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Introduction
The essential amino acid tryptophan is converted to indole
by intestinal bacterial cleavage of the tryptophan side chain.
Following absorption, indole is converted to 3-hydroxy indole
(indoxyl or indican) in the liver, where it is then conjugated
with potassium sulfate or glucoronic acid. It is then transported
through the blood to the kidneys for excretion.
Clinical Application
As most of the endogenous indoles have a side chain which
prevents cleavage and are instead metabolized to skatole,
the production of indicans (indoxyl potassium sulfate and
indoxyl glucoronate) reflects bacterial activity in the small
and large intestines. The table below lists conditions in
which increased levels are found. Elevated levels are considered
as an indicator of intestinal toxemia and overgrowth of anaerobic
bacteria.
Conditions with Elevated Levels of Urinary Indican
- Inflammatory bowel disease
- Celiac disease
- Hypochlorhydria
- Achlorhydria
- Gastric ulcer
- Biliary and intestinal obstruction
- Jejunal diverticulosis
- Scleroderma
- Postgastrectomy
- Hartnup's disease
- Pancreatic insufficiency
- Diminished peristalsis
- Blue diaper syndrome
- Hypermotility of the small intestine
Procedure
Detection of indicans depends upon its decomposition to
indoxyl and subsequent oxidation to indigo blue. It is then
concentrated into a layer of chloroform for easier measurement.
Results
| Urine color |
0 (normal) |
| Light blue |
1+ (low positive) |
| Blue |
2+ (medium positive) |
| Violet |
3+ (high positive) |
| Jet black |
4+ (very high positive) |
Interpretation
A positive test may indicate one of the diseases listed
in table 1, hypochlorhydria, bacterial overgrowth in the small
and/or large intestine, maldigestion and/or malabsorption
of protein.
References
1. Todd J: Clinical Diagnosis and Management by Laboratory
Methods. WB Saunders, Phil, Pa 1979. pp 592-3
2. Greenberger N, Saegh S, and Ruppert R: Urine indican excretion
in malabsorption disorders. Gastroenterol 55:204-11, 1968
3. Curzon G and Walsh J: Value of measuring urinary indicant
excretion. Gut 7:711, 1966
4. Asatoor A, London D, Craske J, and Milne M: Indole production
in Hartnup's disease. Lancet i:126-8, 1963
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