Medical infusion methods and systems

A method of providing an infusion, the method comprising:

• providing a cannula catheter comprising a catheter shaft;
• providing an infusion cannula comprising a cannula shaft, the cannula shaft being at least partially slidably disposed within a first lumen portion of the catheter shaft;
• transvascularly advancing the catheter shaft carrying the cannula shaft to a renal vein;
• and
• advancing the cannula shaft relative to the catheter shaft to position a distal end of the cannula shaft externally of the first lumen portion through a side opening of the catheter shaft to puncture a renal vein wall portion and access renal tissue.

A method of providing an infusion, the method comprising:

• providing a medical infusion system;
• transvascularly accessing a kidney, using the medical infusion system, to provide a transvascular access site in an inner renal medulla of the kidney;
• puncturing a vascular wall portion, using the medical infusion system, to provide an opening in the vascular wall portion at the transvascular access site;
• and
• infusing into tissue of the inner renal medulla, using the medical infusion system, a solution comprising an oncotically active agent through the opening in the vascular wall portion at the transvascular access site.