Reply to Dr. Lapeyre: The Frost Sign

We thank Dr. Lapeyre for his interest in our case report [1] and for his comments. In his letter Dr Lapeyre describes mucosal pseudolipomatosis, which can appear as a white discoloration of the colon and which is also known as the “snow white sign”. In many instances this has been caused by a chemical colitis related to the use of peracetic acid or peroxide in the disinfection of colonoscopes.

In response to Dr. Lapeyre’s letter, we reviewed our endoscope disinfection process. Sterilox, superoxidised water, is currently used in our unit. This is a diluted mixture of mild oxidants at nearly neutral pH and its greatest single constituent is common salt. After the cleaning process the scope channel is routinely subjected to forced-air drying to render it “chemical free”. At no point in our disinfection process is a peroxide agent used. Furthermore, the frost sign appeared during the initial needle injection rather than after insufflation of the colon, as has been reported with the snow white sign of peroxide or peracetic acid colitis. A final observation that supports the incidental injection of air as a cause for the frost sign is that the cases described as pseudolipomatosis occurred in an epidemic pattern, unlike our case, which was solitary.

Therefore, although we recognise that chemical colitis is a potential cause of the snow white sign, we do not believe that it was responsible for the findings reported in our case. The lack of multiple cases, the timing of the changes and the absence of an incriminating agent argue against a chemical colitis as the cause of the appearance we described.

Reference

• 1 Suzuki N, Talbot I C, Saunders B P. The “frost sign”: an inadvertent minor complication of endoscopic mucosal resection.  Endoscopy. 2004;  36 835