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Step 3 Sample Test Answers + Explanations 2026
USMLE STEP 3 Free 137 Explanations
Updated Feb 2025
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Updated as of Feb 2025
Here are the detailed explanations of the new Free 137 NBME STEP 3 Sample Test Questions so you don’t waste your time trying to find the correct answers and explanations. We had our expert USMLE tutors who scored 260+ on their exams refine these answers and explanations for you so you can spend your valuable time learning!
You can download the Free 137 STEP 3 Sample Test Questions on the USMLE website here. The order of answers and explanations here is based on the online NBME platform (not the pdf) as of February 2025.
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Table of Contents
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Block 1
Question 1:
The correct answer is B. his 75-year-old man presents with fever, pleuritic chest pain, cough producing rust-colored sputum, and consolidation in the left lower lobe, suggestive of left-sided lobar pneumonia. His symptoms worsen when he is lying on his left side, likely due to the effects of gravity on the consolidated lung. In this position, blood flow is diverted to the left lung, which has impaired oxygenation due to the consolidation, worsening the ventilation-perfusion mismatch and increasing the A-a gradient, leading to hypoxemia. When the patient is rolled to his right side, gravity helps redistribute the blood flow to the right lung, which is likely less affected by the pneumonia and is better aerated. Positional changes that favor the unaffected lung (right side in this case) can reduce the mismatch in ventilation and perfusion caused by the consolidated lung.
Incorrect answers:
A. Pulmonary embolism typically presents with sudden onset dyspnea, tachypnea, hypoxemia, and pleuritic chest pain. However, the findings of consolidation on chest x-ray, rust-colored sputum, and the gradual onset of symptoms are more indicative of pneumonia rather than a pulmonary embolism.
C. Left ventricular filling abnormalities, such as those seen in restrictive cardiomyopathy or tamponade, can cause positional symptoms, but they would not explain the focal lung findings (consolidation) or improvement with positional changes specific to pneumonia.
D. While a large pleural effusion or consolidation could restrict diaphragmatic motion, it would cause more gradual changes in breathing and wouldn’t result in the rapid improvement in symptoms seen here.
E. While pleural fluid shifts with position, the fluid doesn’t increase; it redistributes. The immediate symptom improvement suggests that the relief is due to a redistribution of blood flow, not the increase of pleural effusion. Also, the chest x-ray does not show any evidence of pleural effusion.
Question 2:
The correct answer is C. This postmenopausal woman presents with abnormal vaginal bleeding, which is concerning for endometrial hyperplasia or endometrial cancer. The first-line diagnostic step in evaluating postmenopausal bleeding is endometrial biopsy.
Endometrial biopsy is indicated in women ≥ 45 years old with postmenopausal bleeding, especially if they have risk factors for endometrial hyperplasia or cancer. These risk factors include obesity, diabetes mellitus, and unopposed estrogen exposure. Alternatively, a transvaginal ultrasound can be performed first, and if the endometrial thickness is >4 mm, an endometrial biopsy is warranted.
Incorrect answers:
A. Complete blood count: A CBC is not indicated unless there are signs of anemia or infection.
B. CT scan of the pelvis: A CT scan is not the first step in evaluating abnormal uterine bleeding; ultrasound is typically preferred.
D. Hysterosalpingography: This test evaluates tubal patency and is not indicated for postmenopausal bleeding.
E. CA 125: CA 125 is used primarily for ovarian cancer monitoring. It is not used for diagnosing endometrial cancer.
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Question 3:
The correct answer is A. This patient reports new-onset anxiety that began after a divorce from her husband of seven years. Adjustment disorder occurs within 3 months of a significant stressor, such as a divorce. It is characterized by emotional or behavioral symptoms that do not meet the criteria for another mental disorder. Anxiety is the predominant symptom here, consistent with adjustment disorder with anxiety.
Incorrect answers:
B. Agoraphobia: This involves avoidance of situations or places due to fear of panic or embarrassment, but this patient’s anxiety appears to occur unpredictably rather than in response to specific situations.
C. Dysthymic disorder: It is characterized by chronic, low-level depression lasting for at least 2 years, but this patient’s main issue is anxiety rather than mood disturbance.
D. Generalized anxiety disorder: GAD involves excessive and uncontrollable worry about various life events, which persists for at least 6 months, but this patient’s anxiety seems more episodic and linked to recent stress.
E. Posttraumatic stress disorder: PTSD involves intrusive memories, flashbacks, or hypervigilance related to trauma, which are not described in this patient’s presentation.
Question 4:
The correct answer is C. This patient with severe COPD and a do-not-resuscitate (DNR) order is requesting removal of noninvasive positive pressure ventilation (NIPPV). The appropriate next step is to clarify her goals of care and confirm that her wishes align with her documented advance directive. Since the directive appears unclear, engaging her in a detailed discussion ensures she understands the implications of her decision.
When a patient’s advance directive is unclear or does not fully address their current situation, it is essential to have a direct and empathetic discussion to clarify their goals of care and document their updated preferences. This ensures that medical interventions align with the patient’s values and wishes.
Incorrect answers:
A. This approach does not adequately address her current concerns or explore her preferences.
B. The patient is competent and can make decisions herself, so involving the family is unnecessary unless she requests it.
D. This contradicts the patient’s initial decision to decline intubation.
E. There is no evidence of impaired decision-making capacity, so this step is not warranted.
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Question 5:
The correct answer is C. When designing a clinical trial, particularly a phase 3 trial for the prevention of type 2 diabetes mellitus (T2DM), selecting participants at high risk for developing the condition ensures that the study is both efficient and clinically meaningful. Patients with hyperlipidemia and central obesity (abdominal fat distribution) represent a population with a significantly elevated risk of developing T2DM. This group is ideal for assessing the effectiveness of preventive medication, as the higher baseline risk increases the likelihood of observing a measurable effect of the intervention within the trial period.
