A 60-year-old rock musician presents to the office because he has been feeling increasingly tired for the past 6 months. He has a history of intravenous drug use and alcohol abuse. He states that he feels quite tired, but he otherwise has no complaints. Physical examination is noncontributory. His laboratory values are normal other than moderately elevated liver enzymes. Which of the following additional tests should you order first?

Hepatitis E virus-specific IgM antibodies

Hepatitis D virus-specific IgG antibody

Hepatitis A virus-specific IgM antibodies

A 50-year-old morbidly obese woman presents to a primary care clinic for the first time. She states that her father recently died due to kidney failure and wants to make sure she is healthy. She works as an accountant, is not married or sexually active, and drinks alcohol occasionally. She currently does not take any medications. She does not know if she snores at night but frequently feels fatigued. She denies any headaches but reports occasional visual difficulties driving at night. She further denies any blood in her urine or increased urinary frequency. She does not engage in any fitness program. She has her period every 2 months with heavy flows. Her initial vital signs reveal that her blood pressure is 180/100 mmHg and heart rate is 70/min. Her body weight is 150 kg (330 lb). On physical exam, the patient has droopy eyelids, a thick neck with a large tongue, no murmurs or clicks on cardiac auscultation, clear lungs, a soft nontender, albeit large abdomen, and palpable pulses in her distal extremities. She can walk without difficulty. A repeat measurement of her blood pressure shows 155/105 mmHg. Which among the following is part of the most appropriate next step in management?

Renal artery doppler ultrasonography

A 50-year-old man presents to a clinic with oliguria. Four weeks ago, he had a kidney transplant. Postoperative follow-up was normal. He is currently on cyclosporine and admits that sometimes he forgets to take his medication. On physical examination, the vital signs include: temperature 37.1°C (98.8°F), blood pressure 165/110 mm Hg, heart rate 80/min, and respiratory rate 16/min. There is mild tenderness on renal palpation. His serum creatinine level is 4 mg/dL, well above his baseline level after the transplant. Which of the following best describes the histological finding if a biopsy is taken from the transplanted kidney?

Lymphocytic infiltration of graft vessels and endothelial damage

Thrombosis and occlusion of vessels

Necrosis with granulation tissue

Thickening of blood vessels, fibrosis of graft vessels, and parenchymal atrophy

A student health coordinator plans on leading a campus-wide HIV screening program that will be free for the entire undergraduate student body. The goal is to capture as many correct HIV diagnoses as possible with the fewest false positives. The coordinator consults with the hospital to see which tests are available to use for this program. Test A has a sensitivity of 0.92 and a specificity of 0.99. Test B has a sensitivity of 0.95 and a specificity of 0.96. Test C has a sensitivity of 0.98 and a specificity of 0.93. Which of the following testing schemes should the coordinator pursue?

Test C on the entire student body followed by Test A on those who are positive

Test A on the entire student body followed by Test B on those who are positive

Test A on the entire student body followed by Test C on those who are positive

Test C on the entire student body followed by Test B on those who are positive

Test B on the entire student body followed by Test A on those who are positive

A 27-year-old G1P0 female presents for her first prenatal visit. She is in a monogamous relationship with her husband, and has had two lifetime sexual partners. She has never had a blood transfusion and has never used injection drugs. Screening for which of the following infections is most appropriate to recommend this patient?

Syphilis, HIV, HBV, and chlamydia

No routine screening is recommended for this patient

A 34-year-old man comes to the physician for a routine health maintenance examination. He was diagnosed with HIV 8 years ago. He is currently receiving triple antiretroviral therapy. He is sexually active and uses condoms consistently. He is planning a trip to Thailand with his partner to celebrate his 35th birthday in 6 weeks. His last tetanus and diphtheria booster was given 4 years ago. He received three vaccinations against hepatitis B 5 years ago. He had chickenpox as a child. Other immunization records are unknown. Vital signs are within normal limits. Cardiopulmonary examination shows no abnormalities. Leukocyte count shows 8,700/mm3, and CD4+ T-lymphocyte count is 480 cells/mm3 (Normal ≥ 500); anti-HBs is 150 mIU/mL. Which of the following recommendations is most appropriate at this time?

