A 55-year-old woman recently underwent kidney transplantation for end-stage renal disease. Her early postoperative period was uneventful, and her serum creatinine is lowered from 4.3 mg/dL (preoperative) to 2.5 mg/dL. She is immediately started on immunosuppressive therapy. On postoperative day 7, she presents to the emergency department (ED) because of nausea, fever, abdominal pain at the transplant site, malaise, and pedal edema. The vital signs include: pulse 106/min, blood pressure 167/96 mm Hg, respirations 26/min, and temperature 40.0°C (104.0°F). The surgical site shows no signs of infection. Her urine output is 250 mL over the past 24 hours. Laboratory studies show: Hematocrit 33% White blood cell (WBC) count 6700/mm3 Blood urea 44 mg/dL Serum creatinine 3.3 mg/dL Serum sodium 136 mEq/L Serum potassium 5.6 mEq/L An ultrasound of the abdomen shows collection of fluid around the transplanted kidney with moderate hydronephrosis. Which of the following initial actions is the most appropriate?

Continue with an ultrasound-guided biopsy of the transplanted kidney

Re-operate and remove the failed kidney transplant

Start on pulse steroid treatment or OKT3

Supportive treatment with IV fluids, antibiotics, and antipyretics

A 33-year-old HIV-positive male is seen in clinic for follow-up care. When asked if he has been adhering to his HIV medications, the patient exclaims that he has been depressed, thus causing him to not take his medication for six months. His CD4+ count is now 33 cells/mm3. What medication(s) should he take in addition to his anti-retroviral therapy?

Azithromycin and trimethoprim-sulfamethoxazole

Azithromycin, dapsone, and fluconazole

A 26-year-old man is undergoing a bone marrow transplantation for treatment of a non-Hodgkin lymphoma that has been refractory to several rounds of chemotherapy and radiation over the past 2 years. He has been undergoing a regimen of cyclophosphamide and total body irradiation for the past several weeks in anticipation of his future transplant. This morning, he reports developing a productive cough and is concerned because he noted some blood in his sputum this morning. The patient also reports pain with inspiration. His temperature is 101°F (38.3°C), blood pressure is 115/74 mmHg, pulse is 120/min, respirations are 19/min, and oxygen saturation is 98% on room air. A chest radiograph and CT are obtained and shown in Figures A and B respectively. Which of the following is the most likely diagnosis?

Pneumocystis jiroveci pneumonia

A 66-year-old man is transferred from another hospital after 3 days of progressively severe headache, vomiting, low-grade fever, and confusion. According to his partner, the patient has been dealing with some memory loss and complaining about headaches for the past 2 weeks. He has a history of interstitial pulmonary disease that required lung transplantation 2 years ago. Upon admission, he is found with a blood pressure of 160/100 mm Hg, a pulse of 58/min, a respiratory rate of 15/min, and a body temperature of 36°C (97°F). During the examination, he is found with oral thrush and symmetric and reactive pupils; there are no focal neurological signs or papilledema. A lumbar puncture is performed. Which of the following features would be expected to be found in this case?

Aspect: clear, opening pressure: ↑, cell count: ↑ lymphocytes, protein: ↑, glucose: ↓

Aspect: clear, opening pressure: normal, cell count: < 5 cells/µL, protein: normal, glucose: normal

Aspect: clear, opening pressure: normal, cell count: ↑ lymphocytes, protein: normal, glucose: normal

Aspect: cloudy, opening pressure: ↑, cell count: ↑ neutrophils, protein: ↑, glucose: ↓

Aspect: xanthochromic, opening pressure: normal, cell count: ↑ red blood cells, protein: normal, glucose: normal