Incorrect answers:
A. This group has a low risk of diabetes, which would make it inefficient for study purposes.
B. This population is too general and may include many individuals at low risk.
D. This group already meets diagnostic criteria for diabetes, making them unsuitable for a prevention study.
Question 6:
The correct answer is D. This patient presents with signs of right heart failure (elevated JVP, peripheral edema) and hypoxemia (oxygen saturation of 84%). The chest X-ray findings, combined with diffuse wheezing and a history of chronic obstructive pulmonary disease (COPD), suggest pulmonary hypertension secondary to chronic hypoxic lung disease (cor pulmonale).
Cor pulmonale is a condition of right ventricular failure due to pulmonary hypertension, most often caused by chronic lung diseases like COPD. Clinical findings include signs of right-sided heart failure (JVP elevation, peripheral edema, hepatomegaly) and hypoxemia. Management includes addressing the underlying cause (e.g., COPD exacerbation), optimizing oxygenation, and diuretic therapy to manage volume overload.
Incorrect answers:
A. External compression of the superior vena cava: Superior vena cava syndrome typically causes upper body venous congestion, such as facial swelling, distended neck veins, and cyanosis, without significant lower extremity edema or signs of pulmonary hypertension. These features are absent here.
B. Helicobacter pylori infection with transmural ulceration and peritoneal leaking: Although H. pylori can cause peptic ulcer disease, this does not explain the patient’s respiratory symptoms, hypoxemia, or the findings on chest X-ray. There is no evidence of abdominal pathology such as peritonitis or free air on imaging.
C. Lactic acidosis caused by systemic hypoperfusion: While lactic acidosis can occur due to systemic hypoperfusion (e.g., in sepsis or cardiogenic shock), this patient’s presentation of right-sided heart failure and pulmonary hypertension is more specific for cor pulmonale. There are no clinical or laboratory findings to support lactic acidosis.
E. Widespread hepatocellular necrosis and parenchymal edema: Hepatic injury in cor pulmonale is due to passive congestion, not widespread hepatocellular necrosis. The liver edge palpation is consistent with hepatic congestion secondary to elevated central venous pressures.
Question 7:
The correct answer is A. This patient has multiple risk factors for impaired wound healing and complications following amputation, including diabetes mellitus, peripheral vascular disease, and prior arterial bypass surgery. A 3 cm blackened eschar on the heel suggests ischemic necrosis, a sign of severe peripheral vascular disease. Poor vascular supply to the distal extremities can lead to impaired healing, infection, and potentially limb-threatening complications. This is particularly concerning in patients with diabetes, as they are predisposed to infections due to neuropathy and hyperglycemia impairing immune function.
A well-vascularized and healthy distal limb is critical for successful ambulation with a prosthesis. The presence of ischemic tissue, as indicated by the blackened eschar, highlights poor peripheral perfusion, which would significantly hinder this patient’s ability to heal and ambulate effectively with a prosthesis.
Incorrect answers:
B. A 5-degree left hip flexion contracture: While contractures can complicate prosthetic fitting, they are typically correctable through physical therapy or surgical intervention and are less likely to impair long-term ambulation compared to critical limb ischemia.
C. An irregular pulse: An irregular pulse may indicate atrial fibrillation, which is already noted in this patient’s history. However, it does not directly affect the ability to ambulate with a prosthesis.
D. Loss of proprioception in the right great toe: While proprioception loss can complicate balance and ambulation, it is less significant than the vascular complications associated with ischemia and tissue necrosis.
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Question 8:
The correct answer is A. The proposed study examines a potential association between dental x-rays and thyroid cancer. The Institutional Review Board (IRB) plays a critical role in ensuring the ethical conduct of research, particularly when human participants are involved. In this scenario, the study design includes sufficient safeguards: informed consent and federal funding requirements, which necessitate ethical oversight and adherence to regulations.
The IRB’s concern regarding “potential liability for the institution if an association is found” is not a sufficient reason to reject or modify the study. Ethical and scientific reviews must be conducted independently of liability concerns. Moreover, including liability-related language in the consent form would be inappropriate and could introduce unnecessary fear or bias in participants.
Incorrect answers:
B. Do not approve the study: This option is not appropriate because the study is ethically sound and scientifically relevant, and the IRB’s role is to ensure safety and ethics, not to preemptively limit research based on potential results.
C. Require language in the informed consent document advising participants of the right to sue should a positive association between dental x-rays and thyroid cancer be found: This is inappropriate because potential legal outcomes are not typically included in informed consent unless there is a clear risk of harm or direct injury, which is not the case here.
D. Require language in the informed consent document releasing the institution from liability: This is not necessary because such a release is unlikely to be enforceable and does not address the core ethical concern of informed consent, which is to provide participants with information about the study’s purpose, risks, and benefits, not institutional liability.
Question 9:
The correct answer is C. This patient presents with generalized pruritus, recent use of oxycodone, and no significant physical findings apart from skin excoriations. Pruritus is a well-documented side effect of opioid therapy, including oxycodone. This side effect occurs due to opioid-induced histamine release from mast cells, leading to an itch sensation. The histamine release is independent of an allergic reaction and does not require discontinuation of the medication unless the pruritus is intolerable or unmanageable.
Incorrect answers:
A. Exacerbation of psoriasis: Psoriasis can cause pruritus, but it typically presents with characteristic erythematous, scaly plaques, which are not seen in this patient, and there’s no sign of psoriasis exacerbation.
B. Obstruction of the common bile duct: This typically causes jaundice and dark urine due to biliary obstruction, which isn’t consistent with this patient’s presentation or urinalysis findings.
