All practice questions

Question 581Question →

A $78$ -year-old woman is evaluated in the hospital for worsening renal function. She was admitted $4$ days ago for acute decompensated heart failure and has been receiving aggressive intravenous bumetanide therapy. Over the past $24$ hours, her urine output has decreased to $300\text{ mL}$ . On physical examination, her blood pressure is $105/65\text{ mmHg}$ and pulse is $92/\text{min}$ . Jugular venous pressure is undetectable, and her lungs are clear to auscultation. Laboratory studies are obtained:

Test	Result
Serum
Sodium	$140\text{ mEq/L}$
Blood urea nitrogen	$50\text{ mg/dL}$
Creatinine	$2.5\text{ mg/dL}$ (baseline $1.1\text{ mg/dL}$ )
Urine
Sodium	$112\text{ mEq/L}$
Urea nitrogen	$500\text{ mg/dL}$
Creatinine	$100\text{ mg/dL}$

Based on the laboratory values, calculate the fractional excretion of urea ( $FE_{Urea}$ ) as a percentage to help determine the etiology of her acute kidney injury.

Show answer & explanation

Answer: 25

Answer

25

The fractional excretion of urea (FEUrea) is calculated using the formula:

FE_{Urea} = \frac{U_{Urea} \times P_{Cr}}{P_{Urea} \times U_{Cr}} \times 100

. Substituting the patient's laboratory values yields:

\frac{500 \times 2.5}{50 \times 100} \times 100 = \frac{1250}{5000} \times 100 = 25\%

. In patients receiving loop or thiazide diuretics, FEUrea is the preferred diagnostic metric over FeNa. Diuretics directly inhibit sodium reabsorption in the loop of Henle or distal convoluted tubule, artificially elevating urinary sodium and falsely increasing FeNa (in this patient, FeNa is calculated to be

2\%

). However, urea reabsorption occurs primarily in the proximal tubule and is largely unaffected by these diuretics. An

FE_{Urea} < 35\%

strongly suggests prerenal AKI, which perfectly aligns with this patient's clinical picture of over-diuresis (undetectable jugular venous pressure, cleared lungs, and relative hypotension).

Step-by-Step Solution

1

Assess the clinical scenario to choose the correct diagnostic calculation.

Determine that FEUrea should be used instead of FeNa.

The patient is actively receiving a loop diuretic (bumetanide), which artificially increases urinary sodium excretion and renders FeNa unreliable for diagnosing prerenal AKI.

2

Set up the Fractional Excretion of Urea (FEUrea) formula.

FE_{Urea} = \frac{U_{Urea} \times P_{Cr}}{P_{Urea} \times U_{Cr}} \times 100

This formula compares the clearance of urea to the clearance of creatinine to assess proximal tubular reabsorption.

3

Substitute the patient's laboratory values into the formula.

FE_{Urea} = \frac{500 \times 2.5}{50 \times 100} \times 100

Accurate placement of serum and urine values is necessary to perform the calculation.

4

Perform the arithmetic calculation.

FE_{Urea} = \frac{1250}{5000} \times 100 = 0.25 \times 100 = 25\%

To obtain the final percentage required by the question format.

Key Concept

In patients receiving loop diuretics, the Fractional Excretion of Urea (FEUrea) is a more reliable indicator than FeNa for distinguishing between prerenal AKI and intrinsic AKI. An FEUrea < 35% indicates a prerenal etiology.

Estimated Time:1m 30s

Question 582Question →

A triage nurse urgently calls a physician to evaluate an $80$ -year-old man who was just brought to the hospital by his son. The son reports that the patient suddenly developed excruciating abdominal pain two hours ago but now appears extremely lethargic and confused. The patient has a history of medication nonadherence for his paroxysmal atrial fibrillation. On physical examination, the abdomen is soft and non-tender to deep palpation. He is tachypneic with deep, rapid respirations.

Initial laboratory studies show:
Serum $\text{Na}^+$ : $140 \text{ mEq/L}$
Serum $\text{Cl}^-$ : $100 \text{ mEq/L}$
Serum $\text{HCO}_3^-$ : $10 \text{ mEq/L}$

Arterial blood gas analysis on room air reveals a pH of $7.22$ and a $\text{pCO}_2$ of $23 \text{ mm Hg}$ .

Based on these findings, which of the following is the most accurate description of this patient's acid-base status?

High anion gap metabolic acidosis with appropriate respiratory compensation

High anion gap metabolic acidosis with a concurrent primary respiratory alkalosis

High anion gap metabolic acidosis with a concurrent primary respiratory acidosis

Normal anion gap metabolic acidosis with appropriate respiratory compensation

Primary respiratory alkalosis with appropriate metabolic compensation

Show answer & explanation

Answer: High anion gap metabolic acidosis with appropriate respiratory compensation

Answer

High anion gap metabolic acidosis with appropriate respiratory compensation

This patient presents with a primary metabolic acidosis, evidenced by a pH of 7.22 and a low serum bicarbonate of 10 mEq/L. The next step in any metabolic acidosis is to calculate the anion gap:

140 - (100 + 10) = 30 \text{ mEq/L}

. An anion gap greater than 12 indicates a high anion gap metabolic acidosis (HAGMA), which in this patient's clinical context (pain out of proportion to exam, atrial fibrillation off anticoagulation) is highly suspicious for lactic acidosis secondary to acute mesenteric ischemia. Finally, Winter's formula (

\text{Expected pCO}_2 = 1.5 \times [\text{HCO}_3^-] + 8 \pm 2

) is applied to check for a mixed disorder. Calculating

(1.5 \times 10) + 8

yields an expected

\text{pCO}_2

of

23 \text{ mm Hg}

. Because the patient's measured

\text{pCO}_2

is exactly

23 \text{ mm Hg}

, the respiratory compensation is appropriate, meaning there is no superimposed secondary respiratory disorder.

Step-by-Step Solution

1

Determine the primary acid-base disorder by looking at the pH and bicarbonate.

The pH is 7.22 (acidemia) and the serum bicarbonate is low at 10 mEq/L, confirming a primary metabolic acidosis.

Acidemia (pH < 7.35) combined with a matched drop in bicarbonate defines a primary metabolic acidosis.

2

Calculate the serum anion gap.

\text{Anion Gap} = \text{Na}^+ - (\text{Cl}^- + \text{HCO}_3^-) = 140 - (100 + 10) = 30 \text{ mEq/L}

.

Determining if the anion gap is normal (8-12 mEq/L) or elevated (>12 mEq/L) restricts the differential diagnosis. Here, the gap is highly elevated, indicating the presence of unmeasured anions (likely lactate due to acute mesenteric ischemia).

3

Calculate the expected respiratory compensation using Winter's formula.

\text{Expected pCO}_2 = (1.5 \times \text{HCO}_3^-) + 8 \pm 2 = (1.5 \times 10) + 8 = 23 \pm 2 \text{ mm Hg}

.

Winter's formula evaluates whether the patient's respiratory response (hyperventilation) is adequate for the degree of metabolic acidosis.

