GI USMLE contd 7-18

Question 1

This patient has poor oral hygiene, sinus tracts on the buccal mucosa that express a yellow exudate, and a nodular mandibular lesion, which suggests he has an?

Answer 1

actinomycosis infection of the buccal tissue. This condition is characterized by multiple oral abscesses and draining sinuses and is caused by the gram-positive organism Actinomyces israelii

Question 2

Actinomyces israelii is a ?

Answer 2

gram-positive, anaerobic, and non–acid-fast bacteria that forms long, branching filaments resembling fungi. Actinomycosis is characterized by the formation of multiple abscesses and draining sinuses, most commonly of the buccal mucosa secondary to poor dentition. Yellow sulfur granules on microscopy and draining sinus tracts are characteristic of this organism.

Question 3

This patient, who presents with watery stools with flecks of mucus (often called “rice-water” stool), electrolyte abnormalities, and signs that suggest dehydration, most likely has?

Answer 3

cholera, caused by the bacterium Vibrio cholerae. His recent stay in Bangladesh, where cholera is endemic, supports this diagnosis.

Question 4

. Cholera toxin enters the cell and constitutively activates ?

2.Vibrio cholerae produces an exotoxin that permanently activates Gs protein, resulting in an?

Answer 4

Gs protein through ADP ribosylation. This illness is not usually accompanied by abdominal pain or fever
2, excess of cAMP, which leads to a profuse watery non-bloody diarrhea

Question 5

This gravid patient presents with symptoms of constipation, extreme pain with defecation, and a sensitive perianal lump. These are all classic signs of ?

Answer 5

external hemorrhoids.Hemorrhoids are a normal part of the anal canal, where engorgement and straining from constipation results in prolapse of the tissue into the anal canal (forming a palpable lump). External hemorrhoids originate below the pectinate line, whereas internal hemorrhoids originate above the pectinate

Question 6

External hemorrhoids originate below the pectinate line, receive somatic innervation and can therefore be extremely painful. This extreme pain, which can cause secondary constipation, helps distinguish external from relatively painless internal hemorrhoids. Venous drainage of external hemorrhoidal tissue is via the ?

Answer 6

inferior rectal vein to the inferior vena cava.

Question 7

In a child with a high fever but no clear source of infection (as suggested by the benign physical exam, imaging, and lumbar puncture results), one must check for occult bacteremia via a blood culture. This child, who presents with fever and delirium, has?

Answer 7

bacteremia as evidenced by blood cultures positive for S pneumoniae. S pneumoniae is a gram-positive, α-hemolytic diplococcus that may cause bacteremia, pneumonia, meningitis, and cellulitis.

Question 8

Kupffer cells are specialized ?

Answer 8

hepatic macrophages that are crucial in clearing pathogens from the bloodstream.

Question 9

Free fatty acids are nonpolar hydrophobic molecules and are thus able to cross the cell membrane by?

Answer 9

simple diffusion. The phospholipid bilayer of cell membranes prevents polar solutes (eg, amino acids, nucleic acids, carbohydrates, proteins, and ions) from diffusing across the membrane; yet, these cell membranes allow the simple diffusion of hydrophobic molecules.

Question 10

Lactose and Fructose transport across the apical membrane requires?

Answer 10

facilitated diffusion via sodium cotransporters

Question 11

The patient presents with a history of Crohn disease and symptoms of bloody diarrhea, vomiting, and weight loss. His right upper and lower quadrants show tenderness on palpation, and hyperactive bowel sounds are auscultated throughout the abdomen. Together, these findings suggest an ?

Answer 11

exacerbation of inflammatory bowel disease.

Question 12

Infliximab binds to and neutralizes ?

Answer 12

the inflammatory cytokine, TNF-α, found in high concentrations in the stool of patients with Crohn disease.

Question 13

This patient is one of a group of individuals with diarrhea and abdominal pain following a pork barbecue. These symptoms, in combination with diffuse myalgias and ocular manifestations, including conjunctival hemorrhages and periorbital edema, should raise suspicion of food-borne illness. The clinical picture is characteristic of infection caused by ?

Answer 13

Trichinella spiralis, a nematode found in undercooked pork and wild game and the cause of trichinellosis (also called trichinosis).

