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 61-year-old-male underwent deceased donor liver transplantation 3 weeks ago. During his follow up visit he complains of nausea and abdominal pain. He has been taking all of his medications as prescribed. He has a history of alcohol abuse and his last drink was one year ago. He does not smoke cigarettes and lives at home with his wife. On physical examination temperature is 98.6°F (37°C), blood pressure is 115/80 mmHg, pulse is 90/min, respirations are 18/min, and pulse oximetry is 99% on room air. He has scleral icterus and a positive fluid wave. Liver function tests are as follows: Alkaline phosphatase: 110 U/L Aspartate aminotransferase (AST, GOT): 100 U/L Alanine aminotransferase (ALT, GPT): 120 U/L Bilirubin total: 2.2 mg/dL Liver biopsy shows mixed dense interstitial lymphocytic infiltrates in the portal triad. What is the mechanism of this reaction?

CD8+ T lymphocytes reacting against donor MHCs

Grafted T lymphocytes reacting against host

CD4+ T lymphocytes reacting against recipient APCs

Pre-existing recipient antibodies

A 57-year-old man presents to the emergency department with fatigue. He states that his symptoms started yesterday and have been worsening steadily. The patient endorses a recent weight loss of 7 pounds this past week and states that he feels diffusely itchy. The patient has a past medical history of alcohol abuse, obesity, asthma, and IV drug use. His current medications include metformin, atorvastatin, albuterol, and fluticasone. In addition, the patient admits to smoking and drinking more than usual lately due to the stress he has experienced. His temperature is 98.7°F (37.1°C), blood pressure is 130/75 mmHg, pulse is 90/min, respirations are 15/min, and oxygen saturation is 98% on room air. Physical exam is notable for an ill-appearing man. The patient's skin appears yellow. Abdominal exam is notable for right upper quadrant tenderness. Cardiac and pulmonary exams are within normal limits. Laboratory values are ordered as seen below: Hemoglobin: 14 g/dL Hematocrit: 42% Leukocyte count: 5,500 cells/mm^3 with normal differential Platelet count: 70,000/mm^3 Partial thromboplastin time: 92 seconds Prothrombin time: 42 seconds AST: 1110 U/L ALT: 990 U/L Which of the following is most likely to be found in this patient's history?

Severe migraine headaches treated with acetaminophen

Recent antibiotic treatment with gentamicin

Appropriate acute management of a deep vein thrombosis

Decreased UDP-glucuronosyltransferase activity at birth

Prosthetic valve with appropriate post-operative care

A 45-year-old man is brought to the emergency department because of a 1-day history of malaise and abdominal pain. Six weeks ago, he had vomiting and watery diarrhea for 2 days that resolved without treatment. Twelve weeks ago, he underwent orthotopic liver transplantation for alcoholic cirrhosis. At the time of discharge, his total serum bilirubin concentration was 1.0 mg/dL. He stopped drinking alcohol one year ago. His current medications include daily tacrolimus, prednisone, valganciclovir, and trimethoprim-sulfamethoxazole. His temperature is 37.7°C (99.9°F), pulse is 95/min, and blood pressure is 150/80 mm Hg. He appears uncomfortable and has mild jaundice. Examination shows scleral icterus. The abdomen is soft and tender to deep palpation over the right upper quadrant, where there is a well-healed surgical scar. His leukocyte count is 2500/mm3, serum bilirubin concentration is 2.6 mg/dL, and serum tacrolimus concentration is within therapeutic range. Which of the following is the next appropriate step in diagnosis?

CT scan of the abdomen with contrast

A 54-year-old man with known end-stage liver disease from alcoholic cirrhosis presents to the emergency department with decreased urinary output and swelling in his lower extremities. His disease has been complicated by ascites and hepatic encephalopathy in the past. Initial laboratory studies show a creatinine of 1.73 mg/dL up from a previous value of 1.12 one month prior. There have been no new medication changes, and no recent procedures performed. A diagnostic paracentesis is performed that is negative for infection, and he is admitted to the hospital for further management and initiated on albumin. Two days later, his creatinine has risen to 2.34 and he is oliguric. Which of the following is the most definitive treatment for this patient's condition?

Transjugular intrahepatic portosystemic shunt (TIPS)

A 37-year-old man who had undergone liver transplantation 7 years ago, presents to the physician because of yellowish discoloration of the skin, sclera, and urine. He is on regular immunosuppressive therapy and is well-adherent to the treatment. He has no comorbidities and is not taking any other medication. He provides a history of similar episodes of yellowish skin discoloration 6–7 times since he underwent liver transplantation. Physical examination shows clinical jaundice. Laboratory studies show: While blood cell (WBC) count 4,400/mm3 Hemoglobin 11.1 g/dL Serum creatinine 0.9 mg/dL Serum bilirubin (total) 44 mg/dL Aspartate transaminase (AST) 1,111 U/L Alanine transaminase (ALT) 671 U/L Serum gamma-glutamyl transpeptidase 777 U/L Alkaline phosphatase 888 U/L Prothrombin time 17 seconds A Doppler ultrasound shows significantly reduced blood flow into the transplanted liver. A biopsy of the transplanted liver is likely to show which of the following histological features?