4

Compare the measured pCO2 to the expected pCO2.

The measured

\text{pCO}_2

is

23 \text{ mm Hg}

, which falls perfectly within the expected range (

21-25 \text{ mm Hg}

).

Because the measured value matches the expected value, there is no superimposed secondary respiratory disorder (neither concurrent respiratory acidosis nor alkalosis).

Key Concept

Evaluation of acid-base disorders using the anion gap calculation and Winter's formula.

Question 583Question →

Six months after a complicated vaginal delivery, a $29$ -year-old woman presents for evaluation of profound exhaustion and cold intolerance. Her obstetrical history is significant for a severe postpartum hemorrhage that necessitated emergency uterine artery embolization and multiple blood transfusions. Since the delivery, she has experienced persistent amenorrhea and was entirely unable to lactate. Vital signs include a blood pressure of $92/58\ \text{mmHg}$ and a heart rate of $58/\text{min}$ . On examination, there is noticeable thinning of the lateral eyebrows, loss of axillary hair, and delayed relaxation of the ankle jerk reflexes. Routine blood work reveals the following:

Laboratory Test	Result	Reference Range
Thyroid-stimulating hormone (TSH)	$1.2\ \mu\text{U/mL}$	$0.5 - 5.0\ \mu\text{U/mL}$
Free thyroxine (T4)	$0.6\ \text{ng/dL}$	$0.9 - 1.7\ \text{ng/dL}$

Based on these findings, which of the following is the most accurate pathophysiologic explanation for this patient's thyroid laboratory abnormalities?

Inadequate anterior pituitary stimulation of the thyroid gland

Autoimmune-mediated destruction of the thyroid follicles

Decreased peripheral conversion of thyroxine to triiodothyronine

Decreased hepatic synthesis of thyroxine-binding globulin

Peripheral tissue resistance to circulating thyroid hormones

Show answer & explanation

Answer: Inadequate anterior pituitary stimulation of the thyroid gland

Answer

Inadequate anterior pituitary stimulation of the thyroid gland

The correct pathophysiologic mechanism is inadequate anterior pituitary stimulation of the thyroid gland. This patient's clinical presentation (severe postpartum hemorrhage requiring transfusion, failure to lactate, amenorrhea, and fatigue) is highly characteristic of Sheehan syndrome, which is ischemic necrosis of the anterior pituitary gland. The laboratory findings confirm secondary (central) hypothyroidism: the free T4 is low, but the TSH is inappropriately normal. The damaged pituitary gland is unable to produce sufficient thyrotropin (TSH) to stimulate the structurally normal thyroid gland.

Step-by-Step Solution

1

Analyze the patient's clinical history and physical examination findings.

The patient has a history of severe postpartum hemorrhage followed by failure to lactate, amenorrhea, fatigue, and signs of hypothyroidism (delayed reflexes, thinning eyebrows) and adrenal/gonadal insufficiency (loss of axillary hair, hypotension).

Identifying the clinical syndrome points toward panhypopituitarism, specifically Sheehan syndrome (ischemic necrosis of the pituitary gland).

2

Interpret the thyroid function laboratory tests in the context of the clinical picture.

The free T4 is distinctly low (

0.6\ \text{ng/dL}

), confirming a hypothyroid state. However, the TSH is

1.2\ \mu\text{U/mL}

, which is within the normal reference range.

In primary hypothyroidism, a low free T4 triggers a massive compensatory increase in TSH. An inappropriately normal or low TSH in the setting of low free T4 defines central (secondary) hypothyroidism.

3

Determine the pathophysiologic mechanism for the identified laboratory pattern.

The damaged anterior pituitary gland is unable to secrete adequate amounts of TSH to stimulate the thyroid gland.

This leads directly to the conclusion that inadequate anterior pituitary stimulation is the cause of the patient's central hypothyroidism.

Key Concept

Secondary (central) hypothyroidism is characterized by a low free T4 level with an inappropriately normal or low TSH, often due to pituitary pathology such as Sheehan syndrome.

Estimated Time:1m 0s

Question 584Question →

Match each antihyperglycemic medication with its primary mechanism of action.

Click a left item, then click its matching right item

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Answer

Metformin decreases hepatic gluconeogenesis; Empagliflozin blocks proximal tubule glucose reabsorption; Semaglutide enhances glucose-dependent insulin secretion; Glimepiride stimulates ATP-sensitive potassium channels on beta cells.

Each listed medication represents a distinct class of antidiabetic drugs with a unique physiological target. Metformin (a biguanide) acts on the liver to reduce glucose output. Empagliflozin (an SGLT2 inhibitor) acts on the kidneys to induce glycosuria. Semaglutide (a GLP-1 agonist) mimics incretin hormones to enhance glucose-dependent insulin release. Glimepiride (a sulfonylurea) functions as an insulin secretagogue by binding to potassium channels on beta cells.

Step-by-Step Solution

1

Identify the pharmacologic class for each listed antihyperglycemic agent.

Metformin is a biguanide, empagliflozin is an SGLT2 inhibitor, semaglutide is a GLP-1 agonist, and glimepiride is a sulfonylurea.

Knowing the drug class is the foundational step in recalling its mechanism of action.

2

Correlate each identified drug class with its specific physiological target.

Biguanides target the liver (gluconeogenesis), SGLT2 inhibitors target the kidneys (proximal tubule), GLP-1 agonists target the incretin pathway, and sulfonylureas target pancreatic beta cells.

This confirms the correct pairing between the medication and the mechanism.

Key Concept

Pharmacotherapy for Type 2 Diabetes Mellitus

Question 585Question →

Match each clinical exposure scenario with the most appropriate definitive post-exposure prophylaxis (PEP) or management regimen based on current clinical guidelines.

Click a left item, then click its matching right item

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Answer

Each specific high-risk exposure must be matched with its respective post-exposure prophylaxis protocol, differentiating when both passive (immune globulin) and active (vaccine) immunity are necessary versus when antimicrobial therapy is indicated.

Correct matching relies on understanding that undocumented or inadequate immunization status necessitates both active and passive immunity (Tetanus, Rabies, HBV). High-risk occupational exposures to respiratory droplets require brief bacterial eradication (ciprofloxacin for Neisseria), whereas high-risk bloodborne viral exposures require prolonged viral suppression (28 days of ART for HIV).

Step-by-Step Solution

1

Analyze the pathogen risk and the host's current immune status for each scenario.

Identified risks include HIV, Tetanus, Meningococcus, Hepatitis B, and Rabies. Noted that the farm worker is unvaccinated, and the HBV-exposed worker has an inadequate titer (< 10 mIU/mL).

Host immunity determines whether active vaccination alone is sufficient or if passive immune globulin is also required.

2

Determine the requirement for dual therapy (vaccine + Ig) in the scenarios.

The dirty wound in an unvaccinated host, the bat exposure with unrecognized bite risk, and the HBV exposure in a non-responder all require both vaccine and their respective specific immune globulins.

