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Question 981Question →

A 22-year-old tall, thin man presents to the emergency department with a sudden onset of right-sided chest pain and shortness of breath. The symptoms started abruptly while he was sitting and studying. He has no significant past medical history, takes no medications, and does not smoke. His temperature is 37.0°C (98.6°F), blood pressure is 120/80 mmHg, heart rate is 112/min, respiratory rate is 22/min, and oxygen saturation is 96% on room air. Physical examination reveals decreased breath sounds and hyperresonance to percussion over the right hemithorax. Arrange the following differential diagnoses in order from highest to lowest pre-test probability based on this patient's clinical presentation.

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Answer

The correct order from highest to lowest pre-test probability is: Primary spontaneous pneumothorax, Pulmonary embolism, Community-acquired pneumonia, and Acute myocardial infarction.
Primary spontaneous pneumothorax is the most probable diagnosis due to the characteristic physical exam (hyperresonance, decreased breath sounds) and demographic profile (tall, thin, young male). Pulmonary embolism is a distant second as a life-threatening possibility that lacks specific risk factors here. Pneumonia and myocardial infarction are much less likely due to the absence of fever or cough and the young age with a lack of cardiovascular risk factors, respectively.

Step-by-Step Solution

1
Analyze the patient's demographics and presenting symptoms.
The patient is a young, tall, thin male with sudden-onset right-sided chest pain and dyspnea at rest.
Identifying the classic demographic profile and symptom onset helps narrow the differential diagnosis for acute chest pain.
2
Correlate symptoms with physical examination findings.
Decreased breath sounds and hyperresonance on the right side strongly indicate a collection of air in the pleural space.
Physical exam findings are crucial for distinguishing between pulmonary, cardiac, and pleural etiologies.
3
Prioritize the differential diagnoses.
Primary spontaneous pneumothorax perfectly fits the entire clinical picture. Pulmonary embolism is a dangerous alternative but lacks specific risk factors. Pneumonia is unlikely without infectious signs, and myocardial infarction is highly improbable given the patient's age and health.
Pre-test probability must be ordered by matching clinical features while keeping life-threatening conditions in the differential.

Key Concept

Formulating a prioritized differential diagnosis for sudden-onset chest pain based on specific patient demographics and physical examination findings.
Estimated Time:1m 0s
Question 982Question →

Emergency medical personnel transport a 55-year-old man to the acute care bay following an episode of voluminous hematemesis at his home. The patient's wife notes he has a long-standing history of alcohol-associated cirrhosis. Upon transfer to the stretcher, the patient is obtunded, pale, and has audible gurgling during inspiration. Vital signs include a temperature of 36.5 C (97.7 F), a blood pressure of 72/42 mm Hg, a heart rate of 144/min, and a respiratory rate of 28/min. Oxygen saturation cannot be reliably obtained due to poor peripheral perfusion.

Arrange the following management steps in the most appropriate chronological sequence for this patient's initial stabilization and triage.

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Answer

The correct sequence prioritizes the ABCs of resuscitation: first securing the airway, then establishing vascular access, followed by volume resuscitation with blood products, administering specific pharmacologic therapy for variceal bleeding, and finally arranging for definitive endoscopic intervention.
The correct sequence adheres to fundamental trauma and critical care principles (Advanced Trauma Life Support guidelines applied to medical resuscitation). The most immediate threat to life is loss of the airway, necessitating intubation. Once the airway is safe, circulation is addressed by gaining access and immediately replacing lost volume with blood. Only after the patient is stabilized and resuscitated should disease-specific medical management (octreotide/antibiotics) and definitive procedural interventions (endoscopy) take place.

Step-by-Step Solution

1
Evaluate and secure the airway.
Endotracheal intubation is performed.
The patient has altered mental status and active hematemesis with gurgling, indicating an unprotected airway and high aspiration risk.
2
Establish vascular access.
Two large-bore peripheral IV lines are placed.
Access is a mandatory prerequisite for treating hemorrhagic shock and must precede medication or fluid delivery.
3
Initiate volume resuscitation.
Uncrossmatched type O-negative blood is transfused.
The patient's profound hypotension and tachycardia indicate class III/IV hemorrhagic shock requiring immediate blood product replacement.
4
Administer targeted pharmacotherapy.
Intravenous octreotide and ceftriaxone are given.
These medications reduce splanchnic blood flow and prevent infectious complications in variceal bleeding, respectively, but are secondary to the ABCs.
5
Consult for definitive care.
Urgent esophagogastroduodenoscopy is arranged.
Endoscopy allows for visualization and band ligation of varices, but can only be safely performed in a hemodynamically stabilized, intubated patient.

Key Concept

In acute hemorrhagic shock with altered mental status, management must strictly follow the ABC (Airway, Breathing, Circulation) resuscitation sequence before initiating disease-specific medical or procedural interventions.
Question 983Question →

A 65-year-old man presents to the emergency department with the sudden onset of severe, "tearing" chest pain that radiates to his back. He has a 15-year history of poorly controlled hypertension. On physical examination, his blood pressure is 185/110 mmHg in the right arm and 145/90 mmHg in the left arm. His heart rate is 110/min. An electrocardiogram shows sinus tachycardia and voltage criteria for left ventricular hypertrophy, but no acute ST-segment or T-wave changes. When formulating the differential diagnosis for this patient, which of the following life-threatening conditions must be prioritized?

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Answer: Acute aortic dissection

Answer

Acute aortic dissection
The correct answer is acute aortic dissection because the patient presents with classic features that demand its immediate inclusion at the top of the differential diagnosis. The sudden onset of severe, "tearing" chest pain that radiates to the back, combined with a history of long-standing hypertension and a significant blood pressure discrepancy (>20 mmHg difference) between the arms, is the hallmark presentation of an aortic dissection. Recognizing this pattern is essential to avoid premature closure on more common but incorrect diagnoses.

Step-by-Step Solution

1
Analyze the patient's history and symptoms.
The patient has a history of poorly controlled hypertension and presents with sudden-onset, severe, tearing chest pain radiating to the back.
Identifying the quality, onset, and radiation of pain helps narrow the initial differential diagnosis.
2
Evaluate the physical examination findings.
There is a significant blood pressure discrepancy between the right and left arms (185/110 mmHg vs. 145/90 mmHg).
A blood pressure difference of >20 mmHg between the arms is a major red flag that points toward a vascular emergency rather than a cardiac or pulmonary etiology.
3
Synthesize the findings to formulate the most likely differential diagnosis.
The combination of severe tearing pain, radiation to the back, and asymmetric blood pressures makes acute aortic dissection the most critical condition to prioritize.
Failing to prioritize this must-not-miss diagnosis leads to premature closure and potentially fatal delays in management.

Key Concept

Formulating a differential diagnosis for acute chest pain requires recognizing classic 'red flag' presentations, such as tearing pain and blood pressure discrepancies, which strongly suggest acute aortic dissection.
Question 984Question →

A hospital ethics committee is reviewing several complex cases involving the refusal of recommended medical interventions. Based on current legal and ethical standards, which mandated physician action best corresponds to each clinical presentation?

