UWorld 4/15

A prospective cohort study was conducted to assess the role of daily alcohol consumption in the occurrence of breast carcinoma. The investigators reported a 5-year relative risk of 1.4 for people who consume alcohol daily compared to those who do not. The 95% confidence interval was 1.02-1.85. Which of the following p-values is most consistent with the results described above? A. 0.03 (%) B. 0.06 (%) C. 0.09 (%) D. 0.11 (%) E. 0.20 (%)

A. 0.03 (%)

A 58-year-old man is hospitalized due to sudden onset of chest pain. Blood pressure is 160/110 mm Hg and pulse is 90/min. BMI is 26.9 kg/m2. A baseline ECG shows nonspecific ST-segment and T-wave abnormalities, and serial troponin measurements are normal. The patient's fasting plasma glucose level is 160 mg/dL, although he has not been diagnosed previously with diabetes mellitus. Serum triglyceride level is elevated, and the HDL level is low. Which of the following additional findings would be most suggestive of increased insulin resistance in this patient? A. Decreased hepatic glucose production (%) B. Elevated LDL level (%) C. High urine ketone concentration (%) D. Increased glycogen stores in skeletal muscles (%) E. Increased waist circumference (%)

E. Increased waist circumference (%) This patient has hypertension and likely type 2 diabetes mellitus. The primary defects in the pathophysiology of type 2 diabetes include defective insulin secretion from pancreatic beta cells and insulin resistance in peripheral tissues. Insulin resistance is caused by a number of genetic (eg, insulin receptor and postreceptor mutations) and environmental factors (eg, lack of physical activity, obesity). An adipose body habitus is commonly associated with insulin resistance and type 2 diabetes. In particular, excess visceral fat (surrounding internal organs) correlates much more strongly with insulin resistance than does subcutaneous fat. Measurement of waist circumference or waist-to-hip ratio is an effective indirect assessment of visceral fat, especially in patients who are overweight (BMI 25-29.9 kg/m2) or mildly obese (BMI 30-34.9 kg/m2). A waist circumference >102 cm (40 in) in men and >88 cm (35 in) in women is associated with a higher risk of insulin resistance. The association of insulin resistance, increased visceral adiposity (ie, increased waist circumference), hypertension, and serum lipid abnormalities (high triglyceride levels, low HDL levels) is known as metabolic syndrome (sometimes called syndrome X). Patients with metabolic syndrome have increased rates of cardiovascular events and warrant careful risk factor management (Choice C) High urinary excretion of ketones suggests absolute insulin deficiency, as seen in type 1 diabetes, rather than insulin resistance. Patients with type 2 diabetes and insulin resistance typically have high circulating insulin levels that are more than adequate to suppress ketone formation.

In an animal experiment the levels of various endogenous compounds are measured in the spinal fluid after application of noxious stimuli. One of the compounds that increase as a result of the experiment is a pentapeptide with a strong affinity to delta- and mu-receptors. Which of the following substances is most likely to have a common molecular origin with the pentapeptide described above? A. Prolactin (%) B. TSH (%) C. ACTH (%) D. Growth hormone (%) E. Vasopressin (%) F. Somatomedin C (%)

C. ACTH (29%) Beta-endorphin is one endogenous opioid peptide that is derived from proopiomelanocortin (POMC). POMC is a polypeptide precursor that goes through enzymatic cleavage and modification to produce not only beta-endorphins, but also ACTH and MSH. The fact that beta-endorphin and ACTH are derived from the same precursor suggests that there may be a close physiological relationship between the stress axis and the opioid system

A research group conducted a study to compare the levels of creatine kinase-MB (CK-MB) between type 2 diabetes mellitus (T2DM) patients given statin therapy. Participants were divided into 4 groups based on treatment. Groups I, II, and III consisted of T2DM patients who had been given statin therapy (atorvastatin, simvastatin, rosuvastatin, respectively) for at least 6 months. Group IV consisted of T2DM patients who had not been given statin therapy. Which of the following statistical tests is most appropriate to compare the CK-MB levels between Groups I, II, III, and IV in this study? A. Analysis of variance (%) B. Chi-square test (%) C. Independent t-test (%) D. Paired t-test (%) E. Correlation analysis (%)

A. Analysis of variance (%) Variables are broadly classified as qualitative (ie, categorical) or quantitative (eg, continuous) based on their scale of measurement. Qualitative variables (eg, type of treatment, blood type) represent categories or groups, whereas quantitative variables (eg, temperature, glucose levels) represent numerical values, with quantitative variables (eg, temperature) sometimes transformed into qualitative variables (eg, "no fever" for <38 C [100 F]; "fever" for ≥38 C [100 F ]). The scale of measurement of the dependent (eg, outcome) and independent (eg, exposures, risk factors) variables in a study determines the correct statistical test for any given situation. The analysis of variance (ANOVA) test compares the means of ≥3 groups. It requires a categorical independent variable (ie, exposure) that is used to divide the study pool into ≥3 groups and a quantitative dependent variable (ie, outcome) for which an average (eg, mean) can be calculated. In this study: The quantitative dependent variable was the levels of creatine kinase-MB (CK-MB). The categorical independent variable was type of statin therapy that was used to categorize 4 different groups of patients with type 2 diabetes mellitus (T2DM): Group I (atorvastatin), Group II (simvastatin), Group III (rosuvastatin), and Group IV (no statin). An ANOVA test can determine whether there is a statistically significant difference in mean levels of CK-MB among T2DM patients given different statin therapies. A large, statistically significant difference in mean CK-MB levels among groups indicates that different statin therapies are associated with significant changes in CK-MB levels (ie, the null hypothesis is rejected).