D. Tamsulosin therapy: Tamsulosin, an alpha-blocker, can cause orthostatic hypotension or dizziness but is not commonly associated with pruritus.
E. Ureteral obstruction: While ureteral obstruction can lead to hematuria and pain, it would not typically cause generalized pruritus; the cause of pruritus is more likely related to the medication or another systemic issue.
Question 10:
The correct answer is B. This patient presents with severe abdominal pain, fever, and physical findings consistent with acute mesenteric ischemia. Laboratory findings of metabolic acidosis and leukocytosis further support this diagnosis. The patient’s abdominal X-ray shows dilated loops of bowel, which is indicative of disruption of peristaltic activity secondary to ischemia. On surgical resection, histopathology in acute ischemic colitis typically demonstrates coagulative necrosis of the mucosa and submucosa due to hypoperfusion. In some cases, full-thickness necrosis may occur if ischemia is severe.
Incorrect answers:
A. Caseating granulomatous inflammation with serosal fibrous adhesions: This is seen in conditions like tuberculosis or Crohn disease, but the acute presentation, along with the patient’s risk factors, suggests ischemia rather than chronic granulomatous disease.
C. Neutrophilic infiltrates in the mucosa with venous congestion and edema: This is more typical of acute colitis or infection (eg, inflammatory bowel disease), not ischemia, where more severe necrosis occurs due to vascular compromise.
D. Patchy mucopurulent exudate with exploding glandular crypts: This describes a pattern seen in infectious colitis or inflammatory bowel disease but does not fit the acute ischemic injury seen in mesenteric ischemia.
E. Transmural chronic inflammation with ulcerations extending into submucosa: This is a hallmark of chronic inflammatory bowel diseases like Crohn disease, but this patient’s acute presentation and vascular issues point to ischemic infarction instead.
Question 11:
The correct answer is C. This 37-year-old woman presents with acute, severe right-sided abdominal pain radiating to the pelvic region, associated with nausea. The physical exam reveals tenderness over the right flank and costovertebral angle. The presence of trace hematuria (occult blood in urine) and normal renal function, along with these findings, strongly suggests ureteral obstruction, most likely due to nephrolithiasis (kidney stones). The next best step in evaluation is a helical (spiral) CT scan of the abdomen and pelvis without contrast, which is highly sensitive and specific for detecting ureteral stones.
Initial symptom control:
- Analgesics (e.g., NSAIDs or opioids for pain).
- Antiemetics for nausea.
- IV fluids to maintain hydration.
Imaging:
- Helical (spiral) CT scan without contrast is the gold standard for detecting ureteral stones.
- Ultrasonography may be used in pregnant patients or where radiation exposure is a concern.
High Yield:
- If complications are present (e.g., infection, complete obstruction, AKI), inpatient admission and urgent urology consultation are required.
- For stones ≤10 mm without complications, outpatient management with pain control, hydration, and alpha blockers (if 5mm< stone <10mm) can be initiated.
Incorrect answers:
A. Cystoscopy: Used for evaluation of bladder pathology or hematuria, but not appropriate for initial imaging in suspected nephrolithiasis.
B. Exploratory laparotomy: Invasive and not indicated unless there are signs of surgical emergencies (e.g., perforation, bowel ischemia).
D. X-ray of the kidney, ureter, and bladder (KUB): Limited sensitivity and specificity for detecting kidney stones, especially radiolucent stones (e.g., uric acid).
E. No further testing is indicated at this time: Incorrect; imaging is necessary to confirm the diagnosis and guide management.
Question 12:
The correct answer is D. This 75-year-old woman presents with a syncopal episode triggered by standing, with associated orthostatic hypotension (a significant drop in blood pressure upon standing). She has no history of tonic-clonic movements or neurological deficits, and her CT scan is normal, ruling out structural brain causes. Orthostatic vital sign measurements reveal a drop in systolic blood pressure and a compensatory increase in heart rate, consistent with hypovolemia or autonomic dysfunction. Telemetry observation is crucial for monitoring cardiac rhythm and detecting any arrhythmias, a common cause of syncope.
Orthostatic hypotension: Defined as a drop in systolic BP ≥20 mm Hg or diastolic BP ≥10 mm Hg within 3 minutes of standing. Common in elderly patients and those on antihypertensive medications like lisinopril.
Management: Address underlying causes (e.g., adjust medications, ensure adequate hydration).
Telemetry observation for rhythm monitoring.
Incorrect answers:
A. Electroencephalography: Used to diagnose seizures, but there is no evidence of a seizure (no tonic-clonic movements or postictal confusion).
B. Outpatient ambulatory ECG monitoring: Less suitable as the patient is symptomatic and requires immediate monitoring.
C. Outpatient echocardiography: Useful for structural heart disease but not first-line for unexplained syncope without arrhythmias.
E. Tilt test – Reserved for unexplained syncope after initial evaluation is inconclusive
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Question 13:
The correct answer is D. This 52-year-old man with cirrhosis presents with fever, hemorrhagic bullae, and hypotension, consistent with sepsis. His recent travel and exposure to warm seawater or ingestion of raw seafood suggest Vibrio vulnificus infection, a gram-negative bacterium commonly found in marine environments.
Vibrio vulnificus: Causes wound infections, sepsis, and bullous lesions, particularly in patients with liver disease (e.g., cirrhosis). Transmitted via contact with contaminated seawater or ingestion of raw shellfish.
Treatment: Immediate antibiotics (e.g., doxycycline + ceftriaxone). Supportive care for sepsis.
Incorrect answers:
A. Enterobacter aerogenes: Typically causes nosocomial infections, not associated with marine exposure.
B. Enterococcus faecalis: Commonly causes endocarditis or urinary infections, not associated with hemorrhagic bullae.
C. Mycobacterium marinum: Causes chronic granulomatous skin infections, not sepsis or bullous lesions.
Question 14:
The correct answer is D. This 58-year-old man has uncontrolled hypertension despite being on multiple antihypertensives. The lack of improvement raises concern about medication adherence. Refill patterns provide objective data on whether the patient is filling prescriptions regularly.
