Small Intestine and Colon Pathology #1 - Nelson

Question 1

Define ileus.

Answer 1

loss of the normal propulsive function of the bowel in the absence of mechanical obstruction

(intestinal pseudo-obstruction)

Question 2

Define hernia.

Answer 2

Defect in the wall of the peritoneal cavity, permitting protusion of a serosal lined pouch of peritioneum called a hernia sac

Locations for acquired hernias is: the inguinal or femoral canal, umbilicus, or at sites of abdominal surgical scars

Question 3

Define bowel adhesions.

Answer 3

Fibrous bands of scar tissue between bowel segments, the abdominal wall, or operative sites

-usually secondary to previous surgical procedures, abdominal infection, or other causes of peritoneal injury/inflammation such as endometriosis

Question 4

Define volvulus.

Answer 4

Complete twisting of a loop of bowel about its mesenteric base

most often occurs in the sigmoid colon, followed by the cecum, and can involve small bowel, stomach, and transverse colon

Question 5

Define intussusception.

Answer 5

a segment of bowel, constricted by a wave of peristalsis, telescopes into the immediately distal segment

• Leads to:
  
  • intestinal obstruction
  • compromise of mesenteric blood vessels
  • infarction

Question 6

Define stenosis.

Answer 6

a form of atresia in which the lumen is markedly decreased in caliber, usually associated with fibrous thickening of the wall

Question 7

Define atresia.

Answer 7

Incomplete development

Question 8

Define omphalocele.

Answer 8

closure of ventral abdominal musculature is incomplete, and abdominal viscera herniate into a ventral membranous (peritoneal) sac

Question 9

Define gastroschisis.

Answer 9

similar to omphalocele, but defect involves all layers of the abdominal wall

Question 10

Define Meckel’s diverticulum.

Answer 10

A “true” diverticulum of the small bowel, composed of all three layers (mucosa, submucosa, and muscularis propria).

Question 11

What are the complications of Meckel’s diverticulum?

Answer 11

• ulceration
  
  • may have ectopic gastric mucosa with acid production and peptic ulcers in adjacent ileum
• perforation
• hemorrhage
• fistula formation to the bladder
• intussusception

Question 12

What is the clinical presentation and pathologic abnormality in Hirchsprung’s disease?

Answer 12

• Clinical presentation:
  
  • 1 of 5000 live births
  • mostly males (M:F ratio 4:1)
  • with failure to pass meconium in the neonatal period
  • infants and older children present with obstructive constipation, abdominal distension, and vomiting
• Pathologic:
  
  • when the normal migration of neural crest cells from cecum to rectum is arrested prematurely or when the ganglion cells undergo premature death
  • The affected segment lacks ganglion cells in both the submucosal (Meissner) and myenteric (Auerbach) plexus
  • Coordinated peristaltic contractions are absent, leading to functional obstruction and dilation proximally.

Question 13

Define malabsorption.

Answer 13

impaired absorption of nutrients

(fats, proteins, carbohydrates, vitamins, electrolytes and minerals, water)

• Disturbance in one of the following:
  
  • Intraluminal digestion and brush border digestion.
  • Transepithelial transport (absorption) into the small intestinal epithelium with intraepithelial processing.
  • Lymphatic transport of absorbed lipids.

Question 14

What are the clinical definitions of diarrhea?

Answer 14

• Generally defined as excessive increase in stool mass, frequency, or fluidity, typically greater than 200 g/day.
• In clinical practice, diarrhea is defined as >3 loose stools per day.
  
  • Acute diarrhea is defined as diarrhea lasting <14 days.
  • Chronic diarrhea is defined as diarrhea lasting >4 weeks.

Question 15

What are the four kinds of diarrhea?

Answer 15

• Secretory diarrhea, characterized by isotonic stools.
• Osmotic diarrhea, due to excessive osmotic forces from unabsorbed luminal solutes (e.g. lactase deficiency).
• Malabsorptive diarrhea, due to failure of global nutrient absorption with steatorrhea.
• Exudative diarrhea: due to inflammatory processes, with bloody stools, increased stool neutrophils.

Question 16

What are the key pathologic findings in celiac disease?

Answer 16

• Sensitivity to gluten and the alcohol soluble fraction of gluten, gliadin, results in an immune reaction (hypersensitivity rxn) which damages the surface epithelium of the small bowel
• villous atrophy
• increased numbers of intraepithelial lymphocytes (IELs)
• epithelial proliferation with crypt elongation

Question 17

Define tropical sprue.

Answer 17

Malabsorption disease that mimics celiac disease occurring in the tropics

• Milder degree of villous atrophy than celiac disease
• Tropical sprue typically affects the distal small bowel, and as such, patients can have vitamin B12 deficiency.
  
  • following an acute diarrheal illness
  • secondary to some type of infectious agent resulting in overgrowth of aerobic enteric bacteria

Question 18

Define abetalipoproteinemia.

Answer 18

Rare autosomal recessive disorder caused by a mutation in the microsomal triglyceride transfer protein (MTP) that catalyzes the transport of triglycerides, cholesterol esters, and phospholipids from the enterocyte.

Question 19

Define Whipple Disease.

Answer 19

Systemic infection caused by a gram-positive actinomycete, Tropheryma whippelii.

Question 20

How is Whipple disease diagnosed?

Answer 20

Definitive diagnosis can be made by performing PCR on the tissue biopsy.

Question 21

What is the most common type of disaccharidase deficiency?

Answer 21

By far the most common form of disaccharidase disorder is adult-onset lactase deficiency. Lactase activity declines with age and by adulthood the loss of the enzyme leads to lactose intolerance.

Question 22

How can pancreatic insufficiency lead to malabsorption?

Answer 22

Decreased luminal lipase and trypsin results in undigested fats and protein in the stool.

_{(Carbohydrate absorption is not affected.)}