The role of altered bile acid metabolism in the steatorrhea of experimental blind loop

Self-reinoculation with fecal flora changes microbiota density and composition leading to an altered bile-acid profile in the mouse small intestine

BACKGROUND

The upper gastrointestinal tract plays a prominent role in human physiology as the primary site for enzymatic digestion and nutrient absorption, immune sampling, and drug uptake. Alterations to the small intestine microbiome have been implicated in various human diseases, such as non-alcoholic steatohepatitis and inflammatory bowel conditions. Yet, the physiological and functional roles of the small intestine microbiota in humans remain poorly characterized because of the complexities associated with its sampling. Rodent models are used extensively in microbiome research and enable the spatial, temporal, compositional, and functional interrogation of the gastrointestinal microbiota and its effects on the host physiology and disease phenotype. Classical, culture-based studies have documented that fecal microbial self-reinoculation (via coprophagy) affects the composition and abundance of microbes in the murine proximal gastrointestinal tract. This pervasive self-reinoculation behavior could be a particularly relevant study factor when investigating small intestine microbiota. Modern microbiome studies either do not take self-reinoculation into account, or assume that approaches such as single housing mice or housing on wire mesh floors eliminate it. These assumptions have not been rigorously tested with modern tools. Here, we used quantitative 16S rRNA gene amplicon sequencing, quantitative microbial functional gene content inference, and metabolomic analyses of bile acids to evaluate the effects of self-reinoculation on microbial loads, composition, and function in the murine upper gastrointestinal tract.

RESULTS

In coprophagic mice, continuous self-exposure to the fecal flora had substantial quantitative and qualitative effects on the upper gastrointestinal microbiome. These differences in microbial abundance and community composition were associated with an altered profile of the small intestine bile acid pool, and, importantly, could not be inferred from analyzing large intestine or stool samples. Overall, the patterns observed in the small intestine of non-coprophagic mice (reduced total microbial load, low abundance of anaerobic microbiota, and bile acids predominantly in the conjugated form) resemble those typically seen in the human small intestine.

CONCLUSIONS

Future studies need to take self-reinoculation into account when using mouse models to evaluate gastrointestinal microbial colonization and function in relation to xenobiotic transformation and pharmacokinetics or in the context of physiological states and diseases linked to small intestine microbiome and to small intestine dysbiosis. Video abstract.

Enteral Nutrition With an Enteral Formula Containing Egg Yolk Lecithin After Percutaneous Endoscopic Gastrostomy: A Case Series

The occurrence of diarrhea at the beginning of enteral nutrition complicates the continuation of enteral nutrition. Recently, studies in Japan indicated that diarrhea could be improved by changing the enteral formula to one that is emulsified with egg yolk lecithin. In this study, we administered the enteral formula K-2S plus, which is emulsified with egg yolk lecithin, to 15 patients (four men and 11 women; mean age, 79.9 ± 2.0 years) after they had undergone a percutaneous endoscopic gastrostomy (PEG) to prevent the occurrence of diarrhea related to enteral nutrition. Two days after the PEG, the patients would receive 200 mL K-2S plus intermittently three times daily; thereafter, the amount of K-2S plus was increased according to the patient’s condition. The administration rate was scheduled as 200 mL/h when 200 mL were administered at one time. For ≥ 300 mL, the scheduled administration rate was 300 mL/h. When we administered K-2S plus at the beginning of enteral nutrition after the PEG, the dose of the enteral formula could be increased without any occurrence of diarrhea or vomiting. Five patients had received intravenous nutrition before the PEG; thus, we were concerned about diarrhea in these patients. In conclusion, an enteral formula emulsified with egg yolk lecithin may be safely used at the time of enteral nutrition initiation without causing diarrhea.

Small Intestinal Bacterial Overgrowth: Nutritional Implications, Diagnosis, and Management

Small intestinal bacterial overgrowth (SIBO), characterized by the presence of excessive bacteria in the small intestine, is typically described as a malabsorptive syndrome occurring in the context of gut stasis syndromes. SIBO is now considered to be a disorder associated with diverse clinical conditions without classic risk factors for SIBO and a cause of several nonspecific gastrointestinal and nongastrointestinal symptoms. Because there is currently no gold standard for diagnosing SIBO, its prevalence and role in the pathogenesis of other diseases remain uncertain; as does optimal treatment of patients with relapsing symptoms.