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Items

A 28-year-old trauma victim, carrying an authenticated advance directive stating she is a Jehovah's Witness and refuses all blood products, presents with class IV hemorrhagic shock; her husband demands she receive blood.
The parents of a 4-year-old child diagnosed with acute lymphoblastic leukemia refuse chemotherapy, arguing that prayer alone will cure the malignancy.
A 65-year-old man with intact cognition and metastatic pancreatic cancer decides to discontinue his scheduled palliative chemotherapy regimens against his oncologist's advice.
The adult daughter and designated health care proxy for an 80-year-old man in a persistent vegetative state declines the surgical placement of a feeding tube, citing multiple past conversations where he explicitly rejected such measures.
A 30-year-old competent woman at 39 weeks gestation with fetal bradycardia firmly declines an emergent cesarean delivery, understanding the high probability of fetal demise.

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Answer

The trauma victim's directive supersedes the husband's demands. The pediatric leukemia case requires judicial intervention. The competent adult stopping chemotherapy must be supported in his decision. The proxy refusing the feeding tube is validated by substituted judgment. The pregnant patient's refusal of the cesarean delivery must be accepted.
Each pairing correctly applies fundamental U.S. medical ethics doctrines to complex refusal scenarios. Advance directives overrule surrogates; the state protects children from life-threatening medical neglect; competent adults may refuse any care; substituted judgment relies on prior statements; and maternal bodily autonomy supersedes fetal indications.

Step-by-Step Solution

1
Analyze the legal standing of the trauma victim's advance directive versus her husband's demands.
The advance directive takes precedence.
An authenticated advance directive is a direct extension of a competent patient's autonomy and legally binding, overriding any contradictory surrogate requests.
2
Evaluate the parental refusal of pediatric leukemia treatment.
The refusal must be legally challenged.
While parents generally have wide latitude in medical decision-making for their children, they cannot refuse standard-of-care, life-saving treatments (parens patriae doctrine).
3
Assess the competent adult's refusal of further cancer therapy.
The refusal must be honored.
Decision-making capacity grants adults the absolute right to refuse any intervention, including life-extending measures, without coercion.
4
Determine the validity of the proxy's decision for the patient in a vegetative state.
The proxy's refusal is ethically valid.
The proxy is appropriately using the standard of substituted judgment by basing the refusal on the patient's previously articulated values and conversations.
5
Analyze the maternal-fetal conflict involving the refusal of an emergent cesarean section.
The maternal refusal must be respected.
Courts and ethics bodies consistently uphold that a competent pregnant woman cannot be compelled to undergo invasive surgical procedures, prioritizing maternal bodily autonomy over fetal risks.

Key Concept

Ethical and legal boundaries of treatment refusal, surrogate decision-making, and bodily autonomy.
Question 985Question →

A 54-year-old woman is brought to the emergency department via ambulance due to sudden-onset difficulty breathing, lightheadedness, and a diffuse rash. Her symptoms began 20 minutes after eating a meal containing shellfish at a local restaurant. En route and upon arrival, she received a total of 2 L of intravenous normal saline and two separate doses of 0.3 mg intramuscular epinephrine, spaced 5 minutes apart. The patient is lethargic but arousable and complains of a "tight throat" and severe nausea. Her medical history is significant for essential hypertension, generalized anxiety disorder, and migraine headaches. Her daily medications include lisinopril, propranolol, and sertraline. Her temperature is 37.0°C (98.6°F), blood pressure is 76/42 mm Hg, pulse is 62/min, and respirations are 26/min. Oxygen saturation is 94% on 4 L/min via nasal cannula. Physical examination reveals diffuse, intensely pruritic erythematous plaques over the trunk and extremities, along with mild facial and lip swelling. Lung auscultation demonstrates diffuse bilateral expiratory wheezing. She is speaking in short phrases without stridor. Which of the following is the most appropriate immediate next step in the stabilization of this patient?

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Answer: Administration of intravenous glucagon

Answer

The most appropriate next step is the administration of intravenous glucagon.
The correct answer is the administration of intravenous glucagon. This patient is experiencing severe anaphylactic shock that is refractory to the standard initial stabilization measures (intramuscular epinephrine and intravenous fluids). A critical diagnostic clue is the patient's heart rate of 62/min despite a blood pressure of 76/42 mm Hg. This inappropriate lack of compensatory tachycardia is due to her daily use of propranolol, a non-selective beta-blocker. Beta-blockers competitively inhibit the beta-1 and beta-2 adrenergic receptors, rendering standard doses of epinephrine ineffective for providing necessary inotropy, chronotropy, and bronchodilation. In patients with anaphylaxis who are unresponsive to epinephrine due to beta-blockade, intravenous glucagon is the stabilization treatment of choice. Glucagon binds to distinct glucagon receptors on the myocardium and smooth muscle, directly stimulating adenylyl cyclase and increasing intracellular cyclic AMP (cAMP) independent of the beta-adrenergic receptor. This alternative pathway restores cardiac contractility, increases heart rate, and aids in bronchodilation, successfully stabilizing the patient.

Step-by-Step Solution

1
Evaluate the patient's hemodynamic status and response to initial emergency therapy.
The patient remains in refractory anaphylactic shock despite receiving adequate intravenous fluid resuscitation and multiple doses of intramuscular epinephrine.
Recognizing refractory shock is essential to trigger alternative, non-standard stabilization pathways.
2
Analyze the patient's vital signs and medication history for complicating factors contributing to the refractory state.
The pulse is inappropriately low (62/min) for the degree of hypotension, and the patient's medication list includes propranolol.
Propranolol is a non-selective beta-blocker that blunts the physiologic response to endogenous catecholamines and exogenous epinephrine.
3
Determine the optimal pharmacologic intervention to bypass the blocked beta-adrenergic receptors.
Intravenous glucagon is selected as the immediate next step.
Glucagon acts on distinct myocardial and smooth muscle receptors to activate adenylyl cyclase, increasing intracellular cAMP and providing necessary inotropic and chronotropic effects independent of beta-adrenergic receptors.

Key Concept

Patients with anaphylaxis who are taking beta-blockers often develop refractory shock due to blunted beta-adrenergic responses; intravenous glucagon is the drug of choice for immediate stabilization because it bypasses the beta-receptor to increase intracellular cAMP.
Estimated Time:2m 0s
Question 986Question →

A 7272-year-old man is brought to the emergency department by his daughter due to progressive confusion, frequent falls, and a slow, shuffling gait that has worsened over the past three weeks. His medical history includes hypertension, mild cognitive impairment, and coronary artery disease, for which he takes aspirin and lisinopril. Vital signs are within normal limits. Neurological examination reveals a delayed response to questions, mild left-sided hemiparesis, and a pronator drift in the left arm. A non-contrast head CT is performed. The preliminary interpretation by the radiology resident states 'no acute intracranial hemorrhage; normal age-related volume loss.' However, your careful review of the images reveals unilateral effacement of the cortical sulci over the right cerebral hemisphere, medial displacement of the gray-white matter junction, and a 55-mm leftward midline shift. The extra-axial space over the right convexity shares the exact same radiodensity (attenuation) as the adjacent cerebral cortex.

Based on your interpretation of these imaging findings, which of the following is the most appropriate next step in patient management?

