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33 Cards in this Set
- Front
- Back
Small Intestine
Congenital Disorders Name 5 |
o Atresia or stenosis
o Duplications and enteric cysts o Malrotations o Herniations o Meckel's diverticulum |
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Small Intestine
Congenital Disorders 1) Atresia refers to _________ 2) while stenosis refers to _________ 3) Both are rare and present in the early post-natal period with ___________ |
1) refers to the complete absence of the intestinal lumen
2) describes partial occlusion 3) obstruction and affect only a segment of bowel |
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Small Intestine
Congenital Disorders Meckel’s Diverticulum (most common) |
- Results from persistence of the vitelline duct
- “Blind pouch” 5-6 cm in length - Antimesenteric border of ileum (approx. 85 cm from cecum) - Usually asymptomatic/incidental - Can present with symptoms due to bacterial overgrowth, mechanical alterations (e.g. intussusception) or ectopic mucosa - Ectopic gastric mucosa can elaborate gastric secretions and lead to peptic ulceration, which can be complicated by perforation or fistula formation. Inflammation and hemorrhage can also be associated with obstruction. |
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SMALL BOWEL OBSTRUCTION
T/F In general, obstruction is less common in the small intestine than the large intestine |
False
In general, obstruction is MORE common in the small intestine than the large intestine, because of the smaller lumen and its more mobile mesenteric attachments. |
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SMALL BOWEL OBSTRUCTION
Mechanical obstructions can result secondary to: |
o hernias
o intestinal adhesions o intussusception or volvulus o tumors or inflammatory strictures o gallstones or foreign bodies o congenital strictures or atresias |
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Of the ones just listed, the major causes of small bowel obstruction are:
(name 4) |
hernias, intestinal adhesions, intussusception, and volvulus
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SMALL BOWEL OBSTRUCTION
Hernias lead to entrapment of bowel and obstruction or ischemic necrosis (strangulation). Permanent entrapment of bowel is often referred to as an __________ |
loops of small intestine (or omentum and other organs) can herniate through congenital or acquired defects in the abdominal wall leading to _______
incarcerated hernia. |
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SMALL BOWEL OBSTRUCTION
Adhesions caused by |
Inflammation of the peritoneum that can lead to the formation of fibrous adhesions between bowel segments and/or the abdominal wall.
They can entrap bowel as described for hernias.. |
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SMALL BOWEL OBSTRUCTION
Intussusception refers to |
the telescoping of proximal bowel into the immediately distal segment.
It is unusual in adults unless accompanied by an intraluminal mass which is ‘grabbed’ by a contracting segment and gets pulled into it with it’s associated wall. |
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SMALL BOWEL OBSTRUCTION
Volvulus refers to |
the twisting of a loop of bowel with resultant ischemia secondary to venous and sometimes arterial obstruction.
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Vascular Diseases
Acute Intestinal Ischemia can be caused by 4 separate phenomena: |
Arterial occlusion
Venous thrombosis Non-occlusive Volvulus, Adhesions, or Herniation |
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Vascular Diseases
Acute Intestinal Ischemia Clinical presentation: Pathology: Complications: |
Clincal Presentation:
Abdominal pain, bloody diarrhea Pathology: - Segmental congestion, edema, hemorrhage - Mucosal to transmural necrosis Complications - Adynamic ileus, perforation with peritonitis, “free air”, and septicemia What is this? |
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Malabsorption
Name the causes and examples of diseases (5 causes) |
- Abnormal Intraluminal Digestion (e.g., pancreatitis, cystic fibrosis)
- Primary abnormalities of the lining epithelium (enterocytes) Terminal digestion - defective hydrolysis of carbohydrates and peptides at the brush border (e.g, disaccharidase deficiency) Abnormal transepithelial transport of fluids and nutrients (e.g., abetalipoproteinemia) - Decreased absorptive surface area (e.g., Celiac disease, Crohn's disease, surgical resection) - Lymphatic obstruction (e.g., lymphoma or tuberculosis) - Infection (e.g., Whipple's disease) |
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Malabsorption
Lactose Intolerance is an example of: |
example of defective mucosal cell absorption.
This is a deficiency of disaccharidase in the brush border of the enterocyte which leads to buildup of carbohydrates in the lumen with subsequent bacterial overgrowth, diarrhea, gas, and bloating. |
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Malabsorption
Abetalipopoteinemia |
example of a genetic deficiency in a mucosal enzyme.
This is a rare autosomal recessive disorder characterized by a deficiency of apoprotein B, which is required for the assembly of chylomicrons. As a result, the mucosal epithelial cell is unable to export lipids. Presents in infancy with diarrhea and steatorrhea with failure to thrive. It is also associated with abnormalities in myelinization and cell membrane formation.The cells contain lipid vacuoles, but the mucosa otherwise appears normal. Histologically characterized by acanthocytes (spiny cells) |
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Malabsorption
Celiac Disease |
example of a non-infectious disease associated with decreased absorptive surface area.
results from immunologic hypersensitivity (CD4 T-cell mediated) to cereal proteins (gliadin peptides). The disease is responsive to a gluten-free diet and is often known as gluten-sensitive enteropathy. There is a strong genetic component (HLA-DQ2) |
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Clinically it can be associated with a cutaneous disease known as dermatitis herpetiformis and there is a modest increase in risk for lymphoma.