A 26-year-old man is being evaluated for recurrent boils and skin abscesses. Anterior nares swab culture is performed to determine colonization by the culprit bacteria, which yields gram-positive cocci in clusters. The bacteria are able to grow in a media containing oxacillin. PCR testing reveals the pathogen has acquired the mecA gene. These bacteria are most likely to be resistant to which of the following antibiotics? A. Cefazolin (%) B. Clindamycin (%) C. Doxycycline (%) D. Trimethoprim-sulfamethoxazole (%) E. Vancomycin (%)

A. Cefazolin (%) This patient with recurrent boils and skin abscesses is likely colonized with Staphylococcus aureus, a gram-positive cocci that grows in clusters. Methicillin-resistant strains are able to grow in the presence of oxacillin due to the acquisition of a mobile genetic element that contains the mecA gene, which encodes for penicillin-binding protein (PBP) 2a. PBPs catalyze peptidoglycan cross-linking during cell wall synthesis; they are the target of beta-lactam medications, which bind to and irreversibly destroy the enzyme. Unlike other PBPs, PBP 2a has a low affinity for beta-lactams and continues to cross-link peptidoglycan in the presence of oxacillin, methicillin, cephalosporins (eg, cefazolin), and other beta-lactam medications

A 65-year-old man reports multiple episodes of lightheadedness while buttoning a tight shirt collar. During 2 episodes, he passed out briefly but sustained no injuries. His blood pressure was 70/40 mm Hg and pulse was 45/min during one of the episodes. Past medical history is significant for hypertension and diet-controlled diabetes mellitus. The patient is a lifetime nonsmoker and drinks alcohol on social occasions. On physical examination, his blood pressure is 125/72 mm Hg and pulse is 76/min without orthostatic changes. Stimulation of afferent sensory fibers in which of the following nerves is most likely responsible for this patient's symptoms? A. Accessory (%) B. Glossopharyngeal (%) C. Hypoglossal (%) D. Trigeminal (%) E. Vagus (%)

B. Glossopharyngeal (%) The carotid sinus reflex has an afferent limb that arises from the baroreceptors in the carotid sinus and travels to the medullary centers via the Hering nerve, a branch of the glossopharyngeal nerve (CN IX). The efferent limb of the carotid sinus carries parasympathetic impulses via the vagus nerve (CN X). Carotid sinus pressure or massage stimulates the baroreceptors and increases the firing rate from the carotid sinus, leading to an increase in parasympathetic output and withdrawal of sympathetic output to the heart and peripheral vasculature. The result is decreased blood pressure (via peripheral vasodilation) and decreased cardiac output (decreased contractility/stroke volume and heart rate). In sensitive individuals, this response can cause severe bradycardia, hypotension, and sometimes syncope.

A 62-year-old woman is brought to the emergency department due to progressive weakness and dyspnea. The patient is visiting her niece, who says the patient forgot to bring her regular medications and has not been taking them for the past week. The patient began feeling weak and fatigued 3 days ago and has had shortness of breath since yesterday. Temperature is 37 C (98.6 F), blood pressure is 122/88 mm Hg, pulse is 90/min, and respirations are 24/min and shallow. On physical examination, the patient appears dyspneic with drooping at the eyelids and corners of the mouth. Her speech has a nasal quality. Arterial blood gas obtained on room air shows pH 7.32; PaCO2 is 52 mm Hg, PaO2 is 72 mm Hg, and HCO3 is 26 mEq/L. Bedside spirometry demonstrates decreased forced vital capacity. A pathologic process involving which of the following structures is the most likely cause of this patient's shortness of breath? A. Brain stem respiratory center (%) B. Muscles of respiration (%) C. Pulmonary arteries (%) D. Terminal airways and alveoli (%) E. Upper larger airways (%)

B. Muscles of respiration (%) This patient has hypercapnic and hypoxic respiratory failure (low pH, high CO2, low O2) indicating global hypoventilation. In association with the ptosis, bulbar weakness, and low forced vital capacity, this presentation suggests myasthenic crisis (severe weakness and respiratory depression due to an exacerbation of myasthenia gravis [MG]). MG is characterized by autoantibodies against nicotinic acetylcholine receptors on the postsynaptic membrane of the neuromuscular junction, resulting in receptor degradation. This reduces the sensitivity of the postsynaptic membrane to acetylcholine stimulation, leading to reduced muscular response despite normal acetylcholine release. Muscle weakness worsens with repetition as acetylcholine stores within the presynaptic nerve terminal become progressively depleted. Patients with MG typically have extraocular (eg, ptosis, diplopia), bulbar (eg, dysphonia, difficulty chewing), and facial (eg, myasthenic snarl) weakness. In addition, neck and proximal muscle weakness may occur, and in severe cases the respiratory muscles may be affected, leading to respiratory failure (as in this patient). Acetylcholinesterase inhibitors (eg, pyridostigmine, neostigmine) are used for symptomatic treatment, and withdrawal can trigger a myasthenic crisis.

A 55-year-old man comes to the emergency department due to sudden-onset dyspnea. Medical history is significant for hypertension, hyperlipidemia, type 2 diabetes mellitus, and chronic kidney disease. The patient takes multiple medications and has no drug allergies. He works for an international bank and returned from a business trip in Australia a day ago. Blood pressure is 110/70 mm Hg and pulse is 110/min. Physical examination shows a moderately overweight man with tachypnea. The lungs are clear on auscultation. ECG shows sinus tachycardia. Ventilation/perfusion scanning is ordered. Which of the following findings would help confirm the suspected diagnosis in this patient? A. Absence of ventilation and perfusion abnormalities (%) B. An area showing both ventilation and perfusion defects (%) C. A perfusion defect without an associated ventilation defect (%) D. A ventilation defect without an associated perfusion defect (%) E. Several small areas of matched perfusion and ventilation defects (%)

C. A perfusion defect without an associated ventilation defect (%) Pulmonary embolism (PE) should be suspected in this patient with recent extended travel (prolonged immobilization) who now has acute-onset dyspnea and tachypnea, normal lung examination, and sinus tachycardia on ECG. In most patients, CT angiography, which requires intravenous contrast administration, is the diagnostic test of choice. However, the contrast used in CT studies should be avoided in patients with chronic kidney disease due to the increased risk of contrast-induced nephropathy; in such patients, a ventilation/perfusion (V/Q) scan is the preferred diagnostic study.

