Alice Kennard, Prof David W Johnson and Ross Francis
BK virus is a human polyomavirus that rarely causes disease, except in immune-compromised patients. Evidence of prior BK Virus (BKV) infection is highly prevalent in the general population, and although it rarely causes significant morbidity at primary infection, reactivation of BKV after kidney transplantation is recognized as a cause of BKV-associated Nephropathy (BKVAN), ureteric stenosis, and, rarely, haemorrhagic cystitis. The incidence of BKVAN appears to be increasing, most likely because of increased surveillance post-transplant, as well as the use of more potent immunosuppressive agents. Many patients with BKVAN experience progressive kidney dysfunction and the disease represents a significant threat to long-term kidney transplant success. This narrative review will discuss the epidemiology, risk factors, clinical features, screening, diagnosis and management of BKV infection in the setting of kidney transplantation, as well as suggest future research directions.