Question 14

This patient, who presents with pharyngitis with a gray-white pseudomembrane, cervical adenopathy, and low-grade fever, shows the classic signs of ?

Answer 14

diphtheria. Between 1 and 2 weeks after onset of symptoms, cardiac involvement may be noticed, as in this patient, indicating potentially life-threatening progression of disease with development of myocarditis and cardiomyopathy.

Question 15

Diphtheria is caused by Corynebacterium diphtheriae via an exotoxin that is encoded by ?

Answer 15

the B prophage. The exotoxin inhibits protein synthesis by adenosine diphosphate ribosylation of elongation factor 2, leading to pseudomembrane formation in the pharynx, pharyngitis, lymphadenopathy, fever, and, if left untreated, myocarditis and cardiomyopathy

Question 16

This patient presents with dizziness and feeling light-headed—common complaints during pregnancy. Potential causes range from the benign physiologic changes of pregnancy to much more serious pathology such as preeclampsia. This woman’s dizziness is only present when lying on her back, and her blood pressure is within normal limits, so her symptoms are likely to be caused by ?

Answer 16

compression of the vena cava. Compression of the inferior vena cava (IVC) by a large mass, such as a tumor or a gravid uterus, can result in decreased venous return from the lower extremities. This can cause transient hypotension and contribute to peripheral edema.

Question 17

The inferior vena cava may be compressed in conditions that greatly increase intra-abdominal pressure, such as a gravid uterus in pregnancy. The IVC traverses the diaphragm at T8, directly passing through ?

Answer 17

the central tendon of the diaphragm.

Question 18

Construction workers, especially those exposed to industrial paints (found on bridges, for example), are at risk for?

Answer 18

lead toxicity. This patient’s signs and symptoms suggest lead toxicity, which may also manifest with wrist and foot drop, hypertension, nausea, seizures, hearing loss.

Question 19

.Dimercaprol and ethylenediaminetetraacetic acid (EDTA) are?

Answer 19

first-line treatments for lead poisoning in adults. Dimercaprol is a chelating agent that binds its thiol groups to lead, hastening its urinary excretion. Lead disturbs heme formation by inhibiting δ-aminolevulinic acid dehydratase and ferrochelatase, which in turn leads to decreased incorporation of iron into heme

Question 20

Deferoxamine for ?

Answer 20

iron overdose

Question 21

N-Acetylcysteine for ?

Answer 21

acetaminophen overdose

Question 22

Naloxone for?

Answer 22

opioid overdose

Question 23

Protamine sulfate for?

Answer 23

heparin overdose

Question 24

A 30-year-old woman presents to her primary care physician with swelling in her right cheek and excessive salivation with drooling. The swollen area is nodular, firm, painless. As the rate of salivation increases, less sodium is reabsorbed and less potassium is secreted. In this condition, salivary sodium will be?

Answer 24

increased while potassium will be decreased relative to normal salivary electrolyte levels.

Question 25

As in most muscle, contraction of gastrointestinal (GI) smooth muscle cells can be initiated by electrical activity and results in excitation-contraction coupling. However, the slow, rhythmic electrical changes noted in GI smooth muscle, referred to as slow waves, are generated by a unique mechanism involving the interstitial cells of Cajal (ICCs). Slow waves are precisely timed,?

Answer 25

rhythmic depolarizations and repolarizations of the muscularis propria of the stomach and intestines, independent of the presence or absence of stimulus.

They move in an oral-to-anal direction and occur at a frequency specific to each organ, with the stomach having the lowest frequency (3 cycles per minute) and the duodenum of the small intestine having the highest frequency (12 cycles per minute). They represent the basal electric rhythm of gastric and intestinal motility, although they don’t always result in mechanical activation.

Question 26

This patient has an asymptomatic increase in direct bilirubin levels, while her other liver test results are normal. An isolated direct hyperbilirubinemia with no other symptoms may occur in a patient with?

Answer 26

Dubin-Johnson syndrome, an autosomal recessive disorder that results in defective excretion of conjugated bilirubin from the liver. In this syndrome, the liver takes on a grossly black appearance caused by pigmented granules that accumulate within hepatocytes.

