Internal Medicine

3151 questions

Question 221Question →

A 6868-year-old man with a history of severe chronic obstructive pulmonary disease (COPD) and chronic cor pulmonale is brought to the emergency department due to profound weakness and increasing shortness of breath over the past 22 days. His wife reports that he has had 55 to 66 large-volume watery stools daily for the past 44 days. He is alert and oriented but in visible respiratory distress, utilizing accessory muscles of respiration.

Vital signs:
- Temperature: 37.2∘C37.2^\circ\text{C} (99.0∘F99.0^\circ\text{F})
- Blood pressure: 105/65 mm Hg105/65\text{ mm Hg}
- Heart rate: 112/min112/\text{min}
- Respiratory rate: 28/min28/\text{min}
- Oxygen saturation: 89%89\% on room air

Physical examination reveals a jugular venous pressure of 5 cm5\text{ cm} above the sternal angle. Pulmonary auscultation demonstrates prolonged expiration and diffuse bilateral wheezing, but no crackles are appreciated. Cardiac examination shows a normal S1S_1 and S2S_2 with a loud P2P_2.

Laboratory evaluation reveals the following:
TestResult
Sodium134 mEq/L134\text{ mEq/L}
Potassium3.1 mEq/L3.1\text{ mEq/L}
Chloride111 mEq/L111\text{ mEq/L}
Bicarbonate14 mEq/L14\text{ mEq/L}
Blood urea nitrogen42 mg/dL42\text{ mg/dL}
Creatinine1.6 mg/dL1.6\text{ mg/dL}
Arterial blood gas analysis on room air:
ParameterResult
pH7.187.18
PaO2PaO_260 mm Hg60\text{ mm Hg}
PaCO2PaCO_238 mm Hg38\text{ mm Hg}

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

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Answer: Initiate noninvasive positive pressure ventilation

Answer

Initiate noninvasive positive pressure ventilation
The correct action is to initiate noninvasive positive pressure ventilation (NIPPV). This patient presents with profound acidemia (pH 7.187.18). Interpretation of his labs reveals a normal anion gap metabolic acidosis (NAGMA) secondary to massive diarrhea (Anion Gap = 134−111−14=9134 - 111 - 14 = 9). To evaluate if his respiratory compensation is adequate, Winter's formula must be applied: Expected PaCO2=(1.5×14)+8=29 mm HgPaCO_2 = (1.5 \times 14) + 8 = 29\text{ mm Hg} (range 27−3127-31). His actual PaCO2PaCO_2 is 38 mm Hg38\text{ mm Hg}. Because his actual PaCO2PaCO_2 is higher than the expected compensated range, he has a concomitant respiratory acidosis. This occurs because his underlying severe COPD and respiratory muscle fatigue prevent him from increasing his minute ventilation sufficiently. He is in impending respiratory arrest and requires immediate ventilatory assistance. NIPPV is the first-line intervention for alert patients with COPD exacerbation and hypercapnic respiratory failure, as it offloads the work of breathing and improves alveolar ventilation without the risks of endotracheal intubation.

Step-by-Step Solution

1
Analyze the arterial blood gas to determine the primary acid-base disturbance.
The pH of 7.187.18 indicates severe acidemia, and the low HCO3−HCO_3^- of 14 mEq/L14\text{ mEq/L} identifies a primary metabolic acidosis.
Establishing the primary disturbance is the necessary first step in acid-base interpretation.
2
Calculate the anion gap to determine the etiology of the metabolic acidosis.
Anion gap = 134−(111+14)=9 mEq/L134 - (111 + 14) = 9\text{ mEq/L}, which is normal.
A normal anion gap metabolic acidosis (hyperchloremic) points toward gastrointestinal bicarbonate loss from his reported diarrhea.
3
Apply Winter's formula to assess for adequate respiratory compensation.
Expected PaCO2=1.5×14+8=29 mm HgPaCO_2 = 1.5 \times 14 + 8 = 29\text{ mm Hg} (range 27−3127-31). The patient's actual PaCO2PaCO_2 is 38 mm Hg38\text{ mm Hg}.
Because the actual PaCO2PaCO_2 is significantly higher than expected, a concurrent respiratory acidosis is present. Even though 38 mm Hg38\text{ mm Hg} is typically 'normal', it is dangerously elevated for this degree of metabolic acidosis.
4
Determine the most appropriate immediate intervention based on the clinical status.
The patient is fatiguing and in mixed acid-base failure; noninvasive positive pressure ventilation (NIPPV) should be initiated.
NIPPV provides ventilatory support, decreases the work of breathing, and is the preferred first-line therapy for alert COPD patients in acute hypercapnic respiratory failure.

Key Concept

Patients with severe COPD who develop a primary metabolic acidosis can experience secondary respiratory failure due to an inability to mount the required compensatory hyperventilation, necessitating immediate mechanical ventilatory support (such as NIPPV).
Question 222Question →

A 6262-year-old male with a history of pulmonary tuberculosis treated 1515 years ago is brought to the emergency department for massive hemoptysis. He reports coughing up approximately 800 mL800\text{ mL} of bright red blood over the past two hours. He is visibly anxious, diaphoretic, and in respiratory distress. Vital signs are temperature 37.1∘C37.1^\circ\text{C}, blood pressure 88/54 mmHg88/54\text{ mmHg}, heart rate 126/min126/\text{min}, respiratory rate 30/min30/\text{min}, and oxygen saturation 85%85\% on room air. Auscultation reveals loud, coarse crackles and diminished breath sounds isolated to the right lung fields; the left lung fields are clear. A chest radiograph from two months ago documented a large, thick-walled cavitary lesion in the right upper lobe. Arrange the following management steps in the most appropriate chronological sequence for this patient.

Drag items to arrange them in the correct order

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Answer

The correct sequence is to first place the patient in the right lateral decubitus position, followed by securing the airway with a large-bore endotracheal tube, then performing bronchoscopy to localize the bleeding, and finally proceeding with bronchial artery embolization.
The management of massive hemoptysis (>600 mL>600\text{ mL} in 2424 hours or causing hemodynamic/respiratory compromise) requires a highly orchestrated sequence to prevent death from asphyxiation. First, the patient must immediately be placed with the bleeding lung down (right lateral decubitus in this patient with right-sided pathology) to protect the dependent healthy lung while intubation equipment is gathered. Second, the airway is secured with a large-bore endotracheal tube (≥8.0 mm\geq 8.0\text{ mm}) to ensure adequate ventilation and accommodate instrumentation. Third, bronchoscopy is performed through the tube to clear life-threatening clots and apply topical therapies (e.g., balloon tamponade) for temporary stability. Finally, once stable, the patient is transferred for bronchial artery embolization, the definitive therapy for bleeding originating from the hypertrophied bronchial circulation (typical of old tuberculosis).

Step-by-Step Solution

1
Identify the primary source of bleeding and the immediate life threat.
The history of a right upper lobe cavity combined with isolated right-sided crackles localizes the bleeding to the right lung. The primary cause of death in massive hemoptysis is asphyxiation, not exsanguination.
Accurate localization dictates the immediate mechanical interventions required to protect the unaffected lung.
2
Position the patient utilizing gravity.
The patient is placed in the right lateral decubitus position (bleeding side down).
This physical maneuver can be performed instantaneously while airway equipment is being prepared, preventing blood from spilling into and drowning the healthy left lung.
3
Establish a definitive airway.
Endotracheal intubation is performed using a large-bore single-lumen tube.
Airway protection is critical given the hypoxia and altered respiratory mechanics. A large-bore tube is mandatory to allow the subsequent passage of a therapeutic bronchoscope.
4
Visualize and temporize the bleeding.
Bronchoscopy (often rigid) is performed through the endotracheal tube.
This clears obstructing clots, confirms the anatomic origin of the hemorrhage, and allows for local hemostatic measures (e.g., cold saline, balloon tamponade) to stabilize the patient for transport.
5
Provide definitive hemorrhage control.
The patient undergoes bronchial artery embolization in the interventional radiology suite.
Bronchial artery embolization is the first-line definitive treatment for massive hemoptysis, which overwhelmingly originates from the high-pressure bronchial circulation, especially in the setting of old tuberculosis or aspergillomas.