Enteral Formula Containing Egg Yolk Lecithin Improves Diarrhea

Diarrhea often occurs during enteral nutrition. Recently, several reports showed that diarrhea improves by adding egg yolk lecithin, an emulsifier, in an enteral formula. Therefore, we evaluated if this combination could improve diarrhea outcomes. We retrospectively investigated the inhibitory effects on watery stools by replacing a polymeric fomula with that containing egg yolk lecithin. Then, we investigated the emulsion stability in vitro. Next, we examined the lipid absorption using different emulsifiers among bile duct-ligated rats and assessed whether egg yolk lecithin, medium-chain triglyceride, and dietary fiber can improve diarrhea outcomes in a rat model of short bowel syndrome. Stool consistency or frequency improved on the day after using the aforementioned combination in 13/14 patients. Average particle size of the egg yolk lecithin emulsifier did not change by adding artificial gastric juice, whereas that of soy lecithin and synthetic emulsifiers increased. Serum triglyceride concentrations were significantly higher in the egg yolk lecithin group compared with the soybean lecithin and synthetic emulsifier groups in bile duct-ligated rats. In rats with short bowels, the fecal consistency was a significant looser the dietary fiber (+) group than the egg yolk lecithin (+) groups from day 6 of test meal feedings. The fecal consistency was also a significant looser the egg yolk lecithin (-) group than the egg yolk lecithin (+) groups from day 4 of test meal feeding. The fecal consistency was no significant difference between the medium-chain triglycerides (-) and egg yolk lecithin (+) groups. Enteral formula emulsified with egg yolk lecithin promotes lipid absorption by preventing the destruction of emulsified substances by gastric acid. This enteral formula improved diarrhea and should reduce the burden on patients and healthcare workers.

Long-term follow-up after ileocaecal continent cutaneous urinary diversion (Mainz I pouch): A retrospective study of a monocentric experience

OBJECTIVE

To assess the long-term follow-up after ileocaecal continent cutaneous reservoir (ICCR) and to review the late complications.

PATIENTS AND METHODS

In all, 756 patients underwent an ICCR in our department, with long-term follow-up data available in 50 patients. The inclusion criterion was ICCR regardless of the indication and the exclusion criteria were orthotopic neobladder or other continent urinary diversions not performed with the ileocaecum. Patients were followed to record primary outcomes and late complications. Complications were stratified according to the Clavien-Dindo classification.

RESULTS

The mean patient age was 44 years and pelvic malignancies were the first indication for urinary diversion. The mean (range) follow-up was 19 (9-36) years. A stoma stenosis was the most frequent outlet-related complication requiring re-intervention, followed by ischaemic outlet degeneration, and stoma incontinence. Six renal units (RUs) developed obstruction at the anastomotic site and were managed by open surgery. Three RUs had to be removed due to deterioration. A dederivation was necessary in three patients (6%).

CONCLUSION

The ICCR is a safe and established technique when an orthotopic pouch is impossible. The long-term follow-up shows acceptable complication rates and satisfactory continence conditions. However, large population studies are necessary to confirm this observation.

Metabolic consequences after urinary diversion

Metabolic disturbances are well-known, but sometimes neglected immediate consequences or late sequelae following urinary diversion (UD) using bowel segments. Whereas subclinical disturbances appear to be quite common, clinically relevant metabolic complications, however, are rare. Exclusion of bowel segments for UD results in loss of absorptive surface for its physiological function. Previous studies demonstrated that at least some of the absorptive and secreting properties of the bowel are preserved when exposed to urine. For each bowel segment typical consequences and complications have been reported. The use of ileal and/or colonic segments may result in hyperchloremic metabolic acidosis, which can be prevented if prophylactic treatment with alkali supplementation is started early. The resection of ileal segments may be responsible for malabsorption of vitamin B12 and bile acids with subsequent neurological and hematological late sequelae as well as potential worsening of the patient's bowel habits. Hence, careful patient and procedure selection, meticulous long-term follow-up, and prophylactic treatment of subclinical acidosis is of paramount importance in the prevention of true metabolic complications.

