From the 1st paper I posted above:
“Postvasectomy Pain Syndrome
The pathophysiology underlying PVPS is a deviation from the natural progression of events within the ejaculatory system following disruption of the vas deferens. The definitive cause for PVPS is not known and may be the result of a number of subclinical processes occurring within the epididymis and further up into the spermatic cord. Theories have included epididymal congestion, painful sperm granulomas, vascular stasis, and nerve impingement.”
Journal of Andrology Volume 24, Issue 3
Testicular Pain Following Vasectomy: A Review of Postvasectomy Pain Syndrome
Cory G. Christiansen Jay I. Sandlow
First published: 02 January 2013
And the 1st article:
"Etiology of PVPS
The etiology of PVPS is still uncertain but there is some understanding of possible mechanisms for the pain. The currently available evidence suggests that several processes lead to the histological findings seen in PVPS. There may be a final common pathway leading to chronic testicular or epididymal pain that involves damage to scrotal nervous structures via immune system inflammatory effects, back pressure affects in the post-vasectomy closed system, or via perineural fibrosis from either of these processes.
Postulated etiologies for PVPS have included pressure from epididymal congestion, inflammation, or compression of paravasal nerves by sperm granuloma, interstitial fibrosis in the epididymides, or perineural fibrosis (14). Studies of epididymectomy specimens from patients with post-vasectomy pain have shown evidence of pathological changes possibly related to longstanding obstruction. This interstitial fibrosis and perineural fibrosis seen in the epididymides of affected men could explain the pain (15)."
December 4, 2014
Post-Vasectomy Pain Syndrome: Common but Hidden
Anthony R. Ellis, M.D., Assistant Clinical Professor
Department of Psychiatry, Michigan State University
Joseph E. Scherger, M.D., M.P.H., Clinical Professor
Department of Family & Preventive Medicine, University of California, San Diego
From the last article:
Post-vasectomy pain syndrome is a well-recognised, but poorly publicised complication of vasectomy. As is exemplified by this case, it is an intermittent or constant, unilateral or bilateral testicular pain that occurs for longer than three months and interferes with daily activities prompting the individual to seek medical advice.
Intermittent pains are often triggered by physical exertion, sexual activity or ejaculation. It may occur immediately postoperatively but more commonly develops months to years later.1
This delay is due to a gradual rise in pressure within the epididymis caused by continued production of sperm that are released into a system now closed by ties or clips on the vas deferens.
The painful build-up of sperm may be prevented or relieved by an ‘epididymal blowout’ or by recruitment of macrophages into sperm-destroying granulomas within the epididymis.2
Providers of vasectomy, both NHS and private, are encouraged by 2004 guidance from the Royal College of Obstetricians and Gynaecologists (RCOG) to inform men of the risk of chronic pain. However, general awareness of the complication remains low and information regarding the level of risk is often ambiguous.
The risk of chronic pain is commonly described as affecting ‘some men’ or ‘a very small number of men’. However, multiple UK-based studies of post-vasectomy pain have demonstrated that the proportion of men who develop pain after a vasectomy is almost 15%.
The number of men who seek medical advice or rate their pain as severe, and therefore qualify for a diagnosis of post-vasectomy pain syndrome, is up to 6%.3 This does not correlate with the level of risk described to patients and it may influence their decision."
Identifying the cause of testicular pain
By Dr Jonathan Pinnell and Dr Lorna MacColl on the 18 January 2012
Some men get a different reaction to the vasectomy from average , some significant pain occurs for up to 15%, 1/7.
A smaller number of men get more severe pain, between 1% and 6%, depending on source, so this occurs in 1/100 to 1/17. Most people posting here are in that bucket, or have been
Back pressure is one of the primary causes, and can still occur in open ended vasectomy at possibly lower rates but the open end tends toward closure over time , also these men may develop pain from sperm granulomas due to increased leakage into the scrotum.
For another group the pain comes from nerve damage during the procedure or possibly also from immune response.
Some men get all of these causes, nerve damage plus congestion, plus immune reaction, plus granulomas!
You have to now be the best informed potential vasectomy candidate regarding chronic pain risks ever at this point!
It’s your choice of this is a “good risk” however. Most people here in the 1% to 6% (1/100 to 1/17) with more severe levels of pain would not say so