Lactose malabsorption in the elderly: role of small intestinal bacterial overgrowth

OBJECTIVE: The prevalence of lactose malabsorption (LM) is increased in the elderly, although the mechanisms responsible are still a matter of speculation. The objective of this study was to investigate the possible roles of reduced functional small intestinal absorptive area, lactase deficiency and small intestinal bacterial overgrowth (SIBO). MATERIAL AND METHODS: Twenty Caucasian (Anglo-Celtic), asymptomatic, well-nourished, elderly volunteers (median age 79 years, range 70-94 years) with no clinically apparent predisposition to SIBO underwent a 50 g lactose breath hydrogen test (LBHT) and mannitol absorption test, the latter as an index of functional small intestinal absorptive area. Those with LM additionally underwent bacteriological assessment of small intestinal secretions and mucosal biopsy, to assess the contribution of SIBO and lactase deficiency, respectively, to the pathogenesis of LM in individual cases. The prevalence of SIBO was also determined in elderly subjects without LM. Twenty asymptomatic younger subjects (median age 29 years, age range 18-35 years) served as controls. All subjects were "hydrogen producers" in response to lactulose. RESULTS: LM was evident in 10/20 (50%) elderly subjects and 1/20 (5%) younger subjects (p=0.003). Mannitol absorption did not differ significantly in elderly and younger subjects or in elderly subjects with and without LM. SIBO was documented in 9/10 (90%) elderly subjects with LM; eradication was associated with resolution of LM. Lactase deficiency was evident in only one elderly subject with LM. SIBO was evident in 2/10 (20%) elderly subjects without LM (p=0.005 compared to those with LM). Lactulose breath hydrogen test identified only 2/11 (18%) elderly subjects with SIBO. CONCLUSIONS: Increased prevalence of LM in the elderly is mostly due to clinically non-apparent SIBO, rather than mucosal factors. The lactulose breath hydrogen test cannot be relied upon to identify elderly subjects with SIBO, even in those without an anatomical predisposition.     

Lower frequency of MMC is found in IBS subjects with abnormal lactulose breath test,suggesting bacterial overgrowth

We have recently described an association between irritable bowel syndrome (IBS) and abnormal lactulose breath test, suggesting small intestinal bacterial overgrowth (SIBO). However, the mechanism by which SIBO develops in IBS is unknown. In this case–control study we evaluate the role of small intestinal motility in subjects with IBS and SIBO. Small intestinal motility was studied in consecutive IBS subjects with SIBO on lactulose breath test. After fluoroscopic placement of an eight-channel water-perfused manometry catheter, 4-hr fasting recordings were obtained. Based on this, the number and duration of phase III was compared to 30 control subjects. To test whether there was a relationship between the motility abnormalities seen and the SIBO status of the patient at the time of the motility, subjects with a breath test within 5 days of the antroduodenal manometry were also compared. Sixty-eight subjects with IBS and SIBO were compared to controls. The number of phase III events was 0.7 ± 0.8 in IBS subjects and 2.2 ± 1.0 in controls (P < 0.000001). The duration of phase III was 305 ± 123 sec in IBS subjects and 428 ± 173 in controls (P < 0.001). Subjects whose SIBO was still present at the time of manometry had less frequent phase III events than subjects with eradicated overgrowth (P < 0.05). In conclusion, phase III is reduced in subjects with IBS and SIBO. Eradication of bacterial overgrowth seems to result in some normalization of motility.     

Early hydrogen excretion peaks during breath tests. Small intestinal bacterial overgrowth or accelerated transit?

BackgroundSmall intestinal bacterial overgrowth (SIBO) has been reported with varying prevalence, depending upon the criteria used for diagnosis. Lactulose and glucose breath tests are the most used in clinical settings. Early rises of hydrogen excretion during a lactose breath test suggest SIBO, but the finding could result from accelerated mouth-to-caecum transit time.AimsDefining the prevalence of early hydrogen peaks during lactose breath tests and assessing the proportion of patients affected by SIBO.MethodsAn early (≤ 60′) hydrogen excretion peak was observed in 120/663 patients with positive lactose hydrogen breath test. Eighty-one of them underwent a 50 g-9sample-glucose hydrogen breath test to diagnose SIBO.ResultsThe glucose breath test proved positive in 11/81 (13.6%) patients. The positivity rate was 18.2% (2/11) in those with the first peak detected at 30′ and 12.8% (9/70) in those with the peak occurring at 60′.ConclusionsEarly hydrogen excretion peaks are rarely associated with SIBO. The low positive predictive value indicates that the finding does not help identifying patients at high risk for this condition. Indirectly, the present data support the opinion that the prevalence of SIBO diagnosed by standard lactulose breath tests is much lower than reported, and the reliability of the test is low.     

