Urinary Xylose Excretion Research Articles

The effect of severe undernutrition, and subsequent refeeding on digestive function in human patients.

Severe undernutrition may adversely affect gut function. To investigate the effects of severe undernutrition and subsequent refeeding on human digestive function. Severely undernourished patients (body mass index (BMI) < 17 kg/m2) were studied before, and after a period of intensive nutritional support. Standard intestinal absorption tests (faecal fat and urinary xylose excretion), pentagastrin-stimulated acid secretion, and cholecystokinin octapeptide (CCK-8)-stimulated pancreatic enzyme secretion tests were performed. In addition, duodenal biopies were taken to assess gut mucosal morphology. Findings were evaluated in comparison to a group of normal healthy volunteers. Mean BMI of the patients prior to nutritional support was 13.41 kg/m2, with improvement to 16.12 kg/m2 after. Duodenal histology showed evidence of villous atrophy in six of 14 (43%) undernourished patients. Mean xylose excretion following a 5 g oral dose was 0.62 g/5 h in the group of undernourished patients prior to nutritional support (normal > 1 g/5 h), with improvement to 1.40 g/5 h (P < 0.01) after feeding. Maximal gastric acid output was significantly impaired in the undernourished group, as compared to the controls (6.94 mEq/l vs 25.53 mEq/l, P < 0.02), with a significant improvement to 12.30 mEq/l (P < 0.05) following nutritional support. Pancreatic enzyme output was significantly reduced (amylase 830.9 U/h vs 2304 U/h, P < 0.01; lipase 38.0 U/h vs 118.6 U/h, P < 0.01; trypsin 119.7 U/h vs 341.4 U/h, P < 0.01). Following a period of nutritional support there was a significant improvement in amylase and lipase outputs to 1819 U/h and 85.5 U/h, respectively (P < 0.01). These levels were not significantly different from the normal controls. Trypsin output, however, remained significantly impaired at 174.3 U/h (P < 0.01). Severe undernutrition is associated with significant impairment of digestive function, with improvement occurring following nutritional support. These changes may affect initial tolerance to enteral feeding, particularly in those patients with co-existent gut disease.

Rapid orocecal transit in chronically active persons with high energy intake

Although chronic physical activity by humans can raise energy requirements and energy intake severalfold above sedentary levels, whether these increases alter digestive strategy remains unknown. To investigate this possibility, food passage rate (mouth-to-large intestinal lactulose transit) and absorption (xylose) were compared in a cross section of young men chosen to represent a wide range of daily physical activity and food intake. In 20 men (energy intake 1,272-5,342 kcal/day), resting mouth-to-cecum transit was faster in high caloric consumers (r = -0.69, P less than 0.01). In contrast, xylose absorption (n = 26; measured either as urinary xylose excretion or integrated breath H2 production from the sugar) was unrelated to food intake. Dietary fiber intake was uncorrelated with energy intake. This apparent human digestive strategy of rapid transit across the gut absorptive surface, without a sacrifice in absorption, parallels the adaptations made by several animal species similarly faced with increased energy demand at constant fiber intake. We therefore conclude that the hyperphagia of chronic exercise in humans may be linked with significant gastrointestinal adaptations.

Bioavailability of digoxin tablets in patients with gastrointestinal dysfunction

In 47 patients with disorders of the gastrointestinal tract, the bioavailability of digoxin tablets was assessed by measuring the area under the serum concentration-time curve (AUC) after the oral administration of single 0.5 mg doses. In 13 or 14 patients who had undergone a previous ileal resection, in 10 of 10 patients with sprue and in 14 of 14 patients with a variety of disorders of the gastrointestinal tract, digoxin absorption was normal despite marked steatorrhea in many. A patient with extensive jejunal and ileal resection, and inflammation of the remaining small bowel, was the sole exception. Impaired digoxin bioavailabllity was found in five of nine patients who had undergone jejunoileal bypass procedures (bypass patients). A strong correlation was noted between the length of jejunum remaining in continuity and the AUC (r = 0.86, p < 0.01). Two of three bypass patients also showed decreased absorption of more rapidly dissolving tablets or an elixir. Digoxin bioavailability correlated significantly with 1 and 2 hour serum xylose levels but not with urinary xylose excretion, fecal fat or the Schilling test result. The findings are consistent with the role of the upper small bowel as the predominant site of digoxin absorption as well as the reserve function of the ileum in the event of jejunal dysfunction or bypass.

