GI- Path- Non-neoplastic diseases of the intestines Flashcards
What are the 4 main causes of intestinal obstruction that make up 80%?
What other 2 causes make up the last 20%?
hernias, intestinal adhesions, intussusception, and volvulus
tumors and infarction
What intervention is usually required in cases involving mechanical obstruction or severe infarction?
surgical
What is the most common obstruction worldwide and 1/3 most common in US?
Hernias
Any weakness or defect in the abdominal wall may permit protrusion of a serosa-lined pouch of peritoneum called a
hernia sac.
Acquired hernias typically occur anteriorly/posteriorly, via the inguinal and canals, umbilicus, or at sites of surgical scars,
anterior
femoral
Obstruction usually occurs because of visceral protrusion and is most frequently-associated with hernias, which tend to have narrow orifices and large sacs.
• Small bowel loops are typically involved, but or large bowel may also protrude, and any of these may become entrapped.
inguinal
omentum
The resultant stasis from impaired venous drainage and edema increase the bulk of the herniated loop, leading to permanent entrapment (incarceration) and, over time, arterial and venous compromise (strangulation), and
infarction.
Surgical procedures, infection, or other causes of peritoneal inflammation, such as endometriosis, may result in development of between bowel segments, the abdominal wall, or operative sites.
adhesions
• are the most common cause of intestinal obstruction in the United States.*
Sequelae, include obstruction and strangulation.
Adhesions
Twisting of a loop of bowel about its mesenteric point of attachment is termed ; it results in both luminal and vascular compromise.
can result in obstruction and .
volvulus
infarction
Volvulus most often in large redundant loops of colon, followed in frequency by the cecum, small bowel, stomach, or, rarely, transverse colon
sigmoid
Intussusception occurs when a segment of the intestine, constricted by a wave of peristalsis, into the immediately distal segment.
Once trapped, the invaginated segment is propelled by peristalsis and pulls the along.
telescopes
mesentery
Intussusception is the most common cause of intestinal obstruction in children less than years of age.
2
Instussusception is associated with viral infection, rotavirus vaccines, reactive of Peyer’s patches
hyperplasia
are diagnostically useful and also are effective in correcting idiopathic intussusception in infants and young children.
• Surgical intervention is necessary when an intraluminal or
serves as the initiating point of traction, as is typical in older children and in adults
Contrast enemas
mass
tumor
What is a mural infarction?
An infarction of the mucosa and the submucosa
While mucosal or mural infarctions often are secondary to acute or chronic , transmural infarction is generally caused by vascular obstruction.
hypoperfusion
acute
Important causes of acute arterial obstruction include severe (which is often prominent at the origin of mesenteric vessels), aortic aneurysm, hypercoagulable states, oral contraceptive use, and embolization of cardiac or aortic atheromas.
atherosclerosis
vegetations
What two aspects of intestinal vascular anatomy contribute to the distribution of ischemic damage?
- Watershed zones
- Patterns of intestinal microvessels
intestinal segments at the end of their respective arterial supplies that are particularly susceptible to ischemia, the splenic flexure (SMA-IMA) and the sigmoid colon and rectum (IMA, pudendal, and Iliac a.) ?
watershed zones
Generalized or hypoxemia can cause localized injury at these sites, and ischemic disease should be considered in the differential dx for focal colitis of the flexure or colon
hypotension
splenic
rectosigmoid
Why is the surface epithelium particularly vulnerable to ischemic injury?
Intestinal capillaries run alongside the glands, from crypt to surface, before making a hairpin turn at the surface
surface epithelial atrophy, or even necrosis and epithelial sloughing, with normal or hyperproliferative crypts is a morphologic signature of
disease.
ischemic intestinal
Infarction is frequently segmental and patchy.
• The mucosa is hemorrhagic and often .*
ulcerated
Dead bowel
ischemic intestine demonstrates atrophy or sloughing of surface epithelium.
- The crypts may be
- Inflammatory infiltrates are initially absent in acute ischemia, but
are recruited within hours of reperfusion.
hyperproliferative.
neutrophils
note: the neutrophils and the sloughing up top
ischemia is accompanied by fibrous scarring of the lamina propria and, uncommonly, stricture formation.
