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Question 1601Question →

Match each clinical presentation or ultrasound/pathologic finding of abnormal placentation and bleeding with the corresponding obstetric diagnosis.

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Items

Ultrasound reveals an anterior placenta with an absent retroplacental clear space, and chorionic villi attaching directly to the superficial myometrium without penetration.
Pathologic examination of a postpartum hysterectomy specimen demonstrates chorionic villi invading deep into the muscularis layer of the uterus.
Intraoperative visualization during a repeat cesarean delivery shows placental tissue penetrating completely through the uterine serosa and extending into the posterior bladder wall.
Amniotomy is immediately followed by painless, bright red vaginal bleeding and sudden, profound fetal bradycardia displaying a sinusoidal heart rate pattern.
A patient presents with sudden-onset severe, tearing abdominal pain, dark vaginal bleeding, and a rigid, hypertonic uterus on physical examination.

Matches

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Answer

Placenta accreta matches with superficial myometrial attachment; Placenta increta matches with deep myometrial invasion; Placenta percreta matches with serosal/bladder penetration; Vasa previa matches with painless bleeding after amniotomy causing fetal bradycardia; Placental abruption matches with painful bleeding and a rigid uterus.
The matching correctly identifies the spectrum of placenta accreta (accreta, increta, percreta) based on the progressive depth of villous invasion from the superficial myometrium to adjacent organs. It also correctly distinguishes the painless, fetal-origin bleeding of vasa previa from the painful, maternal-origin bleeding of placental abruption.

Step-by-Step Solution

1
Evaluate the depth of placental invasion described in the pathologic or intraoperative findings.
Identifies the specific type of morbidly adherent placenta.
Accreta involves superficial attachment, increta involves myometrial invasion, and percreta involves full-thickness serosal penetration.
2
Assess the clinical presentation of third-trimester bleeding.
Differentiates vasa previa from placental abruption.
Painless bleeding immediately after membrane rupture with a sinusoidal fetal heart tracing indicates fetal blood loss from vasa previa. Painful bleeding with a hypertonic, rigid uterus indicates maternal blood loss and uterine irritability from placental abruption.

Key Concept

Differentiating etiologies of third-trimester bleeding and morbidly adherent placentation based on the depth of chorionic villi invasion and distinct clinical presentations.
Question 1602Question →

For each of the following individuals presenting after a potential infectious exposure, select the most appropriate guideline-concordant prophylactic regimen.

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Items

A 28-year-old nurse who sustained a deep, bloody needlestick injury from a patient with untreated HIV.
A 19-year-old university student who spent several hours studying in close proximity with a classmate newly diagnosed with meningococcal meningitis.
A 35-year-old camper who removed an engorged Ixodes scapularis tick from their leg after a 3-day camping trip in Connecticut.
A 12-year-old boy bitten on the finger by a bat found in his bedroom, which subsequently escaped out the window.

Matches

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Answer

The exposures match with their respective evidence-based prophylaxis protocols: the nurse exposed to HIV requires a 3-drug ART regimen for 28 days; the student exposed to meningococcus requires single-dose ciprofloxacin or ceftriaxone; the camper with a prolonged tick attachment requires single-dose doxycycline; and the boy bitten by a bat requires both rabies immune globulin and active vaccination.
Each specific exposure mechanism carries a well-defined risk for a particular pathogen, necessitating a targeted prophylactic approach. HIV exposure requires 28 days of triple-therapy ART. Meningococcal exposure requires clearance of nasopharyngeal carriage with agents like ciprofloxacin. Lyme disease prophylaxis requires a single dose of doxycycline when tick attachment exceeds 36 hours. Unprovoked bat bites require complete rabies post-exposure prophylaxis with both passive and active immunity.

Step-by-Step Solution

1
Identify the high-risk pathogen in each clinical scenario.
Pathogens identified: HIV (needlestick), Neisseria meningitidis (close contact), Borrelia burgdorferi (tick bite), and Rabies virus (bat bite).
Correct post-exposure prophylaxis depends entirely on the suspected pathogen and the mechanism of transmission.
2
Determine the guideline-recommended prophylactic regimen for each pathogen.
HIV requires 3-drug ART; meningococcus requires ciprofloxacin, rifampin, or ceftriaxone; Lyme requires single-dose doxycycline; Rabies requires HRIG + vaccine.
Applying established infectious disease guidelines minimizes the risk of overt disease progression while practicing appropriate antimicrobial stewardship.

Key Concept

Post-exposure prophylaxis (PEP) protocols for high-risk infectious exposures
Question 1603Question →

Pair each patient presentation with the most accurate acute surgical diagnosis.

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Items

A 45-year-old female presents with severe right upper quadrant pain radiating to the right shoulder, arrested inspiration upon deep palpation of the subcostal margin, and a temperature of 38.0°C (100.4°F).
A 22-year-old male reports dull periumbilical pain that migrated to the right lower quadrant over the past 24 hours, accompanied by profound anorexia and nausea.
A 68-year-old male with a history of chronic constipation presents with constant left lower quadrant abdominal pain, a fever of 38.5°C (101.3°F), and leukocytosis.
A 55-year-old male with chronic daily NSAID use presents with the sudden onset of diffuse, severe abdominal pain and a rigid, board-like abdomen on examination.

Matches

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Answer

The presentations map as follows: the 45-year-old female has acute cholecystitis, the 22-year-old male has acute appendicitis, the 68-year-old male has acute diverticulitis, and the 55-year-old male has a perforated peptic ulcer.
Each presentation describes the textbook hallmark symptoms of a specific acute abdominal emergency: right upper quadrant pain with a Murphy sign for acute cholecystitis, migrating periumbilical pain with anorexia for acute appendicitis, left lower quadrant pain in an older adult for acute diverticulitis, and sudden diffuse peritonitis with NSAID use for a perforated peptic ulcer.

Step-by-Step Solution

1
Analyze the location and radiation of pain in each presentation.
Identified right upper quadrant, migrating right lower quadrant, left lower quadrant, and diffuse abdominal pain locations.
Pain location is the primary differentiator for initially triaging acute abdominal pathologies.
2
Incorporate associated symptoms and patient risk factors for each vignette.
Noted Murphy sign for the gallbladder, anorexia for the appendix, age/constipation for diverticula, and NSAID use/rigidity for a perforation.
Associated features confirm the specific etiology suspected from the pain location.
3
Match the synthesized clinical picture to the corresponding standard diagnosis.
Successfully paired all four classic presentations.
Completes the matching requirement based on established surgical guidelines.

Key Concept

Classic clinical presentations of acute abdominal surgical emergencies
Question 1604Question →

A fundamental step in the evaluation of suspected autoimmune and inflammatory conditions of the gastrointestinal tract and liver is the identification of specific autoantibodies. Match each of the following clinical diagnoses with its most characteristic serologic marker.