A 43-year-old man comes to the emergency department after experiencing 4 episodes of coffee ground emesis that started earlier this morning. He also describes epigastric pain over the last 3-4 months that was relieved by over-the-counter antacids. He has no other past medical history. The patient has smoked a pack of cigarettes daily for the last 20 years but does not use alcohol or illicit drugs. Blood pressure is 70/40 mm Hg and pulse is 130/min and regular. Extremities are cool to the touch with loss of skin turgor. Intravenous access is obtained via 2 large-bore peripheral catheters, and rapid infusion of 2 liters of normal saline is initiated. This intervention is most likely to increase which of the following hemodynamic parameters? A. Aortic wall elasticity (%) B. Diastolic ventricular compliance (%) C. End-diastolic sarcomere length (%) D. Heart rate (%) E. Plasma renin activity (%) F. Total peripheral resistance (%) G. Ventricular muscle contraction velocity (%)

C. End-diastolic sarcomere length (%) In the treatment of hypovolemic shock, the most important intervention other than identifying and eliminating the source of bleeding is rapid infusion of blood products and crystalloid solutions such as normal saline. By infusing intravenous fluids, intravascular volume and ventricular preload can be increased rapidly. The increase in preload stretches the myocardium and increases the end-diastolic sarcomere length, leading to an increase in stroke volume and cardiac output by the Frank-Starling mechanism.

A 2-year-old boy is brought to the emergency department due to wheezing and difficulty breathing. The patient had been trick-or-treating with his parents and ate several packs of candy containing peanuts. After he receives an intramuscular epinephrine injection, his symptoms resolve. At a follow up appointment, an allergy specialist places droplets of various allergens on the patient's skin and punctures the epidermis at each site. After 15 minutes, the skin at the site with peanut extract is erythematous with a raised, itchy bump that improves by the time the family leaves the office. Four hours later, the parents notice a hard, red swelling at the puncture site. Which of the following is most likely involved in this secondary reaction? A. Cell lysis following IgG autoantibody binding (%) B. Complement activation by immune complexes (%) C. Epithelial damage by major basic protein (%) D. IgE-mediated histamine release from mast cells (%) E. Interferon gamma release from CD4+ T cells (%)

C. Epithelial damage by major basic protein (%) Following skin prick testing, this patient developed an erythematous, edematous welt that was followed 4 hours later by an indurated skin lesion. These findings are consistent with the early and late phases of a type I hypersensitivity reaction. After first exposure to an allergen (eg, peanuts), antigen specific IgE is produced by B-cells and binds to the surface of mast cells. If repeat exposure occurs, the bound IgE can cross-link and stimulate the release of preformed histamine and leukotrienes that cause vasodilation and increased capillary permeability. The result is a rapid (eg, minutes after exposure) early-phase type I hypersensitivity response characterized by superficial dermal edema and erythema (eg, wheal and flare reaction) that can progress to a more systemic response (eg, anaphylaxis) (Choice D). The late phase of dermatologic type I hypersensitivity reactions manifests as an indurated skin lesion hours after exposure to the allergen due to local tissue damage caused by major basic protein released from eosinophils. In contrast, type IV hypersensitivity reactions develop over days because of the time needed to produce a cell-mediated immune response.

An 83-year-old woman is sent to the emergency department from the nursing home where she resides for evaluation of mental status changes. At baseline, she has mild memory impairment but is otherwise cognitively intact, calm, and cooperative with the nursing home staff. Over the past 24 hours, she has become increasingly combative and agitated and stayed up all night. Behavioral interventions and environmental modifications have not been helpful. The patient's medical conditions include hypertension and a history of anxiety and depression. Temperature is 37.2 C (99 F), blood pressure is 110/80 mm Hg, pulse is 84/min, and respirations are 18/min. Neurological examination is normal, but the patient is unable to attend to the conversation, is mildly disoriented, and cannot state the days of the week backwards. Without provocation, she strikes out at a nurse's aide standing next to her. Laboratory results are normal except for urinalysis, which shows an increased presence of white blood cells and is positive for nitrites. Head CT scan is negative. In addition to starting antibiotic therapy, which of the following medications is most appropriate to treat this patient's behavioral symptoms? A. Clozapine (%) B. Doxepin (%) C. Haloperidol (%) D. Lithium (%) E. Lorazepam (%) F. Temazepam (%)

C. Haloperidol (%) Delirium is an acute-onset "confusional state" characterized primarily by waxing and waning mental status changes and impaired attention. Disorientation, agitation, psychosis, and sleep disturbances may also occur. Delirium occurs secondary to an underlying medical condition, such as a urinary tract infection, and therefore the primary management is treating the underlying cause. The elderly and those with preexisting cognitive disorders are at a higher risk for delirium and may present with varying degrees of agitation. High-potency, first-generation antipsychotics (eg, haloperidol) and some second-generation antipsychotics (eg, quetiapine) can be used for the acute treatment of agitation and psychosis associated with delirium. Antipsychotic use is appropriate in the treatment of delirium in the elderly if the patient is at risk of acute harm to self or others and behavioral interventions have failed. Under these conditions, the benefits of antipsychotics (ie, the provision of safety) outweigh the potential risks when used at low doses and short durations.

