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Differentiation of osmotic and secretory diarrhoea by stool carbohydrate and osmolar gap measurements
J A Castro-Rodríguez1, E Salazar-Lindo, R León-Barúa
1Department of Paediatric, Universidad Peruana Cayetano Heredia, Lima, Perú.
Insights
Detecting osmotic versus secretory diarrhea in children is crucial. The presence of excess reducing substances in stool, identified by Benedict
Area of Science:
- Pediatrics
- Gastroenterology
- Clinical Diagnostics
Background:
- Differentiating between osmotic and secretory diarrhea in infants and children is essential for appropriate management.
- Existing diagnostic methods require further evaluation for accuracy in distinguishing these two types of watery diarrhea.
Purpose of the Study:
- To evaluate clinical features and laboratory tests for distinguishing osmotic from secretory diarrhea in young children.
- To identify the most sensitive and specific diagnostic marker for differentiating these diarrheal conditions.
Main Methods:
- Prospective study of 80 boys (3-24 months) with acute watery diarrhea.
- Calculation of the fecal osmolar gap (FOG) to classify diarrhea type.
- Assessment of clinical features, fecal tests (reducing substances, pH, steatorrhoea), and blood/urine tests.
Main Results:
- Fifty-eight patients had osmotic diarrhea (FOG > 100 mosmol/l) and 22 had secretory diarrhea (FOG ≤ 100 mosmol/l).
- Steatorrhoea and acid fecal pH were more frequent in osmotic diarrhea.
- Tests for reducing substances, particularly Benedict's test with hydrolysis, showed significant association with osmotic diarrhea.
Conclusions:
- The presence of excess reducing substances in stool, detected by Benedict's test with hydrolysis, is the most sensitive and specific indicator for differentiating osmotic diarrhea.
- This simple fecal test offers the best predictive value for distinguishing between osmotic and secretory watery diarrhea in pediatric patients.
Abstract:
Clinical features and laboratory tests that determine carbohydrate in faeces were evaluated to determine which was best able to distinguish between osmotic and secretory diarrhoea in infants and children. For this purpose 80 boys aged 3 to 24 months, with acute watery diarrhoea, were studied prospectively. The faecal osmolar gap (FOG) was calculated as: serum osmolarity-[2 x (faecal sodium + potassium concentration)]. Fifty eight patients were classified as having predominantly osmotic diarrhoea (FOG > 100 mosmol/l), and 22 as having predominantly secretory diarrhoea (FOG < or = 100 mosmol/l). The two groups were comparable in their clinical features on admission, in the results of blood and urine tests, and in the evolution of their diarrhoeal illness. Evidence of steatorrhoea (by positive Sudan III test) and of acid faecal pH on admission were significantly more frequent in patients with osmotic diarrhoea. Mean (SD) faecal osmolarity was not significantly different between the two groups (319 (80) mosmol/l in secretory diarrhoea v 361 (123) mosmol/l in osmotic diarrhoea). Tests for reducing substances in faeces such as Benedict's test--with and without hydrolysis--and glucose strip, all showed a positive and significant association with osmotic diarrhoea (p < 0.05, < 0.025, < 0.05, respectively). The presence of excess reducing substances (Benedict's test with hydrolysis > 2+) on admission was the most sensitive and specific test with the best predictive value for differentiating between the two types of watery diarrhoea.