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Items

Primary biliary cholangitis
Primary sclerosing cholangitis
Autoimmune hepatitis (Type 1)
Celiac disease

Matches

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Answer

Primary biliary cholangitis matches with Anti-mitochondrial antibody; Primary sclerosing cholangitis matches with p-ANCA; Autoimmune hepatitis (Type 1) matches with Anti-smooth muscle antibody; Celiac disease matches with Anti-tissue transglutaminase IgA.
Accurate diagnosis of autoimmune gastrointestinal and liver conditions relies heavily on specific serologic profiles. Anti-mitochondrial antibody is the hallmark of primary biliary cholangitis. p-ANCA is frequently positive in primary sclerosing cholangitis, which is closely linked to inflammatory bowel disease. Anti-smooth muscle antibody is characteristic of autoimmune hepatitis type 1. Finally, anti-tissue transglutaminase IgA is the most accurate initial test for celiac disease.

Step-by-Step Solution

1
Identify the characteristic autoantibody for primary biliary cholangitis.
Anti-mitochondrial antibody (AMA).
AMA is the hallmark serologic marker for diagnosing primary biliary cholangitis, an autoimmune destruction of small intrahepatic bile ducts.
2
Identify the characteristic autoantibody for primary sclerosing cholangitis.
Perinuclear anti-neutrophil cytoplasmic antibody (p-ANCA).
While not entirely specific, p-ANCA is found in the majority of patients with primary sclerosing cholangitis, reflecting its strong association with inflammatory bowel disease.
3
Identify the characteristic autoantibody for autoimmune hepatitis (Type 1).
Anti-smooth muscle antibody.
Type 1 autoimmune hepatitis typically presents with positive anti-smooth muscle antibodies and/or anti-nuclear antibodies.
4
Identify the characteristic autoantibody for celiac disease.
Anti-tissue transglutaminase IgA.
Anti-tissue transglutaminase IgA is the most sensitive and specific initial screening test for celiac disease.

Key Concept

Autoantibodies in gastrointestinal and hepatobiliary diseases
Question 1605Question →

Match the following clinical vignettes describing zoonotic and environmental infections with their most appropriate targeted antimicrobial therapy.

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Items

A 45-year-old livestock veterinarian with a 4-week history of undulating fevers, profound fatigue, night sweats, and hepatosplenomegaly.
A 34-year-old landscaper from Arkansas with sudden-onset fever and chills, followed by a demarcated ulcer on his right index finger and severe right axillary lymphadenopathy.
A 29-year-old triathlete with abrupt-onset high fever, severe calf myalgias, and marked conjunctival suffusion three days after a freshwater swimming event.
A 22-year-old veterinary technician with a localized papule on her forearm that progressed to tender, fluctuant epitrochlear lymphadenopathy over three weeks.
A 41-year-old wool sorter with a painless, pruritic macule on his forearm that rapidly enlarged into a central black eschar surrounded by extensive, non-pitting edema.

Matches

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Answer

Brucellosis matches with doxycycline and rifampin. Tularemia matches with gentamicin. Leptospirosis matches with intravenous penicillin G. Cat scratch disease matches with azithromycin. Cutaneous anthrax matches with ciprofloxacin.
Each clinical vignette provides highly specific occupational or environmental exposures paired with classic physical exam findings that uniquely identify a specific zoonotic bacterial pathogen. The correct pairings reflect the current gold standard first-line therapies for these respective pathogens based on their intrinsic sensitivities and intracellular characteristics.

Step-by-Step Solution

1
Analyze the veterinarian vignette.
Identified Brucellosis (undulating fever, hepatosplenomegaly).
Requires dual intracellular therapy to prevent relapse, matching with doxycycline and rifampin.
2
Analyze the landscaper vignette.
Identified ulceroglandular Tularemia.
Endemic to Arkansas/Missouri, presents with ulcer and massive adenopathy, matching with aminoglycosides like gentamicin.
3
Analyze the triathlete vignette.
Identified Leptospirosis.
Freshwater exposure, conjunctival suffusion, and calf pain are pathognomonic. Matches with intravenous penicillin G for systemic illness.
4
Analyze the veterinary technician vignette.
Identified Cat scratch disease (Bartonella henselae).
Subacute regional lymphadenopathy matches with the targeted macrolide therapy, azithromycin.
5
Analyze the wool sorter vignette.
Identified Cutaneous anthrax.
Painless black eschar with profound edema in a high-risk occupation matches with ciprofloxacin.

Key Concept

Diagnosis and targeted antimicrobial therapy of zoonotic and environmental bacterial infections.
Question 1606Question →

Match each clinical presentation in a patient who previously underwent bariatric surgery with the most likely diagnosis.

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Items

A 42-year-old woman presents with resting tachycardia (125/min), fever, and left shoulder pain on postoperative day 3 following a Roux-en-Y gastric bypass.
A 35-year-old man presents with intermittent, severe, crampy periumbilical pain and vomiting 18 months after a Roux-en-Y gastric bypass. CT of the abdomen reveals a 'swirl sign' of the mesenteric vessels.
A 40-year-old woman presents with colicky right upper quadrant pain, jaundice, and fever one year after a sleeve gastrectomy that resulted in a 40 kg (88 lb) weight loss.
A 48-year-old man who recently resumed smoking presents with severe epigastric pain and hematemesis 8 months after a Roux-en-Y gastric bypass.
A 30-year-old woman presents with palpitations, diaphoresis, and crampy abdominal pain occurring 20 minutes after eating a high-carbohydrate meal, 6 months after a Roux-en-Y gastric bypass.

Matches

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Answer

The correct pairings are: the day 3 patient with tachycardia and shoulder pain has an Anastomotic leak; the 18-month postoperative patient with a CT 'swirl sign' has an Internal hernia; the patient with rapid weight loss, jaundice, and fever has Choledocholithiasis; the smoking patient with hematemesis has a Marginal ulcer; and the patient with postprandial vasomotor symptoms has Early dumping syndrome.
Each clinical scenario maps uniquely to a specific post-bariatric complication based on the timeline, vital signs, radiographic findings, and patient risk factors.

Step-by-Step Solution

1
Analyze the onset timeframe of the complication for each patient.
Patient 1 is in the early postoperative phase (day 3), while the others present months to years after surgery.
Timing distinguishes early technical complications (like leaks) from late anatomical or metabolic complications.
2
Evaluate Patient 1's symptoms of resting tachycardia, fever, and referred shoulder pain.
Matches Anastomotic leak.
Tachycardia > 120/min is the most sensitive indicator of a leak; shoulder pain indicates peritonitis irritating the diaphragm.
3
Evaluate Patient 2's CT imaging finding ('swirl sign') and crampy pain.
Matches Internal hernia.
The Roux-en-Y anatomy creates mesenteric defects. Bowel herniation leads to volvulus, causing the classic 'swirl sign' of mesenteric vessels on CT.
4
Identify the risk factor in Patient 3 (rapid weight loss) alongside Charcot triad.
Matches Choledocholithiasis.
Rapid fat mobilization increases biliary cholesterol saturation, leading to gallstones and subsequent common bile duct obstruction/infection.
5
Assess Patient 4's risk factor (smoking) and symptom of upper gastrointestinal bleeding.
Matches Marginal ulcer.
Smoking causes mucosal ischemia at the gastrojejunal anastomosis, leading to ulceration, pain, and bleeding.
6
Connect Patient 5's diet-triggered autonomic symptoms with altered GI transit.
Matches Early dumping syndrome.
Bypassing the pylorus allows rapid transit of hyperosmolar food boluses, causing fluid shifts and sympathetic activation.