Common causes of poor blood pressure control include nonadherence, secondary hypertension, or suboptimal dosing. Medication adherence is a frequent issue in chronic diseases.
Next steps: Confirm adherence through pharmacy records. Reassess patient education and address barriers (e.g., side effects, cost).
Incorrect answers:
A. Caffeine use: Minor contributor to hypertension, unlikely to explain resistance.
B. Exercise history: Important for long-term management but secondary to adherence in this scenario.
C. Frequency of fast-food consumption: May affect cardiovascular risk but does not directly explain uncontrolled hypertension.
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Question 15:
The correct answer is D. Celecoxib, a selective COX-2 inhibitor, decreases prostaglandin synthesis while sparing COX-1, minimizing gastrointestinal side effects. However, COX-2 also contributes to thromboxane A₂ production, which is involved in platelet aggregation, creating a prothrombotic state.
COX-2 inhibitors: Reduce inflammation and pain (used in osteoarthritis). Increase cardiovascular risk by disrupting prostacyclin (vasodilatory) and thromboxane A₂ (prothrombotic) balance.
Clinical relevance: Avoid in patients with cardiovascular risk factors or recent myocardial infarction.
Incorrect answers:
A. Both COX-1 and COX-2 decreasing prostanoid production: COX-2 inhibitors spare COX-1.
B. COX-1 decreasing prostacyclin production: COX-1 primarily affects gastric mucosa.
C. COX-1 decreasing thromboxane A₂ production: COX-1 is not inhibited by celecoxib.
E. COX-2 decreasing prostacyclin production: While true, the main concern is thromboxane A₂ imbalance.
Question 16:
The correct answer is B. Discrepancies in oxygen administration arise from unclear protocols. Standardizing orders ensures consistent care and reduces the risk of under- or over-administration.
Standardized protocols:
- Include clear titration guidelines.
- Prevent variability in physician and nurse practices.
- Enhance patient safety.
Implementation:
- Provide staff training on standardized protocols.
- Regular audits to ensure adherence.
Incorrect answers:
A. Conducting an in-service program: Useful but does not address systemic issues like unclear orders.
C. Encouraging nurses to refrain from adjusting therapy: Discourages autonomy without providing clear guidelines.
D. Requiring nurses to enter verbal orders: Increases administrative burden and risk of miscommunication.
E. Requiring calls for deviation: Inefficient and delays care.
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Question 17:
The correct answer is B. This 21-year-old ballet dancer presents with secondary amenorrhea, a BMI of 18 kg/m², and a history of strenuous exercise and low caloric intake. These findings are characteristic of functional hypothalamic hypogonadism, which occurs due to insufficient energy availability leading to suppression of the hypothalamic-pituitary-gonadal axis.
Etiology: Caloric deficit and excessive physical activity suppress gonadotropin-releasing hormone (GnRH) secretion, leading to low levels of LH, FSH, and estradiol.
Clinical Features: Amenorrhea, low BMI, and potentially reduced bone density due to hypoestrogenism.
Management: Restore energy balance with increased caloric intake and decreased physical activity. Hormonal therapy may be required for severe hypoestrogenism to prevent osteoporosis.
Incorrect answers:
A. Addison disease: Would present with hyperpigmentation, fatigue, hypotension, and electrolyte abnormalities, which are absent here.
C. Partial hypopituitarism: Usually affects multiple pituitary hormones, not just GnRH. This patient does not have other pituitary dysfunctions.
D. Polycystic ovarian syndrome: Presents with obesity, hyperandrogenism (hirsutism, acne), and irregular periods, which are not seen in this patient.
E. Premature ovarian failure: Characterized by elevated FSH and LH levels, which are not mentioned or expected in this case.
Question 18:
The correct answer is D. This 19-year-old pregnant woman’s history of continued smoking during pregnancy significantly increases the risk of sudden infant death syndrome (SIDS) for her infant. Maternal smoking is the most critical modifiable risk factor for SIDS.
SIDS and maternal smoking: Smoking during pregnancy exposes the fetus to nicotine and other harmful chemicals that can impair autonomic regulation, increasing SIDS risk. Second-hand smoke after birth compounds the risk. Risk reduction strategies include smoking cessation, safe sleep practices (e.g., supine sleeping position), and breastfeeding.
Other Risk Factors for SIDS:
- Maternal/antenatal:
o Substance use: Cigarettes, alcohol, recreational drugs.
o Maternal age <20.
o Inconsistent prenatal care.
- Infant-related:
o Prematurity or low birth weight.
o Unsafe sleep environment: Prone/side sleeping, soft bedding, or bed-sharing.
o Smoke exposure (maternal or secondhand).
Incorrect answers:
A. Employment status: Unemployment is associated with socioeconomic challenges but is not a direct risk factor for SIDS.
B. History of cocaine use: The patient’s urine screening was negative, and cocaine use is not a primary risk factor for SIDS.
C. Lack of breastfeeding: While breastfeeding reduces SIDS risk, it is not as significant as maternal smoking.
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Question 19:
The correct answer is B. Esophagus. This 66-year-old woman presents with a 3-day history of progressively worsening pain with swallowing solids and liquids (odynophagia). She has no nausea, vomiting, or appetite loss. A key detail in her history is the use of alendronate for osteoporosis. Bisphosphonates, especially alendronate, are well known to cause pill-induced esophagitis when tablets lodge in the esophagus, particularly if taken without adequate water or if the patient lies down shortly after ingestion. This results in direct mucosal injury and ulceration of the esophagus. The acute onset of odynophagia and lack of systemic symptoms strongly suggest localized esophageal mucosal damage. Endoscopy would most likely reveal ulceration in the esophagus, commonly in the mid-esophagus where pills tend to lodge.