Review article: small intestinal bacterial overgrowth--prevalence, clinical features, current and developing diagnostic tests, and treatment

BACKGROUND

The symptoms and signs of small intestinal bacterial overgrowth (SIBO) are often identical to a variety of diseases and can lead to diagnostic confusion.

AIMS

To review the diagnostic options for SIBO and present new investigative options for the condition.

METHODS

A literature search was performed on MEDLINE, EMBASE and Web of Science for English articles and abstracts. Search terms included free text words and combinations of the following terms 'small intestinal bacterial overgrowth', 'small bowel bacterial overgrowth', 'diagnostic tests', 'treatment', 'antibiotics', 'probiotics', 'metabonomics', 'proton nuclear magnetic resonance spectroscopy', 'electronic nose' and 'field asymmetric ion mobility spectrometry'.

RESULTS

All of the available methods to test for SIBO have inherent limitations and no 'gold-standard' diagnostic test for the condition exists. Accurate diagnosis of SIBO requires identification of bacterial species growing inappropriately within the small intestine and symptom response to antibiotics. Proton nuclear magnetic resonance spectroscopy, electronic nose technology and/or field asymmetric ion mobility spectrometry may represent better investigative options for the condition.

CONCLUSIONS

Novel diagnostic options are needed to supplement or replace available tests.

[Metabolic long-term complications after urinary diversion]

Metabolic long-term complications and consequences after urinary diversion are somewhat neglected. Subclinical metabolic disturbances are quite common; however, complications are rare. The absorptive surface of the bowel segment is lost for the physiological function of the gastrointestinal tract. Some studies demonstrated that at least some of the absorbent and secreting properties of the bowel are preserved if exposed to urine. For each bowel segment typical complications are reported. Using ileal and/or colon segments, hyperchloremic metabolic acidosis may occur. Studies demonstrated that metabolic effects are not as severe as suspected and could be prevented if a prophylactic treatment is started early.The resection of ileal segments is responsible for malabsorption of vitamin B(12) and bile acid; when using colonic segments, electrolyte disturbances are more common. Careful patient selection, meticulous follow-up and prophylactic treatment are crucial to prevent metabolic complications.

Bladder augmentation and urinary diversion in patients with neurogenic bladder: non-surgical considerations

Segments from almost all parts of the bowel have been used for urinary diversion. As a result, the available absorptive surface area of the bowel is reduced, and the incorporation of bowel segments into the urinary tract may have metabolic consequences. This is an area somewhat neglected in the literature. Metabolic complications are rare, but sub-clinical metabolic disturbances are quite common. Several studies have demonstrated that some of the absorbent and secreting properties of the bowel tissue are preserved after incorporation into the urinary tract. Hyperchloraemic metabolic acidosis can occur if ileal and/or colon segments are used, as well as malabsorption of vitamin B(12) and bile acid after the use of ileal segments. These metabolic effects are not as severe as may be suspected and can be prevented by prophylactic substitution. Secondary malignancies can develop as a long-term consequence of bladder augmentation. Using colonic segments, tumours are most likely to occur at the ureteral implantation site. To prevent metabolic complications, careful patient selection and meticulous and lifelong follow up, as well as prophylactic treatment, are mandatory. Endoscopy for early detection has been recommended, starting 10 years postoperatively for patients who underwent surgery for a benign condition.

The contribution of malabsorption to the reduction in net energy absorption after long-limb Roux-en-Y gastric bypass

BACKGROUND

Roux-en-Y gastric bypass (RYGB) restricts food intake, and when the Roux limb is elongated to 150 cm, the procedure is believed to induce malabsorption.

OBJECTIVE

Our objective was to measure total reduction in intestinal absorption of combustible energy after RYGB and the extent to which this was due to restriction of food intake or malabsorption of ingested macronutrients.

DESIGN

Long-limb RYGB was performed in 9 severely obese patients. Dietary intake and intestinal absorption of fat, protein, carbohydrate, and combustible energy were measured before and at 2 intervals after bypass. By using coefficients of absorption to measure absorptive function, equations were developed to calculate the daily gram and kilocalorie quantities of ingested macronutrients that were not absorbed because of malabsorption or restricted food intake.

