Intestinal absorption in the "contaminated small-bowel syndrome"

Relationship among Chinese herb polysaccharide (CHP), gut microbiota, and chronic diarrhea and impact of CHP on chronic diarrhea

Chronic diarrhea, including diarrhea-predominant irritable bowel syndrome (IBS-D), osmotic diarrhea, bile acid diarrhea, and antibiotic-associated diarrhea, is a common problem which is highly associated with disorders of the gut microbiota composition such as small intestinal bacterial overgrowth (SIBO) and so on. A growing number of studies have supported the view that Chinese herbal formula alleviates the symptoms of diarrhea by modulating the fecal microbiota. Chinese herbal polysaccharides (CHPs) are natural polymers composed of monosaccharides that are widely found in Chinese herbs and function as important active ingredients. Commensal gut microbiota has an extensive capacity to utilize CHPs and play a vital role in degrading polysaccharides into short-chain fatty acids (SCFAs). Many CHPs, as prebiotics, have an antidiarrheal role to promote the growth of beneficial bacteria and inhibit the colonization of pathogenic bacteria. This review systematically summarizes the relationship among gut microbiota, chronic diarrhea, and CHPs as well as recent progress on the impacts of CHPs on the gut microbiota and recent advances on the possible role of CHPs in chronic diarrhea.

Small Intestinal Bacterial Overgrowth-Pathophysiology and Its Implications for Definition and Management

The concept of small intestinal bacterial overgrowth (SIBO) arose in the context of maldigestion and malabsorption among patients with obvious risk factors that permitted the small bowel to be colonized by potentially injurious colonic microbiota. Such colonization resulted in clinical signs, symptoms, and laboratory abnormalities that were explicable within a coherent pathophysiological framework. Coincident with advances in medical science, diagnostic testing evolved from small bowel culture to breath tests and on to next-generation, culture-independent microbial analytics. The advent and ready availability of breath tests generated a dramatic expansion in both the rate of diagnosis of SIBO and the range of associated gastrointestinal and nongastrointestinal clinical scenarios. However, issues with the specificity of these same breath tests have clouded their interpretation and aroused some skepticism regarding the role of SIBO in this expanded clinical repertoire. Furthermore, the pathophysiological plausibility that underpins SIBO as a cause of maldigestion/malabsorption is lacking in regard to its purported role in irritable bowel syndrome, for example. One hopes that the application of an ever-expanding armamentarium of modern molecular microbiology to the human small intestinal microbiome in both health and disease will ultimately resolve this impasse and provide an objective basis for the diagnosis of SIBO.

Small intestinal bacterial overgrowth in patients with chronic pancreatitis

GOALS

To assess the prevalence of small intestinal bacterial overgrowth (SIBO) in chronic pancreatitis (CP), and analyze factors related with SIBO in CP.

BACKGROUND

SIBO is to be considered a factor that worsens symptoms and nutritional status in patients with CP. However, the few studies evaluating the rate of SIBO in CP patients used nonuniform and nonstandardized procedures, and reported a wide range of positivity (0% to 92%). Those studies often investigated CP patients with previous resection surgery (cause of SIBO per se).

STUDY

CP patients and controls evaluated for SIBO by the H2 glucose breath test with a standard protocol. For CP patients, the relationship between test results, abdominal symptoms, and clinical and biochemical variables was analyzed.

RESULTS

A total of 43 CP patients and 43 controls were enrolled. Of the CP patients, 8 had advanced disease (defined by M-ANNHEIM index) and none had undergone previous surgery. The glucose breath test positivity rate was higher in the CP patients than in the controls (21% vs. 14%), albeit without a significant difference (P=0.57). Mean fasting H2 excretion and mean H2 excretion at 120 minutes also had a trend toward higher levels in CP patients. There were no clinical differences between CP patients with or without SIBO, but there were nutritional differences for lower levels of vitamin D and higher levels of folate in these patients with SIBO.

CONCLUSIONS

Our findings suggest that SIBO is not uncommon in uncomplicated CP patients. The lack of a significant difference compared with controls might be due to the study being underpowered. SIBO in CP patients does not seem to be related to peculiar clinical features, but it might affect nutritional status.