Key Concept

Post-bariatric surgery complications have distinct timelines (early vs. late) and specific clinical signatures (e.g., tachycardia for leak, swirl sign for internal hernia, diet-triggered autonomic symptoms for dumping syndrome) that dictate definitive management.
Estimated Time:1m 30s
Question 1607Question →

Match each brief clinical presentation of a hepatobiliary disorder to its most specific diagnostic laboratory or imaging finding.

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Items

A 45-year-old woman with Hashimoto thyroiditis presents with severe pruritus without a rash and progressive fatigue; laboratory studies show an isolated, significantly elevated alkaline phosphatase.
A 35-year-old man with a history of bloody diarrhea and tenesmus presents with jaundice and right upper quadrant aching; labs show an elevated alkaline phosphatase and mild transaminase elevation.
A 28-year-old woman presents with fatigue, amenorrhea, and jaundice; labs reveal an AST of 850 U/L, ALT of 920 U/L, and elevated total IgG levels.
A 54-year-old man presents with polyuria, polydipsia, erectile dysfunction, and generalized joint pains; physical examination reveals hyperpigmented skin.

Matches

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Answer

Primary Biliary Cholangitis matches with anti-mitochondrial antibodies; Primary Sclerosing Cholangitis matches with MRCP findings; Autoimmune Hepatitis matches with anti-smooth muscle antibodies; Hemochromatosis matches with elevated transferrin saturation.
Each vignette represents a classic presentation of a hepatobiliary disease. The middle-aged woman with pruritus and isolated elevated alkaline phosphatase has Primary Biliary Cholangitis (diagnosed via AMA). The man with ulcerative colitis and cholestasis has Primary Sclerosing Cholangitis (diagnosed via MRCP showing strictures). The young woman with severe transaminitis and hypergammaglobulinemia has Autoimmune Hepatitis (diagnosed via ASMA). The man with diabetes, skin pigmentation, and arthropathy has Hereditary Hemochromatosis (diagnosed via elevated transferrin saturation and HFE gene testing).

Step-by-Step Solution

1
Analyze each clinical vignette to establish the most likely underlying diagnosis based on demographics, symptoms, and initial lab patterns.
Identified diagnoses are Primary Biliary Cholangitis (PBC), Primary Sclerosing Cholangitis (PSC), Autoimmune Hepatitis (AIH), and Hereditary Hemochromatosis.
Accurate identification of the syndrome is a prerequisite to selecting the specific confirmatory test.
2
Match the cholestatic presentation in the middle-aged woman with autoimmune history to its serological marker.
The PBC vignette pairs with anti-mitochondrial antibodies.
AMA is highly sensitive and specific for PBC, which destroys small intrahepatic bile ducts.
3
Match the cholestatic presentation in the young man with inflammatory bowel disease to its diagnostic standard.
The PSC vignette pairs with multifocal stricturing and dilation on MRCP.
PSC affects medium and large bile ducts, leading to characteristic imaging findings that are required for diagnosis.
4
Match the severe hepatocellular injury presentation with high IgG to its associated autoantibodies.
The AIH vignette pairs with anti-smooth muscle antibodies and/or anti-nuclear antibodies.
AIH causes acute or chronic hepatocellular injury mediated by autoimmune mechanisms, marked by ASMA/ANA positivity.
5
Match the multi-system metabolic presentation (diabetes, skin changes, arthropathy) to its diagnostic markers.
The Hemochromatosis vignette pairs with elevated transferrin saturation and HFE gene mutation testing.
Hemochromatosis is an iron overload syndrome best screened initially with transferrin saturation and confirmed genetically.

Key Concept

Diagnostic markers for autoimmune and metabolic liver diseases
Question 1608Question →

Match the following primary bone lesions with their most characteristic clinical presentation and radiographic features.

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Items

Osteosarcoma
Ewing sarcoma
Osteoid osteoma
Giant cell tumor of bone
Osteochondroma

Matches

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Answer

Osteosarcoma pairs with the metaphyseal 'sunburst' lesion; Ewing sarcoma pairs with the diaphyseal 'onion-skin' lesion; Osteoid osteoma pairs with the NSAID-responsive nocturnal pain lesion; Giant cell tumor pairs with the epiphyseal 'soap bubble' lesion; and Osteochondroma pairs with the benign metaphyseal bony exostosis.
Primary bone tumors are diagnosed by combining patient age, exact location within the bone (epiphyseal, metaphyseal, or diaphyseal), and classic radiographic patterns (lytic, blastic, periosteal reactions).

Step-by-Step Solution

1
Analyze the anatomic location described in each clinical presentation.
Two lesions are metaphyseal (sunburst, exostosis), two can be diaphyseal (onion-skin, NSAID-responsive), and one is distinctly epiphyseal (soap bubble).
Location within the bone (epiphysis, metaphysis, diaphysis) is a primary distinguishing factor for primary bone tumors.
2
Match specific radiographic buzzwords and clinical symptoms to the appropriate diagnoses.
Sunburst/Codman = Osteosarcoma; Onion-skin/Fever = Ewing sarcoma; NSAID relief = Osteoid osteoma; Soap bubble = Giant cell tumor; Cartilage-capped spur = Osteochondroma.
These are highly conserved classic presentations essential for board exams.

Key Concept

Clinical and radiographic differentiation of primary bone tumors
Estimated Time:1m 30s
Question 1609Question →

Correlate each of the following lower extremity vascular assessment findings with their most likely underlying surgical or vascular pathology.

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Items

Noncompressible distal arteries yielding an ankle-brachial index >1.30 in an asymptomatic patient with diabetes mellitus.
Sudden onset of a painful, pale, and pulseless extremity in a patient with untreated atrial fibrillation.
Reproducible exertional calf cramping that resolves with rest, associated with an ankle-brachial index of 0.65.
A prominently pulsatile mass in the posterior knee fossa complicated by acute distal microembolization.

Matches

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Answer

The presentations match as follows: High ABI >1.30 indicates Medial arterial calcification; Acute painful and pulseless leg indicates Acute arterial thromboembolism; Exertional claudication with low ABI indicates Chronic atherosclerotic peripheral artery disease; Pulsatile knee mass with emboli indicates Popliteal artery aneurysm.
Each clinical scenario presents hallmark features of distinct vascular pathologies. Medial calcification presents with falsely elevated ABIs. Arterial embolism presents acutely with profound ischemia. Chronic peripheral artery disease presents insidiously with claudication and low ABIs. Popliteal aneurysms present as pulsatile masses frequently complicated by embolization.