Transient Lactose Malabsorption in Patients Affected by Symptomatic Uncomplicated Diverticular Disease of the Colon

Lactose malabsorption (LM) may be secondary to several small bowel diseases, and small intestinal overgrowth (SIBO) may be one of them. We looked for a correlation between symptomatic diverticular disease of the colon and LM and assessed whether this correlation may be related to SIBO. Ninety consecutive patients (pts; 39 males, 51 females; mean age, 67.2 years; range, 32–91 years) affected by symptomatic uncomplicated diverticular disease of the colon were evaluated to assess orocecal transit time (OCTT), SIBO, and LM by lactulose and lactose H₂ breath test (H₂-BT) at entry and after 8 weeks of treatment. OCTT was delayed in 67 of 90 pts (74.44%). Fifty-three of 90 pts (58.88%) showed SIBO, and OCTT was normal in 23 of 90 pts (25.56%). LM was diagnosed in 59 of 90 pts (65.55%): 49 of 59 (71.74%) were simultaneously affected by SIBO and delayed OCTT (and thus 49 of 53 pts [92.45%] with delayed OCTT and SIBO were affected by LM); 3 of 59 pts (5.09%) showed only delayed OCTT; 7 of 59 pts (11.86%) did not show either SIBO or delayed OCTT. The association of LM and SIBO was statistically significant (P < 0.001). Seventy-nine of 86 pts (91.86%) showed normal OCTT, while OCTT remained prolonged but shorter in the remaining 7 pts (8.14%). SIBO was eradicated in all pts completing the study, while a new lactulose H₂-BT showed persistence of SIBO in one pt with recurrence of symptomatic diverticular disease. Forty-seven of 59 pts (79.66%) had a normal lactose H₂-BT (P < 0.002), while 12 of 59 pts (20.34%) showed persistence of LM. LM disappeared in 46 of 49 pts (93.88%) concurrently with normalization of OCTT and eradication of SIBO (P < 0.002); it also disappeared in 1 of 3 pts (33.33%) previously affected by delayed OCTT (without SIBO) and LM concurrently with normalization of OCTT. On the contrary, it persisted in all pts with normal OCTT and absence of SIBO. Moreover, it persisted also in the pt with recurrence of symptomatic diverticular disease and persistence of SIBO. In conclusion, most pts affected by symptomatic uncomplicated diverticular disease of the colon showed LM, and in more than 70% of cases it disappeared after successful treatment of the colonic disease.     

COLIGENTA treatment of small intestinal bacterial overgrowth. Results of an open study.

PurposeThe treatment of small intestinal overgrowth (SIBO) varies according to the center. The present study aimed to evaluate the efficacy of COLIGENTA, an association of colimycin and gentamycin, on SIBO symptomatology and breath test normalizationPatients and MethodsIn this prospective cross-sectional open study, 150 patients with functional bowel disorders and SIBO diagnosed by lactulose hydrogen breath test (LHBT) underwent COLIGENTA oral treatment. A new HLBT was performed 4 weeks after the first HLBT.ResultsThe patients were mainly female (74%), with a mean age of 47.4 ± 16.2 years and a body mass index of 26.2 ± 5.9 kg/m². After treatment, a decrease of expired hydrogen concentration (P<0.001) was found in the entire population. Improvement of gastrointestinal symptoms was found in 129 patients (86%), while the breath test's normalization was found in 62 patients (42%). Logistic regression showed that normalization of bowel symptoms was not associated with demographics, clinical, or hydrogen breath concentration. In contrast, normalization of LHBT was associated with an increase of breath hydrogen concentration at time 100 min during the first test (P = 0.003; OR=1.072; 95%CI= [1.023–1.123]).ConclusionThe present study shows that 10-days of COLIGENTA treatment has a high SIBO clinical improvement rate and can be used as the first or second treatment line.     

