Seminal vesicle cyst is a cystic lesion developing within or around the seminal vesicle. It can be congenital or acquired. The congenital form is usually associated with Wolffian duct anomalies and may be part of the Zinner syndrome triad (ipsilateral renal agenesis + seminal vesicle cyst + ejaculatory duct obstruction). Acquired forms result from seminal vesicle obstruction, chronic infection, or post-surgical changes. Most are asymptomatic and discovered incidentally, but large cysts may cause pelvic pain, dysuria, ejaculatory pain, or infertility. On mpMRI, it appears as a T2 hyperintense, non-enhancing, well-defined cystic lesion. In PI-RADS v2.1 classification, it is considered a benign finding and not included in scoring.
Age Range
20-50
Peak Age
35
Gender
Male predominant
Prevalence
Uncommon
Congenital seminal vesicle cysts develop from atresia or ectopic drainage of the distal segment of the Wolffian (mesonephric) duct. The Wolffian duct is embryologically the common precursor of the ureteral bud, epididymis, vas deferens, seminal vesicle, and ejaculatory duct — therefore, anomalies can affect all these structures and present with ipsilateral renal agenesis (Zinner syndrome). Ejaculatory duct obstruction leads to accumulation of seminal vesicle secretions and cystic dilatation. Acquired cysts result from ejaculatory duct blockage due to chronic prostatitis, seminal vesiculitis, or post-surgical fibrosis. On imaging, the cyst contains pure fluid or proteinaceous secretions, producing bright signal on T2 and dark (simple fluid) or bright (proteinaceous/hemorrhagic) signal on T1. Absence of enhancement is due to the cyst wall being lined by avascular simple epithelium.
When a T2 hyperintense cystic lesion is found in the seminal vesicle of a young male patient, the ipsilateral kidney should be evaluated. Presence of ipsilateral renal agenesis confirms Zinner syndrome — representing the full spectrum of Wolffian duct anomaly. This triad is pathognomonic and the most important diagnostic clue for congenital seminal vesicle cyst. Ejaculatory duct obstruction is assessed by dilated appearance of the ejaculatory duct on MRI or indirectly by fluid accumulation in the seminal vesicle.
On T2-weighted images, markedly hyperintense (fluid signal), well-defined, thin-walled cystic lesion in the seminal vesicle region. Usually oval or tubular morphology following normal anatomical configuration of the seminal vesicle. Internal structure is homogeneous with no septa or solid component (simple cyst). In the presence of proteinaceous content, signal may be heterogeneous but remains hyperintense.
Report Sentence
Well-defined cystic lesion with markedly hyperintense signal on T2-weighted images in the seminal vesicle, consistent with seminal vesicle cyst.
On T1-weighted images, cysts with simple fluid content are hypointense (water signal). Cysts with proteinaceous or hemorrhagic content may be hyperintense on T1. This signal variation reflects the nature of cyst content and is important for content characterization rather than benign/malignant differentiation.
Report Sentence
Seminal vesicle cyst showing hypointense/hyperintense signal on T1-weighted images, consistent with simple/proteinaceous content.
On diffusion-weighted images, simple cyst shows no diffusion restriction — signal drops at high b-values and high signal (long ADC value) is observed on ADC map. This finding confirms the cyst contains simple fluid and no cellular solid component is present. Diffusion restriction may be seen in infected cyst or abscess.
Report Sentence
Seminal vesicle cyst showing no diffusion restriction, consistent with simple cystic structure.
On contrast-enhanced sequences, the cyst shows no enhancement — thin wall may show faint enhancement but no solid component or nodular enhancement is present. Absence of enhancement confirms the avascular simple cystic nature of the lesion and differentiates it from solid tumors (particularly prostate cancer with seminal vesicle invasion).
Report Sentence
Seminal vesicle cyst showing no enhancement on contrast-enhanced sequences, consistent with benign cystic structure; no finding of seminal vesicle invasion identified.
