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N10

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ICD-10 CM - N10 - Acute tubulo-interstitial nephritis

Code Classification

  • Chapter: Chapter 14 - Diseases of the genitourinary system (N00-N99)
  • Block: Tubulo-interstitial nephritis (N10-N16)
  • Category: N10 - Acute tubulo-interstitial nephritis
  • Code: N10 - Acute tubulo-interstitial nephritis
  • Status: Billable/Specific ICD-10-CM code for reimbursement

Clinical Description

N10 represents acute inflammation of the kidney interstitium and tubules, often resulting in acute kidney injury. This condition is characterized by a rapid decline in renal function due to immune-mediated injury or direct toxicity to the renal tubules. N10 is distinct from chronic forms of the disease and often requires immediate medical intervention to prevent permanent damage.

Common Clinical Presentations

  • Fever and chills
  • Flank pain or tenderness
  • Hematuria (blood in urine)
  • Pyuria (white blood cells in urine, often sterile)
  • Elevated serum creatinine and BUN
  • Rash (common in drug-induced cases)
  • Eosinophilia (in allergic interstitial nephritis)

Common Etiologies

  • Drug-induced: Antibiotics (penicillins, cephalosporins, sulfonamides), NSAIDs, proton pump inhibitors (PPIs), diuretics
  • Infection-related: Bacterial, viral, or fungal infections spreading to the interstitium
  • Autoimmune: Systemic lupus erythematosus, Sjogren’s syndrome, sarcoidosis
  • Idiopathic: Cause unknown after workup

Code Hierarchy / Tree

N00-N99  Diseases of the genitourinary system
└─ N10-N16  Tubulo-interstitial nephritis
   └─ [[N10]]  Acute tubulo-interstitial nephritis ← THIS CODE
      ├─ (Includes) Acute pyelonephritis NOS
      └─ (Excludes1) Chronic tubulo-interstitial nephritis (N11.-)
   
   └─ N11  Chronic tubulo-interstitial nephritis
      ├─ N11.0  Nonobstructive reflux-associated chronic pyelonephritis
      ├─ N11.1  Chronic obstructive pyelonephritis
      ├─ N11.8  Other chronic tubulo-interstitial nephritis
      └─ N11.9  Chronic tubulo-interstitial nephritis, unspecified
   
   └─ N12  Tubulo-interstitial nephritis, not specified as acute or chronic
   └─ N13  Obstructive and reflux uropathy
   └─ N14  Drug- and heavy-metal-induced tubulo-interstitial and tubulointerstitial nephritis
   └─ N15  Other tubulo-interstitial kidney diseases
   └─ N16  Renal tubulo-interstitial disorders in diseases classified elsewhere

Coding Best Practice

Always distinguish between acute (N10), chronic (N11.-), and unspecified (N12) tubulo-interstitial nephritis. If the documentation states “acute interstitial nephritis” without further specification, N10 is the correct code. If the cause is known to be a drug, consider N14.1 (Other drug-induced tubulo-interstitial nephritis) if specified as acute, though N10 is often used for the general acute diagnosis with an additional code for the drug adverse effect.

Includes / Excludes Notes

Includes (Applicable To)

  • Acute interstitial nephritis
  • Acute pyelonephritis NOS (Not Otherwise Specified)
  • Acute tubulo-interstitial infection
  • Infective interstitial nephritis acute

Excludes1 (Never code together - mutually exclusive)

CodeDescriptionRationale
N11.-Chronic tubulo-interstitial nephritisAcute vs. Chronic duration
N12Tubulo-interstitial nephritis, not specified as acute or chronicSpecificity required (Acute)
N13.0Hydronephrosis with ureteral stricture, not elsewhere classifiedObstructive vs. Inflammatory
N13.6PyonephrosisDistinct pathological condition

Excludes2 (May code together if both conditions exist)

CodeDescriptionWhen to Use Both
N14.0Analgesic nephropathyIf chronic damage exists alongside acute episode
N14.1Other drug-induced tubulo-interstitial nephritisIf specific drug causality is documented
N17.9Acute kidney failure, unspecifiedIf AKI is present concurrently
B96.-Bacterial agents as the cause of diseases classified to other chaptersTo identify infectious organism

Chapter-Level Notes (N00-N99)

  • Chronic Kidney Disease (CKD): If the patient has underlying CKD, code the CKD first (e.g., N18.3-, N18.4) followed by N10 if acute-on-chronic kidney disease is present.
  • Drug Induced: If the nephritis is explicitly documented as drug-induced, an additional code from Chapter 19 (T36-T50) with fifth or sixth character 5 (adverse effect) should be assigned to identify the drug.
  • Organism: Use additional code (B95-B97) to identify the infectious agent if known (e.g., E. coli, Staphylococcus).

