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HelpTest ID CRBF Creatinine, Body Fluid
Necessary Information
1. Date and time of collection are required.
2. Specimen source is required.
Specimen Required
Specimen Type: Body fluid
Preferred Source:
-Peritoneal fluid (peritoneal, abdominal, ascites, paracentesis)
-Pleural fluid (pleural, chest, thoracentesis)
-Drain fluid (drainage, JP drain)
-Peritoneal dialysate (dialysis fluid)
-Pericardial
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.
Forms
If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.
Secondary ID
606601Useful For
Identifying the presence of urine as a cause for accumulation of fluid in a body compartment
Measuring the ultrafiltration capacity of the peritoneal membrane in patients receiving peritoneal dialysis
Method Name
Enzymatic
Reporting Name
Creatinine, BFSpecimen Type
Body FluidSpecimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Body Fluid | Refrigerated (preferred) | 7 days |
| Frozen | 30 days | |
| Ambient | 24 hours |
Clinical Information
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 fluid:
Trauma as well as abdominal or pelvic surgery can lead to bladder perforation or formation of urinary fistula with excessive accumulation of peritoneal fluid or increased surgical drain output caused by intraperitoneal urinary leakage.(1,2)
Pleural fluid:
Urinoma describes the accumulation of urine in the perirenal and retroperitoneal spaces caused by genitourinary tract injury due to trauma or blockage of the urinary tract due to stones, strictures, tumors, benign prostate hypertrophy, etc.(3) Rarely, this fluid can translocate to the pleural cavity causing pleural effusion via movement of urine through the diaphragm or via lymphatic communication between retroperitoneal and pleural spaces caused by increased pressure due to urinoma. Urinothorax is the term used to describe an accumulation of urine in the pleural space. Patients often develop symptoms of dyspnea, chest pain, abdominal pain, and reduced diuresis.(4) The condition is reversed when treatment is directed to correct the primary cause (trauma in 75% and obstruction in 24% of cases). The pleural fluid to serum creatinine ratio is above 1 in 97.9% of cases (n=48; median ratio=2.9, range=0.95-16).
Peritoneal dialysis fluid:
Peritoneal dialysis (PD) is a type of ambulatory dialysis in which hyperosmotic fluid is infused into the patient's peritoneal cavity, with the peritoneum employed as the dialysis membrane promoting the diffusion of small molecules and free water from circulation.(5) The peritoneal equilibration test estimates the rate of small solute transport across the peritoneal membrane and the ultrafiltration capacity. Several analytes may be measured in order to perform this test. Creatinine is measured in PD fluid as well as in plasma or serum in samples taken 2 and/or 4 hours after the dialysate is instilled. The dialysate fluid to serum or plasma creatinine ratio is calculated with larger ratios (approaching 1.0) observed in patients exhibiting faster transport rates.
Reference Values
An interpretive report will be provided.
Cautions
The manufacturer lists the following interfering substances that affect creatinine results for serum testing and are expected to impact body fluid results in a similar manner, when present:
-Rifampicin, levodopa, and calcium dobesilate (eg, Dexium) cause artificially low creatinine results.
-As tested according to CLSI recommendation methyldopa causes artificially low creatinine results.
-Dicynone (Etamsylate) at therapeutic concentrations may lead to falsely low results.
-N-ethylglycine at therapeutic concentrations and DL-proline at concentrations of 1 mmol/L or greater (≥115 mg/L) give falsely high results.
-2-Phenyl-1,3-indandion (Phenindion) at therapeutic concentrations interferes with the assay.
-In patients receiving catecholamines (dopamine, dobutamine, epinephrine, and norepinephrine) falsely low results might be observed.
Results can be falsely decreased in patients with elevated levels of N-acetyl-p-benzoquinone imine (NAPQI, a metabolite of acetaminophen), N-acetylcysteine (NAC), and metamizole.
In very rare cases, gammopathy, in particular type IgM (Waldenstrom macroglobulinemia), may cause unreliable results.
Day(s) Performed
Monday through Sunday
Report Available
Same day/1 to 2 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
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
82570