A 24-year-old man is brought to the emergency department 30 minutes after being involved in a high-speed motor vehicle collision in which he was a restrained driver. On arrival, he is alert and oriented. His pulse is 112/min, respirations are 29/min, and blood pressure is 100/60 mm Hg. The pupils are equal and reactive to light. There is a 3-cm laceration over the forehead and multiple bruises over the trunk. The lungs are clear to auscultation. Cardiac examination shows no abnormalities. The abdomen is soft and nontender. The right knee is swollen and tender; range of motion is limited by pain. Infusion of 0.9% saline is begun and intravenous acetaminophen is administered. Two hours later, blood-tinged fluid spontaneously drains from both nostrils, and is made worse by leaning forward. On a piece of gauze, it shows up as a rapidly-expanding clear ring of fluid surrounding blood. Further evaluation of this patient is most likely to show which of the following?

Bilateral periorbital ecchymosis

Post-transplant infections for USMLE Step 2 CK: High-Yield Surgery Lessons

Infection Timeline - The Risky Calendar

<1 Month (Immediate): Hospital-acquired infections dominate. Think bacterial sources from the surgical wound, IV lines (catheter-related), or ventilator-associated pneumonia. Candida infections are also frequent.
1-6 Months (Delayed): Corresponds to peak immunosuppressive therapy. This is the prime window for opportunistic pathogens normally controlled by T-cells (e.g., Pneumocystis jirovecii, Aspergillus).
>6 Months (Late): As immunosuppression is reduced, the risk profile shifts. Patients are more susceptible to common community-acquired pathogens and reactivation of chronic viruses like BK virus (nephropathy).

⭐ Cytomegalovirus (CMV) is the quintessential opportunistic infection of the 1-6 month period. It can manifest as pneumonitis, colitis, retinitis, or a mono-like syndrome.

Opportunistic Bugs - The Usual Suspects

CMV (Cytomegalovirus): The most significant pathogen in the 1-6 month window.
- Presents as pneumonitis, esophagitis/colitis, hepatitis, or retinitis.
- Biopsy reveals characteristic "owl's eye" intranuclear inclusions.
Pneumocystis jirovecii (PJP):
- Causes diffuse interstitial pneumonia; diagnosed via bronchoalveolar lavage (BAL).
⭐ Prophylaxis is crucial, typically with Trimethoprim-Sulfamethoxazole (TMP-SMX) for the first 6-12 months post-transplant.
Other Key Pathogens:
- Fungi: Aspergillus fumigatus (invasive disease, "halo sign" on chest CT), Candida species.
- Bacteria: Nocardia (cavitary lung lesions, brain abscesses), Listeria monocytogenes (meningitis).
- Viruses: EBV (risk of Post-Transplant Lymphoproliferative Disorder - PTLD), VZV.

Prophylaxis & Tx - The Protective Shield

Universal Prophylaxis (First 6-12 months):
- PJP/PCP: Lifelong TMP-SMX. Alternatives: atovaquone, dapsone.
- CMV: Valganciclovir for high-risk (D+/R-). Others monitored with PCR (pre-emptive therapy).
- Fungal (Candida): Fluconazole or nystatin, especially with high steroid use.
- HSV/VZV: Acyclovir or valacyclovir if seropositive.
Treatment Approach:
- Guided by pathogen identification (culture, PCR, biopsy).
- Crucial first step: Reduce immunosuppression if feasible, balancing rejection risk.

⭐ For febrile neutropenia post-transplant, initial treatment requires broad-spectrum coverage against Pseudomonas, like cefepime or piperacillin-tazobactam.

High‑Yield Points - ⚡ Biggest Takeaways

Infection timing is the most crucial diagnostic clue.

<1 month post-transplant: Think nosocomial bacterial infections from the surgical site, catheters, or aspiration.

1-6 months: This is the classic window for opportunistic infections (e.g., CMV, PJP, Aspergillus) due to peak immunosuppression.

>6 months: The risk profile shifts towards community-acquired pathogens and chronic viral infections like BK virus nephropathy.

Universal prophylaxis with TMP-SMX (for PJP) is standard.

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