A link between irritable bowel syndrome and fibromyalgia may be related to findings on lactulose breath testing

BACKGROUND: An association between irritable bowel syndrome (IBS) and small intestinal bacterial overgrowth (SIBO) has been found. OBJECTIVE: To compare the prevalence and test results for bacterial overgrowth between IBS and fibromyalgia. METHODS: Subjects with independent fibromyalgia and IBS were compared with controls in a double blind study. Participants completed a questionnaire, and a lactulose hydrogen breath test was used to determine the presence of SIBO. The prevalence of an abnormal breath test was compared between study participants. Hydrogen production on the breath test was compared between subjects with IBS and fibromyalgia. The somatic pain visual analogue score of subjects with fibromyalgia was compared with their degree of hydrogen production. RESULTS: 3/15 (20%) controls had an abnormal breath test compared with 93/111 (84%) subjects with IBS (p<0.01) and 42/42 (100%) with fibromyalgia (p<0.0001 v controls, p<0.05 v IBS). Subjects with fibromyalgia had higher hydrogen profiles (p<0.01), peak hydrogen (p<0.0001), and area under the curve (p<0.01) than subjects with IBS. This was not dependent on the higher prevalence of an abnormal breath test. The degree of somatic pain in fibromyalgia correlated significantly with the hydrogen level seen on the breath test (r = 0.42, p<0.01). CONCLUSIONS: An abnormal lactulose breath test is more common in fibromyalgia than IBS. In contrast with IBS, the degree of abnormality on breath test is greater in subjects with fibromyalgia and correlates with somatic pain.     

Milk is a useful test meal for measurement of small bowel transit time

To improve and standardize the measurement of small bowel transit time, milk was employed for the test meal instead of the conventional lactulose meal. Although 92% of the subjects were lactase deficient, only 2% were milk intolerant and 13% were lactose intolerant. Small bowel transit time with milk (milk breath hydrogen test) was 113±9 min (mean ± SE,n=20); the normal range calculated from the mean ±2 SD was 31–195 min. The coefficient of variation in the milk hydrogen breath test was 13 ± 4% (n=6), whereas in the lactulose hydrogen breath test, it was 39±16% (n=10). The frequency of non-hydrogen producers, the occurrence of discomfort, and the reproducibility were better, though not significantly so, in the milk hydrogen breath test than in the lactulose. Since lactase activity in the intestine is variable in lactase-deficient subjects, small bowel transit times for milk may change from subject to subject. However, individual reproducibility of the milk hydrogen breath test is good. It could be useful for pharmacological experiments using paired comparison, for screening tests, or for the follow up of diseases in which small bowel transit time is affected.     

Proton Pump Inhibitor Therapy Does Not Affect Hydrogen Production on Lactulose Breath Test in Subjects with IBS

Background  

Evidence suggests a role for small intestinal bacterial overgrowth (SIBO) in IBS. Recently, the question has arisen whether the lactulose breath test (LBT) is abnormal in IBS subjects due to overlapping GERD and proton-pump inhibitor (PPI) usage.     

Small intestinal bacterial overgrowth

Small intestinal bacterial overgrowth (SIBO) syndrome is characterized in its florid form by diarrhoea and weight loss. The most common underlying factors are dysmotility, small intestinal obstruction, blind or afferent loops. Small intestinal bacterial overgrowth can be diagnosed by: 1) culture of jejunum aspirate for bacterial counts, 2) ¹⁴C-D-xylose breath testing, 3) non-invasive hydrogen breath testing using glucose or lactulose or 4) ¹⁴C-glycocholic acid breath testing. The treatment usually consists of the eradication of bacterial overgrowth with repeated course of antimicrobials, correction of associated nutritional deficiencies and, when possible, correction of the underlying predisposing conditions.     

硫化氢呼气试验在小肠细菌过度生长诊断中的应用价值初探

目的:探究硫化氢呼气试验（hydrogen sulfide breath test,SBT）在小肠细菌过度生长（small intestinal bacterial overgrowth, SIBO）诊断中的应用价值。方法:纳入2019年4—12月某高校学生,进行消化道症状和1周膳食问卷调查,以及乳果糖氢-甲烷呼气试验...     

Small intestinal bacterial overgrowth among patients with celiac disease unresponsive to a gluten free diet

