The Symplicity renal denervation system consists of a flexible catheter and proprietary generator.

FORBES: About the Symplicity? Renal Denervation System

They ended up producing a flexible catheter tube that goes a bit of the way up the nostrils, then a guide wire is inserted into the targeted sinus. (In live patients this is done via an endoscope and fluoroscope.) A balloon catheter is advanced over the guide wire and positioned against the blocked ostium.

FORBES: Balloon Therapy

In bladder instillation, the prescription medication dimethyl sulfoxide, or DMSO, (Rimso-50) is placed into your bladder through a thin, flexible tube (catheter) inserted through the urethra.

CNN: Interstitial cystitis

He'd spent eight years developing a special kind of Foley catheter--a flexible tube inserted into the bladder of hospital patients and disabled people to drain urine--that staved off inevitable infections.

FORBES: Magazine Article

That changed just over a year ago, when Edwards Lifesciences Corp. won approval to sell an artificial aortic valve flexible and small enough to fit into a catheter and wedged inside the bad one.

NPR: Heart Repair Breakthroughs Replace Surgeon's Knife

Then a thin, flexible wire was threaded through the needle, and the needle and catheter were removed.

BBC: 'Revolution' in heart bypass ops