To the Editor: I have read with interest the case presented by Wu et al. 1 regarding urinary bladder perforation after implantation of a peritoneal dialysis (PD) catheter. The colored picture showing methylene blue in the effluent dialysate in the PD bag is quite impressive for the general practitioner, but nephrologists involved in the field of PD may express several objections regarding this approach.There are several reports that methylene blue may be an irritant to the peritoneum and cause chemical peritonitis, and thus, it is not advisable to use it for diagnostic reasons in PD. 2,3 The unexpected glycosuria and the abdominal computed tomography imaging should be sufficient to establish the correct diagnosis, as in other cases. 4 The patient of Wu et al. 1 was transferred to maintenance hemodialysis. However, I would not consider the use of methylene blue in PD for diagnostic reasons as a wise approach, as the main focus of PD remains to preserve the peritoneum for as long as possible.