Uworld16 Flashcards
Where does antidiuretic hormone act in the nephron?
ADH acts primarily on the collecting ducts, increasing their permeability to water.
In the absence of ADH, the tubular fluid is most concentrated at the junction between the descending and ascending limbs of the loop of Henle and most dilute in the collecting ducts
What is thyroid dysgenesis (ie, hypoplasia, aplasia, ectopy)?
the most common cause of primary congenital hypothyroidism.
In this condition, TSH is elevated and thyroxine (T4) is low
How does cholinesterase inhibitors (eg, donepezil, galantamine) work in Alzheimer disease?
Cholinesterase inhibitors (eg donepezil, galantamine) may provide modest symptomatic improvement of cognitive symptoms and temporarily improve functioning in patients with Alzheimer disease. However, these meds do not alter the inevitable disease progression.
What is concentric left ventricular hypertrophy?
Involves thickening of the ventricular walls and reduction in the ventricular cavity size.
It occurs via the addition of myocardial contractile fibers in parallel in response to chronic pressure overlead.
Aortic stenosis and prolonged systemic hypertension are common causes of concentric left ventricular hypertrophy
What is a cohort study?
A cohort study is used to compare incidence of disease between exposed and nonexposed individuals. A common measure of association in cohort studies is the relative risk.
Piperacillin-tazobactam is effective against?
a combination of extended-spectrum penicillin with B-lactamase inhibitor.
It is effective against most gram-negative enteric rods (including Pseudomonas aeruginosa) and against Bacteroides fragilis
What forms the fibrous cap of a mature atheroma?
Medial smooth muscle cells are responsible for synthesizing the extracellular matrix proteins (eg, collagen, proteoglycans) that form the fibrous cap of a mature atheroma.
Progressive atheroma enlargement increases the likelihood of plaque rupture with resulting luminal thrombosis.
What is minimal change disease?
the most common cause of nephrotic syndrome in kids.
It is often idiopathic but may be triggered by drugs, immunization or malignancy.
Light microscopy shows normal glomeruli, with no immunoglobin or complement deposits on immunofluorescent staining.
However, electron microscopy shows diffuse podocyte foot process effacement and fusion.
what is a psoas abscess
The psoas muscle originates from the anterior surface of the transverse processes and lateral surface on the vertebral bodies and functions primarily as a hip flexor.
Psoas abscess may form due to direct spread of infection from adjacent structure (eg, vertebral bodies, appendix, hip joint) or from hematogenous seeding from a distant site
Atopic dermatitis increases the risk for allergic rhinitis, asthma, and food allergies, likely because?
of an immune response that favors IgE production.
In addition, skin barrier dysfunction facilitates food allergen penetration and sensitization, increasing the risk for food allergies.
What are the 5 major causes of hypoxemia (low arterial pressure of oxygen (PaO2)?
- alverolar hypoventilation
- low partial pressure of inspired oxygen
- ventilation-perfusion mismatch
- diffusion impairmentnt
- right to left shunting
The A-a gradient is normal with alveolar hypoventilation and low partial pressure of inspired oxygen, which heps distinguish these causes from other causes of hypoxemia.
What is seen in autologous hematopoietic stem cell transplantation?
Autologous hematopoietic stem cell transplantation reinfuses host cells from the patient’s peripheral blood or banked cord blood to reconstitute the bone marrow.
Because the reinfused cells are genetically identical to the host’s, there is no risk of graft rejection or graft versus host diease.
Although there is also no risk for transferring a new bloodborne pathogen, chronic or latent infections (eg, Epstein Barr virus, cytomegalovirus, varicella-zoster virus) may worsen due to the transient immunosuppression induced by myeloablative chemotherapy
Impaired intestinal blood flow (eg, acute mesenteric ischemia) creates an anaerobic environment that leads to?
an elevate NADH/NAD+ ratio.
This decreases activity of pyruvate dehydrogenase (converts pyruvate –> acetyl coA) while stimulating lactate dehydrogenase (converts pyruvate –> lactate), shunting the metabolic fate of pyruvate toward lactate production,
Patients with significant tissue ischemia are therefore at risk of lactic acidosis.
