Correspondence Peritonitis after endoscopic marking in a peritoneal dialysis patient: Could it be chemical? Pamela Gallo, Giuseppe Ferro, Ileana Benedetti, Chiara Somma and Pietro Claudio Dattolo Peritoneal dialysis patients have higher risk for peritonitis after colonoscopy, due to microperforations of the colonic wall or spontaneous bacterial translocation. 1,2 The 2016 International Society for Peritoneal Dialysis guidelines suggests antibiotic prophylaxis. 3 Peritoneal spreading of dye during endoscopic tattooing is a complication of colo- noscopy reported in the literature. 4 We present a case of culture-negative peritonitis in a peritoneal dialysis patient who underwent an endoscopic tattooing of a colon cancer. Optical microscopy of the peritoneal fluid revealed many Nephrology and Dialysis Unit Firenze II, Santa Maria Annunziata Hospital, Florence, Italy Corresponding author: Pietro Claudio Dattolo, Nephrology and Dialysis Unit Firenze II, Santa Maria Annunziata Hospital, Via Antella 58, 50012 Ponte a Niccheri, Bagno a Ripoli, Florence, Italy. Emails: pietroclaudio.dattolo@uslcentro.toscana.it; pcdattolo@gmail.com Figure 1. (a) Dark peritoneal fluid effluent 1 day after endoscopic marking with India ink of a colonic cancer lesion in a peritoneal dialysis patient. (b) Optical microscopy of peritoneal fluid after centrifugation (2500 r min 1  10 min). Macrophages in aggregates, full of pigment. (c) Papanicolaou coloration of peritoneal fluid (40) intense cellular reaction to India ink, macrophages in phagocytic phase (dark cells), cellular aggregates, cellular debris and fibrin. Peritoneal Dialysis International 1–2 ª The Author(s) 2020 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0896860820908134 journals.sagepub.com/home/ptd