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Answer: Consult neurosurgery for management of a subacute subdural hematoma

Answer

Consult neurosurgery for management of a subacute subdural hematoma
The correct answer is to consult neurosurgery for management of a subacute subdural hematoma. The patient's CT scan describes a classic isodense subdural hematoma, which typically occurs 11 to 33 weeks after an inciting event (often mild trauma in the elderly). Because the decomposing blood becomes isodense to the adjacent cerebral cortex, the fluid collection itself can be nearly invisible. The diagnosis relies heavily on recognizing secondary signs of mass effect, including unilateral sulcal effacement, medial displacement (buckling) of the gray-white matter junction, and midline shift. Given the patient's symptomatic presentation (hemiparesis, confusion) and significant mass effect, urgent neurosurgical consultation is required for possible evacuation.

Step-by-Step Solution

1
Analyze the clinical presentation.
A 72-year-old man presents with a 3-week history of progressive confusion, falls, and new-onset left-sided hemiparesis.
Establishes a subacute timeline and lateralizing neurological deficits pointing to a right-sided cortical or extra-axial lesion.
2
Interpret the specific CT head findings.
Unilateral right-sided sulcal effacement, a 5-mm leftward midline shift, and an extra-axial space that is isodense to the adjacent cortex.
Mass effect indicates a space-occupying lesion. The isodense nature of the extra-axial collection is the classic radiologic signature of a subacute hematoma.
3
Synthesize the clinical and radiologic data to form a diagnosis.
The patient has a symptomatic subacute right-sided subdural hematoma.
Subdural blood transitions from hyperdense (acute) to isodense (subacute, 1-3 weeks) to hypodense (chronic). The timeline and imaging perfectly align.
4
Determine the appropriate management.
Immediate neurosurgical consultation is required.
The patient is symptomatic with significant midline shift, indicating impending or actual risk of herniation, which may necessitate surgical evacuation.

Key Concept

Subacute subdural hematomas (1 to 3 weeks old) are isodense to the cerebral cortex on non-contrast CT and can be subtly identified by unilateral sulcal effacement, medial buckling of the gray-white matter junction, and midline shift.
Estimated Time:1m 30s
Question 987Question →

Match each patient presentation evaluating for suspected coronary artery disease with the most appropriate next step in diagnostic test sequencing.

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Items

A 65-year-old man requires preoperative cardiac risk stratification prior to a femoral-popliteal bypass. His baseline electrocardiogram demonstrates a left bundle branch block. He is unable to walk on a treadmill due to severe claudication.
A 58-year-old woman with severe, actively wheezing asthma on multiple inhalers presents with progressive exertional chest tightness. She has advanced bilateral knee osteoarthritis, relies on a wheelchair, and cannot exercise.
A 72-year-old man is scheduled for an elective open abdominal aortic aneurysm repair. He has a history of hypertension but no cardiac symptoms. He routinely plays 18 holes of golf twice a week, walking the entire course.
A 55-year-old man with a history of coronary artery bypass grafting five years ago presents with new-onset exertional dyspnea. His resting electrocardiogram is normal and he routinely jogs three miles daily.
A 50-year-old man presents with episodic chest tightness occurring after heavy exertion. His resting electrocardiogram is completely normal, he takes no medications, and he works in construction, regularly lifting heavy materials.

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Answer

The correct pairings appropriately map each patient's clinical scenario to their indicated stress testing modality based on functional capacity, baseline ECG abnormalities, and comorbidities.
The correct diagnostic sequencing in suspected coronary artery disease depends on three primary factors: the patient's ability to exercise, their baseline electrocardiogram, and any specific comorbid contraindications. Standard exercise testing is preferred when possible. If the baseline ECG is uninterpretable (e.g., LBBB, paced rhythm) or if prior revascularization exists, imaging must be added. When exercise is impossible, pharmacologic stress is indicated. Vasodilators (adenosine) are necessary for LBBB but contraindicated in severe asthma, making dobutamine the correct choice for asthmatics. Finally, unnecessary testing should be avoided in asymptomatic preoperative patients with good functional capacity.

Step-by-Step Solution

1
Evaluate the patient's ability to exercise and estimate their functional capacity in metabolic equivalents (METs).
Patients who can achieve >4 METs should undergo exercise stress testing, while those who cannot require pharmacologic stress.
Exercise provides superior physiological assessment and prognostic information compared to pharmacologic stress.
2
Assess the baseline electrocardiogram for abnormalities that preclude standard interpretation.
Left bundle branch block, ventricular pacing, and >1 mm ST depression render standard exercise ECGs uninterpretable.
These baseline abnormalities require the addition of imaging, and in the case of LBBB, specifically necessitate vasodilator stress rather than chronotropic agents.
3
Identify specific contraindications to pharmacologic agents.
Asthma/reactive airway disease contraindicates vasodilators; arrhythmias or severe hypertension contraindicate dobutamine.
Selecting the correct pharmacologic agent prevents life-threatening iatrogenic complications.
4
Apply perioperative risk stratification guidelines.
Asymptomatic patients with good functional capacity require no further testing before surgery.
Testing does not change perioperative management in these robust patients and risks unnecessary delays or interventions.

Key Concept

Selection of Cardiac Stress Testing Modalities
Question 988Question →

A 67-year-old retired accountant presents to the pulmonology clinic with an 8-month history of progressively worsening shortness of breath on exertion and a dry, hacking cough. He denies fever, chills, chest pain, or recent travel. He has a 30-pack-year smoking history but quit 15 years ago. He has no history of occupational exposures to dust, mold, or asbestos. On physical examination, his oxygen saturation is 93% on room air. Pulmonary auscultation reveals fine, "Velcro-like" inspiratory crackles at both lung bases. Digital clubbing is present. Pulmonary function testing demonstrates a restrictive pattern with decreased diffusion capacity for carbon monoxide. High-resolution computed tomography (HRCT) of the chest reveals subpleural reticular opacities, traction bronchiectasis, and honeycombing that are most prominent in the lower lobes. To definitively confirm the diagnosis and rule out other interstitial lung diseases, a video-assisted thoracoscopic surgical (VATS) lung biopsy is performed.

Based on the most likely diagnosis, which of the following histopathologic findings are expected to be present on this patient's lung biopsy specimen? (Select two)

Select all that apply

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Answer: Spatial heterogeneity featuring alternating zones of dense scar, normal alveolar parenchyma, and honeycomb cysts; Temporal heterogeneity characterized by the simultaneous presence of dense acellular collagen and active fibroblastic foci

Answer

The correct findings are spatial heterogeneity (alternating zones of dense scar and normal lung) and temporal heterogeneity (simultaneous presence of old collagen and new fibroblastic foci).
The patient's clinical presentation and high-resolution computed tomography findings (subpleural, basilar-predominant reticulation and honeycombing) are classic for Idiopathic Pulmonary Fibrosis (IPF). The histologic correlate of IPF is the Usual Interstitial Pneumonia (UIP) pattern. The absolute hallmark of UIP on surgical lung biopsy is the presence of both spatial and temporal heterogeneity. Spatial heterogeneity refers to a patchy distribution of disease, where dense scarring and honeycomb cysts immediately alternate with areas of relatively normal lung parenchyma. Temporal heterogeneity means that fibrotic changes of different chronologic ages are present simultaneously; specifically, old dense acellular collagen is seen alongside active, young fibroblastic foci. Identifying these two features allows the pathologist to confirm the UIP pattern and confidently exclude other interstitial lung diseases.