Background/AimsLittle is known about the relationship between small intestinal bacterial overgrowth (SIBO) and celiac disease (CeD) in patients who are unresponsive to a gluten-free diet (GFD). This study aimed to determine the SIBO prevalence in patients with CeD who are unresponsive to a GFD.Materials and MethodsWe conducted a case-control study from July 2012 to September 2014. We included 32 patients with CeD who were unresponsive to a GFD and 52 healthy age- and sex-matched controls. Demographic, clinical, and laboratory data were obtained from patients’ medical records. Antitissue transglutaminase antibody determined by enzyme-linked immunosorbent assay was recorded, and lactulose hydrogen breath test (LHBT) was used to detect SIBO in all participants. Microbiological analysis, including jejunal aspirates obtained using upper endoscopy, was performed for only 20 patients with CeD.ResultsA total of 10 (31%) of 32 patients with CeD and 4 (7.7%) of 52 controls tested positive for LHBT, with a statistically significant difference (p=0.007). Of 20 cultures, 3 (15%) were positive with no statistically significant correlation between the cultures and LHBT (p=0.05). In a subgroup analysis of children who were 18 years old or younger, 7/24 (29.2%) patients with CeD had a positive LHBT compared with 3/32 (9.4%) controls, but this difference was not statistically significant (p=0.08).ConclusionThe prevalence of SIBO was 31% in unresponsive patients with CeD according to LHBT and 15% in the quantitative culture of the jejunal aspirate, which is comparable with the published Western literature     

Abnormal Breath Testing in IBS: A Meta-Analysis

Background  

Recent evidence suggests a role for enteric bacteria in the development of symptoms in subjects with irritable bowel syndrome (IBS). The concept was initially based on the common finding of an abnormal lactulose breath test to suggest the presence of small intestinal bacterial overgrowth (SIBO). Despite successful antibiotic studies based on these findings, the premise of bacterial overgrowth was met with skepticism due to the perceived inaccuracies of breath testing in humans. In this study, we conduct a systematic review and meta-analysis of the studies using breath testing in IBS subjects with comparison to healthy controls.     

Methane production and small intestinal bacterial overgrowth in children living in a slum

AIM:To analyze small intestinal bacterial overgrowth in school-aged children and the relationship between hydrogen and methane production in breath tests.METHODS:This transversal study included 85 children residing in a slum and 43 children from a private school,all aged between 6 and 10 years,in Osasco,Brazil.For characterization of the groups,data regarding the socioeconomic status and basic housing sanitary conditions were collected.Anthropometric data was obtained in children from both groups.All children completed the hydrogen(H 2) and methane(CH 4) breath test in order to assess small intestinal bacterial overgrowth(SIBO).SIBO was diagnosed when there was an increase in H 2 ≥ 20 ppm or CH 4 ≥ 10 ppm with regard to the fasting value until 60 min after lactulose ingestion.RESULTS:Children from the slum group had worse living conditions and lower nutritional indices than children from the private school.SIBO was found in 30.9%(26/84) of the children from the slum group and in 2.4%(1/41) from the private school group(P = 0.0007).Greater hydrogen production in the small intestine was observed in children from the slum group when compared to children from the private school(P = 0.007).A higher concentration of hydrogen in the small intestine(P 0.001) and in the colon(P 0.001) was observed among the children from the slum group with SIBO when compared to children from the slum group without SIBO.Methane production was observed in 63.1%(53/84) of the children from the slum group and in 19.5%(8/41) of the children from the private school group(P 0.0001).Methane production was observed in 38/58(65.5%) of the children without SIBO and in 15/26(57.7%) of the children with SIBO from the slum.Colonic production of hydrogen was lower in methaneproducing children(P = 0.017).CONCLUSION:Children who live in inadequate environmental conditions are at risk of bacterial overgrowth and methane production.Hydrogen is a substrate for methane production in the colon.     

Small intestinal bacterial overgrowth

Small intestinal bacterial overgrowth (SIBO) syndrome is characterized in its florid form by diarrhoea and weight loss. The most common underlying factors are dysmotility, small intestinal obstruction, blind or afferent loops. Small intestinal bacterial overgrowth can be diagnosed by: 1) culture of jejunum aspirate for bacterial counts, 2) 14C-D-xylose breath testing, 3) non-invasive hydrogen breath testing using glucose or lactulose or 4) 14C-glycocholic acid breath testing. The treatment usually consists of the eradication of bacterial overgrowth with repeated course of antimicrobials, correction of associated nutritional deficiencies and, when possible, correction of the underlying predisposing conditions.     