Critical appraisal of the management of severe malnutrition: 3. Complications

The high case-fatality of severe malnutrition is due to infections, dehydration, electrolyte disturbances and heart failure. We focus on the evidence about managing these complications of severe malnutrition. Signs of circulatory collapse in severely malnourished children should be treated with intravenous or bone marrow infusion of Ringer's lactate with additional dextrose and potassium at a rate 20-40 mL/kg fast with close monitoring of vital signs. Recommendations for slow or restricted fluids in the face of shock are unsafe, and hypotonic or maintenance solutions must be avoided to prevent hyponatraemia. However, the evidence that severely malnourished children do not tolerate excessive fluid administration is good, so caution must be exercised with regards to fluids in the initial phase of treatment. There is also good evidence that wide spectrum antibiotics need to be given empirically for severe malnutrition to prevent the otherwise unavoidable early mortality. There is a need for improved protocols for tuberculosis diagnosis, HIV management and treatment of infants under 6 months with severe malnutrition. The contribution of environmental enteropathy to poor growth and nutrition during the weaning period means that there should be more priority on improving environmental health, particularly better hygiene and less overcrowding. A T-cell mediated enteropathy contributes to growth failure and malnutrition, and it is related to environmental contamination of enteric organisms in the weaning period rather than allergic responses.

Use of an orally administered combined sugar solution to evaluate intestinal absorption and permeability in cats

OBJECTIVE

To evaluate intestinal permeability and absorption in healthy cats in association with diet and normal intestinal microflora.

ANIMALS

6 healthy domestic shorthair cats.

PROCEDURE

A sugar solution containing D-xylose, 30-methyl-D-glucose, L-rhamnose, lactulose, and 51Cr-EDTA was administered intragastrically to healthy cats, and urinary excretion of ingested sugars was determined 5 hours after administration. After the same cats had received metronidazole for 1 month, the study was repeated. A final study was performed while cats were maintained on a new diet differing in composition and processing.

RESULTS

Lactulose-to-rhamnose ratios, reflecting intestinal permeability, were higher in cats, compared with values for humans or dogs, and values obtained before and after metronidazole administration (mean +/- SEM; before, 0.40 +/- 0.08; after, 0.45 +/- 0.09) were not significantly different. Intestinal absorption also was unaltered after antibiotic administration, and the xylose-to-glucose ratio was 0.70 +/- 0.03 before and 0.71 +/- 0.06 after metronidazole administration. Sugar recovery did not differ significantly while cats were maintained on canned or dry food.

CONCLUSIONS AND CLINICAL RELEVANCE

Reference ranges were established for the percentage urinary recovery of orally administered D-xylose, 3-0-methyl-D-glucose, L-rhamnose, lactulose, and 51Cr-EDTA obtained after 5 hours in healthy cats. The intestines of cats appear to be more permeable than those of other species, although the normal bacterial microflora does not appear to influence the integrity or function of the feline intestine, because values obtained for the measured variables before or after antibiotic administration were not significantly different. In addition, differences were not detected when the diet was completely altered.

Asymptomatic environmental enteropathy among slum-dwelling infants

OBJECTIVE

We documented asymptomatic environmental enteropathy, which may occur in low socioeconomic populations, and which is manifested by bacterial proliferation in the upper portions of the small bowel and by alterations in the digestive-absorptive capacity.

DESIGN

Forty asymptomatic infants (< 1 year) of the Cidade Leonor slum in São Paulo, Brazil, were investigated for digestive-absorptive function, bacterial proliferation in the small bowel lumen, and jejunal morphology. They were compared with a control group of 8 well-nourished children from economically sound families.

RESULTS

Mean value of the D-xylose absorption test in the slum infants 21.0 +/- 10.0 mg%) was significantly lower than in controls (46.0 +/- 13.8 mg%) (p < 0.001). Colonic bacterial proliferation in the small bowel was identified in 25 (62.5%) of slum-dwelling infants. Grade II villous atrophy with inflammatory infiltration in the lamina propria was the most frequent alteration found.

