It is believed that a bezoar develops when substances ingested as food and those such as hair that have been accidentally ingested become an insoluble calculus-like mass within the stomach. This phenomenon was first reported in 1779 by Baudamant. In Japan, the phytobezoar of a persimmon bezoar is frequently found. One type of lecoanthrocyanis, which is one component of persimmons, becomes insoluble and thereafter forms a calculus. In addition, it has been reported that bezoars are often observed in cases with diabetes and an impaired gastric excretion after gastric surgery. The present case also involved a persimmon bezoar. It appears that the stomach was likely underactive due to diabetes and unilateral paralysis, which may have led to an impaired gastric excretion.

There have been reports on the methods for treating bezoars, including surgical treatment, endoscopic lithotripsy, electrohydraulic lithotripsy, laser therapy, and even the use of extracorporeal shock wave lithotripsy (ESWL). In 2002, Ladas[1] reported a method of dissolution with Coca-Cola. The report describes that, in 5 cases of bezoars, it was found that the bezoars disappeared after irrigating approximately 3 liters of Coca-Cola within a 12-hour period via a gastric tube into the stomach. Chung[2] then reported on the injection of Coca-Cola directly into the bezoar via a puncture needle. Referring to past reports [1–9], the period from the administration of Coca-Cola until the disappearance of the bezoars was a minimum of 1 day and a maximum of 2 months. In the present case, the patient refused an indwelling gastric tube, and therefore 500–1,000 ml of Coca-Cola was administered orally. This may be the reason why it required a relatively long period for the bezoar to decrease in size.

It has not been revealed why persimmon bezoars melt after coming in contact with Coca-Cola. However, one explanation is that Coca-Cola, which contains carbonic acid and phosphoric acid, is acidic with a pH of 2.6 and thus creates a gastric environment similar to that of a normal state of gastric acid secretion[1]. Another explanation is that the fine bubbles of carbonic acid permeate the microscopically uneven surface of the bezoar[2]. Typically, a persimmon bezoar is extremely hard, which often makes it difficult to carry out an endoscopic lithotripsy. However, in the present case as well, the surface became uneven and softened, thereby allowing the successful performance of lithotripsy using forceps.

Consequently, the method of dissolving bezoars with Coca-Cola appears to be a safe, convenient, and economically feasible treatment modality.