The fermentation of carbohydrates for intestinal bacteria produces water, acids and gasses, among which carbon dioxide (CO2), hydrogen (H2) and methane (CH4); in particular methane and hydrogen are produced exclusively by bacteria and excretion of these gasses in the human organism following the administration of a substrate indicates that it has been exposed to intestinal micro flora. This is the principle on which the hydrogen Breath Test is based. In particular, after the administration of the opportune substrate the concentration is measured, expressed in parts per million (ppm) of H2 in the breath of the patient via gas chromatography. The main parameters evaluated are: base values nil by mouth (normally less than 12 ppm), the absolute value of the maximum peak, the Delta value (i.e. the relative value of the peak in relation to the base value), the peak latency time (time passed between the start of the test and the appearance of the maximum peak). Normally the small intestine possesses a very scarse level of bacterial flora, therefore it is not able to ferment some sugars. In certain conditions though (mal-absorption after intestinal surgery, nil by mouth reflux, stagnation over phlogistic stenosis, scarring or neoplastic, IBD, IBS) it has an increase of bacterial flora in some tracts of the small intestine able to ferment the carbohydrates of the diet provoking diverse intestinal upsets. The bacterial overgrowth in the small intestine is also manifested in a not truly pathological condition, represented by the chronic administration of powerful gastric anti-secretion medicines such as Omeprazolo; in this case the bacterial contamination is associated neither with mal-absorption of fats nor that of carbohydrates. The test used to diagnose this pathology is the glucose Breath Test. Glucose is normally absorbed by the small intestine, where if bacteria are present, there is a fermentation of glucose with the production of hydrogen (H2) at small intestine level; and consequently an increase in H2 excretion, which can give us, indirectly, a sign of mal-absorption.
Definition of SIBO (small intestinal bacterial overgrowth)
Historically the definition of SIBO was based on the bacterial hyper-proliferation in a context of anatomical anomalies of the intestine, of genetic or postoperative character (in particular in patients affected by overgrowth syndrome: abnormal development of bacteria in the small intestine). It is considered diagnostic criteria when the bacterial count is above 1×105 cfu/ml. However in the last thirty years there has been a growing suspicion that such bacterial hyper-proliferation could be present in many other intestinal disorders; in some of these the bacterial count is higher than in healthy subjects, but lower than 1×105 cfu/ml. This has lead to the conclusion that the classic criteria is better indicated for the diagnosis of overgrowth syndrome rather than of SIBO. The diagnostic criteria have therefore been expanded and today foresee simply that in the nil by mouth breath there is a coliform bacterial presence higher than the concentration normally present in this intestinal tract (i.e. higher than 1×103 cfu/ml).
SIBO manifests itself usually with specific symptoms such as swelling, flatulence, abdominal pain, and diarrhoea. The majority of SIBO sufferers do not manifest clinical signs of mal-absorption such as weight loss, steatorrhoea, malnutrition, arthralgia (joint pain); these are manifested mainly in patients in which SIBO is associated with Billroth II and only in extreme cases (mainly in patients with small-bowel bypass or short intestine syndrome) is a vitamin and mineral deficit manifested (lipo-soluble vitamins A and D, vitamin B12, iron). As SIBO can depend on diverse local or systemic disorders, the symptomatology may vary based on the underlying problem. It is not clear if the gravity of the symptoms is proportional to the quantity of bacteria present in the small intestine. Recent studies show that SIBO is commonly associated with irritable bowel syndrome and that the bacterial hyper-proliferation can contribute to the pathogenesis of this syndrome.
The test can be used on patients that report gastro-intestinal upsets with flatulence, trapped air, diarrhoea, swelling and abdominal cramps.
The test consists of the collection of samples of breathed air, both before and after ingestion of a specific sugar dissolved in water (GLUCOSE), in a plastic bag at regular intervals. The exam lasts 2 hours.
The test is carried out nil-by-mouth (empty stomach).
· For 30 days prior to the exam avoid use of laxatives and antibiotics
· For 15 days prior to the exam avoid use of probiotics (lactic ferments, yoghurt, milk and any other derivatives of animal origins). Almond milk, soya milk and rise milk can be consumed)
· Abstain from using non-essential medicines in the 12 hours before the exam. On the day of the exam the patient can continue to take “life-saving” medicines such as those for blood pressure and the heart, avoiding however Eutirox
· The doctor must be sure that the patient does not have significant diarrhoea at the moment of the exam
a plate of boiled rice dressed with a little oil before 2.30pm, avoiding snacks between meals
steak or poached fish or soya hamburger with salad
· From 9pm of the day previous to the exam the patient must be completely nil by mouth (but can drink still water freely)
· On the morning of the exam the patient should clean their teeth well as usual with a toothbrush and toothpaste and then rinse the oral cavity with mouth wash
· 25 x Vials containing 50 g of glucose certified “food grade”
· 25 x25 x Heat-sealed sterile bags per the collection of breath equipped with closing clamps
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