tbl 3 clinical: malabsorption/ maldigestion, celiac disease and short bowel syndrome Flashcards
- Malabsorption – impaired absorption of nutrients
o Can occur when there is impairment of transport of nutrients across the _____________ or impairment in the transfer of nutrients into the systemic circulation after absorption into the enterocytes e.g. ___________, abetalipoproteinemia - Maldigestion – impaired digestion of nutrients within the intestinal lumen or at the terminal digestive site of the brush border membrane of _________
- Although malabsorption and maldigestion are pathophysiologically distinct, the processes underlying digestion and absorption are interdependent – in clinical practice, the term malabsorption has come to denote derangements in either process
o Malabsorption can occur from any defect or defects at one or more of the nutrient digestion and absorption processes – such as at __________, at absorption into the intestinal mucosa and at transport into the systemic circulation
apical membrane of enterocytes; intestinal lymphangiectasia; mucosal epithelial cells; luminal processing
[Fat malabsorption]
Fats – most dietary fats are absorbed in the ________________.
- Important components needed for the digestion and absorption of fats
o Fat emulsification – begins in the upper GI tract through _________ and gastric mixing
o Fat hydrolysis with pancreatic lipase and colipase, pancreatic bicarbonate – raises intraluminal pH to 6.5, ideal for fat digestion
o Bile salts – enhance fat solubilisation by forming micelles and liposomes which are then absorbed into the enterocytes, where they are processed into _________ and transported to the intestinal lymphatics to enter the systemic circulation
proximal 2/3 of the jejunum; mastication; chylomicrons;
Disturbances in any of the steps in fat assimilation can lead to fat malabsorption and steatorrhea
These include:
- Pancreatic exocrine insufficiency – Impaired production of pancreatic lipase, _______, and bicarbonate of a degree significant enough to cause fat malabsorption may occur in patients with chronic pancreatitis and pancreatectomy.
- Extensive small bowel resection can lead to a significant decrease in absorptive surface, resection of >100cm of TI common results in severe impairment of ______________ of bile salts such that the liver ability to upregulate the de novo bile acid synthesis is inadequate to meet the normal physiological needs for bile production, and _________ where significant lengths of small intestines are bypassed, can all lead to fat malabsorption.
- Small intestinal bacterial overgrowth – ___________ of bile acids by florid small bowel bacterial overgrowth defunctionalizes the bile acids, and can also result in fat malabsorption
- Inadequate synthesis of bile acid (e.g., cirrhosis) or secretion of bile salts (e.g.,
cholestasis) can result in fat malabsorption due to inadequate _______ formation.
However, fat malabsorption is usually mild in these cases. - Other causes of fat malabsorption include ___________ that decreases the amount of absorptive surface, inadequate synthesis or defective structure of _________ necessary for the packaging of chylomicrons in abetalipoproteinemia, impairs their secretion into the lymphatics, or abnormalities in lymphatic flow for example in intestinal lymphangiectasia, will impair their ability to reach the systemic circulation.
colipase; enterohepatic circulation; gastric bypass surgery
Deconjugation; micelle
diffuse small bowel disease; apoproteins;
[Carbohydrate Malabsorption]
Dietary starch (amylose and amylopectin), and disaccharides ______________ are the most abundant digestible carbohydrate in the human diet, and they must be broken down into monosaccharides prior to absorption.
Important components needed for carbohydrate digestion include salivary and pancreatic amylase & brush border __________. Hence, carbohydrate malabsorption may result from deficiency in pancreatic amylase in patients with chronic pancreatitis or pancreatectomy. When there is a reduction in
specific disaccharidase activity, such as acquired _____ deficiency resulting in lactose intolerance,
When there is a decrease in small bowel absorptive surface from surgery or diseases likely celiac disease, or when there’s increase ingestion of unabsorbable carbohydrates such as ______, resulting in diarrhoea.
sucrose and lactose; disaccharidases; lactase; sorbitol
[Protein malabsorption]
Protein digestion begins in the stomach with conversion if pepsinogen into pepsin at low pH, and continues in the duodenum, by pancreatic proteases, such as __________, and peptidases in pancreatic juice, brush border and cytoplasm of intestinal cells.
Protein malabsorption can occur when pancreatic __________________ secretion is impaired such as in chronic pancreatitis or cystic fibrosis. And can also occur in diseases associated with a generalised reduction in intestinal absorptive surface such as celiac disease or after surgery.
trypsin and chymotrypsin; bicarbonate and protease
[Malabsorption: Vitamins and minerals]
The ________ of the small intestine is the predominant site for the absorption of most vitamins and minerals. A notable exception is vitamin B12, which is absorbed at the terminal ileum by a specific ileal receptor that recognizes the B12-intrinsic factor complex. Calcium, iron and ______ are predominantly absorbed in the upper small intestine, and deficiencies are a common consequence of expanded proximal small bowel resections and disease.