RESULTS

Coefficients of fat absorption were 92 ± 1.3% before bypass, 72 ± 5.5% 5 mo after bypass, and 68 ± 8.7% 14 mo after bypass. There were no statistically significant effects of RYGB on protein or carbohydrate absorption coefficients, although protein coefficients decreased substantially in some patients. Five months after bypass, malabsorption reduced absorption of combustible energy by 124 ± 57 kcal/d, whereas restriction of food intake reduced energy absorption by 2062 ± 271 kcal/d. Fourteen months after bypass, malabsorption reduced energy absorption by 172 ± 60 kcal/d compared with 1418 ± 171 kcal/d caused by restricted food intake.

CONCLUSION

On average, malabsorption accounted for ≈6% and 11% of the total reduction in combustible energy absorption at 5 and 14 mo, respectively, after this gastric bypass procedure.

Malabsorption syndrome with and without small intestinal bacterial overgrowth: a study on upper-gut aspirate using 1H NMR spectroscopy

Biochemicals in the upper-gut aspirate in 31 patients with malabsorption syndrome (MAS) with and without small intestinal bacterial overgrowth (SIBO), and 10 disease-free controls were analyzed using high-resolution (1)H-NMR spectroscopy, and were correlated with the degree of SIBO and severity of MAS. Compared to controls, the patients had higher quantities (micromol/L: median [range]) of total bile acids/cholesterol (2000 [0-12000] vs. 300 [0-600]), lactate (700 [0-5200] vs. nil [0-30]), acetate (200 [0-6500] vs. 20 [0-200]), and formate (80 [0-900] vs. nil [0-50]) (P < 0.01, Mann-Whitney U-test). However, amino acids and glucose were comparable in both. Quantities (micromol/L: median [range]) of acetate (1330 [220-6500] vs. 100 [0-1430]), lactate (1430 [670-3300] vs. 300 [0-5200]), formate (360 [0-600] vs. 25 [0-800]), and unconjugated bile acids (500 [40-600] vs. 10 [0-300]) were higher in MAS patients with SIBO than those without SIBO (P < 0.01, Mann-Whitney U-test, for all). In patients with MAS the quantity of acetate positively correlated with the degree of SIBO, and unconjugated bile acids correlated with the degree of steatorrhoea (Spearman's rank correlation coefficient, two-tailed, P < 0.05: 0.46 and 0.52, respectively). This study demonstrates the bacterial production of metabolites and deconjugation of bile acids in patients with MAS.

Bowel function after urinary diversion

Removal of bowel segments for the purposes of urinary diversion may have a significant effect on bowel function. The remaining bowel may not be able to fulfill its normal role, resulting in not only malabsorption syndromes, but also dysfunctional defecation. Provided, however, care is taken in selecting patients and the bowel segments for such procedures and follow-up is vigilant, complications should be minimal. There appears to be a significant risk of developing symptoms of increased bowel frequency following urinary diversion and reconstruction. Patients need to be counselled regarding this prior to surgery, however, further data needs to be collected to accurately quantify the risk and the effect it has on quality of life.

Malabsorption associated with surgical procedures and its treatment

Signs and symptoms of malabsorption after surgical procedures can be subtle and recognized late. This article reviews some of the more common surgical procedures potentially associated with malabsorption and suggests techniques of nutrition intervention. Early recognition, and preferably preventative care, should result in improved patient outcome.

The role of the duodenal microflora as a determinant of persistent diarrhoea

It has been suggested that proliferation of enterobacteriaceae and/or anaerobes in the duodenum of some children with acute diarrhoea determines whether the episode becomes persistent. A review of published studies and the comparison of cultures of duodenal aspirates from Peruvian children with acute and persistent diarrhoea and diarrhoea-free children did not support this hypothesis. Although many children had enterobacteriaceae and/or anaerobes cultured there was no correlation with clinical and nutritional outcome. Age, nutritional status, the environment and the aetiology of the episode were determinants of the duodenal microflora independent of diarrhoea. Culture of the duodenal aspirates did not increase the yield of enteropathogens which were isolated more frequently from stools than from the duodenum. Despite the presence of a single strain or serotype of enterobacteriaceae suggesting that these bacteria were colonizing the duodenum, we were unable to demonstrate any adherence mechanisms in the majority of them. Two of ten bacteria with no other evidence of virulence caused diarrhoea in the RITARD rabbit model.

