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Test ID CL_F Chloride, Feces


Ordering Guidance


This test is only clinically valid if performed on watery specimens. In the event a formed fecal specimen is submitted, the test will not be performed.



Specimen Required


Patient Preparation: No barium, laxatives, or enemas may be used for 96 hours prior to start of, or during, collection.

Supplies: Stool containers - 24, 48, 72 Hour Kit (T291)

Container/Tube: Stool container

Specimen Volume: 10 g

Collection Instructions: Collect a very liquid stool specimen.


Useful For

Workup of cases of chronic diarrhea

 

Evaluation of suspected chloridorrhea 

Method Name

Indirect Ion-Selective Electrode (ISE) Potentiometry

Reporting Name

Chloride, F

Specimen Type

Fecal

Specimen Minimum Volume

5 g

Specimen Stability Information

Specimen Type Temperature Time Special Container
Fecal Frozen (preferred) 14 days
  Refrigerated  7 days
  Ambient  48 hours

Clinical Information

The concentration of electrolytes in fecal water and their rate of excretion are dependent upon 3 factors:

-Normal daily dietary intake of electrolytes

-Passive transport from serum and other vascular spaces to equilibrate fecal osmotic pressure with vascular osmotic pressure

-Electrolyte transport into fecal water due to exogenous substances and rare toxins (eg, cholera toxin)

 

Fecal osmolality is normally in equilibrium with vascular osmolality, and sodium is the major effector of this equilibrium.(1) Fecal osmolality is normally 2 x (sodium + potassium) unless there are exogenous factors inducing a change in composition, such as the presence of other osmotic agents (magnesium sulfate, saccharides) or drugs inducing secretions, such as phenolphthalein or bisacodyl.

 

Chronic diarrhea with elevations in fecal chloride concentrations are caused by congenital chloridorrhea. This is a rare condition associated with a genetic defect in a protein responsible for transport of chloride ions across the mucosal membranes in the lower intestinal tract in exchange for bicarbonate ions. It plays an essential part in intestinal chloride absorption, therefore variants in this gene have been associated with congenital chloride diarrhea.(2.

 

Acquired chloridorrhea is a rare condition that has been described as causing profuse, chloride-rich diarrhea and a surprising contraction metabolic alkalosis rather than metabolic acidosis often associated with typical diarrhea. Contributors to acquired chloridorrhea include chronic intestinal inflammation and reduction of chloride/bicarbonate transporter expression in genetically susceptible persons post-bowel resection and ostomy placement. Acquired chloridorrhea is rare but may be an under-recognized condition in post-bowel resection patients.(3)

Reference Values

An interpretive report will be provided

Interpretation

Fecal chloride may be low (<20 mmol/L) in sodium sulfate-induced diarrhea.(4)

 

Markedly elevated fecal chloride concentration in infants (>60 mmol/L) and adults (>100 mmol/L) is associated with congenital and secondary chloridorrhea.(5)

Clinical Reference

1. Steffer KJ, Santa Ana CA, Cole JA, Fordtran JS: The practical value of comprehensive stool analysis in detecting the cause of idiopathic chronic diarrhea. Gastroenterol Clin North Am 2012;41:539-560

2. Makela S, Kere J, Holmberg C, Hoglund P: SLC26A3 mutations in congenital chloride diarrhea. Hum Mutat. 2002 Dec;20(6):425-438. doi: 10.1002/humu.10139/

3. Ali OM, Shealy C, Saklayen M: Acute pre-renal failure: acquired chloride diarrhea after bowel resection. Clin Kidney J. 2012;5(4):356-358. doi: 10.1093/ckj/sfs082

4. Eherer AJ, Fordtran JS: Fecal osmotic gap and pH in experimental diarrhea of various causes. Gastroenterology. 1992;103:545-551

5. Casprary WF: Diarrhea associated with carbohydrate malabsorption. Clin Gastroenterol. 1986;15:631-655

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

82438

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CL_F Chloride, F 15158-9

 

Result ID Test Result Name Result LOINC Value
CL_F Chloride, F 15158-9

Day(s) Performed

Monday, Thursday

Report Available

1 to 3 days