Key Concept

In the management of massive hemoptysis, immediate positioning with the bleeding lung dependent precedes or occurs simultaneously with endotracheal intubation to protect the healthy lung from asphyxiation, followed by bronchoscopic stabilization and definitive bronchial artery embolization.
Question 223Question →

Match each acute cardiovascular clinical presentation with its most characteristic pulmonary artery catheterization (hemodynamic) profile.

Click a left item, then click its matching right item

Items

A patient presenting with hypotension, elevated jugular venous pressure, clear lung fields, and ST-segment elevation in leads II, III, and aVF.
A patient developing sudden-onset severe respiratory distress, hypotension, and a new harsh holosystolic murmur at the cardiac apex three days after an inferior myocardial infarction.
A patient with end-stage renal disease presenting with hypotension, tachycardia, distant heart sounds, and a >10>10 mmHg drop in systolic blood pressure during inspiration.
A patient with a large untreated traumatic arteriovenous fistula in the lower extremity presenting with progressive dyspnea, bounding peripheral pulses, and a widened pulse pressure.

Matches

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Answer

The correct matches pair acute right ventricular infarction with isolated right-sided pressure elevation; papillary muscle rupture with giant v-waves on PCWP tracing; cardiac tamponade with equalization of diastolic pressures; and an arteriovenous fistula with high-output/low-resistance hemodynamics.
Each pair correctly matches the pathophysiology of the condition to its Swan-Ganz catheterization profile. RV infarction impairs right-sided output, raising RAP but starving the left heart (low PCWP). Papillary muscle rupture creates an acute volume load on the left atrium, dramatically raising PCWP with systolic v-waves. Tamponade exerts uniform external pressure, equalizing RAP and PCWP. AV fistulas create a low-resistance parallel circuit, dropping SVR and forcing a hyperdynamic increased Cardiac Index.

Step-by-Step Solution

1
Diagnose the underlying cardiovascular emergency for each clinical vignette.
Identified Acute RV Infarction, Papillary Muscle Rupture, Cardiac Tamponade, and High-Output Heart Failure.
Accurate clinical diagnosis is required before predicting the resulting hemodynamic derangements.
2
Determine the primary effect on systemic vascular resistance (SVR) and cardiac index (CI) for each condition.
The AV fistula is the only condition that lowers SVR and increases CI (distributive/high-output pattern). The other three represent cardiogenic or obstructive shock, characterized by decreased CI and reflexively increased SVR.
Isolating the high-output state immediately pairs the AV fistula vignette with the high CI / low SVR profile.
3
Analyze right- and left-sided filling pressures to differentiate the remaining three cardiogenic/obstructive shock states.
RV infarction shows isolated right-sided elevation (high RAP, low PCWP). Tamponade shows equalized elevation of both sides (high RAP = high PCWP). Papillary muscle rupture shows prominent left-sided failure (massive PCWP elevation with v-waves).
Filling pressures reflect the specific anatomical location of the cardiac dysfunction or extrinsic compression.

Key Concept

Hemodynamic profiling of shock and acute heart failure states using pulmonary artery catheterization.
Estimated Time:2m 0s
Question 224Question →

A 68-year-old woman is evaluated in the hospital on day 3 of admission for acute cholangitis. She initially presented with fever, right upper quadrant pain, and jaundice. She was started on empiric intravenous piperacillin-tazobactam and successfully underwent endoscopic retrograde cholangiopancreatography with biliary stone extraction.

Currently, she is afebrile and her abdominal pain has entirely resolved. Blood and bile cultures obtained on admission both grow *Klebsiella pneumoniae*. The antimicrobial susceptibility report is as follows:

AntimicrobialSusceptibility
AmpicillinResistant
CeftriaxoneSusceptible
CiprofloxacinSusceptible
MeropenemSusceptible
Piperacillin-tazobactamSusceptible

Which of the following is the most appropriate next step in the patient's pharmacotherapy?

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Answer: Transition to intravenous ceftriaxone

Answer

Transition to intravenous ceftriaxone.
Ceftriaxone is the most appropriate choice because it provides targeted, narrow-spectrum coverage against the susceptible *Klebsiella pneumoniae* isolate. Antimicrobial stewardship guidelines strongly recommend de-escalating from broad-spectrum empiric therapy (like piperacillin-tazobactam) to a narrower-spectrum agent once culture and susceptibility data become available and the patient is clinically stable.

Step-by-Step Solution

1
Assess the patient's clinical status and review the finalized culture and susceptibility testing.
The patient is clinically stable, and cultures show *Klebsiella pneumoniae* susceptible to multiple agents, including narrow-spectrum options.
Clinical improvement indicates it is safe to transition from empiric broad-spectrum therapy to targeted therapy.
2
Select the most narrow-spectrum, effective antimicrobial agent based on the susceptibility profile.
Ceftriaxone is chosen over the broader piperacillin-tazobactam and meropenem.
Antimicrobial stewardship dictates de-escalating to the narrowest effective agent to prevent the development of multidrug-resistant organisms.

Key Concept

Antimicrobial stewardship and de-escalation of empiric antibiotics based on culture results.
Estimated Time:1m 0s
Question 225Question →

A 71-year-old man is evaluated in the emergency department for a 3-day history of progressively worsening shortness of breath, increased cough, and a change in sputum color from clear to yellow-green. He has a 45-pack-year smoking history and severe chronic obstructive pulmonary disease (COPD). Temperature is 37.4∘C37.4^\circ\text{C} (99.3∘F99.3^\circ\text{F}), heart rate is 105/min105/\text{min}, respiratory rate is 24/min24/\text{min}, and blood pressure is 135/85 mmHg135/85\text{ mmHg}. Pulse oximetry shows an SpO2SpO_2 of 88%88\% on room air.

Physical examination shows a patient sitting forward and using accessory muscles of respiration. Jugular venous pulsation is visible at 10 cm H2O10\text{ cm H}_2\text{O}. Chest examination reveals a barrel-shaped chest, hyperresonance to percussion, and diffuse expiratory wheezing with a prolonged expiratory phase. Cardiac examination reveals distant heart sounds with a prominent P2P_2, but no S3S_3 gallop. There is 2+2+ bilateral pitting edema of the lower extremities.

Arterial blood gas on room air shows:
pH: 7.307.30
pCO2pCO_2: 62 mmHg62\text{ mmHg}
pO2pO_2: 55 mmHg55\text{ mmHg}
HCO3−HCO_3^-: 30 mEq/L30\text{ mEq/L}

Chest radiograph demonstrates hyperinflated lung fields, flattened diaphragms, enlarged central pulmonary arteries, and a narrow cardiac silhouette, with no focal consolidations or pleural effusions.

