Topic:Malabsorption syndromes and acid peptic diseases
Question:What are malabsorption syndromes? How are they diagnosed?
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Malabsorption syndromes are conditions characterized by impaired absorption of nutrients from the gastrointestinal tract. They are diagnosed based on clinical features, stool studies, endoscopy, histology and absorptive testing:
Patients present with diarrhea, steatorrhea, weight loss, and deficiency of fat-soluble vitamins/malnutrition. Stool floats due to high fat content and is foul-smelling. Endoscopy may show abnormal mucosa. Duodenal biopsy reveals villous atrophy or inflammation on histology.
Absorptive testing:
– D-xylose test: Measures absorption of D-xylose sugar. Patients ingest 25g xylose; <23mmol/L in urine after 5h indicates malabsorption.
– Fecal fat quantitation: Measures fat excretion over 3-5 days. >7g/day indicates steatorrhea/fat malabsorption.
– Vitamin B12/folate levels: May be low due to ileal disease or bowel overgrowth.
– Schilling test: Uses radio-B12 to assess B12 absorption.
Two types:
1. Normal absorption if >10% dose excreted in 24h urine.
2. With intrinsic factor: If low excretion and improves with intrinsic factor, suggests pernicious anemia.
– D-xylose/lactose breath test: After ingesting xylose/lactose, breath samples measure exhaled hydrogen/methane. High levels indicate poor absorption.
Common causes of malabsorption include:
– Celiac disease: Gluten sensitivity damaging small bowel villi. Diagnosis with IgA anti-tTG titers and duodenal biopsy.
– Inflammatory bowel disease: Crohn’s disease can cause ileal inflammation/resection impairing B12/bile salt absorption. Ulcerative colitis spares small bowel.
– Bacterial overgrowth: Excess bacteria in small intestine compete for nutrients and produce toxins. Diagnosed with breath testing.
– Pancreatic insufficiency: Lack of pancreatic enzymes leads to fat/protein malabsorption. Fecal elastase measures pancreatic function.
– Gastrectomy/gastric bypass: Reduced stomach acid and bypassing duodenum impairs absorption, especially of B12 and iron.
– Lymphoma/amyloidosis: Infiltrative small bowel processes disrupt absorption. Diagnosis by biopsy.
– Radiation enteritis: Prior radiation exposure damages intestinal lining, causing malabsorption. Based on history of radiation treatment.
– Parasitic infections: Giardiasis or strongyloidiasis infect small intestine, impairing absorption. Stool O&P and serology can detect parasites.
In summary, malabsorption syndromes result from disease processes impairing gastrointestinal absorption of nutrients. They require clinical evaluation, non-invasive testing of absorptive capacity and endoscopy with histology to determine the underlying etiology and appropriate treatment to correct deficiencies and improve quality of life.
