MS-DRG assignment, reimbursement weight, and Case Mix Index (CMI). Only secondary diagnoses qualify. The presence of an MCC or CC can move a case into a higher-weighted DRG triplet, directly impacting hospital and physician reimbursement.

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Core Definitions

Term	Definition
CC	A secondary diagnosis that increases the complexity of the principal diagnosis or the resources required for treatment
MCC	A secondary diagnosis with the greatest potential impact on complexity and resource utilization — the highest severity tier
No CC/MCC	Base-level DRG — no qualifying secondary diagnosis present or applicable
PDx	Principal diagnosis — cannot serve as its own CC/MCC
SDx	Secondary diagnosis — the only diagnoses eligible for CC/MCC credit

Key Rule

The principal diagnosis is excluded from CC/MCC consideration. CC and MCC status is evaluated solely among secondary diagnoses. A condition that is the PDx may be a CC or MCC for a different PDx in a different encounter, but never for itself.

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How CC/MCC Drives DRG Assignment

Most MS-DRG logic is organized in triplets:

Base DRG + MCC  →  Higher-weighted DRG (e.g., DRG 870)
Base DRG + CC   →  Mid-weighted DRG    (e.g., DRG 871)
Base DRG w/o    →  Lower-weighted DRG  (e.g., DRG 872)

The grouper evaluates the entire secondary diagnosis list and selects the highest applicable severity level. Only one level applies per encounter — MCC presence supersedes all CCs. Multiple CCs do not stack.

DRG Triplet Example — Septicemia

• DRG 870 Septicemia or Severe Sepsis w/ MCC
• DRG 871 Septicemia or Severe Sepsis w/ CC or Severe Sepsis w/ MV 96+ hrs
• DRG 872 Septicemia or Severe Sepsis w/o CC/MCC

A patient admitted with sepsis and documented acute kidney injury (N17.9) would group to DRG 870 because AKI is an MCC.

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CC/MCC Designation Logic

Who Assigns CC/MCC Status?

CMS assigns CC/MCC status annually via the IPPS Final Rule. The lists are updated each federal fiscal year (October 1). Coders do not assign this status — the grouper does, based on the ICD-10-CM code submitted and the applicable rules below.

What Can Disqualify a CC/MCC?

1. POA (Present on Admission) Indicator

Indicator	Meaning	CC/MCC Impact
Y	Yes, present on admission	✅ Counts as CC/MCC if applicable
N	No, not present on admission	❌ May lose CC/MCC status if also a HAC
U	Unknown	❌ Treated as not POA for HAC purposes
W	Clinically undetermined	✅ Clinically ambiguous — still counts
1	Exempt from POA reporting	✅ Exempt codes always count

HAC + POA = Loss of CC/MCC Status

If a secondary diagnosis is both a Hospital-Acquired Condition (HAC) AND is flagged POA = N or U, it will not count as a CC or MCC for DRG assignment. Additionally, facilities may incur a payment penalty under the HAC Reduction Program.

2. CC Exclusion List

CMS publishes a CC Exclusion List that defines diagnosis pairs where the secondary diagnosis does not receive CC/MCC credit, because it is either an expected manifestation, an integral part of, or clinically redundant with the principal diagnosis.

CC Exclusion in Practice

If the PDx is pneumonia (J18.9) and a secondary diagnosis is respiratory failure (J96.00), the respiratory failure may be excluded from CC credit because it is an expected complication of pneumonia in that pairing — not a truly independent comorbidity increasing the complexity beyond the base DRG.

Coding Tip

CC exclusions are pair-specific. The same secondary diagnosis may be a valid CC or MCC when paired with a different PDx. Always let the grouper evaluate — do not assume exclusion without verification.

3. Code Already Included in PDx Coding

If the complication or comorbidity is already captured within the PDx code itself (e.g., a combination code), it cannot be separately listed as a CC/MCC.

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HAC Overview — Key Categories

HAC ≠ Query Opportunity for "More Coding"

HACs are not a reason to query for additional diagnoses. Documenting a HAC that is not POA removes CC/MCC status and triggers payment reduction. The goal is accurate documentation and POA assignment, not avoidance.