Immediate circulating antibodies (Ig) are needed to neutralize the pathogen while the host's immune system mounts a response to the active vaccine.

3

Select the appropriate antimicrobial regimens for the remaining exposures.

The HIV needlestick requires a 28-day course of triple-drug ART. The meningococcal exposure (intubation) requires a single dose of ciprofloxacin.

Viral suppression is critical for HIV PEP, requiring a full 28-day multi-drug course, whereas eradicating meningococcal carriage requires only a single dose of a targeted antibiotic.

Key Concept

Post-exposure prophylaxis (PEP) protocols require assessing the specific pathogen risk and host immunity to determine the need for antimicrobials, vaccines, or immune globulins.

Question 586Question →

A 24-year-old man is brought to the emergency department by paramedics after being found unresponsive in his garage. An open bottle of antifreeze was found nearby. His temperature is $36.5^\circ\text{C}$ ( $97.7^\circ\text{F}$ ), blood pressure is $110/70\text{ mm Hg}$ , pulse is $112\text{/min}$ , and respirations are $28\text{/min}$ and deep. Physical examination reveals a comatose patient with no focal neurologic deficits.

Laboratory studies show the following:
Serum sodium: $138\text{ mEq/L}$
Serum potassium: $5.0\text{ mEq/L}$
Serum chloride: $104\text{ mEq/L}$
Serum bicarbonate: $10\text{ mEq/L}$
Blood urea nitrogen: $14\text{ mg/dL}$
Serum creatinine: $1.2\text{ mg/dL}$
Serum glucose: $90\text{ mg/dL}$
Measured serum osmolality: $315\text{ mOsm/kg H}_2\text{O}$

Arterial blood gas on room air:
pH: $7.20$
pCO $_2$ : $24\text{ mm Hg}$
pO $_2$ : $95\text{ mm Hg}$

What is this patient's serum osmolar gap? (Enter the value only)

Show answer & explanation

Answer: 29

Answer

The patient's serum osmolar gap is 29 mOsm/kg.

The serum osmolar gap is calculated by subtracting the calculated serum osmolality from the measured serum osmolality. The calculated serum osmolality is

2 \times [Na^+] + \frac{[Glucose]}{18} + \frac{[BUN]}{2.8}

. For this patient, the calculated osmolality is

2 \times 138 + \frac{90}{18} + \frac{14}{2.8} = 286 \text{ mOsm/kg}

. The osmolar gap is

315 - 286 = 29 \text{ mOsm/kg}

. A normal osmolar gap is typically less than 10 mOsm/kg. An elevated osmolar gap in the setting of a high anion gap metabolic acidosis is highly suggestive of toxic alcohol ingestion (e.g., ethylene glycol or methanol).

Step-by-Step Solution

1

Identify the need to calculate the osmolar gap.

The patient has a high anion gap metabolic acidosis and suspected toxic alcohol ingestion, which requires calculation of the osmolar gap to support the diagnosis.

Ethylene glycol and methanol are unmeasured osmotically active substances that increase the osmolar gap.

2

Calculate the expected serum osmolality.

Expected Osmolality =

2 \times 138 + \frac{90}{18} + \frac{14}{2.8} = 276 + 5 + 5 = 286 \text{ mOsm/kg H}_2\text{O}

.

The calculated serum osmolality accounts for the primary normal osmotically active solutes in the blood: sodium, glucose, and urea.

3

Calculate the osmolar gap.

Osmolar Gap = Measured Osmolality - Calculated Osmolality =

315 - 286 = 29 \text{ mOsm/kg}

.

The difference between measured and calculated osmolality represents the concentration of unmeasured osmoles (e.g., ethylene glycol).

Key Concept

The serum osmolar gap is used to detect the presence of unmeasured osmotically active substances (such as toxic alcohols) in the blood. It is calculated as the difference between the measured serum osmolality and the calculated serum osmolality.

Estimated Time:1m 30s

Question 587Question →

A $72$ -year-old woman is evaluated on hospital day $4$ for worsening renal function. She was admitted for acute decompensated heart failure and has been receiving intravenous furosemide. Over the past $48$ hours, her weight has decreased by $4.5\text{ kg}$ , but her urine output has dropped to $300\text{ mL}$ over the last $12$ hours. Her blood pressure is $95/60\text{ mmHg}$ and heart rate is $102\text{/min}$ . Laboratory studies show:

Lab	Value
Serum sodium	$136\text{ mEq/L}$
Serum blood urea nitrogen (BUN)	$75\text{ mg/dL}$
Serum creatinine	$2.5\text{ mg/dL}$ (baseline $1.1\text{ mg/dL}$ )
Urine sodium	$110\text{ mEq/L}$
Urine urea nitrogen	$450\text{ mg/dL}$
Urine creatinine	$100\text{ mg/dL}$

What is this patient's fractional excretion of urea ( $FE_{Urea}$ )? (Express the answer as a percentage).

Show answer & explanation

Answer: 15

Answer

15

The correct answer is

15\%

. This patient presents with acute kidney injury (AKI) in the setting of aggressive diuresis for heart failure. Distinguishing between prerenal azotemia (hypovolemia) and intrinsic renal disease (such as acute tubular necrosis) is critical for her ongoing management. While the fractional excretion of sodium (

FE_{Na}

) is typically less than

1\%

in prerenal AKI, loop diuretics directly inhibit sodium reabsorption, causing a falsely elevated

FE_{Na}

(in this patient's case, it would be calculated as roughly

2.02\%

). In patients on active diuretic therapy, the fractional excretion of urea (

FE_{Urea}

) is a much more accurate diagnostic marker because urea reabsorption is closely linked to proximal tubule water reabsorption and is significantly less affected by loop diuretics. An

FE_{Urea}

of less than

35\%

strongly suggests prerenal azotemia. The calculation is performed as follows:

FE_{Urea} = \frac{U_{Urea} \times P_{Cr}}{P_{Urea} \times U_{Cr}} \times 100 = \frac{450 \times 2.5}{75 \times 100} \times 100 = \frac{1125}{7500} \times 100 = 15\%

.

Step-by-Step Solution

1

Evaluate the clinical scenario and the limitation of standard AKI diagnostic indices.

Identify that the patient's active furosemide use falsely elevates sodium excretion, making FE_Na inaccurate (calculated here as 2.02%).

Loop diuretics inhibit sodium reabsorption in the thick ascending limb of the loop of Henle, invalidating FE_Na as a marker for volume status.

2

Select the appropriate diagnostic calculation for patients on diuretics.

Use the Fractional Excretion of Urea (FE_Urea).

Urea reabsorption occurs primarily in the proximal tubule and is less affected by loop diuretics. An FE_Urea < 35% reliably indicates a prerenal state.

3

Apply the FE_Urea formula.

FE_Urea = (Urine Urea_nitrogen * Serum Creatinine) / (Serum BUN * Urine Creatinine) * 100

This formula compares the clearance of urea to the clearance of creatinine to determine the fraction of filtered urea that is ultimately excreted.