CONCLUSION

These data show that alterations in the microecology, function and morphology of the small intestine can occur even in the absence of diarrhea. Therefore, the absence of symptoms does not necessarily imply a healthy well-being among children living in a slum.

Altered distribution of MHC class II antigens on enterocytes during acute small bowel allograft rejection in rats

Class II major histocompatibility complex (MHC) antigen induction was investigated on enterocytes of heterotopic rat small bowel allografts in the Lewis-Brown Norway strain combination and on isografts in the Lewis-Lewis strain combination. Ia antigens were detected with monoclonal antibodies using an immunoperoxidase technique. Generally, MHC class II antigens were not exhibited in the isografted group, with the exception of two long-term isografts that presented the same pattern as normal small bowel. In these cases, Ia was expressed in a patchy distribution predominantly in the villi, and only very few enterocytes stained positive in Lieberkühn's crypts. Allografted rats showed a typical pattern of Ia expression on the enterocytes during the rejection course. The initial expression was confined to the crypts, indicating a very early stage of rejection when compared to histological findings. More advanced stages of rejection were accompanied by increasing Ia biosynthesis in the crypts and Ia expression by the epithelium lining the villi. Cyclosporin (CyA) was not able to fully inhibit MHC class II antigen expression; however, the appearance of Ia was delayed.

Review: pathophysiology of diarrhea caused by bacterial overgrowth of the small intestine

The bacterial overgrowth syndrome constitutes an intestinal problem involving alterations in motility and injury to the brush border and mucosa. The overgrowth of bacteria also causes secretion, malabsorption, and maldigestion. These alterations result in a clinical syndrome that manifests itself as weight loss, malabsorption of specific nutrients, and (usually) diarrhea. There are known causes of bacterial overgrowth, such as intestinal diverticuli or surgical procedures involving a vagotomy, but in our experience most cases remain idiopathic. This review evaluates the mechanisms of bacterial overgrowth, as currently understood, and specifically addresses the known causes of diarrhea that results from bacterial contamination of the small intestine.

Intestinal uptake of bile acids: effect of external abdominal irradiation

Abdominal irradiation has recently been shown to influence the uptake of hexoses, amino acids, fatty acids and cholesterol into the jejunum of rats. The present studies were undertaken with a previously validated in vitro technique to determine the effect of abdominal irradiation from a cesium 137 source on the rates of uptake of six bile acids into the jejunum, ileum, and colon. In the ileum of control rats, there were marked differences in the value of the apparent Michaelis constant (Km*), maximal transport rate (Jdm), and apparent passive permeability coefficient (Pd*) between cholic (C), glycocholic (GC), taurocholic (TC), chenodeoxycholic (CDC), and glycochenodeoxycholic (GCDC), and deoxycholic (DC) acid. The Km* for each bile acid except DC was lower three and 14 days after 600 rad, whereas the Jdm for GC fell, but rose for TC, CDC, GCDC and DC and was unchanged for C. The Pd* rose for C, GC, and DC, fell for TC and CDC, but remained unchanged for GCDC 14 days after irradiation. After 600 rad the value of Pd* in the colon was increased at day 3 and 14 for CDC and GCDC, but was unchanged for GC and TC and was decreased for C. The uptake of bile acids was also affected by 300 rad and by 900 rad, but the direction and magnitude of the change was influenced by the intestinal site, the dose of irradiation, and the type of bile acid. The results show that: 1) there likely are multiple ileal carriers for bile acids; 2) abdominal irradiation has a variable effect on these carriers; 3) the passive permeability to bile acids varies with the bile acid and with the site along the intestine; and 4) abdominal irradiation is associated with a rise in the colonic permeability to only some bile acids.

Bile acid deconjugation and attachment of chicken gut bacteria: their possible role in growth depression

Bacteria isolated from the chicken gut were tested for their ability to deconjugate bile acids and attach to chicken epithelial cells (crop squamous cells and duodenal brush borders). Clostridium perfringens, streptococci and some of the bifidobacteria and lactobacilli were able to deconjugate all 4 substrates whereas the bacteroides deconjugated only the taurine conjugates and the coliforms were completely inactive. None of the strains of Escherichia coli or streptococci attached to squamous cells, but the anaerogenic coliform, the strain of Klebsiella aerogenes and the lactobacilli did show attachment. Attachment to brush borders was obtained with the anaerogenic coliforms, K. aerogenes, 2 out of 5 of the lactobacilli, and 4 out of 9 of the streptococci, but none of the strains of E. coli.

