Osmolality, Stool

Test Code

Alias/See Also
Osmolality, Feces

Quest Code

CPT Codes

Preferred Specimen
1 mL stool collected in plastic leakproof container

Minimum Volume
0.2 mL

Formed stool will not be accepted. Freeze within 30 minutes.

Transport Temperature

Specimen Stability
Room temperature: unacceptable
Refrigerated: unacceptable
Frozen: not established

Freezing Point Depression

Setup Schedule
Monday-Friday Afternoon

Report Available
Next day

Clinical Significance
No age/sex specific ranges for this test. In patients with unexplained diarrhea, osmolalities < 290 mOsm/kg indicate contamination of stool with water or dilute urine or the presence of a gastrocolic fistula and ingestion of hypotonic fluid. Osmolalities > 290 mOsm/kg (up to 600 mOsm/kg) are common because of bacterial metabolism of fecal carbohydrate during storage of the stool sample. Even higher values can be observed with ingestion of large amounts of poorly absorbable carbohydrate or dietary fiber, with fecal contamination by concentrated urine, or with gastrocolic fistula and ingestion of hypertonic fluids.

Performing Laboratory
Quest Diagnostics Nichols Institute
Chantilly, VA

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.