Incorrect answers:
A. Duodenum: Duodenal ulcers typically present with epigastric abdominal pain, often relieved by food. They do not cause isolated pain with swallowing (odynophagia), which localizes pathology to the esophagus.
C. Gastric cardia: Ulceration in the gastric cardia would present with epigastric discomfort, nausea, or dyspepsia rather than acute pain triggered by swallowing both solids and liquids.
D. Gastric fundus: Fundal ulcers are associated with peptic ulcer disease and cause epigastric pain, not odynophagia. There is no evidence of melena, hematemesis, or chronic dyspeptic symptoms.
E. Pylorus: Pyloric pathology typically presents with symptoms of gastric outlet obstruction (eg, early satiety, vomiting) or peptic ulcer disease, not acute painful swallowing.
Question 20:
The correct answer is C. This 11-year-old boy’s parents are hesitant about the HPV vaccine due to misconceptions about its necessity. Educating the parents about HPV transmission and the vaccine’s role in preventing cancer is essential. HPV can be transmitted even in the context of monogamous relationships if one partner carries the virus.
HPV vaccine counseling:
Indications: Recommended for both boys and girls aged 9–26, ideally before sexual debut.
Benefits: Prevents infection with high-risk HPV strains responsible for cervical, anal, and oropharyngeal cancers.
Addressing concerns: Reassure parents about vaccine safety and long-term benefits.
Incorrect answers:
A. Misleading; HPV vaccines are extremely safe, and this phrasing may amplify fears.
B. Does not address the parents’ specific concern about their son’s risk of exposure.
D. Deferring vaccination reduces the opportunity for maximum efficacy.
Question 21:
The correct answer is C. The study compared emergency portacaval shunt (EPCS) with endoscopic sclerotherapy (EST) in patients with cirrhosis and acute bleeding esophageal varices. One of the significant findings was a reduction in recurrent portal-systemic encephalopathy (PSE) with EPCS (15%) compared to EST (35%). Based on the abstract, the number needed to treat (NNT) to prevent one case of recurrent PSE is calculated using the relative risk reduction (RRR):
RRR = (35% – 15%) / 35% = 20% / 35% ≈ 0.57.
NNT = 1 / Absolute Risk Reduction (ARR) = 1 / (35% – 15%) = 1 / 0.20 = 5.
Therefore, approximately 5 patients must be treated with EPCS instead of EST to prevent one case of recurrent PSE.
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Question 22:
The correct answer is B. The study’s generalizability is limited by the fact that emergency portacaval shunt (EPCS) is a technically demanding procedure requiring specialized expertise and facilities, making it accessible only at tertiary or specialty centers. This limits its widespread application, particularly in smaller or rural hospitals.
Factors limiting generalizability:
EPCS requires highly skilled surgeons and advanced equipment.
Patients in community settings may not have timely access to this intervention.
The study was conducted at a single tertiary care center, further restricting its applicability to other settings.
Incorrect answers:
A. The allocation was concealed: This ensures validity, not generalizability.
C. The follow-up period was too short: The study had a follow-up of up to 17 years, which is sufficient.
D. The patients were not blinded: Blinding may be difficult in surgical trials but does not impact generalizability.
E. Unmeasured confounders were not controlled by the study design: The study design appears rigorous, with randomization and concealed allocation.
Question 23:
The correct answer is B. The table in the abstract shows that the mean number of hospital readmissions for variceal bleeding requiring transfusion was significantly lower in patients undergoing EPCS (0.4) compared to those receiving EST (6.8). This highlights the superior efficacy of EPCS in controlling bleeding and preventing hospitalizations.
Key findings supporting the answer:
EPCS patients had significantly fewer readmissions compared to EST patients.
The difference in efficacy is statistically significant (P < .001).
Incorrect answers:
A. This is not supported by the abstract; survival differences are clearly significant.
C. EPCS improves survival, especially for patients in Child-Pugh classes A and B.
D. The study describes appropriate randomization and concealed allocation, ensuring validity.
Question 24:
The correct answer is A. This Kaplan-Meier plot shows that patients who were seizure-free at 2 years after surgery (yellow line) had significantly better long-term seizure control than those with seizures in the first 2 years postoperatively (blue and pink lines). The P-values indicate a statistically significant difference.
Key Findings:
Patients without seizures at 2 years postoperatively maintained a higher seizure-free rate over the next 15 years compared to those who had seizures within 1 or 2 years after surgery. This highlights the importance of early seizure control in predicting long-term outcomes.
Incorrect answers:
B. The Kaplan-Meier curve shows no specific clustering of recurrences in this time frame.
C. This is not supported by the data, which focus on 1- and 2-year subgroups.
D. Statistical significance (P < .05) confirms meaningful conclusions can be drawn.
Question 25:
The correct answer is E. This 2-week-old newborn with trisomy 18 has significant congenital anomalies, including dysmorphic features, severe growth restriction (5th percentile weight and head circumference), and cardiac abnormalities. The prognosis is extremely poor, with most infants succumbing within the first month. Hospice care is appropriate to prioritize comfort and support for the family.
Trisomy 18 (Edwards syndrome):
Severe intellectual disability and congenital anomalies (e.g., heart defects, overlapping fingers, rocker bottom feet).
Median survival: Less than 2 weeks for neonates; <10% survive beyond the first year.
Hospice focuses on symptom management, quality of life, and family support.
Incorrect answers:
A. Admission to the hospital for a sleep apnea study: Sleep apnea evaluation is not appropriate in the context of severe, life-limiting congenital anomalies.
