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Urinary mannitol: lactulose excretion ratios and jejunal mucosal structure
K A Nathavitharana1, D R Lloyd, F Raafat
1Institute of Child Health, University of Birmingham.
Insights
This dual sugar absorption test accurately detects severe villous atrophy in children. However, its sensitivity decreases with milder mucosal damage, limiting its use as a general screening tool for enteropathies.
Area of Science:
- Pediatric Gastroenterology
- Gastrointestinal Physiology
- Diagnostic Testing
Background:
- Assessing small intestinal mucosal integrity is crucial for diagnosing pediatric enteropathies.
- Non-invasive diagnostic methods are desirable for pediatric gastrointestinal evaluations.
- Dual sugar absorption tests offer a potential non-invasive approach to assess intestinal permeability.
Purpose of the Study:
- To evaluate the diagnostic accuracy of a dual sugar (mannitol, lactulose) absorption test in children with varying degrees of mucosal damage.
- To establish reference ranges and assess the test's correlation with body surface area.
- To determine the test's utility in monitoring mucosal changes in response to therapeutic interventions like gluten withdrawal.
Main Methods:
- A dual sugar absorption test using mannitol and lactulose was administered orally to a study group of 43 children with mucosal damage and 53 healthy controls.
- Urinary excretion ratios of mannitol and lactulose were measured over three hours post-administration.
- Correlation with body surface area was analyzed, and a lower limit of normal was established.
- Sensitivity and specificity for severe villous atrophy were calculated. Sequential studies were conducted in 18 children.
Main Results:
- A significant positive correlation was observed between the urinary mannitol: lactulose ratio and body surface area in controls.
- The test demonstrated high specificity (98%) and sensitivity (95%) for severe villous atrophy.
- Sensitivity decreased significantly with milder degrees of mucosal damage, indicating it's not ideal for screening all enteropathies.
- Sequential studies showed the ratio changes reflected mucosal structural alterations induced by gluten challenges or withdrawal.
Conclusions:
- The dual sugar absorption test is highly accurate for diagnosing severe villous atrophy in children.
- The test's utility is limited as a general screening tool for all enteropathies due to declining sensitivity with less severe mucosal damage.
- This absorption test shows promise for sequential monitoring of small intestinal mucosal lesions, particularly in response to dietary interventions.
Abstract:
A dual sugar (mannitol, lactulose) absorption test was evaluated using an iso-osmolar oral dose in two groups of children: a study group of 43 children divided into five subgroups, based on severity of mucosal damage, and a control group of 53 children with histologically normal jejunal biopsy specimens. After an oral dose, the three hour urinary mannitol: lactulose ratios in the control group showed a highly significant positive correlation with body surface area. After correction for the body surface area relationship, a control lower limit was defined by the mean -2SD of the log10 transformed control mannitol: lactulose ratios. Specificity and sensitivity for severe villous atrophy was 98% and 95% respectively but the sensitivity declined rapidly with decreasing degrees of mucosal damage, and the test would not therefore be an adequate screening procedure for all enteropathies. In sequential studies in 18 children, the changes in the mannitol: lactulose ratio were consistent with the changes in mucosal structure induced by gluten challenge or gluten withdrawal. The test may therefore have a role in any sequential study of lesions of the mucosa of the small intestine.