Step-by-Step Solution

1
Analyze the patient's clinical and radiologic presentation.
The patient is an older male with progressive exertional dyspnea, dry cough, basilar Velcro-like crackles, clubbing, and HRCT showing basilar-predominant subpleural reticulation and honeycombing.
These demographic, clinical, and radiologic findings are the classic presentation of Idiopathic Pulmonary Fibrosis (IPF).
2
Identify the requisite pathologic pattern associated with the suspected diagnosis.
IPF is characterized histologically by the Usual Interstitial Pneumonia (UIP) pattern.
The definitive diagnosis of IPF requires matching the clinical syndrome with the UIP pattern on surgical biopsy when radiologic features are not completely definitive, assuming no other causes are identified.
3
Determine the defining microscopic features of the UIP pattern.
The hallmark features of UIP are marked spatial heterogeneity and temporal heterogeneity, often accompanied by honeycomb change.
To accurately diagnose UIP, a pathologist looks for alternating areas of normal and fibrotic lung (spatial heterogeneity) and mixed stages of fibrosis such as young fibroblastic foci alongside dense mature collagen (temporal heterogeneity).

Key Concept

The pathologic diagnosis of Idiopathic Pulmonary Fibrosis relies on identifying the Usual Interstitial Pneumonia (UIP) pattern, which is fundamentally characterized by both spatial and temporal heterogeneity on lung biopsy.
Question 989Question →

A 28-year-old woman, G1P0 at 24 weeks gestation, presents to the emergency department with sudden-onset shortness of breath and right-sided pleuritic chest pain. Vital signs are temperature 37.1°C (98.8°F), heart rate 115/min, blood pressure 110/70 mm Hg, respiratory rate 22/min, and oxygen saturation 94% on room air. Physical examination reveals clear breath sounds bilaterally and normal heart sounds. The lower extremities show no asymmetric swelling or erythema. Electrocardiogram demonstrates sinus tachycardia. The physician suspects a pulmonary embolism. Arrange the following diagnostic imaging studies in the most appropriate sequential order for evaluating this patient, assuming each preceding test is nondiagnostic.

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Answer

The correct sequential order for imaging in a pregnant patient with suspected pulmonary embolism is bilateral lower extremity compression ultrasonography, followed by plain chest radiography, and finally a ventilation-perfusion (V/Q) scan.
The correct diagnostic algorithm for suspected pulmonary embolism in pregnancy prioritizes minimizing radiation. The first step is bilateral lower extremity compression ultrasonography, which uses no ionizing radiation; if positive for deep vein thrombosis, therapeutic anticoagulation is initiated, and further imaging is safely avoided. If the ultrasound is negative, plain chest radiography is performed next. A chest X-ray exposes the patient to negligible radiation, can identify alternative diagnoses, and is absolutely necessary to interpret a V/Q scan. If the chest X-ray is normal, a ventilation-perfusion (V/Q) scan is the final step in the sequence. A V/Q scan is preferred over CT pulmonary angiography in this specific scenario because it delivers a significantly lower radiation dose to the maternal breast tissue.

Step-by-Step Solution

1
Determine the safest initial imaging modality for a pregnant patient with suspected pulmonary embolism.
Bilateral lower extremity compression ultrasonography.
It avoids ionizing radiation entirely. If it is positive for deep vein thrombosis, the patient will receive therapeutic anticoagulation, making further thoracic imaging unnecessary.
2
Select the next appropriate step if the initial non-radiating ultrasound is negative.
Plain chest radiography.
A chest X-ray provides minimal radiation, evaluates for alternative diagnoses such as pneumonia or pneumothorax, and dictates whether the subsequent diagnostic test should be a V/Q scan or CT pulmonary angiography.
3
Choose the definitive advanced imaging modality when the chest X-ray is normal.
Ventilation-perfusion (V/Q) scan.
When the chest X-ray is normal, a V/Q scan is preferred over CT pulmonary angiography because it delivers significantly less radiation to the rapidly proliferating maternal breast tissue.

Key Concept

In pregnant patients with suspected pulmonary embolism, diagnostic imaging is sequenced to minimize radiation exposure, beginning with lower extremity ultrasonography, proceeding to chest radiography if negative, and concluding with a V/Q scan if the chest X-ray is normal.
Question 990Question →

Match the following distinctive radiographic findings with their corresponding underlying rheumatologic or orthopedic diagnosis.

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Items

Punched-out periarticular erosions with overhanging edges ('rat-bite' erosions) and soft tissue swelling
Periarticular osteopenia, uniform joint space narrowing, and marginal erosions in the proximal interphalangeal and metacarpophalangeal joints
Asymmetric joint space narrowing, subchondral sclerosis, subchondral cysts, and osteophyte formation
Linear or punctate calcifications within the articular cartilage and menisci (chondrocalcinosis)
Squaring of vertebral bodies, syndesmophytes bridging adjacent vertebrae, and sacroiliac joint fusion

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Answer

The correct pairings accurately map classic radiographic findings to their respective degenerative, autoimmune, and crystalline joint diseases.
Correctly identifying these pathognomonic imaging findings allows for accurate differentiation between degenerative, inflammatory, and crystalline arthropathies, which is essential for establishing the precise diagnosis and guiding condition-specific management.

Step-by-Step Solution

1
Identify the characteristic radiographic findings of osteoarthritis.
Osteoarthritis is identified by mechanical wear patterns, specifically asymmetric joint space narrowing, subchondral sclerosis, and osteophytes.
Recognizing degenerative changes distinguishes them from inflammatory etiologies.
2
Identify the radiographic hallmarks of rheumatoid arthritis.
Rheumatoid arthritis presents with periarticular osteopenia and marginal erosions, typically in the PIP and MCP joints.
This confirms the diagnosis of an autoimmune, symmetric inflammatory polyarthropathy.
3
Differentiate crystalline arthropathies based on their specific imaging signs.
Gout causes punched-out erosions with overhanging edges, while CPPD causes linear calcification of the articular cartilage (chondrocalcinosis).
Each crystal type deposits in distinct locations and triggers unique local bony and cartilaginous changes.
4
Recognize the axial skeleton manifestations of seronegative spondyloarthropathies.
Ankylosing spondylitis presents with sacroiliitis, vertebral body squaring, and syndesmophytes.
These findings represent chronic inflammation and subsequent fusion of the axial skeleton.

Key Concept

Distinguishing musculoskeletal pathologies through characteristic radiographic findings
Question 991Question →

A 74-year-old man is brought to the emergency department from a long-term care facility due to worsening confusion and fever over the past 24 hours. He has a history of benign prostatic hyperplasia and relies on an indwelling Foley catheter.

On arrival, the patient is obtunded. His skin is warm and flushed.

Vital signs are:
Temperature: 39.4°C (102.9°F)
Blood pressure: 74/42 mm Hg
Pulse: 124/min
Respirations: 24/min
Oxygen saturation: 95% on room air.