Mechanisms of malabsorption in the "Contaminated Small-Bowel syndrome"

The mucosa of the upper small intestine in humans is repeatedly exposed to potentially harmful environmental influences: infective, toxic and antigenic. One of the most significant manifestations of the control over environmental risks is how the upper intestinal milieu is kept relatively sterile and pathogen-free despite constant exposure to a potentially hostile and pathogen-ridden environment. This control is lost in the so-called "Contaminated Small-Bowel Syndrome" when profuse numbers of bacteria contaminate the contents of the upper bowel. This can occur in a vast array of clinical situations ranging from infancy to old age. The consequences of upper intestinal bacterial overgrowth are very diverse. The mechanisms causing diarrhoea and malabsorption in this syndrome illustrate facets of pathophysiology of many inter-relating processes of intestinal digestion and absorption.

Long term nutritional effects of extensive resection of the small intestine

A nutritional study was carried out on 36 patients several years after major resection of the small intestine (100 to 330 cm). Thirty one of these resections had been performed for Crohn's disease and only patients who had been clinically free of disease for more than one year were studied. The group of patients were 15% below their ideal weight. Total body fat was 24% below the predicted normal value and total body protein was 10% below. Although deficiencies of iron, vitamin B12 and folic acid were frequently found, only six patients were anaemic. Other vitamin and mineral deficiencies were common. Despite these abnormalities, two thirds of the patients were engaged in their normal occupation full time and were subjectively well. The others who did not regain their normal capacity for work, had a greater nutritional deficit and a shorter length of remaining small intestine. It is concluded that nutritional deficiencies are common following extensive small bowel resection and all patients need regular follow up and appropriate vitamin and mineral supplementation. However, major disturbances of body composition and severe protein energy malnutrition with a reduced capacity for work are restricted to a small number of patients with very short lengths of remaining small intestine.

[The effect of unconjugated bile salts on the intestinal absorption of electrolytes and water in the proximal jejunum. Studies in conscious rats (author's transl)]

With an in vivo-perfusion-technique the influence of unconjugated bile salts (cholate, desoxycholate) on the net electrolyte and volume absorption is studied in the jejunum of conscious rats. The applied doses correspond to physiological concentrations in the intestine of rats. Control experiments were performed in the same animal. Cholate and desoxycholate diminish the net electrolyte and volume absorption resp. cause a net secretion. The effects are largely reversible. The extent of net volume absorption depends on the applied dose of each bile salt. The possible mode of action of unconjugated bile salts on the electrolyte and water absorption in the small intestine is discussed.

Enterotoxigenicity of colonising coliform bacteria in tropical sprue and blind-loop syndrome

The enterotoxigenicity of strains of Klebsiella pneumoniae, Enterobacter cloacae, and Escherichia coli, which represented the predominant coliform species isolated from the jejunum of 12 patients with tropical sprue and 5 with the blind-loop syndrome, was quantitatively assessed in terms of the ability of toxin preparations to induce water secretion as assayed by in-vivo perfusion in the rat jejunum. All 12 patients with sprue harboured 1 or more highly toxigenic strains--14 of the 16 strains isolated from this group produced heat-labile and/or heat-stable toxins which were as potent as toxins derived from strains isolated from persons with acute diarrhoea and documented as toxigenic. None of the 9 strains isolated from patients with the blind-loop syndrome produced potent toxins. This difference between the coliform bacteria in sprue and the blind-loop syndrome probably accounts, at least partly, for the different intestinal response in these two disorders to contamination by these organisms.

Functional, biochemical and morphological alterations in the intestines of rats with an experimental blind-loop syndrome

In rat self-filling blind loops and in the contiguous regions of the intestinal tract, considerable functional impairment, accompanied by pronounced morphological transformations of the mucosa, has been observed. The histological alterations consist of mucosal hypertrophy and a reduction in the villus height: crypt length ratio, which is indicative of a hyper-regenerative change. Various enzyme activities of the epithelial cells are reduced and the absorption otinal juices is greatly altered in favour of the free acids. Two mec,anisms have 0een dicids, or meta0olites from bacterial degradation, on the absorptive epithelium; 2. Reduced cellular maturity in response to the effect of bile acids and/or bacteria on the lifespan of the cells.

