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Question 301Question →

For each of the following clinical presentations, match the patient scenario with the single most appropriate initial or next-step diagnostic imaging modality.

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Items

A 24-year-old professional gymnast with severe anatomical snuffbox tenderness after a fall; initial plain radiographs are negative, but definitive diagnosis is required immediately for return-to-play decisions.
A 42-year-old man with a history of ulcerative colitis who develops progressive jaundice, pruritus, and a cholestatic pattern of liver injury; transabdominal ultrasound is unremarkable.
A 67-year-old man with advanced non-small cell lung cancer who presents with progressive facial swelling, arm edema, and distended superficial veins on his chest.
A 70-year-old woman with obscure, ongoing gastrointestinal bleeding requiring multiple blood transfusions; comprehensive upper endoscopy and colonoscopy fail to identify a bleeding source.

Matches

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Answer

Occult scaphoid fracture matches to MRI of the wrist; suspected primary sclerosing cholangitis matches to MRCP; SVC syndrome matches to Contrast-enhanced CT of the chest; and obscure GI bleeding matches to Technetium-99m labeled RBC scintigraphy.
Each match accurately pairs a specialized imaging modality with its specific clinical indication: MRI for occult bone injuries, MRCP for noninvasive biliary duct evaluation, contrast-enhanced CT for mapping venous obstruction in the thorax, and nuclear scintigraphy for highly sensitive localization of slow GI hemorrhage.

Step-by-Step Solution

1
Evaluate the patient with snuffbox tenderness and negative X-rays.
Identify the need for highly sensitive imaging for an occult scaphoid fracture.
Because plain radiographs miss up to 20% of acute scaphoid fractures, an MRI is indicated when immediate diagnostic certainty is required.
2
Analyze the presentation of the patient with ulcerative colitis and new-onset cholestasis.
Recognize the high probability of primary sclerosing cholangitis (PSC).
Directs the selection of MRCP, which is the preferred noninvasive modality for evaluating the biliary tree in suspected PSC.
3
Assess the lung cancer patient with facial plethora and venous distension.
Diagnose suspected superior vena cava (SVC) syndrome.
Necessitates a contrast-enhanced CT of the chest to map the vascular anatomy and extent of obstruction.
4
Review the case of obscure gastrointestinal bleeding with negative endoscopy/colonoscopy.
Determine the need for a highly sensitive test to localize slow, intermittent bleeding.
Prompts the use of a tagged RBC scan, which is more sensitive than CT angiography for detecting slow bleeding rates.

Key Concept

Appropriate selection of imaging modalities requires matching the diagnostic capabilities of the test (e.g., sensitivity for bone marrow edema, biliary tree visualization, vascular mapping, or slow hemorrhage detection) with the specific clinical suspicion.
Estimated Time:2m 0s
Question 302Question →

Correlate the following specific cellular and molecular biopsy findings with the targeted pharmacologic agent most appropriate for exploiting that underlying neoplastic mechanism.

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Items

Biopsy of a breast mass in a premenopausal patient reveals invasive carcinoma with marked ERBB2 gene amplification.
Bone marrow aspirate from a patient presenting with marked leukocytosis shows myeloid cells harboring the t(9;22)(q34;q11) translocation.
Tissue analysis of metastatic non-small cell lung cancer in a lifelong non-smoker demonstrates an EML4-ALK inversion.
Molecular profiling of recurrent high-grade serous ovarian carcinoma identifies a deleterious germline BRCA1 mutation.

Matches

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Answer

The correct matches pair the specific foundational molecular derangement identified in the biopsy with its corresponding targeted pharmacologic inhibitor.
Each correct pair accurately links a fundamental molecular derangement within a neoplastic cell to the pharmacologic agent specifically designed to inhibit or exploit that altered pathway.

Step-by-Step Solution

1
Analyze the molecular and genetic findings described for each neoplastic tissue sample.
Identified the specific pathogenic drivers: HER2 receptor amplification, BCR-ABL fusion kinase, ALK fusion kinase, and BRCA1-mediated homologous recombination deficiency.
Understanding the foundational mechanism driving the neoplastic process is essential to successfully selecting modern targeted therapies.
2
Correlate each identified molecular driver with its specific pharmacologic inhibitor.
Matched the molecular targets to trastuzumab, imatinib, crizotinib, and olaparib, respectively.
Targeted biologic therapies exploit highly specific cellular vulnerabilities, which differ significantly across varying cancer types.

Key Concept

Targeted oncologic therapies exploit specific molecular vulnerabilities characteristic of distinct neoplastic processes, such as oncogene addiction (e.g., HER2, BCR-ABL, ALK) or synthetic lethality (e.g., PARP inhibition in BRCA-mutated cells).
Question 303Question →

Match each patient's specific occupational, environmental, or travel history to the most likely associated diagnosis based on their clinical presentation.

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Items

A 45-year-old demolition worker renovating 19th-century homes who presents with severe abdominal colic, fatigue, and new-onset unilateral extensor weakness of the wrist.
A 52-year-old agricultural laborer who recently sprayed crops and now exhibits excessive salivation, miosis, bradycardia, and generalized muscle fasciculations.
A 38-year-old cave explorer returning from the Ohio River Valley with a subacute febrile respiratory illness, dry cough, and newly detected hepatosplenomegaly.
A 62-year-old retired shipyard worker presenting with progressive dyspnea on exertion, dry cough, and chest imaging revealing bilateral pleural plaques and lower lobe interstitial opacities.

Matches

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Answer

The correct matches correlate the demolition worker with Lead toxicity, the agricultural laborer with Organophosphate poisoning, the cave explorer with Histoplasmosis, and the shipyard worker with Asbestosis.
Each patient's distinct occupational, environmental, or travel history provides the critical diagnostic anchor that, when combined with their specific clinical presentation, leads to the correct diagnosis. Thorough medical history evaluation requires recognizing these classic historical triggers to avoid premature closure and misdiagnosis.

Step-by-Step Solution

1
Analyze the demolition worker's history.
Identified exposure to older building materials (lead paint), correlating with symptoms of abdominal pain and peripheral neuropathy (wrist drop).
To establish lead toxicity as the primary diagnosis over other heavy metal poisonings.
2
Analyze the agricultural laborer's history.
Identified recent pesticide exposure correlating with a classic cholinergic and nicotinic toxidrome.
To confirm organophosphate poisoning as the cause of the acute autonomic and neuromuscular symptoms.
3
Analyze the cave explorer's geographic and hobby history.
Identified endemic fungal exposure (bat guano in the Ohio River Valley), matching the pulmonary and disseminated reticuloendothelial findings.
To differentiate Histoplasmosis from other endemic mycoses or atypical pneumonias.
4
Analyze the retired shipyard worker's history.
Identified chronic occupational asbestos exposure, supported by pathognomonic imaging findings of pleural plaques and lower lobe fibrosis.
To distinguish asbestosis from other pneumoconioses like silicosis, which typically affects upper lobes.

Key Concept

Evaluating specific occupational, environmental, and travel histories is essential for diagnosing exposure-related toxicities, endemic infections, and pneumoconioses.

