Tag: Lactulose breath test

Understanding Double Peak Patterns in Lactulose SIBO Breath Testing

Posted on by Melissa Zinda

When it comes to lactulose breath testing for Small Intestinal Bacterial Overgrowth (SIBO), one of the patterns that may emerge is the double peak. This refers to two distinct rises in gas levels during the breath test. The first peak occurs when bacteria in the small intestine ferment the lactulose. The second peak happens as the lactulose reaches the colon. At this point, colonic bacteria begin their fermentation process. Although this double peak pattern was part of the diagnostic criterion for SIBO, improvements in testing methodology changed how these results are interpreted. While no longer considered definitive for diagnosing SIBO, the double peak still provides valuable insights into the overall health of the digestive system.

The Lactulose Breath Test Double Peak Explained

In a positive SIBO test, lactulose (a non-absorbable sugar) is fermented by bacteria in the small intestine. Within the first 120 minutes of testing, the fermentation causes the first rise or “peak” in hydrogen (H₂) or methane (CH₄) gases. This early gas production indicates excessive bacterial fermentation in the small intestine. As this area typically harbors fewer bacteria than the colon, this peak is considered abnormal. The second peak occurs when the remaining lactulose moves into the large intestine (colon). It is a normal result, reflecting healthy bacterial activity in the colon. However, extreme spikes in activity in the large intestines may indicate overgrowth/ abnormal activity. (See figure 1)

Classic double peak lactulose sibo breath test result
Figure 1: Classic double peak observed during a lactulose breath test. Two distinct rises in gas levels during the breath test are observed. Peak one occurs when bacteria in the small intestine ferment the lactulose. The second peak happens as the lactulose reaches the colon, where colonic bacteria begin their fermentation process.

Double Peak Results: Transition from Diagnostic Use

Historically, a double peak was considered a clear indicator of SIBO. The idea was that if lactulose caused gas levels to rise in both the small and large intestines, bacterial overgrowth was present in the small intestine. However, with advancements in understanding SIBO and improved breath testing techniques, the double peak is no longer used as a primary diagnostic criterion. Now, research shows that the timing and levels of gas production can be influenced by multiple factors including gut motility and variations in the transit time of lactulose through the intestines.

Despite this, a double peak is still a common finding in breath testing. It can offer useful clinical information, especially for differentiating between small intestinal fermentation (indicative of SIBO) and colonic fermentation.

The Transition Period: 100-120 Minutes

One crucial aspect of lactulose breath testing is the transition period between 100 and 120 minutes. During this time, lactulose moves from the small intestine into the large intestine. This may result in a temporary drop in measurable gas activity often seen on breath test results. Levels drop because lactulose has finished fermenting in the small intestine but hasn’t yet begun in the colon.

This transition phase can be helpful for clinicians in interpreting results. For example, if a significant gas rise occurs before 120 minutes, it suggests bacteria in the small intestine are producing those gases. This rise is diagnostic for SIBO. However, if gas levels stay low or drop during the transition, then rise sharply after 120 minutes, it indicates fermentation in the large intestine. Fermentation in the large intestine is normal and expected. However, extreme increases may suggest irregularities.  Delayed transition periods can occur especially in patients with slow gut motility, constipation and gastroparesis (see Figure 2). 

Example of delayed double peak in SIBO breath test results
Figure 2: Double peak observed during a lactulose breath test. Baseline elevated hydrogen gas activity and transition period at 140 minutes suggest slow gut motility.

Importance of Differentiating Small vs. Large Intestinal Activity

Although the double peak is no longer a diagnostic requirement for SIBO, it remains valuable for assessing bacterial activity throughout the digestive tract. By analyzing both the early (small intestine) and late (large intestine) fermentation patterns, clinicians determine if bacterial overgrowth is confined to the small intestine or if other digestive issues, such as colonic dysbiosis, might also be present. The transition period between 100 and 120 minutes offers further insight. It helps pinpoint where gas production is happening—information that can guide diagnostic and treatment decisions.

Double Peak Case Study

Presentation: A 42 year old male with sudden onset of severe constipation, bloating, flatus and lower diffuse abdominal pain since food poisoning in the summer of 2023. 

