SIBO Sleuth: Diagnosing Small Intestinal Bacterial Overgrowth
What is SIBO (Small Intestinal Bacterial Overgrowth)?
SIBO stands for Small Intestinal Bacterial Overgrowth.
Normally there are hundreds of trillions of bacteria that live in your colon or large intestine. In the small intestine, the numbers are usually much smaller - only in the hundreds. However, certain conditions can cause more bacteria to grow in the small intestine - where they don’t belong!
This isn’t an infection. This is an overgrowth where the bacteria are growing in higher numbers than they should.
There are several technical definitions, but in patients with normal GI anatomy, this is defined as:
More than 10^3 colonies/ mL
What are the symptoms of SIBO?
Symptoms of Small Intestinal Bacterial Overgrowth (SIBO)
SIBO symptoms can lead to various unpleasant symptoms and can significantly impact a person's quality of life.
While the symptoms may vary from person to person, there are several common signs that may indicate the presence of SIBO. Some of these symptoms include:
1. Abdominal Discomfort: Many individuals with SIBO experience chronic or recurrent abdominal discomfort, often described as bloating, distension, or a feeling of fullness. This discomfort can range from mild to severe and may worsen after meals.
2. Excessive Gas: SIBO can lead to excessive production of gas in the small intestine. This can cause frequent belching, flatulence, and a sensation of gurgling or rumbling in the abdomen. The gas produced by bacteria in the small intestine may also have an unpleasant odor.
Most commonly I see patients with SIBO having significant gas and bloating within a short time of eating - especially after eating a high carbohydrate meal. This is because the carbohydrates may get fermented in the intestines instead of getting digested and absorbed in the small intestine.
3. Digestive Issues: SIBO can interfere with the normal digestion and absorption of nutrients. As a result, individuals with SIBO may experience symptoms such as diarrhea, constipation, or a combination of both (alternating bowel habits).
4. Malnutrition and Weight Loss: Due to impaired nutrient absorption in the small intestine, SIBO can lead to deficiencies in essential nutrients, including vitamins and minerals. Over time, this can result in weight loss, malnutrition, and associated symptoms such as fatigue, weakness, and anemia.
5. Food Intolerances: Many people with SIBO find that they have an increased sensitivity to certain types of food. Consuming foods high in fermentable carbohydrates, known as FODMAPs, can worsen symptoms. These individuals may experience bloating, gas, diarrhea, or other digestive issues after ingesting certain foods.
6. Nausea and Vomiting: SIBO can trigger feelings of nausea and may even lead to episodes of vomiting in some cases. This is often more pronounced after eating or taking certain medications.
Can you have both irritable bowel syndrome and SIBO?
The overlap of IBS and SIBO
Irritable bowel syndrome (IBS) and small intestinal bacterial overgrowth (SIBO) are two commonly encountered gastrointestinal conditions that often exhibit an overlap in symptoms. This intersection between IBS and SIBO has definitely been seen, and some studies show that up to 1/3 of all children and adults with IBS are also diagnosed with SIBO.
IRRITABLE BOWEL SYNDROME is a disorder of the gut brain interaction that characterized by abdominal discomfort or pain, along with changes in bowel habits such as diarrhea, constipation, or both. It is a diagnosis of exclusion, meaning that other organic causes must be ruled out before attributing the symptoms to IBS. On the other hand, SIBO is a condition characterized by an overgrowth of bacteria in the small intestine, leading to symptoms such as bloating, diarrhea, abdominal pain, and malabsorption.
The connection between IBS and SIBO lies in the fact that both conditions share similar symptoms, such as bloating and alterations in bowel habits. In studies examining patients with IBS, a high prevalence of SIBO has been observed, suggesting a possible link between the two. However, it is important to note that not all patients with IBS have SIBO, and not all patients with SIBO have IBS. The relationship between these two conditions is complex and not yet fully understood.
Several theories attempt to explain the association between IBS and SIBO. One thought is that the altered gut motility seen in IBS may predispose individuals to SIBO. Normally, there are squeezing and peristalsis movements along the GI tract that helps to sweep bacteria out of the small intestine, preventing their overgrowth. However, in patients with IBS, this motility and movement may be impaired, allowing bacteria to accumulate and multiply in the small intestine.
Another theory suggests that the presence of SIBO may trigger symptoms in susceptible individuals by causing an inflammatory response or by producing gas and other metabolites that can irritate the gut. This may explain why some patients with SIBO experience symptoms resembling IBS.
The diagnosis of SIBO can be challenging as the symptoms overlap with those of IBS. Breath testing, using lactulose or glucose as substrates, can help detect the presence of excessive bacterial fermentation in the small intestine. However, these tests have limitations and should be interpreted in the context of the patient's clinical presentation.
Management of the overlap between IBS and SIBO mainly focuses on addressing the underlying bacterial overgrowth if present. Antibiotics that target the overgrown bacteria in the small intestine,
How is SIBO diagnosed?
