Gi uworld 1 Flashcards
Hematochezia, Tc-pertechnetate scintigraphy demonstrates focal radiotracer accumulation in the right LQ. failed embryologic process?
failed obliteration of the vitelline duct
- Meckel diverticulum: incomplete closure of the vitelline duct results in an ileal outpouching with a fibrous connection to the umbilicus
Meckel’s diverticulum contains ectopic gastric mucosa. secretion of HCl causes small bowel ulceration and bleeding (painless lower Gi bleeding) and anemia.
failure of craniocaudal neural crest cell migration results in aganglionic sigmoid colon/rectum that is narrow and inactive
Hirschsprung disease
abnormal midgut rotation around the SMA
intestinal malrotation.
Zenker diverticulum - cricopharyngeal motor dysfunction
abnormal spasms or diminished relaxation of the cricopharyngeal muscles during swallowing (underlying mechanism).
- results in oropharyngeal dysphagia with a feeling of food obstruction at the level of the neck and coughing/choking.
- increases oropharyngeal intraluminal pressure results in herniation of the pharyngeal mucosa through the zone of muscle weakness (false diverticulum) in the posterior hypopharynx (Killian triangle)
- patients develop food retention with halitosis/regurgitation.
pulmonary aspiration of diverticular contents may lead to recurrent pneumonia.
degenerative changes in the myenteric plexus with impaired LES relaxation. barium swallow shows esophageal dilation with esophagogastric junction narrowing (Birds beak)
Achalasia
Rifaximin MOA in hepatic encephalopathy
decreased intraluminal ammonia production.
- Rifaximin is a nonabsorbable antibiotic that alters GI flora to decrease intestinal production and absorption of ammonia. (usually given with lactulose), which is catabolized by intestinal bacterial flora to short-chain FAs, lowering colonic pH and increasing the conversion of ammonia to ammonium.
- it is also used for traveler’s diarrhea, as it inhibits bacterial RNA synthesis through bindings with DNA-dependent RNA polymerase.
lactulose MOA in hepatic encephalopathy
increased conversion of ammonia to ammonium ions
hepatic encephalopathy
due to cirrhosis (liver’s inability to convert ammonia to urea). crosses BBB and causes altered mental status (impaired neurotransmitter release, astrocyte dysfunction, neuroinflammation, and/or edema). Asterixis (flapping tremor) is also common.
food protein-induced allergic proctocolitis
eosinophilic infiltration of the distal colon
benign condition of early infancy (<6 months).
- infants have a non-IgE-mediated reaction to proteins found in breast milk or formula (common trigger is cows milk)
painless, blood-streaked stools (loose stools with mucus) develop weeks to months after initial exposure to the food allergen
findings:
- inflammation (erythema, edema) confined to the distal colon and rectum
- histopathology findings include infiltration of eosinophils within the lamina propria and muscularis mucosa.
hemorrhagic necrosis of the bowel wall
Necrotizing enterocolitis. results in Gut ischemia and death if untreated.
- rectal bleeding, abdominal distension, poor feeding, hemodynamic instability
neutrophilic crypt abscesses
ulcerative colitis
Cystic fibrosis
pancreas: distension and obstruction of pancreatic ducts (pancreatic insufficiency). obstruction and distension is due to viscous mucus and inflammation.
- recurrent sinopulmonary infections and congenital absence of vas deferens.
- pneumonia due to a non-lactose-fermenting, gram-negative rod (Pseudomonas, Burkholderia)
lymphocytic infiltration of the pancreatic islet cells
type I DM
- destruction of insulin-producing pancreatic cells
nodular lymphoid hyperplasia of the intestine
seen in common variable immunodeficiency syndrome (low immunoglobulin and B lymphocyte levels that predispose to recurrent sinopulmonary and GI infections)
CMV esophagitis
linear, shallow ulcerations in the lower esophagus
- occurs in immunocompromised patients (HIV, transplant, immunosuppressive drugs).
CMV can be transmitted to transplant recipients from the donor organ, or infection from chronic immunosuppression.
presentation:
- odynophagia (pain with swallowing)
- dysphagia (difficulty swallowing)
- fever (or burning chest pain)
endoscopy shoes linear and shallow ulcerations in the lower esophagus
tissue biopsy shows enlarged cells with basophilic or eosinophilic intranuclear inclusion bodies
metaplastic columnar epithelium seen in:
Barrett esophagus which is due to prolonged GERD. histologically typically shows tongue-like projections of columnar epithelium with goblet cells (intestinal metaplasia) extending from the distal esophagus to the GE junction.
cryptococcus neoformans
Yeast with a polysaccharide capsule.
Crohns disease patient with kidney stones. cause?
reduced intestinal calcium oxalate formation.
- terminal ileum involvement is usually common. when the terminal ileum is inflamed, bile acids are lost in the feces leading to impaired fat absorption
- In crohns disease, calcium forms soap complexes with the excess fat in the intestinal lumen and is unavailable for complexing with oxalate. –> free oxalate absorption is increased and filtered into the urine, promoting the formation of oxalate kidney stones (enteric oxaluria)
Hepatic abscess
possible route: staph aureus by hematogenous route
presence of fluid filled cavity in the liver, with fevers, RUQ pain –> hepatic abcess.
causes
developing countries: parasitic infection (Entamoeba histolytica, echinococcus)
In the US: bacterial infections
pyogenic bacteria can gain access to the liver through the following routes:
- biliary tract infection (ascending cholangitis)
- portal vein pyemia (bowel or peritoneal sources)
- hepatic artery (systemic hematogenous seeding) - Staph aureus infection
- direct invasion from adjacent sources (peritonitis, cholecystitis)
- penetrating trauma or injury
ascending cholangitis causes
enteric gram-negative bacilli (E.coli, Klebsiella) and enterococci.
Lymphatic drainage of the rectum proximal to the anal dentate line occurs via the inferior mesenteric and internal iliac lymph nodes.
areas distal to the dentate line drain primarily into the inguinal nodes
stronglyloid sterocoralis IgG is positive. detection of active infection?
rhabditiform larvae in the stool
carcinoid syndrome
wheezing, diarrhea, facial flushing in association with ileal tumor with hepatic metastasis.
- carcinoid tumors (ileal tumors) secrete a number of active substances including serotonin
- common manifestations of carcinoid syndrome include flushing, asthma-like symptoms (wheezing, dyspnea), diarrhea, and syncope (due to low BP)
- long-standing Carcinoid syndrome can cause right-sided valvular heart disease
definitive therapy: surgical excision.
medical therapy with octreotide can be used to control symptoms.
octreotide is a synthetic analog of somatostatin that can be used to control symptoms. It acts on somatostatin receptors and inhibits the secretion of many hormones.
- octreotide is also used to inhibit secretory diarrhea in VIPomas (pancreatic endocrine tumors)
structures directly occluded as a result of occlusion of hepatoduodenal ligament
hepatic artery, portal vein, common bile duct (portal triad)
3-day-old newborn with bilious emesis, blind-ending proximal jejunum, a length of absent bowel and mesentery, and terminal ileum spiraled around an ileocolic vessel. diagnosis?
intestinal atresia below duodenum
Cause: Vascular occlusion
enteropeptidase in the duodenal brush border activates what substance?
trypsin
enzyme causing brown pigment stones?
beta-glucuronidase