After the first positive SIBO breath test, he was treated with a combination of herbal and prescriptive antibiotics and an herbal prokinetic. The patient reported initial symptom improvement and then progressively worsening constipation and bloating.                         

Retesting indicated lower gas activity from the previous breath test. However, an “elevated” baseline and late double peak indicate reduced gut motility and delayed intestinal emptying. Prescriptive prokinetic was begun with frequent monitoring (every 2-4 weeks) until motility improved without bloating. The goal is to eventually titrate off motility support over time. 

Prolonged double peak case study
Case Study Image 1: First breath test was a strong positive. Baseline levels are elevated.  Delayed emptying into the colon is indicated.
Double peak results indicating delayed colonic emptying
Case Study Image 2: Second breath test was negative. Baseline levels are elevated. Results indicate delayed emptying into the colon.

Conclusion

The double peak pattern in lactulose breath testing provides important clues about how bacterial fermentation occurs in both the small and large intestines. While no longer considered diagnostic for SIBO on its own, observing the timing and levels of gas production in relation to the transition period differentiates between small intestinal overgrowth and normal colonic fermentation. For patients with unexplained digestive symptoms, understanding these patterns guides effective treatment strategies, ensuring a more tailored approach to gut health management. Learn more about abnormal breath test patterns.

Common Breath Test Results Part 1: SIBO

Posted on by Bradley Bush

SIBO (small intestinal bacterial overgrowth) breath testing measures the production of hydrogen and methane gases by bacteria in the gut. These breath test results offer important insights into bacterial overgrowth.  First, individuals ingest glucose or lactulose, which are fermented by bacteria in the small intestine. By assessing the changes in gas production during the breath test, SIBO can be diagnosed. This article is part one of a three-part series discussing common trends and diagnostic criteria for both glucose and lactulose breath testing.

Glucose Breath Test Results

Glucose is absorbed in the small intestine relatively quickly, making it an excellent substrate for detecting bacterial overgrowth in the upper part of the small intestine.

Positive Glucose SIBO Breath Test Results (Hydrogen or Methane Elevation within 120 minutes)

  • Hydrogen Rise: An increase in hydrogen gas of 12 ppm or more within the first 120 minutes meets the diagnostic criteria for SIBO (Figure 1). This indicates that bacteria in the small intestine are fermenting glucose before it can be fully absorbed.

    Graph showing positive SIBO results
    Figure 1: Hydrogen Rise: An increase in hydrogen gas. Glucose is mostly absorbed in the small intestines therefore the increase in gas is from bacteria.
  • Peak Methane Levels: A peak methane level of 10 ppm or more within 120 minutes suggests the presence of methane-producing bacteria in the small intestine, meeting the criteria for SIBO (Figures 2 & 3). Methane-producing bacteria are often associated with constipation.
    Graph showing increasing levels of methane on SIBO test
    Figure 2 Peak Methane Level: Methane gas activity achieves a level of more than 10 ppm from 60-180 minutes of the test. This indicates the presence of methane producing bacteria and SIBO.Graph showing elevated methane levels on a SIBO test

    Figure 3 Peak Methane Level: Methane gas activity elevated throughout test (baseline to 180 minutes).

  • Combined Hydrogen + Methane Rise: An increase in the combined total of hydrogen and methane gas of 12 ppm or more within the first 120 minutes meets the diagnostic criteria for SIBO (Figure 4). This indicates bacteria in the small intestine ferment the glucose before it can be fully absorbed.
    Graph showing positive SIBO results based on combined gas levels
    Figure 4 Combined Hydrogen + Methane Rise: A rise in the combined total of hydrogen and methane gas of 12 ppm (glucose)/ 15 ppm (lactulose) or more within the first 120 minutes meets the diagnostic criteria for SIBO. This is an example of a positive glucose breath test result.

     

Negative Glucose SIBO Breath Test Results

In healthy individuals, glucose absorbs before it reaches the large intestine, and there is no significant rise in hydrogen or methane within the first 120 minutes (Figure 5). Gas production occurring after 120 minutes reflects normal fermentation in the large intestine.

graph showing negative SIBO test
Figure 5 Negative SIBO: No significant increases in hydrogen gas, methane levels below 10 ppm, and insignificant levels of combined gases indicates negative breath test results.

