What are four mechanial causes of obstruction?
What are some ssx of GI obstruction?
•Crampy abdominal pain that comes and goes.
•Inability to have a bowel movement or pass gas.
•Swelling of the abdomen (distention
What are four clinical criteria that may be used as a sign of strangulation?
- Local Tenderness
- Upper left: Herniation
- Upper right: Adhesions
- Lower Left: Volvulus
- Lower Right: Intussusception
What does this radiograph show, and what does it indicate?
Upright abdominal X-Ray with multiple air fluid levels in intestines that indicate obstruction
What are the most common populations this occurs in?
•Most common cause of intestinal obstruction in children younger than two years of age (typically between 5-9 months)
•Twice as frequent in males than females
Of intussusception cases, 90% are idiopathic. 10% involve a discrete lead point. The telescoping can produce obstruction, ischemia, and eventual strangulation of the bowel. What are 5 common lead points where this happens?
- Meckel's Diverticulum
- Intestinal Polyps
- Neoplastic lesions
- Foreign bodies
What are three associations to be aware of related to intussusception?
- Viral illness - specifically Adenovirus
- Rotavirus Vaccine (apparently only with the old version per michael)
- Peyer patch lymphoid hyperplasia
What do you see in this x-ray? What is is classic for?
"coffee bean" sign
Classic image finding for Volvulus
Volvulus is most common in adults occuring with equal frequency in small intestine (around a twisted mesentery) and colon (in either sigmoid or cecum.
Where does it typically occur in very young children?
Nearly always in the small intestine
What is this?
An external inguinal hernia is a protrusion of a serosa-lined pouch of peritoneum called a hernia sac. Where do these typically occur?
Anteriorly, via inguinal and femoral canals, also the umbilicus and surgical scar sites.
Obstruction often occurs d/t external inguinal hernias because of visceral protrusion into the hernia sac. What structures are commonly involved?
With prolonged incarceration what are some dangers?
Small bowel loops are typically involved, leads to:
- danger of perforation
What is the most common cause of intestinal obstruction in the US?
What are three examples?
What is this and how did it happen?
Fibrous bridges create closed loops through which other loops can slide through and become entrapped…
"Lower GI bleeding" refers to a bleed where?
Distal to ligament of Treitz
Which is more commonly the cause of lower GI bleeds, Colorectum or small intestine?
Lower GI bleeds are most common in the 7th decade, and may not be visible to the patient if chronic/low grade. What is a big tip off that would point to a chronic GI bleed?
Iron deficiency anemia - hypochromic microcytic anemia
What are two common causes of lower GI bleeding we discussed in this lecture?
Besides diverticulitis and angiodysplasia, what are some other important causes of lower GI bleeding?
•Inflammatory Bowel Disease
•Ischemia (watershed zones) > 70 yo
Angiodysplasia is a common cause of lower GI bleeding in elderly patients (acquired lesions associated with aging), with an unknown pathogenesis. This accounts for 20% of significant lower GI bleeding. What happens in this condition?
Proliferation of tortuously dilated and malformed submucosal and mucosal blood vessels.
What is seen in the images here taken from a 77 y/o female with fatigue, pallor and digital clubbing?
Note the dilated small vessels of the lamina propria in the image on the right
What is mesenteric angina?
•acute mesenteric ischemia, commonly present with abdominal pain and hematochezia.
Paradoxically, elderly patients (who are the most prone to ischemia from arterial insufficiency) often experience little or no pain until the disease is far advanced. What areas are most prone to ischemic bowel disease?
Watershed areas: Tissue at terminal segments of arterial circulation
The vast majority of lower GI ischemia is d/t arterial insufficiency (85-95%). Of this cause, sources can be either occlusive ischemia (~70%) or nonocclusive mesenteric ischemia, in essence inadequate arterial blood flow (~25%).
What are four causes of nonocclusive mesenteric ischemia?
- Systemic hypotension
What are five examples of causes of occlusive lower GI ischemia?
- Atheromatous emboli (50%)
- Thrombus (10%)
- Dissecting aneurysm
Venous insufficiency is responsible for a mere 10% of lower GI ischemia, and typically occurs in younger patients with an initial presentation of abdominal pain.
What are three causes of this?
•External venous compression
•Mesenteric venous thrombosis
•Hypercoagulable states (genetic and acquired)
The small intestine and colon can tolerate slowly progressive loss of blood supply, but acute compromise of any major vessel can lead to infarction of several meters of intestine. What are the two types of infarcts seen in ischemic bowel disease?
Superficial mucosal infarction
Describe a superficial mucosal infarction.
Extends no deeper than the muscularis mucosa. (Starts at the mucosa)
Describe a transmural infarction.
Involves all three wall layers, Mucosa, muscularis mucosae, submucosa, muscularis propria, and extends to the serosa.
Describe the two damage phases of intestinal ischemia. Which is worse?
•The initial hypoxic injury occurs at the onset of vascular compromise.
•The second phase, reperfusion injury, is initiated by restoration of the blood supply and it is at this time that the greatest damage occurs.
What are the mechanisms of reperfusion injury in the intestine?
