Dz that involves epithelium or mucosa itself.
D-xylose is a water soluble, non-metabolized pentose
MALABSORPTION that is absorbed mainly in the duodenum and
Intestinal tract optimized for absorption of nutrients. jejunum. No intraluminal handling. No pancreatic
Have high surface area. Cylinder folds villi enzymes needed. Will normally absorb across
microvilli. Large surface area. Problems if epithelium. Assimilation of this sugar does not
compromise that surface area. If have decrease will require the intraluminal pancreatic stage of digestion.
take longer to absorb that nutrient. Mostly Ca and Fe Abnormal test: SI mucosal disease histological
Jejunum: Absorbed most nutrients. examination of the mucosa by biopsy. Also with
Ileum: bile acid and Vit B-12. Restricted to ileum. Can the small intestinal bacterial overgrowth.
be passively absorbed. Active reabsorption is in Normal test: deficiency of intraluminal (pancreatic)
ileum. If malabsorb bile bile acids in colon digestive enzymes or bile acid deficiency.
diarrhea. Vit B-12 anemic.
PABA Test to Evaluate Pancreatic function
Test is done w/PABA and an attached tripeptide. If
Arise from disorders of intraluminal events (e.g. have exocrine function then will cleave off
deficiency of pancreatic digestive enzymes or bile tripeptide.
acids), disorders of events at the cell surface (e.g. Normal function: Ingest PAPA-tripeptide tripeptides
lack of specific cell-surface enzymes, cleaved liberating PAPB which is absorbed
oligosaccharide deficiencies, specific transport excreted in urine.
defects, glucose-galactose malabsorption and amino Abnormal: no cleavage of tripeptide. Is absorbed, but
acid transport defects), abnormally of cellular events PABA is not excreted in urine.
(e.g. mucosal injury in celiac sprue, defects in Causes of pancreatic exocrine sufficiency:
intracellular chylomicron synthesis in Chronic or hereditary pancreatitis
Abetalipoproteinemia) or abnormalities in post- Pancreatic cancer
cellular events (e.g. intestinal lymphangiectasia). Operative resection
Pancreas: enzymes that breakdown fat. End up with Ductal stricture or fistula
number of proteolytic enzymes. Also amylase to CF
breakdown carbohydrate. Protein-calorie malnutrition
Bile Acids: Cannot absorb fat without bile acids. What Isolated enzyme deficiency.
can go wrong. Most easily is fat absorption. Needs
this extra stage. May not make if liver is dz, bile Small intestinal x-ray
duct obstruction, breakdown of bile acids before may reveal typical changes of mucosal pathology,
secreted. internal fistulae, blind loops, diverticulae or motility
Brush border in jejunum: enzyme dysfunction disorders which might be associated with bacterial
dysfunction of lactase. Also inherited defects overgrowth. It may also reveal ileal inflammatory
glucose, galactose malabsorption. disease (e.g. regional enteritis) responsible for bile
Transport monosaccarides. Fat taken up by acid and/or vitamin B12 malabsorption.
lymphatics. If have dz that affects lymphatics Chronic pancreatitis: Output below normal. Low lipase
(radiation, TB with blocked LN.) Do not deliver to --. Low absorption of
Small bowel (jejunal) biopsy
A- lipoproteinemia: fat will hang up within epithelial
cell. Diagnosis of intestinal mucosal dz. Specific diagnostic
Clinical Presentation 1. changes in the architecture of villi and crypts: normal
1. Diarrhea or steatorrhea ratio of 4 to 1 Physiologic inflamed (normal). See
2. Weight loss some intraepithelial lymphocytes and plasma cells
3. Evidence of Vit deficiency with occasional eosinophil and mast cell. Should see
D: Osteomalacia, psuedofractures, tetany some CD4 cells. Celiac Dz.
K: Bleeding tendency 2. cellular changes in the epithelium
B: Cheliosis, glossitis 3. specific types of cellular infiltration in the lamina
Folate B-12: anemia, neuropathy. propria
4. as well as inclusions of bacteria or abnormalities of
Tests of Malabsorption the lymphatics.
