Objectives: To investigate the timing of the clinical presentation of various types of bacille Calmette-Guérin (BCG) infections in a Finnish population of patients with bladder cancer treated with BCG instillation therapy.

Patients and methods: We identified patients with a history of post-instillation BCG infection from 1996 to 2016 using the Finnish Cancer Registry and the Finnish National Infectious Diseases Registry. We categorised infections as systemic if the infection was found in the non-urogenital system and genitourinary (GU) if the infection affected the urogenital tract. We calculated the time interval between the last BCG instillation and the presentation of the infection. The infection was considered late if the time interval was ≥1 year.

Results: A total of 100 patients with BCG infection were identified during the study period. In all, 39 (39%) infections presented as systemic and 61 (61%) were in the GU tract. The majority of the systemic infections presented rapidly after the last instillation, while five (13%) presented after a latency of ≥1 year. The presentation of GU infections was more heterogeneous, with 12 (20%) presenting as late infections.

Conclusion: This study confirms the concept of early and late infection types, especially among systemic infections. However, late infections appeared to be rarer than previously described. Urologists should be aware of the possibility of late BCG infection if patients develop symptoms even several years after the BCG regimen.