Chronic
note: notice the scarring of the lamina propria in light pink
Ischemic bowel disease tends to occur in younger/older adults with coexisting cardiac or vascular disease.
older
Acute transmural infarction typically manifests with sudden, severe abdominal pain and tenderness, sometimes accompanied by nausea, vomiting, bloody diarrhea, or grossly stool
melanotic
Acute transmural infarction may progress to shock and vascular collapse within hours as a result of loss.
• sounds diminish or disappear, and muscular spasm creates boardlike rigidity of the abdominal wall
blood
Peristaltic
What other 3 abdominal emergencies resemble ischemic bowel disease?
acute appendicitis, perforated ulcer, and acute cholecystitis,
As the mucosal barrier breaks down, bacteria enter the circulation and
can develop; the mortality rate in these cases may exceed 50%.*
sepsis
What is characterized by malformed submucosal and mucosal blood vessels, occurs most often in the cecum or right colon, and usually presents after the sixth decade of life?
• Although it affects less than 1% of the adult population, accounts for 20% of major episodes of lower intestinal bleeding.
angiodysplasia
What are dilated anal and perianal collateral vessels that connect the portal and caval venous systems to relieve elevated venous pressure within the hemorrhoid plexus?
hemorrhoids
What are some predisposing factors for hemorrhoids?
constipation
increased intraabdominal and venous pressure
venous stasis of pregnancy
portal hypertension
Collateral vessels within the hemorrhoidal plexus are located below the anorectal line and are termed external hemorrhoids, while those that result from dilation of the hemorrhoidal plexus within the distal rectum are referred to as internal hemorrhoids
inferior
superior
sclerotherapy, rubber band ligation, and infrared coagulation are treatments for which condition?
hemorrhoids
Systemic vasculitides and infectious diseases (CMV) can cause vascular disease that is/is not confined to the gastrointestinal tract.
is not
What disease refers to acquired pseudodiverticular outpouchings of the colonic mucosa and submucosa?
rare in individuals younger than 30 years of age, but the prevalence approaches 50% in Western adult populations older than years of age.
Diverticular disease
60
Why is diverticulosis more common in the colon?
the colon, this muscle layer is discontinuous, being gathered into three bands termed taeniae coli.
High luminal pressures may be generated by exaggerated peristaltic contractions, with spasmodic sequestration of bowel segments that may be exacerbated by diets low in which reduce stool bulk.
fiber
Anatomically, colonic diverticula are small, flasklike outpouchings, usually 0.5 to cm in diameter, that occur in a regular distribution in between the taeniae coli.
• They are most common in the colon, but other regions of the colon may be affected.
1
sigmoid
Colonic diverticula have a thin wall composed of a or atrophic mucosa, compressed submucosa, and attenuated muscularis propria - often, this last component is totally absent
flattened
Because the wall of the diverticulum is supported only by the muscularis mucosa and a thin layer of subserosal adipose tissue, inflammation, increased pressure, and mucosal ulceration within an obstructed diverticulum can readily result in
perforation.
Review differences between IBD and Crohn’s
is limited to the colon and rectum and extends only into the mucosa and submucosa.
, aka regional enteritis (because of frequent ileal involvement), may involve any area of the gastrointestinal tract and is frequently transmural.
Ulcerative colitis
Crohn disease
NOD2 encodes a protein that binds to intracellular bacterial and than activates NF-κB.
NOD-2 mutation is ineffective at defending against intestinal bacteria.
• The result is that bacteria are able to enter through the epithelium into the wall of the intestine, where they trigger reactions.*
peptidoglycans
inflammatory
Polarization of helper T cells to the TH1 type is recognized in disease, and some data suggest that TH17 T cells also contribute to disease pathogenesis.*
Crohn
defects in intestinal epithelial barrier function occur in patients with Crohn disease and a subset of their healthy first-degree relatives
tight junction
In a genetically susceptible host, the subsequent release of and other immune signals directs epithelia to increase tight junction permeability, which further increases the flux of luminal material
TNF
Crohn disease, also known as regional enteritis, may occur in any area of the gastrointestinal tract but the most common sites involved at presentation are the terminal ileum, ileocecal valve, and .
cecum
The earliest lesion, the ulcer, may progress, and multiple lesions often coalesce into elongated, serpentine ulcers oriented along the axis of the bowel.
• Sparing of interspersed mucosa results in a coarsely textured,
appearance in which diseased tissue is depressed below the level of normal mucosa.