What is the primary goal of medical therapy for acute aortic dissection?
to reduce aortic wall shear stress by minimizing the change in aortic blood pressure per time.
Esmolol, a selective beta-1 blocker, decreases left ventricular contraction velocity and heart rate to reduce aortic blood pressure per time.
What is borderline personality disorder?
persistant pattern of unstable relationships, mood lability, and impulsivity.
Individuals with this disorder may exhibit suicidal ideation or behavior in the context of an interpersonal crisis in which they feel rejected or abandoned.
What is Lambert-Eaton myasthentic syndrome?
characterized by antibodies against presynaptic voltage gated calcium. Patients develop progressive proximal muscle weakness with reduced/absent flexes that predominantly involves the lower extremities.
The syndrome is often associated with malignancy, particularly small cell lung cancer.
Digoxin is cleared by what organ?
Digoxin is a cardiac glycoside that is predominantly cleared by the kidneys.
Elderly patients typically exhibit age-related renal insufficiency, even in the presence of normal creatinine levels.
The dose of digoxin must be reduced in these patients to prevent toxicity.
What is capitation?
an arrangement in which a payor pays a fixed, predetermined fee to provide all the services required by a patient.
Payors may negotiate a capitated contract with an insurance company that then pays the providers, or a large medical group may negotiate directly with the payor
Lead poisoning can cause what?
neurologic, gastrointestinal, renal, and hematologic complications.
Although symptoms can be vague, lead poisoning should be suspected if these symptoms arise while residing in a home built before 1978.
Diagnosis is made by measuring the patient’s blood lead level.
Ascites in cirrhosis develops from hemodynamic changes related to?
portal hypertension.
Splanchnic vasodilation decreases the systemic vascular resistance, which causes activation of the renin-angiotensin-aldosterone system and promotes vasoconstriction and sodium and water retention.
Spironolactone, an aldosterone antagonist, is used to induce natriuresis and resolve ascites without blocking the critical vasoconstrictive effects of angiotensin.
What is mucormycosis?
an opportunistic infection caused by Rhizopus, Mucor, and Absidia species.
The classic clinical picture is paranasal sinus involvement in a diabetic or immunosuppressed patient.
The fungi form broad nonseptate hyphae that branch at right angles
Dizygotic twins occur due to?
fertilization of 2 oocytes by 2 different sperm, can be different sexes, and almost always have 2 chorions and 2 amnions (eg, dichorionic/diamniotic)
Monozygotic twins arise from the fertilization of?
a single oocytes, are the same sex, and can be dichorionic/diamniotic (days 0-4), monochorionic/diamniotic (days 4-8), monochorionic/monoamniotic (days 8-12), or monochorionic/monoamniotic conjoined twins (>13 days)
What is inclusion cell disease?
a lysosomal storage disorder in which a defect in protein targeting prevents the phosphorylation of mannose residues required to tag acid hydrolases for transport to lysosomes.
Without these lysosomal proteins, cellular debris cannot be degraded and therefore accumulates within lysosomes, forming inclusion bodies characteristic of the disease.
What is positive predictive value?
the probability that an individual has a disease given a positive test.
It is calculated as: true positives / (true positive + false positives)
What is Li-Fraumeni syndrome?
caused by an autosomal dominant mutation in the tumor suppressor gene TP53.
Leukemia, sarcomas, and tumors of the breast, brain, and adrenal cortex are most common.
What is the process of DNA synthesis?
DNA synthesis occurs is the 5’-3’ direction only.
During DNA replication, one daughter strand is synthesized continuously toward the replication fork (leading strand), whereas the other daughter strand is synthesized discontinuously away from the replication fork (lagging strand).
The lagging strand is formed from short stretches of newly synthesized DNA separated by RNA primers (Okazaki fragments)
What is ovarian vein thrombosis (infected ovarian vein thrombus)?
is a rare complication associated with the postpartum period and is typically right sided.
Because ovarian venous drainage is asymmetric, a thrombus in the right ovarian vein can extend into the inferior vena cava. In contrast, a left ovarian vein thrombosis would extend first to the left renal vein.
Shiga toxin-producing Escherichia coli O157:H7 elaborates Shiga toxin, which inactivates 60S ribosomal subunits in colonic mucosal cells, leading to the inhibition of?
protein synthesis and apoptosis; clinical manifestations include bloody diarrhea.