The urinary catheter bag contains cloudy, dark urine.

Which of the following is the most appropriate initial step in the management of this patient?

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Answer: Rapid infusion of intravenous crystalloid fluids

Answer

Rapid infusion of intravenous crystalloid fluids
The correct answer involves the immediate administration of intravenous crystalloid fluids. This patient is in septic shock, indicated by his severe hypotension, compensatory tachycardia, altered mental status, fever, and a suspected urinary source. The foundation of initial stabilization for septic shock is prompt and aggressive fluid resuscitation (typically 30 mL/kg of crystalloids) to treat the relative hypovolemia caused by systemic vasodilation and capillary leak. This step must be taken immediately upon presentation to restore end-organ perfusion.

Step-by-Step Solution

1
Assess the patient's hemodynamic status and recognize the signs of shock.
The patient has a blood pressure of 74/42 mm Hg, tachycardia (124/min), and altered mental status, confirming distributive shock.
Identifying the severity of hemodynamic instability determines the urgency and type of intervention required.
2
Identify the likely etiology of the shock.
Fever, warm flushed skin, and cloudy urine from a Foley catheter strongly suggest septic shock secondary to a urinary tract infection.
Understanding the mechanism of shock (distributive/vasodilatory) guides the appropriate stabilization therapy.
3
Select the most urgent initial stabilization step.
Rapid infusion of intravenous crystalloid fluids is selected as the primary intervention.
Current sepsis guidelines mandate immediate fluid resuscitation to restore intravascular volume and improve tissue perfusion before initiating vasopressors or pursuing advanced imaging.

Key Concept

The immediate management of septic shock requires aggressive hemodynamic stabilization with intravenous crystalloid fluids prior to advanced imaging, vasopressor use, or unit transfer.
Question 992Question →

A 72-year-old man is brought to the emergency department by his family at 08:00 after they found him in bed with dense right-sided hemiplegia and severe global aphasia. He was last known to be neurologically at baseline when he went to sleep at 22:00 the previous night. Initial vital signs reveal a blood pressure of 165/90 mm Hg and a heart rate of 88/min. The acute stroke team is activated to evaluate the patient for potential endovascular reperfusion therapy.

Arrange the following neuroimaging modalities and their corresponding primary interpretive objectives in the correct chronological sequence required to definitively qualify this patient for extended-window mechanical thrombectomy.

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Answer

The correct sequence of imaging evaluation for a wake-up stroke being considered for extended-window mechanical thrombectomy is: Non-contrast CT (NCCT), followed by CT Angiography (CTA), then CT Perfusion (CTP), and finally Digital Subtraction Angiography (DSA).
The correct chronological interpretation sequence maximizes patient safety and adheres to established stroke protocols for the extended window (DAWN/DEFUSE-3 criteria). NCCT must be interpreted first to rule out bleeding before administering any contrast or considering reperfusion. CTA immediately follows to confirm an actionable occlusion. Because the patient is outside the standard 6-hour window (last known well was 10 hours prior), CTP is mandatory to prove a target mismatch (salvageable penumbra significantly larger than irreversible core) before proceeding to invasive DSA for the actual thrombectomy procedure.

Step-by-Step Solution

1
Obtain and interpret Non-contrast computed tomography (NCCT)
Excludes intracranial hemorrhage and provides an ASPECTS score.
Administering intravenous contrast or proceeding with any reperfusion therapy is absolutely contraindicated until active bleeding is ruled out.
2
Obtain and interpret Computed tomography angiography (CTA)
Identifies the presence of a proximal large vessel occlusion (LVO).
Endovascular therapy is only indicated if there is a targetable clot in a major cerebral vessel (e.g., ICA or M1 segment of the MCA).
3
Obtain and interpret Computed tomography perfusion (CTP)
Determines the core-to-penumbra mismatch volume.
For 'wake-up' strokes or those presenting in the 6-24 hour window, establishing that salvageable brain tissue still exists is mandatory to prevent futile recanalization and reperfusion injury.
4
Perform Digital subtraction angiography (DSA)
Provides real-time dynamic vascular mapping.
Used immediately during the intra-arterial procedure to navigate the catheter and guide the stent retriever or aspiration device to the clot.

Key Concept

Evaluation of a wake-up stroke for extended-window mechanical thrombectomy requires a strict sequential imaging protocol: exclude hemorrhage (NCCT), confirm a target occlusion (CTA), prove salvageable tissue exists (CTP), and therapeutically guide intervention (DSA).
Question 993Question →

A 29-year-old G1P0 woman is evaluated in the emergency department for a one-day history of lower abdominal cramping and mild vaginal spotting. She reports that her last menstrual period was approximately 6 weeks ago. Her medical history is unremarkable, and she takes no medications. Vital signs are within normal limits, including a heart rate of 78/min and a blood pressure of 116/74 mm Hg. Physical examination demonstrates a closed, non-tender cervical os. There is mild right-sided adnexal tenderness, but no palpable masses, guarding, or rebound tenderness are appreciated. A point-of-care urine pregnancy test is positive. Subsequent transvaginal ultrasonography reveals a thickened endometrial stripe measuring 14 mm14 \text{ mm}, no evidence of an intrauterine gestational sac, and normal-appearing ovaries bilaterally with no free fluid in the cul-de-sac. Laboratory testing shows a quantitative serum β\beta-hCG level of 1,100 mIU/mL1,100 \text{ mIU/mL}. Which of the following is the most appropriate next step in the diagnostic workup?

Show answer & explanation

Answer: Repeat quantitative serum β\beta-hCG level in 48 hours

Answer

Repeat quantitative serum β\beta-hCG level in 48 hours
The correct diagnostic sequence for a hemodynamically stable patient presenting with a pregnancy of unknown location (positive pregnancy test, empty uterus on ultrasound) and a quantitative serum β\beta-hCG level below the discriminatory zone (<1,500−2,000 mIU/mL< 1,500 - 2,000 \text{ mIU/mL}) is to repeat the β\beta-hCG level in 48 hours. At a level of 1,100 mIU/mL1,100 \text{ mIU/mL}, an intrauterine gestational sac may not yet be visible even in a normal, healthy pregnancy. By tracking the kinetic rise or fall of the hormone over 48 hours (a normal pregnancy should rise by at least 35-53%), the physician can accurately sequence the next steps—either repeating the ultrasound when the threshold is reached or intervening for an ectopic/failing pregnancy.

Step-by-Step Solution

1
Identify the patient's clinical status and imaging findings.
The patient is hemodynamically stable with a positive pregnancy test and a transvaginal ultrasound showing an empty uterus (pregnancy of unknown location).
Establishing stability determines if an immediate surgical intervention is necessary versus an algorithmic diagnostic workup.
2
Compare the patient's quantitative β\beta-hCG level to the transvaginal ultrasound discriminatory zone.
The patient's β\beta-hCG is 1,100 mIU/mL1,100 \text{ mIU/mL}, which is below the standard discriminatory zone of 1,500−2,000 mIU/mL1,500 - 2,000 \text{ mIU/mL}.
The discriminatory zone is the threshold above which a normal intrauterine gestational sac should consistently be visible on transvaginal ultrasound.
3
Determine the appropriate diagnostic sequence for a sub-threshold β\beta-hCG level.
Select serial tracking of β\beta-hCG levels over 48 hours.
Because the level is below the discriminatory zone, an empty uterus is an expected finding even in a normal early pregnancy. Serial testing dictates the next branch of the diagnostic algorithm.

