This is a follow-on from:
EricE's: "Radical Prostectomy and Penis Growth?"
Not to be confused with loss of function & the need for "rehabilitation".
Looking at the studies, one is struck by the seeming indifference to the problem. Men must have been complaining of the issue, or at least remarking on it, ever since prostatectomies began.
It is not until a 2017 paper that I see an explanation given:
"Anatomically, the glans and corpus spongiosum surrounding the urethra are an integral structure, and the proximal urethra is drawn into the pelvis during urethrovesical anastomosis." [5]
"urethrovesical anastomosis" is the reconnection of the urethra after the prostate has been removed. If the prostate is the size of a walnut, as is often said, one gets an idea of how much urethra has been lost.
Here is a video of the procedure:
quilldevice.com/video-libra...
[1] (2001)
This is the first study I found - conducted:
"because an occasional complaint from patients after RRP is that their penis is shortened."
"The results of this pilot study appear to show that the stretched penile length decreases after RRP at 3 months of follow-up in most men; 48% (15 of 31) had considerable shortening greater than 1.0 cm. If confirmed by other investigators, the cause of this change needs to be elucidated."
The authors appear shocked.
[2] (2003)
"Twelve patients (19%) had a 15% or greater decrease in stretched penile length."
"Men should be counseled before radical prostatectomy that penile shortening may occur."
I asked my surgeon about this before my RP. He claimed to have never seen a case.
[3] (2007)
Italian study reported that:
"Penile shortening after radical prostatectomy peaks at the time of catheter removal and it continues to a lesser but still significant degree for at least 1 year."
{That was my experience too.}
[4] (2012)
A Brazilian long-term study:
"The mean stretched penile length 3 months after RP decreased an average of 1 cm from baseline... This mean difference persisted until 24 months. At 36 months, the penile length differed 0.6 cm. At 48 months (-0.3 cm) and 60 months (+0.4 cm), the mean differences in penile length before and after RP were not significant"
[5] (2017)
A Japanese study:
"The SPL {stretched penile length} was shortest 10 days after RP (mean PL shortening from preoperative level: 19.9 mm), and gradually recovered thereafter. SPL at 12 months after RP was not significantly different from preoperative SPL. On MRI examination, the distal end of membranous urethra was found to have moved proximally (mean proximal displacement: 3.9 mm) at 10 days after RP, and to have returned to the preoperative position at 12 months after RP."
[1] ncbi.nlm.nih.gov/pubmed/115...
[2] ncbi.nlm.nih.gov/pubmed/126...