Small-bowel bacterial overgrowth in the postgastrectomy syndrome

Clinical predictors of small intestinal bacterial overgrowth by duodenal aspirate culture

BACKGROUND

There has been increasing interest in small intestinal bacterial overgrowth (SIBO) after reports of a link with irritable bowel syndrome (IBS), yet our understanding of this entity is limited.

AIM

Our aim was to estimate the yield of patients undergoing duodenal aspirate culture, and to identify symptoms and features that predict SIBO.

METHODS

A medical chart review of patients who had undergone duodenal aspirate culture at an academic medical centre in 2003 was performed to record clinical characteristics and culture results. The associations between aspirate results and symptoms, medical diagnoses and medication use were assessed using logistic regression.

RESULTS

A total of 675 patients had available aspirate results. Mean age of the sample was 53 (s.d. 17) and 443 (66%) were female patients. Overall, 8% of aspirates were positive for SIBO; 2% of IBS patients had SIBO. Older age, steatorrhoea and narcotic use were associated with SIBO (P < 0.05). PPI use was not associated with SIBO, but was associated with bacterial growth not meeting criteria for SIBO (P < 0.05). Inflammatory bowel disease (IBD), small bowel diverticula and pancreatitis were positively associated with an abnormal duodenal aspirate (P < 0.05), but other conditions including IBS were not associated with SIBO.

CONCLUSION

Older age, steatorrhoea, narcotic use, IBD, small bowel diverticula and pancreatitis were associated with small intestinal bacterial overgrowth based on abnormal duodenal aspirate culture results. However, no clear associations of true small intestinal bacterial overgrowth with IBS or PPI use were detected, in contrast to recent speculation.

The role of small intestinal bacterial overgrowth in postgastrectomy patients

BACKGROUND

Small intestinal bacterial overgrowth (SIBO) is expected in postgastrectomy patients; however, its role has not been clarified. This study was to estimate the prevalence of SIBO and investigate the clinical role of SIBO in postgastrectomy patients.

METHODS

This prospective study involved 76 patients who underwent gastrectomy for early gastric cancer with no evidence of recurrence. An H(2)-CH(4) breath test with oral glucose challenge test was performed to diagnose SIBO and dumping syndrome. Sigstad dumping questionnaires, serum glucose, hematocrit and pulse rate were simultaneously monitored for every 30 min for 3 hours.

KEY RESULTS

There were significant differences in SIBO between the postgastrectomy patients and controls (77.6%vs 6.7%, P < 0.01). Abdominal fullness or borborygmus during oral glucose load were more common in SIBO-positive than in negative patients (50.8%vs 17.6%, P = 0.03), and were the independent factors for predicting SIBO in postgastrectomy patients (P = 0.02). The prevalences of dumping syndrome and hypoglycemia after oral glucose were 35 (46.1%) and 19 (25.0%), and were not different between both groups. However, the plasma glucose was significantly lower in SIBO-positive than in SIBO-negative patients at 120 and 150 min after oral glucose load (P < 0.05). No significant differences were observed in pulse rate and hematocrit in both groups.

CONCLUSIONS & INFERENCES

SIBO is common among postgastrectomy patients. It appears to be associated with postprandial intestinal symptoms and might aggravate late hypoglycemia. SIBO could be a new therapeutic target for managing intestinal symptoms in postgastrectomy patients.

Small intestinal bacterial overgrowth

Despite the current increase in interest in the role of the microbiota in health and disease and the recognition, for over 50 years, that an excess of colonic-type flora in the small intestine could lead to a malabsorption syndrome, small intestinal overgrowth remains poorly defined. This lack of clarity owes much to the difficulties that arise in attempting to arrive at consensus with regard to the diagnosis of this condition: there is currently no gold standard and the commonly available methodologies (the culture of jejunal aspirates and a variety of breath tests) suffer from considerable variations in their performance and interpretation, leading to variations in the prevalence of overgrowth in a variety of clinical contexts. Treatment is similarly supported by a scant evidence base and the most commonly used antibiotic regimens owe more to custom than clinical trials.