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Malabsorption
Celiac Disease |
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Histology of Celiac Sprue:
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The small bowel shows a very typical but nonspecific response to immune-mediated injury with flattening or blunting of the villi, giving an appearance that more resembles large bowel mucosa.
The glandular and surface epithelium is infiltrated by activated T cells, and there is associated intense infiltration of the lamina propria by lymphocytes and plasma cells. |
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MALABSORPTION
Whipple's Disease an example of: (It is caused by a gram-positive bacterium, Tropheryma whippelii) |
example of an infectious disease.
- a systemic infectious disorder that typically involves the small intestine with malabsorption and has frequent involvement of joints, central nervous system, and other organs. Its protein and chronic manifestations make it very hard to diagnose. Humans are the only known host and patients with the infection usually have some mild form of underlying immunodeficiency. Histologically characterized by infiltration of the lamina propria of the small intestine by foamy PAS-positive macrophages that contain the microorganisms. The inflammatory reaction can interfere with nutrient export via lymphatics. |
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Infectious Enterocolitis
Can be from 3 sources: |
1) Bacterial
Toxigenic bacteria - diarrhea Invasive bacteria - dysentery 2) Viral Viral gastroenteritis 3) Parasitic |
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Most common parasitic infection in the US is?
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The most common in the US is Giardiasis (flagellated protozoan)
(Giardiasis) - attach to enterocytes in proximal small intestine and deconjugate bile salts All are associated with ingestion of fecal contaminants. |
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Infectious Enterocolitis
Toxigenic bacteria - diarrhea (primarily affects which part of the small intestine?) Invasive bacteria - dysentery (primarily affects which part of the small intestine?) |
Toxigenic bacteria (diarrhea) - associated with the release of enterotoxins that alter epithelial function in the proximal small intestine
Invasive bacteria (dysentery) - commonly involve the distal small intestine (and colon) |
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CROHN'S DISEASE - A TYPE OF INFLAMMATORY BOWEL DISEASE
Define and characterize: |
an idiopathic systemic inflammatory disease that involves the intestines
Deranged mucosal immunity Abnormal cytokines, receptors, T-cells Probably elicited by microorganisms or microbial products in susceptible host 20% CARD-15 mutations – protein in epithelial cell/antigen interaction Antibodies – anti-Saccharomyces cerivisiae, p-ANCA, anti-E.coli outer membrane protein Paneth cells – ATG16/1 |
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CROHN'S DISEASE - A TYPE OF INFLAMMATORY BOWEL DISEASE
Clinical Presentation; |
Abdominal pain, bloody diarrhea, malabsorption (loss of surface area), fever, and sometimes a palpable abdominal mass.
Characterized by remissions and exacerbations of active disease over a several years. Intestinal obstruction and fistulas are common complications. Apthous ulcers, perianal fissures Cutaneous, ocular and hepatic manifestations Increased risk of bowel carcinoma |
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Crohn’s DiseasePathology
Gross Presentation |
Classically involves the terminal ileum but can involve the colon and more proximal GI tract (40/30/30)
Segmental disease with “skip lesions” Thickened wall with narrowed lumen Longitudinal serpentine ulcers and cobblestoned mucosa Serosal “fat wrapping” or “creeping fat” Regional lymphadenopathy |
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Crohn’s Disease
Histopathology: |
Transmural chronic inflammation or fibrosis
Mucosal ulceration Non-specific mucosal injury (cryptitis, crypt abcesses) Epithelioid granulomas (40-50%) Architectural disarray |
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Neoplasms Benign Tumors
Several types: (4) |
Adenomas
- Tubular or villous, most common in the duodenum - Peutz-Jeghers syndrome Hamartomatous polyps Lipomas Leiomyomas |
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Malignant Neoplasms
Small Intestine Adenocarcinomas T/F Adenocarcinomas are the most common small intestinal malignant neoplasm (approximately 50%). They are virtually identical in appearance to enteric colon cancers. |
True
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Malignant Neoplasms
Small Intestine Adenocarcinomas Risk factors include _________ and ________ Consistent with the distribution of adenomas, they are most common in the ________. These tumors can occur at the ampulla of Vater and present with ________________ |
FAP and Crohn's
duodenum obstructive jaundice. |
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Neoplasms
Carcinoid tumors Define and characterize presentation: Classic Histological presentation: |
Endocrine differentiation
(resemble pancreatic islet cells --> neuroendocrine cells) Approximately 20% of small bowel malignancies can arise in: - Terminal ileum (~2/3) - Meckel’s diverticulum - Duodenum (gastrinomas) 25-30% multifocal Small (most <2cm) Classic Histological presentation: Salt and Pepper nuclei (classic for neuroendocrine tumors) |
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Carcinoid tumors
The tumors can have __________ submucosal growth patterns and have a homogeneous _________ color |
polypoid or circumferential
yellow |
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Carcinoids are often associated with a prominent desmoplastic response, which can lead to _________________.
T/F Like appendiceal and rectal carcinoids, they do not frequently metastasize. |
kinking of the bowel with resultant obstruction
False: Unlike appendiceal and rectal carcinoids, they frequently metastasize, and the risk of metastasis correlates with tumor size. Tumors with a diameter of > 2 cm are considered malignant regardless of their histological features. |
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T/F
Gastrointestinal lymphomas do not involve bone marrow, spleen or liver at the time of diagnosis |
True
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