10/8- Small Intestine Pathology Flashcards
What is the widest part of the small intestine?
Duodenum
What part of the small intestine does the jejunum comprise?
- Location
- Describe relative dimensions
- Histology
Upper 2/5, around umbilicus and L iliac fossa
- Wider, thicker, more vascular
- Villi are larger; no Peryer’s patches in upper part
What part of the small intestine does the ileum comprise?
- Location
- Describe relative dimensions
- Histology
Lower 3/5, umbilical, hypogastric, R iliac and pelvic region
- Narrow, smaller, thinner layers; less vascular
- Numerous and larger Peyer’s patches
What is the normal villous to crypt length ratio?
3-5: 1
What is seen here?
Compare jejunum and ileum (picture)
Jejunum or ileum?
Jejunum
Jejunum or ileum?
Ileum
T/F: Obstruction may occur at any level of the GIT?
True
Where is the most common site of obstruction in the small intestine?
- Other sites/causes?
Mostly small intestine (narrow lumen)
- 80% of mechanical obstructions = hernias, intestinal adhesions, intussusception and volvulus
- 10-15% of small bowel obstructions = tumors and infarction
What are some clinical manifestations of intestinal obstruction?
- Abdominal pain and distention
- Vomiting
- Constipation
Treatment of intestinal obstruction?
Surgery in cases of mechanical obstruction or severe infarction
What is a hernia?
Weakness/defect in the wall of the peritoneal cavity
- Hernia sac = protrusion of serosa-lined pouch of peritoneum
Are acquired hernias more commonly anterior or posterior? Where?
Acquired are more anterior
- Inguinal and femoral canals or umbilicus or surgical scars
What happens with pressure at the neck of a hernia?
Impair venous drainage
- > stasis and edema
- > increase in size
- > permanent entrapment (incarceration)
- > arterial and venous compromise (strangulation)
- > infarction
What is adhesion/what causes it?
- Characteristics
- Complications?
Surgical procedures, infection, or peritoneal inflammation may cause adhesions between bowel segments, abdominal wall and operative sites
- Rarely congenital
Fibrous bridges, closed loops; other viscera may slide -> become entrapped: internal herniation
Complications:
- Obstruction
- Strangulation
What is seen here?
Small bowel infraction secondary to intraperitoneal fibrous band
What is volvulus?
- What does it cause
- Clinical presentation
- Common locations
Complete twisting of a loop of bowel about its mesenteric base of attachment
- Luminal and vascular compromise
Clinical presentation: features of obstruction and infarction
Most often in:
- Sigmoid colon, then
- Cecum
- Small bowel
- Stomach
What is intussusception?
- Prognosis
A segment of the intestine, constricted by a wave of peristalsis, telescopes into the immediately distal segment
- Once trapped, the invaginated segment is propelled by peristalsis and pulls the mesentery along
- Untreated intussusception… intestinal obstruction, compression of mesenteric vessels and infarction
What is seen here?
Jejunum with big mass in distal portion; pulled rest of jejunum along
What causes intussusception in kids? Adults?
Infants and children:
- Usually no underlying anatomic defect
- Association with rotavirus infection
Older children and adults:
- Intraluminal mass or tumor; leading point of traction
How to treat intussusception in kids? Adults?
Infants and young children: barium enema
Older patient: surgery
Describe blood supply to the small/large intestine?
Arterial supply:
- Celiac a
- Superior and inferior mesenteric arteries
What is the most common cause of intestinal ischemia?
Arterial insufficiency if large and small bowel
Acute compromise of any major vessel causes what?
Infarction of several meters of intestine
How does ischemic bowel disease present?
Older individuals with coexisting cardiac or vascular disease
Acute mesenteric ischemia (95%):
- Abdominal pain, N/V and hematochezia
- Little or no pain in elderly until advanced stages
- Shock and vascular collapse within hours as a result of blood loss
Chronic mesenteric ischemia (< 5%):
- Postprandial abdominal pain; 30 min after a meal, peaks in one hour and resolves in 3 hours
What is found on the physical exam of someone with ischemic bowel disease?