Based on the clinical presentation and diagnostic findings, which of the following are the most appropriate immediate interventions for this patient? (Select all that apply)

Select all that apply

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Answer: Systemic glucocorticoids; Inhaled short-acting bronchodilators

Answer

The correct interventions are systemic glucocorticoids and inhaled short-acting bronchodilators.
This patient is experiencing a severe acute exacerbation of COPD (AECOPD), characterized by the three cardinal symptoms: increased dyspnea, increased sputum volume, and increased sputum purulence. Immediate management consists of supplemental oxygen (targeting saturations of 88-92% to avoid worsening hypercapnia), inhaled short-acting bronchodilators (such as albuterol and ipratropium) to reverse acute bronchoconstriction, and systemic glucocorticoids (oral or intravenous) to reduce airway inflammation and speed recovery. Antibiotics are also indicated due to the presence of purulent sputum, but they should generally be narrow-spectrum.

Step-by-Step Solution

1
Analyze the clinical presentation and vital signs.
The patient has cardinal symptoms of an acute exacerbation of COPD (AECOPD): worsening dyspnea, increased cough, and increased sputum purulence.
Identifying the primary clinical syndrome drives immediate management priorities.
2
Interpret the physical exam and imaging findings.
The elevated JVP, prominent P2, and peripheral edema in the setting of hyperinflated, clear lungs indicate chronic right heart failure (cor pulmonale) secondary to COPD, rather than acute decompensated left heart failure.
Differentiating cor pulmonale from left-sided heart failure prevents inappropriate administration of diuretics.
3
Evaluate the arterial blood gas.
The ABG shows an acute-on-chronic respiratory acidosis (low pH, high pCO2, and elevated HCO3- indicating chronic metabolic compensation) alongside hypoxemia.
Understanding the acid-base derangement confirms the etiology of respiratory failure and guides oxygen/ventilatory therapy.
4
Select evidence-based therapies for AECOPD.
Initial management includes supplemental oxygen (target 88-92%), short-acting inhaled bronchodilators, systemic glucocorticoids, and targeted oral antibiotics.
These interventions are proven to decrease mortality, reduce length of stay, and improve lung function in severe exacerbations.

Key Concept

Management of Acute Exacerbations of COPD (AECOPD) and differentiation from acute decompensated heart failure.
Question 226Question →

A 68-year-old man comes to the emergency department due to a 2-day history of worsening shortness of breath, cough, and increased production of thick, yellow sputum. He has a 40-pack-year smoking history and was diagnosed with chronic obstructive pulmonary disease (COPD) 5 years ago. His temperature is 37.4°C (99.3°F), blood pressure is 140/88 mm Hg, pulse is 95/min, and respiratory rate is 24/min. Pulse oximetry shows an oxygen saturation of 86% on room air. Physical examination reveals a barrel-shaped chest, diffuse bilateral wheezing, and a prolonged expiratory phase. There is no jugular venous distention, crackles, or lower extremity edema. Which of the following are appropriate initial management steps for this patient? (Select all that apply)

Select all that apply

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Answer: Administration of inhaled short-acting bronchodilators and systemic glucocorticoids; Administration of an oral macrolide antibiotic

Answer

The correct interventions are the administration of inhaled short-acting bronchodilators with systemic glucocorticoids, and the administration of an oral macrolide antibiotic.
The correct initial management for an acute COPD exacerbation includes supplemental oxygen (to target saturation of 88-92%), inhaled short-acting bronchodilators, and systemic glucocorticoids to relieve bronchospasm and reduce airway inflammation. Additionally, because this patient presents with all three cardinal symptoms (increased dyspnea, increased sputum volume, and increased sputum purulence), a narrow-spectrum antibiotic such as an oral macrolide is indicated to treat potential bacterial triggers.

Step-by-Step Solution

1
Identify the primary diagnosis based on the clinical presentation.
The patient has an acute exacerbation of chronic obstructive pulmonary disease (COPD).
The patient has a significant smoking history, known COPD, and presents with worsening dyspnea, cough, increased sputum volume, and purulence, along with wheezing on examination.
2
Determine the necessary core pharmacological interventions for the primary diagnosis.
The standard treatment bundle includes bronchodilators, systemic glucocorticoids, and appropriate antibiotics.
Short-acting bronchodilators and systemic steroids treat acute airway inflammation and bronchospasm. Antibiotics are required because the patient exhibits all three cardinal symptoms of a bacterial exacerbation (dyspnea, sputum volume, sputum purulence).
3
Select the appropriate class of antibiotics.
A narrow-spectrum oral agent, such as a macrolide, is chosen.
Broad-spectrum antibiotics are not indicated without specific risk factors for resistant or hospital-acquired organisms.
4
Exclude treatments for alternative diagnoses.
Exclude diuretics and sodium bicarbonate.
There are no signs of heart failure to warrant furosemide, and bicarbonate is not a treatment for respiratory acidosis.

Key Concept

Management of acute chronic obstructive pulmonary disease (COPD) exacerbations
Question 227Question →

During morning rounds, the care team reviews the chart of a 71-year-old woman who is currently receiving inpatient treatment for acute ascending cholangitis. She was admitted three days ago with a temperature of 39.2°C (102.6°F), severe right upper quadrant pain, and scleral icterus. On the day of admission, blood cultures were drawn, and she was started on empiric intravenous piperacillin-tazobactam. The following day, she underwent an urgent endoscopic retrograde cholangiopancreatography (ERCP), during which a 12-mm common bile duct stone was successfully extracted, restoring normal biliary flow. Today, the patient reports feeling significantly better and is tolerating a liquid diet. Her vital signs are a temperature of 37.0°C (98.6°F), blood pressure of 122/76 mm Hg, and pulse of 78/min. Laboratory studies show her leukocyte count has normalized to 7,500/mm³. The microbiology laboratory reports that the admission blood cultures are positive for *Escherichia coli*. The susceptibility panel confirms the isolate is resistant to ampicillin but highly susceptible to ceftriaxone, ciprofloxacin, and piperacillin-tazobactam. Which of the following is the most appropriate next step in the pharmacologic management of this patient?

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Answer: Transition to intravenous ceftriaxone

Answer

Transition to intravenous ceftriaxone
The correct action is to transition to intravenous ceftriaxone. This patient presented with acute ascending cholangitis and appropriately received broad-spectrum empiric therapy (piperacillin-tazobactam) along with definitive source control (ERCP with stone extraction). Once clinical improvement is noted and definitive culture and susceptibility data become available, a core principle of antimicrobial stewardship is to de-escalate to the most targeted, narrow-spectrum agent that is effective against the isolated organism. Because the blood cultures grew *E. coli* that is highly susceptible to ceftriaxone, continuing the broader piperacillin-tazobactam is unnecessary and inappropriate. Targeted therapy provides excellent efficacy while minimizing the risk of multidrug-resistant organism colonization.

Step-by-Step Solution

1
Evaluate the patient's current clinical status and interventions.
The patient is afebrile, hemodynamically stable, and has achieved definitive source control via ERCP.
Establishing clinical stability confirms that the current treatment trajectory is successful and safe for modification.
2
Analyze the microbiology and susceptibility data.
Blood cultures isolate E. coli that is susceptible to ceftriaxone, a narrower-spectrum agent than the empiric piperacillin-tazobactam.
Objective culture data provides the foundation for transitioning from empiric to targeted therapy.
3
Apply the principles of antimicrobial stewardship.
Piperacillin-tazobactam is discontinued in favor of ceftriaxone.
De-escalating to the narrowest effective agent minimizes the risk of resistance and secondary infections like Clostridioides difficile.

