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?
What is the most common obstruction worldwide and 1/3 most common in US?
Any weakness or defect in the abdominal wall may permit protrusion of a serosa-lined pouch of peritoneum called a
Acquired hernias typically occur anteriorly/posteriorly, via the inguinal and canals, umbilicus, or at sites of surgical scars,
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.
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
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.
• are the most common cause of intestinal obstruction in the United States.*
Sequelae, include obstruction and strangulation.
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 most often in large redundant loops of colon, followed in frequency by the cecum, small bowel, stomach, or, rarely, transverse colon
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.
Intussusception is the most common cause of intestinal obstruction in children less than years of age.
Instussusception is associated with viral infection, rotavirus vaccines, reactive of Peyer’s patches
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
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.
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.
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.) ?
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
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
Infarction is frequently segmental and patchy.
• The mucosa is hemorrhagic and often .*
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.
note: the neutrophils and the sloughing up top
ischemia is accompanied by fibrous scarring of the lamina propria and, uncommonly, stricture formation.
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.
Acute transmural infarction typically manifests with sudden, severe abdominal pain and tenderness, sometimes accompanied by nausea, vomiting, bloody diarrhea, or grossly stool
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
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%.*
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.
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?
What are some predisposing factors for hemorrhoids?
increased intraabdominal and venous pressure
venous stasis of pregnancy
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
sclerotherapy, rubber band ligation, and infrared coagulation are treatments for which condition?
Systemic vasculitides and infectious diseases (CMV) can cause vascular disease that is/is not confined to the gastrointestinal tract.
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.
Diverticula generally are multiple, and the condition is referred to as
less common in developing countries,
Colonic diverticula tend to develop under conditions of elevated
pressure in the sigmoid colon
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.
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.
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
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
Concerning diverticular disease:
Most individuals with diverticular disease remain asymptomatic/symptomatic
complaints including intermittent cramping, continuous lower abdominal discomfort, constipation, and
most often resolves spontaneously or after treatment, and relatively few patients require surgical intervention
What is a chronic condition resulting from complex interactions between intestinal microbiota and host immunity in genetically predisposed individuals resulting an inappropriate mucosal immune activation?
Inflammatory bowel disease (IBD)
What are the 2 types of IBD?
Crohn disease and ulcerative colitis.
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.
When do Crohn disease and ulcerative colitis frequently present:
mostly adolescence or in young adults
after the fifth decade
IBD is most common among whites and is 3 to 5 times more often among eastern
European (Ashkenazi) Jews.
Most investigators believe that IBD results from the combined effects of alterations in host interactions with intestinal , intestinal epithelial , aberrant mucosal immune responses, and altered composition of the gut microbiome.
Genetic factors are more prominant in Crohn’s/UC?
Molecular linkage analyses of affected families have identified (nucleotide oligomerization binding domain 2) as a susceptibility gene in 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.*
What other genes are associated with IBD other than NOD 2?
autophagosome pathway and, like NOD-2, are involved in host cell responses supporting the hypothesis that inadequate defense against luminal bacteria may be important in the pathogenesis of IBD
ATG16L1 (autophagy-related 16–like-1) and IRGM (immunity-related GTPase M) genes.
immunosuppressive and agents remain mainstays of IBD therapy.
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.*
Some data suggest that mucosal production of the TH 2- derived cytokine IL-13 is increased in and, to a lesser degree, Crohn disease
defects in intestinal epithelial barrier function occur in patients with Crohn disease and a subset of their healthy first-degree relatives
One model that unifies the roles of intestinal microbiota, epithelial function, and mucosal immunity suggests a cycle by which flux of luminal bacterial components activates innate and adaptive immune responses.
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
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 .
The presence of multiple, separate, sharply delineated areas of disease, resulting in , is characteristic of Crohn disease and may help in differentiation from ulcerative colitis.
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
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)
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
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?
What are some of the many symptoms of Crohn’s
relatively mild diarrhea, fever, and abdominal pain.
right lower-quadrant pain and fever
Concerning Crohn’s, Disease reactivation can be associated with a variety of external triggers, including physical or emotional , specific dietary items, NSAID use, and smoking
-deficiency anemia may develop in individuals with Chrohn’s colonic disease.
Extensive small-bowel disease may result in serum loss and hypoalbuminemia, generalized nutrient malabsorption, or malabsorption of vitamin and bile salts.
Fibrosing particularly of the terminal ileum, are common and require surgical resection.
• Disease often recurs at the site of , and as many as 40% of patients require additional resections within 10 years.
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.
Extraintestinal manifestations of Crohn disease include , migratory polyarthritis, sacroiliitis, ankylosing spondylitis, erythema nodosum, and clubbing of the fingertips, any of which may develop before intestinal disease is recognized.
Pericholangitis and primary sclerosing cholangitis may occur in Crohn disease but are more common in
The risk for development of colonic is increased in patients with long-standing colonic Crohn disease
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.
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.
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
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.
inflammatory infiltrates, crypt abscesses, crypt distortion, and epithelial metaplasia are both in UC and Crohns
Skip lesions and granulomas are not present in UC/Crohns?
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.
With UC, the onset of symptoms can occur shortly after smoking in some patients, and smoking may partially relieve symptoms.
Extraintestinal manifestations of UC, similar to Crohn’s:
migratory polyarthritis, sacroiliitis, ankylosing spondylitis, uveitis, skin lesions, pericholangitis, and primary sclerosing cholangitis.
In UC, colectomy cures intestinal disease, but extraintestinal manifestations may/may not persist
What 3 factors are related to the development of colitis associated dysplasia:
Duration of disease - Risk increases beginning 8-10 years after disease initiation.
• Extent of involvement - Patients with pancolitis are at greater risk than those with only left-sided disease.
• Inflammation - Greater frequency and severity of active inflammation (characterized by the presence of neutrophils) may increase risk.
Those with UC and what other condition have greater risk of developing dysplasia?
primary sclerosing cholangitis
Acute appendicitis is most common in and young adults but may occur in any age group.
Females/Males are affected slightly more
may be confused with mesenteric lymphadenitis, acute salpingitis, ectopic pregnancy, mittelschmerz (pain associated with ovulation), and Meckel diverticulitis.
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.
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.
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
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).