- Prognosis
Bowel sounds diminish or disappear, and muscular spasm creates rigid abdomen (acute abdomen)
- Delayed or missed diagnosis: disastrous consequences
- Mucosal barrier breaks down, bacteria enter the circulation and sepsis; mortality >50%
What is seen here?
Ischemic bowel disease (or just infarction?)
What is the etiology of acute arterial obstruction: non-occlusive?
Non-occlusive: failure to deliver sufficient oxygen due to inadequate blood flow without an obstruction
- Severe atherosclerosis
- Hypotension, shock and dehydration
- Vasoconstrictor drugs: digitalis, vasopression and propranolol
What is the etiology of acute arterial obstruction: occlusive?
- Intraluminal
- Thromboemboli: the most common cause
- Atherosclerosis, dissecting aneurysms..
- Intramural: drugs causing vasospasm: cocaine, snake venom
- Extramural: compresion by tumors, volvulus, torsion..
What is the most common cause of acute arterial obstruction?
Thromboemboli
Describe the pathogenesis of acute arterial obstruction- 2 big stages?
- Initial hypoxic injury
- Reperfusion injury
What happens in the initial hypoxic injury?
- At the onset of vascular compromise
- Some damage (epithelial cells relatively resistant to transient hypoxia)
What happens in the reperfusion injury?
- Restoration of the blood supply
- Greatest damage …trigger multiorgan failure
- Free radical production, neutrophil infiltration, and release of inflammatory mediators (complement proteins and TNF )
Extent of damage in obstruction/ischemia depends on what?
- Severity of vascular compromise
- Time frame
- Size of obstructed vessel and its degree of collateral circulation
What is seen on microscopic examination of ischemia?
How does occlusive differ from non-occlusive?
Similar changes, except that in occlusive disease ischemia is segmentally distributed and affected regions uniformly affected whereas in non-occlusive patchy, variable in severity and often widespread
What layer is most susceptible to hypoxia?
What layer most easily regenerates?
Mucosa on both counts!
- Mucosa is the most susceptible layer to hypoxia, also has the greatest regenerative capacity
What is seen here?
Ischemia
- Attenuated villi
- Ulcerated
What is Celiac disease?
- Mechanism
- Epidemiology
- Gluten sensitive enteropathy
- Autoimmune-mediated disorder that results in damage to small intestinal mucosa and malabsorption of nutrients
Most common in countries with European descent population (1% prevalence):
- Europe
- America
- Australia
What does celiac disease look like in adults?
Mild disease : fatigue due to anemia
- Silent disease: positive serology and villous atrophy without symptoms
- Latent disease: positive serology but no villous atrophy
More on celiac disease:
- Symptoms
- Other associations
- Gender prevalence
Symptoms:
- Abdominal discomfort
- Diarrhea and steatorrhea
Also: FTT, infertility, neurologic disorders, dermatitis herpetiform
Female = Male
What is the pathogenesis of celiac disease?
- What is gluten biochemically?
- What normally digests it
- Gluten: the major storage protein of wheat and similar grains
- Gliadin: alcohol-soluble fraction of gluten; which has most of the disease-producing components
- Gluten is digested into AAs and peptides, including a 33-AA α-gliadin peptide, resistant to degradation by gastric, pancreatic, and small intestinal proteases
Describe what’s going on here?
(Missed the beginning- Ab mediation?)
- Gliadin enters, passes epithelial cells to reach lamina propria
- Gliadin is deaminated by tissue transglutaminase (tTG)
- It effects antigen presenting cellswtih DQ2/8 to activate cytotoxic T cells
- Stimulated to kill more lymphocytes
- T cells also stimulate B cells to produce Abs against gliadin
What are the genetics behind celiac disease?
