2Objectives: Upon completion of this lecture the students will : Understand that the malabsorption is caused by either abnormal digestion or small intestinal mucosaKnow that malabsorption can affect many organ systems ( alimentary tract, hematopoietic system, musculoskeletal system, endocrine system, epidermis, nervous system)Concentrate on celiac disease and lactose intolerance as two examples of malabsoption syndrome.
3Malabsorption Syndrome Inability of the intestine to absorb nutrients adequately into the bloodstream.Impairment can be of single or multiple nutrients depending on the abnormality.
4PathophysiologyThe main purpose of the gastrointestinal tract is to digests and absorbs nutrients (fat, carbohydrate, and protein), micronutrients (vitamins and trace minerals), water, and electrolytes.
5Mechanisms and Causes of Malabsorption Syndrome Primary mucosal abnormalities Celiac disease Tropical sprue Whipple's disease Amyloidosis Radiation enteritis Abetalipoproteinemia Giardiasis Inadequate small intestine Intestinal resection Crohn's disease Mesenteric vascular disease with infarction Jejunoileal bypass Lymphatic obstruction Intestinal lymphangiectasia Malignant lymphoma MacroglobulinemiaInadequate digestion Postgastrectomy Deficiency of pancreatic lipase Chronic pancreatitis Cystic fibrosis Pancreatic resection Zollinger-Ellison syndrome Deficient bile salt Obstructive jaundice Bacterial overgrowth Stasis in blind loops, diverticula Fistulas Hypomotility states (diabetes) Terminal ileal resection Crohns' disease Precipitation of bile salts (neomycin)Many causes
6Pathophysiology Inadequate digestion Or Small intestine abnormalities =Malabsorption
7Pathophysiology Inadequate digestion Stomach Pancreas Bile Small intestine abnormalitiesmucosaInadequate small intestineLymphatic obstruction
8Pathophysiology Postgastrectomy Deficiency of pancreatic lipase Inadequate digestionDeficiency of pancreatic lipaseChronic pancreatitisCystic fibrosisPancreatic resectionStomachPancreasBileSmall intestine abnormalitiesObstructive jaundiceBacterial overgrowthStasis in blind loops, diverticulaTerminal ileal resectionmucosaInadequate small intestineLymphatic obstruction
10Malabsorption Syndrome Clinical features There is increased fecal excretion of fat (steatorrhea) and the systemic effects of deficiency of vitamins, minerals, protein and carbohydrates. Steatorrhea is passage of soft, yellowish, greasy stools containing an increased amount of fat. Growth retardation, failure to thrive in children Weight loss despite increased oral intake of nutrients.
11Malabsorption Syndrome Clinical features Depend on the deficient nutrientProteinSwelling or oedemaAnaemias(fatigue and weakness)B12, folic acid and iron deficiencyvitamin D, calciumMuscle crampOsteomalacia and osteoporosisvitamin K and other coagulation factorBleeding tendencies
12Malabsorption Syndrome Clinical features Malabosortion affect many organs Hematopiotic system anemia Musculoskeletal system osteopenia, Muscle cramp Endocrine system amenorrhea, infertility, hyperparathyridism Skin, purpura , dermatitis hyperkeratosis Nervous system, neuropathy
16FECAL FAT ANALYSISStool is collected for 3 consecutive days while the patient is on a diet containing 100 g of fat per day, and the specimen is analyzed for fat content.Normal fat excretion should not exceed 6 g/day.
17Evaluation of Malabsorption D-Xylose Test ( sugar absorbed in small intestine) Measures absorptive capacity of proximal small bowel Distinguishes malabsorption from maldigestion Does not require pancreatic enzymes to be absorbed by an intact small bowel mucosa Enters the blood and is excreted in urine Method: Give 25g D-Xylose; collect urine for 5 hours….Collect blood one hour after ingestion Abnormal result : if xylose is less than 4 g in urine If test abnormal – small bowel biopsy If test normal, maldigestion likely due to pancreatic insufficiency
18Test for pancreatitisThe measurement of pancreatic enzymes in the blood (trypsinogen) or in the stool (chymotrypsin or elastase) is simple and provides helpful laboratory evidence for the diagnosis of moderate to severe pancreatitis.Pancreatic calcifications seen on abdominal films or CT scan indicate the presence of chronic pancreatitis.