Key Concept

In a hemodynamically stable patient with a pregnancy of unknown location and a β\beta-hCG level below the discriminatory zone (<1,500−2,000 mIU/mL< 1,500 - 2,000 \text{ mIU/mL}), the correct diagnostic sequence is to repeat the β\beta-hCG level in 48 hours rather than proceeding to invasive procedures.
Estimated Time:1m 15s
Question 994Question →

Cognitive biases are systematic errors in thinking that can significantly impact clinical decision-making and compromise patient safety. Match the following clinical scenarios with the specific cognitive bias that best explains the physician's diagnostic or management error.

Click a left item, then click its matching right item

Items

A physician recently treated several cases of viral gastroenteritis and subsequently diagnoses a new patient with similar symptoms as having a viral infection, missing early acute appendicitis.
A hospitalist receives a patient from the emergency department with a preliminary diagnosis of 'heart failure exacerbation' and continues aggressive diuresis despite the patient developing a fever and purulent sputum.
A clinician firmly suspects a patient has systemic lupus erythematosus and heavily weights mildly positive antinuclear antibodies, while disregarding normal complement levels and an absence of other clinical criteria.
A resident hands off a patient by describing them as a 'difficult, anxious patient with a history of panic attacks,' leading the oncoming night team to inadequately evaluate the patient's new-onset tachycardia and hypotension.

Matches

Show answer & explanation

Answer

The recent cluster of gastroenteritis cases matches the Availability heuristic; sticking rigidly to the initial emergency department diagnosis matches Anchoring bias; selectively weighting supportive laboratory data matches Confirmation bias; and the subjective handoff description altering clinical perception matches the Framing effect.
Each scenario describes a distinct cognitive bias. The availability heuristic is demonstrated when recent memorable cases (gastroenteritis) skew the clinician's estimate of a new diagnosis. Anchoring bias occurs when a clinician relies too heavily on an initial piece of information (heart failure diagnosis) and fails to adjust despite new, conflicting data. Confirmation bias is seen when a clinician selectively focuses on data (mildly positive ANA) that supports their favored diagnosis while ignoring contradictory findings. The framing effect occurs when the subjective presentation of a case ('anxious patient') alters the subsequent clinician's objective reasoning and decision-making.

Step-by-Step Solution

1
Evaluate the first scenario focusing on the physician's recent clinical exposure.
Identifies the availability heuristic.
Recalling recent, memorable events inappropriately biases the perceived probability of a current diagnosis.
2
Evaluate the second scenario focusing on the reliance on the initial diagnostic label.
Identifies anchoring bias.
The physician failed to adjust their differential diagnosis when new information emerged, staying anchored to the initial piece of information.
3
Evaluate the third scenario focusing on the selective interpretation of laboratory data.
Identifies confirmation bias.
The clinician sought out and overvalued data supporting their preexisting hypothesis while ignoring contradictory evidence.
4
Evaluate the fourth scenario focusing on how the patient was presented during handoff.
Identifies the framing effect.
The subjective wording used during the handoff negatively framed the patient, directly influencing the receiving clinician's objective reasoning.

Key Concept

Human Factors and Cognitive Biases
Question 995Question →

A 42-year-old man presents to the primary care clinic for a follow-up visit regarding elevated blood pressure. Over the past three months, his blood pressure measurements have consistently ranged from 145/92 mmHg to 152/96 mmHg despite strict lifestyle modifications. His past medical history is significant for asthma, which is well-controlled with an as-needed albuterol inhaler. The physician decides to initiate pharmacologic antihypertensive therapy. Which of the following medications should be avoided in this patient due to the risk of exacerbating his underlying respiratory condition?

Show answer & explanation

Answer: Propranolol

Answer

Propranolol should be avoided because it is a non-selective beta-blocker that can trigger bronchospasm in asthmatic patients.
The correct answer is the non-selective beta-blocker. Non-selective beta-blockers inhibit both beta-1 receptors (primarily in the heart) and beta-2 receptors (found in bronchial smooth muscle). Blockade of beta-2 receptors leads to bronchoconstriction and increased airway resistance, which can precipitate a severe or even fatal asthma exacerbation in susceptible individuals. Therefore, they are explicitly contraindicated in patients with a history of asthma.

Step-by-Step Solution

1
Identify the patient's concurrent medical conditions.
The patient has a history of asthma.
Concurrent conditions often dictate which medications are safe or contraindicated.
2
Evaluate the mechanism of action of the proposed antihypertensive medications.
Propranolol is a non-selective beta-blocker, meaning it antagonizes both beta-1 and beta-2 receptors.
Understanding the mechanism of action helps identify potential adverse effects on other organ systems.
3
Determine the effect of the medication on the patient's concurrent condition.
Blockade of beta-2 receptors in the lungs by non-selective beta-blockers leads to bronchoconstriction, which can precipitate an asthma exacerbation.
This establishes the absolute contraindication for using non-selective beta-blockers in asthmatic patients.

Key Concept

Non-selective beta-blockers are contraindicated in patients with asthma due to the risk of inducing bronchoconstriction via beta-2 receptor blockade.
Question 996Question →

A 48-year-old woman undergoes a percutaneous liver biopsy to evaluate persistently abnormal liver biochemistries. Over the past year, she has experienced worsening fatigue and generalized pruritus. Her medical history is notable only for hypothyroidism managed with levothyroxine. Laboratory evaluation shows an alkaline phosphatase of 410 U/L, aspartate aminotransferase of 55 U/L, and alanine aminotransferase of 62 U/L. Total bilirubin is 1.0 mg/dL. An abdominal ultrasound demonstrates a homogeneous liver echotexture with no intrahepatic or extrahepatic biliary dilatation. The liver biopsy specimen reveals expanded portal tracts with a dense lymphoplasmacytic infiltrate and scattered eosinophils. The inflammatory cells are centered around small interlobular bile ducts, demonstrating epithelial cell swelling, vacuolization, and disruption of the ductal basement membrane. Several poorly formed, noncaseating granulomas are intimately associated with these damaged ducts. The surrounding hepatic lobules are largely preserved. Based on these histopathologic findings, which of the following is the most definitive diagnosis?

Show answer & explanation

Answer: Primary biliary cholangitis

Answer

The most definitive diagnosis is Primary biliary cholangitis.
The biopsy describes the classic 'florid duct lesion,' which is the pathognomonic histopathologic hallmark of primary biliary cholangitis. This lesion is characterized by a focal, heavy lymphoplasmacytic and frequently granulomatous inflammatory infiltrate that specifically targets and destroys the small interlobular bile ducts. This tissue diagnosis perfectly aligns with the patient's demographic profile (middle-aged woman), cholestatic liver enzyme pattern (disproportionately elevated alkaline phosphatase), and symptoms of fatigue and pruritus.

