Here's another interesting paper, which raises the possibility that dysautonomia of the ileocecal valve (ileo-cecal reflux) might also contribute to SIBO.
As that paper said, there's not much in the literature about the ileocecal valve aspect to SIBO but a couple of other studies also back up the theory that a dysfunctional valve can be implicated in contributing to causing SIBO.
https://pubmed.ncbi.nlm.nih.gov/24795035/ Low ileocecal valve pressure is significantly associated with small intestinal bacterial overgrowth (SIBO) (2014)
https://pubmed.ncbi.nlm.nih.gov/28871499/ A Prospective Evaluation of Ileocecal Valve Dysfunction and Intestinal Motility Derangements in Small Intestinal Bacterial Overgrowth (2017)
On a more controversial note, a recent SIBO review paper suggests the whole 'SIBO industry', as I like to call those pushing SIBO as 'the' reason for every symptom of GI upset, is getting it wrong to be overdiagnosing SIBO using the fatally flawed Lactulose Breath Test to diagnose the condition;
https://pubmed.ncbi.nlm.nih.gov/33037967/ Small Intestinal Bacterial Overgrowth Syndrome: A Guide for the Appropriate Use of Breath Testing (2021)
[ Abstract: The increased availability of noninvasive breath tests, each with limitations, has led to widespread testing for small intestinal bacterial overgrowth (SIBO) in patients with non-specific gastrointestinal complaints. The lactulose breath test (LBT) is based upon an incorrect premise and therefore incorrect interpretations which has resulted in the over-diagnosis of SIBO and the excessive use of antibiotics in clinical practice. Despite limitations, the glucose breath test (GBT) should be exclusively employed when considering SIBO in appropriately chosen patients. This review suggests guidelines for the optimal use and appropriate interpretation of the GBT for suspected SIBO. The lactulose breath test (LBT) should be discarded from future use, and the literature based upon the LBT should be discounted accordingly ]
The following paragraphs highlight what I see to be among the many important takeaways to be had from this review article. (A further point of note to bear in mind here is that GI motility studies into functional gastrointestinal disorders (FGID) find that it is far more prevalent in FGID to have rapid gastric emptying rather than having delayed gastric emptying).
[ However, the clinical issue is not to distinguish symptomatic patients from healthy subjects, but to distinguish, from among symptomatic patients, those whose symptoms are manifestations of the condition in question. In this regard, the lower cutoff value, for instance, distinguishes IBS patients from healthy subjects but not from disease controls [6]. Therefore, a critical question is what concentration and what type of bacteria are necessary to produce the metabolic consequences and symptoms associated with SIBO syndrome. In early studies of patients with conditions associated with SIBO such as stagnant loop syndromes or different types of partial gastrectomy, malabsorption of vitamin B12, bile acids, and fat were strongly associated with the presence of coliform organisms. Most such patients had much higher bacteria concentrations, in the range of 10 7 –10 9 cfu/ml[7 ]. When lower bacteria concentrations are used to define SIBO, fewer patients are found to have an underlying condition historically associated with SIBO. Furthermore, with lower cutoff concentrations for determining SIBO, symptoms do not correlate strongly with the presence of SIBO [8], and patients are not observed to have additional clinical benefit from antibiotic therapy [9]. An additional concern comes from recent findings suggesting that bacterial concentrations ≥ 10 5 can be observed in the proximal small bowel of healthy subjects consuming a high fiber diet [8]. This observation raises additional questions regarding how to interpret quantitative cultures without accounting for the subject's diet. ]
[ In a larger series of 139 patients undergoing concurrent GBT with scintigraphy, 48% had a false positive breath test resulting from rapid delivery of glucose to the colon [27]. The frequency of this finding depended upon whether the patients had a history of prior upper GI tract surgery. Among
patients with such surgery, 69% had an abnormal breath test result, but in 65% of these, this was a false positive result due to a rapid orocecal transit time (mean 16 min). This finding
also calls into question studies showing high rates of bacterial overgrowth in patients following foregut surgery, based on results of breath tests performed without scintigraphy [45–48]. Even in patients without such a surgical history, 13% had a false positive breath test due to colonic fermentation from rapid orocecal transit (mean 38 min) [27]. Patients with negative GBT or presumptive true positive tests for bacterial overgrowth had similar orocecal transit times (mean 86
and 79 min, respectively), which were significantly longer than those with a false positive test. These findings demonstrate convincingly that a positive GBT cannot be interpreted without knowing the orocecal transit time. ]
[ Because patients with profound intestinal stasis can have ongoing retention and thus fermentation of carbohydrates, the presence of a high fasting hydrogen level alone is considered to be diagnostic of SIBO by some. A major difficulty with such a conclusion is that baseline breath hydrogen values are greatly influenced by the diet leading up to the breath test [50]. If the pretest protocol does not require a diet low in fermentable substrates, or such a diet is not followed, high baseline hydrogen values likely represent fermentation of these dietary constituents in the colon rather than SIBO. In a patient with slow transit constipation, several days of a low fermentation diet may be required to reduce fasting levels of breath hydrogen to normal. High baseline values also occur in untreated celiac disease [51, 52]. In our experience, patients with SIBO syndrome associated with luminal stasis and high fasting hydrogen levels show dramatic elevations in hydrogen values above this baseline following glucose administration. Unless the patient is known to have significant problems with stasis, breath tests with baseline elevations of hydrogen only should be considered technically unsatisfactory and uninterpretable. ]
[ Main conclusion; We believe that most of the literature on SIBO performed with lactulose-based testing is fundamentally flawed, as it is based on an incorrect premise and therefore incorrect conclusions. This has resulted in the overdiagnosis of SIBO and the excessive use of antibiotics in clinical practice. ]
