In humans, after food has been processed into chyme in the stomach it enters the small intestine. In the small intestine, further enzymatic degradation of food occurs and then the broken down simple nutrients are absorbed. Undigested materials and bile salts then flow through a one-way sphincter called the ileocecal (IC) valve into the large intestine. In the large intestine, water and bile are reabsorbed while left-over materials are further compacted and simultaneously processed by symbiotic bacteria into the end product, feces.
Intestinal Flora
The small intestine is usually sparse in bacterial activity. In contrast, the large intestine normally houses several types of bacteria including Escherichia coli(E. coli), bifidus , and lactobacillus species. These bacteria thrive on the left-over materials, take up space, and make it an inhospitable environment for more pathological types of organisms.
Sometimes other bacteria or fungi do take over in the large intestine and then push past the IC valve into the small intestine (often called Small Bowel Bacterial Overgrowth Syndrome -or SBBOS). Causes of this may evolve from the use of antibiotics, diet choices, or physical inadequacies of the IC valve.
The Test
The indican test is a quick and efficient screening exam that assays the possibility of dysbiosis using a patient's urine. During occasions of overgrowth, bacteria intercept the amino acid tryptophan before it can be processed by the small intestine. They break it down into unique parts which are then absorbed by the small intestine, changed around in the liver, and then excreted in the urine.
Tryptophan
Tryptophan is a complex essential amino acid. Amino acids are the building blocks for proteins and the essential ones are not synthesized by the body and thus must be acquired from the diet. Besides being part of proteins, tryptophan is also the precursor for serotonin, melatonin, and the B -vitamin niacin.
Tryptophan has the usual amino and carboxyl ends but differs from other amino acids in that it has an indole group.
The Principle
Indoles are two-ring structures composed of a six member benzene ring fused to a nitrogen-containing, five member pyrrole ring. They have a flowery smell and turn a deep blue (indigo) when oxidized.
When quantities of bacteria are present in the small intestine, this indole ring is stripped from tryptophan. The indoles are then absorbed into the bloodstream where they are processed in the liver. The liver converts them into 3-hydroxyl-indole and then attaches glucuronic acid or potassium sulfate. They are then transported in the blood to the kidneys where they are excreted in the urine.
To perform the test, this urine is treated with Obermeyer reagent (ferric chloride dissolved in hydrochloric acid) and chloroform. The color of the solution is then observed. A clear solution indicates a negative test while an opaque or indigo color indicates a positive result.
Conditions Associated with Increased Indican:
- Small Bowel Bacterial Overgrowth (SBBO)
- Inflammatory Bowel Disease
- Celiac Disease
- Hypochlorhydia
- Gastric Ulcer
- Biliary and Intestinal Obstruction
- Jejunal Diverticulosis
- Scleroderma
- Diminished peristalsis
- Blue Diaper Syndrome & Hartnup's Disease (hereditary metabolism conditions)
- Increased protein or tryptophan consumption
These results may help a physician take steps in the right direction to address a patient's underlying condition.
Additional Resources
Indican Test
Pizzorno, J., Murray, M. Textbook of Natural Medicine. 2nd ed. New York, Churchill. 1999; p 245-246
Todd J. Clinical diagnosis and management by laboratory methods. Philadelphia, PA: WB Saunders. 1979: p 592–593
Greenberger N, Saegh S, Ruppert R. Urine indican excretion in malabsorption disorders. Gastroenterol 1968; 55: 204–211
Curzon G, Walsh J. Value of measuring urinary indican excretion. Gut 1966; 7: 711
Indoles, Part One, W.J. Houlihan (ed.), Wiley Interscience, New York, 1972.
Metabolic Conditions
Asatoor A, London D, Craske J et al. Indole production in Hartnup’s disease. Lancet 1963; i: 126–128
Drummond, K. N.; Michael, A. F.; Ulstrom, R. A.; Good, R. A. : The blue diaper syndrome: familial hypercalcemia with nephrocalcinosis and indicanuria. A new familial disease, with definition of the metabolic abnormalityAm. J. Med. 37: 928-948, 1964.
Overgrowth
Teo M, Chung S, Chitti L, Tran C, Kritas S, Butler R, Cummins A (2004). "Small bowel bacterial overgrowth is a common cause of chronic diarrhea"J Gastroenterol Hepatol 19 (8): 904–9.
Kirsch M (1990). "Bacterial overgrowth"Am J Gastroenterol85 (3): 231–7.
Tryptophan
Tryptophan biosynthesis and metabolism: biochemical and molecular genetics. Radwanski, E., Last, R. Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, New York 14853-1801, USA.
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