Can an extruded disc fragment at l5-s1 go away without dissection?

Not usually: Are you symptomatic? It depends where the fragment is in relation to the herniated disc (anterior, posterior, lateral placement, and how big it is, and whether it's impinging on anything or not). Need to speak to your spine specialist about this further, as s/he did the physical exam, and has the imaging needed to answer this question more fully.

Yes. : Unless you have severe pain or weakness always try therapy first