On transrectal ultrasonography (TRUS), anechoic or hypoechoic, well-defined cystic lesion in seminal vesicle region. Posterior acoustic enhancement is observed. Located posterosuperior to prostate at expected seminal vesicle anatomical location. Thin wall and absence of internal echoes is consistent with simple cyst.
Report Sentence
Anechoic cystic lesion with posterior acoustic enhancement in the seminal vesicle on TRUS, consistent with seminal vesicle cyst.
On CT, well-defined, non-enhancing cystic lesion at water density (0-20 HU) in the seminal vesicle region. Thin smooth wall. Posterosuperior to prostate at normal seminal vesicle location. CT is less sensitive than MRI for diagnosis of seminal vesicle cyst but can detect large cysts and is important for evaluating ipsilateral renal agenesis.
Report Sentence
Non-enhancing cystic lesion at water density in the seminal vesicle region on CT, consistent with seminal vesicle cyst.
Criteria
Associated with Wolffian duct anomaly. Forms triad with ipsilateral renal agenesis and ejaculatory duct obstruction. Usually diagnosed in young men aged 20-40. Unilateral seminal vesicle cyst + ipsilateral kidney absence confirms diagnosis.
Distinct Features
Young patient, unilateral, ipsilateral renal agenesis, ejaculatory duct dilatation, vas deferens anomaly may be present
Criteria
Occurs after chronic prostatitis, seminal vesiculitis, pelvic surgery, or radiotherapy. Ejaculatory duct obstruction is due to acquired causes. May be bilateral. More common at older age. No renal anomaly accompanies.
Distinct Features
Older age, surgical/RT history, may be bilateral, no renal anomaly, infectious history
Criteria
Size >5 cm or symptomatic (pelvic pain, dysuria, ejaculatory pain, infertility). May become infected — shows diffusion restriction in this case. May compress bladder or rectum. May require surgical excision or percutaneous drainage.
Distinct Features
>5 cm, symptomatic, compression signs, infection risk, surgical/drainage indication
Distinguishing Feature
Müllerian duct cyst is midline and extends above the prostate (pear-shaped). Seminal vesicle cyst is lateral, following seminal vesicle anatomy. Müllerian duct cyst starts from verumontanum level and extends cranially — seminal vesicle cyst remains localized in the seminal vesicle region.
Distinguishing Feature
Utricle cyst is midline, at verumontanum level, and does NOT extend above the prostate (small and confined). Seminal vesicle cyst is lateral and located outside the prostate in the seminal vesicle region. Utricle cyst is usually <10 mm and remains within the prostate.
Distinguishing Feature
When prostate adenocarcinoma invades the seminal vesicle (T3b), it shows focal T2 hypointensity and enhancement. Seminal vesicle cyst is T2 hyperintense with no enhancement. In SVI, normal tubular architecture of seminal vesicle is disrupted with mass effect — in cyst, structure is preserved and cystic morphology continues.
Distinguishing Feature
Prostate abscess shows diffusion restriction (DWI hyperintense, low ADC), thick irregular wall and surrounding tissue inflammation (edema). Seminal vesicle cyst shows no diffusion restriction, thin smooth wall, and no surrounding tissue reaction. Clinically, abscess presents with fever and leukocytosis.
Urgency
routineManagement
conservativeBiopsy
Not NeededFollow-up
no-follow-upAsymptomatic seminal vesicle cysts are benign findings requiring no treatment or follow-up. In PI-RADS v2.1, they are considered benign findings — not affecting scoring in prostate cancer screening. Symptomatic large cysts (pelvic pain, dysuria, infertility) may be treated with surgical excision or transrectal aspiration. In suspected Zinner syndrome, upper urinary tract and ipsilateral kidney should be evaluated. In patients with infertility complaints, ejaculatory duct obstruction should be assessed and urology consultation obtained.
Seminal vesicle cysts are usually asymptomatic. Symptomatic ones may present with hemospermia, perineal pain, or dysuria. In Zinner syndrome, ipsilateral renal agenesis should be investigated. Treatment is only needed for symptomatic cysts (aspiration or excision).