Step-by-Step Solution

1
Analyze the first presentation: Ankle-brachial index >1.30 in a diabetic patient.
Identified as medial arterial calcification.
Vessel wall calcification prevents arterial compression by the blood pressure cuff, resulting in artificially high ABI measurements.
2
Analyze the second presentation: Sudden, painful, pale, pulseless leg in a patient with atrial fibrillation.
Identified as acute arterial thromboembolism.
Untreated atrial fibrillation predisposes patients to left atrial thrombus formation, which can embolize and acutely occlude distal arteries.
3
Analyze the third presentation: Exertional calf pain relieved by rest with an ankle-brachial index of 0.65.
Identified as chronic atherosclerotic peripheral artery disease.
This is the classic description of intermittent claudication resulting from chronic flow-limiting atherosclerotic stenoses.
4
Analyze the fourth presentation: Pulsatile popliteal mass with distal microembolization.
Identified as popliteal artery aneurysm.
The most common peripheral aneurysm occurs in the popliteal artery, and it often presents with ischemic complications due to distal embolization of intraluminal thrombus.

Key Concept

Differentiation of lower extremity vascular pathologies based on physical exam findings, hemodynamics, and patient risk factors.
Question 1610Question →

Match each clinical presentation following a recent acute myocardial infarction (left) with its precise underlying pathophysiologic mechanism and anatomical basis (right).

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Items

An individual rapidly develops profound cardiogenic shock and pulmonary edema on hospital day 4 following a delayed-presentation inferior STEMI. Physical examination is notable for a new, soft, early systolic apical murmur. Pulmonary artery catheterization reveals large, prominent 'v' waves in the capillary wedge pressure tracing.
Three days after an anteroseptal myocardial infarction, a patient abruptly develops hypotension, biventricular heart failure, and a new, harsh holosystolic murmur loudest at the left sternal border with an associated thrill. Oximetry run demonstrates a significant step-up in oxygen saturation between the right atrium and the right ventricle.
Five days post-infarction, a patient with a large transmural anterior STEMI experiences sudden-onset electromechanical dissociation (pulseless electrical activity). Emergent bedside echocardiography reveals a rapidly accumulating, large anechoic space surrounding the myocardium with diastolic bowing of the right ventricular free wall.
Four months after a large anterior myocardial infarction, a patient presents with symptoms of progressive heart failure and a transient ischemic attack. Electrocardiography demonstrates persistent ST-segment elevations in the anterior precordial leads without reciprocal changes. Echocardiography shows a thinned, dyskinetic segment at the apex with a broad base.

Matches

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Answer

The mechanical complications of acute myocardial infarction each present with distinct timing, hemodynamic profiles, and physical exam findings that directly reflect their underlying anatomical disruption. Posteromedial papillary muscle rupture causes acute mitral regurgitation (giant v waves); ventricular septal rupture causes a left-to-right shunt (oxygen step-up); free wall rupture causes rapid tamponade (PEA arrest); and true aneurysms cause persistent ST elevations and stasis (mural thrombus/emboli).
Each clinical vignette provides highly specific hemodynamic and physical exam clues that uniquely identify a post-infarction mechanical complication. The matches correctly link the clinical presentation (e.g., giant v waves, O2 step-up, PEA, dyskinetic pouch) to the exact pathophysiologic mechanism and anatomical defect responsible for the syndrome.

Step-by-Step Solution

1
Analyze the first clinical presentation (cardiogenic shock post-inferior STEMI, soft murmur, giant v waves).
Identify acute mitral regurgitation due to papillary muscle rupture.
The inferior location predisposes the posteromedial papillary muscle to ischemic rupture. The giant v waves and soft murmur are classic for acute, severe mitral regurgitation.
2
Analyze the second clinical presentation (biventricular failure post-anterior STEMI, harsh murmur with thrill, oxygen step-up).
Identify a ventricular septal rupture.
The harsh murmur with a thrill and the diagnostic oxygen saturation step-up between the right atrium and right ventricle confirm a new left-to-right intracardiac shunt.
3
Analyze the third clinical presentation (sudden PEA arrest post-transmural STEMI, anechoic space with right ventricular diastolic bowing).
Identify a left ventricular free wall rupture.
Sudden PEA arrest accompanied by echocardiographic evidence of rapidly accumulating pericardial fluid causing tamponade physiology points directly to a full-thickness myocardial tear.
4
Analyze the fourth clinical presentation (late heart failure and TIA, persistent ST elevations, broad-based dyskinetic segment).
Identify a true ventricular aneurysm.
The late presentation (months later), persistent ST-segment elevations, and embolic event from a broad-based outward bulging area of fibrotic myocardium are pathognomonic for a true aneurysm.

Key Concept

Mechanical complications of acute myocardial infarction (AMI)
Question 1611Question →

Match each characteristic electrocardiogram (ECG) description with its corresponding cardiovascular diagnosis.

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Items

Continuous 'sawtooth' baseline pattern without distinct P waves
Progressively lengthening PR interval culminating in a non-conducted (dropped) QRS complex
Short PR interval followed by a slurred upstroke of the QRS complex (delta wave)
Diffuse ST-segment elevations accompanied by PR-segment depressions

Matches

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Answer

The 'sawtooth' pattern matches atrial flutter, progressive PR lengthening matches Mobitz type I block, delta waves match Wolff-Parkinson-White syndrome, and diffuse ST elevations with PR depressions match acute pericarditis.
Each specific ECG description uniquely identifies the pathophysiology of its matched condition: atrial flutter involves a distinct macroreentrant atrial circuit; Mobitz type I involves reversible AV nodal fatigue; Wolff-Parkinson-White syndrome involves an accessory conduction pathway bypassing the AV node; and acute pericarditis involves diffuse epicardial and atrial inflammation.

Step-by-Step Solution

1
Analyze the baseline and P wave characteristics.
A 'sawtooth' baseline without normal P waves is identified as atrial flutter.
This pattern is uniquely produced by a rapid macroreentrant circuit in the atrium.
2
Evaluate the relationship between the P wave and the QRS complex.
A progressively lengthening PR interval followed by a dropped QRS represents Mobitz type I (Wenckebach) block.
This indicates reversible, progressive conduction delay and eventual failure at the AV node.
3
Examine the QRS complex morphology and PR interval duration.
A short PR interval with a slurred QRS upstroke (delta wave) identifies Wolff-Parkinson-White syndrome.
The accessory pathway bypasses the AV node, causing early, abnormal ventricular depolarization.
4
Assess ST segments and PR segments globally across the ECG.
Diffuse ST-segment elevations with PR-segment depressions confirm acute pericarditis.
Widespread inflammation affects the epicardium globally, distinguishing it from localized ischemia.

Key Concept

Characteristic electrocardiographic findings in common cardiovascular diseases
Estimated Time:1m 0s
Question 1612Question →

Match each clinical and neuroimaging presentation of a central nervous system disorder in patients with advanced HIV infection to its most appropriate definitive or empiric management.

