Diagnostic Considerations
Considerations
Consider specific causes of diarrhea and malabsorption.
Consider the diagnosis of tropical sprue if the initial history, physical, and laboratory workups are suggestive of mucosal malabsorption.
Although tropical sprue can manifest as an acute diarrheal illness, the clinical diagnosis is usually not considered until patients present with chronic symptoms.
Diarrhea and fat malabsorption may occasionally be difficult to differentiate. Perform a 24- to 72-hour stool test for fat. May lose up to 40 grams of fat in the stool daily. Total stool fat less than 6-7 g/d excludes steatorrhea; therefore, consider chronic diarrhea.
Studies differentiating tropical sprue from other gastrointestinal conditions
Versus gluten-sensitive enteropathy
Brown et al compared the histologic changes found in tropical sprue with those occurring in gluten-sensitive enteropathy, a condition for which tropical sprue is often mistaken. The study, which involved 12 patients with tropical sprue and 150 cases of gluten-sensitive enteropathy, identified no complete villous blunting in the duodenal mucosa of the tropical sprue patients, although partial blunting occurred in 75% of them. In contrast, complete villous blunting was identified in 25% of gluten-sensitive enteropathy patients. The investigators also found that in the appropriate clinical context, tropical sprue is indicated by involvement of the terminal ileum, with greater inflammation and villous blunting than in the duodenum, and by the presence, in the lamina propria, of a conspicuous eosinophil infiltrate. [7]
Versus celiac disease
A 2012 study of Indian adults by Ghoshal et al indicated that, in comparison with patients with tropical sprue, those with celiac disease tended to be younger (< 35 years), have a longer duration of diarrhea and a higher platelet count, and more often demonstrate villous atrophy (subtotal or partial). [8]
A 2018 systematic review to differentiate clinical, endoscopic, and histologic features between celiac sprue and tropical sprue found no differences in the prevalence and duration of chronic diarrhea, abdominal distention, weight loss, extent of abdominal fat content, and density of intestinal inflammation. [6]
Features more common in tropical sprue were as follows [6] :
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Anemia
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Abnormal urinary D-xylose test
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Endoscopy showing either normal duodenal folds or mild attenuation
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Histology revealing decrescendo type of intraepithelial lymphocytosis (IELosis), low modified Marsh changes, patchy mucosal changes, and mucosal eosinophilia
In contrast, features more common in celiac sprue included the following [6] :
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Short stature
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Vomiting/dyspepsia
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Endoscopy showing scalloping/attenuation of the duodenal folds
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Histology revealing crescendo type of IELosis, high modified Marsh changes, surface epithelial denudation, surface mucosal flattening, and thickening of subepithelial basement membrane
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Celiac seropositivity
Other conditions to consider
Diseases of general fat malabsorption to consider include the following:
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Bacterial overgrowth
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Ileal diseases
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Pancreatic disorders
Mucosal diseases leading to malabsorption to consider include the following:
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Acquired immunodeficiency syndrome (AIDS) enteropathy
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Celiac sprue
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Cryptosporidia
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Giardiasis
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Infectious causes
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Nonspecific enteropathy
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Norwalk virus
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Radiation enteropathy
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Intestinal lymphoma
Differential Diagnoses
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Tropical Sprue. Subtotal villous atrophy (hematoxylin-eosin [H&E], original magnification ×10).
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Tropical Sprue. Tropical sprue (hematoxylin-eosin [H&E], original magnification ×10).
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Tropical Sprue. Endoscopic views of unsuspected celiac disease. A: Absent duodenal folds. B: Mucosal fissures and scalloped folds. C: Scalloped fold.