Tetanus, diphtheria, pertussis vaccine (Tdap)

Measles, mumps, rubella vaccine

A 38-year-old kidney transplant recipient maintained on tacrolimus presents with a 2-week history of progressive confusion, ataxia, and visual disturbances. MRI shows multifocal white matter lesions without mass effect or enhancement. CSF analysis reveals mild pleocytosis with elevated protein. JC virus DNA is detected in CSF by PCR. Serum tacrolimus level is therapeutic at 8 ng/mL. Apply knowledge of this condition to determine the appropriate management strategy.

Significantly reduce or discontinue immunosuppression and provide supportive care

Switch from tacrolimus to sirolimus to preserve graft while treating infection

Continue current immunosuppression and administer IVIG therapy

Maintain immunosuppression and start cidofovir antiviral therapy

Reduce tacrolimus by 50% and start high-dose corticosteroids

Donor selection criteria for USMLE Step 1: High-Yield Surgery Lessons

Donor Selection - The Gatekeepers' Rules

Core Principle: Maximize graft survival while minimizing disease transmission.
General Criteria: Hemodynamic stability, absence of irreversible organ damage.
Absolute Contraindications:
- Uncontrolled systemic infection (sepsis).
- Most extracranial malignancies.
- HIV infection (though evolving with the HOPE Act).
- Prion diseases (e.g., CJD).
Relative Contraindications:
- Advanced age (> 70-80 years, varies by organ).
- Hepatitis B/C (can donate to positive recipients).
- Treated, localized cancers with long disease-free interval.
- Significant comorbidities (severe HTN, DM).

⭐ Primary non-metastasizing brain tumors (e.g., low-grade astrocytoma) generally DO NOT preclude organ donation.

Organ-Specific Criteria - Matchmaking Organs

Heart & Lungs:
- Primary: ABO compatibility & size matching (height, weight ±20%).
- Heart: Panel Reactive Antibody (PRA) < 10%.
- Lungs: Lung Allocation Score (LAS) guides priority based on urgency/benefit. Donor must have clear chest imaging and no aspiration.
Liver:
- Primary: ABO compatibility & size.
- Priority set by MELD/PELD score.
- Absence of extrahepatic malignancy or uncontrolled sepsis.
Kidney:
- Primary: ABO compatibility & Human Leukocyte Antigen (HLA) matching.
- Negative complement-dependent cytotoxicity (CDC) crossmatch is mandatory.
- PRA screens for pre-formed anti-HLA antibodies.

⭐ For kidneys, HLA-DR matching is the most critical for long-term graft survival, followed by HLA-B and then HLA-A.

Infection Screening - Dodging Dangerous Donations

Core Serologies: Mandatory screening for all potential donors.
- HIV-1/2 (Antibody & NAT)
- Hepatitis B (HBsAg, anti-HBc, NAT)
- Hepatitis C (Anti-HCV, NAT)
- Syphilis (e.g., RPR)
Viral Panel:
- CMV (IgG) - critical for matching
- EBV (VCA IgG)
- HTLV-1/2
Targeted Screening: Based on exposure/geography.
- West Nile Virus (NAT)
- Trypanosoma cruzi (Chagas disease)
- SARS-CoV-2

⭐ Nucleic Acid Testing (NAT) is vital for detecting recent infections (HIV, HBV, HCV) during the serological "window period," especially in donors with high-risk behaviors.

Special Cases - Expanded Criteria Donors

Donors aged > 60 years, or aged > 50 years with at least two of the following:
- History of hypertension (HTN)
- Terminal creatinine > 1.5 mg/dL
- Death from cerebrovascular accident (CVA)
ECD organs carry a higher risk of graft dysfunction and failure but expand the donor pool, offering a survival benefit over waiting.

⭐ Despite increased risks, accepting an ECD kidney provides a significant mortality benefit compared to remaining on the transplant waitlist, especially for older recipients.

High‑Yield Points - ⚡ Biggest Takeaways

ABO compatibility is the most critical initial step in donor selection, a non-negotiable prerequisite.

HLA matching, particularly for HLA-A, B, and DR loci, is crucial for long-term graft survival, especially in kidney and bone marrow transplants.

Absolute contraindications include active infections (HIV, viral hepatitis), uncontrolled sepsis, and most malignancies.

Donor age is a significant factor; organs from very young or elderly donors may have reduced function.

Hemodynamic stability and adequate end-organ function are essential for deceased donors.

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