Selected HAC categories relevant to inpatient profee specialties:

HAC Category	Example Conditions
Pressure ulcers (stage 3+)	L89.X3, L89.X4, L89.X9
Falls and trauma	Fractures, burns, dislocations occurring post-admission
CAUTI	T83.511A, N39.0 — catheter-associated UTI
CLABSI	Central line-associated bloodstream infection
Surgical site infections	Specific SSI codes post-procedure
DVT/PE post-orthopedic	I26.XX, I82.4XX — certain joint replacement encounters
Air embolism	T79.0XXA
Transfusion incompatibility	T80.30XA
Hypoglycemia post-procedure	E11.641 in certain surgical contexts

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CC and MCC: Common Examples by Type

Common MCCs (Selected)

Condition	Code	Notes
Sepsis, unspecified	A41.9	Requires two-code construct with source (e.g., A41.51 for gram-neg)
Severe sepsis w/o organ failure	R65.20	Must accompany underlying sepsis code
Acute respiratory failure, unspecified	J96.00	Hypoxic vs hypercapnic specificity preferred
Acute kidney injury, unspecified	N17.9	Stage/specificity improves accuracy
ESRD	N18.6	Also qualifies for HCC — dual capture opportunity
Intracranial hemorrhage	I62.9	Various subtypes are MCCs
Aspiration pneumonia	J69.0	MCC — commonly seen in post-surgical/neuro patients
Malnutrition, severe	E43	Query opportunity when BMI low, albumin reduced, intake documented poor
Acute MI	I21.x	Various subtypes; important comorbidity across all specialties
Hepatic failure, unspecified	K72.90
Morbid obesity w/ alveolar hypoventilation	E66.01 + G47.36	Combination frequently seen in PMR

Common CCs (Selected)

Condition	Code	Notes
UTI, unspecified	N39.0	Also HAC risk if catheter-associated
Dysphagia, unspecified	R13.10	Common PMR and ENT CC; specify oropharyngeal vs esophageal
Malnutrition, moderate	E44.0	Lower tier than E43 but still a CC
CKD Stage 3	N18.3	Stage 4 = CC; Stage 5 = CC; ESRD = MCC
Obstructive sleep apnea	G47.33	Frequently documented, often missed as CC
Hypertensive CKD, Stage 1-4	I12.9	Combination code — captures both hypertension and CKD
Hematuria	R31.9	Relevant in urology; specificity matters
Pressure ulcer, Stage 2	L89.X12	Stage 3+ = MCC
Depression, unspecified	F32.A	Common PMR comorbidity
Urinary retention	R33.9	Frequent urology secondary diagnosis
Dehydration	E86.0	Common CC across all specialties
Ileus, paralytic	K56.0	Post-surgical
Pneumonia, unspecified	J18.9	May be PDx or SDx depending on encounter

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Specialty-Specific CC/MCC Considerations

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Physical Medicine & Rehabilitation (PMR)

PMR Context

Inpatient rehab admissions (IRF) use the IRF-PAI / CMG system, not MS-DRGs. However, patients admitted to an acute care hospital for PMR-related conditions (e.g., post-CVA, post-TBI, post-fracture, SCI) ARE subject to MS-DRG CC/MCC logic. The notes below apply to acute care inpatient stays with PMR-coded encounters.

High-Yield MCCs in PMR

Condition	Codes	Why It Matters
Severe TBI	S06.2X1A-S06.899S	Consciousness duration and LOC specificity required for MCC
Acute ischemic stroke	I63.x	Specify vessel and laterality
Sepsis (post-surgical)	A41.x + source code	Common complication in immobilized, post-op PMR patients
Respiratory failure	J96.0x	Dysphagia/aspiration risk in neuro patients
Aspiration pneumonia	J69.0	MCC — extremely common in neuro/dysphagia patients
Severe malnutrition	E43	Query when albumin <2.1, significant weight loss documented
Pressure ulcer, stage 3-4	L89.X3, L89.X4	POA critical — if acquired post-admit, HAC status applies
DVT	I82.4X1	Post-immobilization complication
PE	I26.09, I26.99	High-acuity complication

High-Yield CCs in PMR

Condition	Codes	Notes
Dysphagia	R13.10-R13.19	Specify oropharyngeal (R13.11) vs esophageal (R13.13); common in stroke, TBI
Urinary retention	R33.9	Neurogenic bladder patients; see also N31.9
Neurogenic bladder	N31.9	Specify subtype if documented
Pressure ulcer, stage 2	L89.X12	POA essential
OSA	G47.33	Very common comorbidity in PMR population
Depression	F32.A, F33.x	Post-stroke depression, TBI behavioral sequelae
Deconditioning / functional debility	Z74.09	Not a CC itself, but supports medical necessity documentation
Moderate malnutrition	E44.0	Step below severe; still CC
Hypertensive heart disease	I11.x	Common comorbidity
CKD (any stage)	N18.1-N18.6	Stage specificity affects CC vs MCC
Anemia, unspecified	D64.9	Common PMR CC

