A comprehensive narrative review evaluating the relationship between viral pathogens and chronic scrotal content pain suggests that viral orchiepididymitis may initiate persistent neuropathic discomfort through inflammatory mechanisms such as Wallerian degeneration. The research, published in Basic and Clinical Andrology by Thiago A. Teixeira, Eduardo Zinoni Pato, Maria Christina W. Avellar, Raul Sanchez, Igor V. Coimbra, Joël R. Drevet, and Jorge Hallak, synthesizes decades of clinical and laboratory investigations to address a clinical condition that frequently eludes definitive diagnosis. Chronic scrotal content pain, clinically defined as persistent or intermittent discomfort within the scrotum that significantly impairs daily activities and overall quality of life, represents a common complaint managed by andrologists worldwide. Epidemiological estimates reported in the study indicate a prevalence ranging from 0.4 percent to 4.75 percent, which translates to over 100,000 cases annually. Despite its relatively frequent clinical presentation, up to half of all affected patients show no identifiable intrinsic or extrinsic cause, resulting in extended diagnostic delays, inappropriate or ineffective treatments, and long-standing physical distress.
To investigate the potential role of viral infections in chronic scrotal discomfort, the investigators conducted a systematic literature search across PubMed, MEDLINE, and Web of Science for all relevant studies published up to November 2024. The structured search methodology incorporated Boolean keyword combinations, including viral testicular pain, viral orchiepididymitis, and chronic scrotal pain, restricting the search exclusively to English-language publications evaluating human clinical presentations of acute or chronic scrotal or testicular pain. Duplicates, studies involving non-human subjects lacking direct clinical or mechanistic relevance, and publications without therapeutic or diagnostic bearing were screened out. From an initial identification pool of 142 records, 61 published articles met the explicit inclusion criteria and underwent qualitative synthesis and thematic analysis. Through this evidence framework, the authors sought to address a notable imbalance in clinical literature: while bacterial pathogens have long been accepted as established contributors to epididymo-orchitis and subsequent pain, the pathogenic and neuropathic capacity of common viral infections has historically been overlooked in standard diagnostic and therapeutic algorithms.
The anatomical framework detailed in the review illustrates how structural and neurovascular characteristics of the male reproductive tract render the scrotal contents vulnerable to chronic pain syndromes. The ellipsoid testes, responsible for testosterone synthesis by interstitial Leydig cells and spermatogenesis within the seminiferous tubules, are situated within the scrotum, which provides mechanical protection and thermal regulation. Developing spermatozoa transit through the efferent ducts into the uncoiled seven-meter-long epididymis, divided into the caput, corpus, and cauda, where mature sperm are stored prior to entering the vas deferens. Innervation across these scrotal structures relies on complex somatic and autonomic networks. Somatic sensory innervation originates from spinal nerve roots L1-L2 and S2-S4 via the iliohypogastric, ilioinguinal, genitofemoral, and pudendal nerves. Autonomic innervation, organized into superior, middle, and inferior spermatic nerves originating from the renal, intermesenteric, superior hypogastric, and pelvic plexuses, provides sympathetic fibers primarily from T10-L1 and parasympathetic fibers from S2-S4. Furthermore, because internal scrotal structures share embryological origins and spinal cord sensory levels between T10 and L2 with the kidneys, ureters, bladder, prostate, and urethra, shared neuroanatomical pathways frequently lead to referred pain and diffuse clinical presentations.