Key Concept

Antimicrobial Stewardship: De-escalation of antibiotics in acute cholangitis following source control and culture susceptibility results.
Question 228Question →

A 64-year-old man presents to his primary care physician complaining of a two-week history of progressively worsening shortness of breath. Initially, he only felt breathless when walking up an incline, but now he experiences it while walking on level ground. He also reports a new, dry cough that occurs mainly at night, which has prompted him to sleep in a recliner chair for the past three nights. His medical history includes essential hypertension and a 35-pack-year smoking history. His temperature is 37.0°C (98.6°F), blood pressure is 158/92 mm Hg, pulse is 88/min, and respiratory rate is 20/min. Physical examination reveals distention of the jugular veins while the patient is sitting at a 45-degree angle. Auscultation of the lungs demonstrates fine crackles at both lung bases that do not clear with coughing. Cardiac examination reveals a regular rate and rhythm with an extra, low-frequency heart sound occurring shortly after S2. Trace pitting edema is noted in both ankles.

Which of the following is the most likely underlying mechanism for this patient's clinical presentation?

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Answer: Increased pulmonary venous hydrostatic pressure

Answer

Increased pulmonary venous hydrostatic pressure
This patient's presentation of exertional dyspnea, orthopnea (needing to sleep in a recliner), jugular venous distention, bibasilar crackles, and a third heart sound (S3 gallop) is pathognomonic for acute decompensated heart failure. An S3 is a low-frequency sound occurring in early diastole caused by rapid filling into a volume-overloaded left ventricle. The primary pathophysiologic mechanism driving this patient's pulmonary symptoms is backward failure from the left heart. Elevated left ventricular end-diastolic pressure causes an increase in left atrial pressure, which subsequently increases pulmonary venous hydrostatic pressure. This high hydrostatic pressure forces fluid out of the pulmonary capillaries into the interstitium and alveoli, resulting in the fine basilar crackles of cardiogenic pulmonary edema.

Step-by-Step Solution

1
Analyze the patient's key symptoms: exertional dyspnea, orthopnea (sleeping in a recliner), and nocturnal cough.
These symptoms are classic for paroxysmal nocturnal dyspnea and orthopnea, which strongly suggest fluid shifting into the lungs when supine.
Identifying the clinical syndrome is the first step in determining the etiology.
2
Evaluate the physical examination findings: JVD, bibasilar crackles, an extra low-frequency sound after S2 (S3 gallop), and pitting edema.
These signs confirm a volume-overloaded state consistent with acute decompensated heart failure (ADHF).
An S3 gallop is highly specific for heart failure due to rapid ventricular filling into a non-compliant or overfilled left ventricle.
3
Link the clinical diagnosis of ADHF to its primary pathophysiologic mechanism.
Left ventricular dysfunction leads to elevated left-sided filling pressures, which are transmitted backward to the pulmonary veins.
The backward transmission of pressure raises the hydrostatic pressure in the pulmonary capillaries, causing fluid to leak into the interstitium and alveoli (cardiogenic pulmonary edema).

Key Concept

Cardiogenic pulmonary edema in acute decompensated heart failure is caused by increased left ventricular end-diastolic pressure that translates backward, resulting in increased pulmonary venous hydrostatic pressure.
Question 229Question →

A medical student is reviewing small bowel biopsy pathology reports for several patients presenting with chronic diarrhea, weight loss, and signs of malabsorption. Match each clinical diagnosis with its hallmark histologic finding on small intestinal biopsy.

Click a left item, then click its matching right item

Items

Celiac disease
Whipple disease
Abetalipoproteinemia
Eosinophilic gastroenteritis

Matches

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Answer

Celiac disease matches with villous blunting; Whipple disease matches with PAS-positive macrophages; Abetalipoproteinemia matches with lipid-laden enterocytes; Eosinophilic gastroenteritis matches with dense eosinophilic infiltration.
Accurate diagnosis of chronic diarrhea and malabsorption relies heavily on endoscopic biopsy. Each of these four conditions presents with distinct and defining histopathological features that guide targeted therapy.

Step-by-Step Solution

1
Analyze the histologic finding for Celiac disease.
Identified as villous blunting, crypt hyperplasia, and increased intraepithelial lymphocytes.
Gluten induces an inflammatory response leading to these classic mucosal changes.
2
Analyze the histologic finding for Whipple disease.
Identified as foamy macrophages containing PAS-positive, diastase-resistant granules.
These granules represent partially digested T. whipplei bacteria within macrophages.
3
Analyze the histologic finding for Abetalipoproteinemia.
Identified as normal villous architecture with lipid-laden enterocytes at the villus tips.
Defective chylomicron assembly traps absorbed lipids within the mucosal cells.
4
Analyze the histologic finding for Eosinophilic gastroenteritis.
Identified as dense infiltration of the mucosa and submucosa by eosinophils.
The disease is defined by eosinophilic tissue infiltration, often linked to allergic responses.

Key Concept

Histopathologic diagnosis of malabsorptive syndromes
Question 230Question →

A 4141-year-old woman with a history of cystic fibrosis presents to the emergency department after coughing up large volumes of bright red blood. She estimates expectorating over 600600 mL of blood since this morning. On arrival, she is in severe respiratory distress, coughing persistently, and unable to speak in full sentences.

Vital signs:
Temperature: 37.4∘C37.4^\circ\text{C} (99.3∘F99.3^\circ\text{F})
Blood pressure: 100/60100/60 mmHg
Heart rate: 118118/min
Respiratory rate: 3030/min
Oxygen saturation: 86%86\% on room air

A bedside chest radiograph demonstrates extensive bronchiectasis, predominantly in the right upper and middle lobes, with new dense alveolar opacities in the left lower lobe.

Arrange the following interventions in the correct sequential order of management, from the immediate life-saving stabilization step to the definitive last-resort therapy.

Drag items to arrange them in the correct order

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Answer

The correct sequential order for managing massive hemoptysis is: 1) Endotracheal intubation with a large-bore tube, 2) Bronchoscopic evaluation and topical intervention, 3) Bronchial artery embolization via interventional radiology, and 4) Surgical pulmonary resection.
The algorithmic approach to massive hemoptysis (defined as >600>600 mL of expectorated blood in 24 hours, or a rate posing an immediate threat to life) mandates that airway protection is the paramount initial step. Because the anatomic dead space is only about 150150 mL, even a relatively small volume of blood can rapidly flood the bronchial tree, causing sudden death by asphyxiation. Therefore, endotracheal intubation with a large-bore tube (to accommodate a bronchoscope) is the first required intervention. Once the airway is secure and the patient is stabilized, bronchoscopy is performed to identify the bleeding lobe, clear clots from the unaffected lung, and potentially achieve temporary hemostasis using balloon tamponade or topical vasoconstrictors. After the site is identified and temporarily stabilized, the patient is taken for bronchial artery embolization (BAE) by interventional radiology, which is the most effective and least invasive definitive treatment. Surgical resection carries a high mortality risk in the acute setting and is strictly reserved for cases where BAE is technically impossible, fails to control the bleeding, or is contraindicated.