Application of the glucose hydrogen breath test for the detection of bacterial overgrowth in patients with cystic fibrosis--a reliable method?

Patients with cystic fibrosis (CF) have recently been deemed highly susceptible for bacterial intestinal overgrowth (BIO). We aimed to define the prevalence of BIO in children with CF by applying the H(2)-glucose breath test. Forty children with CF and ten healthy children received 1 g/kg D-glucose orally. Breath samples for H(2) content (ppm) were collected for 3 h. BIO was suspected if the breath hydrogen content increased by more than 20 ppm or if baseline concentrations topped 20 ppm. In 27 of 40 CF children (68%), breath hydrogen content exceeded 20 ppm. Whereas the breath hydrogen exhalation persisted above 20 ppm in almost all these children throughout the sampling period, none of the remaining children increased above this threshold. The high rate of CF children with elevated fasting hydrogen breath concentrations indicates that this phenomenon is less a sign of BIO rather than a consequence of global malabsorption and intestinal dysmotility.

Latest results (12-21 years) of a prospective randomized study comparing Billroth II and Roux-en-Y anastomosis after a partial gastrectomy plus vagotomy in patients with duodenal ulcers

INTRODUCTION

After a partial resection of the stomach, the continuity of the gastrointestinal tract can be restored either by a Billroth II gastrojejunal anastomosis or a Roux-en-Y gastrojejunostomy. Each procedure has its advantages and disadvantages.

OBJECTIVE

To determine through a prospective and random clinical trial, the clinical outcome and the endoscopic and histologic alterations of the distal esophagus and the gastric remnant in patients who received a partial distal gastrectomy due to duodenal ulcers and a Billroth II or Roux-en-Y reconstruction.

MATERIAL AND METHODS

In this prospective random trial, a total of 75 patients with duodenal ulcers were included. A bilateral selective vagotomy and partial distal gastrectomy were performed in all patients. A Billroth II or Roux-en-Y 60-cm-long loop was randomly used for reconstruction of the gastrointestinal tract. During the latest follow-up clinical evaluation, upper endoscopy and biopsy samples from the distal esophagus and gastric remnant were obtained.

RESULTS

There was 1 operative mortality and 6 patients had some morbidity. The average follow-up period was 15.5 years (range, 11-21). Patients with Roux-en-Y gastrojejunostomy were significantly more asymptomatic and had greater Visick I grading than patients with Billroth II reconstruction (P < 0.001). In the distal esophagus, endoscopic findings were normal in 90% of the Roux-en-Y group, but only in 51% of the Billroth II group (P < 0.0009). Nearly 25% of the latter group had the appearance of a short-segment Barrett esophagus compared with 3% of the Roux-en-Y group (P < 0.0001). The gastric remnant endoscopic findings were normal in 100% of the Roux-en-Y group and in 18% of the Billroth II group (P < 0.02). Histologic analyses showed similar proportions of normal fundic mucosa and chronic active fundic gastritis. However, chronic atrophic fundic gastritis and intestinal metaplasia were significantly more frequent after Billroth II reconstruction (P < 0.008). Helicobacter pylorus was present in a similar proportion of patients.

CONCLUSIONS

This prospective and random study showed that Roux-en-Y gastrojejunostomy is significantly better than a Billroth II reconstruction in patients with duodenal ulcers, through subjective and objective endoscopic and histologic evaluations during the latest follow-up evaluation.

Diagnosis of small intestinal bacterial overgrowth: the challenges persist!

Small intestinal bacterial overgrowth was originally defined in the context of an overt malabsorption syndrome and diagnostic tests were developed and validated accordingly. More recently, the concept of intestinal contamination with excessive numbers of bacteria, especially those of colonic type, has been extended beyond the bounds of frank maldigestion and malabsorption to explain symptomatology in disorders as diverse as irritable bowel syndrome, celiac sprue and nonalcoholic fatty liver disease. Owing to a lack of consensus with regard to the optimal diagnostic criteria (the 'gold standard') for the diagnosis of bacterial overgrowth, the status of these new concepts is unclear. This review sets out to critically appraise the various diagnostic approaches that have been taken and are currently employed to diagnose small intestinal bacterial overgrowth.