B. CT scan of the head: Unnecessary given the obvious clinical syndrome and poor prognosis.
C. Electroencephalography: Seizure assessment is not the priority here.
D. Referral to a cardiologist: Although the patient has a heart murmur, invasive interventions are unlikely to change outcomes.
Question 26:
The correct answer is C. This 79-year-old man presents with acute-onset dizziness, instability, and horizontal nystagmus triggered by head movements. These findings are consistent with labyrinthitis, a condition caused by inflammation of the inner ear structures, specifically the labyrinth, which houses the vestibular system responsible for balance. Labyrinthitis is often a sequela of a viral infection and results in both vertigo and hearing loss.
Etiology: Typically follows a viral upper respiratory infection, but it can also occur due to bacterial infections, head trauma, or ototoxic medications. In this case, the patient’s history and symptoms strongly suggest a viral etiology.
Symptoms: Sudden-onset vertigo, often described as a sensation of spinning that worsens with head movement. Nausea and vomiting, secondary to the vertigo. Imbalance and unsteady gait.
Hearing loss: Present in many cases, though not noted here (likely mild in this case). Tinnitus may also occur in some cases.
Diagnosis: Clinical, based on history and physical exam findings, particularly nystagmus that is positional and suppressed by visual fixation. Vestibular testing or imaging (e.g., MRI) is only needed if central causes (e.g., stroke) are suspected.
Management: Vestibular suppressants such as meclizine or benzodiazepines (e.g., lorazepam) to alleviate vertigo. Antiemetics for nausea and vomiting.
Differentiation from Other Causes: Labyrinthitis is a peripheral vertigo condition, as evidenced by horizontal nystagmus that suppresses with visual fixation. Central causes (e.g., stroke) would present with vertical or direction-changing nystagmus and additional neurological signs.
Incorrect answers:
A. Arrhythmias cause syncope or near-syncope, not vertigo or positional symptoms.
B. Although alcohol can damage the cerebellum over time, this patient has no history of heavy alcohol use or cerebellar findings (e.g., dysmetria, ataxia, or intention tremor).
D. This condition presents as dizziness or lightheadedness upon standing, not positional vertigo. The patient’s blood pressure is stable, and symptoms are unrelated to standing or sitting.
E. Central vertigo due to posterior circulation stroke would present with additional findings, such as focal neurological deficits (e.g., weakness, dysarthria) or vertical nystagmus. The patient’s examination is consistent with a peripheral cause.
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Question 27:
The correct answer is B. This elderly woman’s progressive confusion and drowsiness over 10 days, along with a visible parietal scalp ecchymosis, strongly suggest chronic subdural hematoma (SDH) as the most likely diagnosis. Chronic SDH often occurs in older adults following minor head trauma, due to increased fragility of bridging veins and brain atrophy, which creates space for slow bleeding.
Symptoms: Gradual onset of altered mental status, drowsiness, or confusion over days to weeks. Neurological deficits may include hemiparesis, headache, or gait disturbances.
Risk Factors: Older age, anticoagulant or antiplatelet use, and minor head trauma.
Pathophysiology: Slow venous bleeding into the subdural space leads to a mass effect, causing symptoms to develop gradually over time.
Diagnosis: A non-contrast head CT is diagnostic and typically reveals a crescent-shaped collection of blood compressing the brain.
Incorrect answers:
A. Drug-drug interaction: There is no evidence of new medications or signs of toxicity from her current medications.
C. Hypothyroidism: While hypothyroidism can cause lethargy or confusion, it does not explain the scalp ecchymosis or sudden onset of symptoms.
D. Major depressive episode: Depression typically presents with chronic low mood or anhedonia, not acute confusion or scalp bruising.
E. Viral encephalitis: This would likely present with fever, headache, seizures, or focal neurological deficits, none of which are present here.
Question 28:
The correct answer is C. This 12-year-old girl with a seizure disorder is requesting a dose of carbamazepine and a prescription refill. However, since the patient is a minor and her aunt is not a legal guardian, the physician is obligated to contact the mother to obtain informed consent. Treatment without guardian consent is permissible only in emergency situations where the child’s life or health is at immediate risk, which is not the case here.
Key Considerations in Minors:
Informed Consent: Legal guardians (usually parents) must provide consent for non-emergent treatment in minors.
Emergencies: In life-threatening situations (e.g., status epilepticus), treatment can proceed without consent to protect the minor’s health.
Non-Emergent Situations: Physicians must attempt to contact the parent/guardian for consent, even if the child requests treatment.
Application in This Case: Since the patient is stable, the focus should be on obtaining consent before administering medication or writing a prescription. The mother’s consent ensures adherence to legal and ethical obligations.
Incorrect answers:
A. Administer the dose of carbamazepine and provide a prescription: This action requires parental consent in non-emergency situations.
B. Administer the dose of carbamazepine but do not provide a prescription: Both actions require guardian consent.
D. Do not contact the mother but request that the aunt sign a consent form: The aunt is not legally authorized to provide consent.
E. Provide a prescription, but do not administer the dose of carbamazepine: Writing a prescription also requires parental consent.
Question 29:
The correct answer is D. This 63-year-old man presents with a history of transient monocular vision loss, likely due to amaurosis fugax, a transient ischemic event involving the retina. The most common etiology is retinal ischemia due to atherosclerotic emboli. These emboli usually originate from ipsilateral carotid artery. So, patients with risk factors, should be evaluated with an ultrasonography of the neck.
Amaurosis Fugax:
Pathophysiology: Typically caused by a transient embolus or hypoperfusion affecting the retinal circulation.
Presentation: Sudden, temporary monocular vision loss lasting seconds to minutes, with full resolution. Classic: Curtain descending over the visual field
Etiology: Most cases arise from embolic events (e.g., carotid artery atherosclerosis, atrial fibrillation). Other causes include retinal artery vasospasm or giant cell arteritis.