–leakage of gut lumen bacterial products- lipopolysaccharide into the systemic circulation
–free radical production and neutrophil infiltration
What is shown in each of these photos?
Left/top: normal unfixed small intestine
Bottom/right: Early ischemic enteritis involving the tips of the villi. (Hyperemic)
Which is quantitatively greater as far as absorption and secretion in the GI system?
What happens if you have either a decrease in absorption or an increase in secretion?
What are the classes of diarrhea? 6
Watery diarrhea impies either?
Secretory or osmotic
Fatty diarrhea implies?
defective absorption of fat and perhaps other nutrients in the small intestine.
Inflammatory diarrhea implies the presence of one of a limited number of inflammatory or neoplastic diseases involving the GI tract, and will present with?
Purulent or bloody stools
What impact does fasting have on secretory diarrhea?
What is the usual etiology?
•persists during fasting
•usually infectious; viral or enterotoxin
What impact does fasting have on osmotic diarrhea?
What is this classically d/t?
•abates with fasting
•classically lactase deficiency
Exudative diarrhea occurs d/t mucosal damage and leads to purulent or bloody stools. What impact does fasting have?
What is the typical etiology?
•persists during fasting
•usually bacterial or IBD
Gastrointestinal infections are a major cause of morbidity and mortality worldwide. Most cases of infectios enterocolitis require what treatment?
None, most are self limited
Viral infections most commonly cause what type of diarrhea?
Bacterial infections are common causes of what type of diarrhea?
What are some symptoms of enterocolitis? 5
•Diarrhea (watery and/or bloody)
What are the four pathogenic mechanisms of bacterial enteritis?
- Ingestion of preformed bacterial toxins
- non-invasive bacteria that secrete toxins
Intracellular invasion of the intestinal epithelia cells
- Bacteria that enter the blood stream via the intestinal tract
What are some examples of bacteria that cause bacterial enteritis via preformed bacterial toxins?
- S. Aureus
- B. Cereus
- C. Botulinum
- C. Perfringens
What are some examples of non-invasive bacteria that secrete toxins while adhered to the intestinal wall and cause bacterial enteritis?
- Enterotoxigenic E. coli
- Vibrio cholerae
- C. Jejuni
What are two examples of bacteria that cause bacterial enteritis via intracellular invasion?
What are two examples of bacteria that enter the blood stream via the intestinal tract?
S. Aureus produces enterotoxins while growing/multiplying in food supplies. What do the staphylococcal enterotoxins do?
Act as superantigens, which among other things induces diarrhea
Most who are exposed to V. cholerae are asymptomatic or have only mild symptoms. Occasionally it can kick your ass though. What can severe dehydration lead to?
•Severe disease can lead to dehydration, hypotension shock and death in 24 hrs.
By what mechanism does V. cholerae cause bacterial enteritis?
•Vibrio cholera produces multiple toxins that affect ion secretion and absorption resulting in increased Na and Cl ions in the lumen.
E. coli is classified according to morphology, serotyping, mechanism of pathogenesis, and in vitro behavior. What are the major subgroups with clinical relevance? 5
–Enterotoxigenic E. coli (ETEC)
–Enteropathogenic E. coli (EPEC)
–Enterohemorrhagic E. coli (EHEC)
–Enteroinvasive E. coli (EIEC)
–Enteroaggregative E. coli (EAEC).
What kind of diarrhea does ETEC cause?
What diarrhea is EPEC associated with?
What are two associations to be aware of for EHEC?
Hemolytic uremic syndrome
What should you think of when you hear EIEC?
In what patients does EAEC cause diarrhea?
Children and HIV patients
ETEC is a major cause of traveler's diarrhea and infects what?
Characterize this organism based on invasion and toxin production.
The small intestine.
Non-invasive (non-bloody diarrhea)
Produces secretory toxins that cause non-inflammatory diarrhea
EPEC causes non-invasive, non-bloody diarrhea in infants. What part of the intestine does it infect?
What lesions does it cause?
Infects the small intestine
•Attaching and effacing mucosal lesions
Describe EHEC in terms of diarrhea, part of intestine affected and toxins.
- Bloody diarrhea with severe abdominal pain.
- Affects large intestine
- Produces a cytotoxin similar to that of Shigella (Shiga like toxin)
We can use antibiotics to treat EHEC, but...
This appears to increase the risk of hemolytic uremic syndrome
EIEC affects the large intestine, and is similar to shigella genetically. Describe the toxin production, and the method of damage to the epithelium.
What does this produce symptom wise?
•Do not produce toxins
•Invade epithelial cells (this causes damage)
•Produce a severe, dysentery-like illness as well as bacteremia
EAEC causes diarrhea in children and adults, leading to non-bloody diarrhea. In what patients is this most problematic and what does it cause?
How does it do its dirty work?
•Causes of chronic diarrhea and wasting in AIDS patients
The most common enteric pathogen in the developed world is a gram negative curved bacillus that is invasive. What is it?
Its toxins are similar to those of what other organism?
Toxins are similar to cholera
C. Jejuni gastroenteritis is clinically indistinguishable from that caused by other enteric pathogens. What are two pretty specific associations that we should know regarding C. jejuni?