4

Substitute the provided laboratory values into the formula.

(450 * 2.5) / (75 * 100) * 100 = 1125 / 7500 * 100

Accurate substitution of variables is required to solve the clearance ratio.

5

Perform the final calculation.

0.15 * 100 = 15%

To express the fractional excretion as a percentage.

Key Concept

In patients receiving active diuretic therapy, the fractional excretion of urea (FE_Urea) is a more reliable indicator of prerenal azotemia than the fractional excretion of sodium (FE_Na).

Question 588Question →

Correlate the following clinical patient profiles with their most likely underlying systemic rheumatologic diagnosis and associated extra-articular complication.

Click a left item, then click its matching right item

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Answer

The correct matches link each distinct clinical presentation to its classic extra-articular or systemic complication. The patient with erosive arthritis and neutropenia matches Rheumatoid arthritis with Felty syndrome. The patient with bamboo spine and a diastolic murmur matches Ankylosing spondylitis with aortic regurgitation. The patient with oro-genital ulcers and ascites matches Behçet disease with Budd-Chiari syndrome. The patient with a heliotrope rash and bibasilar crackles matches Dermatomyositis with interstitial lung disease. Finally, the patient with sclerodactyly and elevated pulmonary pressure matches Limited cutaneous systemic sclerosis with pulmonary arterial hypertension.

Each rheumatologic condition has highly specific systemic manifestations. Felty syndrome requires a background of RA; aortic root disease is a well-known cardiac complication of ankylosing spondylitis; Budd-Chiari syndrome reflects the hypercoagulable state of Behçet disease; interstitial lung disease is heavily linked to dermatomyositis (especially anti-Jo-1 positive); and pulmonary arterial hypertension is a classic complication of limited cutaneous systemic sclerosis.

Step-by-Step Solution

1

Analyze the first vignette to identify the underlying disease (erosive polyarthritis) and complication (neutropenia and splenomegaly).

Identified as Rheumatoid Arthritis with Felty syndrome.

The combination of severe RA, splenomegaly, and neutropenia definitively establishes the diagnosis of Felty syndrome.

2

Analyze the second vignette focusing on the combination of sacroiliitis (bamboo spine) and a new diastolic murmur.

Identified as Ankylosing Spondylitis with aortic root dilation and regurgitation.

Aortitis leading to aortic regurgitation is a classic extra-articular manifestation of HLA-B27 spondyloarthropathies.

3

Evaluate the third vignette describing oral and genital ulcers accompanied by hepatic vein thrombosis.

Identified as Behçet disease causing Budd-Chiari syndrome.

Behçet disease is characterized by mucosal ulcerations and a significant risk of venous thrombosis, including rare sites such as the hepatic vein.

4

Assess the fourth vignette featuring proximal muscle weakness, heliotrope rash, and new-onset respiratory symptoms.

Identified as Dermatomyositis complicated by interstitial lung disease.

Patients with dermatomyositis, particularly those positive for anti-Jo-1, have a high incidence of rapidly progressive interstitial lung disease.

5

Examine the fifth vignette detailing CREST features and elevated pulmonary pressures without left heart failure.

Identified as Limited Cutaneous Systemic Sclerosis with pulmonary arterial hypertension.

Pulmonary arterial hypertension is a leading cause of mortality in limited systemic sclerosis and is confirmed via right heart catheterization.

Key Concept

Identifying life-threatening extra-articular complications of common systemic rheumatologic diseases.

Question 589Question →

Correlate the following patient presentations with their most characteristic histopathologic finding on renal biopsy.

Click a left item, then click its matching right item

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Answer

Lupus nephritis matches with 'wire loops'; malignancy-associated nephrotic syndrome matches with 'spike and dome'; synpharyngitic hematuria matches with mesangial IgA deposition; post-impetigo nephritic syndrome matches with subepithelial 'humps'; and Hepatitis C-associated renal disease matches with 'tram-track' appearance.

Each clinical vignette provides classic demographic and historical clues for specific glomerular diseases. Identifying the underlying etiology allows for direct correlation with its pathognomonic renal biopsy findings.

Step-by-Step Solution

1

Identify the underlying glomerular disease for each clinical vignette.

The vignettes describe Diffuse Proliferative Glomerulonephritis (DPGN), Membranous Nephropathy, IgA Nephropathy, Poststreptococcal Glomerulonephritis (PSGN), and Membranoproliferative Glomerulonephritis (MPGN), respectively.

Accurately diagnosing the clinical syndrome based on timing, patient demographics, and associated systemic symptoms is a prerequisite to predicting the biopsy findings.

2

Correlate each identified glomerular disease with its characteristic light, immunofluorescence, or electron microscopy findings.

DPGN -> wire loops; Membranous -> spike and dome; IgA -> mesangial IgA deposits; PSGN -> subepithelial humps; MPGN -> tram-track appearance.

USMLE Step 2 CK expects integration of clinical presentations with classic pathophysiologic and histopathologic anchors.

Key Concept

Glomerular Disease Histopathology and Clinical Correlations

Question 590Question →

A $42$ -year-old woman is brought to the emergency department by her husband due to progressive confusion, lethargy, and a low-grade fever over the past $24$ hours. She has no significant past medical history. Her temperature is $37.8^\circ\text{C}$ ( $100.0^\circ\text{F}$ ), blood pressure is $142/88$ mmHg, and pulse is $105$ /min. Physical examination reveals petechiae on her lower extremities and scleral icterus. Neurologic examination shows a lethargic patient who is oriented only to person.

Laboratory studies show:

Test	Result
Hemoglobin	$8.2$ g/dL
Platelets	$22,000$ /mm $^3$
Leukocytes	$8,500$ /mm $^3$
Creatinine	$1.8$ mg/dL
Total bilirubin	$3.2$ mg/dL
Indirect bilirubin	$2.8$ mg/dL
Lactate dehydrogenase	$850$ U/L

Arrange the following steps in the most appropriate chronological order for the management of this patient.

Drag items to arrange them in the correct order

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Answer

The correct sequence is: 1) Perform a peripheral blood smear to identify schistocytes, 2) Obtain a baseline blood sample for ADAMTS13 activity, 3) Initiate emergent therapeutic plasma exchange (PEX), and 4) Monitor platelet count and lactate dehydrogenase (LDH) daily to assess treatment response.

The patient's presentation of thrombocytopenia, hemolytic anemia, renal dysfunction, neurologic changes, and fever is highly suggestive of Thrombotic Thrombocytopenic Purpura (TTP). The first step is to confirm microangiopathic hemolytic anemia (MAHA) via a peripheral blood smear showing schistocytes. Once MAHA and thrombocytopenia are confirmed without another obvious cause, a presumptive diagnosis of TTP is made. Before administering any plasma, a blood sample for ADAMTS13 activity must be drawn, as donor plasma will alter baseline levels. Following this, therapeutic plasma exchange (PEX) must be initiated emergently. It is the primary life-saving treatment and should not be delayed while awaiting ADAMTS13 results. Finally, the patient's response to PEX and adjunctive immunosuppression is monitored daily by following the platelet count and LDH levels.

