What N27 covers · when clinicians use it
ICD-10 code N27 identifies Small kidney of unknown cause in the U.S. ICD-10-CM clinical and billing record set. It sits within the Genitourinary System chapter (N00–N99), the section that groups related diagnoses so providers, payers, and public-health agencies report them consistently. Clinicians and medical coders apply N27 when an encounter's findings match the Small kidney of unknown cause description, attaching it to the patient record so downstream insurance claims, payer audits, quality reporting, and epidemiological surveillance all reference the same standardized diagnosis. The ICD-10-CM is maintained by the Centers for Medicare & Medicaid Services and the CDC's National Center for Health Statistics, with an updated official code set released each U.S. fiscal year — always verify N27 against the current CMS/CDC release and your payer's documentation guidance before final use. This page summarizes documentation context for N27 and is a coding reference, not clinical, diagnostic, or billing advice.
N27 refers to Small kidney of unknown cause, a group of kidney disorders characterized by impaired tubular function, structural abnormalities like contraction or small size, and other non-specific renal pathologies impacting kidney health and urine formation.
Symptoms
- Polyuria and polydipsia – Seen in tubular disorders (N25)
- Hypertension – Common with contracted or small kidneys (N26, N27)
- Proteinuria and hematuria – Indicative of general kidney damage
- Progressive renal insufficiency – Across all disorders
- Electrolyte imbalances – Due to tubular dysfunction
Diagnosis
Diagnosis of Small kidney of unknown cause includes kidney function tests (eGFR, creatinine), imaging (renal ultrasound, CT scan), urinalysis, electrolyte panels, and sometimes renal biopsy to investigate underlying structural or tubular abnormalities.
ICD10 Code Usage
ICD10 code N27 is used by nephrologists, urologists, and internists to document a range of renal abnormalities, facilitate further diagnostic evaluations, plan management strategies, and monitor disease progression or complications.
Related Codes
- N25 – Disorders resulting from impaired renal tubular function
- N26 – Unspecified contracted kidney
- N28 – Other disorders of kidney and ureter, not elsewhere classified
- N29 – Other disorders of kidney and ureter in diseases classified elsewhere
FAQs
Q1: What is ICD10 code N27?
A: It refers to Small kidney of unknown cause, encompassing disorders affecting renal tubular function, kidney size, and non-specific renal abnormalities.
Q2: What causes impaired renal tubular function (N25)?
A: Conditions like Fanconi syndrome, tubulointerstitial nephritis, genetic mutations, and nephrotoxin exposure can impair tubular function.
Q3: What is a contracted kidney (N26)?
A: It refers to a shrunken kidney often resulting from chronic scarring due to infections, reflux nephropathy, or vascular diseases.
Q4: How is a small kidney of unknown cause (N27) managed?
A: Management focuses on monitoring kidney function, managing blood pressure, and preventing progression of kidney disease when possible.
Q5: What are examples of N28 and N29?
A: N28 includes cysts, infarctions, or fibrosis of the kidney not classified elsewhere; N29 refers to renal complications occurring secondary to other systemic diseases.
Conclusion
ICD10 code N27 ensures comprehensive classification and management of Small kidney of unknown cause, supporting early intervention strategies that aim to preserve kidney function and prevent end-stage renal disease.