 

Lactulose Breath Test Results 

Lactulose is not absorbed by the body and passes through both the small and large intestines, making it useful for detecting bacterial overgrowth in both regions. 

Lactulose Positive SIBO Breath Test Results (Early Hydrogen or Methane Rise within 120 minutes)

  • Hydrogen Rise: A hydrogen increase of 20 ppm or more within the first 120 minutes meets the diagnostic criteria for SIBO, indicating fermentation in the small intestine by bacteria (Figure 6).graph showing a positive lactulose breath test resultsFigure 6 Hydrogen Rise: An increase in hydrogen gas. Lactulose is not absorbed in the intestines. Therefore, large intestinal bacterial fermentation is observed (typically 140-180 minutes).
  • Peak Methane Levels: A peak methane level of 10 ppm or more within 120 minutes suggests the presence of methane-producing bacteria in the small intestine. This meets the criteria for SIBO (Figures 2 & 3). Methane-producing bacteria are often associated with constipation.
  • Combined Hydrogen + Methane Rise: An increase in the combined total of hydrogen and methane gas of 15 ppm or more within the first 120 minutes meets the diagnostic criteria for SIBO (Figure 4). This indicates bacteria in the small intestine ferment lactulose. 

Lactulose Negative SIBO Breath Test Results

In a negative test, there will be no significant gas rise in the first 120 minutes. Additionally, gas production typically rises after this period, reflecting normal lactulose  fermentation within the large intestine (Figure 5).

Common Trends in Hydrogen and Methane Gas Production

  • Hydrogen-Dominant SIBO: Patients with diarrhea-predominant symptoms (IBS-D) often show elevated hydrogen levels. A sharp rise in hydrogen gas, particularly early in the breath test, suggests bacterial fermentation of glucose or lactulose in the small intestine. (Figures 1 & 6)
  • Methane-Dominant SIBO: Patients with constipation-predominant symptoms (IBS-C) usually present with elevated methane levels. High methane gas, especially when peaking at 10 ppm or more within 120 minutes, indicates the presence of methanogenic archaea. The presence of these bacteria can slow intestinal transit. (Figures 2 & 3)
  • Mixed Hydrogen and Methane Production: Some patients may show elevated levels of both hydrogen and methane gases, leading to a mix of symptoms such as alternating diarrhea and constipation. This pattern can indicate the presence of both bacterial overgrowth and methanogens in the small intestine. (Figure 4)
  • Double Peak Patterns:  For lactulose, a double peak may be observed. If SIBO is present, the first peak occurs within 120 minutes due to small intestinal fermentation. As lactulose reaches the colon, fermentation by colonic bacteria cause the second peak (Figure 7). Double peak results used to be diagnostic for SIBO but are not anymore due to improvements in testing methodology. However, double peaks seen on testing can assist in differentiating between small and large intestine specimen assessments. 

    graph showing a double peak in a lactulose breath test result
    Figure 7: Classic double peak observed during a lactulose breath test. Two distinct rises in gas levels during the breath test are observed. The first peak occurs when bacteria in the small intestine ferment the lactulose. The second peak happens as lactulose reaches the colon where colonic bacteria begin their fermentation process.

Conclusion

Both glucose and lactulose are good substrates for SIBO breath testing. For glucose breath tests, a rise in hydrogen levels or combined gases of 12 ppm or more within 120 minutes meets the criteria for diagnosing SIBO. For lactulose breath tests, hydrogen levels rising by 20 ppm or more or 15 ppm (combined gases) within 120 minutes also indicate SIBO. Peak methane levels of 10 ppm or more indicate methane-dominant SIBO. These tests help clinicians distinguish between hydrogen-dominant and methane-dominant SIBO, leading to more targeted treatment plans.

This is the first blog in a three-part series. Part 2 discusses fructose, lactose, and sucrose sugar malabsorption patterns. In part 3, learn about atypical breath test patterns.