19Bile salt breath test– measures orally ingested (14C)bile salt absorption. If terminal ileum is abnormal, bile acid is not absorbed across the terminal ileum, bacteria in colon deconjugate it and 14CO2 diffuses across the colon and is excreted in the breath so the level of 14CO2 in expired air is abnormally high
20A capsule containing the radiolabelled bile salts is taken orally A capsule containing the radiolabelled bile salts is taken orally. Levels are measured at seven day interval. A value less than 15% signifies malabsorption.23-Seleno-25-homo-tauro-cholate scan
21Malabsorption Syndrome Celiac disease An immune reaction to gliadin fraction of the wheat protein glutenUsually diagnosed in childhood – mid adult.Patients have raised antibodies to gluten autoantibodiesHighly specific association with class II haplotypes of HLA DQ2 (haplotypes DR-17 or DR5/7) and, to a lesser extent, DQ8 (haplotype DR-4).
24Clinical features Celiac disease Typical presentation GI symptoms that characteristically appear at age 9-24 months.Symptoms begin at various times after the introduction of foods that contain gluten.A relationship between the age of onset and the type of presentation;Infants and toddlers….GI symptoms and failure to thriveChildhood…………………minor GI symptoms, inadequate rate of weight gain,Young adults……………anemia is the most common form of presentation.Adults and elderly…...GI symptoms are more prevalent
26Celiac Disease Histology Normal Mucosa is flattened with marked villous atrophy.Lamina propria: increase in chronic inflammatory cells.
27Celiac DiseaseDiagnosis Clinical documentations of malabsorption. Small intestine biopsy demonstrate villous atrophy. Improvement of symptom and mucosal histology on gluten withdrawal from diet.wheat, barley, flour
28Gluten free diet for life TreatmentGluten free diet for lifeOther grains, such as rice and corn flour, do not have such an effect.
29Celiac Disease Complications Osteopenia , osteoporosis Infertility in womenShort stature, delayed puberty, anemia,Malignancies,[ intestinal T-cell lymphoma]10 to 15% risk of developing GI lymphoma.
31Lactose Intolerance Pathophysiology At the brush border of enterocyteslactaseLactoseglucose + galactoseLactose IntoleranceLow or absent activity of the enzyme lactase
32Inherited lactase deficiency Lactose IntoleranceInherited lactase deficiencyCongenital lactase deficiencyChildhood-onset and adult-onset lactase deficiencyextremely rarecommonGenetically programmed progressive loss of the activity of the small intestinal enzyme lactase.Gastroenteritis: Infectious diarrhea, particularly viral gastroenteritis in younger children, may damage the intestinal mucosa enough to reduce the quantity of the lactase enzyme.Acquired lactase deficiencyTransientSecondary lactase deficiency due to intestinal mucosal injury by an infectious, allergic, or inflammatory process
33ClinicalBloating, abdominal discomfort, meteorism, and flatulence ……………1 hour to a few hours after ingestion of milk products Stool characteristics: Loose, watery, acidic stool often with excessive flatus and associated with urgency that occurs a few hours after the ingestion of lactose-containing substances is typical.
35Lactose IntoleranceDeficiency/absence of the enzyme lactase in the brush border of the intestinal mucosa → maldigestion and malabsorption of lactose • Unabsorbed lactose draws water in the intestinal lumen • In the colon, lactose is metabolized by bacteria to organic acid, CO2 and H2; acid is an irritant and exerts an osmotic effect • Causes diarrhea, gaseousness, bloating and abdominal cramps
36DiagnosisEmpirical treatment with a lactose-free diet, which results in resolution of symptoms;Hydrogen breath testGenetic testing.Many intestinal diseases cause secondary reversible lactase deficiency, including viral gastroenteritis, celiac disease, giardiasis, and bacterial overgrowth.