Breath hydrogen after oral xylose in tropical malabsorption

Thirty hospital in-patients (12 of whom were suspected on clinical grounds of having tropical mahabsorption (TM), and 18 who either had trivial symptoms or were undergoing a routine examination after tropical exposure) had breath hydrogen determinations at 10 mm intervals for 5 hr, and 5-hr urinary and 90-mm blood xylose measurements, after 25 g oral xylose. In seven patients (five of whom had evidence of TM), a significant increase in breath hydrogen above the fasting concentration (T) was observed during the 1st hour (group 1); they all excreted 5 g xylose. The remaining 15 patients did not show a significant increase in hydrogen compared with the fasting concentration (group 3); xylose excretion was >5 g. Correlation between T and urinary xylose excretion in groups 1 and 2 was significant (P < 0.001). Twenty-five patients also had breath hydrogen estimations at lO-min intervals after 33.5 g oral lactulose, and mean T was similar in those in groups 1 to 3; a previous study has demonstrated a significant slowing of transit in TM. A rise in hydrogen production during the 1st hour after xylose is presumably, therefore, a reflection of small intestinal bacterial activity, and is not the result of rapid transit. Bacterial metabolism of xylose seems to be much less in TM than in the blind-loop syndrome, and does not invalidate the test in TM. If hydrogen production rises during the 1st hour after 25 g xylose, total 5 hr urinary xylose excretion is <5 g; that is likely to constitute a valuable noninvasive test in the evaluation of TM. Am. J. Clin. Nutr. 33: 555-560, 1980.

Effect of Soy Protein on Intestinal Absorptive Ability of Calves by the Xylose Absorption Test

Five calves per group were fed whole milk (control) or one of three milk replacers with one-third of the total protein provided by a soy product. Soy products were Promocaf (a commercial soy protein concentrate), an experimental soy protein concentrate, and an experimental soy flour. After a 24-h fast, calves were fed xylose solution. Urine was collected for 5h. Jugular blood was sampled at 0, .5, 1, 1.5, 2, 2.5, 3, 4, and 5h after xylose administration. Xylose tests were weekly on each calf through 5 wk of age. Urinary xylose excretion, as a percentage of xylose fed, was higher in the control group during the last 4 wk than in groups fed milk replacers. Mean urinary xylose excretions during 5 wk from calves sampled 5h after xylose administration were 12.4, 4.2, 4.2, and 4.3% of xylose administered for calves fed milk, soy flour, soy protein concentrate, and Promocaf, respectively. Mean increases in peak of xylose concentration in plasma were 55.7, 44.4, 42.8, and 45.3 mg/100ml. Peak values for control calves were higher than those for calves fed soy products at wk 4 and 5. Times required to reach peak value did not differ significantly. Neither xylose concentration of plasma nor urinary xylose excretion differed among the groups fed soy products.

Evaluation of xylose absorption as measured in blood and urine: A one-hour blood xylose screening test in malabsorption

The assessment of d-xylose absorption by measurement of urinary excretion is subject to several sources of error. An investigation has been made into the use of the blood levels obtained after a 5-g dose as an assessment of malabsorption. We have shown that optimal discrimination between normal and impaired xylose absorption is achieved by measuring blood xylose levels 1 hr after oral administration and then correcting the results to a constant body surface area. The reference range was 0.65 to 1.33 mmoles per liter for values corrected to 1.73m2. In a prospective study of the value of this modification in investigating malabsorption, the incidence of falsenegatives and false-positives was found to be 4.8 and 2.2%, respectively. The test is of particular value in the elderly because surface area corrected 1-hr blood xylose levels are independent of age, eliminating the expected and observed declines in renal function and urinary xylose excretion in this age group.