PMR Query Targets

• Malnutrition — albumin levels, weight loss %, dietitian documentation often present but physician linkage missing
• Dysphagia specificity — “oropharyngeal” vs “esophageal” changes code; query for type if not specified
• Aspiration pneumonia vs chemical pneumonitis — J69.0 (MCC) vs J68.0 — distinguish carefully; requires physician documentation
• Pressure ulcer POA — confirm with nursing admission assessment; stage at admission vs on discharge

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Urology

Urology Context

Urology inpatient encounters frequently involve post-procedural complications, obstructive uropathy, urologic malignancies, and complex renal conditions. CC/MCC capture is especially important in oncologic admissions, sepsis with genitourinary source, and AKI encounters.

High-Yield MCCs in Urology

Condition	Codes	Notes
Sepsis — urologic source	A41.51 (gram-neg) / A41.9	Document as sepsis due to [organism/source] — “urosepsis” alone is NOT a valid sepsis code per Coding Clinic
Acute kidney injury (AKI)	N17.9, N17.0, N17.1, N17.2	Specify prerenal (N17.0), acute tubular necrosis (N17.0 with detail), or cortical necrosis; AKI = MCC
ESRD	N18.6	Also an HCC — dual capture
Hemorrhagic shock	R57.1	Post-surgical major hemorrhage
Respiratory failure	J96.0x	Complication of complex surgical cases
Bilateral ureteral obstruction w/ AKI	N13.x + N17.x	Obstructive nephropathy driving AKI

High-Yield CCs in Urology

Condition	Codes	Notes
UTI, unspecified	N39.0	Also CAUTI risk; specify organism if documented
Urinary retention	R33.9	Distinguish acute (R33.9) vs chronic (R33.8)
Hematuria	R31.0 (gross) / R31.1 (microscopic) / R31.9	Gross hematuria may be PDx or CC depending on encounter
CKD, Stage 3	N18.30-N18.32	Substage specificity added in recent updates
CKD, Stage 4	N18.4	CC
CKD, Stage 5	N18.5	CC (ESRD = MCC)
Hypertensive CKD	I12.9, I12.10, I12.11	Combination code; captures both conditions
Diabetes w/ CKD	E11.65	Combination code — captures DM + CKD in one code
Post-procedural hemorrhage	N99.820, N99.821	Genitourinary organ post-procedure; POA = N typically
Urinary fistula	N32.1, N32.2	Post-surgical
Hydronephrosis	N13.30	With or without obstruction specificity
Vesicoureteral reflux	N13.70	Specify with/without reflux nephropathy

Urosepsis — Critical Coding Note

Per Coding Clinic 2Q 2012 and subsequent guidance: “Urosepsis” as a standalone term does not default to sepsis. It may refer to a urinary tract infection without systemic involvement. If the physician documents “urosepsis,” a query is required to clarify whether the patient meets sepsis criteria (sepsis syndrome, SIRS due to infectious process). If confirmed, code sepsis (A41.x) with urinary tract infection (N39.0) or applicable genitourinary source.

Failure to query results in either under-coding (missing MCC) or over-coding (assigning sepsis without documentation). Both are compliance risks.

Urology Query Targets

• AKI in obstructive uropathy — document relationship (obstructive vs intrinsic vs prerenal)
• Sepsis vs SIRS vs UTI — most high-value query in urology inpatient
• CKD staging — if GFR is in chart but stage not explicitly documented, query
• Organism specificity in UTI — improves code specificity, supports CAUTI exclusion
• Post-procedural vs pre-existing — distinguish complication (post-procedural hemorrhage) from pre-existing condition to guide POA

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Otolaryngology (ENT)

ENT Context

Inpatient ENT encounters include major head and neck oncologic surgery, deep space neck infections, airway management, and complex sinus/skull base cases. Malnutrition, airway complications, and post-operative hemorrhage are the most clinically significant CC/MCC opportunities. Tracheostomy-dependent patients may also qualify for special DRG mapping (LTCH-type groupings when applicable).