Alternative Method

When approaching matching questions based on history, first isolate the most unique geographic or occupational keyword (e.g., 'shipyard', 'spelunker') and link it to its classic pathology before verifying that the clinical symptoms align with that preliminary match.
Estimated Time:1m 30s
Question 304Question →

Match each clinical laboratory profile with the most likely underlying diagnostic entity.

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Items

A 4141-year-old woman presents with palpitations. Labs: TSH\text{TSH} 0.02 \muU/mL0.02 \text{ \mu U/mL}, Free T4\text{Free T4} 0.6 ng/dL0.6 \text{ ng/dL} (Low), Free T3\text{Free T3} 6.4 pg/mL6.4 \text{ pg/mL} (High), Thyroglobulin\text{Thyroglobulin} <0.1 ng/mL<0.1 \text{ ng/mL} (Low), 2424-hour RAIU 1%1\%.
A 3535-year-old man presents with diffuse goiter and bitemporal hemianopsia. Labs: TSH\text{TSH} 7.8 \muU/mL7.8 \text{ \mu U/mL} (High), Free T4\text{Free T4} 2.9 ng/dL2.9 \text{ ng/dL} (High), Free T3\text{Free T3} 5.6 pg/mL5.6 \text{ pg/mL} (High). SHBG is elevated. Pituitary α\alpha-subunit to TSH\text{TSH} molar ratio is 2.52.5 (Ref: <1.0<1.0).
An asymptomatic 2929-year-old woman is evaluated during a routine physical. Labs: TSH\text{TSH} 5.5 \muU/mL5.5 \text{ \mu U/mL} (High), Free T4\text{Free T4} 2.6 ng/dL2.6 \text{ ng/dL} (High), Free T3\text{Free T3} 5.2 pg/mL5.2 \text{ pg/mL} (High). SHBG is normal. Pituitary α\alpha-subunit to TSH\text{TSH} molar ratio is 0.40.4 (Ref: <1.0<1.0).
A 6868-year-old man in the intensive care unit with severe sepsis. Labs: TSH\text{TSH} 0.6 \muU/mL0.6 \text{ \mu U/mL} (Normal), Free T4\text{Free T4} 1.1 ng/dL1.1 \text{ ng/dL} (Normal), Free T3\text{Free T3} 1.2 pg/mL1.2 \text{ pg/mL} (Low), Reverse T3\text{Reverse T3} 550 pg/mL550 \text{ pg/mL} (High).

Matches

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Answer

The correct matches are: Profile 1 maps to Exogenous liothyronine administration; Profile 2 maps to TSH-secreting pituitary adenoma; Profile 3 maps to Resistance to thyroid hormone; Profile 4 maps to Non-thyroidal illness syndrome.
The profiles accurately reflect the pathophysiological laboratory findings unique to each disease state. Distinguishing factitious T3 toxicosis requires noting the low T4 and Thyroglobulin. Distinguishing TSH-oma from RTH requires analyzing SHBG and alpha-subunit. Distinguishing non-thyroidal illness requires noting the elevated Reverse T3.

Step-by-Step Solution

1
Analyze the first clinical profile showing isolated T3 elevation with suppressed TSH and low T4.
Identified as exogenous liothyronine administration.
Exogenous T3 administration raises Free T3, which suppresses central TSH secretion. The lack of TSH stimulation leads to ceased endogenous thyroid production, marked by low Free T4 and undetectable thyroglobulin.
2
Compare profiles two and three, which both show central hyperthyroidism patterns (High TSH, High T4, High T3).
Profile 2 is a TSH-secreting adenoma; Profile 3 is Resistance to Thyroid Hormone (RTH).
TSH-omas (Profile 2) cause true thyrotoxicosis (driving up hepatic SHBG production) and concurrently overproduce pituitary alpha-subunits. RTH (Profile 3) is a receptor defect where tissues do not respond normally to T4/T3, resulting in normal SHBG (no peripheral thyrotoxicosis) and a normal alpha-subunit ratio.
3
Examine the fourth profile showing an ICU patient with low T3 but high Reverse T3.
Identified as non-thyroidal illness syndrome (euthyroid sick syndrome).
During critical illness, 5'-deiodinase activity decreases, reducing the conversion of T4 to T3 and shifting conversion toward the inactive metabolite Reverse T3.

Key Concept

Advanced interpretation of thyroid function tests requires integrating secondary biomarkers (Thyroglobulin, SHBG, Alpha-subunit, Reverse T3) to differentiate mechanisms of complex central and peripheral HPT axis disruption.
Estimated Time:2m 30s
Question 305Question →

Match each patient's clinical presentation and care setting with the single most appropriate initial or definitive diagnostic imaging modality.

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Items

Emergency department presentation of a 35-year-old man with abrupt onset of severe, unilateral scrotal pain, localized swelling, and an absent cremasteric reflex.
Emergency department presentation of a 55-year-old woman with a sudden-onset 'thunderclap' headache, photophobia, and neck stiffness within 4 hours of symptom onset.
Outpatient gastroenterology clinic presentation of a 28-year-old woman with known Crohn's disease complaining of progressive perianal pain and induration, concerning for a deep tissue fistula.
Primary care clinic presentation of a 65-year-old man with a recent onset of painless jaundice, acholic stools, and a palpable, non-tender right upper quadrant abdominal mass, requiring an initial evaluation step.

Matches

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Answer

The patient with abrupt scrotal pain requires a Color Doppler ultrasonography of the scrotum; the patient with a 'thunderclap' headache requires a non-contrast computed tomography of the head; the patient with Crohn's disease and perianal pain requires magnetic resonance imaging of the pelvis; and the patient with painless jaundice requires ultrasonography of the right upper quadrant as the initial test.
Each clinical scenario presents a classic diagnostic challenge where the choice of imaging is critical for timely and accurate patient management. Testicular torsion requires immediate blood flow evaluation via Doppler ultrasound. Subarachnoid hemorrhage is a neurologic emergency best initially evaluated by a non-contrast head CT to detect acute blood. Complex perianal fistulas in Crohn's disease require precise soft-tissue anatomical mapping, making pelvic MRI the gold standard. Finally, the initial evaluation of painless jaundice begins with a right upper quadrant ultrasound to differentiate between intrahepatic and extrahepatic causes of biliary obstruction, prior to advanced cross-sectional imaging.

Step-by-Step Solution

1
Analyze each clinical vignette to identify the primary suspected diagnosis based on the key signs, symptoms, and the clinical setting.
The suspected diagnoses are testicular torsion, subarachnoid hemorrhage, perianal fistula from Crohn's disease, and malignant biliary obstruction, respectively.
Accurate recognition of the underlying pathology is the prerequisite for selecting the appropriate diagnostic pathway.
2
Determine the optimal, evidence-based imaging modality tailored to both the suspected pathology and the chronological sequence of evaluation (e.g., initial versus definitive staging).
Identified Doppler US for torsion, non-contrast head CT for acute hemorrhage, pelvic MRI for soft-tissue fistula mapping, and RUQ ultrasound for initial biliary evaluation.
Different tissue types and diagnostic urgencies require specific imaging techniques (e.g., ultrasound for flow and biliary tracts, non-contrast CT for acute intracranial hemorrhage, MRI for detailed pelvic soft tissue).
3
Match each identified imaging modality to its corresponding patient presentation.
All four clinical presentations are correctly paired with their respective optimal imaging study.
This confirms mastery of diagnostic imaging selection guidelines.

