Malabsorption

Tory Davis, PA-C

To Be Covered Malabsorption overview Small bowel bacterial overgrowth Carbohydrate intolerance Celiac Disease Short Bowel Syndrome Not covered in this lecture: tropical

sprue, Whipple’s disease, secondary causes…look-em-ups

Malabsorption Inadequate assimilation of dietary

substances due to defects in– Digestion– Absorption– Transport

Can affect micronutrients (vits and minerals) or macronutrients (protein/carb/fat)

Malabsorption causes… Increased fecal excretion Nutritional deficiencies Common GI symptoms:

– Diarrhea– Steatorrhea (>6g/d of fat…hallmark of

malabsorption)– Abdominal bloating– Gas– Weight loss– Other specific s/s with each malabsorbed

nutrient

How to figure it out Suspect malabsorption in all patients with

chronic diarrhea, wt loss, anemia Check hx for clues:

– Hx acute pancreatitis? Think chronic panc– Hx lifelong diarrhea exac by gluten? Rash, too?

Think celiac disease– Milk makes them fart? Think lactose intolerance– Had most of their small bowel removed? Think

short bowel syndrome! Okay, duh…

Work-up If you suspect specific cause, test for it

– Details to follow, and more details from Brenda’s lab lectures

And/or check CBC (anemia), ferritin, lytes Confirm malabsorption:

– 72 h fecal fat collection– Sudan III stool stain for fat– D-xylose test (assesses mucosal integrity to

differentiate between mucosa and pancreatic etiology)

Diagnosis of Malabsorption

Endoscopy with small bowel bx Culture small bowel aspirate for bac-t

overgrowth Small bowel xrays to look for anatomical

conditions that may predispose to bac-t overgrowth (fistulas, surgical blind loops, strictures, ulcerations)

Schilling test (B12)

Causes of Malabsorption

Bacterial Overgrowth Syndrome

Usually secondary to anatomic alterations or motility disorders (congenital or acquired) that promote stasis of intestinal contents

Normal small bowel has <105 bact/mL Low count maintained by peristalsis,

gastric acid, mucus, intact ileocecal valve function

What Extra Bacteria Do Consume nutrients, especially B12 and

carbs– B12 (cyanocobalamin) deficiency– Calorie deprivation/weight loss

Produce folate, so this is NOT a cause of folate deficiency (folate def causes macrocytic anemia)

Deconjugate bile salts– Fat malabsorption– Steatorrhea and diarrhea

Bac-t Overgrowth Dx Frequently, empiric antibiotic therapy

resulting in improvement is basis for diagnosis…but abx can worsen many conditions on the ddx

Better: quantitative culture of intestinal fluid. Look for bac-t count>105/mL

Or C-xylose breath test (less invasive)

Bact Overgrowth Tx 10-14 days oral abx

– Tetracycline– Amox/clavanulate– Cephalexin– TMP/SMX– Metronidazole

Correct underlying condition Correct nutritional deficiencies

Carbohydrate Intolerance Inability to digest certain carbs due to lack of

one or more enzymes Sx: watery diarrhea, abdominal distention,

flatulence, nausea, borborygmi, abd cramping (hooray for lactaid!)

Etiology:– Acquired (primary)– Secondary – Congenital (rare)

Lactase Deficiency Primary adult hypolactasia Most common carb intolerance Lactase normally in high levels in

neonates but decrease after weaning in most ethnic groups– 80% blacks and hispanics– Near 100% Asians– Only 15-20% Caucasians

Lactose intolerance So, 75% of the world adult population

lacks lactase, and we call it abnormal…

Secondary Lactase Deficiency

Seen with small bowel mucosal damage, such as in celiac disease, acute small bowel infections, tropical sprue

Dx/Tx Dx by:

– Careful hx– Dietary challenge

– H2 breath test

Tx with:– Lactose avoidance– Lactase supplements– Ca+ supplements

Celiac Disease Aka:

– Celiac Sprue– Non-tropical sprue– Gluten Enteropathy

Immunologically mediated disease caused by intolerance of gluten, which causes mucosal inflammation and malabsorption

Celiac Hereditary insensitivity to gliadin fraction of

gluten Gluten-sensitive T cells activated by

exposure, cause inflammatory response…leads to mucosal villous atrophy and crypt hyperplasia

N. America 1/5000, (1/150 in SW Ireland) Female 2:1 male

Presentation There is no typical Infants

– Sx appear after cereals intro’d– FTT (failure to thrive), anorexia, pallor,

hypotonia, abdominal distention Older kids

– Anemia, growth delays, anorexia, diarrhea

Adults Anorexia, weakness, Diarrhea, steatorrhea, Anemia Glossitis, angular stomatitis, aphthous

ulcers Decreased fertility Lactose intolerance (Why?)

– Will lactose avoidance help the sx? Evidence of Ca/vit D (like what?) Dermatitis herpetiformis (10%)

Diagnosis Clinical suspicion

– Use clues like unexplained Fe deficient anemia FHX Labs

– 72 hr fecal fat– D-xylose absorption test– Tissue transglutaminase (IgA)– Anti gliaden antibody (IgA)– Anti reticulin antibody (IgA)– Total IgA (check to make sure there is no IgA

deficiency)– Antibody levels decrease with gluten-free diet,

so you can use this to determine if the pt is really following the diet

Small Bowel Biopsy Not specific Villous atrophy

– Lack of or shortening of villi Increased epithelial cells Crypt hyperplasia

Celiac Treatment Gluten free diet

– No wheat, rye, barley or anything that has gluten in it

– No breads, bagels, pastries, pasta and pizza – Gluten used as thickener frequently, so need

education to facilitate avoidance– Must do dietitian referral, advise support group

Sx will resolve in 1-2 weeks (usually)

Prognosis & Complications

Prog 10-30% mortality without tx Complications:

– Intestinal lymphomas– Refractory disease– Increase in other GI malignancies

Short Bowel Syndrome Malabsorption due to extensive small

bowel resection (often because of Crohn’s, mesenteric infarction, radiation enteritis)

Symptom severity depends on length and function of remaining bowel

Diarrhea and nutritional deficiencies

Jejunum Primary digestive and absorptive site

for most nutrients BUT If removed, the ileum will adapt by

changing villous structure Gradual clinical improvement as

adaptive process continues

Ileum Primary site for B12 and bile acid

absorption No compensatory mechanism for loss

of ileum Malabsorption of fats, fat-soluble

vitamins, and B12 Bile acids in large intestine cause

secretory diarrhea

SBS Tx Small feedings Anti-diarrheals TPN if needed