House Wiki

The bladder is an elastic organ that collects urine that has been processed by the kidneys until it is excreted through the urethra.

Because the urethra is shorter in females, they are far more susceptible to bladder infections. Sterile urine tends to protect the bladder from infection.

In Honeymoon, House draws urine directly from the bladder through a syringe when the catheter falls out during a test for porphyria.

Urinary bladder at Wikipedia