Key Concept

Selecting the most appropriate initial or definitive imaging modality based on the specific clinical presentation, suspected diagnosis, and evidence-based guidelines.
Question 306Question →

A 38-year-old patient is admitted to the diagnostic evaluation unit for recurrent episodes of diaphoresis, palpitations, and confusion that resolve rapidly with carbohydrate intake. A supervised 72-hour fasting test is initiated, and comprehensive laboratory studies are drawn when the patient develops symptomatic hypoglycemia (capillary blood glucose 42 mg/dL). Match each distinct laboratory profile below with its most likely underlying pathophysiologic mechanism.

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Items

Serum insulin elevated, C-peptide elevated, proinsulin elevated, negative oral secretagogue screen
Serum insulin elevated, C-peptide suppressed, proinsulin suppressed, negative oral secretagogue screen
Serum insulin elevated, C-peptide elevated, proinsulin normal, positive oral secretagogue screen
Serum insulin suppressed, C-peptide suppressed, elevated IGF-II, low beta-hydroxybutyrate

Matches

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Answer

Profile L1 matches autonomous exocytosis (insulinoma). Profile L2 matches direct hormone administration (exogenous insulin). Profile L3 matches K-ATP channel closure (sulfonylurea). Profile L4 matches paraneoplastic receptor activation (non-islet cell tumor hypoglycemia).
Each laboratory profile uniquely maps to a pathophysiologic mechanism of hypoglycemia. Elevated insulin with high C-peptide and a negative drug screen points to an insulinoma (autonomous neuroendocrine secretion). High insulin with low C-peptide indicates exogenous insulin injection, as commercial preparations lack the cleavage byproduct. High insulin and C-peptide with a positive drug screen confirms sulfonylurea use, which pharmacologically closes K-ATP channels. Low insulin and C-peptide with high IGF-II indicates a paraneoplastic syndrome where the tumor secretes a peptide that activates peripheral insulin receptors.

Step-by-Step Solution

1
Analyze the relationship between serum insulin and C-peptide to differentiate endogenous from exogenous hyperinsulinemia.
Elevated insulin with suppressed C-peptide identifies exogenous administration, while concurrent elevation of both points to an endogenous source.
Endogenous insulin is secreted in a 1:1 equimolar ratio with C-peptide, whereas pharmaceutical insulin preparations do not contain C-peptide.
2
Evaluate the oral secretagogue screen in profiles with endogenous hyperinsulinemia.
A positive screen identifies pharmacologic stimulation of beta cells, whereas a negative screen points to autonomous tumor secretion.
Sulfonylureas and meglitinides artificially stimulate endogenous insulin release by closing K-ATP channels, mimicking an insulinoma.
3
Identify non-insulin-mediated mechanisms in profiles with suppressed insulin and C-peptide.
Hypoglycemia with suppressed beta-cell function and elevated IGF-II indicates a paraneoplastic syndrome.
Tumor-secreted IGF-II binds to insulin receptors, driving glucose into tissues while appropriately suppressing endogenous pancreatic beta-cell activity via negative feedback.

Key Concept

Pathophysiologic mechanisms and diagnostic laboratory profiles of fasting hypoglycemia
Question 307Question →

Match the following thyroid laboratory profiles to their most likely diagnostic etiology.

Reference Ranges:
TSH: 0.4−4.00.4-4.0 μ\mu U/mL
Free T4: 0.9−2.40.9-2.4 ng/dL
Total T3: 80−20080-200 ng/dL
24-hour Radioactive Iodine Uptake (RAIU): 10−30%10-30\%

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Items

Profile 1: TSH 0.010.01 μ\mu U/mL, Free T4 2.92.9 ng/dL, 24-hour RAIU 2%2\%
Profile 2: TSH 12.512.5 μ\mu U/mL, Free T4 0.70.7 ng/dL, Anti-TPO Antibodies 850850 IU/mL
Profile 3: TSH 0.020.02 μ\mu U/mL, Free T4 3.23.2 ng/dL, 24-hour RAIU 68%68\% (diffuse pattern)
Profile 4: TSH 0.80.8 μ\mu U/mL, Free T4 1.11.1 ng/dL, Total T3 6565 ng/dL, Reverse T3 4545 ng/dL (Elevated)

Matches

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Answer

Profile 1 matches with Destructive thyroiditis; Profile 2 matches with Hashimoto thyroiditis; Profile 3 matches with Graves disease; Profile 4 matches with Euthyroid sick syndrome.
Each laboratory profile specifically aligns with one distinct pathophysiological mechanism: hormone leakage without synthesis (Profile 1), autoimmune gland destruction leading to failure (Profile 2), autoimmune continuous stimulation (Profile 3), and adaptive peripheral hormone diversion during illness (Profile 4).

Step-by-Step Solution

1
Evaluate the primary thyroid axis via TSH and Free T4.
Profiles 1 and 3 indicate primary hyperthyroidism (Low TSH, High Free T4). Profile 2 indicates primary hypothyroidism (High TSH, Low Free T4). Profile 4 indicates a euthyroid central state with an isolated low T3.
TSH and Free T4 establish the patient's baseline biochemical thyroid status.
2
Utilize secondary diagnostic markers (RAIU, antibodies, Reverse T3) to differentiate specific etiologies within each broad category.
Profile 1's low RAIU points to destructive release, while Profile 3's high RAIU points to active synthesis. Profile 2's antibodies confirm autoimmunity. Profile 4's elevated reverse T3 confirms altered peripheral metabolism.
Secondary tests distinguish between different pathophysiologic mechanisms that can cause similar TSH/Free T4 patterns.

Key Concept

Interpretation of thyroid function tests, radioactive iodine uptake, and peripheral thyroid hormone metabolism.
Question 308Question →

A group of medical residents is reviewing classic abdominal physical examination findings and their underlying pathophysiological or anatomic mechanisms. Match each eponymous physical examination sign with the mechanism that best explains its clinical presentation.

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Items

Cullen sign
Kehr sign
Murphy sign
Courvoisier sign
Rovsing sign

Matches

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Answer

Cullen sign matches with extravasation of hemorrhagic exudate to periumbilical tissue; Kehr sign matches with C3-C5 nerve root mediated diaphragmatic irritation; Murphy sign matches with descent of an inflamed hepatobiliary structure during inspiration; Courvoisier sign matches with malignant obstruction of the common bile duct causing painless distention; Rovsing sign matches with transmission of localized pressure stretching the right-sided parietal peritoneum.
Each physical examination sign represents a distinct anatomical or pathophysiological process. Cullen sign is periumbilical ecchymosis due to tracking of retroperitoneal or intraperitoneal hemorrhage along fascial planes. Kehr sign is left shoulder pain referred via the phrenic nerve from irritation of the inferior surface of the diaphragm, classic for splenic rupture. Murphy sign is an inspiratory arrest caused by an inflamed gallbladder descending during respiration to meet the palpating hand. Courvoisier sign is a palpable, non-tender gallbladder caused by chronic, malignant obstruction of the common bile duct. Rovsing sign relies on the transmission of manual pressure from the left lower quadrant across the abdominal cavity, irritating the inflamed right-sided parietal peritoneum overlying the appendix.