Under normal physiological circumstances, peripheral nerve injury stimulates Wallerian degeneration, an inflammatory cascade where injured axons are degraded to establish an environment conducive to axonal regeneration. Following mechanical or inflammatory damage, an influx of calcium triggers cytoskeletal breakdown and axonal fragmentation. Concurrently, toll-like receptors on non-myelinating Schwann cells bind to molecular ligands released at the injury focus. This activation signals the production and secretion of pro-inflammatory cytokines, enhances regional vascular endothelial permeability, and recruits circulating neutrophils and macrophages to clear disintegrating myelin and cellular debris. In the first 48 hours following nerve insult, Schwann cells actively hydrolyze myelin phospholipids into phosphatidylcholine by upregulating phospholipase A2 before recruited macrophages complete phagocytic clearance. However, while Wallerian degeneration serves as an essential repair pathway, the concurrent release of pronociceptive chemical mediators by mast cells, neutrophils, macrophages, and Schwann cells can induce persistent peripheral sensitization. Consequently, aberrant or sustained Wallerian degeneration represents a leading mechanistic model explaining why neuropathic discomfort persists long after an initial localized insult has resolved.
The review outlines how viral infections can activate this degenerative neuropathic cascade through systemic and local immune responses. In contrast to bacterial infections, which cause well-documented gross structural inflammation and classic histological Wallerian degeneration, viral agents often provoke prolonged immune-mediated cellular stress. Following viral infiltration, the sustained release of pro-inflammatory cytokines, including interleukin-6, tumor necrosis factor, interferons, and chemokines like monocyte chemoattractant protein-1 and C-X-C motif chemokine ligand 10, continuously sensitizes peripheral nociceptive nerve fibers and alters central nervous system sensory processing. In addition, viral pathogens can initiate autoimmune neuropathic damage through molecular mimicry, wherein viral antigens share structural sequence homology with host cellular proteins, prompting plasma cells to produce cross-reactive antibodies such as the immunoglobulin G responses noted in Zika or Epstein-Barr virus infections. Persistent pain may also arise via bystander activation, in which non-specific immune activation triggers autoreactive T and B cells, or through the persistent release of endogenous epitopes and residual viral messenger RNA or proteins that maintain long-term localized inflammation.
Examining individual viral pathogens, the review synthesizes documented characteristics and clinical presentations across several major virus families. The mumps virus, an enveloped RNA pathogen belonging to the Paramyxoviridae family with documented tropism for testicular tissue, historically represents a prominent viral etiology of orchitis in post-pubertal males. While its post-vaccine incidence varies from less than 0.1 per 100,000 in the United States and Finland to between 10 and 30 per 100,000 per year in Thailand, orchitis remains a frequent complication, affecting both testicles in 10 to 30 percent of cases and leading to permanent subfertility in approximately 30 percent of affected men. In experimental murine models, mumps activates toll-like receptors and retinoic acid-inducible gene 1 pathways, prompting interstitial edema, vascular congestion, and intense mononuclear infiltration. However, because mumps orchitis typically follows a self-limiting acute clinical course, the review noted that direct investigative evidence connecting mumps infection to sustained nerve damage via Wallerian degeneration remains unverified in existing literature.
The authors also evaluated sexually transmitted and systemic viruses, including hepatitis B virus, herpes simplex virus, and human immunodeficiency virus. Hepatitis B, an enveloped DNA virus within the Hepadnaviridae family infecting more than 1.5 million individuals annually, demonstrates tropism for testicular endothelial cells and fibroblasts. In rare presentations, hepatitis B can trigger polyarteritis nodosa, causing immune complex deposition, testicular necrotizing vasculitis, and severe chronic testicular pain that may be biologically associated with Wallerian degeneration. Herpes simplex virus types 1 and 2, which establish life-long latency within nerve cells, can induce chronic prostatitis, urethritis, and epididymitis leading to persistent scrotal pain, although the physical blood-testis barrier restricts HSV-2 from entering the seminiferous tubules. For human immunodeficiency virus, testicular discomfort, irreversible hypogonadism, and sperm degradation are recognized clinical features. HIV infects CD4 T lymphocytes and stimulates extensive chronic testicular inflammation dominated by lymphocytic and macrocytic infiltration, suggesting that neuropathic axonal degradation is likely active even though definitive viral isolation from testicular biopsies is not uniformly documented.