• frequently develop between mucosal folds and may extend deeply to become sites of perforation or fistula tracts
aphthous
cobblestone
Fissures
The intestinal wall is thickened as a consequence of edema, inflammation, submucosal fibrosis, and hypertrophy of the muscularis propria, all of which contribute to stricture formation.
• In cases with extensive transmural disease, frequently extends around the serosal surface (creeping fat)
transmural
mesenteric fat
The microscopic features of active Crohn disease include abundant
that infiltrate and damage crypt epithelium.
- Clusters of within a crypt are referred to as a crypt abscess and often are associated with crypt destruction.
- Ulceration is common in Crohn disease, and there may be an abrupt transition between ulcerated and normal mucosa.
- Repeated cycles of crypt destruction and regeneration lead to distortion of mucosal ; the normally straight and parallel crypts take on bizarre branching shapes and unusual orientations to one another
neutrophils
neutrophils
architecture
What is a hallmark of Crohn disease, are found in approximately 35% of cases and may arise in areas of active disease or uninvolved regions in any layer of the intestinal wall?
Noncaseating granulomas
As concerning Crohn’s
develop between loops of bowel and may also involve the urinary bladder, vagina, and abdominal or perianal skin.
• Perforations and peritoneal can also occur.
Fistulas
abscesses
What always involves the rectum and extends proximally in a continuous fashion to involve part or the entire colon that can be diffusely ulcerated.
• Skip lesions are not seen.
Ulcerative colitis
Disease of the entire colon is termed
- Disease limited to the rectum or rectosigmoid may be referred to descriptively as ulcerative or ulcerative proctosigmoiditis.
- The small intestine is normal, although mild mucosal inflammation of the distal ileum, , may be present in severe cases of pancolitis.
pancolitis.
proctitis
backwash ileitis
Grossly, involved colonic mucosa may be slightly red and granularappearing or exhibit extensive broad-based ulcers.
- The transition between diseased and uninvolved colon can be
- Isolated islands of regenerating mucosa often bulge into the lumen to create small elevations, termed
abrupt.
pseudopolyps.
Concerning ulcerative colitis
Chronic disease may lead to mucosal and a flat, smooth mucosal surface.
- Unlike in Crohn disease, mural thickening is absent, the serosal surface is normal, and strictures do not occur.
- Inflammation and inflammatory mediators can damage the muscularis propria and disturb neuromuscular function leading to colonic dilation and toxic , which carries a significant risk for perforation.
atrophy
megacolon
inflammatory infiltrates, crypt abscesses, crypt distortion, and epithelial metaplasia are both in UC and Crohns
However
Skip lesions and granulomas are not present in UC/Crohns?
UC
is a relapsing disorder characterized by attacks of bloody diarrhea with expulsion of stringy, mucoid material and lower abdominal pain and cramps that are temporarily relieved by defecation.
Ulcerative colitis
Those with UC and what other condition have greater risk of developing dysplasia?
primary sclerosing cholangitis
Acute appendicitis is thought to be initiated by progressive increase in intraluminal pressure that compromises outflow.
- In 50%-80% of cases, acute appendicitis is associated with overt luminal obstruction, usually by a small, stone-like mass of stool, or , or, less commonly, a gallstone, tumor, or mass of worms.
- Ischemic injury and stasis of luminal contents, which favor bacterial
, trigger inflammatory responses including tissue edema and neutrophilic infiltration of the lumen, muscular wall, and periappendiceal soft tissues.
venous
fecalith
proliferation
In early acute appendicitis, subserosal vessels are congested, and a modest perivascular neutrophilic infiltrate is present within some/all layers of the wall.
- The inflammatory reaction transforms the normal glistening serosa into a , granular-appearing, erythematous surface.
- The diagnosis requires infiltration of the muscularis propria.
all
dull
neutrophilic
In more severe cases, focal abscesses may form within the wall, and these may even progress to large areas of hemorrhagic ulceration and gangrenous necrosis that extend to the serosa, creating acute appendicitis, which often is followed by rupture and suppurative
gangrenous
peritonitis.
Typically, early acute appendicitis produces periumbilical pain that ultimately localizes to the lower quadrant, followed by nausea, vomiting, low-grade fever, and a mildly elevated peripheral white blood cell count.
• A classic physical finding is sign, deep tenderness noted at a location two-thirds of the distance from the umbilicus to the right anterior superior iliac spine (McBurney’s point).
right
McBurney’s