A 58-year-old man comes to the emergency department due to sudden right-sided weakness. He has no sensory loss, problems speaking/swallowing, or difficulty with balance. The patient was previously told that he has elevated blood pressure, but he does not routinely follow up with his physician. He takes no medications. Examination shows intact cranial nerves and sensory function. The patient has 3/5 muscle strength on the right side. Initial CT scan without contrast reveals no abnormalities. Four weeks later, repeat brain imaging shows a 9-mm, fluid-filled cavitary lesion in the left internal capsule. This patient's condition is most likely caused by which of the following? A. Cardiac embolism (%) B. Carotid artery atherosclerosis (%) C. Hypertensive arteriolar sclerosis (%) D. Hypertensive encephalopathy (%) E. Hypoxic encephalopathy (%) F. Saccular aneurysm (%)

C. Hypertensive arteriolar sclerosis (%) This patient has pure motor hemiparesis and a small cavitary lesion in the internal capsule, characteristic of a lacunar infarct. This type of stroke affects the small penetrating arterioles that supply the deep brain structures (eg, basal ganglia, pons) and subcortical white matter (eg, internal capsule, corona radiata). Lacunar infarcts are primarily associated with chronic hypertension, which promotes lipohyalinosis, microatheroma formation, and hardening/thickening of the vessel wall (hypertensive arteriolar sclerosis). This leads to progressive narrowing of the arteriolar lumen and predisposes to thrombotic vessel occlusion, which causes characteristic clinical syndromes, depending on the portion of the brain affected: Posterior limb of the internal capsule and/or basal pons - pure motor hemiparesis or ataxia-hemiplegia syndrome (ie, ipsilateral limb ataxia out of proportion to motor deficit) Genu/anterior limb of the internal capsule and/or basal pons - dysarthria-clumsy hand syndrome (ie, dysarthria and dysphagia with clumsiness of one hand) Ventroposterolateral or ventroposteromedial thalamus - pure sensory stroke In the acute setting, CT imaging may not reveal the expected hypodensity of ischemic stroke due to the small infarct size (usually <15 mm). After several weeks, these necrotic lesions turn into cavitary spaces filled with cerebrospinal fluid and surrounded by scar tissue called lacunas

A 63-year-old man is brought to the emergency department after recent onset of high fever, confusion, headache, watery diarrhea, and cough. The patient has been smoking two packs of cigarettes daily for more than 30 years and has been diagnosed with chronic bronchitis. His temperature is 40.1 C (104 F), blood pressure is 100/70 mm Hg, pulse is 91/min, and respirations are 28/min. Sputum Gram staining reveals numerous neutrophils but no bacteria. Which of the following is the most likely cause of this patient's disease? A. Coccidioides immitis (%) B. Klebsiella pneumoniae (%) C. Legionella pneumophila (%) D. Mycobacterium kansasii (%) E. Mycoplasma pneumoniae (%)

C. Legionella pneumophila (%) The classic presentation of Legionnaires' disease includes high fever accompanied by diarrhea, confusion, and cough in an older adult who smokes. Legionella pneumophila is a common cause of community-acquired pneumonia, especially in patients with chronic lung disease. It commonly contaminates water and can be spread by inhalation of aerosolized water from natural water sources, tap water used in healthcare facilities, air conditioners, and other water-based cooling systems. Legionella infection should be suspected in a patient with radiographic evidence of pneumonia, a high fever, and accompanying gastrointestinal symptoms such as diarrhea. Sputum studies often show few or no bacteria since unique lipopolysaccharide chains on the outer membrane inhibit Gram staining. The diagnosis is most commonly made by PCR of a lower respiratory tract sample or detection of Legionella antigen in the urine. Legionnaires' disease can cause a life-threatening pneumonia if not recognized and treated properly (eg, floroquinolone or newer macrolide antibiotic)

Amniocentesis is performed on a 35-year-old pregnant woman. The phospholipid content of the amniotic fluid is determined in order to check for: A. Fetal neural tube defect (%) B. Erythroblastosis fetalis (%) C. Karyotype abnormalities (%) D. Fetal lung maturity (%) E. Cystic fibrosis (%) F. Fetal adrenal dysfunction (%)

D. Fetal lung maturity (%) Phospholipids, including dipalmitoyl phosphatidylcholine, are a major component of pulmonary surfactant. The level of phosphatidylcholine (also called lecithin) is measured in amniotic fluid in order to gauge fetal lung maturity. When the lecithin to sphingomyelin (L/S) ratio in amniotic fluid is > 2, the fetal lung is considered mature, meaning that it is producing adequate surfactant to avoid neonatal respiratory distress syndrome after birth. The L/S ratio is measured in cases of premature labor and/or premature rupture of the membranes in order to determine the timing of delivery and whether or not to give the mother corticosteroids to induce fetal surfactant production

A 26-year-old man is brought to the emergency department after a high-speed motorcycle collision. The patient was thrown several feet after his motorcycle collided with a car. On arrival, he is profoundly comatose. A CT scan of the head performed within an hour of the event shows no abnormalities. The patient dies several hours later, and autopsy examination is performed. Brain histopathology shows widespread axonal swelling, predominantly at the gray-white junction. Immunohistochemical staining of these axons reveals accumulation of alpha-synuclein and amyloid precursor proteins. Which of the following is the most likely cause of these observed findings? A. Diffuse cerebral hypoperfusion (%) B. Disruption of the bridging cortical veins (%) C. Glutamate-mediated neuronal injury (%) D. Interruption of the white matter tracts (%) E. Secondary microvascular spasm (%)

D. Interruption of the white matter tracts (34%) This patient has histopathologic findings of diffuse axonal injury (DAI), a type of severe traumatic brain injury that can occur from direct blunt force injury (eg, head hitting windshield) or abrupt changes in acceleration-deceleration (eg, restrained passenger coming to sudden stop after a collision). Transfer of force can result in immediate shearing of the white matter tracts or induce secondary biochemical changes leading to degradation of the axonal cytoskeleton with subsequent axon breakage. Normal axonal transport is inhibited, leading to accumulation of axonally transported proteins (eg, amyloid precursor, alpha-synuclein) within axonal swellings at the point of injury (eg, axonal bulb formation). Presentation varies based on the extent of injury; most patients are comatose (Glasgow Coma Score <8); however, those with very mild DAI may have only concussive symptoms (eg, headache, amnesia). CT scan has low sensitivity for diagnosis and is often normal, but MRI may demonstrate lesions at the gray-white junction. Microscopically, DAI is visible as widespread axonal swelling, most pronounced at the gray-white matter junction. Prognosis is poor, with up to 25% of cases resulting in death