Effect of oral gold salt therapy on bile acid absorption in rheumatoid arthritis patients

Several studies pointed out an altered stool pattern as the most common side effect of auranofin therapy. The major mechanism in the aetiology of auranofin-induced impairment in bowel habit seems to be the inhibition of Na+/K+ ATPase in the gut. In vitro experiments proved that auranofin can affect active bile acid (BA) reabsorption in rat terminal ileum; this action, due to the ability of the drug to reduce Na+ pump activity by inhibiting Na+/K+ ATPase, may make a significant contribution to the auranofin-induced diarrhoea. The ability of auranofin to reduce the Na+ gradient necessary for active BA reabsorption, however, could cause a decrease of serum BA levels in patients taking auranofin before or without the development of an overt diarrhoea. We measured fasting and postprandial serum conjugated BA levels in 10 female rheumatoid arthritis patients before and after one month and two months' auranofin treatment. No patient developed diarrhoea during the chrysotherapy. When oral gold salt therapy was started, we observed a slight decrease in serum BA levels, but difference was not statistically significant. We can conclude that auranofin therapy does not cause BA malabsorption in patients who do not develop diarrhoea during the treatment.

Severe acquired hypocholesterolemia: two case reports

We present two case reports from different institutions that emphasize two distinct aspects of severe acquired hypocholesterolemia. The first case report discusses the issue of malabsorption in a man with systemic lupus erythematosus and bacterial overgrowth of the small bowel. The second case report examines the data on metabolic abnormalities associated with severe illness that appear to be independent of digestion and absorption. These two cases serve to alert the physician that severe hypocholesterolemia is a portentous finding that may be associated both with a wide variety of diseases and with a high mortality rate. Successful therapy of the underlying diseases may lead to correction of the hypocholesterolemia.

Intestinal involvement in progressive systemic sclerosis detected by increased unconjugated serum bile acids

In patients with progressive systemic sclerosis, impaired motor function of the small intestine may lead to bacterial overgrowth causing diarrhoea, steatorrhoea and malabsorption. As unconjugated serum bile acids have been proposed as markers for small bowel bacterial overgrowth, we studied individual unconjugated serum bile acids in 36 patients with progressive systemic sclerosis. These patients had significantly higher serum concentrations of unconjugated cholic acid (median 0.18; range 0.05-30.75 v 0.09; 0.01-0.19 mumol/l, p less than 0.001) and chenodeoxycholic acid (0.10; 0.01-6.83 v 0.04; 0.01-0.39 mumol/l, p less than 0.025) than healthy controls (n = 16). This difference was mainly due to patients with diarrhoea (n = 10), who had significantly higher concentrations of unconjugated serum bile acids than patients with normal bowel habit (cholic acid median 0.55 v 0.16 mumol/l, p less than 0.001; chenodeoxycholic acid 0.75 v 0.07 mumol/l; p less than 0.005). All patients with raised unconjugated serum bile acids had oesophageal motility disorders. These results confirm a relationship between motility disorders and bacterial overgrowth in patients with progressive systemic sclerosis.

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.

Biochemical aspects of malabsorption in marasmus

Sixty marasmic children and fifteen normal age-matched controls were investigated for the absorption of fats and proteins. Their duodenal juice samples were also analysed for bile salts and microflora. A significant amount of malabsorption, with respect to both the dietary ingredients, was observed in the majority of the marasmic children. The levels of conjugated bile acids in the duodenal juice samples of marasmic children were significantly lower as compared with those of normal controls, while the reverse was true for free bile acids and bacterial counts. Significant correlations were observed between bile acid levels and fat absorption and also between microflora and free bile acids. The pathophysiology of malabsorption in marasmus is discussed in the light of these findings.