Step-by-Step Solution

1
Analyze the patient's clinical presentation and laboratory profile.
A middle-aged woman presents with fatigue, pruritus, and a prominent cholestatic pattern of liver injury (disproportionately elevated alkaline phosphatase with normal imaging).
This specific clinical pattern localizes the pathology to an intrahepatic cholestatic process, narrowing the differential diagnosis significantly.
2
Interpret the specific histopathologic findings from the liver biopsy.
The biopsy shows a portal lymphoplasmacytic infiltrate with poorly formed noncaseating granulomas that are selectively targeting and destroying small interlobular bile ducts.
Identifying the specific anatomical target of the inflammation (the interlobular ducts) and the nature of the damage (granulomatous destruction) is the critical step in establishing the diagnosis.
3
Synthesize the clinical and histologic data to reach a definitive diagnosis.
The finding of granulomatous destruction of small interlobular bile ducts is known as the 'florid duct lesion,' which confirms the diagnosis of primary biliary cholangitis.
This classic histopathologic lesion rules out other causes of portal inflammation and granulomas that lack this highly specific, targeted biliary destruction.

Key Concept

The histopathologic hallmark of primary biliary cholangitis is the 'florid duct lesion,' characterized by a dense lymphoplasmacytic infiltrate and noncaseating granulomas that specifically target and destroy small interlobular bile ducts.
Question 997Question →

A 74-year-old woman is brought to the clinic by her son for a progressive decline in her memory over the past 12 months. The son notes that she frequently repeats questions, forgets recently discussed topics, and recently became disoriented while walking in her own neighborhood. She previously managed her own finances but now struggles to pay bills on time. She has a history of essential hypertension, osteoarthritis, and occasional urinary incontinence over the past 2 years. Her current medications include lisinopril and acetaminophen. Vital signs are Temp 36.8°C (98.2°F), BP 132/82 mmHg, HR 72/min, and RR 14/min. Neurological examination shows normal cranial nerves, normal motor strength and sensation, and a normal, steady gait. She scores 21/30 on the Montreal Cognitive Assessment (MoCA), losing points primarily on delayed recall, orientation, and visuospatial tasks. Which of the following are indicated as the most appropriate concurrent steps in the initial diagnostic workup of this patient? (Select 2)

Select all that apply

Show answer & explanation

Answer: Serum vitamin B12 and thyroid-stimulating hormone assays; Noncontrast magnetic resonance imaging of the brain

Answer

The most appropriate concurrent steps are serum vitamin B12 and thyroid-stimulating hormone assays, along with noncontrast magnetic resonance imaging of the brain.
The correct sequence for evaluating progressive cognitive decline begins with a thorough clinical assessment, followed concurrently by laboratory testing to rule out reversible metabolic causes (such as hypothyroidism and vitamin B12 deficiency) and structural neuroimaging (such as an MRI of the brain) to rule out vascular disease, tumors, or hydrocephalus. The patient presents with a classic insidious onset of memory loss and functional decline, making this standard initial evaluation the most appropriate next step.

Step-by-Step Solution

1
Identify the primary clinical syndrome.
The patient has progressive cognitive decline affecting memory, orientation, and executive function, indicative of a major neurocognitive disorder (dementia).
Establishing the clinical syndrome directs the subsequent diagnostic workup.
2
Evaluate for red flags or atypical features.
The presentation is consistent with typical Alzheimer disease. Although she has urinary incontinence, her normal gait significantly lowers the probability of normal pressure hydrocephalus (NPH).
Atypical features might alter the sequence of testing, but their absence supports a standard diagnostic pathway.
3
Select the guideline-recommended initial diagnostic tests.
Standard guidelines require screening for reversible causes (vitamin B12, TSH) and structural neuroimaging (MRI or CT) to rule out covert cerebrovascular disease or masses.
These tests form the mandatory baseline workup for any patient presenting with new-onset, progressive dementia.

Key Concept

The initial evaluation of a patient with suspected dementia requires ruling out reversible systemic causes with basic laboratory tests (B12, TSH) and ruling out structural intracranial pathology with neuroimaging (MRI or CT).
Estimated Time:1m 30s
Question 998Question →

A 65-year-old man is evaluated in the emergency department for sudden-onset right-sided pleuritic chest pain, dyspnea, and a mild dry cough that began 4 hours ago. He has a history of type 2 diabetes mellitus, hypertension, and chronic kidney disease. His current medications include lisinopril, amlodipine, and insulin glargine.

Vital signs are:
Temperature: 37.2°C (99.0°F)
Pulse: 112/min
Blood pressure: 135/85 mm Hg
Respiratory rate: 24/min
Oxygen saturation: 91% on room air

Physical examination reveals decreased breath sounds and dullness to percussion at the right lung base. Cardiovascular examination reveals tachycardia with a regular rhythm and no murmurs. The lower extremities exhibit trace bilateral pitting edema without localized swelling, erythema, or calf tenderness.

Laboratory studies show a serum creatinine of 2.9 mg/dL (baseline 2.7 mg/dL), with an estimated glomerular filtration rate (eGFR) of 22 mL/min/1.73 m222 \text{ mL/min/1.73 m}^2.

Chest radiography reveals a moderate right-sided pleural effusion and an area of consolidation in the right lower lobe. An electrocardiogram demonstrates sinus tachycardia. The physician maintains a high clinical suspicion for an acute pulmonary embolism.

Which of the following is the most appropriate next step in imaging?

Show answer & explanation

Answer: Bilateral lower extremity compression ultrasonography

Answer

The most appropriate next step in imaging is bilateral lower extremity compression ultrasonography.
The correct response is bilateral lower extremity compression ultrasonography. This patient has a high clinical probability of an acute pulmonary embolism (PE). The gold-standard initial imaging test is computed tomography pulmonary angiography (CTPA). However, CTPA requires intravenous iodinated contrast, which is strongly avoided in patients with severe chronic kidney disease (eGFR < 30) due to the high risk of contrast-induced nephropathy. The standard alternative for patients who cannot receive contrast is a ventilation-perfusion (V/Q) scan. A critical limitation of the V/Q scan is that it requires a normal or near-normal chest radiograph. This patient's chest X-ray demonstrates a moderate pleural effusion and lower lobe consolidation. These abnormalities will cause matched ventilation and perfusion defects, rendering the V/Q scan indeterminate and diagnostically useless. When both CTPA and V/Q scans are contraindicated or expected to be non-diagnostic, bilateral lower extremity compression ultrasonography is the safest and most appropriate next step. Approximately 30-50% of patients with PE will have a detectable deep vein thrombosis (DVT) on ultrasound, even without classic leg symptoms. Identifying a DVT secures the diagnosis of venous thromboembolism (VTE) and provides a definitive indication for anticoagulation, effectively eliminating the need for complex or harmful chest imaging.