High-Yield MCCs in ENT

Condition	Codes	Notes
Aspiration pneumonia	J69.0	Common post-op, post-laryngectomy, or dysphagia-related; MCC
Respiratory failure	J96.0x	Airway-related; post-operative ENT risk
Sepsis (deep neck infection)	A41.x	Ludwig’s angina, parapharyngeal abscess progression
Severe malnutrition	E43	Critical in head/neck cancer — cachexia, pre-op nutritional decline
Major post-op hemorrhage	Post-procedural hemorrhage codes	Tonsillectomy hemorrhage, vessel erosion in radical neck

High-Yield CCs in ENT

Condition	Codes	Notes
Dysphagia	R13.11 (oropharyngeal) / R13.13 (esophageal)	Extremely common post-laryngectomy, tongue base resection, or pharyngeal surgery
Malnutrition, moderate	E44.0	Pre- or post-surgical; tube feeding dependence supports
Aspiration (without pneumonia)	Y93.89 (activity), R04.2 (hemoptysis), or clinical documentation	Distinguish from frank aspiration pneumonia
OSA	G47.33	Extremely common in ENT population; frequently documented
Post-tonsillectomy hemorrhage	J35.01	PDx if presenting problem; may be SDx in revision cases
Wound dehiscence (post-surgical)	T81.31XA, T81.32XA	Post-op complication; POA = N
Dehydration	E86.0	Common post-op ENT
Anemia	D64.9, D62	Post-surgical acute blood loss anemia (D62 = CC)
Tracheostomy complication	J95.00-J95.09	Obstruction, hemorrhage, mechanical
Laryngeal stenosis	J38.6	Post-surgical or post-intubation

ENT Query Targets

• Malnutrition in head/neck cancer — one of the highest-yield queries in ENT inpatient; dietitian documentation + albumin/prealbumin often supports but physician must make diagnosis
• Aspiration vs aspiration pneumonia — radiographic findings + clinical documentation needed to distinguish; J69.0 = MCC vs no CC for aspiration alone
• OSA with tracheostomy — OSA documented in H&P? If trach placed and prior OSA documented, code both
• Severity of dysphagia — oropharyngeal vs esophageal affects code; query if unclear
• Post-op hemorrhage POA — bleeding that develops post-operatively = N; correct POA assignment critical

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Ophthalmology

Ophthalmology Context

True inpatient ophthalmology encounters are uncommon (most ophthalmic procedures are outpatient). Inpatient ophthalmology coding typically arises in the context of: (1) endophthalmitis or severe ocular infection, (2) orbital complications of sinusitis or trauma, (3) patients with systemic comorbidities (diabetes, autoimmune disease) with acute ophthalmic manifestations requiring admission, or (4) post-procedural complications. CC/MCC capture in ophthalmic inpatient encounters is largely driven by systemic comorbidities, not the ophthalmic diagnoses themselves.

Ophthalmic Conditions That May Carry CC/MCC Status (as secondary diagnoses)

Condition	Code	Status	Notes
Endophthalmitis, panophthalmitis	H44.001-H44.009	May be MCC	Serious infection; bilateral or uncontrolled = significant resource use
Orbital cellulitis	H05.011-H05.019	CC	Frequently secondary to sinus disease
Acute angle-closure glaucoma	H40.211-H40.219	CC	Requires IOP documentation; may be bilateral
Vitreous hemorrhage	H43.10-H43.13	CC	Context-dependent
Retinal detachment, total	H33.051-H33.059	CC
Blindness, both eyes	H54.0x	CC	Functional status implication

Important Ophthalmology CC/MCC Reality

Most individual ophthalmic ICD-10-CM codes do not carry CC or MCC designation in the MS-DRG grouper. The CC/MCC impact in ophthalmic inpatient encounters almost always comes from systemic comorbidities listed as secondary diagnoses.

High-Yield Systemic CCs/MCCs in Ophthalmic Admissions

Condition	Code	Status	Notes
Diabetes w/ ophthalmic complications	E11.311-E11.359	CC varies	Combination codes; proliferative DR w/ macular edema = higher specificity
Severe sepsis	R65.20 + A41.x	MCC	Endophthalmitis with systemic spread
Acute kidney injury	N17.9	MCC	Post-IV contrast administration; post-surgical
Hypertensive retinopathy	H35.031-H35.039	CC context	Captured within hypertension + retinopathy combination
Hypertensive urgency/emergency	I16.0, I16.1	CC/MCC	Acute ocular hypertensive crisis
Autoimmune uveitis (systemic)	H30.101-H30.109	CC context	Underlying systemic disease (sarcoid, HLA-B27) may carry CC

Ophthalmology Query Targets

• Diabetic retinopathy specificity — proliferative vs nonproliferative, with/without macular edema; more specific combination codes improve DRG and HCC capture
• Laterality in all codes — required for accuracy; bilateral codes exist for most ophthalmic conditions
• Systemic source of orbital/ocular infection — document organism when culture available
• Functional impact — if visual acuity is severely affected, low vision or blindness codes may apply and affect complexity

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Physician Query Opportunities — CC/MCC

When to Query

Query when clinical indicators in the record suggest a CC or MCC condition exists but the physician has not explicitly documented it, or has documented it ambiguously. The query must be compliant — non-leading, open-ended, based on clinical indicators.