Effect of stasis on intestinal enzyme activities

Activities of the small intestinal mucosal enzymes lactase, sucrase, maltase, alkaline phosphatase and N-acetyl-beta-glucosaminidase were studied in rats with surgically-induced upper intestinal stasis and in control animals. The first four are brush border enzymes, the latter a lysosomal enzyme. There was a reduction in the activities of all enzymes in the operated animals. The change lining was significant and most marked in mucosa the blind loop and gut distal to it; areas in which there is gross bacterial overgrowth and excessive levels of intraluminal deconjugated bile salts. The significance of these findings in relation to malabsorption consequent on bacterial contamination of the upper gut is uncertain and requires further study.

Clinical and laboratory study of postvagotomy diarrhoea

Thirty-two patients with diarrhoea, on average four years following truncal vagotomy and drainage, were studied. A comparison was made with 24 patients without postvagotomy diarrhoea. The incidence of bacterial colonization of the upper small intestine was no different in the two groups, though patients with a gastroenterostomy had a significantly higher incidence than those with a pyloroplasty. There was a higher incidence of ;anaerobic colonization' in patients with diarrhoea, but statistical significance was not reached. Colonization was associated with significantly lower levels of gastric acid secretion. Though 13 patients with diarrhoea had an abnormal faecal fat excretion, no correlation could be found between this and the severity of the diarrhoea or bacterial colonization, either with an anaerobic or a coliform type flora.In patients with diarrhoea, no small intestinal mucosal abnormality was detected, the mean haematological and serum biochemistry values were within normal limits, and the body weight was similar to that before operation. Two patients with diarrhoea had abnormal haematological values five years following vagotomy and gastroenterostomy in association with ;anaerobic colonization' of the upper small intestine. As the incidence of haematological abnormalities after gastric surgery increases with time, colonized patients might merit particularly close clinical observation.

The effect of vagotomy and drainage on the small bowel flora

The incidence of small intestinal colonization in unoperated duodenal ulcer patients was low and similar to that in the normal population. The majority of patients seven to 10 days following truncal vagotomy and drainage were colonized whereas none of a control group of patients following simple closure of a perforated duodenal ulcer was colonized. In patients with pyloroplasty, this high incidence fell to control levels on average 18 months postoperatively, but in patients with a gastro-jejunostomy, the incidence remained raised probably due to the presence of the afferent loop. Only two patients developed episodic diarrhoea and there was no obvious association with small bowel colonization.

The effects of different bile salts on the absorption of fluid, electrolytes, and monosaccharides in the small intestine of the rat in vivo

The effects of different bile salts on the absorption of fluid, electrolytes, and monosaccharides have been investigated in the rat small intestine in vivo. In the jejunum, deoxycholate (1 mM) impaired absorption of water and potassium, but not of sodium or glucose; at higher concentrations (2.5 and 5 mM) secretion of fluid and electrolytes occurred, and glucose and fructose absorption was impaired. By contrast, in the ileum, 1 mM deoxycholate failed to inhibit fluid and electrolyte absorption, and a concentration of 10 mM was required completely to inhibit absorption; secretion was not observed in the ileum. Chenodeoxycholate (5 mM) produced a similar effect to deoxycholate on fluid and electrolyte absorption in both jejunum and ileum, but taurocholate (5 mM) and taurodeoxycholate (5 mM) were ineffective.In jejunum, cholate, taurocholate, and taurodeoxycholate, each at a concentration of 5 mM, were less effective inhibitors of glucose transport than deoxycholate; chenodeoxycholate failed to inhibit glucose absorption. Deoxycholate produced histological damage at 5 mM, but not at lower concentrations. The functional and structural abnormalities were shown to be reversible phenomena. These findings may be relevant to the pathogenesis of diarrhoea in patients with bacterial overgrowth in the small intestine.