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Items

A 3535-year-old male with a CD4 count of 8080 cells/mm 3^3 presents with a two-week history of severe headache, nausea, and neck stiffness. Cerebrospinal fluid analysis reveals a significantly elevated opening pressure and a positive latex agglutination test for a polysaccharide capsular antigen.
A 4242-year-old female with a CD4 count of 4545 cells/mm 3^3 develops progressive hemiparesis, cognitive impairment, and expressive aphasia over the past month. Brain magnetic resonance imaging reveals multiple asymmetric, non-enhancing white matter demyelinating lesions without mass effect or surrounding edema.
A 3939-year-old male with a CD4 count of 9090 cells/mm 3^3 is brought to the emergency department after a new-onset generalized tonic-clonic seizure. Brain magnetic resonance imaging with contrast demonstrates multiple small, ring-enhancing lesions predominantly located in the basal ganglia.
A 4545-year-old male with a CD4 count of 2525 cells/mm 3^3 presents with rapidly progressive confusion, apathy, and cranial nerve palsies. Brain magnetic resonance imaging shows distinct periventricular enhancement suggestive of ventriculitis.

Matches

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Answer

The presentations map to the following treatments: Cryptococcal meningitis requires amphotericin B and flucytosine; Progressive multifocal leukoencephalopathy (PML) requires optimization of antiretroviral therapy; Toxoplasmosis requires sulfadiazine, pyrimethamine, and leucovorin; Cytomegalovirus encephalitis requires ganciclovir or foscarnet.
Each central nervous system infection in advanced HIV has a distinct clinical and radiographic profile that dictates its specific management. Cryptococcal meningitis is characterized by elevated intracranial pressure and is treated with amphotericin B and flucytosine. Toxoplasmosis presents with multiple ring-enhancing lesions and responds to sulfadiazine and pyrimethamine. JC virus causes progressive multifocal leukoencephalopathy (non-enhancing white matter lesions) and is managed solely by reversing immunosuppression with antiretroviral therapy. Cytomegalovirus causes ventriculitis and must be treated with targeted agents like ganciclovir or foscarnet.

Step-by-Step Solution

1
Analyze the first clinical vignette involving elevated opening pressure and a positive polysaccharide antigen test.
Identify the pathogen as Cryptococcus neoformans.
The polysaccharide capsule is characteristic of Cryptococcus, which typically presents with subacute meningitis and elevated intracranial pressure in patients with CD4 counts below 100100 cells/mm 3^3.
2
Evaluate the second vignette detailing non-enhancing white matter lesions without edema.
Identify the condition as progressive multifocal leukoencephalopathy (PML) caused by the JC virus.
PML causes asymmetric demyelination without mass effect in severely immunocompromised hosts, distinguishing it from space-occupying lesions.
3
Examine the third vignette describing seizures and multiple ring-enhancing lesions in the basal ganglia.
Identify the etiology as Toxoplasma gondii.
Toxoplasmosis is the most common cause of ring-enhancing brain lesions in patients with advanced HIV and frequently presents with seizures and focal neurologic deficits.
4
Assess the fourth vignette featuring rapid neurologic decline and periventricular enhancement.
Identify the pathogen as Cytomegalovirus (CMV).
CMV encephalitis typically presents with ventriculitis and cranial nerve neuropathies in patients with CD4 counts typically less than 5050 cells/mm 3^3.
5
Match each identified infectious etiology to its guideline-directed management.
Cryptococcus pairs with amphotericin B and flucytosine. PML pairs with antiretroviral therapy. Toxoplasmosis pairs with sulfadiazine and pyrimethamine. CMV pairs with ganciclovir or foscarnet.
Survival and recovery depend on utilizing the pathogen-specific antimicrobial or immune reconstitution strategy indicated for each distinct central nervous system infection.

Key Concept

Identifying opportunistic central nervous system infections in advanced HIV based on CD4 count, clinical presentation, and neuroimaging to determine the targeted pharmacotherapy.
Question 1613Question →

Evaluate the following clinical vignettes describing patients who developed acute kidney injury (AKI) in various clinical settings. Match each patient's clinical presentation to the most accurate pathophysiological diagnosis.

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Items

A 68-year-old man with heart failure undergoes aggressive diuresis with intravenous furosemide. He develops AKI with a BUN of 72 mg/dL and a creatinine of 2.4 mg/dL. Urinalysis shows abundant hyaline casts.
A 55-year-old woman with decompensated cirrhosis develops oliguria and a creatinine of 3.1 mg/dL. Urine sodium is 6 mEq/L. Renal function does not improve after 48 hours of intravenous albumin therapy and diuretic withdrawal.
A 60-year-old man undergoes a contrast-enhanced CT scan. Two days later, his serum creatinine increases from 1.0 mg/dL to 2.2 mg/dL. Urinalysis shows granular casts, and the fractional excretion of sodium (FENa) is 0.6%.
A 72-year-old man undergoes coronary angiography. Five days later, he develops AKI, a purplish mottling on his feet, and new-onset peripheral eosinophilia. Urinalysis reveals eosinophils.

Matches

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Answer

The presentations map to distinct mechanisms: overdiuresis causes classic prerenal azotemia, cirrhosis with albumin-unresponsive AKI represents hepatorenal syndrome, post-contrast AKI is contrast-induced nephropathy (notable for FENa < 1%), and post-angiography AKI with livedo reticularis is atheroembolic renal disease.
The correct matches rely on synthesizing the patient history with specific diagnostic markers. Furosemide diuresis predictably shrinks the effective arterial blood volume, leading to a classic prerenal pattern characterized by a high BUN/Cr ratio and hyaline casts. Hepatorenal syndrome is distinguished from simple prerenal azotemia by its complete failure to improve after withdrawing diuretics and administering a dedicated volume expansion trial with intravenous albumin. Contrast-induced nephropathy represents a toxic injury to the tubules, but unlike classic ischemic acute tubular necrosis (which typically exhibits a FENa > 2%), the profound vasoconstrictive effect of the contrast media classically yields a FENa < 1%. Finally, atheroembolic renal disease is distinguished by its delayed onset (days to weeks post-procedure) alongside systemic signs of crystal embolization, such as livedo reticularis, blue toe syndrome, and eosinophilia.

Step-by-Step Solution

1
Evaluate the temporal context and inciting events for the acute kidney injury in each vignette.
Recent interventions include massive diuresis (first patient), progressive cirrhosis (second patient), iodinated contrast administration (third patient), and an invasive endovascular catheterization (fourth patient).
Establishing the precise clinical context acts as the primary branching logic in determining the etiology of acute kidney injury.
2
Analyze the accompanying physical examination signs and specific laboratory indices (urinalysis, FENa, urine sodium) for each presentation.
The first patient demonstrates a highly elevated BUN/Cr ratio with hyaline casts; the second shows fluid-unresponsiveness with severely depressed urine sodium; the third shows granular casts but a paradoxically low FENa (< 1%); the fourth displays cutaneous manifestations (livedo reticularis) and eosinophilia.
Urine indices and systemic signs separate etiologies that might otherwise present with similar temporal profiles, confirming the specific pathophysiologic mechanism.