Step-by-Step Solution

1

Identify the clinical syndrome

Suspected Thrombotic Thrombocytopenic Purpura (TTP)

The patient presents with the classic pentad: fever, neurologic changes, thrombocytopenia, hemolytic anemia, and renal dysfunction.

2

Select the initial diagnostic test

Peripheral blood smear

Visualizing schistocytes confirms microangiopathic hemolytic anemia (MAHA), establishing the presumptive diagnosis of TTP.

3

Identify the necessary pre-treatment laboratory draw

ADAMTS13 activity and inhibitor assay

Blood must be drawn before giving donor plasma to accurately measure the patient's baseline enzyme activity.

4

Select the emergent definitive therapy

Therapeutic plasma exchange (PEX)

PEX removes autoantibodies and replenishes ADAMTS13; it must be started immediately without waiting for confirmatory assay results.

5

Determine the follow-up monitoring strategy

Daily monitoring of platelets and LDH

These markers indicate the resolution of microthrombi and hemolysis, guiding the duration of PEX.

Key Concept

Sequential management of suspected Thrombotic Thrombocytopenic Purpura (TTP)

Estimated Time:1m 30s

Question 591Question →

A 4-day-old male neonate is brought to the emergency department due to poor feeding, vomiting, and progressive unresponsiveness over the past 12 hours. He was born at 39 weeks gestation via uncomplicated vaginal delivery and was discharged on day 2 of life feeding well. On examination, the infant is comatose, hypothermic (35.4°C), and tachypneic. While being examined, he develops generalized tonic-clonic seizure activity. Initial laboratory evaluation reveals:

Sodium: 140 mEq/L
Potassium: 4.5 mEq/L
Chloride: 105 mEq/L
Bicarbonate: 22 mEq/L
Blood urea nitrogen: 4 mg/dL
Creatinine: 0.3 mg/dL
Glucose: 55 mg/dL
Arterial blood gas: pH 7.52, pCO2 25 mmHg, pO2 95 mmHg
Plasma ammonia: 1,250 µmol/L (normal: 15-50 µmol/L)

Arrange the following management steps in the most appropriate sequential order for this patient.

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Answer

The correct sequence is: (1) endotracheal intubation, (2) discontinue feeds and start IV dextrose, (3) draw diagnostic labs, (4) administer IV nitrogen scavengers, (5) initiate emergency hemodialysis.

In a severe neonatal metabolic crisis presenting with extreme hyperammonemia (indicative of a Urea Cycle Defect given the respiratory alkalosis and normal anion gap), management must follow strict emergency protocols. The airway must be secured first due to coma and seizures. Next, the catabolic state must be reversed by stopping protein and giving dextrose. Diagnostic labs must then be drawn, because subsequent treatments will erase the biochemical evidence needed for a definitive diagnosis. After labs are secured, medical therapies (scavengers) are initiated because they are readily available. Finally, preparation for emergency hemodialysis is completed, which is the definitive treatment for ammonia levels this high (>1,000 µmol/L) but takes the longest to physically initiate.

Step-by-Step Solution

1

Assess clinical stability and prioritize ABCs (Airway, Breathing, Circulation).

Identify that the comatose and seizing neonate requires immediate endotracheal intubation to protect the airway.

Neurologic compromise from cerebral edema impairs airway protective reflexes and respiratory drive.

2

Address the immediate pathophysiologic driver (hyperammonemia).

Discontinue breast milk/formula (protein source) and provide high-concentration IV dextrose.

Halting protein intake and providing carbohydrates stimulates insulin release, shifting the body from a catabolic state (breaking down internal proteins, releasing ammonia) to an anabolic state.

3

Secure diagnostic integrity before definitive treatment.

Draw plasma amino acids, urine organic acids, and acylcarnitine profile.

Once nitrogen scavengers or dialysis are started, the specific metabolic signature required to diagnose the exact enzyme deficiency (e.g., Ornithine Transcarbamylase deficiency) will be washed out.

4

Initiate medical therapy for hyperammonemia.

Administer sodium benzoate, sodium phenylacetate, and arginine.

These medications provide alternative pathways for nitrogen excretion and prime the urea cycle; they can be pushed quickly via IV.

5

Initiate definitive mechanical clearance of ammonia.

Perform emergency hemodialysis.

Ammonia levels >500 µmol/L in a neonate correlate with severe brain edema and poor neurologic outcomes. Hemodialysis is the fastest way to clear ammonia but takes time to set up, placing it at the end of the immediate stabilization sequence.

Key Concept

Acute management of neonatal hyperammonemic crisis prioritizes airway stabilization, reversal of catabolism, collection of diagnostic labs prior to treatment, pharmacologic scavenging, and finally, emergency hemodialysis for extreme levels.

Question 592Question →

Match the following pediatric clinical vignettes, characterized by distinctive electrocardiographic (ECG) or chest radiograph (CXR) findings, to their most likely underlying congenital cardiovascular diagnosis.

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Answer

The correct pairings align specific imaging and ECG findings with their respective pathologies: Left axis deviation in a cyanotic newborn indicates Tricuspid atresia; a superior QRS axis in a Down syndrome patient indicates a Complete atrioventricular septal defect; the 'snowman' sign indicates Total anomalous pulmonary venous return; and a boot-shaped heart indicates Tetralogy of Fallot.

Each congenital heart defect has distinct anatomical and hemodynamic consequences that manifest as highly specific electrocardiographic and radiographic patterns. Recognizing these classic diagnostic associations is crucial for rapid identification and management in pediatric cardiology.

Step-by-Step Solution

1

Analyze the first vignette describing a cyanotic neonate with left axis deviation and left ventricular hypertrophy.

Matches with Tricuspid atresia.

Normal newborns typically have right axis deviation and right ventricular dominance. The presence of left ventricular hypertrophy in a cyanotic newborn is highly specific for tricuspid atresia, as the right ventricle is hypoplastic.

2

Evaluate the second vignette describing a dysmorphic infant (Down syndrome features) with a superior QRS axis on ECG.

Matches with Complete atrioventricular septal defect.

This is the most common congenital heart defect in patients with Down syndrome. The abnormal displacement of the AV node causes early activation of the posteroinferior left ventricle, resulting in the classic superior QRS axis.

3

Examine the third vignette describing the 'snowman' sign on a chest radiograph.

Matches with Total anomalous pulmonary venous return.

In the supracardiac variant of TAPVR, the anomalous vertical vein and dilated innominate vein form the upper loop of the 'snowman' above the normal cardiac shadow.

4

Assess the final vignette describing a boot-shaped heart with decreased pulmonary vascular markings.

Matches with Tetralogy of Fallot.

Right ventricular hypertrophy tilts the apex of the heart upward, while hypoplasia of the pulmonary outflow tract creates a concavity, perfectly producing the 'coeur en sabot' or boot-shaped heart.