Carotid Ultrasonography: Non-invasive, highly sensitive and specific for detecting carotid artery stenosis.
Incorrect answers:
A. Fluorescein angiography of the right eye: Used to evaluate retinal vascular abnormalities, but not indicated here due to the transient nature of the event.
B. Measurement of intraocular pressures: Necessary for glaucoma, which is not suspected here.
C. Transesophageal echocardiography: Appropriate for suspected cardioembolic sources, but there is no evidence of embolism here.
E. No further evaluation is indicated: This is inappropriate, as amaurosis fugax often indicates underlying atherosclerotic disease or embolic risk that requires prompt evaluation to prevent future stroke or vision loss.
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Question 30:
The correct answer is E. This 55-year-old man has symptoms and physical findings suggestive of aortic regurgitation (AR). The patient’s bounding pulses, widened pulse pressure, displaced point of maximal impulse (PMI), and a diastolic decrescendo murmur are classic for AR. Transthoracic echocardiography (TTE) is the best initial test to confirm the diagnosis, assess the severity, and evaluate for underlying causes.
Aortic Regurgitation (AR):
Pathophysiology: Backflow of blood into the left ventricle during diastole, leading to left ventricular volume overload and eventual dilation.
Clinical Features: Fatigue, exertional dyspnea, chest discomfort (due to increased myocardial oxygen demand). Bounding pulses, wide pulse pressure, displaced PMI, and diastolic murmur.
Diagnosis: TTE is the gold standard for diagnosing AR, assessing valve anatomy, and determining the degree of regurgitation.
Management:
Mild AR: Medical management (e.g., afterload reduction with ACE inhibitors or calcium channel blockers).
Severe AR: Surgery if symptomatic or evidence of left ventricular dysfunction.
Incorrect answers:
A. Arterial brachial index of the lower extremity: Used to assess peripheral arterial disease, not relevant for AR.
B. Coronary angiography: Indicated for suspected coronary artery disease, which is not evident here.
C. Pulmonary function testing: Not related to cardiac symptoms or findings.
D. Renal ultrasonography: No indication of renal pathology or hypertension secondary to renal artery stenosis.
Question 31:
The correct answer is B. This 39-year-old woman with a history of Graves’ disease treated with radioactive iodine presents with progressively worsening dyspnea, fatigue, and atrial fibrillation with a rapid ventricular response (RVR). Her clinical presentation is consistent with high-output heart failure secondary to her underlying hyperthyroidism. Echocardiography is the most appropriate next step to confirm the diagnosis and evaluate cardiac function, including structural or functional changes contributing to heart failure.
Pathophysiology: Occurs when cardiac output is elevated but insufficient to meet the metabolic demands of the body. Common causes include hyperthyroidism, anemia, and arteriovenous fistulas. Hyperthyroidism increases basal metabolic rate and oxygen demand, leading to an increase in cardiac output. Chronic exposure to elevated thyroid hormones causes increased heart rate, contractility, and decreased systemic vascular resistance, eventually leading to left ventricular dysfunction. Atrial fibrillation further exacerbates symptoms by reducing cardiac output.
Incorrect answers:
A. CT scan of the chest: Not indicated as there are no findings suggestive of lung pathology (e.g., pulmonary embolism or interstitial lung disease).
C. Perfusion lung scan: Used to evaluate for pulmonary embolism, which is unlikely in the absence of acute symptoms or risk factors.
D. Pulmonary function testing: Not appropriate, as the symptoms are cardiac in origin, not due to obstructive or restrictive lung disease.
E. Ultrasonography of the thyroid: Unnecessary because the patient’s hyperthyroidism is already diagnosed and treated.
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Question 32:
The correct answer is A. This 53-year-old man with acute pancreatitis has developed new-onset labored breathing, fever, and decreased breath sounds on the left lung base. These findings are suspicious for a left-sided pleural effusion or pneumonia, both of which are common complications of pancreatitis. A chest X-ray is the most appropriate next step to evaluate these findings.
Pancreatitis-Related Complications:
Pleural Effusion: Often exudative and due to inflammation of the diaphragm or fistula formation.
Pneumonia: Occurs secondary to impaired respiratory mechanics from pain or systemic inflammation.
Incorrect answers:
B. Determination of cardiac enzyme activity: No clinical evidence suggests myocardial ischemia.
C. Echocardiography: Unnecessary unless cardiac tamponade or pericardial effusion is suspected, which is not the case here.
D. Ultrasonography of the chest: May be used to evaluate pulmonary edema but is less accessible than chest X-ray.
E. Ventilation-perfusion lung scans: Indicated for pulmonary embolism evaluation, not suggested here.
Question 33:
The correct answer is F. This 24-year-old woman presents with recurrent episodes of irritability, insomnia, and mood swings that seem to occur in a cyclical pattern lasting 2–3 weeks. Her symptoms are likely related to her menstrual cycle, and timing of symptoms is crucial to differentiate between premenstrual dysphoric disorder (PMDD) and other mood disorders.
Key Features of PMDD:
Symptoms typically occur in the luteal phase (1–2 weeks before menses) and resolve with the onset of menstruation. Symptoms include mood changes, irritability, fatigue, insomnia, and physical symptoms (e.g., bloating, breast tenderness). Diagnosis relies on a clear temporal relationship with the menstrual cycle.
Next Steps:
Ask the patient to track her symptoms over 2–3 cycles to confirm the timing and relationship to menstruation. Management includes lifestyle modifications, SSRIs, and hormonal therapy (e.g., oral contraceptives).