A 66-year-old man is undergoing a procedure to control chronic throat pain due to Eagle syndrome, a condition frequently caused by a misshapen or elongated styloid process. During the procedure, the styloid process is trimmed surgically. However, the left glossopharyngeal nerve is accidentally transected. Which of the following is most likely to be seen as a result of this patient's nerve injury? A. Deviation of the protruded tongue toward the left (%) B. Hoarseness due to left vocal cord dysfunction (%) C. Impaired taste sensation from the anterior two-thirds of the tongue (%) D. Loss of general sensation at the tonsillar lining (%) E. Reduced salivary secretion from the submandibular gland (%)

D. Loss of general sensation at the tonsillar lining (%) The glossopharyngeal nerve (CN IX) originates in the medulla and exits the cranial cavity via the jugular foramen. This nerve has numerous functions, including: Somatic motor: Stylopharyngeus muscle only (elevates larynx during swallowing) Parasympathetic: Inferior salivatory nucleus → CN IX → otic ganglion → travels along auriculotemporal nerve (CN V3) → parotid gland secretion General sensory: Tympanic membrane (inner surface), eustachian tube, posterior third of tongue, tonsillar region, upper pharynx (afferent portion of gag reflex), carotid body, and carotid sinus Special sensory (taste): Posterior third of tongue Glossopharyngeal nerve lesions result in loss of general sensation in the upper pharynx, posterior tongue, tonsils, and middle ear cavity; loss of the gag reflex (afferent limb); and loss of taste sensation on the posterior third of the tongue

A 68-year-old woman with end-stage renal disease receiving intermittent hemodialysis comes to the office due to back pain. She says that she may have "pulled a muscle" while getting out of her car a week ago; since then she has had progressively worsening back pain. She has no leg numbness or weakness but reports malaise and fatigue. The patient also has hypertension and type 2 diabetes mellitus and was treated several weeks ago for staphylococcal bacteremia associated with the dialysis catheter. Her temperature is 38 C (100.4 F). On examination, she has tenderness over the upper lumbar vertebrae without overlying skin changes. The straight leg raise test is negative. Which of the following is the best next step in management of this patient? A. Analgesics and close follow-up (%) B. CT myelogram (%) C. Lumbar puncture (%) D. MRI of the spine (%) E. Serum protein electrophoresis (%)

D. MRI of the spine (%) Although this patient believes her back pain may be due to a muscle sprain, her presentation (localized bony back pain, low-grade fever, recent staphylococcal bacteremia) suggests vertebral osteomyelitis. Bacteria can access the spine by hematogenous spread from a distant infection (eg, skin or soft tissue, intravenous catheter), direct invasion from trauma or local spinal procedures (eg, lumbar puncture, spinal surgery), or direct spread from adjacent soft tissue infection. Hematogenous spread is most common as the adult vertebral bone has a very rich and vascular marrow. Increasing age can cause the nutrient arteries to develop a "corkscrew" anatomy, which allows bacteria to more easily penetrate the marrow cavity and cause local infection. Bacteremia due to intravascular devices (eg, hemodialysis catheters) increases risk of health care-related vertebral osteomyelitis. Offending organisms include Staphylococcus (most common is S aureus or coagulase-negative staphylococci) and various gram-negative organisms (eg, Pseudomonas). Vertebral osteomyelitis should be suspected in patients with new or worsening back pain, fever, and recent endocarditis or bacteremia (especially S aureus). It should also be suspected if there are new neurologic findings and fever, with or without back pain. Initial evaluation includes blood cultures and MRI of the spine, which is the most sensitive imaging method for diagnosing vertebral osteomyelitis (Choice C) Lumbar puncture is typically used for diagnosing meningitis and has a low yield for diagnosing vertebral osteomyelitis. CT-guided bone biopsy is usually preferred for isolating the organism after imaging confirms the diagnosis of vertebral osteomyelitis.

33-year-old man comes to the emergency department due to 3 days of shortness of breath, profound fatigue, and chills. The patient has a history of intravenous drug use. He was enrolled in a methadone program but admits to relapsing last week. Temperature is 40 C (104 F), blood pressure is 75/40 mm Hg, pulse is 122/min and regular, and respirations are 40/min. He is admitted to the intensive care unit but dies despite treatment efforts. Lung autopsy findings are shown in the image below. Which of the following is the most likely diagnosis in this patient? A. Miliary tuberculosis (%) B. Mycotic aortic aneurysm (%) C. Severe small airway obstruction (%) D. Tricuspid valve endocarditis (%) E. Venous thromboembolism (%)

D. Tricuspid valve endocarditis (%) The lung specimen above shows multiple wedge-shaped hemorrhagic infarcts in the periphery of the lung, which, given this patient's presentation, are most likely due to septic pulmonary emboli. Patients with intravenous drug use are at increased risk of developing tricuspid valve endocarditis, most commonly due to Staphylococcus aureus. The clinical presentation is typically acute with high-grade fever, and tachycardia and hypotension due to septic shock. The majority of patients with tricuspid valve endocarditis experience embolization of tricuspid valve vegetation fragments; these fragments lodge in distal portions of the pulmonary arterial tree and cause septic pulmonary infarcts. The infarcts are typically wedge-shaped due to the triangular perfusion field of small arteries at the lung periphery. Due to the relatively low density of lung tissue (which allows blood seepage into tissue during infarction) and a dual blood supply (ie, pulmonary and bronchial arteries), pulmonary infarcts are typically hemorrhagic (red) rather than ischemic (white) (Choice E) Venous thromboembolism in the pulmonary vasculature (ie, thrombotic pulmonary embolism) can also cause wedge-shaped hemorrhagic infarct in the periphery of the lung. However, this patient's high-grade fever and recent intravenous drug use are more suggestive of septic emboli from tricuspid valve endocarditis. In addition, multiple pulmonary infarcts are more consistent with septic embolization than venous thromboembolism. Educational objective: Pulmonary infarcts are typically hemorrhagic (red) and wedge-shaped in the periphery of the lung. Intravenous drug users are at increased risk of tricuspid valve endocarditis, which can cause multiple septic pulmonary infarcts due to embolization of tricuspid valve vegetation fragments.

