N39.0 — Urinary tract infection, site not specified

Clinical Definition

A urinary tract infection (UTI) is an infection involving any part of the urinary system, including the kidneys, ureters, bladder, and urethra. UTIs are among the most common bacterial infections in clinical practice, with Escherichia coli (E. coli) accounting for 75-95% of uncomplicated cases. Other causative organisms include Klebsiella pneumoniae, Proteus mirabilis, Enterococcus faecalis, and Staphylococcus saprophyticus. Patients typically present with dysuria, urinary frequency, urgency, suprapubic discomfort, and occasionally hematuria.

ICD-10-CM code N39.0 is assigned when a provider documents a urinary tract infection without specifying the anatomical site — that is, when the record does not distinguish between cystitis (bladder), pyelonephritis (kidney), or urethritis. This code is appropriate for the general diagnosis of "UTI" when no site-specific information is documented. N39.0 should not be used when documentation clearly identifies the infection site, as more specific codes exist for cystitis (N30.x), pyelonephritis (N10-N12), and urethritis (N34.x).

Per ICD-10-CM Official Guidelines, when the causative organism is identified by urine culture, an additional code from category B95-B97 must be assigned. For example, if E. coli is identified, report N39.0 for the UTI and B96.20 for unspecified E. coli as an additional code. The organism code is always sequenced as a secondary code, not as the principal or first-listed diagnosis. Omitting the organism code when culture results are available is a common coding deficiency.

When to Use N39.0

• ✓The provider documents 'urinary tract infection' or 'UTI' without specifying whether the infection involves the bladder, kidneys, urethra, or another anatomical site.
• ✓A patient presents with classic UTI symptoms (dysuria, frequency, urgency) and the clinician diagnoses a UTI based on clinical findings and/or positive urinalysis without further anatomic localization.
• ✓Urine culture confirms a urinary tract infection, but the provider's documentation does not differentiate between upper and lower tract involvement.
• ✓The patient is treated empirically for a UTI in an urgent care or emergency department setting where site-specific evaluation (e.g., imaging) was not performed and the documentation simply states 'UTI.'
• ✓Coding from a problem list, discharge summary, or referral letter that lists 'UTI' or 'urinary tract infection' without additional anatomic detail.
• ✓A recurrent urinary tract infection is documented without site specification — note that N39.0 may be used, though coders should also consider whether a history code (Z87.440) is more appropriate for resolved infections.

Common Coding Mistakes

Related & Differential Codes

Documentation Requirements

• 1Site of infection: document whether the UTI involves the bladder (cystitis), kidney (pyelonephritis), urethra (urethritis), or is unspecified — this directly determines code selection between N30.x, N10-N12, N34.x, or N39.0.
• 2Causative organism: record urine culture results with the identified pathogen (e.g., E. coli, Klebsiella, Proteus) and sensitivity pattern to support assignment of an additional B95-B97 organism code.
• 3Symptoms and clinical findings: document presenting symptoms such as dysuria, frequency, urgency, suprapubic pain, flank pain, fever, or costovertebral angle tenderness to support the clinical diagnosis and differentiate upper from lower tract infection.
• 4Urinalysis and culture results: include results such as pyuria (WBC count), nitrites, leukocyte esterase, colony count, and identified organisms with antibiotic sensitivities.
• 5Complicating factors: document the presence of any indwelling catheter (for CAUTI coding), pregnancy status (which redirects coding to O23.x), urinary obstruction, vesicoureteral reflux, or immunocompromised state.
• 6Recurrence history: if applicable, document whether this is a first episode, recurrent UTI, or chronic infection, and the number of episodes within the past 12 months.
• 7Treatment plan: document the prescribed antibiotic (name, dose, duration), any pending culture-directed changes, and follow-up instructions.
• 8Classification as complicated vs. uncomplicated: document any structural or functional abnormalities of the urinary tract, male sex, pregnancy, immunosuppression, or multidrug-resistant organisms that would classify the UTI as complicated.

Reimbursement & Billing Notes

ICD-10-CM code N39.0 is a valid, billable code accepted by Medicare, Medicaid, and commercial payers for reimbursement of services related to urinary tract infection evaluation and management. It is commonly used across outpatient, emergency department, urgent care, and inpatient settings. However, payers may request additional documentation when N39.0 is submitted without an accompanying organism code, particularly in inpatient settings where urine cultures are standard practice. Coders should ensure that when culture results are available, the appropriate B95-B97 code is appended to maximize coding accuracy and reduce the risk of claim queries.

For Medicare risk adjustment purposes, N39.0 does not map to a CMS-HCC category in the standard V28 risk adjustment model, so it does not directly impact RAF scores or capitated payments. Nevertheless, accurate UTI coding is important for quality reporting, hospital-acquired condition tracking (particularly CAUTI), and value-based purchasing programs. Under CMS hospital-acquired condition policies, catheter-associated UTIs may result in reduced reimbursement if not properly documented and coded with the appropriate T83.511x complication code. Facilities should ensure that CAUTI cases are correctly identified with both the device complication code and N39.0 to comply with present-on-admission indicator requirements and avoid preventable condition payment penalties.

Frequently Asked Questions