Kidney Transplantation — Advanced

Correct answer: C. A positive complement-dependent cytotoxicity (CDC) crossmatch indicates the presence of cytotoxic, complement-fixing anti-donor antibodies and is associated with a high risk of hyperacute rejection; historically it has been considered a contraindication to transplantation without desensitisation or other measures. A negative flow cytometric crossmatch does not negate the prognostic importance of a positive CDC result. High MFI on Luminex indicates circulating anti-HLA antibodies and increases risk, but the CDC result specifically shows complement-fixing capability and immediate graft injury risk. Option A is incorrect because a negative flow cytometry does not reliably exclude the risk indicated by a positive CDC. Option B is incorrect: high MFI DSA increases rejection risk. Option D is unsafe—standard induction is inadequate when CDC is positive. Option E is incorrect: virtual crossmatch (based on antibody specificities) informs compatibility but does not supplant a positive CDC crossmatch which demonstrates functional cytotoxicity.

Correct answer: A. Active, untreated malignancy is an absolute contraindication to living kidney donation because of the risk of tumour transmission and the donor's own health risks. Options B, C, D and E are considerations that may be acceptable or relative contraindications depending on centre-specific evaluation and risk assessment: a remote solitary stone may be allowed, older age is assessed on fitness rather than an absolute cutoff, high BMI is often a relative contraindication and managed case by case, and well-controlled diabetes may preclude donation if there is evidence of end-organ damage but isolated well-controlled diabetes without complications may be handled variably. Thus only active untreated cancer is an absolute contraindication.

Correct answer: E. cPRA estimates the proportion of donors in the donor pool who would be incompatible because the recipient has unacceptable HLA antibodies; a cPRA of 80% implies that about 80% of potential donors carry one or more unacceptable antigens and approximately 20% would be compatible. It does not directly quantify immediate rejection risk (A), is not limited to family members (B), is not a statement about transfusions (C), nor does it predict immediate graft loss irrespective of donor-specific matching or desensitisation (D).

Correct answer: B. For patients at high immunological risk (retransplantation, high PRA), guidelines commonly recommend T-cell-depleting induction such as rabbit antithymocyte globulin (rATG) because it provides greater lymphocyte depletion and lower early rejection rates than IL-2 receptor antagonists. Basiliximab (A) is typically used for lower-risk recipients. Belatacept (C) is an alternative maintenance agent in some contexts but is not the standard induction choice for high immunological risk. High-dose steroids alone (D) are generally inferior to lymphocyte-depleting agents in high-risk patients. Option E (anti-IL-6) is not established as standard induction in this setting.

Correct answer: D. In the immediate post-transplant period with oliguria and concern for poor graft perfusion, an urgent Doppler ultrasound is the best initial test to assess vascular complications (arterial/venous thrombosis, stenosis, cortical perfusion) and can be performed rapidly at the bedside. Option A (immediate biopsy) risks bleeding if a vascular complication is present and is not first-line. Empirical high-dose steroids (B) are inappropriate without evidence of rejection and may worsen infection risk; biopsy-directed therapy is preferred. A nuclear medicine scan (C) can be useful but is less readily available and slower than Doppler in most centres. Checking tacrolimus level (E) is reasonable but will not rapidly exclude a vascular surgical cause and should not delay imaging.

Correct answer: A. The biopsy findings and presence of DSA are diagnostic of antibody-mediated rejection (AMR). Initial treatment typically targets removal and neutralisation of pathogenic antibodies with plasmapheresis (or therapeutic plasma exchange) combined with IVIG; adjunctive agents (e.g., rituximab) may be used in many protocols. High-dose steroids alone (B) are the mainstay for acute cellular rejection but are generally insufficient for AMR. Increasing calcineurin inhibitor dose (C) is not the priority and may be harmful. Observation (D) is inappropriate for AMR because it usually progresses without active therapy. Acyclovir (E) is irrelevant to AMR.

Correct answer: C. The initial and evidence-based step for BK viraemia is to reduce immunosuppression (commonly reducing or holding the antimetabolite such as mycophenolate) and monitor viral load and renal function closely. Biopsy is generally reserved for cases where renal function is worsening or to confirm BK nephropathy. There is no proven role for ganciclovir (A) which targets herpesviruses, and cidofovir (D) is nephrotoxic and not routinely first-line. Increasing steroids (E) would worsen viral replication and is contraindicated.

Correct answer: E. Histologic changes consistent with chronic CNI nephrotoxicity warrant strategies to reduce CNI exposure, such as lowering trough targets or converting to an mTOR inhibitor (sirolimus/everolimus) where appropriate. Conversion may slow progression of chronic injury; however conversion must be considered carefully because mTOR inhibitors can worsen wound healing and increase proteinuria. Increasing CNI (A) would worsen toxicity. Immediate cessation of all immunosuppression (B) is unsafe. High-dose prednisone monotherapy (C) is not an effective long-term strategy and increases adverse effects. Adding mycophenolate without addressing CNI exposure (D) will not reverse CNI-induced structural injury.

Correct answer: B. Conversion from calcineurin inhibitors to mTOR inhibitors (sirolimus/everolimus) has been associated with a reduced incidence of certain skin malignancies and may be considered in patients with multiple skin cancers, balancing benefits against side effects (e.g., impaired wound healing, dyslipidaemia, proteinuria). Increasing tacrolimus (A) would likely increase cancer risk. High-dose corticosteroids (C) worsen long-term complications and do not reduce cancer risk. Stopping all immunosuppression (D) risks graft loss. Azathioprine (E) is not used specifically to reduce cancer risk and in some contexts may increase photosensitivity and cancer risk. Management should be individualised with dermatology and transplant teams.

Correct answer: D. Donor-positive/recipient-negative (D+/R−) is the highest CMV risk constellation; most guidelines recommend antiviral prophylaxis (commonly valganciclovir) for a defined post-transplant period rather than relying solely on pre-emptive PCR monitoring. No prophylaxis (A) is unsafe. Pre-emptive monitoring (B) is an option for intermediate-risk groups but D+/R− generally benefits from prophylaxis. Lifelong acyclovir (C) is not appropriate; acyclovir has limited CMV activity compared with ganciclovir/valganciclovir. IVIG (E) is not used as sole CMV prophylaxis.