•Associated with reactive arthritis in patients with HLA-B27
•Guillain-Barre syndrome is post infection complication (1 in 2000 infections). Can happen months post infection.
What is a pretty classic description of C. jejuni?
Faint Gram negative curved rods which may be gull-winged in shape
Shigella is a virulent invasive organism that causes bloody diarrhea, and is resistant to the acid of the stomach.
What does the shiga toxin do?
What does it cause that can be seen on gross inspection?
•Shiga toxin Stx, inhibits eukaryotic protein synthesis
•Cause aphthous-appearing ulcers similar to those seen in Crohn disease.
Salmonella enteritidis features are nonspecific and are similar to acute self-limited colitis.
Salmonella typhi on the other hand, causes?
Typhoid fever, and can disseminate via lymphatic and blood vessels.
When salmonella typhi causes typhoid fever and disseminates via lymphatic and blood vessels, what does this cause throughouth the body?
reactive hyperplasia of phagocytes and lymphoid tissues
Yersinia enterocolitica strains are usually confined to the intestinal tract and lead to enteritis/diarrhea. What are some possible post infectious complications?
- reactive arthritis with urethritis and conjunctivitis,
- erythema nodosum
- kidney disease.
Y. pseudotuberculosis has symptoms of? and mimics?
Fever and abdominal pain mimicking appendicitis (actually from mesenteric lymphadenitis)
What are three organisms that produce a pseudomembranous pattern of damage in the intestine.
- Clostridium difficile
- Enterohemorrhagic E. coli
What are four types of organisms that produce a granulomous reaction in the GI tract?
- Yersinia sp.
What is a cause of macrophage proliferation in the intestine?
Whipple disease- Tropheryma whippelii
What would you call this?
•Acute colitis characterized by formation of an adherent layer of inflammatory cells and debris overlying sites of mucosal injury
When does C. diff overgrowth and toxin production typically occur?
Following normal flora loss d/t antibiotic use. (antibiotic associated colitis)
What is the diagnostic test for C. diff?
C. difficile cytotoxin in stool
What is shown here?
What is shown here?
What characteristic feature of pseudomembranous colitis is shown here?
Pseudo-membranes feature “volcano” eruption of inflammatory exudate (arrows)
Norovirus is the most common cause of acute gastroenteritis requiring medical attention in US. This is second only to what other virus in causing severe diarrhea in infants and young children?
What are the main methods by which norovirus is transmitted?
•Local norovirus outbreaks are usually related to contaminated food or water, but person-to-person transmission underlies most sporadic cases.
Rotavirus is a common cause of severe childhood diarrhea and diarrheal mortality worldwide. What does it infect/destroy?
What does this lead to?
•Rotavirus selectively infects and destroys mature enterocytes in the small intestine
•Loss of absorptive function and net secretion of water and electrolytes
Adenovirus is a major cause of childhood diarrhea, and also hits immunocompromised patients. What is it associated with in children?
Ileal and Cecal intussusception
Cryptosporidium parvum was considered a very rare pathogen until AIDS epidemic. Since then it has been an important cause of diarrhea and is usually spread via contaminated drinking water.
Where does it most often concentrate?
Terminal ileum and right colon
What is the cause of this patients diarrhea?
What is causing this AIDs patients diarrhea?
Bonus point - What must this patient's CD4 count be below?
Mycobacterium avium intracellulare
CD4 count under 100
What are some important nematodes to know that cause parasitic enterocolitis?
Ascaris - most common
What are some unicellular parasites that cause parasitic enterocolitis?
–Entamoeba histolytica (ameba)
Giardiasis is the leading GI protazoal disease in the US, with an overall prevalence of 2% to 7%. What is a particularly high reservoir for this?
Day care centers, prevalence reaches 35%
Endoscopic examination is generally unremarkable, and small intestinal biopsies are often normal in appearance/mild villous blunting.
What tissues are typically invaded by giardia?
Tissue invasion is not a feature of this infection.
Cysts and trophozoites of giardia lamblia can both be found in feces. What forms are responsible for transmission of giardia?
What form is resistant?
•Cysts are resistant forms and are responsible for transmission of giardiasis
What is shown in these samples obtained from a patients duodenal mucosa?
Describe the morphological features of your finding.
A. Duodenal mucosa with numerous Giardia trophozoites at the luminal surface
B. Higher-power view shows the typical pear-shaped morphology with two prominent nuclei.
Entamoeba histolytica is a dysentery causing protozoa that can also cause fulminant colitis, with a high incidence in homosexual men and AIDS patients.
What do they tend to invade/create?
Amoeba invade colonic crypts, burrow into lamina propria, create flask shaped ulcer with broad base
What is a somewhat interesting/terrifying risk associated with entamoeba histolytica?
•40% invade portal vessels, embolize to liver and cause abscesses up to 10 cm
•Rarely see abscesses in liver, lung, heart, kidneys, brain
What do you see in each image?
B: A side-view of the classical flask-shaped ulcer seen in amebic colitis
C: histolytica trophozoites (arrows) taken from an ulcer, showing the presence of numerous ingested red blood cells