Key Concept

Differentiating etiologies of acute kidney injury requires recognizing classic clinical contexts and appropriately interpreting urine indices, while maintaining high suspicion for exceptions such as contrast nephropathy, which typically presents with a FENa < 1%.
Estimated Time:2m 0s
Question 1614Question →

Match each patient's hepatitis B (HBV) serology profile with the most appropriate clinical diagnosis.

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Items

HBsAg negative, Anti-HBs positive, Anti-HBc (total) positive
HBsAg positive, HBeAg positive, Anti-HBc IgM positive, Anti-HBs negative
HBsAg negative, Anti-HBs positive, Anti-HBc (total) negative
HBsAg positive, Anti-HBc IgG positive, Anti-HBe positive, persistently normal ALT

Matches

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Answer

Profile 1 matches Resolved past HBV infection. Profile 2 matches Acute HBV infection. Profile 3 matches Immunity due to HBV vaccination. Profile 4 matches Inactive chronic HBV carrier.
Accurate interpretation of HBV serology relies on evaluating HBsAg (active infection vs. immunity), Anti-HBc (natural exposure vs. vaccination), and HBeAg/Anti-HBe status (infectivity and replication). The matched pairs correctly align these serological principles with their respective clinical phases.

Step-by-Step Solution

1
Analyze the HBsAg status for each profile.
Profiles 2 and 4 are HBsAg positive (active infection). Profiles 1 and 3 are HBsAg negative (no active infection).
HBsAg is the hallmark of active viral presence, distinguishing active disease from immunity or past infection.
2
Differentiate the HBsAg positive profiles (2 and 4).
Profile 2 has Anti-HBc IgM, indicating acute infection. Profile 4 has Anti-HBc IgG and Anti-HBe with normal ALT, indicating an inactive chronic carrier.
IgM antibodies represent acute or recent exposure, while IgG represents chronic or remote exposure.
3
Differentiate the HBsAg negative profiles (1 and 3).
Profile 1 has Anti-HBc (total) positive, indicating natural exposure and resolved infection. Profile 3 has Anti-HBc negative, indicating immunity from vaccination.
The HBV vaccine contains only HBsAg; therefore, vaccinated individuals will only develop Anti-HBs. Natural infection exposes the immune system to all viral proteins, leading to Anti-HBc production.

Key Concept

Interpretation of Hepatitis B virus (HBV) serological markers for disease staging
Estimated Time:1m 0s
Question 1615Question →

High-resolution manometry (HRM) is the gold standard for diagnosing esophageal motility disorders. According to the Chicago Classification v4.0, match the following esophageal motility disorders with their precise defining manometric criteria.

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Items

Type I Achalasia
Type II Achalasia
Type III Achalasia
Distal Esophageal Spasm
Hypercontractile (Jackhammer) Esophagus

Matches

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Answer

Type I Achalasia matches with elevated IRP, 100% failed peristalsis, and no pressurization. Type II Achalasia matches with elevated IRP, 100% failed peristalsis, and pan-esophageal pressurization. Type III Achalasia matches with elevated IRP and premature contractions. Distal Esophageal Spasm matches with normal IRP and premature contractions. Hypercontractile Esophagus matches with normal IRP and a DCI > 8,000 mmHg·s·cm.
The correct matches strictly follow the Chicago Classification algorithm for esophageal motility disorders. The first critical metric is the IRP. Achalasia requires an elevated IRP, while DES and Jackhammer require a normal IRP. Once IRP is established, the contractility pattern (failed, pressurized, premature, or hypercontractile) differentiates the specific subtype.

Step-by-Step Solution

1
Evaluate the Integrated Relaxation Pressure (IRP) to determine lower esophageal sphincter (LES) function.
An elevated IRP indicates impaired LES relaxation (defining achalasia), while a normal IRP rules out achalasia.
This primary branching point separates achalasia (Types I, II, and III) from other motility disorders (DES, Jackhammer).
2
Assess the contractility pattern in the esophageal body for cases with an elevated IRP.
100% failed peristalsis without pressurization is Type I. 100% failed peristalsis with pan-esophageal pressurization is Type II. Premature contractions indicate Type III.
The distinct contractility patterns dictate the achalasia subtype, which influences the choice of therapy (e.g., Type II responds best to pneumatic dilation or myotomy, while Type III often requires a longer myotomy).
3
Assess the contractility pattern in cases with a normal IRP.
Premature contractions with normal IRP define Distal Esophageal Spasm. Extremely high vigor contractions (DCI > 8,000) with normal IRP define Hypercontractile (Jackhammer) Esophagus.
Separating these prevents inappropriate achalasia treatments for patients with functioning LES relaxation.

Key Concept

Diagnosis and classification of esophageal motility disorders using high-resolution manometry criteria.
Estimated Time:2m 0s
Question 1616Question →

Match the following patient presentations with the most likely underlying pathophysiologic mechanism of their hematologic abnormality.

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Items

A 32-year-old woman presents with altered mental status, fever, and petechiae. Labs show hemoglobin 7.5 g/dL, platelets 22,000/mm³, and creatinine 2.4 mg/dL. Peripheral smear shows schistocytes. PT and PTT are normal.
A 48-year-old man admitted for gram-negative sepsis develops diffuse oozing from his intravenous catheter sites. Labs show platelets 35,000/mm³, prolonged PT and PTT, and decreased fibrinogen.
A 24-year-old healthy woman presents with heavy menstrual bleeding and petechiae on her lower extremities. Labs show hemoglobin 11.8 g/dL, platelets 15,000/mm³, and normal PT and PTT. Peripheral smear shows large platelets without schistocytes.
A 62-year-old woman with chronic lymphocytic leukemia presents with new-onset fatigue and scleral icterus. Labs show hemoglobin 8.2 g/dL, elevated indirect bilirubin, and elevated LDH. Peripheral smear shows spherocytes.

Matches

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Answer

The correct matches are: the patient with the TTP pentad matches with ADAMTS13 deficiency; the patient with DIC matches with consumption of coagulation factors; the patient with ITP matches with anti-glycoprotein IIb/IIIa autoantibodies; and the patient with AIHA matches with IgG-coated red blood cell destruction.
Each vignette represents a distinct hematologic pathophysiology. TTP results from ADAMTS13 deficiency, allowing large von Willebrand factor multimers to shear red blood cells and consume platelets. DIC involves systemic activation of the coagulation cascade, depleting clotting factors and causing prolonged PT/PTT. ITP is an autoimmune destruction of platelets mediated by anti-glycoprotein IIb/IIIa antibodies without affecting the coagulation cascade. Warm AIHA is the antibody-mediated destruction of red blood cells, often producing spherocytes on a peripheral smear, and is frequently associated with lymphoid malignancies like CLL.

