Clinics and Departments

Laboratory Services

Lab Dept:

Urine/Stool

Test Name:

PH, STOOL

General Information

Lab Order Codes:

PHS

Synonyms:

Stool pH; Feces pH

CPT Codes:

83986 – pH, body fluid, except blood

Test Includes:

Determination of stool pH by Hydrion paper method.

Logistics

Lab Testing Sections:

Microbiology

Phone Numbers:

MIN Lab: 612-813-5866

STP Lab: 651-220-6555

Test Availability:

Daily, 24 hours

Turnaround Time:

4 hours

Special Instructions:

Requisition must state date/time of collection.

Specimen

Specimen Type:

Fresh random stool

Container:

Plastic leakproof container

Volume:

1 gram or 1 mL stool

Collection:

● Collect stool in a clean, dry bedpan or on a newspaper over the toilet. Transfer specimen to a plastic, leakproof container. Do not overfill or contaminate the outside of the container.
● Pediatric patients with severe diarrhea may use a U-bag collection system. Place the bag over the anal area in an attempt to retrieve the specimen before it soaks into the diaper. The diaper can also be reversed with the plastic side toward the skin to prevent the specimen from soaking into the diaper. Transfer specimen into a plastic, leakproof container.

Transport/Storage:

Specimen must be received in the laboratory within 1 hour of collection. Do not send specimen through the pneumatic tube.

Patient Preparation:

Barium procedures and laxatives should be avoided for 1 week prior to collection of the specimen.

Sample Rejection:

No diapers accepted. Improperly labeled specimen; specimen contaminated with urine and/or water; leaking container; insufficient volume; specimen containing interfering substances such as castor oil, bismuth, Metamucil®, barium, Vaseline®, or other cream contaminants. If an unacceptable specimen is received, the physician or nursing station will be notified and another specimen will be requested before the specimen is discarded.

Interpretive

Reference Range:

Diet dependent; normal, neutral to slightly alkaline or acid. Stool pH is usually slightly acidic at approximately pH 6. pH is increased with protein breakdown, decreased with carbohydrate or fat malabsorption. Breast-fed infants have slightly acid stools, bottle-fed infants, neutral or slightly alkaline. Acid stool is formed with fat malabsorption.

Normal diet

Neutral to slightly acidic
Approx. pH = 6.0

Breast feed infants

Slightly acid

Bottle fed infants

Neutral or slightly alkaline

Critical Values:

Stool pH <5.3 is diagnostic of carbohydrate intolerance; stool pH >6.8 is evidence of choleric enteropathy.

Limitations:

Limited value due to dependence on stool volume and transit time. Bacterial fermentation may give falsely acidic results if the specimen is not analyzed within 1 hour. The diagnosis of steatorrhea requires 72-hour specimen with diet of 75-100 g fat/24 hours.

Methodology:

Hydrion paper method

References:

Cook, JH, and M Pezzlo (1992). Specimen receipt and accessioning. Section 1. Aerobic bacteriology, 1.2.1-4. In HD Isenberg (ed) Clinical Microbiology Procedures Handbook. American Society for Microbiology, Washington DC

Miller, J Michael (1999) A Guide To Specimen Management in Clinical Microbiology, American Society for Microbiology, Washington DC

Miller, J Michael, and HT Holmes (1999) Specimen Collection, Transport, and Storage In PR Murray et al, (ed), Manual of Clinical Microbiology, 7th edition, American Society for Microbiology, Washington DC, pp 33-104



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