A systematic review of diagnostic tests for small intestinal bacterial overgrowth

BACKGROUND

A growing number of studies seem to suggest that small intestinal bacterial overgrowth (SIBO) is a common clinical problem. Although various techniques are available to make this diagnosis, tradition has accepted small bowel aspirate (>10(5) cfu/ml) as a gold standard. In this systematic review, the validity of culture and other diagnostic testing for SIBO is evaluated.

METHODS

We performed a systematic review of the literature from 1966 to present using electronic databases (PubMed and OVID). Full paper review of those abstracts that fulfilled preset criteria was carried out to evaluate the validity of various tests in diagnosing SIBO. Finally, all papers were evaluated against published standards for studies on diagnostic testing.

RESULTS

Seventy-one papers met the criteria for detailed review. Studies were very heterogeneous with regards to patient populations, test definitions, sample size, and methods in general. Small bowel colony counts appeared elevated in most gastrointestinal diseases compared to controls. The traditional definition of >10(5) cfu/ml was usually indicative of stagnant loop conditions. Although, numerous diagnostic tests were studied, not even culture papers met the quality standards described by Reid et al. Breath testing and other diagnostic testing suffered therefore from the lack of a gold standard against which to validate in addition to the poor quality.

CONCLUSIONS

There is no validated diagnostic test or gold standard for SIBO. In this context, the most practical method to evaluate SIBO in studies at this time would be a test, treat, and outcome technique.

Small intestinal bacterial overgrowth--an incidental finding?

OBJECTIVES

To assess the prevalence of typical clinical features and need for treatment of small intestinal bacterial overgrowth (SIBO) in the elderly.

DESIGN

Random selection of patients, regardless of their nutritional status.

SETTING

Acute admissions ward in the Dept. of Medicine for the Elderly.

PATIENTS

Thirty elderly patients between 68 and 90 years of age.

MEASUREMENTS

Active clinical problems, including the presence of recent weight loss and diarrhea, were recorded. Routine blood tests, including serum vitamin B12, red cell folate, albumin and calcium, and qualitative small bowel bacteriology results, were analyzed. The effect of age on all variables was studied.

RESULTS

Twenty of the 30 small bowel aspirates had proven SIBO, and strict anaerobes were isolated in 15. The mean blood test values did not differ significantly between culture-positive and culture-negative patients. There was no significant correlation between those variables and the total bacterial counts. Of the 20 proven SIBO cases, eight had anemia, five had hypoalbuminemia, five had diarrhea, four complained of recent weight loss, and none had B12 deficiency. Alternative causes other than SIBO were identified for many of these abnormalities. Advancing age correlated significantly with rising counts of small bowel strict anaerobes.

CONCLUSIONS

These data suggest that age may be a predisposing factor in the development of anaerobic overgrowth but that SIBO is a benign entity in the elderly. Contrary to previous recommendations, treatment of this condition is not routinely indicated.

Effect of gastrectomy with either Roux-en-Y or Billroth II anastomosis on small-intestinal function

This prospective study was undertaken in patients scheduled for gastrectomy for peptic ulcer disease to determine the effect of partial gastrectomy with either Roux-en-Y (n = 11) or Billroth II anastomosis (n = 11) on the function of the small intestine. Patients were studied before and at 6 months (blood and small-intestinal function tests) and at 24 months (blood tests) postoperatively. Median postoperative body weights at 6 months (70.5 kg; p less than 0.01) and 12 months (70.3 kg; NS) were lower than preoperatively (73.0 kg). Haemoglobin concentrations at 6 months (8.9 mM; p less than 0.01) and at 24 months (9.1 mM; p less than 0.05) were also significantly reduced compared with the preoperative value (9.5 mM). However, neither at 6 nor at 24 months postoperatively were there significant changes for serum iron, iron saturation, folic acid, vitamin B12, protein, albumin, alkaline phosphatase, and calcium concentrations. Whereas no significant deterioration of the absorption of D-xylose and vitamin B12 or of faecal fat excretion was observed, the orocoecal transit time was significantly shortened from 98 to 50 min (p less than 0.01), the expiratory hydrogen excretion after a 50-g oral glucose load was significantly increased from 8 to 54 ppm (p less than 0.01), as was indicanuria from 257 to 368 mumol/24 h (p less than 0.01). Apart from a lower serum iron concentration and iron saturation index in the Roux-en-Y patients 6 months postoperatively (p less than 0.05), no significant differences between the two types of anastomosis were observed. It is therefore concluded that both in patients with Roux-en-Y and in those with Billroth II anastomosis most abnormalities observed after gastrectomy are secondary to an accelerated small-intestinal transit.

