8 Malabsorptive Disorders.pdf

Malabsorp)ve Disorders Objec&ves o Differen(ate the e(ologies, presenta(ons, and diagnoses of the various disorders of absorp(on: • Celiac disease • Tropical sprue • Short-bowel syndrome • Bacterial overgrowth syndromes • Whipple’s disease o Evaluate and select appropriate treatment specific to the ty...

Malabsorp)ve Disorders Objec&ves o Differen(ate the e(ologies, presenta(ons, and diagnoses of the various disorders of absorp(on: • Celiac disease • Tropical sprue • Short-bowel syndrome • Bacterial overgrowth syndromes • Whipple’s disease o Evaluate and select appropriate treatment specific to the type of malabsorp(ve disorders o Describe pathogenesis of refeeding syndrome o Manage pa(ents at risk for developing refeeding syndrome Disorders of Absorp-on Classifica&on o Disorders of absorp(on • Diminished intes(nal absorp(on → referred to as malabsorp)on syndrome • Increased intes(nal absorp(on: § Iron → Hemochromatosis § Copper → Wilson’s disease Clinical Presenta&on o Steatorrhea o Diarrhea • Osmo(c diarrhea: Secondary to diminished absorp(on of one or more dietary nutrients § → Suggests malabsorp)on syndrome • Secretory diarrhea: Secondary to small and/or large intes(nal fluid and electrolyte secre(on § → Suggests luminal (e.g., E. Coli enterotoxin) or circula(ng (e.g., vasoac(ve intes(nal pep(de) secretagogue (Mal)absorp&on o Lipids • Integrated processes for absorp(on: § Intraluminal (or diges(ve) phase § Mucosal (or absorp(ve) phase § Delivery (or post-absorp(ve) phase • An abnormality at any site involved in these processes can cause steatorrhea o Carbohydrates • Absorbed only in the: § Small intes(ne § Form of monosaccharides • e.g., Lactose malabsorp(on o Protein • Requires hydrolysis to di- and tripep(des and amino acids before absorp(on • Malabsorp(on of protein that are clinically significant are rarely observed Approach to Management o Iden(fy the likely e(ology • History, symptoms, and ini(al preliminary observa(ons o Recognize that dietary nutrient absorp(on may be segmental or diffuse along the small intes(ne and is site-specific • Calcium, iron, and folic acid: Absorbed by ac(ve-transport processes exclusively in the proximal small intes(ne, especially the duodenum • Cobalamin and bile acids: Absorbed by the ac(ve-transport processes only in the ileum Specific Disease En&&es o Celiac disease o Tropical sprue o Short-bowel syndrome o Bacterial overgrowth syndromes o Whipple’s disease Celiac Disease E&ology and Symptoms o E(ology: Unknown • Environmental factor: Clear associa(on with gliadin • Immunologic factor: Serum an(bodies - IgA an(gliadin, an(endomysial, and an(tTG an(bodies - are present • Gene(c factor: High among whites, low among blacks and Asians o Symptoms: Diarrhea, steatorrhea, weight loss, anemia, and metabolic bone disease o Onset of symptoms: At all points of life Diagnosis and Treatment o Diagnosis: Small-intes(nal biopsy • Symptoms, • Laboratory findings sugges(ve of nutrient malabsorp(on and/or deficiency, and • Posi(ve tTG an(body test o Treatment: Dietary gluten restric(on o Key features of celiac disease: • Abnormal small-intes(nal biopsy • Response (including symptoms and histologic changes on small-intes(nal biopsy) to the elimina(on of gluten from the diet Tropical Sprue E&ology and Symptoms o Incidence: Affects 5–10% of the popula(on in some tropical areas o E(ology: Unknown • Consensus: May be caused by one or more infec(ous agents (e.g., K. pneumoniae, E. cloacae, and E. coli) o Symptoms: Chronic diarrhea, steatorrhea, weight loss, and nutri(onal deficiencies, including those of both folate and cobalamin Diagnosis and Treatment o Diagnosis: Small-intes(nal biopsy • Chronic diarrhea, • Evidence of malabsorp(on, and • Either residing or has recently lived in a tropical country o Treatment: Broad-spectrum an(bio(cs (tetracycline for up to 6 months) and folic acid (induces hematologic remission) Short-Bowel Syndrome Defini&on and Symptoms o Defini(on: Descrip(ve term for the myriad clinical problems that follow resec(on of various lengths of the small intes(ne or, on rare occasions, are congenital o Symptoms: Diarrhea, steatorrhea, enteric hyperoxaluria, gastric hypersecre(on of acid Treatment o Dietary nutrients and calories o