Step-by-Step Solution

1
Assess airway, breathing, and circulation to identify the immediate threat to life.
Recognize life-threatening massive hemoptysis with impending respiratory failure due to airway flooding, indicated by hypoxemia (86%86\% SpO2) and new infiltrates in the contralateral lung.
Asphyxiation, not exsanguination, is the most common cause of death in massive hemoptysis.
2
Perform immediate airway protection.
Endotracheal intubation with a large-bore tube.
Protects the healthy lung from further aspiration of blood, allows for mechanical ventilation to correct hypoxemia, and provides a conduit for therapeutic bronchoscopy.
3
Localize the bleeding site and achieve temporary hemostasis.
Bronchoscopic evaluation and topical intervention.
Identifies the exact lobar source of bleeding and allows for temporary stabilizing measures (e.g., balloon tamponade) before definitive treatment.
4
Proceed to definitive hemostatic therapy.
Bronchial artery embolization, reserving surgical pulmonary resection only if embolization fails.
Bronchial artery embolization is highly effective and carries significantly lower morbidity and mortality compared to emergent surgical resection.

Key Concept

The acute management algorithm for massive hemoptysis strictly prioritizes airway protection (intubation) to prevent asphyxiation, followed by source identification (bronchoscopy), and ultimately minimally invasive definitive hemostasis (bronchial artery embolization), with surgery reserved as an absolute last resort.
Question 231Question →

A 74-year-old man presents to the emergency department at 3:00 AM with sudden-onset, severe shortness of breath and wheezing. He has a 45-pack-year smoking history, essential hypertension, and diet-controlled type 2 diabetes mellitus. He reports waking up gasping for air and states that his cough produces frothy sputum. Current medications include amlodipine and metformin. His temperature is 37.0°C (98.6°F), blood pressure is 210/115 mm Hg, pulse is 112/min, and respirations are 28/min. Pulse oximetry shows 88% on room air. Physical examination reveals use of accessory muscles of respiration. Lung auscultation demonstrates diffuse, bilateral end-expiratory wheezes with a prolonged expiratory phase. Cardiac examination reveals a sustained but non-displaced apical impulse and a prominent fourth heart sound (S4). Jugular venous pressure is estimated at 10 cm H2O. There is no lower extremity edema. A chest radiograph reveals peribronchial cuffing, indistinct pulmonary vascular margins, and a normal cardiothoracic ratio. An electrocardiogram demonstrates normal sinus rhythm with voltage criteria for left ventricular hypertrophy. Which of the following pathophysiologic mechanisms is the primary driver of this patient's current respiratory distress?

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Answer: Decreased left ventricular diastolic compliance

Answer

Decreased left ventricular diastolic compliance
This patient is presenting with acute flash pulmonary edema, manifesting clinically as 'cardiac asthma' (wheezing secondary to peribronchial edema compressing the airways). While his smoking history makes COPD a consideration, his extreme hypertension, prominent S4 gallop, normal cardiothoracic ratio, and interstitial edema (peribronchial cuffing) on radiograph strongly indicate cardiogenic pulmonary edema due to Heart Failure with Preserved Ejection Fraction (HFpEF). The primary pathophysiologic driver of HFpEF is decreased left ventricular diastolic compliance (a stiff ventricle). When blood pressure spikes, the non-compliant ventricle requires exceedingly high filling pressures, which rapidly transmit backward into the left atrium and pulmonary venous system, resulting in acute pulmonary edema.

Step-by-Step Solution

1
Analyze the patient's presentation and vital signs.
The patient presents with sudden-onset nocturnal dyspnea, wheezing, frothy sputum, extreme hypertension (210/115 mm Hg), and hypoxia.
To establish the acuity of the presentation and identify the primary physiologic derangements.
2
Evaluate the physical examination and diagnostic findings.
Exam shows an S4 gallop, non-displaced apical impulse, and wheezing. CXR shows peribronchial cuffing and a normal heart size. ECG shows left ventricular hypertrophy.
To differentiate between cardiac and pulmonary etiologies of wheezing and dyspnea.
3
Synthesize the data to form a clinical diagnosis.
The findings indicate acute cardiogenic pulmonary edema (flash pulmonary edema) secondary to a hypertensive emergency. The wheezing is 'cardiac asthma' caused by peribronchial interstitial edema.
Despite the smoking history, the extreme blood pressure, S4, and CXR findings confirm a cardiac source rather than a primary COPD exacerbation.
4
Identify the subtype and mechanism of the heart failure.
The normal heart size and S4 point to Heart Failure with Preserved Ejection Fraction (HFpEF), which is driven by decreased left ventricular diastolic compliance.
Concentric left ventricular hypertrophy creates a stiff ventricle that requires high filling pressures, leading to rapid fluid backup into the lungs during acute hypertensive episodes.

Key Concept

Heart Failure with Preserved Ejection Fraction (HFpEF) / Cardiac Asthma
Question 232Question →

A 28-year-old woman presents to an urgent care center with a two-day history of progressive shortness of breath, chest tightness, and a dry cough. Her symptoms began shortly after she adopted a cat. She was diagnosed with asthma in childhood but has not required daily medications for the past five years. Over the last 48 hours, she has used her short-acting albuterol inhaler up to six times daily with minimal relief. Her temperature is 37.1°C (98.8°F), blood pressure is 122/78 mmHg, pulse is 112/min, and respiratory rate is 24/min. Pulse oximetry shows an oxygen saturation of 93% on room air. Physical examination reveals a prolonged expiratory phase with diffuse bilateral wheezing. There is no jugular venous distention, and heart sounds are normal without murmurs or gallops. Which of the following is the most appropriate next step in pharmacologic management?

Show answer & explanation

Answer: Administration of systemic corticosteroids

Answer

Administration of systemic corticosteroids
This patient is presenting with an acute asthma exacerbation directly triggered by recent exposure to an environmental allergen (cat dander). Her lack of clinical improvement despite frequent use of a short-acting beta-agonist indicates a moderate-to-severe exacerbation. In such cases, the standard of care dictates the addition of systemic corticosteroids (such as oral prednisone). Corticosteroids address the underlying severe airway inflammation, accelerate symptom resolution, and significantly decrease the risk of treatment failure or relapse. She does not have signs of volume overload or an infectious etiology, making alternative treatments inappropriate.

Step-by-Step Solution

1
Identify the primary diagnosis based on the clinical presentation.
The patient is experiencing an acute asthma exacerbation triggered by an environmental allergen (cat dander).
She has a history of asthma, recent exposure to a known trigger, tachypnea, and diffuse expiratory wheezing.
2
Determine the severity and the patient's response to initial home therapy.
The exacerbation is moderate to severe, as evidenced by the lack of improvement despite using a short-acting beta-agonist frequently over 48 hours.
Repeated use of an albuterol inhaler without symptom resolution indicates significant underlying airway inflammation that requires escalation of therapy.
3
Select the most appropriate pharmacological intervention for this severity.
Systemic corticosteroids (e.g., oral prednisone) are indicated.
Systemic corticosteroids effectively reduce severe airway inflammation, accelerate symptom resolution, and decrease the risk of a relapse.

Key Concept

The management of an acute asthma exacerbation that is unresponsive to initial short-acting beta-agonist therapy requires the prompt administration of systemic corticosteroids.
Question 233Question →

A 7474-year-old woman is brought to the emergency department by her daughter due to sudden, severe abdominal pain that started 22 hours ago. The patient reports the pain is constant, diffuse, and poorly localized. She has a history of type 2 diabetes mellitus, hypertension, and a previous transient ischemic attack. She was diagnosed with atrial fibrillation one year ago but stopped taking her prescribed apixaban three months ago due to financial constraints. Her temperature is 37.2∘C37.2^\circ\text{C} (99.0∘F99.0^\circ\text{F}), pulse is 112/min112/\text{min} and irregularly irregular, blood pressure is 142/88 mm Hg142/88 \text{ mm Hg}, and respirations are 20/min20/\text{min}. Physical examination shows a patient in significant distress, writhing on the stretcher. However, abdominal palpation elicits only mild, diffuse tenderness without rigidity, guarding, or rebound tenderness. Bowel sounds are hypoactive. Stool is negative for occult blood. Laboratory studies show a leukocyte count of 16,500/mm316,500/\text{mm}^3 and a serum lactate of 4.2 mmol/L4.2 \text{ mmol/L}.

