What is ICD-10 code N99.511?

N99.511 is the ICD-10-CM diagnosis code for Cystostomy infection. An infection develops at or around the cystostomy site, the surgically created opening in the bladder used for urine drainage. This can involve the stoma itself or surrounding tissue. N99.511 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. N99.511 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. N99.511 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. N99.511 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for N99.511?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. N99.511 was a payment HCC under V24 (Complications of Specified Implanted Device or Graft) but the V28 recalibration removed it from the risk adjustment model. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting N99.511?

Document the organism identified if culture results are available Confirm active infection is present; do not code for prophylactic antibiotic use alone Because N99.511 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

2026 ICD-10-CM N99.511: Cystostomy infection

ICD-10-CM Code View

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Code lookupN99.511Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the genitourinary system (N00-N99) / Intraoperative and postprocedural complications and disorders of genitourinary system, not elsewhere classified (N99)

N99.511

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Cystostomy infection

An infection develops at or around the cystostomy site, the surgically created opening in the bladder used for urine drainage. This can involve the stoma itself or surrounding tissue.

Buddy Insight

Cystostomy infection represents a significant complication that can lead to urosepsis and systemic complications, requiring aggressive antibiotic therapy and possible device revision.

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

Mapped

HCC 176

Complications of Specified Im...

RAF 0.582

ACA/HHS

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ESRD/PACE

Mapped

HCC 176

Complications of Specified Im...

RAF 0.000

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

N99.5Complications of stoma of urinary tract

N99.51Complication of cystostomy

N99.511Cystostomy infection

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for N99.511 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for N99.511 in this effective period.

Related Child Codes

Official

N99.510Cystostomy hemorrhage

N99.512Cystostomy malfunction

N99.518Other cystostomy complication

Includes

Official

ICD-10-CM does not list Includes notes for N99.511 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for N99.511 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for N99.511 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for N99.511 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for N99.511 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Clinical evidence of infection at cystostomy site

Microbiological culture results and organism identification

Documentation of cystostomy procedure and timeline

Assessment of local vs systemic infection signs

MEAT Support

HCC Buddy guidance

Clinical evidence of infection at cystostomy site

Microbiological culture results and organism identification

Documentation of cystostomy procedure and timeline

Assessment of local vs systemic infection signs

Audit Caution

HCC Buddy guidance

Confusing bladder UTI with cystostomy site infection

Missing the device-related nature of the infection

Failing to document culture results and specific organisms

Not capturing the complication relationship to the procedure

Common Mistakes

HCC Buddy guidance

N99.510 — Cystostomy hemorrhage (bleeding vs infectious complication)

N30.90 — Cystitis, unspecified (bladder infection vs stoma infection)

T83.518A — Infection due to other urinary catheter (different device type)

N39.0 — Urinary tract infection, site not specified (general UTI vs device-related)

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is N99.511 an HCC code?

Yes. N99.511 maps to Complications of Specified Implanted Device or Graft under the V24 model but is not retained in V28.

Code: N99.511
Description: Cystostomy infection
HCC (V28): No CMS-HCC V28 mapping
RAF: —
Billable: Yes
Payment year: 2026

HCC Category Mapping

V24HCC 176, Complications of Specified Implanted Device or Graft

0.582

ESRDHCC 176, Complications of Specified Implanted Device or Graft

0.000

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work N99.511 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for N99.511

For N99.511 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed N99.511 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

N99.511 is the ICD-10-CM diagnosis code for cystostomy infection. An infection develops at or around the cystostomy site, the surgically created opening in the bladder used for urine drainage. This can involve the stoma itself or surrounding tissue. N99.511 sits in the ICD-10-CM chapter for diseases of the genitourinary system (n00-n99), within the section covering intraoperative and postprocedural complications and disorders of genitourinary system, not elsewhere classified (n99).

Under the older CMS-HCC V24 model, N99.511 maps to Complications of Specified Implanted Device or Graft (HCC 176) with a community, non-dual, aged base RAF weight of 0.582. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Document the organism identified if culture results are available. Because N99.511 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for N99.511 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Document the organism identified if culture results are available
•Confirm active infection is present; do not code for prophylactic antibiotic use alone

Clinical Significance

Cystostomy infection represents a significant complication that can lead to urosepsis and systemic complications, requiring aggressive antibiotic therapy and possible device revision. This complication substantially increases care complexity and morbidity risk in patients requiring urinary diversion.

Documentation Requirements

✓Clinical evidence of infection at cystostomy site
✓Microbiological culture results and organism identification
✓Documentation of cystostomy procedure and timeline
✓Assessment of local vs systemic infection signs
✓Antibiotic therapy selection and duration
✓Response to treatment and resolution documentation
✓Complications such as sepsis or device removal requirements
✓Preventive measures and care plan modifications

Commonly Confused Codes

•N99.510: Cystostomy hemorrhage (bleeding vs infectious complication)
•N30.90: Cystitis, unspecified (bladder infection vs stoma infection)
•T83.518A: Infection due to other urinary catheter (different device type)
•N39.0: Urinary tract infection, site not specified (general UTI vs device-related)
•L08.9: Local skin and soft tissue infection (non-device related)