A 63-year-old man comes to the emergency department due to dyspnea. Over the past several days, the patient has experienced progressively worsening shortness of breath while walking his dog around the block. In addition, he could not breathe while lying in bed last night and fell asleep only after moving to a recliner. The patient had an acute myocardial infarction 2 years ago and has been nonadherent with his medications and follow-up appointments. Temperature is 36.7 C (98 F), blood pressure is 122/74 mm Hg, pulse is 94/min, and respirations are 22/min. Physical examination shows bibasilar lung crackles, jugular venous distension, and bilateral pitting edema in the lower extremities. Chest x-ray reveals cardiomegaly and pulmonary venous congestion. Which of the following factors is most likely contributing to this patient's symptoms? A. Decreased arteriolar resistance (%) B. Decreased plasma renin activity (%) C. Decreased ventricular end-diastolic pressure (%) D. Increased plasma brain natriuretic peptide concentration (%) E. Increased sympathetic nervous system activity (%)

E. Increased sympathetic nervous system activity (%) This patient's progressive dyspnea, orthopnea, and lower extremity swelling are consistent with acute decompensated heart failure. Heart failure occurs when a structural or functional cardiac disorder impairs ventricular filling or ejection of blood, causing reduced cardiac output and elevated filling pressure. The reduced cardiac output causes an initial drop in blood pressure, which triggers compensatory neurohormonal activity mainly via stimulation of the sympathetic nervous system and renin-angiotensin-aldosterone system (RAAS). These adaptations function together in an effort to improve organ perfusion by increasing cardiac chronotropy and inotropy (improves cardiac output), promoting arterial and venous vasoconstriction (maintains perfusion pressure), and expanding the extracellular fluid compartment (improves circulating blood volume). However, over time, these responses lead to adverse consequences that perpetuate a downward spiral of progressive cardiac deterioration. Chronic hemodynamic stress (eg, increased preload and afterload) and prolonged exposure to sympathetic drive (catecholamines) and RAAS stimulation (angiotensin II, aldosterone) lead to deleterious remodeling with worsening cardiac function and eventual symptomatic decompensation.

A 62-year-old woman with no significant medical history is brought to the emergency department due to fatigue and substernal chest pain that began 6 hours ago. On arrival, ECG is consistent with ST-segment elevation myocardial infarction. Coronary angiography shows right-dominant coronary circulation and a thrombotic occlusion of the proximal right coronary artery, which supplies blood to the patient's right ventricle and the inferior and posterior portions of the left ventricle. A drug-eluting stent is placed, and she is discharged 2 days later without complication. After 6 weeks, the patient follows up in the clinic and undergoes echocardiography that shows left ventricular contractile dysfunction with normal right ventricular function. Which of the following characteristics of the right ventricle compared to the left ventricle best explains these echocardiography findings? A. Higher resting oxygen extraction (%) B. Less dependence on collateral circulation (%) C. Less ischemic preconditioning (%) D. More active fibroblast proliferation (%) E. Perfusion during both systole and diastole (%)

E. Perfusion during both systole and diastole (%) Myocardial infarction (MI) involving the left ventricle (LV) commonly leads to scarring and a sustained reduction in contractile function; however, contractile function of the right ventricle (RV) almost always returns to normal following MI. Some of the reasons for protection of the RV from infarction include: The relatively small muscle mass and afterload of the RV create less oxygen demand and necessitate lower oxygen extraction at rest. This allows for a large capacity to increase oxygen extraction during periods of ischemia. The relatively low systolic pressure of the RV (eg, ≤25 mm Hg) allows for coronary perfusion throughout the cardiac cycle; during MI, this enables the RV to pull blood flow from collateral vessels during both systole and diastole. In contrast, the high systolic pressure of the LV (eg, 120 mm Hg) blocks coronary blood flow of the LV walls during systole, allowing for perfusion during diastole only

A 26-year-old woman is brought to the emergency department due to acute-onset diplopia. Medical history is significant for episodes of blurry vision involving her right eye that occurred 6 months and 2 years ago. These episodes were associated with deficits in color vision and pain made worse with eye movement. The patient recovered the majority of her visual acuity after a few months in both cases. On neurologic examination, she has a visual acuity of 20/20 OS and 20/40 OD, mild right optic disk atrophy, and a relative afferent pupillary defect in the right eye. There is slowed and impaired adduction of the left eye with right lateral gaze. Convergence testing shows normal adduction in both eyes. The remainder of the neurologic examination is unremarkable. This patient's diplopia is most likely caused by which of the following mechanisms? A. Impaired neuromuscular transmission (%) B. Loss of axons (%) C. Muscle fiber inflammation and necrosis (%) D. Nerve compression (%) E. Reduced saltatory conduction (%)

E. Reduced saltatory conduction (%) Due to the acute demyelination seen with MS, propagation of the impulse cannot occur, as the distance between the sodium channels at the nodes of Ranvier precludes sequential activation. This causes a conduction block. Over time, sodium channels eventually redistribute across the naked axon and surviving oligodendrocytes partially remyelinate neurons, allowing for some restoration of signal transmission (explaining why some of the symptoms and signs of MS resolve to a variable extent).