Treatment of small intestine bacterial overgrowth with rifaximin, a non-absorbable rifamycin

In twelve patients affected by small bowel bacterial overgrowth, diagnosed by means of the lactulose hydrogen breath test, the therapeutic efficacy of a non-absorbable derivative of rifamycin, rifaximin, was evaluated. This study showed that this drug has a satisfactory therapeutic efficacy in contaminated small bowel syndrome and, at the doses tested, is free of side-effects.

The human intestinal microflora

The major host defense mechanisms against bacterial overgrowth in the small bowel are the normal propulsive activity of the bowel itself and gastric acid secretion. Microbial interactions are a major factor in regulating the indigenous bacterial flora. Studies of the bacterial enzymes of the gut suggest that changes in diet may lead to marked changes in the colonic flora. Antibiotics affect the composition of the colonic microflora. The microflora also influence the degradation of mucin, the conversion of urobilin to urobilinogen, of cholesterol to coprostanol, and the production of short chain fatty acids. Current interests are focused on the bacterial flora of tropical sprue, the role of bacteria in colorectal cancer, and the involvement of intestinal microflora in the enterohepatic circulation of sex steroid hormones.

Potential hazards of hypochlorhydria in the treatment of peptic ulcer

The introduction of ulcer-healing drugs that do not induce hypochlorhydria--the main aim of therapy thus far--has led to the consideration of the possible disadvantages of acid secretion inhibition. Potential dangers are that micro-organisms destroyed by the normal stomach survive and proliferate in the stomach and small intestine. The incidence of gastric cancer is higher in pernicious anemia and after partial gastrectomy. It has been suggested that the intragastric bacteria may convert dietary nitrate into nitrite that may then be nitrosated to carcinogenic N-nitroso compounds. The third potential hazard is the development of stagnant loop syndrome in patients treated with H2 antagonists. In a double-blind randomised trial of colloidal bismuth subcitrate (CBS) versus cimetidine in duodenal ulcer, gastric juice was aspirated for pH measurement. There was a significant increase in the total number of bacteria isolated during cimetidine treatment (P less than 0.01) and an increase in nitrate-reducing organisms (P less than 0.05), but no change in the CBS group. It is concluded that there may be advantages in using ulcer-healing drugs that do not reduce H+ concentration.

Diagnosis of bacterial overgrowth of the small intestine. Comparison of the 14C-D-xylose breath test and jejunal cultures in 60 patients

Sixty consecutive patients suspected of having bacterial overgrowth of the small intestine (BOG) had aerobic and anaerobic bacterial cultures made of fasting upper jejunal fluid and also a 14C-D-xylose breath test (XBT). Culture-proven BOG was present in 23 patients. In another 15 patients the presence of BOG was ruled out (diagnoses: irritable bowel syndrome, 8; chronic diarrhoea, 6; and lactose malabsorption, 1). These patients were used as controls. The other 22 of the 60 patients could not be placed in either group owing to the presence of factors known to predispose for BOG; none of them had abnormal jejunal cultures, but several had strong clinical suspicion of BOG. An abnormal XBT, defined as values exceeding upper 90% confidence limits (upper range) of the 15 patient control values within a 4-h period, was observed with the following frequencies in the 23 patients with BOG: after 60 min, 35%; after 120 min, 44%; after 180 min, 61%; and after 240 min, 65%. An abnormal XBT was observed in 41% of the 22 patients with normal jejunal cultures but with predisposition for, and clinical suspicion of, BOG. It is concluded that, compared with a relevant control material, the XBT tends to be rather insensitive and that a negative outcome of jejunal cultures is inadequate to exclude the presence of BOG.