Key Concept

Classic Electrocardiographic and Radiographic Findings in Congenital Heart Disease

Question 593Question →

A 10-day-old male neonate is evaluated in the pediatric orthopedics clinic for bilateral foot abnormalities present since birth. The pregnancy was uncomplicated, and he was born at term via spontaneous vaginal delivery. On physical examination, both feet exhibit deep medial creases, plantar flexion of the ankles, inversion of the heels, and medial deviation of the forefeet. The deformities are rigid and cannot be passively manipulated into a neutral position. There are no dimples over the sacrum, and lower extremity reflexes are normal. The physician discusses the standard evidence-based, nonoperative management protocol with the parents. Arrange the following steps of the standard treatment protocol for this patient's condition in the correct chronological sequence.

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Answer

The correct sequence for the Ponseti method is: 1) Initiation of weekly manual manipulation and serial long-leg plaster casting, 2) Percutaneous Achilles tenotomy, 3) Application of a final long-leg cast, and 4) Maintenance therapy with a foot abduction orthosis.

Congenital talipes equinovarus (clubfoot) is characterized by four primary deformities: cavus, adductus, varus, and equinus (CAVE). The gold standard of treatment is the Ponseti method, which must be performed in a highly specific sequence to safely and effectively correct the foot. The process begins with gentle manual manipulation and serial long-leg plaster casting, changed weekly for 4 to 6 weeks, to correct the cavus, adductus, and varus components. Once these are corrected, the equinus deformity typically remains. Because the Achilles tendon is severely contracted, it strongly resists stretching, necessitating a percutaneous Achilles tenotomy in most infants to achieve adequate dorsiflexion. Immediately following the tenotomy, a final long-leg cast is applied with the foot in maximum dorsiflexion and abduction; this cast remains in place for approximately three weeks to allow the severed tendon to heal in an elongated position. Finally, upon removal of the last cast, the patient is transitioned to a foot abduction orthosis (brace). Bracing is critical because the deformity has a very high rate of relapse; it is typically worn full-time for the first few months and then during sleep until the child reaches 4 to 5 years of age.

Step-by-Step Solution

1

Identify the underlying diagnosis based on the clinical presentation.

The rigid plantar flexion (equinus), heel inversion (varus), and forefoot medial deviation (adductus) confirm the diagnosis of congenital talipes equinovarus (clubfoot).

Accurate diagnosis is required to determine the appropriate treatment protocol.

2

Determine the first step in the standard management protocol.

The Ponseti method begins with weekly gentle manipulation and serial casting.

Initial non-operative casting corrects the cavus, adductus, and varus (CAV) components sequentially.

3

Identify the required intervention for the final uncorrected component.

After the varus and adductus are corrected, the residual equinus is addressed via a percutaneous Achilles tenotomy.

The Achilles tendon is typically too tight to stretch with casting alone; tenotomy is necessary in approximately 80% of cases.

4

Determine the immediate post-procedure management.

A final cast is applied for three weeks.

Tendon healing requires immobilization in the fully corrected (dorsiflexed) posture.

5

Determine the long-term management strategy.

The patient is transitioned to a foot abduction orthosis (brace).

Clubfoot has a high tendency to relapse; prolonged bracing maintains the correction as the child grows.

Key Concept

The standard of care for congenital talipes equinovarus (clubfoot) is the Ponseti method, consisting sequentially of serial casting, percutaneous Achilles tenotomy, final casting, and prolonged bracing.

Question 594Question →

An 8-month-old girl with an unrepaired congenital heart defect presents to the acute care clinic with sudden, severe cyanosis and inconsolable crying that began after feeding. Her parents state she has had milder episodes like this before, but they usually resolved quickly. On examination, the infant is highly agitated and has marked circumoral cyanosis. Her peripheral oxygen saturation is 60% on room air. A systolic ejection murmur is auscultated at the left mid-to-upper sternal border, though it is currently faint. The clinical picture is consistent with a hypercyanotic (tet) spell.

Arrange the following interventions in the correct chronological sequence for the acute management of this patient's condition, starting from the immediate initial response to the final definitive treatment step.

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Answer

The correct sequence is: 1) Place the infant in a knee-to-chest position and apply supplemental oxygen, 2) Administer an intravenous opioid (e.g., morphine), 3) Administer an intravenous alpha-1 receptor agonist (e.g., phenylephrine), and 4) Transfer to the operating room for urgent surgical intervention.

The correct sequence for managing a hypercyanotic spell escalates from immediate, non-invasive maneuvers to potent medical and surgical therapies. Placing the child in a knee-to-chest position increases systemic vascular resistance (SVR) by compressing the femoral arteries, which redirects blood flow away from the right-to-left shunt and into the pulmonary circulation. Supplemental oxygen helps increase pulmonary oxygenation and acts as a mild pulmonary vasodilator. If the child remains agitated and cyanotic, an intravenous opioid (such as morphine) is given to decrease sympathetic drive, thereby relieving infundibular spasm. For refractory spells, an intravenous alpha-1 agonist like phenylephrine is administered to substantially increase SVR. Finally, if all escalating medical interventions fail to resolve the cyanosis, urgent surgical palliation or complete repair is indicated as the definitive, life-saving treatment.

Step-by-Step Solution

1

Identify the clinical presentation and underlying pathophysiology

The patient is experiencing a hypercyanotic 'tet' spell due to right ventricular outflow tract obstruction (infundibular spasm) and increased right-to-left shunting.

The sudden onset of severe cyanosis, agitation, and a softer-than-usual systolic murmur in a patient with an unrepaired defect points directly to a hypercyanotic spell.

2

Determine the immediate initial management

Place the infant in a knee-to-chest position and administer supplemental oxygen.

This non-pharmacologic step instantly increases systemic vascular resistance (decreasing right-to-left shunting) and improves pulmonary venous oxygen content.

3

Determine the next step if initial measures are insufficient

Administer an intravenous opioid such as morphine.

Morphine calms the infant, reduces sympathetic tone, and helps relieve the infundibular spasm.

4

Determine the subsequent step for refractory cyanosis

Administer an intravenous alpha-1 agonist such as phenylephrine.

Phenylephrine is a potent vasopressor that significantly increases systemic vascular resistance, forcing more blood through the narrowed pulmonary circulation rather than across the ventricular septal defect.

5

Identify the definitive final management

Transfer for urgent surgical intervention.

If maximal medical management fails to break the spell, emergency surgical palliation (e.g., systemic-to-pulmonary shunt) or complete repair is required to save the patient's life.

Key Concept

The stepwise management of hypercyanotic (tet) spells prioritizes increasing systemic vascular resistance and relaxing the right ventricular outflow tract, progressing sequentially from physical positioning and oxygen to pharmacologic therapy (morphine, then phenylephrine), and ultimately to emergency surgery if refractory.

