I suspect it was the after effects of a nocturnal erection, and the fluid was from the Cowpers gland, which is usually left intact during the RRP. That's the gland that produces the pre-lube we are used to seeing as we become sexually excited.
Here's the wiki definition:
The Cowper's glands (bulbourethral gland) are male sexual glands. They are two small racemose glands that are located below the prostate and discharge a component of the seminal fluid into the urethra. They are homologous to the Bartholin's glands in the female. The secretions provide fluid to lubricate and clean the lower urethra, which may have residue left from its use during urination.
During sexual arousal each gland produces a clear, viscous secretion known as pre-ejaculate. This fluid helps to lubricate the urethra for spermatozoa to pass through, it neutralizes traces of acidic urine in the urethra, and helps flush out any residual urine or foreign matter. It is possible for this fluid to pick up sperm, remaining in the urethral bulb from previous ejaculations, and carry them out prior to the next ejaculation. (Wikipedia)
James C. Age 63
Gonna Make Myself A Better Man www.youtube.com/watch?v=a6cX61oNsRQ&feature=channel
4/07: PSA 7.6, Recheck after 4 weeks Cipro-6.7
7/07 Biopsy: 3 of 16 PCa, 5% invloved, left lobe, GS3+3=6
9/07: Nerve Sparing
open RRP, 110gms, Path Report- Stg. pT2c, 110 gms., margins clear
3 Years: PSA's .04 each test since surgery, ED continues: Bimix- .3ml PRN, Trimix- .15ml PRN