Hematogenous spread of Shiga toxin to renal endothelial cells can also lead to hemolytic uremic syndrome
What is idiopathic intracranial hypertension (pseudotumor cerebri)?
presents in young obese women with daily headache (which worsens during the Valsalva maneuver), bilaterally symmetric papilledema, and transient visual disturbances.
Increased intracranial pressure compresses the optic nerves, resulting in impaired axoplasmic flow and optic disc edema.
Side effects of dopamine receptor blockers (eg, metoclopramide, prochlorperazine)
Dopamine receptor blockers (eg, metoclopramide, prochlorperazine) act as antiemetics and pain relievers for severe migraine headache associated with nausea and vomiting.
However, dopamine blockade can also result in excess cholinergic activity (eg, acute dystonic reactions); diphenhydramine can be co-administered with dopamine receptor blockers to prevent these reactions due to its anticholinergic activity.
What is the most common risk factor for calcium (calcium oxalate and calcium phosphate) kidney stones in adults?
Hypercalciuria; contributing factors may include increased gastrointestinal absorption, increased mobilization of calcium from bone, or decreased renal tubular calcium reabsorption.
However, most patients remain normocalcemic due to regulation of plasma calcium levels by vitamin D and parathyroid hormone
What is anorexia nervosa?
low body weight (BMI<18.5), fear of becoming fat, and distorted body image.
Unlike other patterns of restrictive eating, (eg, bulimia nervosa), patients with anorexia nervosa experience complications of progressive clinical starvation, such as bradycardia, osteoporosis, and amenorrhea
What is TSH resistance?
due to a mutation in the TSH receptor gene presents with congenital hypothyroidism, which is characterized by increased TSH and low thyroxine.
The thyroid gland is normal in size and location.
How can the anterior cruciate ligament (ACL) can be damaged?
by sudden changes in direction or awkward landings (eg, excessive internal rotation or valgus stress) during sports activity.
ACL tears are typically associated with rapid-onset hemarthrosis.
PE shows anterior laxity of the tibia relative to the femur (eg, Lachman test, anterior drawer test)
What is epiglottitis?
causes rapidly progressive airway obstruction and classically presents with fever, dysphagia, drooling, stridor, and tripod positioning.
Individuals with incomplete immunization against Haemophilis influenzae type b are at greatest risk
A painless, solid scrotal mass should be considered?
testicular cancer until proven otherwise.
Examination generally reveals a solid, firm, or fixed nodule in the tunica albuginea that is ovoid in shape and painless to palpation.
Testicular tumors do not transilluminate
What is Wolff-Parkinson-white pattern?
characterized by a shortened PR interval, slurred initial upstroke of the QRS complex (delta wave), and widening of the QRS complex.
It is caused by an accessory pathway that bypasses the atrioventricular node, leading to ventricular preexcitation.
Some patients develop paroxysmal tachyarrhythmias (eg, atrioventricular reentrant tachycardia) due to reentry of electrical impulses through the accessory conduction pathway (ie, WPW syndrome)
Acid base for severe vomitting
hypokalemic, hypochloremic metabolic alkalosis.
The metabolic alkalosis is initiated by loss of gastric H+ from the body, worsened by hypovolemia-induced activation of the renin-angiotensin-aldosterone system, and perpetuated by profround gastric and renal losses of Cl- that lead to hypochloremia and impaired renal HCO3- excretion.
Hypokalemia primarily results from aldosterone-mediated renal K+ losses
What is Vernet syndrome?
Lesions of the jugular foramen can result in jugular foramen (Vernet) syndrome, which is characterized by the dysfunction of cranial nerves IX, X, and XI.
Symptoms include dysphagia, hoarseness, loss of gag reflex on the ipsilateral side, and deviation of the uvula toward the normal side.
What is mesothelioma?
a neoplasm arising from mesothelial cells and is strongly associated with asbestos exposure.
In early mesothelioma, multiple nodules form on the parietal pleura and gradually encase the lung parenchyma.
Immunohistochemistry is important for diagnosis; nearly all mesotheliomas strain positive for cytokeratins and many also stain positive for calretinin