HCC Risk Adjustment Status

CMS-HCC Model V24 & V28

AttributeValue
HCC CategoryNone
Relative Factor (RAF)0.000
Model StatusNot an HCC

HCC Documentation Context

  • N10 is an acute condition and does not contribute to the Hierarchical Condition Category (HCC) risk adjustment score.
  • HCC models focus on chronic, long-term conditions (e.g., N18.3- Chronic Kidney Disease, Stage 3).
  • While N10 does not increase RAF, accurate coding is critical for risk adjustment because unresolved acute nephritis may progress to CKD (N18.-), which is an HCC.
  • Ensure documentation clearly distinguishes acute episodes from chronic baseline status to avoid inappropriate HCC capture or denial.

MS-DRG Assignment (Inpatient Facility Billing)

N10 may group to the following MS-DRGs (v43.0) depending on procedures performed, presence of CC/MCC, and principal diagnosis status:

MS-DRGDescriptionTypical ScenariosCC/MCC Impact
689Kidney and urinary tract infections with MCCSevere acute nephritis with sepsis or respiratory failureMajor Complication/Comorbidity present
690Kidney and urinary tract infections without MCCAcute nephritis managed medicallyNo MCC (CC may be present)
697Kidney and urinary tract signs and symptoms with MCCHematuria/AKI workup revealing nephritisMCC present
698Kidney and urinary tract signs and symptoms without MCCSymptom management onlyNo CC/MCC
682Renal failure with MCCIf Acute Kidney Injury (N17.9) is principalMCC present
683Renal failure with CCIf AKI is principalCC present
684Renal failure without CC/MCCIf AKI is principalNo CC/MCC

DRG Logic

  • If N10 is the principal diagnosis, DRGs 689 or 690 are most common.
  • If Acute Kidney Failure (N17.-) is the principal diagnosis with N10 as secondary, DRGs 682-684 are more likely.
  • Presence of sepsis (A41.9) often drives the MCC status for DRG 689.

wRVU and Assistant Payable Status

Diagnosis Code Limitation

N10 is an ICD-10-CM diagnosis code, NOT a CPT procedure code. Therefore:

  • wRVU (work Relative Value Unit): Not applicable. wRVUs are assigned to CPT/HCPCS procedure codes (e.g., 50200, 50945), not diagnosis codes.
  • Assistant Payable: Not applicable. Assistant-at-surgery indicators apply to CPT surgical procedure codes, not diagnosis codes.

To find wRVU/assistant payable data, reference the CPT procedure codes used to diagnose or treat the condition (e.g., kidney biopsy, cystoscopy, urinalysis).

Coding Examples

Example 1: Drug-Induced Acute Interstitial Nephritis

Clinical Scenario: Patient presents with AKI after starting omeprazole. Biopsy confirms acute interstitial nephritis. Provider documents “Acute tubulo-interstitial nephritis due to PPI.”

CodeDescriptionRationale
N10Acute tubulo-interstitial nephritisPrimary diagnosis for the acute inflammation
T39.8X5AAdverse effect of other drugs primarily affecting the gastrointestinal system, initial encounterIdentifies the causative agent (PPI)
N17.9Acute kidney failure, unspecifiedCaptures the functional impairment (AKI)

Sequencing

If the encounter is specifically for the adverse effect, the T-code may be sequenced first depending on admission reason. If admitted for the nephritis itself, N10 is often principal.

Example 2: Acute Pyelonephritis NOS

Clinical Scenario: Patient presents with fever, flank pain, and WBCs in urine. Culture pending. Provider documents “Acute pyelonephritis.”

CodeDescriptionRationale
N10Acute tubulo-interstitial nephritisIncludes acute pyelonephritis NOS per ICD-10 includes notes
B96.20Unspecified Escherichia coli [E. coli] as the cause of diseases classified to other chaptersAdd if organism is identified
R50.9Fever, unspecifiedSymptom code if fever is significant focus

Example 3: Acute on Chronic Kidney Disease

Clinical Scenario: Patient with known CKD Stage 3 presents with acute nephritis. Creatinine spikes from baseline.

CodeDescriptionRationale
N10Acute tubulo-interstitial nephritisAcute component
N18.3-Chronic kidney disease, stage 3 (moderate)Underlying chronic condition
N17.9Acute kidney failure, unspecifiedOptional if AKI criteria met, often implied by N10 + N18

CKD Sequencing

When acute kidney failure occurs with chronic kidney disease, code the acute condition first (or N17.-) followed by the CKD code (N18.-). Check specific coding guidelines for “Acute on Chronic” sequencing rules for the fiscal year.

Example 4: Resolution/Follow-up

Clinical Scenario: Patient returns 4 weeks post-discharge. Nephritis resolved. Creatinine back to baseline CKD level.