Recent epidemiological and clinical attention has centered on emerging RNA pathogens, notably Zika virus and SARS-CoV-2. Zika virus, a mosquito-borne Flaviviridae virus that can also be sexually transmitted, causes acute orchitis, epididymo-orchitis, and chronic scrotal pain. In infected murine evaluations, the virus disrupted the blood-testis barrier, demonstrated by an absence of ETV5-positive cells and marked infiltration of CD45-positive leukocytes and F4/80-positive macrophages. SARS-CoV-2, an enveloped coronavirus that utilizes angiotensin-converting enzyme 2 receptors abundant within testicular and epididymal tissues, has demonstrated pronounced effects on male reproductive integrity. Post-mortem tissue examinations of patients who succumbed to COVID-19 revealed viral presence in the testes accompanied by fibrin microthrombi, interstitial edema, germ cell degeneration, seminiferous tubule damage, and lowered circulating testosterone levels. Additionally, clinical reports identified acute epididymitis in more than 50 percent of affected males. Laboratory observations also revealed that spermatozoa can generate extracellular traps consisting of cell-free nuclear DNA, paralleling systemic inflammatory extracellular trap responses that entrap infectious particles during severe infection.
Despite these extensive immunological and histopathological observations, the authors highlight significant limitations across the published literature. To date, there is no direct experimental or histological data definitively demonstrating Wallerian degeneration in chronic scrotal pain following viral orchitis or epididymitis, in sharp contrast to bacterial epididymo-orchitis where axonal degeneration is clearly documented. The existing scientific literature remains sparse, comprising predominantly small, heterogeneous observational studies, case series, and narrative reports that lack standardized diagnostic criteria. Consequently, establishing causal inference between specific viral exposures and permanent peripheral nerve degeneration remains challenging. The authors emphasize that examining human tissue and nerve biopsies from individuals experiencing chronic post-viral scrotal symptoms could provide essential diagnostic clarity, allowing clinicians to definitively differentiate between ongoing active infection, post-infectious autoimmune irritation, and structural axonal degeneration.
These mechanistic insights suggest practical shifts in clinical management for patients presenting with idiopathic chronic scrotal pain. Because standard urological guidelines primarily emphasize bacterial cultures and empirical antibiotic regimens, incorporating targeted viral screening—especially when bacterial evaluations remain negative—could minimize diagnostic delays and prevent unnecessary antimicrobial exposure. Furthermore, recognizing potential neuropathic components supports the earlier adoption of anti-inflammatory and neuromodulatory pain management protocols. Given documented associations between viral orchitis and testicular endocrine disruption, routine endocrine evaluations for hypogonadism and follow-up semen analyses are warranted to monitor testosterone production and fertility preservation. Ultimately, the authors conclude that multidisciplinary care integrating andrology, infectious disease, and pain management, combined with preventative vaccination programs against orchitis-inducing viruses, will be crucial to clarify viral-induced Wallerian degeneration and improve long-term reproductive outcomes worldwide.
Subject of Research: Viral orchiepididymitis and Wallerian degeneration in chronic scrotal content pain
Article Title: Chronic scrotal content pain and viral orchiepididymitis: an overlooked hypothesis linking infection and Wallerian degeneration
Article References: Teixeira, T. A., Pato, E. Z., Avellar, M. C. W., Sanchez, R., Coimbra, I. V., Drevet, J. R., & Hallak, J. (2026). Chronic scrotal content pain and viral orchiepididymitis: an overlooked hypothesis linking infection and Wallerian degeneration. Basic and Clinical Andrology, 36(1), Article 6. https://doi.org/10.1186/s12610-026-00301-9
Image Credits: AI Generated
DOI: 10.1186/s12610-026-00301-9
Keywords: chronic scrotal content pain, viral orchiepididymitis, Wallerian degeneration, neuropathic pain, andrology, SARS-CoV-2, Zika virus, mumps orchitis, testicular innervation, epididymitis, Chronic, scrotal
News Source: Kristina Jarvis. (November 6, 2026). Review Examines How Viral Infections Might Trigger Chronic Scrotal Content Pain. Scienmag.