Question 595Question →

A 29-year-old nulliparous woman at 27 weeks of gestation comes to the obstetric clinic for a scheduled evaluation. She mentions that lately she feels "out of breath" when climbing stairs at home and has noticed her shoes feeling tight by the evening. She has no history of cardiopulmonary disease. Blood pressure is 114/72 mm Hg, pulse is 98/min, and respirations are 20/min. Cardiopulmonary auscultation reveals a grade 2/6 systolic murmur heard best over the left sternal border and clear breath sounds bilaterally. Trace pitting edema is noted around her ankles.

Laboratory analysis shows:
Leukocyte count: $14,200/\text{mm}^3$
Hemoglobin: $10.7 \text{ g/dL}$
Platelet count: $128,000/\text{mm}^3$
Serum creatinine: $0.5 \text{ mg/dL}$
Urine dipstick: 1+ glucose, negative for protein and blood.

Her blood type is O, Rh-positive.

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

Request a transthoracic echocardiogram to assess the cardiac murmur

Prescribe therapeutic ferrous sulfate for maternal anemia

Order an oral glucose challenge test for gestational diabetes screening

Instruct the patient to collect a 24-hour urine sample for total protein

Perform a ventilation-perfusion scan to rule out a pulmonary embolism

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Answer: Order an oral glucose challenge test for gestational diabetes screening

Answer

The correct answer is to order an oral glucose challenge test for gestational diabetes screening.

The correct answer is to proceed with routine screening, which includes a 50-g oral glucose challenge test. This patient presents with multiple clinical and laboratory findings that, while appearing abnormal in a non-pregnant patient, represent normal physiologic adaptations to pregnancy. Her dyspnea is due to progesterone-induced increased tidal volume. The 2/6 systolic murmur is a physiologic flow murmur resulting from increased cardiac output. The trace edema is due to decreased plasma oncotic pressure and inferior vena cava compression. Furthermore, her laboratory findings show a normal dilutional anemia of the second trimester (hemoglobin > 10.5 g/dL is normal), mild physiologic leukocytosis, gestational thrombocytopenia, decreased serum creatinine (due to increased GFR), and normal physiologic glycosuria. Because all findings are physiologic, she requires standard prenatal care, which at 24 to 28 weeks gestation mandates universal screening for gestational diabetes mellitus.

Step-by-Step Solution

1

Analyze the patient's clinical presentation and vital signs.

The patient has mild dyspnea, trace edema, and a 2/6 systolic murmur with normal vitals.

To differentiate between normal physiologic adaptations of pregnancy and potential cardiopulmonary pathology.

2

Evaluate the laboratory findings against pregnancy-specific reference ranges.

Hemoglobin (10.7 g/dL) is normal for the second trimester (>10.5 g/dL). Mild leukocytosis, thrombocytopenia, decreased creatinine, and trace glycosuria are also present and normal.

To identify any true hematologic or renal abnormalities requiring intervention.

3

Synthesize the findings to determine the patient's overall health status.

All clinical and laboratory findings reflect normal physiologic adaptations to pregnancy. No acute pathology is present.

To avoid unnecessary diagnostic testing for expected pregnancy changes.

4

Apply the standard prenatal care timeline to a normal pregnancy at 27 weeks gestation.

The 24 to 28-week window requires universal screening for gestational diabetes mellitus.

To select the most appropriate proactive management step for this specific routine visit.

Key Concept

Normal physiologic adaptations to pregnancy and the standard prenatal screening timeline

Question 596Question →

Match each clinical scenario describing an acute obstetric complication with its most appropriate immediate next step in management.

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Answer

Eclamptic seizures require magnesium sulfate. Shoulder dystocia is managed initially with McRoberts maneuver and suprapubic pressure. Uterine atony requires bimanual massage and uterotonics. Suspected placenta previa requires ultrasound prior to any digital cervical examination.

Each management step addresses the immediate life-threatening aspect of the matched complication: magnesium sulfate stabilizes eclamptic neuro-excitability, the McRoberts maneuver mechanically alters the maternal pelvis to resolve shoulder dystocia, physical massage and uterotonics directly counter uterine atony, and ultrasound ensures safety before evaluating a bleeding patient.

Step-by-Step Solution

1

Identify the underlying obstetric complication described in each clinical scenario.

Scenario 1 describes eclampsia, Scenario 2 describes shoulder dystocia, Scenario 3 describes uterine atony causing postpartum hemorrhage, and Scenario 4 describes possible placenta previa.

Accurate diagnosis based on hallmark clinical signs is required before determining the appropriate therapeutic intervention.

2

Determine the standard first-line management for each identified complication.

Magnesium sulfate for eclampsia; McRoberts maneuver for shoulder dystocia; bimanual massage and uterotonics for atony; ultrasound for painless third-trimester bleeding.

USMLE guidelines emphasize prioritizing interventions that immediately stabilize the patient or prevent catastrophic harm.

Key Concept

Recognizing classic presentations of major obstetric emergencies and selecting their immediate, first-line management.

Question 597Question →

Match each clinical presentation of a pregnant patient with the primary underlying physiological mechanism responsible for the findings.

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Answer

The presentations map to their physiological causes as follows: The dyspnea and respiratory alkalosis match progesterone-mediated respiratory drive; the second-trimester hypotension matches decreased systemic vascular resistance; the normocytic anemia with normal ferritin matches disproportionate plasma volume expansion; and the third-trimester dependent edema matches mechanical venous compression.

Each clinical scenario corresponds to a well-defined physiologic adaptation in pregnancy. The respiratory alkalosis is driven by progesterone; the mid-pregnancy blood pressure nadir is due to decreased systemic vascular resistance; the normocytic anemia is from disproportionate plasma volume expansion; and the dependent edema is due to mechanical compression of the inferior vena cava.

Step-by-Step Solution

1

Analyze the respiratory presentation (32 weeks with dyspnea and ABG).

The patient has mild dyspnea and a compensated respiratory alkalosis (low PaCO2, low HCO3, normal-high pH).

This is a classic normal physiologic change of pregnancy driven by progesterone, ruling out pathological causes like pulmonary embolism.

2

Analyze the cardiovascular presentation (18 weeks with dizziness).

The patient has asymptomatic to mildly symptomatic hypotension in the second trimester.

Blood pressure normally reaches a nadir at mid-pregnancy due to a significant drop in systemic vascular resistance.

3

Analyze the hematologic presentation (26 weeks with low hemoglobin).

The patient has anemia with normal MCV and normal iron stores (ferritin).

This confirms physiologic dilutional anemia due to disproportionate plasma volume expansion, differentiating it from iron deficiency anemia.

4

Analyze the renal/extremity presentation (36 weeks with ankle swelling).

The patient has trace proteinuria and dependent edema without hypertension.

Trace protein can be normal in pregnancy, and third-trimester edema is caused by mechanical compression of the IVC, ruling out preeclampsia.

Key Concept

Normal maternal physiological adaptations to pregnancy can mimic pathological states; they include progesterone-mediated respiratory alkalosis, decreased systemic vascular resistance, dilutional anemia, and mechanical venous compression.