The terminal ileum is the site of b12 absorption and re-absorption of bile salts in the enterohepatic circulation of bile salts.
- > 100cm of distal ileal resection is associated with high risk of b12 deficiency
- Distal ileum resection is also associated with ____ malabsorption, which enters the colon and stimulates colonic water and electrolyte secretion, resulting in diarrhoea.
- Fat soluble vitamins A, D, E and K requires solubilisation in a mixed micellar phase to be absorbed. - Factors that affect fat absorption will also affect the absorption of these vitamins as well.
- Fatty acids that are not absorbed binds to _________ resulting in increase loss and deficiency.
Intestinal absorption of copper is inhibited by excessive _______ and can result in copper deficiency.
proximal half; folate
bile salt ;
ca and mg ;
zinc replacement
Common causes of malabsorption include celiac disease, in particular, in __________ patients.
- Small bowel bacterial overgrowth, as a result of gastric surgery and resultant _________, intestinal blind loops post surgery. Also in patients with _________, intestinal strictures from various causes including crohn’s disease, fistulas, impaired small intestinal peristalsis, for e.g. in patients with scleroderma.
- Pancreatic insufficiency from chronic pancreatitis and post pancreatectomy.
Caucasian and Indian; achlorhydria; jejunal diverticula
Less common causes of malabsorption include:
- _________ after intestinal resection for crohn’s disease and ischemic bowel,
- Chronic infections such as _______ and TB
- Small intestinal lymphoma
- Radiation enteritis
- Intestinal lymphangiectasia from various causes
- Drugs such as orlistat, laxatives and __________
- Eosinophilic enteritis
- And lastly immunodeficiency which can be congenital or acquired.
Short bowel syndrome; tropical sprue; cholestyramine
[Malabsorption- clinical features]
- The classic manifestations for malabsorption are chronic diarrhoea from fat or cho malabsorption and unintentional weight loss due to calorie malnutrition
- Patients with fat malabsorption present with stools that are pale, greasy and floating, which can be highly subjective and not as specific seeing oil droplets seen in stool. On the other hand, patients with carbohydrate malabsorption presents with __________, with bloating, and excess ________
Specific nutrient deficiencies may be the predominant clinical feature:
- For example, In patients with hypoalbuminemia from protein-calorie malnutrition, patients may present with peripheral edema, abdominal distension from ________ and shortness of breath from ______.
Dermatitis may be seen in patients with vitamin B, ____ and essential Fatty acids deficiencies.
Glossitis and _______ is suggestive of vit B deficiency.
While Bony aches and pain may be a predominant complaint for pts with vitamin dvdeficiency. Patients with hypocalcemia may just complain of muscle spasms and parasthesia.
And pts with b12 and thiamine deficiency may present with ___________.
watery chronic diarrhoea; flatus;
ascites, pleural effusion;
Zn ;
cheilosis;
peripheral neuropathy
[Malabsorption: Laboratory Findings]
- The malabsorption of fat is the most commonly used indicator of global malabsorption as it tends to be the most sensitive among the macronutrients (fat, carbohydrates, and protein) to have interference from disease processes.
- Since it is the most ___________ macronutrient, its malabsorption is a critical factor in the weight loss that often accompanies malabsorptive disorders.
- Begin with a qualitative assessment for fecal fat on a single specimen using ________, which is inexpensive, easy to perform and a good screening test. If the qualitative test is positive, a quantitative assessment of fecal fat can be performed when available and a stool fat of >___ over a 72hr period while consuming at least 60g of fat daily during the test is confirmatory for fat malabsorption. Patients with fat malabsorption may have deficiencies of the fat soluble vitamins as well.
- A low serum _________, a low 25-hydroxyvitmin D, a low serum ___________ levels and prolonged prothrombin is indicative of deficiencies of vitamin A, D, E and K respectively.
- Intestinal protein loss is suggested by a low serum albumin and protein levels, and confirmed with an increased stool ___________ clearance. Do remember to exclude urinary protein loss (Proteinuria), inadequate synthesis in patients with chronic liver disease and inadequate intake (poor nutrition).
- Low levels ca, mg and Zn, a ______________ anemia suggestive of iron deficiency. And a ________ anemia may be due to folate or b12 deficiency.
calorically dense
Sudan III stain; 7g
retinol/carotene; alpha-tocopherol;
alpha 1 anti-trypsin
hypochromic microcytic; macrocytic
[Malabsorption: evaluation to determine etiology]
To establish the diagnosis of pancreatic exocrine insufficiency, an indirect test of pancreatic function can be performed with __________. If the tests is inconclusive and clinical suspicion remains high, direct pancreatic function testing with _________ can be performed if available. Otherwise, a trial of pancreatic enzyme supplement can be used to see if symptoms, steatorrhoea improves. In patients with confirmed pancreatic exocrine insufficiency, imaging of the pancreas with CT, MRI or endoscopic ultrasound can help to diagnose ___________ and to exclude malignancy.
Small intestinal bacteria overgrowth is supported by a positive ______________. If breath test is not available, a trial of antibiotics may be attempted again to see if symptoms improve with antibiotic therapy.
Radiological imaging of the small bowel can help establish the etiology of malabsorption by identifying mucosal abnormalities, and anatomical abnormalities such as diverticulosis.
Both upper and lower endoscopy may demonstrate endoscopic features that may suggest the presence of an underlying cause of malabsorption, but biopsies are required to establish the diagnosis. Bxs are often taken from the duodenum/jejunum and distal ileum and colon and can help exclude diseases such as cd, celiac disease and small bowel lymphoma.
Serological testing with ___________ and _______________ for celiac disease may be considered in at risk population.
fecal elastase; secretin test; chronic pancreatitis
glucose or lactulose breath test
tissue transglutaminase IgA; deaminated gliadin peptide IgG
[Lactose intolerance]
Lactose intolerance is a clinical syndrome in which lactose ingestion causes symptoms of abdominal pain, _______, flatulence and diarrhoea, due to lactose malabsorption.
This is most commonly due to lactase enzyme non persistence, that is, acquired lactase deficiency, which is common in Asians and African populations. With acquired lactase deficiency, the lactose malabsorption rates are low in children <6yrs old, but as the levels of lactase decreases with age, lactose malabsorption rates increases as well.
Malabsorption of lactose may be secondary to underlying intestinal disease such as infection or inflammation which damages intestinal epithelium and results in decrease digestive activity as lactase is usually the first disaccharidase to be affected due to its _________________.
In lactose malabsorption, the undigested lactose rapidly passes into the colon, where it is converted by bacteria to Hydrogen, carbon dioxide and short chain fatty acids, resulting in the clinical symptoms of lactose intolerance.
bloating; distal location on the villi.
[Lactose intolerance: diagnosis]
A presumptive diagnosis of lactose intolerance can be made in otherwise healthy patients with mild symptoms that occur with significant lactose ingestion. And Resolution of symptoms after ________ of avoidance of lactose-containing foods.
A __________ with simultaneous assessment of symptoms can be used to confirm lactose malabsorption and intolerance in patients who have a low probability of being lactase nonpersistent based on ethnicity (e.g., Caucasian pts).
Patient diagnosed with lactose intolerance should be advised to restrict their intake of lactose, sufficient to avoid symptoms of intolerance. Pt may also take lactose reduced products and take lactase supplements. Levels of ca and vitamin D should be monitored in those who avoid dairy intake and supplemented when indicated.
five to seven days;
lactose hydrogen breath test
Pernicious anemia is an autoimmune condition. Characterised by the presence of autoantibodies, anti intrinsic antibody and anti parietal cell antibody. And maybe associated with other autoimmune conditions such as _________ and type 1 Diabetes.
Anti intrinsic factor antibody binds to intrinsic factor and prevents the formation of ___________, and in turns decreases the absorption of b12 at the terminal ileum, resulting in b12 deficiency.
Anti parietal cell antibody results in ____________, characterised by the destruction of parietal cells, which are replaced by atrophic and metaplastic mucosa in the gastric body, increasing the risk of ______________.
The resultant achlorhydria causes _____________. The chronic stimulation of enterochromaffin cells by the elevated gastrin levels increases the risk of _______________. Hence, it is recommended that a screening upper endoscopy should be performed at the time of diagnosis of PA.
autoimmune thyroid disease; vitb12-Intrinsic factor complex
autoimmune atrophic gastritis ; gastric adenocarcinoma
compensatory hypergastrinemia; gastric neuroendocrine tumor
Bile salts that are not absorbed in the ileum enters the colon, where they stimulate electrolyte and water secretion, increase intestinal motility, resulting in symptoms of diarrhoea, bloating and urgency.
Treatment with bile acid sequestrants such as ___________ are usually very effective.
Bile acid malabsorption have been categorized into 3 types:
- In Type I, BAM is related to ____________ and impaired reabsorption, due to ileal resection or inflammation from ileal CD.
- In Type 3 BAM, pts have : Other gastrointestinal disorders that can affect BA absorption, such as postcholecystectomy state, small intestinal bacterial overgrowth, celiac disease, and chronic pancreatitis
- In Type 2 BAM there is an absence of ileal or other obvious gastrointestinal disease, but patient’s chronic diarrhoea responds to ____________, for e.g. in some patients with diarrhoea predominant IBS. Some studies have suggested that there may be an overproduction of BA in type 2 BAM.
cholestyramine;
Ileal dysfunction;
bile acid sequestrants