Several tests are available to pinpoint the specific B12 absorption test (Schilling test)
defects responsible for malabsorption. Since fat Oral dose of radioactive cobalt-labeled B12 w/or w/out
absorption is vulnerable to defects in either IF. Measures the % or orally ingested isotope
intraluminal digestive enzymes or defects at the excreted in the urine.
mucosal absorptive surface, the demonstration of 1. Abnormal B12 absorption alone: IF deficiency
steatorrhea by qualitative or ultimately quantitative (classical pernicious anemia). Gastric atrophy
(72 hours) fecal fat measurement is the major 2. Abnormal vitamin B12 and IF: bacterial overgrowth
criterion for establishing the presence of fat or with disease of the ileum. If bacterial overgrowth
malabsorption. From there, a logical sequence of of the small intestine is. responsible for the abnormal
tests should lead to the establishment of a specific test, antibiotic therapy will return the test to normal.
Other Tests for Malabsorption
Quantitative Fecal Fat Excretion Pancreatic Function Tests. The secretin test is used to
Anything that causes malabsorption will cause problems measure secretory capacity of the exocrine pancreas.
w/fat absorption first. After administration of secretin, bicarbonate
Sudan staining: look for fat globules concentration is measured in the juice aspirated from
Quantitative Fecal Fat excretion: the duodenum.
Pt placed on 100 gram/day fat diet for 3 total days. Nl Measurements of serum iron, calcium, cholesterol,
excrete ~ 3-5 grams fat/day. > 15 grams excretion folate and vitamin B12 often are used as screening
over the 3 days is (+) result 2 SD > normal mean. tests for malabsorption, but are not specific.
Can easily get false positive: Poor food intake, Prothrombin Time. If prolonged, may reflect
constipation, forgot to collect stool. Eating nuts that malabsorption or liver disease. These possibilities
cause fat in stool. can be distinguished by measuring the response to
D-Xylose Absorption-Excretion Test parenterally administered vitamin K.
Serum Carotene. Carotene is a fat-soluble substance the macrophages may, in fact, represent
present in yellow vegetables and fruits, eggs, etc. degenerating bacilli.
Serum carotene levels tend to be depressed in EM: rod-shaped bacilli can be demonstrated in
patients with fat malabsorption, but can be decreased the lamina propria beneath the absorptive cells.
also if the intake of dietary carotene is low. Treatment: antibiotics.
Differential Diagnosis 1. Rare disease which begins in childhood, often before
the age of one.
Crohn’s dz fat malabsorption
Eosinophilic gastroenteritis hypolipidemia
Infection: Cryptosporidium, Isospora, Girardia, MAC. acanthocytosis of the red blood cells
Lymphangiectasia cerebellar ataxia
Lymphoma "atypical" retinitis pigmentosa.
Mastocytosis 3. Patients have an inability to make the protein-
Whipple’s disease. phospholipid-cholesterol coating of chylomicrons so
the epithelial cells become laden with triglycerides.
Celiac Disease (Gluten-Sensitive 4. On histology
Enteropathy) the villi are normal in shape
1. Precipitated by the ingestion of wheat, rye, and abundance of lipid droplets in the mucosal cells at
barley. Activated by alcohol soluble proteins in the tips of the villi.
wheat, rye, and barley which are termed gliadins, No fat is found in the intracellular spaces and
secalins, and hordeins, respectively. Rich in lacteals of the submucosa and lamina propria.
glutamine and proline. Results in malabsorption. 5. Malabsorption usually is confined to fat. The liver
2. Wide spectrum of dz manifestations. biopsy can also show infiltration of triglycerides.
3. HA associated dz: Dz susceptibility is associated
with the presence of HLA class II DQ sub-region
alleles DQA1 *0501, DQB 1*0201. These alleles can Intestinal Lymphatic Obstruction
be present in cis or trans and encode an HLA DQ2 1. Obstruction to the flow of lymph from SI dilation
molecule which appears to be necessary, but not of the intestinal lymphatic vessels in the villi,
sufficient, for the phenotype expression of this submucosa, serosa, and mesentery. The intestinal
disease (i.e., these alleles are also present in lymph that may leak from ruptured lacteals contains
approximately 20% of healthy Caucasians). Peptide plasma proteins, chylomicrons and small
binding of specific HLA. Peptide from glydins that lymphocytes. Cells look normal.
