tbl 3 pathology (small intestine)

Question 1

[Histology of normall small intestine]
- At the luminal aspect, finger-like villi and _____________ are present to increase the surface area of absorption
o Form the villi, the epithelium dips down to the mucosa to form _____
o The lifespan of enterocytes are 72 hours but cells on the side walls of crypts constantly divide and help to renew and replace the epithelial cells lost to
the lumen
- The villus:crypt ratio is normally _______but can be changed in diseased states
- _____________ can be normal but increased numbers can represent diseased states
- Staining for mucin reveals a ________ at the luminal aspect of enterocytes – rich carbohydrate coat over the brush border, protecting mucosa from luminal contents and a site of certain enzymes such a disaccharides – important for terminal digestion and absorption of certain nutrients

Answer 1

microvilli brush border; crypts; 3:1 to 5:1; Intra-epithelial lymphocytes (IELs); glycocalyx layer

Question 2

Digestion
- Digestion and absorption of food involves the small bowel, pancreas (pancreatic juice) and biliary tract (bile from liver)
- Digestion and absorption occurs in three phases
o Luminal phase – in the lumen, food is mixed with digestive juices and broken down
o Mucosal phase
o Post-absorptive phase

Malabsorption – can be due to defects in the 3 phases of digestion and absorption

1. Pancreatic enzymes are present but inactivated due to ___________ in small bowel
2. Less bile produced in the case of _________
3. Bile not reaching the small intestine e.g. _________
4. Such as in small bowel resection
5. Present in bacterial overgrowth syndromes

Answer 2

acidic chyme; liver cirrhosis; biliary stones

Question 3

Celiac disease
- Celiac disease is gluten-sensitive enteropathy – immune mediated enteropathy to ingested gluten in genetically predisposed individuals
- Pathophysiology – villous _______ with crypt ________ due to loss of ________________
o Cells in crypts are increased (increased mitosis) but are unable to keep up with the rate of epithelial cell destruction, resulting in ___________.

1. Gluten is ingested and broken down by _________ into gliadin, which undergoes further digestion and is absorbed into the mucosa
2. Gliadin is acted upon by tTG to form deaminated gliadin
3. Deaminated gliadin is picked up by HLA DQ2 or 8 arms of antigen-presenting cells and presented to __________
4. TH cells mediate immune responses as plasma cells form anti-tTG antibodies and induce epithelial cells to produce IL-15, which activates intraepithelial CD8+ CTL to cause damage and destruction to the epithelium
   - Anti-tTG antibodies can be detected – helps in confirmation of diagnosis (________ is preferred now)

Answer 3

atrophy; hyperplasia; surface enterocytes; villous blunting

peptidases; CD4+ TH cell; DGP IgG Ab

Question 4

Histological features of celiac disease
- Increased intraepithelial lymphocytes and in lamina
propria (>30 intraepithelial lymphocytes per 100
__________)
- Associated with complete or partial villous atrophy with crypt hyperplasia

Progression Histology
- Normal (A) Preserved villous architecture, villus to crypt ratio of 3:1 to 5:1
- Early (B) _________ of villus, increased lengths of crypts and ______, villus to crypt ratio of 1:1
- Late (C) ____________ with flat mucous
crypts that are markedly elongated. Increased IELs and lymphocytes in lamina propria

Crypts – increased mitosis, proliferation
- However, histological features are not totally diagnostic of celiac disease as increased IEL with or without villous blunting can be seen in
o Drugs (such as NSAIDs), peptic duodenitis, H pylori infection, giardiasis, food allergies, refractory sprue, autoimmune gastropathy, Crohn’s disease, small intestinal bacterial overgrowth, infectious gastroenteritis, ZES

Answer 4

surface enterocytes; blunting; IELs

Complete villous atrophy;

Question 5

Biopsy in celiac disease

• __________ is suggestive but not pathogenomic of celiac disease
• Clinical and serological correlation are essential
• _________is important for diagnosis and to assess response with a gluten-free diet – if the mucosa reverts to normal with clinical improvements after a gluten-free diet, it supports the diagnosis of celiac disease
• If serology is negative, other causes may be – Crohn’s disease, Giardia, medications, food allergy

Effects of celiac disease

• Impaired nutrient absorption – failure to thrive and diarrhoea for infants, stunted growth in childhood and anaemia, altered bowel habits, weight loss in adults
• Extra-intestinal manifestations
• Other autoimmune conditions – dermatitis herpetiformis (IgA mediated cutaneous manifestation of celiac disease), _____________ (increased IEL)
• Increased risk of malignancy, particularly enteropathy associated T cell lymphoma, _______.