Step-by-Step Solution

1
Assess the pre-test probability and standard imaging modality for the suspected diagnosis.
The patient's presentation (tachycardia, pleuritic chest pain, dyspnea) makes pulmonary embolism (PE) highly likely, which typically warrants computed tomography pulmonary angiography (CTPA).
Establishing the clinical likelihood determines the need for definitive vascular imaging.
2
Evaluate patient-specific contraindications for standard imaging.
CTPA is strongly relatively contraindicated due to the patient's severe chronic kidney disease (eGFR of 22 mL/min).
Intravenous iodinated contrast poses a high risk of contrast-induced nephropathy in severe renal impairment.
3
Identify the standard alternative imaging modality and assess its diagnostic feasibility.
Ventilation-perfusion (V/Q) scanning is the standard non-contrast alternative, but the patient's abnormal chest X-ray (consolidation and effusion) will likely render the V/Q scan non-diagnostic.
V/Q scans require a relatively clear radiograph to accurately interpret perfusion mismatches; matched defects from consolidations result in indeterminate findings.
4
Select the safest alternative diagnostic pathway to confirm venous thromboembolism.
Bilateral lower extremity compression ultrasonography should be performed, even without localized leg symptoms.
A positive ultrasound confirms deep vein thrombosis, providing a definitive indication for therapeutic anticoagulation and safely bypassing the need for contrast or radiation.

Key Concept

In hemodynamically stable patients with suspected pulmonary embolism who have contraindications to CTPA (e.g., severe CKD) and an abnormal chest X-ray (which renders a V/Q scan non-diagnostic), bilateral lower extremity compression ultrasonography is the preferred initial imaging step to confirm venous thromboembolism.
Estimated Time:2m 0s
Question 999Question →

A 72-year-old man is transferred to the intensive care unit with septic shock secondary to a severe intra-abdominal infection. Blood cultures have been drawn and broad-spectrum antimicrobial therapy has been initiated. However, his mean arterial pressure remains below 65 mmHg, and he exhibits signs of poor tissue perfusion. The clinical team proceeds to manage his hemodynamic instability according to standard sepsis resuscitation guidelines. Arrange the following pharmacologic interventions in the correct sequential order of escalation for the treatment of his persistent hypotension.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence of escalation is: 1) intravenous crystalloids, 2) intravenous norepinephrine, 3) intravenous vasopressin, and 4) intravenous hydrocortisone.
Hemodynamic stabilization in septic shock follows a standardized protocol. The foundation of treatment is restoring intravascular volume with a rapid bolus of intravenous crystalloids. If target perfusion is not met, the first-line vasopressor, norepinephrine, is initiated. For patients who require escalating doses of norepinephrine, a second vasopressor, typically vasopressin, is added to augment blood pressure and spare catecholamine toxicity. Finally, if the patient remains hypotensive despite adequate fluids and vasopressors, intravenous hydrocortisone is administered to treat suspected critical illness-related corticosteroid insufficiency.

Step-by-Step Solution

1
Identify the primary intervention for volume depletion and hypotension in sepsis.
Intravenous crystalloids.
Sepsis causes widespread vasodilation and capillary leak. Filling the intravascular space with fluids is the mandatory first step before initiating vasoactive agents.
2
Determine the first-line vasopressor for fluid-refractory shock.
Intravenous norepinephrine continuous infusion.
If the mean arterial pressure remains <65 mmHg after initial fluid boluses, norepinephrine is the preferred initial vasopressor due to its potent alpha-1 adrenergic effects.
3
Determine the adjunctive vasopressor for escalating support.
Intravenous vasopressin continuous infusion.
When norepinephrine alone is insufficient, adding vasopressin can help achieve the target blood pressure without increasing the toxicity of high-dose catecholamines.
4
Identify the intervention for vasopressor-refractory shock.
Intravenous hydrocortisone.
In cases of refractory septic shock, relative adrenal insufficiency is often present, making hydrocortisone the final pharmacologic step in the standard hemodynamic escalation pathway.

Key Concept

The hemodynamic escalation protocol for septic shock progresses sequentially from fluid resuscitation (crystalloids) to a first-line vasopressor (norepinephrine), followed by an adjunctive vasopressor (vasopressin), and finally corticosteroids (hydrocortisone) for refractory shock.
Question 1000Question →

A 7676-year-old woman is brought to the emergency department from a skilled nursing facility due to severe, diffuse abdominal pain that began abruptly 44 hours ago. She has a medical history of paroxysmal atrial fibrillation, heart failure with preserved ejection fraction, and hypertension. Current medications include metoprolol and lisinopril; she stopped taking apixaban three weeks ago due to financial constraints. On examination, the patient is distressed and diaphoretic. Temperature is 37.4∘C37.4^\circ\text{C} (99.3∘F99.3^\circ\text{F}), blood pressure is 105/65105/65 mmHg, pulse is 118118/min and irregularly irregular, and respirations are 2222/min. Abdominal examination reveals mild, diffuse tenderness to deep palpation without rebound or guarding, which appears disproportionately mild compared to her reported pain severity. Laboratory studies show a leukocyte count of 16,500/mm316,500/\text{mm}^3 and a serum lactate level of 5.25.2 mmol/L. A contrast-enhanced CT scan of the abdomen and pelvis is performed. The radiologist notes segmental mural hypoenhancement and wall thinning involving the distal jejunum and proximal ileum. Additionally, there are distinct, linear, branching areas of low attenuation (gas density) extending predominantly into the peripheral subcapsular regions of the liver. Which of the following is the most accurate interpretation of the hepatic imaging findings in the context of this patient's presentation?

Show answer & explanation

Answer: Accumulation of gas within the portal venous system due to transmural bowel infarction

Answer

The imaging findings represent the accumulation of gas within the portal venous system due to transmural bowel infarction.
The patient's clinical presentation (atrial fibrillation off anticoagulation, pain out of proportion to exam, high lactate) points strongly to acute mesenteric ischemia. The CT finding of branching gas extending to the peripheral subcapsular regions of the liver is the classic description of portal venous gas. When the bowel wall undergoes transmural infarction, mucosal gas traverses the compromised wall into the mesenteric venous system and travels to the liver via the portal vein. The flow of portal blood pushes this gas to the far periphery of the hepatic parenchyma.

Step-by-Step Solution

1
Analyze the clinical presentation.
The patient has sudden-onset abdominal pain out of proportion to exam findings, an irregularly irregular rhythm (atrial fibrillation) off anticoagulation, and an elevated lactate (5.25.2 mmol/L).
These findings are highly characteristic of acute mesenteric ischemia, likely due to a superior mesenteric artery embolus.
2
Evaluate the intestinal imaging findings.
Segmental mural hypoenhancement and wall thinning in the jejunum and ileum are identified.
These findings confirm a lack of blood flow and structural compromise (infarction) of the small bowel wall.
3
Interpret the hepatic imaging findings and correlate with the pathophysiology.
Linear, branching gas extending to the peripheral subcapsular regions of the liver is identified.
When transmural bowel infarction occurs, mucosal integrity is lost, allowing luminal gas to enter the mesenteric venous system. This gas is carried to the portal vein and is pushed into the extreme periphery of the liver by the direction of portal venous blood flow. This distinguishes it from biliary gas (pneumobilia), which remains central.

Key Concept

On abdominal CT, portal venous gas appears as branching radiolucencies extending to the periphery of the liver (within 22 cm of the capsule), whereas pneumobilia presents as centrally located gas. In the setting of acute mesenteric ischemia, portal venous gas is an ominous sign indicating transmural bowel infarction.
Estimated Time:1m 30s
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