Step-by-Step Solution

1
Analyze each eponymous physical examination sign to determine its clinical definition and presentation.
Identified the signs: Cullen (periumbilical ecchymosis), Kehr (referred left shoulder pain), Murphy (inspiratory arrest on right upper quadrant palpation), Courvoisier (palpable painless gallbladder with jaundice), and Rovsing (right lower quadrant pain elicited upon left lower quadrant palpation).
Accurate definition of the eponymous signs is required before mapping them to their underlying physiology.
2
Correlate each defined physical sign with its underlying pathophysiological or anatomical mechanism.
Mapped the corresponding anatomical pathways: retroperitoneal tracking to periumbilical area (Cullen), phrenic nerve referral (Kehr), diaphragmatic excursion (Murphy), distal malignant obstruction (Courvoisier), and indirect pressure transmission across the abdomen (Rovsing).
Understanding the anatomical mechanism allows for accurate diagnostic interpretation of physical findings in clinical practice.

Key Concept

Physical Examination Findings and their Pathophysiological Mechanisms
Question 309Question →

Match each patient's clinical presentation with the single most appropriate initial or next imaging study to establish the diagnosis.

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Items

A 28-year-old pregnant woman at 16 weeks gestation presents with acute dyspnea and pleuritic chest pain. Her chest radiograph is normal, and bilateral lower extremity venous ultrasound shows no deep vein thrombosis.
A 70-year-old man with a non-conditional permanent pacemaker presents with rapidly progressive bilateral lower extremity weakness, sensory loss below the umbilicus, and acute urinary retention.
A 55-year-old man presents with sudden-onset, severe, tearing chest pain radiating to the back. Examination shows asymmetric radial pulses. Laboratory testing reveals a serum creatinine of 3.8 mg/dL.
A 9-year-old girl presents with a 1-day history of periumbilical pain that has migrated to the right lower quadrant, accompanied by fever, nausea, and localized rebound tenderness.

Matches

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Answer

The pregnant patient with suspected pulmonary embolism matches with Ventilation-perfusion (V/Q) scan. The patient with suspected spinal cord compression and a pacemaker matches with CT myelography. The patient with suspected aortic dissection and acute kidney injury matches with Transesophageal echocardiography (TEE). The pediatric patient with suspected appendicitis matches with Graded compression ultrasonography.
Each correct match directly applies evidence-based guidelines for imaging selection while navigating a major patient-specific contraindication (e.g., pregnancy, severe kidney injury, non-compatible medical devices, and young age).

Step-by-Step Solution

1
Analyze the pregnant patient's presentation (acute dyspnea, pleuritic pain, normal chest radiograph, and negative lower extremity ultrasound).
Identify that the next best step is pulmonary imaging that strictly minimizes radiation exposure.
V/Q scan is preferred over CT pulmonary angiography in pregnancy when the initial chest radiograph is completely normal.
2
Evaluate the patient with acute spinal cord compression symptoms and a non-conditional pacemaker.
Determine that Magnetic Resonance Imaging (MRI) is absolutely contraindicated.
CT myelography provides the necessary visualization of the spinal canal and cord when an MRI cannot be safely performed.
3
Assess the patient with signs of acute aortic dissection and severe acute kidney injury.
Recognize that iodine-based contrast for CT angiography is contraindicated.
Transesophageal echocardiography (TEE) accurately diagnoses aortic dissection without the need for nephrotoxic contrast agents.
4
Consider the pediatric patient with classic symptoms of acute appendicitis.
Select an imaging modality that entirely avoids ionizing radiation.
Graded compression ultrasonography is the first-line imaging choice in children to adhere to radiation safety principles.

Key Concept

When ordering diagnostic imaging, the choice of modality must be strictly tailored to patient-specific contraindications, such as avoiding ionizing radiation in children and pregnant women, avoiding iodinated contrast in severe acute kidney injury, and avoiding MRI in patients with non-conditional metallic implants.
Estimated Time:1m 30s
Question 310Question →

Neurological physical examination is critical for localizing acute ischemic strokes. Match each constellation of physical examination findings with its most likely corresponding occluded vascular territory.

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Items

Ipsilateral ptosis and miosis, hoarseness, absent gag reflex, and contralateral body loss of pain and temperature sensation
Ipsilateral tongue deviation upon protrusion, contralateral hemiparesis, and contralateral loss of proprioception
Ipsilateral ptosis, resting 'down and out' eye position with mydriasis, and contralateral hemiparesis
Ipsilateral complete facial paralysis, inability to abduct the eye, and contralateral hemiparesis
Contralateral lower extremity weakness and sensory loss, with relative sparing of the upper extremity, accompanied by urinary incontinence

Matches

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Answer

The correct matches correlate classic neurological examination findings to their respective vascular territories: Lateral Medullary (Wallenberg) syndrome to PICA, Medial Medullary syndrome to ASA, Midbrain (Weber) syndrome to PCA paramedian branches, Caudal Pontine syndrome to Basilar paramedian branches, and medial frontoparietal cortical strokes to ACA.
Crossed signs (ipsilateral cranial nerve palsies and contralateral long tract deficits) indicate a brainstem lesion. CN III localization points to the midbrain (PCA paramedian branches). CN VI/VII localizations point to the pons (Basilar paramedian branches). CN XII localization points to the medial medulla (ASA), while the nucleus ambiguus and sympathetic fibers point to the lateral medulla (PICA). Cortical strokes lack crossed cranial nerve signs; ACA strokes preferentially cause contralateral lower extremity weakness and sensory loss, along with incontinence, due to medial cortex involvement.

Step-by-Step Solution

1
Analyze the cranial nerve deficits to determine the rostrocaudal level of the brainstem lesion.
Oculomotor (CN III) deficits localize to the midbrain. Abducens (CN VI) and Facial (CN VII) deficits localize to the pons. Glossopharyngeal (CN IX), Vagus (CN X), and Hypoglossal (CN XII) deficits localize to the medulla.
Cranial nerve nuclei have strict vertical anatomical positions within the brainstem.
2
Evaluate the long tract signs (motor and sensory) to establish the medial-lateral position of the lesion.
Corticospinal tract (motor) and medial lemniscus (proprioception) deficits indicate a medial lesion. Spinothalamic tract (pain/temperature) and sympathetic chain (Horner syndrome) deficits indicate a lateral lesion.
Vascular supply to the brainstem is strictly segregated into paramedian (medial structures) and circumferential (lateral structures) arterial branches.
3
Synthesize the neuroanatomical localization to deduce the occluded vascular territory.
A medial medullary lesion maps to the ASA, a lateral medullary lesion to the PICA, a medial pontine lesion to basilar paramedian branches, and a midbrain lesion to PCA paramedian branches. Deficits sparing cranial nerves but disproportionately affecting the contralateral leg map to the ACA.
Understanding distinct cerebrovascular territories is necessary to establish the etiology of the physical examination findings.