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

Show answer & explanation

Answer: Computed tomography angiography of the abdomen

Answer

Computed tomography angiography of the abdomen
This patient presents with sudden, severe abdominal pain that is out of proportion to her physical examination findings. Combined with her history of atrial fibrillation without current anticoagulation, an elevated leukocyte count, and elevated serum lactate, this presentation is highly suspicious for acute mesenteric ischemia (AMI) due to an arterial embolus. The embolus most commonly lodges in the superior mesenteric artery. The initial management of suspected AMI dictates that patients with unequivocal signs of peritonitis (e.g., rigidity, rebound tenderness) or hemodynamic collapse proceed directly to emergent exploratory laparotomy. However, because this patient has a soft abdomen without peritoneal signs, there is no immediate indication for surgery. Therefore, the most appropriate next step is computed tomography (CT) angiography of the abdomen. This imaging modality rapidly confirms the diagnosis, pinpoints the vascular occlusion, and helps the surgical team decide between open embolectomy versus endovascular revascularization.

Step-by-Step Solution

1
Analyze the patient's acute clinical presentation and risk factors.
The patient has sudden, severe abdominal pain out of proportion to physical exam findings, an elevated lactate, and untreated atrial fibrillation.
This combination of findings strongly points to acute mesenteric ischemia caused by a thromboembolism to the superior mesenteric artery.
2
Evaluate the physical examination for acute surgical indications.
The abdomen is soft without rigidity, guarding, or rebound tenderness.
The absence of peritonitis indicates that transmural bowel infarction and perforation have likely not yet occurred, meaning the patient does not require immediate, unguided exploratory surgery.
3
Determine the optimal diagnostic modality.
Computed tomography angiography of the abdomen should be ordered.
Before exposing a hemodynamically stable patient without peritonitis to the high morbidity of a laparotomy, rapid vascular imaging is required to definitively diagnose the occlusion and guide whether open surgical embolectomy or endovascular revascularization is needed.

Key Concept

The initial management of suspected acute mesenteric ischemia depends on the presence or absence of peritonitis. Patients lacking peritoneal signs require immediate CT angiography to confirm the diagnosis prior to intervention.

Alternative Method

In patients with severe iodine allergy or severe chronic kidney disease who absolutely cannot receive IV contrast for CT angiography, magnetic resonance angiography (MRA) may be considered. However, MRA is generally avoided in the acute setting due to longer acquisition times and inferior resolution of distal mesenteric branches compared to CTA.
Estimated Time:1m 30s
Question 234Question →

A 1919-year-old male college student presents to the student health clinic complaining of a severely painful throat, subjective fevers, and profound exhaustion that has progressively worsened over the past 77 days. He notes that he has been too tired to attend his classes. He has no chronic medical conditions and takes no daily medications. Vital signs show a temperature of 38.4∘C38.4^\circ\text{C} (101.1∘F101.1^\circ\text{F}), blood pressure of 115/72 mm Hg115/72\text{ mm Hg}, pulse of 92/min92/\text{min}, and respirations of 14/min14/\text{min}. Physical examination demonstrates marked bilateral posterior cervical lymphadenopathy, erythematous tonsils with grayish-white exudates, and mild splenomegaly. A point-of-care heterophile antibody test yields a positive result. Which of the following is the most appropriate management for this patient?

Show answer & explanation

Answer: Recommend rest, hydration, and nonsteroidal anti-inflammatory drugs

Answer

Recommend rest, hydration, and nonsteroidal anti-inflammatory drugs
The patient's presentation of fever, pharyngitis, posterior cervical lymphadenopathy, splenomegaly, and a positive heterophile antibody test confirms the diagnosis of infectious mononucleosis caused by the Epstein-Barr virus. Management of uncomplicated mononucleosis is strictly supportive. Patients should be advised to rest, maintain adequate hydration, and use over-the-counter analgesics/antipyretics such as nonsteroidal anti-inflammatory drugs (NSAIDs) for symptom control. Additionally, they should be counseled to avoid contact sports for at least 3-4 weeks to prevent splenic rupture.

Step-by-Step Solution

1
Analyze the clinical presentation and physical exam findings.
The patient presents with a classic triad of fever, tonsillar pharyngitis, and profound fatigue, alongside posterior cervical lymphadenopathy and splenomegaly.
Identifying these classic symptoms strongly points toward infectious mononucleosis rather than a bacterial pharyngitis (which typically presents with anterior cervical lymphadenopathy and no splenomegaly).
2
Interpret the diagnostic testing.
The heterophile antibody test (Monospot test) is positive.
A positive heterophile antibody test in the appropriate clinical context confirms the diagnosis of Epstein-Barr virus (EBV) infection.
3
Determine the most appropriate management based on the confirmed diagnosis.
Supportive care with rest, hydration, and NSAIDs is selected.
Because EBV is a viral illness, antimicrobial therapy is ineffective and inappropriate. Prescribing antibiotics violates stewardship principles and exposes the patient to adverse effects.

Key Concept

The management of uncomplicated infectious mononucleosis is supportive; antibiotics must be avoided to adhere to stewardship principles and prevent adverse reactions such as ampicillin-induced rash.
Question 235Question →

A 6060-year-old woman is brought to the emergency department by her husband due to progressive confusion, profound fatigue, and generalized weakness over the past week. Two weeks ago, she had a mild upper respiratory infection. Her husband notes she has been complaining of intermittent headaches and peripheral vision loss for the last three months. Her temperature is 36.2∘C36.2^\circ\text{C} (97.2∘F97.2^\circ\text{F}), blood pressure is 82/50 mm Hg82/50\text{ mm Hg}, pulse is 54/min54/\text{min}, and respirations are 16/min16/\text{min}. Physical examination shows a lethargic woman with dry, pale skin and delayed relaxation of deep tendon reflexes. Mild bilateral non-pitting lower extremity edema is present. Lung auscultation reveals decreased breath sounds at the bases but no crackles or wheezes.

Laboratory evaluation shows:

ParameterValue
Sodium128 mEq/L128\text{ mEq/L}
Potassium4.2 mEq/L4.2\text{ mEq/L}
Chloride98 mEq/L98\text{ mEq/L}
Bicarbonate20 mEq/L20\text{ mEq/L}
Blood urea nitrogen24 mg/dL24\text{ mg/dL}
Creatinine1.1 mg/dL1.1\text{ mg/dL}
pH7.327.32
PaCO2\text{PaCO}_238 mm Hg38\text{ mm Hg}
PaO2\text{PaO}_285 mm Hg85\text{ mm Hg}
Thyroid-stimulating hormone (TSH)0.8 \muU/mL0.8\text{ \mu U/mL} (Normal: 0.4−4.0 \muU/mL0.4-4.0\text{ \mu U/mL})
Free thyroxine (T4\text{T}_4)0.3 ng/dL0.3\text{ ng/dL} (Normal: 0.9−1.7 ng/dL0.9-1.7\text{ ng/dL})

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

Show answer & explanation

Answer: Administration of intravenous hydrocortisone

Answer

Administration of intravenous hydrocortisone
This patient's presentation of headaches, peripheral vision loss, profound fatigue, bradycardia, and non-pitting edema is highly suspicious for a pituitary macroadenoma causing panhypopituitarism. The laboratory findings of a low free T4\text{T}_4 coupled with an inappropriately normal TSH confirm central (secondary) hypothyroidism. The patient is currently presenting with hemodynamic collapse (hypotension, altered mental status) and hyponatremia, triggered by the physiological stress of a recent viral infection. This is the classic presentation of an acute adrenal crisis due to secondary adrenal insufficiency (ACTH deficiency). Notably, in secondary adrenal insufficiency, aldosterone production is preserved via the renin-angiotensin-aldosterone system, which is why her serum potassium level is normal despite the severe hyponatremia (caused by loss of cortisol's suppressive effect on ADH). In cases of suspected adrenal crisis, immediate administration of intravenous glucocorticoids (such as hydrocortisone) is life-saving and is the most critical next step. Glucocorticoids must always be replaced before thyroid hormone.