Xylose catabolism in the experimental rat blind loop syndrome: Studies, including use of a newly developed d-[14C]xylose breath test

Intraluminal bacterial catabolism of xylose in an experimental rat blind loop model has been evaluated by means of a newly developed d-[14C]xylose breath test. The system employed affords frequent determination of total CO2 and 14CO2 and the opportunity for post-therapy evaluation. Rats with jejunal self-filling blind loops expired 40% of an orogastric dose of d-[14C]xylose as 14CO2 over 6 hr, as compared to 9% in nonoperated control rats and 17% in surgical controls with self-emptying blind loops. 14CO2 production decreased significantly with neomycin treatment of rats with self-filling blind loops, and was correlated with a significant decrease of gram-negative coliforms in jejunal contents. Small intestinal bacteria could be implicated in the production of up to 76% of the 14CO2 production by blind loop rats, with colon bacterial catabolism of unabsorbed xylose a smaller additive factor.Intravenous administration of d-[14C]xylose demonstrated that 14CO2 production by cellular metabolism of xylose was an insignificant part of the breath 14CO2 output. Urinary xylose excretion was significantly decreased in rats with self-filling blind loops by an amount correlating with the demonstrated intraluminal bacterial catabolism of xylose. Thus, intraluminal catabolism of xylose by small intestine bacteria appears to be the major determinant of the decreased urinary xylose excretion of the experimental blind loop syndrome, with colon bacterial catabolism of malabsorbed xylose a probable minor additional factor.

Jejunal monosaccharide, water, and electrolyte transport in patients with chronic pancreatitis.

Jejunal perfusion studies were performed to assess water, electrolyte, d-xylose, and d-glucose transport in 16 patients with chronic calcific pancreatitis (eight with and eight without steatorrhoea) and in 10 control subjects. The patients with steatorrhoea demonstrated significantly less xylose, water, and electrolyte absorption than patients without steatorrhoea and control subjects, when an isosmotic slaine-xylose solution was perfused. On the other hand, when an isosmotic saline-glucose solution was perfused, the patients with steatorrhoea absorbed significantly more glucose, water, and electrolytes than control subjects. Significant correlation was demonstrated between the absorption of xylose as measured by the segmental perfusion technique and the peak serum xylose level during perfusion as well as the five-hour urinary xylose excretion after a 25 g oral dose of xylose. The xylose absorption measured by small bowel perfusion also correlated significantly with pancreatic juice amylase and trypsin concentrations obtained during a standard pancreatic function test.

Xylose‐1‐14 C Absorption Test: The use of Urine, Serum and Breath Analysis, and Comparison with a Colorimetric Assay

The xylose absorption and excretion test has been reassessed in controls and patients with coeliac disease. Xylose has been assayed in both serum and urine colorimetrically and by liquid scintillation counting using xylose-1-14C. The excretion of 14CO2 in breath following administration of xylose-1-14C has been measured. Liquid scintillation counting is a simple and reliable method for the measurement of xylose absorption. Serum xylose levels, urinary xylose excretion, or breath 14CO2 in isolation were poor screening tests for mucosal disease. The use of serum levels and urinary excretion in combination improved the discriminatory value of the test though small gut biopsy was more reliable.

Intestinal Perfusion Studies in Tropical Sprue: I. Transport of water, electrolytes, and d-xylose

Segmental jejunal perfusion studies were performed to assess water, sodium, chloride, and d-xylose transport in 10 carefully selected patients with untreated tropical sprue who had diarrhea at the time of perfusion, and in 8 control subjects. All of the patients with tropical sprue were found to be in a net secretory state in regards to water, sodium, and chloride as compared with control subjects. d-Xylose absorption was impaired in patients with tropical sprue as compared with control subjects. A significant correlation was demonstrated between the absorption of xylose as measured by the segmental perfusion technique and the 5-hr urinary xylose excretion as well as the peak serum xylose level obtained with a standard xylose absorption test utilizing a 25-g dose of xylose when combined data from control and tropical sprue subjects are analyzed. The net secretory state for water, sodium, and chloride observed in patients with tropical sprue may be of relevance in explaining, at least partially, the pathogenesis of the diarrhea seen in this syndrome. Contamination with coliform bacteria has been reported in tropical sprue, and, more recently, certain of these organisms have been shown to produce enterotoxins. Whether these enterotoxins account fully for the derangements in water and electrolyte transport found present in patients with tropical sprue remains undetermined.

