This usually occurs within a year. In the first stage, inflammation, oedema or necrosis occurs within the first few days after the injury, often with early signs of oesophageal obstruction; in the second stage, about 1 to 2 weeks after the injury, the necrotic tissue begins to fall off and soft, red granulation tissue appears, and the symptoms of obstruction can often be reduced, when the oesophageal wall is at its weakest, lasting about 3 to 4 weeks; in the third stage, scarring and stricture form, and the evolution can last weeks to months, but it is less common for patients to have a recurrence of stricture after more than 1 year.