A 59-year-old patient underwent laparoscopic radical prostatectomy (LRP) in our department. After surgery, he had an extensive cellulitis of the right flank develop. Urine, drainage effluent, and blood cultures were all positive for Escherichia coli. Prolonged broad spectrum antibiotherapy allowed progressive resolution of the cellulitis. This case shows that severe cellulitis can occur after LRP. Urinary tract infection and vesicourethral anastomotic leakage may contribute to this complication.