Interstitial cellular infiltration with parenchymal fibrosis, obliterative arteritis

Ballooning degeneration of hepatocytes

Normal architecture of bile ducts and hepatocytes

Irregularly shaped nodules of regenerating hepatocytes with peripheral halo

Broad fibrous septations with formation of micronodules

Liver transplantation for USMLE Step 3: High-Yield Internal Medicine Lessons

Indications & Scoring - The Waiting Game

Indications for Transplant
- Acute Liver Failure: Fulminant viral hepatitis (A, B), drug-induced (e.g., Acetaminophen), Wilson's disease.
- Chronic Liver Disease: Decompensated cirrhosis from any cause (HCV, HBV, NAFLD, alcohol), Hepatocellular Carcinoma (HCC) within Milan criteria.
MELD Score: Prioritizes Allocation
- Calculates 3-month mortality risk. Formula: $MELD = 3.78 imes ext{ln[Bilirubin]} + 11.2 imes ext{ln[INR]} + 9.57 imes ext{ln[Creatinine]} + 6.43$
- 📌 Mnemonic: I Bleed Chestnuts (INR, Bilirubin, Creatinine).
Absolute Contraindications
- Severe, irreversible cardiopulmonary disease.
- Active extrahepatic malignancy.
- Ongoing alcohol or illicit substance abuse.

⭐ Patients with a MELD score ≥ 15 are typically listed. MELD-Na is a common variant, adding sodium for better prognostication in hyponatremia.

Evolution of MELD, MELD-Na, and MELD 3.0 components

Donor & Surgery - The Main Event

Deceased Donor (DDLT): Whole organ from a deceased donor; longer wait times.
Living Donor (LDLT): Partial graft (e.g., right lobe) from a living donor; technically complex.

Liver Transplant Surgical Techniques

Key Early Complications:
- Hepatic Artery Thrombosis (HAT): Most common vascular complication.
- Portal Vein Thrombosis
- Biliary leaks & strictures

⭐ HAT is a surgical emergency, often presenting with graft dysfunction and requiring urgent re-transplantation.

Rejection Types - The Body Fights Back

Type	Onset	Pathophysiology	Histology Findings
Hyperacute	Minutes to hours	Pre-formed anti-donor Abs	Vascular thrombosis, neutrophilic infiltrate
Acute	Days to weeks (<6 mo)	T-cell mediated injury	Portal lymphocytic infiltrate, endothelitis
Chronic	Months to years (>6 mo)	Mixed cellular & humoral	Vanishing bile duct syndrome, progressive fibrosis

⭐ Acute rejection is the most common type, typically occurring within the first few months post-transplant; it is usually reversible with immunosuppressive therapy.

Immunosuppression - Taming the Guards

A multi-drug regimen prevents rejection by targeting different immune pathways, balancing efficacy with toxicity.

Drug Class	Drugs	Key Adverse Effects
Calcineurin Inhibitors	Tacrolimus, Cyclosporine	Nephrotoxicity, neurotoxicity (tremor), HTN, ↑K⁺
Antimetabolites	Mycophenolate Mofetil	GI distress (diarrhea), bone marrow suppression
mTOR Inhibitors	Sirolimus, Everolimus	Hyperlipidemia, delayed wound healing, stomatitis
Corticosteroids	Prednisone	Hyperglycemia, osteoporosis, Cushingoid features

⭐ Calcineurin inhibitors (Tacrolimus, Cyclosporine) are metabolized by CYP3A4; many drug-drug interactions can affect their levels.

Post-Op Complications - Navigating the Aftermath

Opportunistic Infections: Follow a predictable timeline based on the net state of immunosuppression.

Metabolic Syndrome: Immunosuppressants often drive new-onset diabetes, hypertension, and hyperlipidemia.
Renal Insufficiency: A major long-term issue, frequently due to calcineurin inhibitor (tacrolimus) nephrotoxicity.
Malignancy: Significantly ↑ risk of skin cancer (squamous cell) & Post-Transplant Lymphoproliferative Disorder (PTLD).

⭐ PTLD is a life-threatening B-cell proliferation driven by Epstein-Barr Virus (EBV). Reducing immunosuppression is a key first step in management.

High‑Yield Points - ⚡ Biggest Takeaways

MELD score is key for allocation, predicting 3-month mortality using bilirubin, INR, creatinine, and sodium.

Main indications are acute liver failure, decompensated cirrhosis, and HCC within Milan criteria.

Absolute contraindications include active extrahepatic malignancy, severe cardiopulmonary disease, and active substance abuse.

Post-transplant immunosuppression typically involves tacrolimus, mycophenolate, and corticosteroids.

Suspect acute rejection with rising LFTs; confirm with biopsy. Hepatic artery thrombosis is a major vascular complication.

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