Step-by-Step Solution

1
Analyze the first clinical vignette for diagnostic clues.
Identified the presence of microangiopathic hemolytic anemia (MAHA), thrombocytopenia, renal impairment, and altered mental status with normal coagulation times.
These findings represent the classic pentad of Thrombotic Thrombocytopenic Purpura (TTP), which is caused by a deficiency in the ADAMTS13 protease.
2
Analyze the second clinical vignette for diagnostic clues.
Identified thrombocytopenia accompanied by prolonged PT and PTT, and low fibrinogen in the setting of severe infection (sepsis).
These laboratory derangements indicate consumption of coagulation factors, confirming the diagnosis of Disseminated Intravascular Coagulation (DIC).
3
Analyze the third clinical vignette for diagnostic clues.
Identified isolated thrombocytopenia without hemolysis and with normal coagulation studies in an otherwise healthy young adult.
This presentation is characteristic of Immune Thrombocytopenic Purpura (ITP), where autoantibodies target platelet surface antigens.
4
Analyze the fourth clinical vignette for diagnostic clues.
Identified extravascular hemolysis (jaundice, indirect hyperbilirubinemia, spherocytes) in a patient with underlying chronic lymphocytic leukemia.
These findings point to Warm Autoimmune Hemolytic Anemia (AIHA), caused by IgG autoantibodies binding to red blood cell surface antigens.

Key Concept

Differentiation of bleeding and hemolytic disorders based on peripheral smear findings and coagulation panels.
Question 1617Question →

Match each patient's clinical presentation of chronic diarrhea to the underlying pathophysiologic mechanism that best explains their symptoms.

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Items

A 52-year-old man presents with chronic diarrhea, weight loss, migratory polyarthralgia, and generalized lymphadenopathy. Small bowel biopsy reveals PAS-positive, diastase-resistant inclusions in the lamina propria.
A 48-year-old woman with a history of progressive systemic sclerosis develops chronic postprandial bloating, steatorrhea, and macrocytic anemia despite adequate dietary intake.
A 60-year-old woman presents with months of chronic, nonbloody watery diarrhea. Colonoscopy reveals grossly normal mucosa, but biopsy shows increased intraepithelial lymphocytes without a thickened subepithelial band.
A 55-year-old man experiences profuse, voluminous watery diarrhea that persists during a 48-hour fasting trial. Laboratory studies show profound hypokalemia and a non-anion gap metabolic acidosis.
A 65-year-old woman describes episodic severe abdominal cramping, watery diarrhea, and facial flushing triggered by alcohol consumption, accompanied by a new-onset holosystolic murmur at the left lower sternal border.

Matches

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Answer

The correct pairings link each specific clinical presentation of chronic diarrhea to its defining pathophysiologic mechanism, matching unique historical and histologic clues to underlying disease processes.
Each clinical vignette provides distinctive historical and diagnostic clues that point to a unique cause of chronic diarrhea. Whipple disease is identified by PAS-positive macrophages; SIBO is identified by the combination of dysmotility, steatorrhea, and macrocytic anemia; Lymphocytic colitis is diagnosed by biopsy showing intraepithelial lymphocytosis; VIPoma presents with secretory diarrhea and hypokalemia; and Carcinoid syndrome features systemic flushing and right heart valvular lesions.

Step-by-Step Solution

1
Analyze the patient with diarrhea, arthralgia, and PAS-positive macrophages in the lamina propria.
This identifies Whipple disease, which impairs absorption via macrophage infiltration.
Identifying the specific histologic hallmark of Tropheryma whipplei maps directly to its infiltrative mechanism.
2
Evaluate the systemic sclerosis patient with steatorrhea and macrocytic anemia.
This indicates small intestinal bacterial overgrowth (SIBO).
Systemic sclerosis causes dysmotility, allowing microbial overgrowth that deconjugates bile acids and consumes vitamin B12.
3
Review the presentation of watery diarrhea with normal endoscopy but increased intraepithelial lymphocytes.
This defines lymphocytic microscopic colitis.
Differentiating this from collagenous colitis relies on the specific absence of a subepithelial collagen band.
4
Examine the case of profuse secretory diarrhea persisting during fasting with severe hypokalemia.
This points to a VIPoma (Verner-Morrison syndrome).
Vasoactive intestinal peptide ectopic production drives cAMP-mediated chloride secretion.
5
Assess the patient with episodic flushing, diarrhea, and a right-sided heart murmur.
This is characteristic of carcinoid syndrome.
Systemic serotonin release bypassing the liver causes right heart valvular fibrosis and vasomotor symptoms.

Key Concept

The pathophysiology of distinct chronic diarrhea syndromes.
Question 1618Question →

Match the following calcium and parathyroid hormone (PTH) laboratory profiles with their most likely underlying etiologies.

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Items

Serum calcium 11.211.2 mg/dL, intact PTH 8585 pg/mL (high), 24-hour urine calcium 350350 mg/day (high)
Serum calcium 12.512.5 mg/dL, intact PTH 88 pg/mL (low), elevated parathyroid hormone-related peptide (PTHrP)
Serum calcium 11.011.0 mg/dL, intact PTH 5555 pg/mL (upper normal), urine calcium/creatinine clearance ratio <0.01<0.01
Serum calcium 8.28.2 mg/dL, intact PTH 120120 pg/mL (high), 25-hydroxyvitamin D 99 ng/mL (low)

Matches

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Answer

The correct matches are: Profile 1 pairs with Primary hyperparathyroidism; Profile 2 pairs with Humoral hypercalcemia of malignancy; Profile 3 pairs with Familial hypocalciuric hypercalcemia; and Profile 4 pairs with Secondary hyperparathyroidism due to vitamin D deficiency.
Correctly matching these profiles requires evaluating the integrity of the parathyroid axis. When calcium is elevated, PTH should normally be suppressed. If PTH is high or inappropriately normal, the process is PTH-dependent (e.g., primary hyperparathyroidism or FHH). FHH must be distinguished from primary hyperparathyroidism by finding profound hypocalciuria due to a mutated calcium-sensing receptor. If PTH is suppressed, the hypercalcemia is PTH-independent, and the presence of elevated PTHrP points directly to a malignant etiology. Conversely, low calcium should appropriately stimulate PTH secretion; a concurrent low 25-hydroxyvitamin D level identifies secondary hyperparathyroidism as the underlying cause.