A 48-year-old woman comes to the office with a 4-month history of pain, stiffness, and swelling of her hands, feet, and knees that is associated with daily fatigue. She has taken over-the-counter nonsteroidal anti-inflammatory agents, but they only temporarily relieve the pain. The patient has no other medical issues. She does not use tobacco, alcohol, or illicit drugs and is not sexually active. Vital signs are within normal limits. BMI is 35 kg/m2. The patient walks with a limp due to pain in the foot. There is symmetric swelling, tenderness, and restricted range of motion involving the wrists, ankles, forefeet, and knees. There is no skin rash. Laboratory studies show anemia. Which of the following is most likely to be the earliest finding during the development of this patient's condition? A. Fibrillation of articular cartilage (%) B. Joint subluxation (%) C. Marginal bone erosions (%) D. Osteophyte formation (%) E. Synovial neovascularization (%)

E. Synovial neovascularization (%) This patient has a chronic, symmetric, polyarticular arthritis with joint swelling and stiffness consistent with early rheumatoid arthritis (RA). RA is a progressive autoimmune disorder that is often associated with signs of systemic inflammation (eg, fatigue, fever, anemia). It has a peak incidence at age 50-75 but can occur at any age; women are affected more commonly than men. The pathogenesis of RA begins with activation of T lymphocytes in response to rheumatoid antigens (eg, citrullinated peptides, type II collagen). Activated T cells release cytokines that cause synovial hyperplasia with recruitment of additional mononuclear cells. The accelerated metabolic rate of the inflamed synovial tissue leads to local hypoxia and increased production of hypoxia-inducible factor 1 and vascular endothelial growth factor by local macrophages and fibroblasts, resulting in synovial angiogenesis (neovascularization). As the disease progresses, new blood vessels provide nutrients that facilitate expansion of inflammed synovium into a rheumatoid pannus, an invasive mass composed of fibroblast-like synovial cells, granulation tissue, and inflammatory cells. Over time, the pannus encroaches into the joint space and can destroy the articular cartilage and erode the underlying subchondral bone (Choice C). Ossification of the pannus can lead to fusion of the bones across the affected joint (bony ankylosis)

A 23-year-old asymptomatic male participates in clinical research and is found to be homozygous for the apolipoprotein E-4 allele. In the future, this patient is most likely to suffer from which of the following? A. Familial hypercholesterolemia (%) B. Hypertrophic cardiomyopathy (%) C. Diabetes mellitus, type 2 (%) D. Peptic ulcer disease (%) E. Polycystic kidney disease (%) F. Alzheimer dementia (%)

F. Alzheimer dementia (%) Late-onset familial Alzheimer disease is associated with the ε4 allele of Apolipoprotein E. The exact mechanism of its influence is not known. It is thought that the ApoE4 protein may be involved in the formation of senile plaques. (Choice A) Familial hypercholesterolemia is an autosomal dominant disorder. It is associated with a defect in low-density lipoprotein (LDL) receptors. This defect leads to decreased hepatic LDL uptake and severe elevation in total cholesterol and LDL levels

64-year-old woman is evaluated for episodic urinary incontinence. Urodynamic studies reveal an overactive bladder. Symptoms persist after behavioral interventions, and the patient is unable to tolerate medical treatment. Low-amplitude electrical stimulation therapy that helps modulate neural control of the urinary bladder muscle, urethral sphincter, and pelvic muscles is planned. A stimulating electrode is most likely to be placed close to which of the following structures during this procedure? A. Nucleus accumbens (%) B. Subthalamic nucleus (%) C. Vagus nerve (%) D. T6 nerve root (%) E. L5 nerve root (%) F. S3 nerve root (%)

F. S3 nerve root (%) This patient has urge incontinence due to an overactive bladder. In patients unresponsive to behavioral therapy and unable to take medications, a bladder stimulator is sometimes used. Neural stimulation is used to augment neural signals to the pelvic floor muscles and urinary sphincter, which are innervated from nerves derived from the S2-S4 nerve roots: Somatic innervation of the pelvic floor muscles helps to maintain continence because these muscles stabilize the urethra against the anterior vaginal wall. This contraction decreases the angle between the bladder neck and the urethra (ie, urethrovesical angle), thereby compressing the urethra, stopping urine flow, and maintaining continence. Therefore, increasing the strength of the pelvic floor muscles (either through physical therapy or neuromodulatory stimulation) promotes continence. The external urethral sphincter (EUS) is also under somatic control via the pudendal nerve (S2-S4); therefore, stimulation of these nerve roots will increase EUS tone to help improve urinary continence. Although the pelvic splanchnic nerves, derived from S2-S4, are classically described as providing parasympathetic input to the bladder and urethral sphincter (which promotes bladder contraction and may worsen incontinence), they are also involved in the bladder stretch-contraction reflex. Neural stimulation seems to inhibit this reflex to improve continence.

A 43-year-old woman comes to the office for an initial appointment due to ongoing abdominal pain, general weakness, decreased appetite, and dizziness. She says the pain is ruining her life and is worried that her previous physicians may have missed something. Over the past several years, the patient has been hospitalized 3 times with similar symptoms. No etiology for the pain has been identified despite extensive workups, including several abdominal CT scans and an exploratory laparotomy. The patient describes chronic abdominal pain since adolescence and is concerned as the nonprescription analgesics she takes are ineffective. She has no history of psychiatric diagnoses or substance abuse. Physical examination, vital signs, and laboratory tests (including chemistry panel, complete blood count, and urinalysis) are within normal limits. Which of the following is the most appropriate next step in the management of this patient? A. Explain that symptoms are psychological in nature (%) B. Obtain gastroenterology consult (%) C. Order abdominal MRI scan (%) D. Prescribe an opioid analgesic (%) E. Reassure that all tests are negative and further workup is not indicated (%) F. Refer for psychiatric treatment (%) G. Schedule regular outpatient office visits (%)

G. Schedule regular outpatient office visits (%) This patient's preoccupation with unexplained medical symptoms and excessive health care use are characteristic of somatic symptom disorder. The best approach is to schedule regular visits with her primary care provider, who can monitor her condition and avoid unnecessary diagnostic testing and specialist referrals

What is the functional residual capacity of the lung?