Incorrect answers:
A. Carbohydrate intake: Not directly related to her mood or insomnia symptoms.
B. Coital frequency: Unrelated to her cyclic mood swings.
C. Frequency of physical activity: May impact overall well-being but is not the key history for this presentation.
D. History of psychological trauma: Relevant in other mood disorders but less likely with clear cyclic symptoms.
E. Stress level: Affects mood but does not explain the cyclic nature of her symptoms.
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Question 34:
The correct answer is B. This 55-year-old man with a fasting glucose of 126 mg/dL has impaired fasting glucose, placing him at risk for type 2 diabetes mellitus. Measurement of hemoglobin A1c is the most appropriate next step to confirm the diagnosis and assess long-term glucose control.
Diabetes Diagnosis (any one of the following):
- Fasting glucose ≥126 mg/dL.
- Hemoglobin A1c ≥6.5%.
- 2-hour glucose tolerance or random glucose ≥200 mg/dL
Incorrect answers:
A. Arterial blood gas values: Not indicated in a patient with no signs of acid-base disturbance or respiratory symptoms.
C. 3-hour glucose tolerance test: Used when initial tests are equivocal, but hemoglobin A1c is the preferred initial test.
D. Serum cortisol concentration: Unnecessary; there are no signs of adrenal insufficiency.
E. Serum fructosamine concentration: Reflects shorter-term glucose control (2–3 weeks) and is less commonly used than hemoglobin A1c.
Question 35:
The correct answer is A. This 8-year-old girl presents with a generalized tonic-clonic seizure followed by asystole, global hypokinesis, and severe left ventricular dysfunction (EF 20%) on echocardiography. Despite intensive care, the patient dies, and autopsy reveals an acute myocardial infarction. The findings are suggestive of arrhythmogenic cardiac conduction abnormalities leading to sudden cardiac arrest and secondary hypoxic injury to the myocardium.
Cardiac conduction abnormalities, such as congenital long QT syndrome or catecholaminergic polymorphic ventricular tachycardia (CPVT), are common causes of cardiac arrest in young patients without coronary artery disease.
Long QT syndrome: Prolonged repolarization predisposes to torsades de pointes, resulting in syncope or sudden cardiac death.
CPVT: Triggered by adrenergic stimuli (e.g., exercise, stress) leading to ventricular tachyarrhythmias.
Role of Arrhythmias: Arrhythmias cause transient asystole, reduced cardiac output, and hypoperfusion, leading to myocardial ischemia, hypokinesis, and eventual pump failure.
Incorrect answers:
B. Coronary artery plaque rupture: Unlikely in a child with no atherosclerotic risk factors; autopsy findings would also show evidence of atherosclerosis, which is absent.
C. Increased pulmonary vascular resistance: May lead to right-sided heart failure, but there is no evidence of pulmonary hypertension or right heart strain here.
D. Systolic prolapse of mitral valve: Seen in mitral valve prolapse but would not account for the severity of global hypokinesis or asystole.
E. Thickened left ventricular wall and contractile dysfunction: Suggestive of hypertrophic cardiomyopathy, but this patient’s echocardiography findings do not show hypertrophy, and no such findings were noted at autopsy.
Question 36:
The correct answer is A. This 2-month-old boy with conjugated hyperbilirubinemia, hypoplastic gallbladder on ultrasound, and elevated direct bilirubin is consistent with biliary atresia. The microscopic hallmark of biliary atresia is bile ductular proliferation, which results from obstruction of bile flow and progressive fibrosis.
Key Features of Biliary Atresia:
Progressive fibroinflammatory obliteration of the extrahepatic bile ducts, leading to biliary obstruction. Presents with:
- Jaundice (persistent conjugated hyperbilirubinemia).
- Pale stools and dark urine (reduced bile in stool).
- Hepatomegaly (due to inflammation and fibrosis).
- Elevated direct bilirubin and liver enzymes (ALT/AST).
- Hypoplastic or absent gallbladder on ultrasound.
Pathology:
Bile ductular proliferation occurs in response to biliary obstruction and is accompanied by portal tract fibrosis and eventual cirrhosis if untreated.
Incorrect answers:
B. Centrilobular necrosis: Seen in ischemic or toxic liver injury, not in biliary obstruction.
C. Increased glycogen stores: Associated with glycogen storage diseases, not biliary atresia.
D. Intranuclear hepatocytic inclusions: Seen in viral infections (e.g., CMV, HSV), not biliary atresia.
E. Macrovesicular steatosis: Seen in conditions like nonalcoholic fatty liver disease or metabolic disorders.
Question 37:
The correct answer is B. The graph demonstrates the receiver operating characteristic (ROC) curves of various screening tests for gestational diabetes mellitus. For screenings, we should minimize the risk of false-negative results, so the test with the highest sensitivity (curve B) should be selected.
ROC Curve Analysis:
- Sensitivity is plotted against (1 – specificity).
- The closer the curve is to the upper left corner, the better the test’s diagnostic performance.
- Curve B has the highest sensitivity, making it the most appropriate choice for this patient who prioritizes avoiding false negatives.
Question 38:
The correct answer is C. This 2-year-old girl is diagnosed with lymphadenitis, and her father is concerned due to a family history of cancer. The most appropriate response demonstrates empathy while exploring the father’s specific concerns. Open-ended questions like “Tell me what your greatest concerns are” encourage dialogue and address the underlying fear of malignancy.
Effective Communication in Pediatric Cases:
- Show empathy and acknowledge the parent’s concerns.
- Use open-ended questions to gather more information about fears or expectations.
- Reassure the parent with evidence-based explanations if appropriate.
Incorrect answers:
A. Dismissive tone may alienate the parent and prevent open communication.
B. Dismisses concerns without exploring them fully.
D. Overly reassuring and ignores the family’s fears.
E. Although this seeks clarification, it can come across as defensive or challenging rather than empathetic.
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