Key Concept

Neuroanatomical localization of acute ischemic strokes using cranial nerve and long tract physical examination findings
Estimated Time:1m 30s
Question 311Question →

Match each characteristic thoracic imaging finding described below with its most likely associated clinical condition.

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Items

Enlarged, globular cardiac silhouette with a 'water bottle' configuration on a PA chest radiograph
Shallow, wedge-shaped peripheral consolidation with its base against the pleural surface on a chest radiograph
Abnormal radiolucency extending deeply into the costophrenic angle on a supine anteroposterior chest radiograph
Bilateral, symmetric, perihilar airspace opacities that spare the peripheral lung zones on a chest radiograph

Matches

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Answer

The 'water bottle' silhouette matches a large pericardial effusion; the wedge-shaped consolidation matches a pulmonary embolism with infarction; the abnormal radiolucency in the costophrenic angle matches a supine pneumothorax; and the perihilar opacities match acute cardiogenic pulmonary edema.
Each radiographic finding is a pathognomonic sign for a specific acute cardiopulmonary pathology. The 'water bottle' silhouette represents fluid accumulation in the pericardial space. 'Hampton's hump' reflects localized lung necrosis and hemorrhage due to a pulmonary embolus. The 'deep sulcus sign' indicates pleural air collecting in the nondependent costophrenic recess in a supine patient. The 'batwing' pattern reflects fluid shifting into the central alveolar spaces due to elevated pulmonary venous pressure.

Step-by-Step Solution

1
Analyze the description of the 'water bottle' cardiac silhouette.
Identify this as representing an accumulation of fluid in the pericardial sac.
Pericardial fluid settles dependently, rounding the heart borders and eliminating normal anatomical indentations.
2
Evaluate the wedge-shaped peripheral consolidation.
Associate this finding with pulmonary infarction due to a distal pulmonary embolism.
Vascular occlusion leads to downstream lung ischemia and hemorrhage, which takes a wedge shape corresponding to the affected vascular territory.
3
Assess the abnormal lucency in the costophrenic angle on a supine film.
Correlate this 'deep sulcus sign' with a pneumothorax in a recumbent patient.
In a supine position, free pleural air rises to the highest point in the hemithorax, which is anterior and basal, deepening the sulcus rather than forming an apical line.
4
Examine the description of bilateral perihilar 'batwing' opacities.
Link this structural pattern to acute cardiogenic pulmonary edema.
Elevated hydrostatic pressure causes fluid to extravagate preferentially in the central, perihilar alveolar spaces before extending peripherally.

Key Concept

Classic Thoracic Imaging Signs
Question 312Question →

For each of the following clinical scenarios requiring targeted biologic therapy, select the precise immunopathologic mechanism of the most appropriate therapeutic agent.

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Items

A 32-year-old woman with highly active relapsing-remitting multiple sclerosis requires escalation of therapy. Serological testing for the John Cunningham (JC) virus is negative.
A 45-year-old man with medically refractory chronic spontaneous urticaria continues to experience daily wheals and severe pruritus despite maximum tolerated doses of second-generation H1-antihistamines.
A 28-year-old woman is diagnosed with severe fistulizing Crohn disease and concurrent moderate-to-severe plaque psoriasis. She requires induction and maintenance therapy.
A 55-year-old man with newly diagnosed microscopic polyangiitis and rapidly progressive glomerulonephritis requires non-glucocorticoid induction therapy.

Matches

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Answer

The correct matches align each specific autoimmune or inflammatory condition with the precise molecular target of its corresponding first-line or escalation biologic agent: MS with alpha-4 integrin blockade, chronic urticaria with IgE binding, Crohn/psoriasis with IL-12/23 p40 inhibition, and microscopic polyangiitis with CD20 depletion.
Each clinical presentation requires a specific immunomodulator whose mechanism precisely targets the underlying pathophysiology of the disease. Natalizumab blocks leukocyte CNS entry in MS. Omalizumab neutralizes IgE in chronic urticaria. Ustekinumab halts the IL-12/23 inflammatory cascade in Crohn disease and psoriasis. Rituximab depletes the autoantibody-producing B cells in ANCA-associated vasculitis.

Step-by-Step Solution

1
Identify the indicated biologic agent for each specific clinical scenario.
Natalizumab is indicated for the MS patient. Omalizumab is indicated for the chronic urticaria patient. Ustekinumab is indicated for the patient with Crohn disease and psoriasis. Rituximab is indicated for the patient with microscopic polyangiitis.
Establishing the correct drug based on clinical presentation and guidelines is necessary before identifying its molecular mechanism.
2
Map each identified agent to its immunopharmacologic mechanism of action.
Natalizumab blocks alpha-4 integrin; Omalizumab binds circulating IgE; Ustekinumab targets the IL-12/23 p40 subunit; Rituximab depletes CD20+ B cells.
Demonstrates foundational knowledge of how targeted immunotherapies modulate specific immune cascades and pathways.

Key Concept

Understanding the precise immunologic targets of monoclonal antibodies is essential for selecting appropriate therapies and anticipating specific adverse effects or contraindications (e.g., PML risk with alpha-4 integrin blockade).
Question 313Question →

A physician is reviewing laboratory results for several patients presenting with microcytic anemia (Mean Corpuscular Volume < 80 fL). Match the following serum iron and hematologic profiles to their most likely diagnostic etiology.

Reference ranges:
Serum iron: 60-170 µg/dL
Total iron-binding capacity (TIBC): 240-450 µg/dL
Ferritin: 15-200 ng/mL
Transferrin saturation: 20-50%
Red Cell Distribution Width (RDW): 11.5-14.5%

Click a left item, then click its matching right item

Items

Serum iron: 35 µg/dL, TIBC: 480 µg/dL, Ferritin: 8 ng/mL, Transferrin saturation: 7%
Serum iron: 40 µg/dL, TIBC: 210 µg/dL, Ferritin: 350 ng/mL, Transferrin saturation: 19%
Serum iron: 185 µg/dL, TIBC: 280 µg/dL, Ferritin: 450 ng/mL, Transferrin saturation: 66%
Serum iron: 95 µg/dL, TIBC: 310 µg/dL, Ferritin: 110 ng/mL, Transferrin saturation: 30%, RDW: 12%

Matches

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Answer

Profile 1 matches Iron deficiency anemia; Profile 2 matches Anemia of chronic inflammation; Profile 3 matches Sideroblastic anemia; Profile 4 matches Beta-thalassemia minor.
Interpreting microcytic anemias requires analyzing the interplay between serum iron, TIBC, and ferritin. Iron deficiency is characterized by depleted stores (low ferritin) and compensatory increased transferrin (high TIBC). Anemia of chronic inflammation is driven by hepcidin, which sequesters iron in macrophages (high ferritin) and decreases transferrin synthesis (low TIBC). Sideroblastic anemia involves an inability to incorporate iron into protoporphyrin, leading to systemic iron accumulation (high serum iron, high ferritin). Beta-thalassemia is a primary globin defect; therefore, iron studies remain normal, and patients typically present with uniform microcytosis (normal RDW).

