Test Catalog

Test Id : UEBF

Urea Nitrogen, Body Fluid

Useful For
Suggests clinical disorders or settings where the test may be helpful

Identifying the presence of urine as a cause for accumulation of fluid in a body compartment


Assessing adequacy of peritoneal dialysis treatment protocols

Method Name
A short description of the method used to perform the test


NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Urea Nitrogen, BF

Lists additional common names for a test, as an aid in searching

Blood Urea Nitrogen, Body Fluids

BUN, Body Fluids

Nitrogen, Body Fluids

Specimen Type
Describes the specimen type validated for testing

Body Fluid

Necessary Information

1. Date and time of collection are required.

2. Specimen source is required.


Question ID Description Answers
FLD15 Fluid Type, Urea Nitrogen

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Preferred Source:

-Peritoneal fluid (peritoneal, abdominal, ascites, paracentesis)

-Pleural fluid (pleural, chest, thoracentesis)

-Drain fluid (drainage, JP drain)

-Peritoneal dialysate (dialysis fluid)


Acceptable Source: Write in source name with source location (if appropriate)

Collection Container/Tube: Sterile container

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Centrifuge to remove any cellular material and transfer into a plastic vial.

2. Indicate the specimen source and source location on label.


If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.5 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject
Cerebrospinal fluid, breast milk, saliva, nasal secretions, gastric secretions, bronchoalveolar lavage (BAL) or bronchial washings, colostomy/ostomy, feces, urine, , sputum, or vitreous fluid Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Body Fluid Refrigerated (preferred) 7 days
Frozen 30 days
Ambient 24 hours

Useful For
Suggests clinical disorders or settings where the test may be helpful

Identifying the presence of urine as a cause for accumulation of fluid in a body compartment


Assessing adequacy of peritoneal dialysis treatment protocols

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Byproducts of nitrogen metabolism are present in high concentration in urine compared to blood and serve as a surrogate marker for the identification of urine leakage into a body compartment. Concentrations of creatinine or urea nitrogen that exceed the concentration found in a concurrent sample of blood are suggestive of the presence of urine.(1)


Peritoneal, abdominal, pelvic drain fluids:

Disruption of the urinary tract with subsequent leakage of urine into body cavities may be considered as part of the differential diagnosis when body fluid effusions develop of unknown origin.(2) Metabolites such as creatinine or urea that are contained in urine at high concentrations are good candidates to measure in body fluids for this investigation. Elevated concentrations may elicit a more focused radiologic examination to identify possible bladder rupture or perforation or the development of urinary fistula, which are typically corrected by surgical intervention.


Peritoneal dialysis fluid:

Peritoneal dialysis (PD) is a type of dialysis in which hyperosmotic fluid is passed into the patient's peritoneal cavity for a prescribed dwell time, wherein the peritoneum is employed as the dialysis membrane. The dwell fluid containing waste molecules removed by dialysis is drained and replaced with fresh fluid and the process repeated. Measurements of urea, creatinine, glucose, or other electrolytes in serum, urine, and the peritoneal dialysate fluid, aid in the assessment of peritoneal membrane transport characteristics and serve as markers of dialysis adequacy. Adequacy of PD is important to monitor because patients who maintain a sufficient clearance over time have longer survival.(2) Peritoneal urea clearance volume of distribution or urea (Kt/V) is calculated to measure solute clearance from the daily peritoneal urea clearance (Kt), and the volume of distribution of urea (V). Adequacy and membrane transport characteristics are calculated by plugging in the appropriate laboratory parameters into software packages used by dialysis centers.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretive report will be provided.

Provides information to assist in interpretation of the test results

Peritoneal and drain fluid concentrations should be compared to serum or plasma. A fluid to serum ratio of greater than 1.0 suggests the specimen may be contaminated with urine.(1)


Peritoneal dialysate urea nitrogen concentrations can be used to calculate the adequacy of peritoneal dialysis by monitoring solute clearance over time.(3)


All other fluids: Results should be interpreted in conjunction with serum urea nitrogen and other clinical findings.

Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

In very rare cases, gammopathy, in particular type IgM (Waldenstrom macroglobulinemia), may cause unreliable results.


Ammonium ions may cause erroneously elevated results.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Manahan KJ, Fanning J: Peritoneal fluid urea nitrogen and creatinine reference values. Obstet Gynecol. 1999 May;93(5 Pt 1):780-782. doi: 10.1016/s0029-7844(98)00516-x

2. Block DR, Florkowski CM: Body fluids. In: Rafai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier;2018:chap 43

3. Canada-USA (CANUSA) Peritoneal Dialysis Study Group. Adequacy of dialysis and nutrition in continuous peritoneal dialysis: association with clinical outcomes. J Am Soc Nephrol. 1996;7:198-207

Method Description
Describes how the test is performed and provides a method-specific reference

This is a kinetic ultraviolet assay where urease cleaves urea to form ammonia and carbon dioxide. The ammonia formed then reacts with alpha-ketoglutarate and NADH in the presence of urease/glutamate dehydrogenase (GLDH) to yield glutamate and NAD. The decrease in absorbance, due to the consumption of NADH, is measured kinetically and is proportional to the amount of urea in the sample.(Package insert: Roche Urea/BUN reagent. Roche Diagnostic Corp; V7.0 07/2019)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Sunday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

Same day/1 to 2 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

1 week

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
UEBF Urea Nitrogen, BF 3093-2
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
UE_BF Urea Nitrogen, BF 3093-2
FLD15 Fluid Type, Urea Nitrogen 14725-6

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports