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Questions and Answers
Which of the following is a common viral cause of diarrhea lasting less than 2 weeks?
Which of the following is a common viral cause of diarrhea lasting less than 2 weeks?
- Cholera
- Shigella
- Viral (correct)
- ETEC
Campylobacter is classified as a secretory organism causing diarrhea lasting over 4 weeks.
Campylobacter is classified as a secretory organism causing diarrhea lasting over 4 weeks.
False (B)
What type of diarrhea is characterized by abdominal cramps, fever, and blood in the stool?
What type of diarrhea is characterized by abdominal cramps, fever, and blood in the stool?
Invasive organisms
Diarrhea lasting longer than 4 weeks may include a type known as __________ colitis.
Diarrhea lasting longer than 4 weeks may include a type known as __________ colitis.
Match the type of diarrhea with its description:
Match the type of diarrhea with its description:
What role do Brunner's glands play in the digestive system?
What role do Brunner's glands play in the digestive system?
The body pool of bile acids is maintained by the enterohepatic circulation.
The body pool of bile acids is maintained by the enterohepatic circulation.
What are the primary components formed when triglycerides are broken down during fat absorption?
What are the primary components formed when triglycerides are broken down during fat absorption?
During fat absorption, bile acids are conjugated with _______ or taurine in the liver.
During fat absorption, bile acids are conjugated with _______ or taurine in the liver.
Match the following components of the intestinal wall with their functions:
Match the following components of the intestinal wall with their functions:
What is a common etiology of small intestinal diarrhea?
What is a common etiology of small intestinal diarrhea?
In large intestinal diarrhea, pus, blood, or mucus is typically absent.
In large intestinal diarrhea, pus, blood, or mucus is typically absent.
What symptom is present in both small and large intestinal diarrhea?
What symptom is present in both small and large intestinal diarrhea?
In small intestinal diarrhea, the stool odorous finding is likely to be __________.
In small intestinal diarrhea, the stool odorous finding is likely to be __________.
Which of the following symptoms is typically absent in small intestinal diarrhea?
Which of the following symptoms is typically absent in small intestinal diarrhea?
Match the following features with small or large intestinal diarrhea:
Match the following features with small or large intestinal diarrhea:
Weight loss is commonly absent in large intestinal diarrhea.
Weight loss is commonly absent in large intestinal diarrhea.
Name one symptom that may be present in small intestinal diarrhea but rare in large intestinal diarrhea.
Name one symptom that may be present in small intestinal diarrhea but rare in large intestinal diarrhea.
Which type of diarrhea is most commonly seen in children?
Which type of diarrhea is most commonly seen in children?
Type 6 stools indicate severe diarrhea according to the Bristol stool chart.
Type 6 stools indicate severe diarrhea according to the Bristol stool chart.
What is the maximum absorption site for nutrients in the body?
What is the maximum absorption site for nutrients in the body?
Most calorie-dense nutrient is ____.
Most calorie-dense nutrient is ____.
Match the following Bristol stool types with their descriptions:
Match the following Bristol stool types with their descriptions:
Which of the following organisms is associated with secretory diarrhea?
Which of the following organisms is associated with secretory diarrhea?
Secretory diarrhea shows an increased osmotic gap in the stool.
Secretory diarrhea shows an increased osmotic gap in the stool.
Name one tumor associated with secretory diarrhea.
Name one tumor associated with secretory diarrhea.
Patients with secretory diarrhea may experience __________ as a result of electrolyte loss.
Patients with secretory diarrhea may experience __________ as a result of electrolyte loss.
Match the following features with the type of diarrhea:
Match the following features with the type of diarrhea:
Which enzyme is responsible for activating trypsinogen?
Which enzyme is responsible for activating trypsinogen?
Cystinuria is associated with a defect in the transport of dibasic amino acids.
Cystinuria is associated with a defect in the transport of dibasic amino acids.
Name a congenital cause of lactose intolerance.
Name a congenital cause of lactose intolerance.
Lactose is broken down into ________ and galactose by the enzyme lactase.
Lactose is broken down into ________ and galactose by the enzyme lactase.
Match the following conditions or defects with their effects:
Match the following conditions or defects with their effects:
Which of the following is the hallmark symptom of malabsorption?
Which of the following is the hallmark symptom of malabsorption?
The 72-hour fecal fat test is a qualitative measure of fat excretion in stools.
The 72-hour fecal fat test is a qualitative measure of fat excretion in stools.
What is defined as diminished intestinal digestion and absorption of one or more nutrients?
What is defined as diminished intestinal digestion and absorption of one or more nutrients?
Passing of pale, bulky, fatty, malodorous, greasy stools is known as __________.
Passing of pale, bulky, fatty, malodorous, greasy stools is known as __________.
Match the following investigations with their descriptions:
Match the following investigations with their descriptions:
What is the primary site for maximum nutrient absorption in the small intestine?
What is the primary site for maximum nutrient absorption in the small intestine?
The distal part of the small intestine primarily absorbs bile acid and Vitamin B2.
The distal part of the small intestine primarily absorbs bile acid and Vitamin B2.
What type of cells surround the villi in the small intestine?
What type of cells surround the villi in the small intestine?
The continuous renewal of the mucosal layer in the small intestine occurs every _____ hours.
The continuous renewal of the mucosal layer in the small intestine occurs every _____ hours.
Match the following cells in the small intestine with their functions:
Match the following cells in the small intestine with their functions:
What is primarily affected in chronic pancreatitis?
What is primarily affected in chronic pancreatitis?
Bile acid defects can include issues with synthesis and early deconjugation in the small intestine.
Bile acid defects can include issues with synthesis and early deconjugation in the small intestine.
Name one condition associated with defects in small intestinal mucosal integrity.
Name one condition associated with defects in small intestinal mucosal integrity.
In the post-mucosal phase of absorption, long-chain fatty acids are transported via intestinal lymphatics to form _______.
In the post-mucosal phase of absorption, long-chain fatty acids are transported via intestinal lymphatics to form _______.
Which enzyme is responsible for breaking down lactose?
Which enzyme is responsible for breaking down lactose?
Match the conditions to their associated defects in absorption:
Match the conditions to their associated defects in absorption:
The primary transport mechanism for glucose and galactose in the gut is facilitated diffusion.
The primary transport mechanism for glucose and galactose in the gut is facilitated diffusion.
Name the condition caused by a defect in SGLT1.
Name the condition caused by a defect in SGLT1.
The enzyme ________ breaks down sucrose into glucose and fructose.
The enzyme ________ breaks down sucrose into glucose and fructose.
Match the following carbohydrate absorption mechanisms with their corresponding transporters:
Match the following carbohydrate absorption mechanisms with their corresponding transporters:
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Study Notes
Approach to Diarrhea
- Diarrhea is defined as stool water content > 200mL/24hrs
- Diarrhea is classified by duration: <2 weeks (Infection), >4 weeks (Small bowel, Large bowel)
- The Bristol stool chart is used to classify consistency: Types 1 & 2 are constipation, Types 6 & 7 are diarrhea
- The most common causes of acute diarrhea are viral infections
- Norovirus is the most common cause of acute diarrhea in adults
- Rotavirus is the most common cause of acute diarrhea in children
Small Intestinal vs Large Intestinal Diarrhea
- Small intestinal diarrhea usually has large volume, watery consistency, absent pus/blood/mucus, present abdominal cramps and bloating
- Large intestinal diarrhea usually has present pus/blood/mucus, present tenesmus, present dyschezia, present abdominal pain and fever
- Small intestinal diarrhea is caused by osmotic, secretory, and vibrio cholera etiologies
- Large intestinal diarrhea is caused by invasive organisms, e.g. Shigella, and inflammation, e.g. Ulcerative colitis
- The stool osmotic gap is normal/decreased in secretory diarrhea and increased in osmotic diarrhea
Layers of the Intestinal Wall
- The submucosa contains Brunner's glands which secrete bicarbonate
- The submucosa contains Peyer's patches, which are macroscopic lymphoid aggregates that hypertrophy in typhoid
- The muscularis propria is a layer of muscle
- The serosa is the outer layer of the intestinal wall
- The small intestine is the site of the majority of absorption
- The small intestine is divided into a proximal 2/5 and a distal 3/5
- The proximal small intestine (jejunum > duodenum) is the site of maximum absorption
- The distal small intestine (ileum) is the site of bile acid, vitamin B12, and magnesium absorption
Fat Absorption
- The luminal phase of fat absorption involves the breakdown of triglycerides by pancreatic lipase
- The breakdown products of triglycerides combine with bile acids to form micelles
- Micelles diffuse into enterocytes
- Bile acids have an enterohepatic circulation, in which they are synthesized, conjugated, recycled
- The rate-limiting enzyme of bile acid synthesis is 7a-hydroxylase
- Bile acid synthesis in the liver is controlled by a negative feedback mechanism
- Chronic pancreatitis can cause a bile acid defect
- Bile acids play a role in the absorption of lipid soluble vitamins
Protein Absorption
- Endopeptidases like trypsin and exopeptidases like carboxypeptidase and aminopeptidase are involved in protein digestion
- Enterokinase activates trypsinogen to trypsin
- Transport of amino acids across the small intestinal mucosa occurs via sodium-amino acid co-transporters
Defects in Protein Absorption
- Global malabsorption can occur due to celiac disease, Whipple disease, and tropical sprue
- Selective malabsorption can occur due to enterokinase deficiency, Hartnup's disease, and cystinuria
- Enterokinase deficiency impairs the activation of trypsinogen to trypsin
- Hartnup's disease causes a neutral amino acid transport defect
- Cystinuria causes a dibasic amino acid transport defect, leading to excretion of cystine, ornithine, lysine, and arginine
Carbohydrate Absorption
- Disaccharidases in the small intestinal brush border epithelium break down disaccharides into monosaccharides
- Lactase breaks down lactose into glucose and galactose
- Maltase breaks down maltose into two glucose molecules
- Sucrase breaks down sucrose into glucose and fructose
- Trehalase breaks down trehalose into two glucose molecules
- Sodium-glucose cotransporter 1 (SGLT1) is responsible for the active transport of glucose and galactose
- Glucose transporter (GLUT2) facilitates the diffusion of glucose and galactose into the blood
- Glucose is converted into glucose-6-phosphate by glucokinase in the liver
- Fructose and galactose are phosphorylated in the liver
- Fructose is transported across the intestinal mucosa by Glucose transporter (GLUT5)
Defects in Carbohydrate Absorption
- Lactase deficiency can be congenital or acquired (primary or secondary)
- Congenital lactase deficiency is autosomal recessive
- Acquired lactase deficiency is more common and caused by a genetic defect
- Secondary lactase deficiency can occur due to infections and irritable bowel syndrome
- Defects in the small intestinal mucosa can cause global carbohydrate malabsorption
- Familial glucose-galactose malabsorption syndrome is caused by a defect in SGLT-1
Chronic Diarrhea
- Osmotic diarrhea is commonly caused by malabsorption of water, but osmotic diarrhea is also related to tumors and toxins
- Secretory diarrhea is caused by an increase in fluid secretion into the intestinal lumen
- Inflammatory diarrhea is caused by inflammatory bowel disease
Pathological Classification of Diarrhea
- Osmotic diarrhea is the most consistent clinical symptom of malabsorption
- Steatorrhea is the hallmark of malabsorption, and it is the passing of pale, bulky, fatty, malodorous, greasy stools
- Steatorrhea causes a decreased fat absorption in the small intestine, an increased stool osmolality in the colon
- Steatorrhea causes stool to draw water from large intestinal epithelial cells
- The gold standard for investigating steatorrhea is the 72-hour fecal fat test
- The 72-hour fecal fat test involves fat input of 100 g/day. Stool fat excretion ≥7% is considered steatorrhea
- Other tests for steatorrhea include qualitative stool fat tests using Sudan III, Sudan IV, or Oilred O
Physiology of GIT Absorption and Selective Malabsorption
- Absorption is divided into luminal, mucosal, and post mucosal stages
- Luminal absorption involves enzyme-mediated processes in the small intestinal mucosa
- The small intestinal mucosa is lined with enterocytes, villi, and crypts
- Villi are surrounded by crypts of Lieberkuhn and contain brush borders with enzymes
- Crypts contain Paneth cells, enteroendocrine cells, and goblet cells
- The small intestinal mucosa is continuously renewed every 48-72 hours
- The lamina propria contains glands and blood vessels
- The muscularis mucosa provides a tight attachment to the mucosa
- Plicae circulares are visible mucosal folds on the luminal surface of the small intestine
- The interstitial cells of Cajal are pacemaker cells of the small intestine
- The small intestine has a basal electrical rhythm
Defects in Luminal Absorption
- Chronic pancreatitis affects pancreatic lipase, which leads to impaired lipolysis
- Bile acid defects occur due to defects in synthesis or premature deconjugation in the small intestine
- Defects in reabsorption can occur in tuberculosis and Crohn's disease
- Defects in secretion can occur in primary biliary cholangitis, primary sclerosing cholangitis, and small intestinal bacterial overgrowth (SIBO)
Mucosal Phase of Absorption
- Defects in the small intestinal mucosal integrity can cause malabsorption
- Celiac disease, Whipple disease, and tropical sprue can impair mucosal absorption
Post-Mucosal Phase of Absorption
- Long-chain fatty acids (LCFA) are esterified and transported via intestinal lymphatics to form chylomicrons
Types of Fatty Acids
- Long-chain fatty acids (LCFA) have a carbon chain length > 12
- Medium-chain fatty acids (MCFA) have a carbon chain length of 8-12
- Short-chain fatty acids (SCFA) have a carbon chain length of < 8
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