How much air remains in the lungs after a passive exhalation

A 7-year-old girl is brought to the clinic due to nasal congestion with facial pain. The patient first developed congestion over a year ago. Her parents have been treating it with over-the-counter allergy medications, but there has been no improvement. Over the past 4 months, the congestion has worsened, and now the patient has difficulty breathing through her nose. She also developed a dry cough and a constant, dull pain over her cheeks. The patient's stools have been loose. Temperature is 37.8 C (100 F). Weight is at <1st percentile at 18 kg (39.7 lb), decreased from 19 kg (41.9 lb) 3 months ago. Examination reveals copious yellow mucus within both nares. Translucent, gray, shiny masses obscure the middle turbinates bilaterally. Lymphadenopathy is not present. The lungs have coarse breath sounds bilaterally. The abdomen is soft with no organomegaly. Which of the following is the most likely diagnosis? A. Cystic fibrosis (%) B. HIV infection (%) C. Nasopharyngeal carcinoma (%) D. Primary ciliary dyskinesia (%) E. Seasonal allergic rhinitis (%)

This patient has chronic rhinosinusitis with nasal polyposis and failure to thrive, findings concerning for cystic fibrosis (CF). CF is an inherited, multisystem disorder characterized by the abnormal transport of sodium and chloride due to a mutation in the CFTR gene. Although common CF mutations (eg, ΔF508) are often identified on newborn screening, less common mutations may go undetected and cause milder symptoms later in childhood. Abnormal CFTR function causes thick, viscous respiratory secretions and impaired mucociliary clearance, leading to chronic sinopulmonary disease (eg, chronic rhinosinusitis). Patients typically have chronic cough, nasal congestion, and facial pain, as seen in this patient. Bilateral nasal polyps, benign outgrowths of inflamed mucosa, are also common due to chronic infection and present as nontender, shiny, gray masses in the nasal cavity or paranasal sinuses. In CF, viscous secretions can also block pancreatic ducts, leading to pancreatic insufficiency. Decreased or absent pancreatic enzymes cause fat malabsorption with oily, loose stools and failure to thrive and/or weight loss. Over time, pancreatic injury can also lead to insufficient insulin production and CF-related diabetes

A 55-year-old, right-handed man comes to the emergency department due to recent onset of severe, throbbing, right-sided headache and double vision. His medical history includes poorly controlled hypertension and chronic tobacco use. Neurologic examination shows that he is awake, alert, and oriented and can follow commands. Visual fields and optic fundi are normal. The position of the right eye is down and out with ipsilateral ptosis, and the right pupil is dilated and nonreactive to both light and accommodation. Left eye examination is normal. Based on this patient's neurologic deficits, CT angiography of the head is most likely to reveal an aneurysm arising from which of the following locations in the image below?

This patient has right oculomotor nerve (CN III) palsy secondary to a compressive aneurysm arising from the junction of the right posterior communicating artery with the internal carotid artery. Saccular aneurysms typically arise from branch points on the circle of Willis, and most (85%) affect the anterior circulation (eg, anterior communicating, posterior communicating, and middle cerebral arteries). Chronic smoking and poorly controlled hypertension are risk factors. Unruptured aneurysms are usually asymptomatic, but patients may experience headache and cranial neuropathies due to mass effect. CN III is a pure motor nerve that exits the midbrain between the posterior cerebral and superior cerebellar arteries and courses along the posterior communicating artery, making it particularly susceptible to injury from posterior communicating artery aneurysms. It carries general visceral efferent fibers on its surface (for the pupillary light and near-reflex pathways) and general somatic efferent fibers within its interior (innervating superior rectus, inferior rectus, medial rectus, inferior oblique, and levator palpebrae superioris muscles). Consequently, aneurysmal compression of CN III produces mydriasis (due to superficial parasympathetic fiber damage) with diplopia, ptosis, and down and out deviation of the ipsilateral eye (due to somatic efferent fiber injury).

Choice A) The junction of the anterior communicating artery and anterior cerebral artery is the most common location for saccular aneurysms; however, aneurysms in this region typically .

compress the central optic chiasm, causing bitemporal hemianopia

Respiratory distress syndrome classically presents in premature infants with increased work of breathing and hypoxia at birth due to surfactant deficiency. Poor alveolar compliance leads to widespread atelectasis and decreased_______. Airway _____ is often increased due to lung inflammation and edema.

functional residual capacity increased resistance

Educational objective: The oculomotor nerve (CN III) is most susceptible to injury from ipsilateral_____ Aneurysmal compression of CN III produces mydriasis (due to superficial parasympathetic fiber damage) with diplopia, ptosis, and down and out deviation of the ipsilateral eye (due to somatic efferent fiber injury).

posterior communicating artery aneurysms.

the inferior thyroid arteries provide blood to the thyroid gland and other structures of the anterior neck. From the thyrocervical trunk, the inferior thyroid artery courses deep to the internal jugular vein, vagus nerve, and common carotid artery before turning toward the thyroid. As it approaches the thyroid, the artery comes in close proximity to the ____nerve

recurrent laryngeal

(Choice E) Posterior communicating artery aneurysms cause

symptoms on the same side as the lesion due to damage to the ipsilateral oculomotor nerve. A left posterior communicating artery aneurysm would cause left-sided mydriasis, ptosis, and eye deviation.

(Choices F, G, and H) Approximately 15% of saccular aneurysms arise from the posterior circulation (eg, branches of the basilar and vertebral arteries). Although these aneurysms could potentially cause oculomotor palsy by compressing the oculomotor nerve as it exits the midbrain, this presentation is rare and usually associated only

with very large aneurysms that cause multiple neurologic deficits.

Patients with proximal radial neuropathy typically have weakness during

wrist and finger extension (wrist drop) and variable sensory loss over the posterior arm and forearm