Endovascular prostheses used to treat diseased blood vessels, such as arteries, are disclosed. In some embodiments, an endovascular prosthesis is configured to be implanted within a diseased blood vessel adjacent a diseased section. The endovascular prosthesis may include a fenestration tube through which a guidewire extends in a sealed configuration. The fenestration tube can be selectively openable and configured to sealingly receive an expandable endovascular prosthesis that extends into a side branch vessel of the diseased blood vessel.