Small intestinal bacterial overgrowth (SIBO) is typically diagnosed through a combination of medical history assessment, symptom evaluation, and certain diagnostic tests. During the intake (where the provider talks with the patient or family), the provider will inquire about the patient's symptoms, such as chronic bloating, abdominal pain, diarrhea, or constipation. A breath test is commonly used to diagnose SIBO, where the patient ingests a solution containing either lactulose or glucose, and their breath is then analyzed for the presence of gases produced by bacteria. In some cases (if a breath test isn’t reliable for certain patients), a small intestine biopsy or endoscopy with aspiration may be recommended. An accurate diagnosis is crucial to initiate appropriate treatment and alleviate the symptoms associated with SIBO.
Types of SIBO tests:
Endoscopy with duodenal or jejunal aspiration and culture.
Endoscopy and Jejunal Aspiration in SIBO Diagnosis
Endoscopy and jejunal aspiration are two diagnostic procedures commonly used in the evaluation and diagnosis of small intestinal bacterial overgrowth (SIBO).
Endoscopy (Upper Gastrointestinal Endoscopy):
Endoscopy is a minimally invasive procedure that allows direct visualization of the upper gastrointestinal tract using a thin, flexible tube called an endoscope. The endoscope is equipped with a light and a camera, which provides a detailed view of the esophagus, stomach, and first part of the small intestine (duodenum).
During the procedure, the patient is usually under anesthesia (in children) or sedated (in adults) to ensure comfort, and the endoscope is gently inserted through the mouth and guided down the esophagus. The doctor examines the lining of the upper digestive tract for any abnormalities such as inflammation, ulcers, or strictures. While endoscopy can help identify certain conditions that may contribute to SIBO, it is not specifically designed to diagnose the presence of bacterial overgrowth.
Jejunal Aspiration:
Jejunal aspiration, also known as duodenal or small bowel aspirate, is a procedure performed during an endoscopy to collect a sample of fluid and bacteria from the small intestine. It is considered the gold standard for diagnosing SIBO.
After the endoscope reaches the duodenum, the doctor navigates it into the jejunum (the middle part of the small intestine). Using a small suction tube attached to the endoscope, a sample of fluid is aspirated from the jejunum. This sample is then sent for analysis to identify the type and quantity of bacteria present.
Purpose in SIBO Diagnosis:
Endoscopy with jejunal aspiration is done for SIBO diagnosis because it allows direct access to the small intestine, where bacterial overgrowth is suspected. By analyzing the fluid collected during the aspiration, the number and types of bacteria present can be determined.Because this method of diagnosis is invasive and expensive, we often look for other ways to diagnose SIBO, like the breath test.
Breath Test:
Breath Test for SIBO Diagnosis: Test and Interpretation
A breath test is commonly used as a non-invasive diagnostic tool for Small Intestinal Bacterial Overgrowth (SIBO). This test measures the levels of specific gases produced by gut bacteria, helping to determine if there is an overgrowth of bacteria in the small intestine. Let's describe the procedure, preparation process, and interpretation of a breath test for SIBO. Note: I always warn my patients that the test is long and BORING (so bring a book to read or movie to watch!).
Preparation Process:
To ensure accurate results, it is crucial to follow the preparation process provided by your healthcare provider. Key aspects of the preparation might include:
1.. Medication Considerations: Certain medications, such as antibiotics, probiotics, and certain gastrointestinal medications, may need to be stopped for a specified period before the test, as they can affect the bacterial levels in the gut.
2. Fasting Period: In some cases, a period of fasting (typically overnight) may be required before the test to empty the stomach. NO BREAKFAST!
3. Avoidance of Certain Substances: Patients are usually told to NOT take antibiotics or probiotics for 2 weeks prior to the procedure as these can interfere with the accuracy of the test.
4. Brushing teeth: Sorbitol and other sugars in toothpaste can interfere with the test results. Therefore, the morning of the test, patients are usually instructed to rinse their mouth or brush their teeth with water only.
Procedure:
1. Collection of Baseline Breath Sample: Before starting the test, the patient is required to provide a baseline breath sample by exhaling into a collection bag or tube. This baseline sample is crucial for comparison with subsequent breath samples.
2. Administering the Test Substance: The patient drinks a sugary drink like lactulose or glucose, which is not readily absorbed in the small intestine but is instead fermented by bacteria.
3. Breath Sample Collection: Over the next two to three hours, depending on the specific test, the patient is asked to provide breath samples at regular intervals. These samples are usually collected every 15 or 20 mins. These samples are typically collected by blowing into labeled collection bags or tubes.
4. Analyzing the Breath Samples: The collected breath samples are then sent to a laboratory for analysis.
5. Interpreting the Results: After analyzing the breath samples, the laboratory will report the levels of various gases, such as hydrogen (H2) and methane (CH4), and sometimes hydrogen sulfide (H2S) produced during the test. These measurements are often compared to the baseline sample and standardized criteria to determine the presence and severity of SIBO.
Interestingly, our bodies and human cells don’t produce hydrogen or methane. Therefore, all the gas that is produced is made from the bacteria in the gut that fermented the sugary drink. This gas eventually passes from the GI tract through the blood into the lungs and out of the breath (which is collected).
Your doctor will let you know if your test is positive or negative for SIBO.