Frequency and Factors Associated with Small Intestinal Bacterial Overgrowth in Patients with Cirrhosis of the Liver and Extra Hepatic Portal Venous Obstruction

Spontaneous bacterial peritonitis (SBP), a common complication of cirrhosis of liver, might result from translocation of bacteria from the small bowel. However, there is scanty data on frequency of small intestinal bacterial overgrowth (SIBO) in patients with cirrhosis of the liver. There are no data on SIBO in patients with extra-hepatic portal venous obstruction (EHPVO) in the literature. A total of 174 patients with cirrhosis of the liver, 28 with EHPVO and 51 healthy controls were studied for SIBO using glucose hydrogen breath test (GHBT). Persistent rise in breath hydrogen 12 ppm above basal (at least two readings) was considered diagnostic of SIBO. Of 174 patients (age 47.2 ± 11.9 years, 80.5% male) with cirrhosis due to various causes, 67 (38.5%) were in Child’s class A, 70 (40.2%) class B and 37 (21.7%) class C. Of the 174 patients with cirrhosis, 42 (24.14%) had SIBO as compared to 1 of 51 (1.9%) healthy controls (P < 0.0001). Patients with EHPVO had similar frequency of SIBO compared to healthy controls [2/28 (7.14%) vs 1/51 (1.97%), P = ns]. Frequency of SIBO in Child’s A, B and C was comparable [13 (18.6%) vs 16 (23.9%) and 13 (35.1%), respectively; P = ns]. Presence of SIBO were not related to ascites, etiology of cirrhosis, and degree of liver dysfunction. SIBO is common in patients with cirrhosis of the liver. Patients with EHPVO do not have higher frequency of SIBO than healthy subjects. SIBO in cirrhosis is not related to the degree of derangement in liver function or of portal hypertension.     

Small intestinal bacterial overgrowth is common both among patients with alcoholic and idiopathic chronic pancreatitis

BackgroundSmall intestinal bacterial overgrowth (SIBO) is known to occur in patients with chronic pancreatitis, particularly of alcoholic etiology. There are, however, scanty data on frequency of SIBO in patients with chronic idiopathic pancreatitis and factors associated with its occurrence.Methods68 patients with chronic pancreatitis and 74 age and gender-matched healthy subjects (HS) were evaluated for SIBO using glucose hydrogen breath test (GHBT). Persistent rise in breath hydrogen 12 ppm above basal (at least two recordings) was diagnostic of SIBO.ResultSIBO was diagnosed more often among patients with chronic pancreatitis than controls (10/68 [14.7%] vs. 1/74 controls [1.3%]; p = 0.003). Of 68 patients, 22 (32.3%) had alcoholic and 46 (67.6%) had idiopathic chronic pancreatitis. SIBO was as commonly detected among patients with alcoholic as idiopathic pancreatitis (3/22 [13.6%] vs. 7/46 [15.2%]; p = 0.86). Age, gender, body mass index (BMI), steatorrhoea, pain, analgesic use, pancreatic calcifications and use of pancreatic enzyme supplements had no relationship with the presence of SIBO. Diabetes mellitus tended to be commoner among patients with chronic pancreatitis with than without SIBO (6/10 [60%] vs. 18/58 [31%]; p = 0.07).ConclusionSIBO was commoner among patients with chronic pancreatitis, both alcoholic and idiopathic, than HS. Though presence of SIBO among patients with chronic pancreatitis tended to be commoner among those with diabetes mellitus, there was no relationship with age, gender, BMI, steatorrhoea, pain, analgesic use, pancreatic calcifications and use of pancreatic enzyme supplements.     

Small Intestinal Bacterial Overgrowth versus Antimicrobial Capacity in Patients with Spontaneous Bacterial Peritonitis

Background: Spontaneous bacterial peritonitis (SBP) is a serious infection in cirrhotic patients with ascites. Both defects in the host defense mechanisms and the enhancement of the offensive factor (small intestinal bacterial overgrowth (SIBO)) may contribute to the development of SBP. Therefore, the aim of this study was to evaluate the role of SIBO versus various antimicrobial capacities in the pathogenesis of SBP in cirrhotic patients. Methods: Forty-five cirrhotic patients were enrolled in this study. Bacterial overgrowth was evaluated by breath hydrogen test (BH₂T). The hepatic reticuloendothelial system phagocytic index (HRESPI) was measured by intravenously injected colloid suspensions. Results:     

Hydrogen- and Methane-Based Breath Testing and Outcomes in Patients With Heart Failure