Cholestyramine (an anion-binding resin) and calcium • → Useful in reducing hyperoxaluria o Proton pump inhibitors • → Help reduce diarrhea and steatorrhea by inhibi(on of gastric acid secre(on Bacterial Overgrowth Syndrome E&ology and Symptoms o E(ology: • Anatomic or func(onal stasis or • Communica(on between the rela(vely sterile small intes(ne and the colon, with its high levels of aerobic and anaerobic bacteria (e.g., E. coli or bacteroides) o Symptoms: Diarrhea, steatorrhea, and macrocy(c anemia of cobalamin (low serum cobalamin level), and an elevated serum folate level Diagnosis and Treatment o Diagnosis: • Duodenal aspirate for bacterial (ters → not readily available • Breath hydrogen tes(ng with administra(on of lactulose, a nondiges(ble disaccharide • Resolu(on of symptoms with empiric an(bio(c treatment o Treatment: Surgical correc(on • If cannot be corrected surgically: Broad-spectrum an(bio(cs (e.g., tetracycline, metronidazole, amoxicillin/clavulanic acid, rifaximin, and cephalosporins) for ~3 weeks or un(l symptoms remit • For frequent recurrences: An(bio(cs for 1 week per month, whether or not symptoms are present Whipple’s Disease E&ology and Symptoms o E(ology: Tropheryma whipplei, gram-posi(ve bacillus o Symptoms: Diarrhea, steatorrhea, weight loss, arthralgia, and central nervous system (CNS) and cardiac problems • Demen(a: Rela(vely late symptom and an extremely poor prognos(c sign o Onset of symptoms: Insidious Diagnosis and Treatment o Diagnosis: Tissue biopsy of the small intes(ne and/or other organs that may be involved (e.g., liver, lymph nodes, heart, eyes, CNS, or synovial membranes) o Treatment: Prolonged use of an(bio(cs • Cedriaxone or meropenem for 2 weeks followed by oral sulfamethoxazoletrimethoprim (800-160 mg) twice a day for 1 year § If trimethoprim-sulfamethoxazole is not tolerated, chloramphenicol is an appropriate second choice Refeeding Syndrome Poten(ally fatal shids in fluids and electrolytes that may occur in malnourished pa(ents receiving refeeding, resul(ng in hormonal and metabolic changes causing serious clinical complica(ons Risk Factors Malnutri&on/Starva&on Nutri&on Replacement Clinical Manifesta&on o Hypophosphatemia from increase in adenosine triphosphate produc(on o Hypokalemia and hypomagnesemia from glucose and amino acid uptake o Hypernatremia may occur to maintain posi(ve ion homeostasis, leading to fluid reten(on/overload o Thiamine deficiency • Low reservoir from malnutri(on/starva(on • Carbohydrate use for energy produc(on via glycolysis increases thiamine requirements • Increased role as cofactor during nutri(onal replacement to synthesize glycogen, fat, and protein Clinical Management – Baseline Labs o Obtain baseline basic metabolic panel (BMP) with phosphorous and magnesium • If using parenteral nutri(on, obtain baseline hepa(c enzymes, albumin, prealbumin, cholesterol, triglycerides, and coagula(on studies o Obtain baseline weight o Note: Most electrolyte disturbances occur in first 2-3 days of ini(a(ng refeeding but can occur up to 7-10 days later Clinical Management – Replacements o Before start of refeeding • Thiamine and con(nue for 3-5 days • Mul(vitamin with or without iron once daily o At start of refeeding as appropriate • Electrolytes § Orally/enterally: In pa(ents with mild to moderately low levels and a func(oning GI tract § Intravenously: In pa(ents with severely low levels, without func(oning GI tract, do not respond to enteral replacement, where oral replacement is not possible or contraindicated Clinical Management – Nutri&on o Start at 50% (20-75%) of es(mated caloric needs • Highest risk pa(ent (e.g., anorexia nervosa): Start at 25% o Dietary advancement over 3 to 7 days, with caloric increase of 10-25% per day un(l at goal o All calorie sources should be taken into account, including fluids (e.g., D5, D10) and medica(ons (e.g., propofol) Monitoring o I/O with calorie counts o Daily weights • Goal weight gain in adults: 1 kg per week • Goal weight gain in children: undetermined o Daily BMP with phosphorous and magnesium for at least 7 days (then 3 (mes in following week) during refeeding period o If using parenteral nutri(on, weekly hepa(c enzymes, albumin, prealbumin, cholesterol, triglycerides, and coagula(on studies