Question 598Question →

Match each pediatric patient's clinical presentation with the most appropriate next step in management.

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Answer

Developmental Dysplasia of the Hip is managed with a Pavlik harness; Slipped Capital Femoral Epiphysis requires immediate surgery; Legg-Calvé-Perthes disease is managed conservatively with activity restriction and therapy; and Radial Head Subluxation is treated with a bedside hyperpronation reduction maneuver.

Each pediatric orthopedic condition has a distinct age demographic, presentation, and management protocol. DDH in infants is treated with positioning orthotics; SCFE in adolescents requires urgent surgical fixation to prevent severe avascular necrosis; LCPD in school-aged children relies on conservative containment; and nursemaid's elbow is a minor mechanical displacement requiring brief manual reduction.

Step-by-Step Solution

1

Analyze the first presentation (3-month-old, positive clunk on abduction).

Diagnose Developmental Dysplasia of the Hip (DDH).

The age and positive Ortolani maneuver strongly indicate DDH, prompting bracing with a Pavlik harness.

2

Analyze the second presentation (13-year-old obese boy, obligate external rotation).

Diagnose Slipped Capital Femoral Epiphysis (SCFE).

SCFE is an orthopedic emergency in adolescents requiring cessation of weight-bearing to prevent further epiphyseal displacement prior to surgery.

3

Analyze the third presentation (6-year-old, painless limp, sclerotic femoral head).

Diagnose Legg-Calvé-Perthes disease.

The radiographic findings of avascular necrosis in a young child without systemic symptoms point to this condition, which is managed conservatively.

4

Analyze the fourth presentation (2-year-old pulled by the wrist, arm held pronated).

Diagnose Radial head subluxation.

The classic mechanism of longitudinal traction on an extended arm dictates an immediate bedside reduction.

Key Concept

Management Strategies for Classic Pediatric Orthopedic Conditions

Question 599Question →

Match each classic clinical presentation during a primary postpartum hemorrhage with its most likely underlying etiology.

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Answer

The correct matches correctly align the classic physical exam findings with their respective postpartum hemorrhage etiologies: boggy uterus indicates atony, firm uterus with continuous bleeding indicates laceration, torn placenta indicates retained products, and an absent fundus indicates uterine inversion.

Each classic presentation maps specifically to the etiologies of postpartum hemorrhage: 'boggy' uterus to atony, firm uterus with continuous bleeding to lacerations, incomplete placenta to retained products, and absent fundus with vaginal mass to uterine inversion.

Step-by-Step Solution

1

Evaluate the state of the uterine tone on physical examination.

The presence of a soft or 'boggy' uterus indicates a loss of tone.

Uterine atony is the leading cause of postpartum hemorrhage and is diagnosed primarily by palpating a poorly contracted uterus.

2

Assess for bleeding in the setting of a firmly contracted uterus.

If the uterus is firm but active bleeding persists, trauma (lacerations) should be suspected.

Lacerations cause ongoing, often bright red bleeding that is independent of myometrial contraction.

3

Inspect the delivered placenta and the vaginal vault.

A torn maternal placental surface suggests retained tissue, whereas an absent fundus and a visible vaginal mass suggest uterine inversion.

Identifying these specific physical exam clues differentiates the remaining common causes of postpartum hemorrhage.

Key Concept

Differentiating the etiologies of primary postpartum hemorrhage based on classic physical examination findings.

Question 600Question →

A healthy 24-year-old primigravida presents for preconception counseling. She is subsequently confirmed pregnant and initiates prenatal care at 8 weeks gestation. Her initial laboratory workup reveals she is blood type A-negative. Assuming an uncomplicated pregnancy course that concludes with the term vaginal delivery of a healthy Rh(D)-positive neonate, arrange the following routine alloimmunization screening and prophylaxis steps in the correct chronological sequence from the first trimester through the postpartum period.

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Answer

The correct chronological sequence is: 1) Initial prenatal ABO/Rh(D) blood typing and baseline maternal serum indirect antiglobulin testing, 2) Repeat maternal indirect antiglobulin testing to confirm the continued absence of alloimmunization, 3) Routine antepartum prophylactic administration of a standard 300-mcg dose of anti-D immune globulin, 4) Qualitative erythrocyte rosette testing on maternal blood to detect massive fetal-maternal hemorrhage, and 5) Postpartum administration of anti-D immune globulin with the dose adjusted via quantitative testing.

The correct chronological sequence for managing an Rh(D)-negative pregnant patient begins with an initial prenatal ABO/Rh(D) blood typing and baseline maternal serum indirect antiglobulin testing to establish baseline status. At 28 weeks gestation, repeat maternal indirect antiglobulin testing must be performed to confirm the continued absence of alloimmunization. Immediately following this blood draw, routine antepartum prophylactic administration of a standard 300-mcg dose of anti-D immune globulin is given. Postpartum, after delivery of an Rh(D)-positive neonate, qualitative erythrocyte rosette testing on maternal blood is performed to detect significant fetal-maternal hemorrhage. Finally, postpartum administration of anti-D immune globulin is given within 72 hours, with the dose adjusted based on quantitative testing (such as the Kleihauer-Betke test) if the initial qualitative screen was positive.

Step-by-Step Solution

1

Identify the baseline initial prenatal testing requirements for an unsensitized Rh(D)-negative pregnant patient.

Initial prenatal ABO/Rh(D) blood typing and baseline maternal serum indirect antiglobulin testing must be performed first to establish the lack of pre-existing antibodies.

A baseline must be established in the first trimester before any potential sensitization events occur.

2

Determine the required screening immediately prior to third-trimester prophylaxis.

A repeat maternal indirect antiglobulin test is required at 28 weeks gestation.

It is necessary to confirm the patient has not become sensitized during the pregnancy before administering the prophylactic immune globulin.

3

Administer the standard antepartum prophylaxis.

Routine antepartum prophylactic administration of a standard 300-mcg dose of anti-D immune globulin is given.

This provides passive immunity during the third trimester and must be given only AFTER the 28-week antibody screen is drawn to avoid an iatrogenic positive screen.

4

Identify the appropriate initial postpartum screening test following delivery of an Rh(D)-positive neonate.

Qualitative erythrocyte rosette testing is performed on maternal blood.

This screens for massive fetal-maternal hemorrhage > 30 mL to determine if a single standard dose of immune globulin is sufficient or if quantitative testing is needed.

5

Administer the final targeted prophylaxis.

Postpartum administration of anti-D immune globulin is given, dosed according to quantitative testing (e.g., Kleihauer-Betke) if the rosette test was positive.

Adequate dosing must be given within 72 hours postpartum to neutralize all fetal erythrocytes and prevent permanent maternal alloimmunization.

Key Concept

Rh(D) alloimmunization prevention requires a strict chronological sequence: initial first-trimester screening, repeat screening at 28 weeks prior to routine antepartum prophylaxis, and postpartum qualitative/quantitative fetal-maternal hemorrhage testing to guide the final postpartum prophylactic dose.

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