Step-by-Step Solution

1
Evaluate the first laboratory profile.
The profile shows hypercalcemia, an elevated PTH, and hypercalciuria.
An elevated PTH in the setting of hypercalcemia indicates that the parathyroid glands are functioning autonomously rather than responding to physiological feedback. The resulting high filtered load of calcium causes hypercalciuria, confirming primary hyperparathyroidism.
2
Evaluate the second laboratory profile.
The profile reveals hypercalcemia with suppressed PTH and elevated PTHrP.
The suppressed PTH demonstrates intact physiological negative feedback from the hypercalcemia. The presence of PTHrP indicates that an ectopic source (e.g., squamous cell carcinoma) is driving the hypercalcemia, confirming humoral hypercalcemia of malignancy.
3
Evaluate the third laboratory profile.
The profile demonstrates hypercalcemia, an inappropriately normal PTH, and profound hypocalciuria (calcium/creatinine clearance ratio <0.01).
This pattern mimics primary hyperparathyroidism but is distinguished by the very low urine calcium excretion. It confirms familial hypocalciuric hypercalcemia (FHH), which results from a defective calcium-sensing receptor.
4
Evaluate the fourth laboratory profile.
The profile displays low calcium, elevated PTH, and low 25-hydroxyvitamin D.
The low vitamin D level leads to decreased intestinal calcium absorption. The parathyroid glands respond appropriately to the resulting low serum calcium by secreting more PTH, confirming secondary hyperparathyroidism.

Key Concept

Differential diagnosis of calcium and parathyroid disorders based on the relationship between serum calcium, intact PTH, and urinary calcium excretion.
Question 1619Question →

Match each disease-modifying antirheumatic drug (DMARD) or immunosuppressive agent to its most characteristic adverse effect or required screening protocol.

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Items

Hydroxychloroquine
Etanercept
Methotrexate
Cyclophosphamide

Matches

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Answer

Hydroxychloroquine matches with macular toxicity; Etanercept matches with latent tuberculosis reactivation; Methotrexate matches with hepatotoxicity and cytopenias; Cyclophosphamide matches with hemorrhagic cystitis.
Each immunosuppressive medication has a unique toxicity profile that dictates specific pre-treatment screening and ongoing monitoring. Safe long-term management of rheumatologic diseases requires pairing the drug with its classic adverse effect.

Step-by-Step Solution

1
Analyze Hydroxychloroquine's toxicity profile.
Identified as causing retinal toxicity (bull's-eye maculopathy).
Hydroxychloroquine binds to melanin in the retinal pigment epithelium, necessitating routine ophthalmologic screening.
2
Analyze Etanercept's mechanism and screening requirements.
Identified as a TNF inhibitor that risks TB reactivation.
TNF-alpha is required to maintain granulomas. Inhibiting it requires ruling out latent tuberculosis prior to initiation.
3
Analyze Methotrexate's mechanism of action and side effects.
Identified as a folate analog causing mucosal and hepatic toxicity.
Inhibiting dihydrofolate reductase disrupts rapidly dividing cells. Folic acid supplementation prevents stomatitis and transaminitis.
4
Analyze Cyclophosphamide's specific metabolic byproducts.
Identified acrolein as the cause of hemorrhagic cystitis.
Acrolein is excreted in the urine and is directly toxic to the bladder urothelium.

Key Concept

Pharmacologic adverse effects and required monitoring for disease-modifying antirheumatic drugs (DMARDs)
Estimated Time:1m 30s
Question 1620Question →

Match each clinical vignette and laboratory profile with the most likely underlying etiology of the patient's acid-base disorder.

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Items

A 42-year-old woman with Sjögren syndrome presents with profound weakness. Labs: Na+Na^+ 139139 mEq/L, K+K^+ 2.12.1 mEq/L, Cl−Cl^- 114114 mEq/L, HCO3−HCO_3^- 1414 mEq/L. Urine pH is 6.56.5 and the urine anion gap is positive.
A 58-year-old man with light chain cast nephropathy presents with bone pain. Labs: Na+Na^+ 140140 mEq/L, K+K^+ 2.92.9 mEq/L, Cl−Cl^- 112112 mEq/L, HCO3−HCO_3^- 1616 mEq/L. Serum glucose is 9595 mg/dL. Urinalysis shows 3+ glucose and a pH of 5.35.3.
A 64-year-old man with diabetic nephropathy presents for routine follow-up. Labs: Na+Na^+ 138138 mEq/L, K+K^+ 5.95.9 mEq/L, Cl−Cl^- 109109 mEq/L, HCO3−HCO_3^- 1919 mEq/L. Urine pH is 5.25.2 and the urine anion gap is positive.
A 29-year-old woman with an extensive ileal resection presents with fatigue. Labs: Na+Na^+ 137137 mEq/L, K+K^+ 2.82.8 mEq/L, Cl−Cl^- 113113 mEq/L, HCO3−HCO_3^- 1212 mEq/L. Urine pH is 5.05.0 and the urine anion gap is negative.

Matches

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Answer

Patient 1 matches with Type 1 RTA; Patient 2 matches with Type 2 RTA; Patient 3 matches with Type 4 RTA; Patient 4 matches with Gastrointestinal bicarbonate loss.
Normal anion gap metabolic acidosis is differentiated primarily by serum potassium and the urine anion gap. Hyperkalemia points to Type 4 RTA. Hypokalemia with a negative UAG points to GI loss. Hypokalemia with a positive UAG and high urine pH points to Type 1 RTA. Hypokalemia with signs of generalized proximal dysfunction (like normoglycemic glycosuria) points to Type 2 RTA.

Step-by-Step Solution

1
Calculate the serum anion gap for each patient using the formula Na+−(Cl−+HCO3−)Na^+ - (Cl^- + HCO_3^-) to categorize the metabolic acidosis.
All four patients have an anion gap between 1010 and 1212 mEq/L, indicating a normal anion gap metabolic acidosis (NAGMA).
This calculation narrows the differential diagnosis to either a renal tubular acidosis (RTA) or gastrointestinal bicarbonate loss.
2
Evaluate the serum potassium levels for all patients.
Patients 1, 2, and 4 have hypokalemia, whereas patient 3 has hyperkalemia (K+K^+ 5.95.9 mEq/L).
Hyperkalemia in the setting of a NAGMA is highly specific for Type 4 RTA, which is caused by aldosterone deficiency or resistance. This isolates the diagnosis for patient 3.
3
Analyze the urine anion gap (UAG) in the hypokalemic patients.
Patient 4 has a negative UAG, while patient 1 has a positive UAG.
A negative UAG indicates that the kidneys are appropriately excreting acid (as ammonium chloride), pointing to extrarenal (gastrointestinal) bicarbonate loss, confirming patient 4's diagnosis. A positive UAG indicates impaired renal acid excretion, pointing to an RTA.
4
Differentiate between Type 1 and Type 2 RTA using urine pH and additional proximal tubule markers.
Patient 1 cannot acidify the urine (pH >5.5>5.5), indicating distal (Type 1) RTA. Patient 2 has intact distal acidification (pH <5.5<5.5) but shows isolated glycosuria, a sign of proximal tubule dysfunction.
The inability to secrete hydrogen ions distally confirms Type 1 RTA. Proximal tubule defects (like Fanconi syndrome) leading to bicarbonate wasting characterize Type 2 RTA.

Key Concept

Differentiation of Normal Anion Gap Metabolic Acidosis (NAGMA) using serum potassium, urine pH, and the urine anion gap.
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