- Class II HLA-DQ2 or HLA-DQ8 allele: less than half of the genetic component
- Polymorphisms of immune-regulatory genes, such as those encoding IL-2, IL-21, CCR3, and SH2B3, and genes that determine epithelial polarity
What other diseases/conditions celiac disease associated with?
- Type 1 diabetes
- Thyroiditis
- Sjögren syndrome
What serology should be done to identify Celiac disease?
Most sensitive tests:
- IgA Abs to tissue transglutaminase
- IgA or IgG Abs to deamidated gliadin
Anti-endomysial Abs are highly specific but less sensitive
If IgA test is negative, rule out IgA deficiency:
- IgA deficiency: IgG antibodies to tissue transglutaminase and deamidated gliadin
Absence of HLA-DQ2 or HLA-DQ8
- High negative predictive value
What is seen grossly in celiac disease?
- Reduced or absent duodenal folds
- Totally flat mucosa with dramatic clinical and morphologic response to removal of gluten
What is seen on the microscopic exam in celiac disease?
Atrophic or absent villi
- Villous/crypt ratio: 1 or less (normal: 2.5+)
- Increased in T lymphocytes
What is the most common celiac disease associated cancer? Others?
Enteropathy-associated T-cell lymphoma
- Also small intestinal adenocarcinoma
What are symptoms of small intestinal adenocarcinoma?
- Abdominal pain
- Diarrhea
- Weight loss
Despite a strict gluten free diet (failure to adhere to gluten-free diet is the most common cause of recurrent symptoms)
What is seen here?
Giardia in lumen
What is seen here?
Giardia
- Pear shaped, 2 symmetric nuclei
What are Giardia?
- Characteristics
- Disease
- Location
- Resistance
Giardia characteristics:
- Pear shaped trophozoites
- 2 symmetric nuclei each with 1 necleoli
Cause Giardiasis
- Most common diarrheal disease transmitted by contaminated water
Located in duodenum
- Only human protozoa that resides here
Cysts are resistant to chlorine
How is Giardiasis transmitted?
- Transmitted through streams and domestic water supplies
- Contaminated with cysts from human or wildlife feces, fecal-oral in day-care and oral-anal sex
Symptoms of Giardiasis?
- Severe diarrhea
- Cramping and malabsorption
Diagnosis of Giardiasis?
- Trophozoites or cysts in stool
- Surgical biopsies
- Serology (ELISA) may be helpful
What is seen here?
Giardia???
What is strongyloides stercoralis?
- Epidemiology/demographics
- Associated with what
Threadworm Worldwide distribution:
- Southern US
- Mental institutions
- Adults, hospitalized, chronic illness and immunocompromised
Associated with
- Steroids
- HTLV1
What are symptoms of Strongyoides stercoralis?
- Diarrhea
- Abdominal pain and tenderness
- N/V
- Weight loss
- GI bleed
How does the Strongyloides stercoralis worm cause disease?
- How is infection diagnosed?
Worm penetrates skin.. veins.. lung.. small intestine
- Aauto-infection; can be fatal especially in immunossuppressed
Diagnosis
- Larvae or egg in stool
- Adult worm in intestinal biopsy
- Serology
What is seen here?
Strongyloides stercoralis
What is seen here?
Strongyloides stercoralis (?)
- Many lymphocytes?
What is Whipple’s disease?
- Other organ systems
- Histology
Intestinal lipodystrophy
Can involve:
- LN
- Heart, lung
- Liver, spleen
- Adrenal glands and nervous system
Histology:
- Large macrophages crowding lamina propria
- Distorting the villi and alternating with empty spaces
- Histiocytes have diastase resistant, PAS+ material
What is the clinical presentation of Whipple’s disease?
Triad:
- Diarrhea
- Weight loss
- Malabsorption
What causes Whipple’s disease?
Differential diagnosis?
Tropheryma whippelli
- Malabsorption due to impaired lymphatic transport
Treatment: response to antibiotic
Main differential diagnosis
- MAI
- Ingestion of mineral oil can cause similar changes in intra-abdominal lymph nodes
What is seen here?
Whipple’s disease