Effects of jejunoileal bypass on the enterohepatic circulation of bile acids, bacterial flora in the upper small intestine, and absorption of vitamin B12

Eleven morbidly obese patients were studied before and at various time intervals after jejunoileal bypass (JIB). Bile acid deconjugation was assessed with the bile acid breath test and bile acid absorption by analyzing the fecal excretion of both radioactively labeled and unlabeled bile acids. In addition, aerobic and anaerobic cultures of upper small intestinal aspirates, the Schilling vitamin B12 absorption test, and fecal fat analysis were performed. All patients developed marked diarrhea and steatorrhea after JIB. The bile acid breath test was positive in all 11 patients after JIB. In 7 of the 11 patients, this test was already slightly positive before JIB. In every instance, however, the bile acid breath test became significantly more abnormal after the bypass operation. The fecal excretion of labeled bile acids increased significantly. However, the increase in the quantitative excretion of the bile acids did not reach statistical significance. The concentrations of bile acids in fecal water were considerably below the levels required to induce diarrhea. This was mainly the result of a low fecal pH and consequent low aqueous solubility. Jejunoileal bypass effected a major shift in fecal bile acids from the secondary bile acids, lithocholic acid and deoxycholic acid, to the respective primary compounds, chenodeoxycholic acid and cholic acid. There were no significant changes in the small bowel bacteriologic findings after JIB. In 5 out of the 9 patients in whom bacteriologic studies were performed, the cultures were positive before the operation. The Schilling vitamin B12 absorption test showed in all patients a significant drop in the 24-hour urinary 57Co excretion rate after JIB.(ABSTRACT TRUNCATED AT 250 WORDS)

Utilisation of rye by chickens: effect of microbial status, diet gamma irradiation and sodium taurocholate supplementation

Several experiments were conducted to determine the influence of intestinal microflora when rye diets are fed to young chicks. In a conventional environment dietary rye severely depressed growth, amino acid and fat retention, and metatarsal bone ash. These conditions could be effectively alleviated by gamma irradiation of the diet and maintenance in a germ-free environment. In gnotobiotic chicks associated with streptococci dietary rye caused effects similar to those seen in a conventional environment, however the responses were less severe. Since addition of sodium taurocholate improved fat retention from a rye diet to a greater extent than from a wheat diet, a deficiency of conjugated bile salts might contribute to the steatorrhea observed in rye-fed chicks.

Protein digestion and absorption in the blind loop syndrome

Protein digestion and absorption was studied in rats with 6-week-old surgically constructed self-filling intestinal blind loops and steatorrhea, ie, blind-loop animals and controls were fed a 14C-labeled protein meal containing a nonabsorbable marker, 51CrCl3, and sacrificed 1 or 2 hr later. Intestinal contents were analyzed for 14C, 51Cr, protein, trypsin, and the products of digestion. At 1 hr, 14C absorption was greater in controls, but at 2 hr there was no difference in absorption between the two groups. Marker studies showed that blind-loop filling resulted in a delay of the progression of intestinal contents distally. Intraluminal trypsin and porteolysis were similar in the two groups. Endogenous protein was greater in the blind-loop animals. The early stages of the blind-loop syndrome may be characterized by delayed protein absorption secondary to blind-loop filling, which is compensated for by the distal gut resulting in an absence of overall protein malabsorption.

The contaminated small bowel syndrome

Contamination of the small bowel with an abnormal microflora causes a variety of disturbances of intraluminal digestion and of mucosal function resulting in malabsorption of fat, protein, carbohydrate, electrolytes and vitamin B12. Indirect clinical tests for the presence of small bowel bacterial overgrowth must be supported by careful roentgenologic examination of the small intestine and intestinal aspiration studies to establish a firm pretreatment diagnosis. However, the reversal of absorptive defects by antibacterial therapy is valuable confirmatory evidence.

Effects of cancer on nutrition: impaired organ system effects

The specific organ system effects of cancer and its treatment have been reviewed from the standpoint of nutritional impact. Nutritional impairment may occur as the result of specific organ system malfunction, and malnutrition itself may impair organ system functions in such a way as to compound these deficits. Nonmalignant, acute, and chronic illnesses resemble cancer in many ways, particularly in their ability to produce malnutrition and these organ system malfunctions. It is apparent that there is nothing particularly unique about many of these cancer states, from the standpoint of nutritional deficiency, that is not found in nonneoplastic conditions.