Step-by-Step Solution

1
Evaluate ferritin levels as the primary indicator of total body iron stores.
A distinctly low ferritin uniquely identifies iron deficiency, while high or normal levels point to chronic disease, sideroblastic anemia, or thalassemia.
Ferritin is the most specific initial test to differentiate true systemic iron deficiency from other causes of microcytic anemia.
2
Assess TIBC and transferrin saturation in patients presenting with normal or high ferritin levels.
A low TIBC with high ferritin indicates anemia of chronic inflammation. Conversely, high transferrin saturation with high ferritin points to sideroblastic anemia or iron overload.
Hepcidin upregulation in chronic inflammation decreases transferrin (TIBC), whereas defective heme synthesis in sideroblastic anemia leaves excess iron unbound in serum.
3
Review the red cell distribution width (RDW) in the context of entirely normal iron studies.
Normal iron studies accompanied by a normal RDW in the setting of isolated microcytosis is indicative of thalassemia trait.
Thalassemia is a primary globin chain synthesis defect, meaning iron metabolism remains unaffected, and red cell sizing is uniformly microcytic without the size variation seen in early iron deficiency.

Key Concept

Differential diagnosis of microcytic anemia using serum iron studies.
Question 314Question →

Match each clinical presentation to the most appropriate initial or confirmatory laboratory test required to establish the diagnosis.

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Items

A 35-year-old construction worker presents with recurrent severe abdominal cramping, new-onset right foot drop, and a CBC demonstrating microcytic anemia with basophilic stippling.
A 42-year-old agricultural worker complains of progressive stocking-glove sensorimotor neuropathy, painful hyperkeratosis on the palms and soles, and transverse white lines on the fingernails.
A 28-year-old man presents with a new-onset resting tremor, worsening dysarthria, and mildly elevated hepatocellular transaminases without serologic evidence of viral hepatitis.
A 55-year-old man is evaluated for progressive erectile dysfunction, generalized skin hyperpigmentation, and bilateral symmetric arthropathy involving the second and third metacarpophalangeal joints.
A 45-year-old woman receiving long-term total parenteral nutrition develops an erythematous, vesicular perioral and acral dermatitis, accompanied by alopecia and ageusia.

Matches

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Answer

The presentations correspond respectively to lead toxicity, arsenic poisoning, Wilson disease, hereditary hemochromatosis, and zinc deficiency, each requiring a specific targeted laboratory test.
Each clinical presentation contains classic pathognomonic features for a specific condition (lead toxicity, arsenic toxicity, Wilson disease, hemochromatosis, and zinc deficiency), which dictate the precise initial or confirmatory laboratory assay required.

Step-by-Step Solution

1
Analyze the first clinical vignette for key syndromic features.
Identified abdominal pain, motor neuropathy (foot drop), and basophilic stippling.
These findings are pathognomonic for lead toxicity, necessitating a whole blood lead level rather than a serum level.
2
Evaluate the second clinical vignette for characteristic physical exam findings.
Identified neuropathy, palmoplantar hyperkeratosis, and Mees lines on the nails.
These are hallmark signs of chronic arsenic exposure, best diagnosed via a 24-hour urinary arsenic concentration.
3
Assess the third clinical vignette involving a young adult with mixed neuropsychiatric and hepatic manifestations.
Identified a resting tremor, dysarthria, and unexplained transaminitis.
This combination strongly suggests Wilson disease, which requires testing for serum ceruloplasmin and 24-hour urinary copper.
4
Review the fourth clinical vignette for classic systemic and joint findings.
Identified erectile dysfunction, hyperpigmentation, and second/third metacarpophalangeal arthropathy.
These findings indicate hereditary hemochromatosis, prompting an initial serum iron panel.
5
Analyze the fifth clinical vignette focusing on the nutritional context and cutaneous findings.
Identified a patient on total parenteral nutrition developing periorificial dermatitis and ageusia.
This presentation is characteristic of acquired zinc deficiency, confirmed by measuring the serum zinc level.

Key Concept

Selecting the most appropriate diagnostic laboratory test requires precise pattern recognition of specific toxicological, metabolic, and nutritional deficiency syndromes, as well as an understanding of the specific specimen type required (e.g., whole blood vs. serum).
Estimated Time:2m 0s
Question 315Question →

Match the following distinct radiographic descriptions with their most likely underlying clinical condition or pathophysiologic diagnosis.

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Items

Focal, wedge-shaped enhancement of hepatic segment IV (quadrate lobe) on early arterial phase abdominal CT
Central non-enhancing filling defect within the superior sagittal sinus surrounded by contrast on a head CT venogram
Central focal area of ground-glass opacity completely surrounded by a denser, complete ring of consolidation on high-resolution chest CT
Sharp linear radiopacity traversing the right upper quadrant, distinctly outlined by radiolucent gas on both of its sides on a supine abdominal radiograph

Matches

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Answer

The correct matching pairs specific imaging findings to their classic underlying diagnoses: Segment IV hepatic enhancement matches Superior Vena Cava Syndrome, the superior sagittal sinus filling defect matches Cerebral Venous Sinus Thrombosis, the ring of consolidation surrounding ground-glass opacity matches Cryptogenic Organizing Pneumonia, and the linear radiopacity outlined by gas matches Pneumoperitoneum.
Each radiographic description corresponds precisely to a classic diagnostic sign. The 'hot quadrate lobe' sign reflects collateral circulation in SVC syndrome. The 'empty delta' sign represents a thrombus in cerebral venous sinus thrombosis. The 'reversed halo' sign is characteristic of cryptogenic organizing pneumonia. The 'falciform ligament' sign indicates free air in pneumoperitoneum on a supine film.

Step-by-Step Solution

1
Evaluate the focal hepatic segment IV enhancement on arterial CT.
Identified as the 'hot quadrate lobe' sign.
In SVC syndrome, systemic venous return diverts through the internal mammary and paraumbilical veins, directly entering the left portal system and prematurely enhancing segment IV.
2
Evaluate the sagittal sinus filling defect on head CT venogram.
Identified as the 'empty delta' sign.
Pathognomonic for dural venous sinus thrombosis; the 'empty' center represents the thrombus, while the surrounding enhancement is collateral dural venous flow.
3
Evaluate the ring of consolidation around ground-glass opacity on chest CT.
Identified as the 'reversed halo' or 'atoll' sign.
Characteristic of cryptogenic organizing pneumonia (or certain fungal infections), differentiating it from the standard halo sign.
4
Evaluate the linear radiopacity outlined by gas on a supine abdominal X-ray.
Identified as the 'falciform ligament' sign.
Free intraperitoneal air rises in a supine patient, outlining both sides of the falciform ligament, serving as a critical indicator of massive pneumoperitoneum.

Key Concept

Identification of pathognomonic eponymous imaging signs and understanding their underlying pathophysiologic mechanisms is essential for diagnosing critical vascular, inflammatory, and surgical emergencies.
Question 316Question →

Various hereditary cancer syndromes are characterized by distinct clinical presentations and specific underlying molecular defects. Match each patient's clinical vignette with the fundamental genetic mechanism responsible for their disease pathogenesis.