BackgroundRecent evidence endorses gut microbiota dysregulation in the pathophysiology of heart failure (HF). Small intestinal bacterial overgrowth (SIBO) might be present in HF and associated with poor clinical outcomes. Lactulose breath testing is a simple noninvasive test that has been advocated as a reliable indicator of SIBO. In patients with HF, we aimed to evaluate the association with clinical outcomes of the exhaled hydrogen (H₂) and methane (CH₄) concentrations through the lactulose breath test.Methods and ResultsWe included 102 patients with HF in which lactulose SIBO breath tests were assessed. Cumulative gas was quantified by the area under the receiver operating characteristic curve of CH₄ (AUC-CH₄) and H₂ (AUC-H₂). Clinical end points included the composite of all-cause death with either all-cause or HF hospitalizations, recurrent all-cause hospitalizations, and recurrent HF hospitalizations. Medians (interquartile ranges) of AUC-H₂ and AUC-CH₄ were 1290 U (520-2430) and 985 U (450-2120), respectively. In multivariable analysis, AUC-H₂ (per 1000 U) was associated with all-cause death/all-cause hospitalization (hazard ratio [HR] 1.21, 95% CI 1.04–1.40; P = .012), all-cause death/HF hospitalization (HR 1.20, 95% CI 1.03–1.40; P = .021), and an increase in the rate of recurrent all-cause (incidence rate ratio [IRR] 1.31, 95% CI 1.14–1.51; P < .001) and HF (IRR 1.41, 95% CI 1.15–1.72; P = .001) hospitalizations. AUC-CH₄ was not associated with any of these end points.ConclusionsAUC-H₂, a safe and noninvasive method for SIBO estimation, is associated with higher risk of long-term adverse clinical events in patients with HF. In contrast, AUC-CH₄ did not show any prognostic value.     

Diagnosing Small Intestinal Bacterial Overgrowth: A Comparison of Lactulose Breath Tests to Small Bowel Aspirates

Background

Duodenal aspiration (DA) and lactulose breath tests (LBT) are commonly performed to diagnose small intestinal bacterial overgrowth (SIBO). There are no data directly comparing these tests.

Aims

To investigate the agreement between DA and LBT for the diagnosis of SIBO.

Methods

A retrospective cohort study of adult patients who underwent a LBT and a DA at a tertiary care center over 9 years was assembled. LBT was considered positive if the hydrogen baseline or peak change measurement was ≥?20 ppm, and/or if the methane baseline or peak change was ≥?10 ppm. DA was considered positive if >?100,000 cfu/mL of gram-negative flora was identified on culture, and contaminated if >?100,000 cfu/mL of gram-positive flora was identified.

Results

A total of 106 patients were evaluated; 81 (76.4%) were female; the mean age was 53.4?±?15.9 years. 21 patients (19.8%) had evidence of contamination on DA. 14 (16.5%) patients had a positive DA result. Patients with diabetes mellitus and those with PPI use were more likely to have a positive DA (94.4% vs. 71.4%, p?=?0.007; 62% vs. 28.6%, p?=?0.021, respectively). 33 (31.1%) patients had a positive LBT. Patients with a history of small bowel resection were more likely to have a positive LBT (12.1% vs. 1.4%, p?=?0.016). DA and LBT results agreed in 54 patients (63.5%; kappa?=???0.02), indicating poor agreement.

Conclusions

The agreement between LBT and DA in evaluation for SIBO was poor. LBT may be favorable to DA, as LBT is safer, cheaper, and less likely to yield a contaminant result.

     

Methane production during lactulose breath test is associated with gastrointestinal disease presentation

It has recently been determined that there is an increased prevalence of bacterial overgrowth in IBS. Since there are two gases (hydrogen and methane) measured on lactulose breath testing, we evaluated whether the different gas patterns on lactulose breath testing coincide with diarrhea and constipation symptoms in IBS and IBD. Consecutive patients referred to the gastrointestinal motility program at Cedars-Sinai Medical Center for lactulose breath testing were given a questionnaire to evaluate their gastrointestinal symptoms. Symptoms were graded on a scale of 0–5. Upon completion of the breath test, the results were divided into normal, hydrogen only, hydrogen and methane, and methane only positive breath tests. A comparison of all subjects and IBS subjects was undertaken to evaluate diarrhea and constipation with regards to the presence or absence of methane. This was further contrasted to Crohn's and ulcerative colitis (UC) patients in the database. After exclusion criteria, 551 subjects from the database were available for comparison. Of the 551 subjects (P < 0.05, one-way ANOVA) and in a subgroup of 296 IBS subjects (P < 0.05, one-way ANOVA), there was a significant association between the severity of reported constipation and the presence of methane. The opposite was true for diarrhea (P < 0.001). If a breath test was methane positive, this was 100% associated with constipation predominant IBS. Furthermore, IBS had a greater prevalence of methane production than Crohn's or UC. In fact, methane was almost nonexistent in the predominantly diarrheal conditions of Crohn's and UC. In conclusion, a methane positive breath test is associated with constipation as a symptom.