Sensitivity of bile acid breath test in the diagnosis of bacterial overgrowth in the small intestine with and without the stagnant (blind) loop syndrome

The bile acid breath test was studied to examine its sensitivity for establishing the diagnosis of bacterial overgrowth in comparison to that of the Schilling test and small-intestinal cultures in 12 patients with a stagnant (blind) loop syndrome, as well as in 38 patients who had other conditions with suspected bacterial contamination of the small intestine. The presence of bile acid malabsorption was excluded in all 50 patients by studies of fecal excretion of radioactively labeled bile acids. The bile acid breath test was positive in 100% (12/12) of the patients with a stagnant (blind) loop syndrome, whereas 92% (11/12) had a positive Schilling test and 75% (9/12) a positive small-intestinal culture. The abnormal tests improved only in 2 of 4 patients treated with tetracycline. In the group of 38 patients without demonstrable dilated or blind loops of small bowel who were suspected of having bacterial contamination of small bowel, the bile acid breath test was positive in 53% (20/38), the Schilling test in 39% (15/38), and the small-intestinal culture in 45% (17/38). The difference in the incidence of positive results between the tests in the two patient groups was statistically not significant. The findings of these studies have the following diagnostic implications: (1) Bile acid breath test, Schilling test, and cultures of aspirates from the upper small bowel are of comparable sensitivity in the detection of bacterial overgrowth in the small intestine. (2) A negative bile acid breath test makes the diagnosis of a stagnant (blind) loop syndrome very unlikely.

Effects of dihydroxy bile acids and hydroxy fatty acids on the absorption of oleic acid in the human jejunum

Perfusion studies of the normal human jejunum were performed to test whether dihydroxy bile acids and hydroxy fatty acids inhibit the absorption of oleic acid, since previous reports documented their inhibitory effects on the absorption of several other organic solutes. 3 mM deoxycholate and 7 mM glycodeoxycholate inhibited the absorption of 3 mM oleic acid in isotonic micellar solutions while inducing net fluid secretion. Similarly, fractional absorption of oleic acid decreased in the presence of hydroxy fatty acids. However, only the changes induced by 2 mM ricinoleic acid could be distinguished from changes induced by an increase in total fatty acid concentration. Under all experimental conditions, close linear relationships existed between net water movement and fractional absorption of glucose, xylose, and fatty acids, as well as between the absorption rates of these solutes. In contrast, net fluid secretion induced by hypertonic D-mannitol (450 mosmol/liter) had no effect on solute absorption. Our data and observations in the literature do not allow formulation of a hypothesis which would adequately define all effects of dihydroxy bile acids and fatty acids on intestinal transport processes. The observations help explain the malabsorption of fat and other nutrients in patients with the blind loop syndrome.

A new substrate for the rapid evaluation of enteric microbial overgrowth

The possibility of a new approach to diagnosis of intestinal bacterial overgrowth has been evaluated in laboratory animals. The diagnostic test involves oral administration of an enzyme-labile substrate consisting of para-aminobenzoic acid (PABA) conjugated to a bile acid. In the presence of enteric bacteria, PABA is split from the bile acid and is rapidly absorbed and excreted in the urine. The amount of PABA recovered during the 6 hr following the administered dose of the conjugate may be used as an index of bacterial overgrowth in the upper-gastrointestinal tract. The procedure has been shown to be a reliable index of this condition in laboratory animal models.

The effects of pure and micellar solutions of different bile salts on mucosal morphology in rat jejunum in vivo

The effects of pure and micellar solutions of different bile salts on mucosal morphology have been investigated in rat jejunum using a closed-loop technique; the effects of an anionic dihydroxy steroid antibiotic, fusidic acid, have also been studied. Mucosal changes were assessed by light-microscopical appearances and quantified by determining surface to volume ratios (c/1h). The unconjugated dihydroxy bile salts, chenodeoxycholate and deoxycholate (DC), produced similar and gross structural changes at concentrations of 2-5 to 5 mM, as judged by mucosal appearances, but not at 1 mM; the unconjugated trihydroxy bile salt cholate and a variety of di- and trihydroxy conjugated salts produced no changes at concentrations of 5 to 20 mM. Fusidate (5 mM) produced similar changes to 5 mM DC. Compared with control values DC (1,2-5 and 5 mM) and fusidate (5 mM) produced highly significant (P less than 0-001) reductions in c/1h ratios. DC-induced damage was completely abolished by mixed micellar solutions, whereas pure micellar solutions provided no protection. These results indicate, (i) a molecular specificity for bile salt-induced mucosal damage, and (ii) that the effects of the unconjugated dihydroxy species on mucosal structure depends not only on their intraluminal concentrations, but also on the relative concentrations of conjugated bile salts and lipids present in the lumen.

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.