If left untreated, the condition may become chronic.

如果得不到治疗，此病可能会转成慢性。

《柯林斯英汉双解大词典》

If left untreated, decay goes deeper and deeper into the tooth.

如果不及时治疗，蛀牙会越来越深。

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If decay is left untreated, it will reach the tooth's pulp.

如果龋坏没得到治疗，它将进入牙髓。

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When left untreated,however, it can lead to changes in a person's physical appearance and even death.

VOA: special.2010.07.06

Lupus can be life threatening if left untreated.

VOA: special.2009.04.14

If left untreated,fistula can cause other health problems.

VOA: special.2010.08.09

In a worst-case scenario, if left untreated, this condition could increase the chance of developing cancer.

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When left untreated, the disease can cause infertility in women and painful, oozing inflammation in men.

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Instead, it detects abnormalities which, if left untreated, could lead to cancer in a woman's cervix.

BBC: Cervical screening: Third of Nottingham women miss tests