Small bowel (small intestine)
Malabsorption
General

Author: Hanni Gulwani, M.D. (see Authors page)

Revised: 9 February 2018, last major update August 2012

Copyright: (c) 2003-2018, PathologyOutlines.com, Inc.

PubMed Search: Malabsorption[TI] small bowel[TIAB] full text[sb]

Cite this page: Gulwani, H. Malabsorption - general. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/smallbowelmalabsorptiongen.html. Accessed September 25th, 2018.
Definition / general
  • Standard site for biopsies is proximal jejunum, just distal to ligament of Treitz
  • Mount specimen mucosal side up on solid substance, then embed perpendicular to mounting material, then step section or serial section
  • Small bowel is important for absorption of fats, fat soluble vitamins, proteins, carbohydrates, electrolytes, minerals, water
  • In U.S., most common malabsorption disorders are celiac sprue, pancreatic insufficiency and Crohn's disease
  • Steatorrhea: bulky, greasy stools associated with weight loss, anorexia, muscle wasting
Symptoms associated with specific deficiencies
  • Diarrhea, flatus, abdominal pain, weight loss, mucositis, anemia (iron, folate, vitamins B6, B12)
  • Bleeding / purpura (vitamin K)
  • Osteopenia, tetany (calcium, magnesium, vitamin D)
  • Amenorrhea / impotence / infertility (generalized malnutrition)
  • Hyperparathyroidism (calcium, vitamin D)
  • Edema (albumin)
  • Dermatitis (zinc, vitamin A, fatty acids, niacin)
  • Peripheral neuropathy (vitamins A, B12)
Physiologic classification of malabsorption
Disturbances related to:
  1. Intraluminal digestion: saliva, gastric peptic digestion, small bowel, bile salts
  2. Terminal digestion: hydrolysis of carbohydrates and peptides by disaccharidases and peptidases in brush border of small bowel
  3. Transepithelial transport: across small bowel epithelium to intestinal vasculature; fatty acids to triglycerides, cholesterol to chylomicrons

(a) Causes of defective intraluminal digestion:
  • Digestion of fats / proteins: pancreatic insufficiency due to pancreatitis or cystic fibrosis, Zollinger-Ellison syndrome
  • Defective bile secretion (fat solubilization): ileal dysfunction or resection with decreased bile salt uptake, cessation of bile flow (obstruction, hepatic dysfunction), nutrient preabsorption or modification by bacterial overgrowth

(b / c) Causes of abnormalities in terminal digestion or transepithelial transport:
  • Disaccharidase deficiency (lactose intolerance), bacterial overgrowth, abetalipoproteinemia, defects in ileal bile acid transporter