The hydrogen (H2) breath test. Sampling methods and the influence of dietary fibre on fasting level

Three end-expiratory breath hydrogen (H2) sampling methods were compared in a patient group (n = 12) and a laboratory staff group (n = 12) on two separate occasions. H2 samples obtained with each method showed significantly different concentrations (p less than 0.001) but no significant differences in coefficient of variation when individual triplicate samples were evaluated. There was a high correlation between the breath H2 concentrations obtained by the three methods (r = 0.93-0.96). Fasting breath H2 values after an overnight fast and an unrestricted diet the day before the investigation were compared with values obtained after an overnight fast and a low-fibre diet the day before the test in two patient groups (n = 39 and 39) with a comparable distribution of diagnoses and in one group of healthy volunteers (n = 17). Fasting breath H2 concentrations were significantly lower after a low-fibre diet in the patient groups (p less than 0.005) and in healthy volunteers (p less than 0.02). We conclude that each of the three end-expiratory sampling methods can be chosen for use in H2 breath tests depending on suitability and convenience and that a low-fibre diet the day before the H2 breath test lowers fasting breath H2 concentration.

Hydrogen (H2) breath test and gastric bacteria in acid-secreting subjects and in achlorhydric and postgastrectomy patients before and after antimicrobial treatment

Sixteen patients with pentagastrin-fast achlorhydria and 12 patients who had undergone Billroth II gastrectomy (at least 3 years previously) were compared with 10 acid-secreting volunteers and 13 patients with endoscopically proven peptic disease. The concentration and type of gastric bacteria were analysed in achlorhydrics, Billroth II patients, and patients with peptic disease. A 6-h hydrogen (H2) breath test after a standardized meal was performed in all subjects. The mean concentration of gastric bacteria was significantly higher in achlorhydrics and Billroth II patients than in patients with peptic disease. End-expiratory H2 excretion was elevated in achlorhydrics and Billroth II patients to levels significantly exceeding those of acid-secreting volunteers and patients with peptic disease. In achlorhydrics, total bacterial concentration in gastric juice was correlated to H2 excretion between 60 and 180 min after the meal. Treatment of achlorhydric and postgastrectomy patients with trimethoprim/sulphamethoxazole lowered H2 breath concentrations in both groups and reduced symptoms in achlorhydrics. Elevated end-expiratory H2 levels after a test meal indicate upper gastrointestinal bacterial overgrowth in achlorhydrics and in postgastrectomy patients.

Bacterial overgrowth

Different aspects of bacterial overgrowth in the small intestine are reviewed. The pathophysiological mechanisms involving both bacterial metabolism of dietary components and secretions and effects on the mucosal cells are discussed in more detail. The current therapy, surgical, medical and supportive, is outlined.

Bacterial overgrowth as a consequence of reduced gastric acidity

Reduction in acid secretion in atrophic gastritis allows bacterial colonization of the stomach, most extremely in achlorhydric patients with pernicious anaemia, in whom overgrowth may cause nitrate reduction and formation of potentially carcinogenic N-nitroso compounds. Subsequent bacterial contamination of the upper small intestine can induce mucosal damage and malabsorption. The situation is similar after gastrectomy. In achlorhydria and after gastrectomy, the risk of gastric cancer is increased. There is controversy as to the risks of long-term treatment with H2-receptor antagonists. Increase in nitrate-reducing bacteria, nitrite and N-nitrosamine have been observed in patients by some investigators but not in volunteers and patients by others. Bacterial concentrations after cimetidine are inversely related to pretreatment acid secretory capacity. Demonstration of increased mutagenicity of gastric juice after H2-receptor antagonists gives grounds for caution. Drastic acid reduction may in future be reserved for short-term and intermittent treatment and mild or moderate reduction for long-term treatment of peptic ulcer and ulcer prevention.