Step-by-Step Solution

1
Evaluate the clinical presentation for underlying etiology.
The combination of headaches, peripheral vision loss (bitemporal hemianopsia), and signs of hypothyroidism suggests a pituitary macroadenoma.
Mass effect from a pituitary tumor commonly compresses the optic chiasm and disrupts normal anterior pituitary hormone secretion.
2
Interpret the thyroid function tests.
The free T4\text{T}_4 is low while the TSH is inappropriately normal, indicating central (secondary) hypothyroidism.
In primary hypothyroidism, the TSH would be significantly elevated. A normal or low TSH in the presence of low T4\text{T}_4 implies pituitary or hypothalamic failure.
3
Analyze the acute hemodynamic collapse.
The patient is experiencing hypotension, altered mental status, and hyponatremia triggered by a recent infection, representing an acute adrenal crisis.
A pituitary mass causing central hypothyroidism likely also causes secondary adrenal insufficiency (ACTH deficiency), which decompensates under physiological stress.
4
Determine the safest and most critical initial treatment.
Intravenous hydrocortisone must be administered immediately.
Glucocorticoids must be replaced before thyroid hormone, because thyroid hormone increases the metabolic clearance of cortisol and can precipitate a fatal adrenal crisis if given alone.

Key Concept

In patients with suspected panhypopituitarism presenting in acute decompensation, immediate intravenous glucocorticoid replacement is required to treat secondary adrenal crisis before initiating thyroid hormone replacement.
Question 236Question →

A 62-year-old man is evaluated in the hospital on hospital day 3. He was initially admitted for fever, chills, and a warm, swollen right calf. On admission, his temperature was 39.1 C (102.4 F), blood pressure was 105/65 mm Hg, and pulse was 110/min. He was started on empiric intravenous vancomycin and piperacillin-tazobactam. Today, his temperature is 37.4 C (99.3 F), blood pressure is 120/75 mm Hg, and pulse is 82/min. The erythema on his right calf has significantly decreased. Blood cultures drawn on admission are positive for Staphylococcus aureus in 2 of 2 bottles. Susceptibility testing shows the isolate is resistant to penicillin but susceptible to oxacillin, cefazolin, and vancomycin. The patient has no history of medication allergies. Which of the following is the most appropriate next step in management?

Show answer & explanation

Answer: Switch to intravenous cefazolin

Answer

Switch to intravenous cefazolin
The patient has methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia. For MSSA bacteremia, targeted beta-lactams such as first-generation cephalosporins (e.g., cefazolin) or anti-staphylococcal penicillins (e.g., nafcillin, oxacillin) are the treatments of choice. They have been consistently shown to be superior to vancomycin for MSSA infections, resulting in faster bacterial clearance, lower rates of clinical failure, and reduced mortality. Because the isolate is susceptible and the patient has no beta-lactam allergies, de-escalating to cefazolin is the most appropriate next step.

Step-by-Step Solution

1
Analyze the blood culture and susceptibility results.
The pathogen is identified as methicillin-susceptible Staphylococcus aureus (MSSA) because it is susceptible to oxacillin and cefazolin.
Identifying the specific susceptibility pattern is required to transition from empiric to targeted, definitive therapy.
2
Evaluate the patient's current empiric antibiotic regimen against the culture data.
The current regimen of vancomycin and piperacillin-tazobactam is overly broad and suboptimal for MSSA.
Vancomycin covers MRSA but is inferior to beta-lactams for MSSA. Piperacillin-tazobactam covers Pseudomonas and anaerobes, which are not present in this patient's cultures.
3
Select the most appropriate definitive therapy based on antimicrobial stewardship principles.
Intravenous cefazolin should be initiated.
Cefazolin (or an anti-staphylococcal penicillin like nafcillin) provides targeted, narrow-spectrum coverage and has proven superiority over vancomycin for MSSA bacteremia.

Key Concept

Methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia should be treated with a narrow-spectrum beta-lactam (e.g., cefazolin, nafcillin, or oxacillin) rather than vancomycin due to superior clinical outcomes.
Question 237Question →

Match each classic clinical presentation of an infectious disease with its most appropriate first-line pharmacotherapy.

Click a left item, then click its matching right item

Items

A 26-year-old man with a painless, indurated genital ulcer and non-tender inguinal lymphadenopathy
A 32-year-old woman with an expanding, targetoid erythematous rash on her leg following a tick bite
A 12-year-old boy with acute onset of fever, tonsillar exudates, and tender anterior cervical adenopathy without a cough
A 19-year-old athlete with a painful, fluctuant, purulent skin abscess on his leg requiring drainage

Matches

Show answer & explanation

Answer

The presentations map to their respective first-line therapies: primary syphilis with benzathine penicillin G, early Lyme disease with doxycycline, streptococcal pharyngitis with amoxicillin, and community-acquired MRSA with trimethoprim-sulfamethoxazole.
Each clinical vignette provides pathognomonic or highly specific features for a common infection, which precisely corresponds to a well-established, guideline-directed first-line antimicrobial agent.

Step-by-Step Solution

1
Diagnose the infectious disease described in each clinical vignette based on classic signs and symptoms.
The vignettes sequentially describe primary syphilis, early localized Lyme disease, group A streptococcal pharyngitis, and a community-acquired MRSA skin abscess.
Accurate clinical pattern recognition is the necessary first step before selecting empiric antimicrobial therapy.
2
Identify the guideline-recommended, first-line antimicrobial agent for each diagnosed condition.
Primary syphilis requires benzathine penicillin G; Lyme disease requires doxycycline; Streptococcal pharyngitis requires amoxicillin; CA-MRSA requires trimethoprim-sulfamethoxazole.
Using targeted, first-line therapy ensures clinical efficacy while adhering to antimicrobial stewardship principles by avoiding unnecessarily broad coverage.

Key Concept

Empiric antimicrobial selection for common outpatient infectious diseases based on classic clinical presentations.
Question 238Question →

Match each patient's clinical presentation with the most likely corresponding urinalysis sediment finding.

Click a left item, then click its matching right item

Items

A 62-year-old man who develops acute kidney injury 48 hours after prolonged hypotension during an emergency abdominal aortic aneurysm repair.
A 24-year-old woman with recent onset of a malar rash, photosensitivity, and new hematuria with mild renal insufficiency.
A 45-year-old man presenting with severe generalized edema, a serum albumin of 2.1 g/dL, and a 24-hour urine protein excretion of 5.2 g.
A 58-year-old woman presenting with high fever, right-sided costovertebral angle tenderness, dysuria, and acute kidney injury.
A 72-year-old man with longstanding, poorly controlled hypertension and diabetes mellitus, presenting with small, echogenic kidneys on ultrasound.

