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Toronto Notes 2019
Small and Large Bowel
Gastroenterology G17
Clinical Features
• symptomsusuallyvagueunlessdiseaseissevere
• weightloss,diarrhea,steatorrhea,weakness,fatigue • manifestationsofmalabsorption/deficiency
Table 9. Absorption of Nutrients and Fat Soluble Vitamins
Fat Soluble Vitamins: ADEK
vitamin A, vitamin D, vitamin E, vitamin K
Deficiency
Iron Calcium
Folic Acid Vitamin B12
Carbohydrate
Protein Fat
Vitamin A
Vitamin D Vitamin E Vitamin K
Absorption
Duodenum, upper jejunum
Duodenum, upper jejunum (binds to Ca2+ binding-protein in cells; levels increased by Vit D)
Jejunum
B12 ingested and bound to R proteins mainly from salivary glands; stomach secretes intrinsic factor (IF) in acidic medium; in basic medium, proteases from the pancreas cleave R protein and B12-IF complex forms, protecting B12 from further protease attack; B12 absorbed in ileum and binds to transcobalamin (TC)
Complex polysaccharides hydrolyzed to oligosaccharides, and disaccharides by salivary and pancreatic enzymes Monosaccharides absorbed in duodenum/ jejunum
Digestion at stomach, brush border, and inside cell
Absorption occurs primarily in the jejunum
Lipase, colipase, phospholipase A (pancreatic enzymes), and bile salts needed for digestion
Products of lipolysis form micelles which solubilize fat and aid in absorption Absorption occurs primarily in the jejunum Fatty acids diffuse into cell cytoplasm
Dietary sources (e.g. milk, eggs, liver, carrots, sweet potatoes)
Skin (via UV light) or diet (e.g. eggs, fish oil, fortified milk)
Dietary sources (e.g. vegetable oils, nuts, leafy green vegetables)
Synthesized by intestinal flora
risk of deficiency after prolonged use of broad spectrum antibiotics and/or starvation
Clinical Disease and/or Features
Hypochromic, microcytic anemia, glossitis, koilonychia (spoon nails), pica
Metabolic bone disease, may get tetany and paresthesias if serum calcium falls (see Endocrinology, E41)
Megaloblastic anemia, glossitis, red cell folate (may seefolic acid with bacterial overgrowth)
Subacute combined degeneration of the spinal cord, peripheral/ optic neuropathy, dementia, megaloblastic anemia, glossitis
Generalized malnutrition, weight loss, flatus, and diarrhea
General malnutrition and weight loss, amenorrhea, andlibido if severe
Generalized malnutrition, weight loss, and diarrhea
Foul-smelling feces + gas Steatorrhea
Night blindness Dry skin Keratomalacia
Osteomalacia in adults Ricketts in children
Retinopathy, neurological problems
Prolonged INR may cause bleeding
Investigations
 Hb,  serum Fe,  serum ferritin  serum Ca2+,  serum Mg2+, and
 ALP
Evaluate forbone mineralization radiographically (DEXA)
serum folic acid Differentiate causes by nuclear
Schilling test (when available) Positive anti-intrinsic factor antibodies and atrophic gastritis point toward pernicious anemia (see Hematology, H24)
Hydrogen breath test
Trial of carbohydrate-restricted diet D-xylose test
serum albumin (low sensitivity) Small bowel biopsy
MRCP, ERCP, pancreatic function tests (not routinely available) Quantitative stool fat test (72 h) May start with qualitative stool fat test (Sudan stain of stool) C-triolein breath test (not routinely available)
* Calcium malabsorption more commonly causes decreased bone density rather than hypocalcemia because serum calcium levels are protected by leaching calcium from the bone
Investigations
• tissuetransglutaminase(tTG)antibodyserology/immunoglobulinAquantitationandabdominal imaging are most useful because celiac disease and chronic pancreatitis are the two most common causes of steatorrhea
• 72hstoolcollection(weight,fatcontent)documentssteatorrhea(goldstandard)
• fecalelastasetoscreenforpancreaticinsufficiencyand/orconsiderempirictrialofpancreaticenzymes
based on clinical context
• serumcarotene(precursortovitaminA),folate,Ca2+,Mg2+,vitaminB12,albumin,ferritin,serumiron
solution, INR/PTT
• stoolfatglobulesonfecalsmearstainedwithSudan(usedasaninitialscreeningtool)
• othertestsspecificforetiology(e.g.CTscan/MRItovisualizepancreas)
Treatment
• dependentonunderlyingetiology