Question 27

The patient presents with a history of recent ceftriaxone and clindamycin use, hospitalization, and symptoms of diarrhea. Additionally, the patient has a significant fever (≥103° F), substantial leukocytosis (≥30,000), and abdominal distention. This clinical picture is consistent with?

Answer 27

pseudomembranous colitis due to Clostridium difficile (C. difficile) infection.

Question 28

C. difficile produces two cytotoxins (toxin A and the more important toxin B). While both toxins have a wide range of activities, toxin B is the more potent cytotoxin, causing ?

Answer 28

apoptosis in a wide variety of cell types.

Question 29

This patient presents with flu-like symptoms, including headache, nausea and vomiting with blood, joint pain, and Faget sign, fever coinciding with bradycardia. His laboratory results show elevated liver enzymes and leukopenia. In light of the patient’s recent travels to a region where mosquito-borne illness is not uncommon, his symptoms are highly suggestive of ?(Faget’s sign is classical for a diagnosis of yellow fever).

Answer 29

yellow fever.

Yellow fever is caused by a flavivirus, a single-stranded RNA virus transmitted via a mosquito vector. Symptoms manifest following a three to six day incubation period.

Question 30

A 27-year-old man presents to the doctor’s office with a history of chronic low-grade diarrhea of several years’ duration. He reports that he sees no blood or pus in the diarrhea, but that recently he has developed copious gas and bloating when he ingests dairy products. Stool analysis for ova and parasites reveals?

Answer 30

The organism is Giardia lamblia. Giardia can cause a long-term, smoldering infection of the small intestine resulting in few or no symptoms. The image shows the trophozoite form of the organism, which proliferates in the intestine

Question 31

This patient is presenting with bilious vomiting and a diffusely tender abdomen, a clinical picture that is most suggestive of ?

Answer 31

a small bowel obstruction. Dilated loops of small intestine on x-ray of the abdomen (like that shown in the image provided with the vignette) and a clinical history of anorexia, vomiting, and abdominal pain are usually sufficient to make the diagnosis. In the United States, the leading cause of small bowel obstructions is adhesion formation, which obstructs the lumen of the small bowel. These adhesions are formed during the healing process, secondary to abdominal surgery. Other conditions that predispose patients to small bowel obstructions are hernias and intraluminal cancers of the small intestine.

Question 32

centrolobular accumulation of copper in hepatocytes and a band of fibrous tissue with inflammatory cells and copper-laden macrophages. This is seen in ?

Answer 32

Wilson disease, which is caused by copper accumulation in the liver, brain, and cornea secondary to an autosomal recessive defect in copper transport. Early manifestations include corneal copper deposits, known as Kayser-Fleischer rings, and asymptomatic elevations in liver enzyme levels. It may also present with a type 2 renal tubular acidosis (hypokalemia and metabolic acidosis)

Penicillamine is a potent copper chelator given in high doses after the diagnosis of Wilson disease to deplete accumulated body stores of copper.

Question 33

an elderly patient with acute-onset lower left quadrant pain and a history of constipation or painless rectal bleeding. ?

Answer 33

Diverticulitis should be suspected in ………………Once the symptoms are resolved, the patient should undergo colonoscopy to rule out malignancy, especially if there is evidence of iron deficiency anemia.
DiverticulitisQuadrant (anatomy)ConstipationPainlessResolvedColonoscopyMalignancyRectal bleedingIron deficiency anemia

Question 34

This young child is experiencing sudden-onset intermittent abdominal pain, dark red stool, and vomiting; these symptoms indicate intestinal obstruction, likely secondary to intussusception. One possible anatomical cause for this is ?

Answer 34

Meckel diverticulum.

Meckel diverticulum is a congenital outpouching of the small intestine that results from the failed closure of the vitelline (omphalomesenteric) duct.

Question 35

The patient presents with abdominal pain and swelling, and reports regular travel to Brazil where he bathed in the Amazon river.?

Answer 35

Schistosomiasis is a parasitic blood fluke disease with hepatic involvement. Schistosoma mansoni (see image) cercariae are commonly found in fresh waters in tropical and subtropical areas of sub-Saharan Africa, the Middle East, South America, and the Caribbean.
Schistosoma mansoni, a parasite that lives in freshwater in many parts of the world, can cause portal hypertension by invading the venous vasculature of the liver. Treatment is a single oral dose of praziquantel.