Matches

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Answer

The correct matches pair acute tubular necrosis with muddy brown casts, glomerulonephritis with red blood cell casts, nephrotic syndrome with fatty casts, acute pyelonephritis with white blood cell casts, and advanced chronic kidney disease with broad waxy casts.
Each clinical vignette presents classic hallmark features for a distinct renal pathology. The underlying mechanism of injury directly dictates the type of cells or substances that precipitate within the renal tubules to form casts: necrotic epithelial cells (ATN), red blood cells (glomerulonephritis), lipids (nephrotic syndrome), neutrophils (pyelonephritis), or degenerate proteins in dilated tubules (advanced CKD).

Step-by-Step Solution

1
Analyze the first patient's presentation involving hypotension and surgery.
Identify ischemia-induced acute tubular necrosis (ATN).
ATN is the most common cause of intrinsic acute kidney injury following severe hypoperfusion.
2
Evaluate the second patient's systemic symptoms and hematuria.
Identify acute glomerulonephritis, likely secondary to systemic lupus erythematosus.
Glomerular inflammation leads to the passage of red blood cells through the damaged basement membrane.
3
Assess the third patient's severe edema, hypoalbuminemia, and massive proteinuria.
Identify nephrotic syndrome.
Proteinuria greater than 3.5 g/day defines nephrotic syndrome, which profoundly alters lipid metabolism.
4
Examine the fourth patient's fever and costovertebral angle tenderness.
Identify acute pyelonephritis.
These are hallmark signs of an upper urinary tract infection involving the renal interstitium.
5
Review the fifth patient's chronic comorbidities and small kidneys on ultrasound.
Identify advanced chronic kidney disease (CKD).
Chronic irreversible scarring leads to loss of renal mass and compensatory hypertrophy of remaining tubules.

Key Concept

Urinalysis sediment and cast differentiation in renal disease
Estimated Time:2m 0s
Question 239Question →

Match each classic physical examination finding to the endocrine condition with which it is most commonly associated.

Click a left item, then click its matching right item

Items

Pretibial myxedema (non-pitting edema of the lower extremities)
Facial muscle spasm upon tapping the cheek (Chvostek sign)
Violaceous abdominal striae greater than 1 cm in width
Hyperpigmentation of the palmar creases and oral mucosa

Matches

Show answer & explanation

Answer

Pretibial myxedema pairs with Graves disease; the Chvostek sign pairs with Hypocalcemia; violaceous abdominal striae pair with Cushing syndrome; and hyperpigmentation pairs with Primary adrenal insufficiency.
Each physical finding is highly specific to its respective endocrine disorder's underlying pathophysiology. Pretibial myxedema is a localized autoimmune phenomenon unique to Graves disease. The Chvostek sign reflects the classic neuromuscular excitability seen in hypocalcemia. Violaceous striae arise from hypercortisolism-induced catabolism in Cushing syndrome. Diffuse hyperpigmentation is a direct result of elevated ACTH/MSH seen specifically in primary adrenal insufficiency.

Step-by-Step Solution

1
Analyze the dermatologic finding of pretibial myxedema.
Identify it as a unique autoimmune manifestation.
It is mediated by TSH receptor antibodies stimulating dermal fibroblasts, uniquely linking it to Graves disease.
2
Evaluate the neuromuscular finding (Chvostek sign).
Identify it as a sign of membrane instability.
Low extracellular calcium directly increases the resting membrane potential of nerves, causing twitching upon mechanical stimulation.
3
Assess the origin of wide, violaceous striae.
Identify it as a sign of connective tissue breakdown.
Excess glucocorticoids (Cushing syndrome) weaken collagen and cause skin thinning, exposing underlying vascular beds.
4
Determine the cause of mucosal and palmar hyperpigmentation.
Identify it as a sign of elevated pro-opiomelanocortin (POMC) cleavage products.
Primary adrenal insufficiency lacks cortisol, resulting in high ACTH and MSH levels that stimulate melanocytes.

Key Concept

Classic physical examination findings and their associated endocrine disorders.
Question 240Question →

Match each highly specific clinical scenario to the most appropriate guideline-directed pharmacotherapy, taking into account patient-specific contraindications.

Click a left item, then click its matching right item

Items

A 24-year-old pregnant woman (10 weeks gestation) presents with a 4-day history of fever, severe headache, myalgias, and a petechial rash that began on her wrists and ankles. She recently camped in a wooded area of North Carolina.
A 32-year-old pregnant woman (10 weeks gestation) presents with an expanding targetoid rash on her back and a unilateral facial nerve palsy. She has no meningeal signs or electrocardiographic abnormalities.
A 65-year-old man develops ventilator-associated pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA). He has a documented history of severe, anaphylactic allergy to vancomycin.
A 55-year-old man with acute myeloid leukemia and profound neutropenia develops persistent fever and a new pulmonary nodule with a surrounding ground-glass halo on chest computed tomography.
A 40-year-old man with advanced HIV and a severe sulfa allergy presents with fever, dry cough, and bilateral interstitial infiltrates. Arterial blood gas shows a PaO2 of 62 mmHg on room air.

Matches

Show answer & explanation

Answer

Vignette 1 matches Oral doxycycline; Vignette 2 matches Oral amoxicillin; Vignette 3 matches Intravenous linezolid; Vignette 4 matches Intravenous voriconazole; Vignette 5 matches Intravenous pentamidine plus corticosteroids.
Each clinical scenario presents a specific infectious disease paired with unique constraints requiring highly targeted therapy. RMSF in pregnancy must still be treated with doxycycline due to disease lethality. Lyme disease in pregnancy with isolated facial palsy allows for the safe alternative of amoxicillin. MRSA pneumonia in a vancomycin-allergic patient necessitates linezolid. Invasive aspergillosis in neutropenia requires voriconazole. Severe PCP with a sulfa allergy requires alternative coverage (pentamidine) alongside vital corticosteroids.

Step-by-Step Solution

1
Analyze Vignette 1: Identify Rickettsia rickettsii (RMSF) infection in a pregnant patient.
Match with Oral doxycycline.
Doxycycline is the sole exception to the tetracycline contraindication in pregnancy when treating life-threatening RMSF.
2
Analyze Vignette 2: Identify Borrelia burgdorferi (Lyme disease) with isolated facial palsy in a pregnant patient.
Match with Oral amoxicillin.
Amoxicillin is safe in pregnancy and effective for early Lyme with isolated facial palsy; doxycycline must be avoided here as safer alternatives exist.
3
Analyze Vignette 3: Identify MRSA pneumonia in a patient with a vancomycin allergy.
Match with Intravenous linezolid.
Linezolid has excellent lung penetration. Daptomycin cannot be used because it is inactivated by surfactant.
4
Analyze Vignette 4: Identify the CT halo sign in a neutropenic host as invasive pulmonary aspergillosis.
Match with Intravenous voriconazole.
Voriconazole is the first-line targeted antifungal for invasive aspergillosis.
5
Analyze Vignette 5: Identify severe Pneumocystis jirovecii pneumonia (PaO2 of 62 mmHg) in a sulfa-allergic patient.
Match with Intravenous pentamidine plus corticosteroids.
Severe PCP requires adjunctive corticosteroids to prevent inflammatory respiratory failure, and pentamidine replaces TMP-SMX in severe allergy.

Key Concept

The management of complex infectious diseases requires critical adjustment of first-line therapies based on strict patient-specific factors such as pregnancy, anaphylactic allergies, and the anatomical site of infection.
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