Catheter
A thin flexible tube inserted into the body to drain fluid or deliver treatment.
What it means
A catheter is a thin tube placed into a body cavity or vessel, either to drain something out or to deliver something in.
Unqualified, the word usually means a urinary catheter, passed into the bladder to drain urine. An indwelling catheter stays in place, held by a small inflated balloon; an intermittent catheter is passed and removed each time.
Cardiac catheters are threaded through blood vessels to the heart for angiography and stenting; central venous catheters deliver drugs into a large vein.
In practice
Long-term urinary catheters almost invariably grow bacteria. Bacteria in the urine of a catheterised person with no symptoms is expected and should not be treated with antibiotics, since treating it drives resistance without benefit.
Why it matters
A catheterised person with fever, new confusion, loin pain or feeling systemically unwell should be assessed — that is genuine infection rather than colonisation.
A catheter that stops draining, with abdominal pain or distension, requires same-day attention.
Catheter problems are among the situations we cannot manage remotely and would direct to a district nurse or urgent care.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026