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Items

A 35-year-old female (BP 185/115 mmHg, HR 105 bpm) is evaluated for a rapidly enlarging thyroid mass. Physical exam notes oral mucosal neuromas. Labs demonstrate elevated serum calcitonin and 24-hour urine fractionated metanephrines.
An asymptomatic 42-year-old male with normal vital signs undergoes endoscopic screening due to family history. Gastroenterology reports the presence of approximately 300 adenomatous colonic polyps.
A 29-year-old female presents with progressive gait ataxia. Vital signs are within normal limits. Neuroimaging identifies a cerebellar hemangioblastoma, while concurrent abdominal ultrasound reveals bilateral renal cysts.
A 48-year-old female discovers a painless, fixed 3-cm breast mass. Vitals are unremarkable. Pathology confirms triple-negative invasive ductal carcinoma. Her pedigree includes a first-degree relative with high-grade serous ovarian cancer.

Matches

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Answer

MEN2B (vignette 1) is driven by RET receptor tyrosine kinase activation. FAP (vignette 2) is caused by APC mutation and failure to degrade β\beta-catenin. VHL disease (vignette 3) results from impaired HIF-1 α\alpha degradation. HBOC syndrome (vignette 4) is due to defective homologous recombination DNA repair.
This question requires a two-step reasoning process: first, diagnosing the hereditary cancer syndrome from the clinical vignette, and second, identifying the fundamental molecular defect responsible for that syndrome. The vignettes describe MEN2B (RET mutation), FAP (APC mutation), VHL disease (VHL mutation), and HBOC syndrome (BRCA mutation). Matching these clinical phenotypes to their respective receptor tyrosine kinase activation, Wnt/β\beta-catenin signaling dysregulation, impaired HIF-1 α\alpha degradation, and defective homologous recombination correctly maps the neoplastic processes.

Step-by-Step Solution

1
Analyze the first vignette to diagnose the syndrome and its genetic basis.
The triad of medullary thyroid cancer, pheochromocytoma, and mucosal neuromas diagnoses MEN2B, caused by RET receptor tyrosine kinase activation.
Recognizing the syndromic presentation is the first step to identifying the specific oncogenic driver.
2
Evaluate the second vignette's endoscopic findings.
Hundreds of colonic polyps indicate FAP, which results from APC gene mutation and failure to degrade β\beta-catenin.
FAP has a distinct molecular pathogenesis compared to other polyposis syndromes.
3
Identify the disease described in the third vignette.
Hemangioblastoma and renal cysts are classic for VHL disease, driven by impaired HIF-1 α\alpha degradation.
VHL mutations directly link defective angiogenesis regulation to tumor development.
4
Assess the fourth vignette's family history and pathology.
Triple-negative breast cancer and familial ovarian cancer suggest BRCA mutations, which impair double-strand DNA repair.
BRCA mutations exhibit a characteristic pattern of related malignancies due to genomic instability.

Key Concept

Molecular pathogenesis and genetic drivers of hereditary cancer syndromes
Question 317Question →

For each patient presenting with hepatobiliary or systemic symptoms, select the most appropriate diagnostic laboratory test to confirm the underlying etiology.

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Items

A 45-year-old female presents with progressive fatigue and intense generalized pruritus. Laboratory studies show an alkaline phosphatase of 450 U/L, normal aminotransferases, and a normal right upper quadrant ultrasound.
A 29-year-old female presents with lethargy and scleral icterus. Labs reveal AST 1250 U/L, ALT 1400 U/L, and elevated total IgG. Viral hepatitis serologies are negative.
A 52-year-old male presents with joint pain, erectile dysfunction, and recent-onset polyuria. Physical examination reveals bronze-colored skin and hepatomegaly.
A 22-year-old male is brought in by his family due to recent personality changes, declining academic performance, and a new-onset resting tremor. Examination reveals mild jaundice.

Matches

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Answer

Primary Biliary Cholangitis requires an Antimitochondrial antibody assay; Autoimmune Hepatitis requires Anti-smooth muscle and antinuclear antibodies; Hereditary Hemochromatosis requires Fasting transferrin saturation and serum ferritin; and Wilson disease requires a Serum ceruloplasmin level.
Each laboratory test serves as a highly specific diagnostic marker for a distinct etiology of hepatobiliary disease. AMA confirms Primary Biliary Cholangitis. Fasting iron studies (transferrin saturation and ferritin) screen for Hereditary Hemochromatosis. Serum ceruloplasmin is the necessary initial step for Wilson disease. ASMA and ANA are required for diagnosing Autoimmune Hepatitis.

Step-by-Step Solution

1
Analyze the patient demographics and symptom profile.
Categorize the presentation into distinct clinical syndromes: isolated cholestasis (pruritus, high alk phos), acute hepatocellular injury (jaundice, high AST/ALT), iron overload (bronze skin, diabetes, hypogonadism), and copper accumulation (neuropsychiatric signs, early-onset liver disease).
Different etiologies of liver and systemic diseases present with characteristic symptom clusters and biochemical patterns.
2
Select the confirmatory serologic or biochemical test for each suspected condition.
Match PBC with AMA, AIH with ASMA/ANA, Hemochromatosis with iron studies, and Wilson disease with ceruloplasmin.
Targeted diagnostic testing minimizes unnecessary investigations and definitively establishes the diagnosis for these autoimmune and metabolic conditions.

Key Concept

Selecting specific diagnostic laboratory tests based on distinct clinical and biochemical patterns of liver disease.
Question 318Question →

A physician is evaluating five patients who present with complex acid-base and electrolyte abnormalities. Match each patient's clinical and laboratory profile to the most likely underlying diagnosis. All serum electrolytes are reported in mEq/L. The reference range for serum anion gap is 8−128-12 mEq/L.

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Items

Patient A: pH 7.257.25, PaCO 2_2 3030 mmHg, Na +^+ 140140 mEq/L, K +^+ 2.12.1 mEq/L, Cl −^- 115115 mEq/L, HCO 3−_3^- 1313 mEq/L, Urine pH 6.86.8, Urine AG positive, BP 120/80120/80 mmHg
Patient B: pH 7.307.30, PaCO 2_2 3636 mmHg, Na +^+ 139139 mEq/L, K +^+ 5.85.8 mEq/L, Cl −^- 110110 mEq/L, HCO 3−_3^- 1717 mEq/L, Urine pH 5.25.2, Urine AG positive, BP 130/85130/85 mmHg
Patient C: pH 7.527.52, PaCO 2_2 4848 mmHg, Na +^+ 136136 mEq/L, K +^+ 2.62.6 mEq/L, Cl −^- 8686 mEq/L, HCO 3−_3^- 3838 mEq/L, Urine Cl −^- 88 mEq/L, BP 115/75115/75 mmHg
Patient D: pH 7.507.50, PaCO 2_2 4646 mmHg, Na +^+ 139139 mEq/L, K +^+ 2.52.5 mEq/L, Cl −^- 9292 mEq/L, HCO 3−_3^- 3535 mEq/L, Urine Cl −^- 6868 mEq/L, BP 110/70110/70 mmHg
Patient E: pH 7.517.51, PaCO 2_2 4747 mmHg, Na +^+ 142142 mEq/L, K +^+ 2.72.7 mEq/L, Cl −^- 9494 mEq/L, HCO 3−_3^- 3636 mEq/L, Urine Cl −^- 5555 mEq/L, BP 175/105175/105 mmHg

Matches

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Answer

Patient A matches with Distal (Type 1) RTA, Patient B with Hyporeninemic hypoaldosteronism, Patient C with Surreptitious vomiting, Patient D with Surreptitious loop diuretic abuse, and Patient E with Primary hyperaldosteronism.
Each patient requires a systemic approach to acid-base interpretation. Matching correctly relies on integrating multiple parameters: differentiating RTA types by potassium and urine pH, and evaluating metabolic alkalosis using urine chloride and blood pressure.