Gastrointestinal Function in Iron Deficiency States in Children

Gastrointestinal function, chiefly acid secretion by the stomach, was studied in 30 children with iron deficiency anemia and in 13 healthy children of comparable age. Sixteen of the anemic patients had an associated hookworm infection and in 14 the anemia was due to dietary iron deficiency. Gastric acidity was reduced in all of the anemic patients regardless of etiology and of whether observations were made under basal conditions or following stimulation with histamine. A direct effect of hookworm infestation could not be demonstrated either in terms of acid secretion or by biopsy of the small bowel. In these children anemia seemed vastly more important than damage wrought by hookworms in reducing acid secretion by the stomach. Additional observations on fecal fat and urinary xylose excretion did not yield definitive conclusions.

THE XYLOSE EXCRETION TEST IN NORMAL CHILDREN AND IN PEDIATRIC PATIENTS WITH TROPICAL SPRUE

The 5-hour urinary xylose excretion test was performed in 158 normal Puerto Rican school children 2½ to 13 years of age after the administration of a 5 gm oral dose of D-xylose. The values ranged from 0.7 to 2.3 gm with a mean of 1.44 gm and a standard deviation of ± 0.35 gm. Seven children excreted 0.9 gm or less (18% of the oral dose), which was the upper limit of excretion by the patients with untreated tropical sprue. All except one of the values below 1.0 gm occurred in children less than 6½ years of age. Thirty children with proven untreated tropical sprue showed a range of 0.2 to 0.9 gm, with a mean of 0.54 gm and a standard deviation of ± 0.20 gm Seventeen patients with tropical sprue treated for 6 months to 2 years showed a xylose excretion of 1.0 to 2.3 gm with a mean of 1.48 gm and a standard deviation of ± 0.36 gm. The lowest value obtained in this group, 1.0 gm, is higher than the seven lowest values in the control group. Our study confirms that the xylose excretion test is a simple and very reliable test of intestinal absorption. It is very useful as a screening test for the diagnosis of tropical sprue and in the follow up of treated patients.

Pediatric Xylose Absorption Test: Measurements in Blood Preferable to Measurements in Urine

Abstract Data from 129 pediatric patients given oral xylose tolerance tests were reviewed and statistically analyzed to determine if blood concentrations are a more acceptable diagnostic tool than urinary excretion. After oral administration of D-(+)-xylose, blood xylose concentrations were measured at 0.5, 1, 2, 3, and 4 h, and a 5-h urine sample was analyzed. Urinary xylose excretion was more variable than blood concentration. The best criterion of celiac disease through blood sampling is a failure of blood xylose to increase during the first hour of the test. An age difference was observed but appears to be critical only if the patient is less than six months old: the lower limits of normal as determined at 0.5, 1, and 2 h are 10, 15, and 15 mg/100 ml, respectively, for patients less than six months old; and 15, 20, and 20 mg/100 ml, respectively, for older patients.

The interpretation and significance of the xylose tolerance test in the tropics.

Abstract Xylose tolerance tests were performed in 158 Thai and 60 American subjects in Thailand. Urinary xylose excretion was normally distributed in the 2 nationalities. Five hour total urine xylose was significantly higher in the American subjects. After 8 months in Thailand, however, the American subjects excreted the same amount of xylose as the Thai subjects. The serum xylose concentration 2 hours following oral administration of the pentose sugar was significantly lower in the Americans and did not change when the test was repeated after 8 months of residence in the tropics. Studies of the reproducibility of the test showed a low coefficient of variation for the chemical determination of xylose. There was marked day-to-day variation in individuals which could not be accounted for by laboratory error. Because of this, considerable caution must be exercised in the interpretation of intermediate values for xylose excretion (3 to 5 Gm. per 5 hours) in subjects in the tropics.

Urinary xylose excretion in steatorrhoea.

The urinary xylose excretion is low in patients with untreated idiopathic steatorrhoea but subsequent improvement in excretion was noted after treatment in six out of nine patients. This did not coincide with histological improvement. With Crohn's disease low values were found when the jejunum but not the ileum was involved.