In the abstract, in the methodology section, line number 1, the following sentence: ‘This study was conducted prospectively at the Gezira Hospital for Renal Disease and Surgery and at the National Cancer Institute at the University of Gezira, Sudan, for an 11-year period’ should be replaced with ‘This study was conducted retrospectively at the Gezira Hospital for Renal Disease and Surgery and at the National Cancer Institute at the University of Gezira, Sudan, for an 11-year period.’