bind to MHC II and activation of pathogenic T cells. 2. This disorder causes abnormalities in the delivery
4. Intestinal Histology: villous atrophy: loss of villi. phase of absorption.
Will only see entrance to crypts. Increased crypt Acquired: 2 to retroperitoneal disease,
depth: only crypt. Actively proliferating. Abnormal lymphoma, radiation enteritis, abdominal
surface epithelial cells. Lymphocyte and plasma cell tuberculosis, etc.
infiltrate of the lamina propria and an increased Congenital
density of T lymphocytes in the intraepithelial congenital and acquired forms cannot be
region. distinguished by small intestinal biopsy alone.
5) The lesion is most severe in the duodenum and 3. Findings:
jejunum. Although the histological lesion is low albumin
characteristic of this disease, it is not totally specific low Ig level due to gastrointestinal protein loss
since similar lesions can be seen in other diseases low lymphocyte levels due to lymphocyte loss in
such as tropical sprue, small intestinal lymphoma, the gut.
Zollinger-Ellison syndrome and, in some instances, Individuals do not absorb chylomicrons due to the
common variable immunodeficiency syndromes. lymphatic obstruction.
6) Diagnosis: Can see similar picture in soy allergy.
Gut can only respond in a few number ways to insult. Common Variable Immunodeficiency
Demonstrating malabsorption (Hypogammaglobinemia)
Documenting the presence of the typical mucosal 1. As many as 60% of patients with common variable
lesion immunodeficiency have diarrhea, and 20- 30% have
Observing a prompt clinical response and mild to moderate malabsorption.
improvement in mucosal histology upon 2. The biopsy can vary from normal to having partial
withdrawal of the offending proteins from the villous atrophy, similar to that of celiac disease,
diet. except for a lack of plasma cells in the lamina
Whipple's Disease 3. Girardia Lamblia, often is found in the small
Occurs in 4th and 5th decades, w/ incidence in (:, intestinal aspirates of patients with this disorder.
approximately 9:1). Treatment of Girardia infection usually reverses the
Cause: Bacterial: Tropheryma Whippelii malabsorption and villous abnormalities.
Clinical Presentation: 4. Biopsy: lacks normal numbers of plasma cells.
malabsorption 5. Nodular lymphoid hyperplasia of the small intestine
fever, increased skin pigmentation, anemia, occurs in as many as 60% of patients, but does not
lymphadenopathy, arthralgias and arthritis, as correlate with the presence of diarrhea or
well as occasional central nervous system malabsorption.
symptoms. Intestinal Lymphoma
1. May be 1* or 2* to lymphoma arising elsewhere. 1*
Villi are broad and flat
lymphoma can be localized to a short segment of the
Lamina propria contains dilated lymphatics: Do
bowel, it can be multifocal or diffuse, and can cause
not look quite right.
a disease in the delivery phase of absorption.
Foamy macrophages which stain (+) with PAS 2. The ileum and jejunum are among the most frequent
stain. Not much staining in normal pt. sites of involvement, the duodenum being less
Glycoprotein in macrophages lights up. Want to involved.
do this SI not colon. The PAS-positive material in
3. 1* diffuse lymphoma involving the proximal small
intestine is found in individuals in the Middle East,
particularly Arabs and non-European Sephardic
Jews. They can present with malabsorption, but also
have abdominal pain, anorexia and fever. Early in the
disease, there may be partial villous atrophy and the
cellular infiltrate in the lamina propria consists of
benign appearing plasma cells. Later malignant
changes ensue with atypical plasma cells and
reticulum cells. A number of these individuals have
"-heavy chain" disease in which their serum and
intestinal secretions contain an excess quantity of
free-chains of the IgA molecule that frequently have
a deletion in the normal amino acid sequence