The “Frost Sign” and the “Snow White Sign”: Intramucosal Air Injection or Peroxide Colitis?

 

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I read with interest the recent case report by Suzuki et al. [1] in which the authors describe seeing an “unusual white appearance” during colonoscopy, which was thought to be a direct consequence of intramucosal air injection during an endoscopic mucosal resection procedure. I found the endoscopic and pathological images highly suggestive of mucosal pseudolipomatosis, often referred to as the “snow white sign”. This condition is characterized histologically by the presence of optically empty, unlined spaces within the colorectal lamina propria, grossly similar to fat but actually accounted for by the presence of intramucosal gas [2]. Endoscopic examination reveals what are usually described as “white plaques” and these are sometimes seen to extend during the examination. It is a benign condition which regresses spontaneously, and usually causes transient mild symptoms or is asymptomatic.

Different pathogenetic mechanisms have been hypothezised for this condition, including intramucosal penetration of air during insufflation, biopsy, or other procedures [3] [4]. There have, however, been many reports linking this condition to a chemical colitis caused by the peroxide agents used in the disinfection of endoscopes.

Acute colitis due to hydrogen peroxide enemas has been well described, some reports documenting the finding of intramucosal gas in such cases [5]. Jonas et al. [6] reported their experience of 21 cases in which perendoscopic mucosal changes suggestive of pseudomembranous colitis occurred after using colonoscopes flushed with 3 % hydrogen peroxide. Bilotta & Waye [7] described the onset of mucosal blanching of the colonic mucosa upon insufflation, which they called the “snow white sign”. This occurred in seven patients during a 2-week period, while the endoscopes had been flushed with 3 % hydrogen peroxide. Ryan & Potter [8] reported the appearance of white mucosal changes during colonoscopies, with changes characteristic of pseudolipomatosis seen on histological examination, and regarded these findings to be due to a direct toxic effect of the hydrogen peroxide which had been used as a disinfectant. A similar condition was described by Coton et al. [9] but, this time, the peracetic acid that had been used as a disinfective agent was blamed. (This chemical releases hydrogen peroxide when in contact with water.)

We have recently observed several cases of the snow white sign, with typical histological findings of pseudolipomatosis, in an epidemic pattern, within a period of a few weeks in our unit. This occurred shortly after we exchanged our old disinfection equipment for a new semiautomated unit which uses peracetic acid. As in the other cases involving peracetic acid [9], there was a technical failure in the rinsing of the air channel, leading to vaporization of residues of peracetic acid and its peroxide derivatives during insufflation. No further cases were seen after correction of this technical fault.

All these reports seem to describe the same entity, unequivocally due to a peroxide colitis, which should be suspected first when such “white” signs are seen during colonoscopy when a peroxide agent has been used at some stage during disinfection. Cases like these should lead to a thorough check of the entire disinfection process, paying special attention to the rinse cycle of the endoscope channels.

In the case presented by Suzuki et al. [1], it seems that these mucosal changes appeared immediately during a needle injection, leading to the hypothesis that they had been caused by an incidental intramucosal air injection. However, I wonder if a peroxide colitis could have been involved in this case, at least as a co-factor. In this regard, it would be interesting to know whether or not peracetic acid or another peroxide agent was used during the disinfection procedure.

References

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B. Lapeyre, M.D.

Department of Gastroenterology, Polyclinique Saint-Côme

72 Rue Carnot 60200 CompiegneFrance

Fax: +33-3-44205692

Email: scheithelapeyre@tele2.fr