If called an abscess why don't all toa's need to be drained.?

Tubo-ovarian abscess: Drainage of an abscess is ideal therapy assuming that they are large enough to drain appropriately, that the surgical procedure will not do more damage than benefit, and that the lesion is small enough to respond to antibiotic treatment without the necessity of drainage. This is often a clinical decision making process and why doctors need so much time in training.