Various devices for the treatment of disorders of the prostate gland, for example benign prostatic hyperplasia(BPH), are known in the art. 
Treatment of obstructive tissue in the prostate urethra with a balloon catheter is disclosed in U.S. Pat.  No.  4,660,560 which describes a catheter having a Foley balloon for anchoring the catheter by inflation within the bladder, and an annular balloon for dilation of the prostate urethra. 
U.S. Pat.  Nos.  4,932,958 and 4,932,956 disclose an apparatus for dilation of the prostate urethra which comprises a catheter for insertion in the prostate urethra having dilation means and spaced-apart location means, the preferred embodiment of the dilation means being an inflatable balloon. 
The above devices treat the prostate disorder by dilation of the prostate urethra.  Another approach is to treat the prostate by radiant energy.  Typical treatments are by electromagnetic radiation, particularly in the microwave range; and by ultrasound.  For example, U.S. Pat.  No.  5,007,437 discloses a device comprising a catheter adapted to be inserted into the prostate of a male patient, which catheter comprises an inflatable balloon containing a microwave antenna for irradiating the prostate with a given distribution of microwave field intensity, thereby to heat the prostatic tissue.  Care has to be taken to limit the maximum microwave power so that the temperature of the heated tissue does not exceed a given safe maximum temperature. 
One of the ways to monitor temperature during treatment of the prostate is to utilize a rectal probe containing a temperature sensor. 
International Application Publication No.  WO 91/15174 discloses a rectal probe having a body made of a flexible, self-supporting polymer wherein the flexibility is defined by a Shore hardness A less then about 90.  This publication discloses a therapeutic treatment apparatus which comprises a rectal probe and contains means for hyperthermal treatment of tissue, especially the prostate. 
It has now been found that accurate monitoring of temperature during transurethral thermal treatment of the prostate is achieved by the use of a novel rectal probe comprising a balloon catheter having a temperature sensor attached to one wall of the balloon.