CodeDescriptionRationale
N18.30Chronic kidney disease, stage 3 (moderate)Active chronic condition remains
Avoid N10Do not report acute code if condition has resolved
Z09Encounter for follow-up examination after completed treatment for conditions other than malignant neoplasmReason for visit

Clinical Documentation Improvement (CDI) Tips

Query Triggers for Specificity

- Documentation states "Nephritis" without acute/chronic distinction → Query: "Is the nephritis acute, chronic, or unspecified?"
- Documentation states "Acute Kidney Injury" with "Interstitial Nephritis" → Query: "Is the AKI due to the nephritis? Should both be coded?"
- Medication list includes NSAIDs/PPIs/Antibiotics + Acute Nephritis → Query: "Is the nephritis drug-induced? If so, which agent?"
- History of CKD + New Acute Nephritis → Query: "Is this acute-on-chronic kidney disease? Please specify CKD stage."

Documentation Best Practices

  • Specify etiology (drug-induced, infectious, autoimmune) to support accurate coding (N14.1 vs N10).
  • Specify CKD Stage if chronic disease is present (N18.1 through N18.6).
  • Document resolution clearly to prevent inappropriate carryover of acute codes to future encounters.
  • Link symptoms (fever, flank pain) to the diagnosis in the assessment plan to support medical necessity.

More Specific Tubulo-Interstitial Codes

  • N11.0 - Nonobstructive reflux-associated chronic pyelonephritis
  • N11.1 - Chronic obstructive pyelonephritis
  • N11.8 - Other chronic tubulo-interstitial nephritis
  • N11.9 - Chronic tubulo-interstitial nephritis, unspecified
  • N12 - Tubulo-interstitial nephritis, not specified as acute or chronic
  • N14.0 - Analgesic nephropathy
  • N14.1 - Other drug-induced tubulo-interstitial nephritis
  • N14.2 - Tubulo-interstitial nephritis, not specified as acute or chronic, due to unspecified drug

Acute Kidney Failure Codes

  • N17.0 - Acute kidney failure with tubular necrosis
  • N17.1 - Acute kidney failure with acute cortical necrosis
  • N17.2 - Acute kidney failure with medullary necrosis
  • N17.8 - Other acute kidney failure
  • N17.9 - Acute kidney failure, unspecified

Chronic Kidney Disease Codes (HCC Relevant)

  • N18.1 - Chronic kidney disease, stage 1
  • N18.2 - Chronic kidney disease, stage 2 (mild)
  • N18.3- - Chronic kidney disease, stage 3 (moderate)
  • N18.4 - Chronic kidney disease, stage 4 (severe)
  • N18.5 - Chronic kidney disease, stage 5
  • N18.6 - End stage renal disease

Common Procedure Codes (CPT) for Nephritis Workup

  • 50200 - Biopsy of kidney, percutaneous
  • 50205 - Biopsy of kidney, open
  • 81000 - Urinalysis, automated
  • 81001 - Urinalysis, manual
  • 50945 - Cystourethroscopy, with ureteral catheterization
  • 36415 - Collection of venous blood by venipuncture (for Creatinine/BUN)

Coding Edits & Compliance Alerts

Common Denial Risks

  1. Acute vs. Chronic Confusion: Using N10 for patients with stable chronic nephritis will lead to denials or audits. Ensure documentation supports “acute” presentation (rapid onset, rapid decline in function).
  2. Drug Induced Specificity: If the provider documents “Drug-induced interstitial nephritis,” coding N10 alone may be insufficient. Consider N14.1 depending on coder guidance and tabular list instructions for the specific year.
  3. AKI Redundancy: Coding both N10 and N17.9 is generally acceptable if both conditions are treated/monitored, but some payers may bundle them. Verify NCCI edits.
  4. CKD Staging: If CKD is present, the stage must be documented. Unspecified CKD (N18.9) may trigger queries or lower DRG weights.

Quick Reference Summary

AttributeValue
CodeN10
DescriptionAcute tubulo-interstitial nephritis
BillableYes
EffectiveFY 2026 (10/1/2025)
HCC V24None
HCC V28None
MS-DRGs689, 690, 697, 698, 682, 683, 684
wRVUN/A (diagnosis code)
Assistant PayableN/A (diagnosis code)
Excludes1N11.- (Chronic forms)
Use WhenAcute inflammation of kidney interstitium/tubules documented

Revision History

  • 2026-03-12: Initial note creation; updated for FY 2026 ICD-10-CM, MS-DRG v43.0
  • 2025-10-01: N10 remained unchanged from prior year; no code revisions

Key Takeaway

N10 is the correct code for acute inflammation of the renal interstitium and tubules. It is critical to distinguish this from chronic forms (N11.-) and to identify any drug-induced etiology (N14.1) or underlying CKD (N18.-). While not an HCC itself, accurate coding prevents progression to uncoded CKD and ensures appropriate DRG assignment for inpatient stays involving acute kidney injury.

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