Universal Query Triggers

Clinical Finding	Potential CC/MCC	Query Direction
Elevated creatinine (1.5-2.0+), oliguria	AKI N17.9 (MCC)	“The creatinine trended from X to Y. Does this represent acute kidney injury?”
Albumin <2.1, weight loss >10%, poor PO intake	Severe malnutrition E43 (MCC)	“The dietitian documented [finding]. Is malnutrition present, and if so, what is the severity?”
Fever, elevated WBC, tachycardia + source	Sepsis A41.x (MCC)	“The patient has suspected infection with [SIRS criteria]. Does this meet criteria for sepsis?”
Low O2 sat, supplemental O2 required	Respiratory failure J96.0x (MCC)	“What is your clinical assessment of the patient’s respiratory status?”
Documented aspiration event + infiltrate	Aspiration pneumonia J69.0 (MCC)	“The patient had a witnessed aspiration event. Is aspiration pneumonia present?”
PEG tube, poor PO intake, documented wt loss	Malnutrition + dysphagia	Two separate query opportunities
GFR in chart, no CKD stage documented	CKD staging (N18.x) (CC or MCC)	“The GFR is documented as [X]. What stage of CKD does this represent, if any?”

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CMI (Case Mix Index) and CC/MCC

CMI Connection

CMI is the average DRG relative weight for a hospital or physician group’s inpatient discharges. It is a proxy for case complexity and drives reimbursement benchmarks. CC/MCC capture rate is a direct driver of CMI. Improved documentation and coding accuracy of CCs and MCCs raises CMI — appropriately.

• CC capture rate = % of discharges with at least one CC or MCC
• MCC rate = % with at least one MCC
• Targets vary by specialty and payer mix; typically benchmarked against national IPPS norms
• Under-coded CCs/MCCs = lost reimbursement and potentially inaccurate quality metrics (sicker patients appear healthier on paper)

Compliance Note

CC/MCC capture must be based on documented, clinically supported conditions. Query for underdocumented conditions is appropriate; adding codes without documentation is upcoding and a compliance violation. All CC/MCC designations must be supported by physician documentation in the medical record.

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CC/MCC Coding Quick Reference

For every inpatient encounter, ask:
1. What are all the secondary diagnoses?
2. Does each SDx have a CC or MCC designation in the grouper?
3. Is each SDx POA = Y? (Or W/1?)
4. Is any SDx also a HAC? (If POA = N/U → loses CC/MCC status)
5. Are any SDx pairs on the CC Exclusion List for the PDx?
6. What is the highest applicable severity level? (MCC > CC > none)
7. Is there documentation supporting a higher-severity SDx not yet captured?
   → Physician query opportunity?

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Related Notes

• MS-DRG System Overview
• POA Indicators — Inpatient Reference
• HAC Reduction Program
• Physician Query — Compliance and Templates
• Sepsis Coding — Inpatient Reference
• Malnutrition Coding — Inpatient Reference
• Acute Kidney Injury — ICD-10 Reference
• N17.9 — Acute kidney injury, unspecified
• A41.9 — Sepsis, unspecified organism
• E43 — Unspecified severe protein-calorie malnutrition
• J69.0 — Pneumonitis due to solids and liquids (aspiration)
• J96.00 — Acute respiratory failure, unspecified
• N18.6 — End stage renal disease

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Citations and Sources

1. CMS. MS-DRG Definitions Manual, Version 41.0. FY2024 IPPS Final Rule. ¹
2. AHA Coding Clinic for ICD-10-CM/PCS. 2Q 2012: Urosepsis. ²
3. CMS. Hospital-Acquired Conditions (HAC) Reduction Program. CMS.gov. ³
4. CMS. Present on Admission (POA) Indicator Reporting. MLN Matters. ⁴
5. AAPC. Certified Inpatient Coder (CIC) Exam Content — DRG Grouping and CC/MCC Logic. ⁵
6. OptumInsight. ICD-10-CM Expert for Hospitals. Current edition. ⁶