Step-by-Step Solution

1
Calculate the serum anion gap for acidotic patients
Patients A and B have a normal serum anion gap (1212 mEq/L), confirming hyperchloremic metabolic acidosis.
To classify the metabolic acidosis and determine if it is due to unmeasured anions or bicarbonate loss.
2
Evaluate potassium, urine anion gap, and urine pH in normal anion gap acidosis
Patient A has hypokalemia and urine pH >5.5> 5.5, indicating Type 11 RTA. Patient B has hyperkalemia and urine pH <5.5< 5.5, indicating Type 44 RTA.
To differentiate between renal tubular acidosis subtypes.
3
Analyze urine chloride in patients with metabolic alkalosis
Patient C has low urine Cl −^- (<20< 20 mEq/L), indicating saline-responsive alkalosis. Patients D and E have high urine Cl −^- (>20> 20 mEq/L), indicating saline-resistant alkalosis.
To determine volume status and chloride responsiveness.
4
Assess blood pressure in saline-resistant metabolic alkalosis
Patient D is normotensive, pointing to diuretic abuse. Patient E is hypertensive, pointing to primary hyperaldosteronism.
To distinguish between mineralocorticoid excess and renal salt-wasting states.

Key Concept

Interpretation of complex acid-base disorders requires algorithmic evaluation of the serum anion gap, potassium, urine pH, urine anion gap, urine chloride, and blood pressure to isolate the precise pathophysiological mechanism.
Question 319Question →

During bedside cardiovascular evaluation, several classic physical examination findings provide direct insight into underlying cardiopulmonary hemodynamics. Match the following peripheral pulse abnormalities or central venous pressure findings with their precise underlying pathophysiologic mechanism.

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Items

Pulsus paradoxus
Kussmaul sign
Pulsus bisferiens
Pulsus alternans

Matches

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Answer

Pulsus paradoxus matches with exaggerated interventricular dependence; Kussmaul sign matches with impaired right-sided cardiac compliance; Pulsus bisferiens matches with rapid initial ejection followed by a second systolic wave; and Pulsus alternans matches with beat-to-beat variation in stroke volume due to fluctuating contractility.
Each physical examination maneuver or finding evaluates a distinct hemodynamic variable. Matching these clinical signs with their corresponding mechanical and physiologic derangements ensures accurate bedside diagnosis and directs appropriate subsequent imaging or therapy.

Step-by-Step Solution

1
Analyze 'Pulsus paradoxus'.
It describes a drop in systolic blood pressure greater than 10 mmHg during inspiration.
This physical finding directly reflects exaggerated ventricular interdependence, typically seen in cardiac tamponade.
2
Analyze 'Kussmaul sign'.
It is a paradoxical increase (or lack of decrease) in jugular venous pressure on inspiration.
This points to a rigid, non-compliant right ventricle (e.g., constrictive pericarditis) that cannot expand to accommodate increased inspiratory venous return.
3
Analyze 'Pulsus bisferiens'.
It is a pulse with two palpable systolic peaks.
This occurs in conditions with rapid left ventricular ejection such as severe aortic regurgitation, leading to an initial percussion wave followed by a tidal wave.
4
Analyze 'Pulsus alternans'.
It manifests as alternating strong and weak pulse amplitudes despite a regular heart rhythm.
This is a classic physical exam finding of profound left ventricular systolic failure, representing beat-to-beat alterations in myocardial contractility.

Key Concept

Cardiovascular physical examination signs and their underlying hemodynamic pathophysiology.
Question 320Question →

A pathologist is reviewing biopsy specimens from four different patients who recently underwent neurosurgical resection of central nervous system masses. Match each specific microscopic description below with its most likely definitive pathologic diagnosis.

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Items

Densely cellular regions containing spindle cells with palisading nuclei, alternating with loosely textured, myxoid areas lacking significant cellularity.
Monomorphic cells demonstrating round nuclei and prominent perinuclear clear spaces, situated within a delicate, anastomosing capillary network.
Markedly pleomorphic cells featuring zones of serpiginous necrosis bordered by crowded tumor cells, accompanied by prominent endothelial cell hyperplasia.
Plump spindle cells arranged in tight, concentric syncytial whorls, accompanied by scattered laminated, basophilic calcifications.

Matches

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Answer

The biphasic spindle cell pattern matches Schwannoma; the perinuclear halo pattern matches Oligodendroglioma; the pseudopalisading necrosis pattern matches Glioblastoma; and the whorled pattern with calcifications matches Meningioma.
Each central nervous system tumor has distinct morphological features on biopsy. Accurate diagnosis requires matching these pathognomonic descriptors—such as Antoni areas for Schwannomas, 'fried egg' cells for Oligodendrogliomas, pseudopalisading necrosis for Glioblastomas, and whorls with psammoma bodies for Meningiomas—to their correct entities to guide surgical and oncological management.

Step-by-Step Solution

1
Analyze the first microscopic description focusing on cellularity patterns.
The alternating densely cellular and myxoid hypocellular areas with palisading nuclei describe Antoni A and B regions, identifying a Schwannoma.
Recognizing peripheral nerve sheath tumor morphology is essential for distinguishing benign masses from malignant intramedullary lesions.
2
Evaluate the second description highlighting cellular halos and vascular architecture.
The perinuclear clear spaces ('fried egg' cells) and anastomosing capillaries ('chicken-wire' pattern) specifically identify an Oligodendroglioma.
These classic fixation artifacts and vascular patterns are pathognomonic for this specific glial tumor.
3
Examine the third description for high-grade malignant features.
Serpiginous necrosis bordered by cells (pseudopalisading necrosis) and endothelial hyperplasia indicate a Grade IV astrocytoma, or Glioblastoma.
These specific features define the highest grade of astrocytic tumors, carrying severe prognostic implications.
4
Review the fourth description focusing on cellular arrangement and calcifications.
Concentric whorls of cells and laminated calcifications (psammoma bodies) are the hallmark features of a Meningioma.
Identifying these features confirms an extra-axial, typically benign tumor arising from the arachnoid cap cells.

Key Concept

Histopathological identification of primary central nervous system tumors.
Estimated Time:1m 30s
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