Answer 5

Villous atrophy; Biopsy ; lymphocytic gastritis or colitis; adenocarcinoma

Question 6

Intestinal obstruction
- Mechanical blockage to a segment of bowel – occurrence is more common in small bowel than large bowel due to smaller lumen
- Types of intestinal obstruction
o Bowel wall lesions – tumours, strictures, __________
o Outside bowel wall – adhesions, hernia, volvulus, tumours
o Luminal lesions (rare) – gall stone
o Functional – _____________ (congenital aganglionic segment of colon leading to dilation)
- Herniation, adhesions, volvulus and intussusception account for 80% of IOs

Answer 6

intussusception; Hirschsprung disease

Question 7

Pathophysiology of IO
- Obstruction of a tubular structure (i.e. bowel) leads to proximal bowel dilatation
o Leads to ____________, resulting in vomiting (electrolyte and fluid loss)
- As the bowel dilates, luminal pressure increases, leading to ___________, resulting in vascular congestion and oedema
o At a point, the luminal pressure exceeds the arterial pressure, leading to __________
o Ischemia and infarction of bowel wall – ischemia leads to reduced viability and infarction leads diffusion of toxic products resulting in ___________
- Stasis leads to bacterial proliferation – inflammation, perforation and peritonitis
- Patient presents with pain, vomiting, dehydration, abdominal distension and constipation
o Mortality is 10%, but if necrosis or perforation present, 30%

• Simple IO – simple obstruction without vascular compromise
• Strangulated IO – associated with vascular compromise, ischemia and infarction

o Perforation may be possible

Answer 7

retroperistalsis; venous compression; arterial blockage; toxaemia

Question 8

Types of IO

1. Herniation – protrusion of a pouch like __________ through a defect or aperture (commonly in the abdominal wall)
   - Sac often contains bowel loops or ________, with strangulation (vascular compromise)
   - Common sites – inguinal, femoral, ________, umbilical
   - Complications – irreducible hernia, intestinal obstruction, hernia with strangulation leading to Infarction, perforation
2. Adhesions – usual develop as fibrous adhesions between bowel loops, abdominal wall or operative sites, bowel loops trapped in between the fibrous bands
   - History of previous surgery, infections or __________
   - Complications – IO which may be complicated by strangulation
3. Intussusception
   - A portion of bowel, constricted by a wave of peristalsis, invaginates inside the adjoining distal segment
   o Intussusceptum (invaginating portion i.e.
   “telescoped” portion), intussuscipiens (receiving
   portion)
   - Commonest site – ileocolic intussusception at the
   ____________
   - Most common cause of IO in children under 2 years of age
   - Features at the leading edge of an intussusception
   o Children – prominent ________, Meckel’s
   diverticulum, enlarged mesenteric node
   o Adults – usually a __________

• Complications – IO
  o Infarction – as a loop of bowel is telescoped into the distal segment, the mesentery is pulled along, compressing it along with blood vessels within it
  § Currant jelly stool – mixture of necrotic mucosa, blood and mucous
  o Perforation

Answer 8

peritoneum lined sac; omentum; incisional; endometriosis;

Ileocecal valve; Peyer’s patches; polypoid tumour

Question 9

Types of IO

4. Volvulus (rare)
   - Rotation of a bowel loop on itself (especially those with long and redundant mesentery) – luminal and vascular obstruction
   - Common sites – _________, rarely the cecum
   - Complications – IO, strangulation with infarction and perforation
5. Meckel’s diverticulum
   - Remnanto of __________ – connects yolk sac with the midgut lumen in the foetus
   o True diverticulum (involves all layers of the bowel wall i.e. mucosa, submucosa and _________) on the antimesenteric border
   - Most common congenital anomaly of the GIT – 2” long, 2 feet from the ileocecal valve
   o Occurs in 2% of population, 2x more common in males and most are symptomatic by 2 years of age
   - Histology – ileal mucosa with gastric or pancreatic tissue (heterotopia)
   - Complications
   o Diverticulitis, peptic ulceration with haemorrhage and abdominal pain – peptic ulcers due to gastric oxytocic mucosa that may be present
   o Intestinal obstruction – intussusception, volvulus that can be complicated with ischemia or infarction, perforation

Answer 9

sigmoid colon;

vitellointestinal duct; muscularis propria