Introduction
Cysts of the seminal vesicles usually become apparent in the second to third decade during the period of greatest sexual or reproductive activity. Seminal vesicle cysts less than 5 cm may remain asymptomatic and are usually discovered incidentally as a palpable abdominal mass or on digital rectal examination as a palpable fluctuant mass arising from the superior aspect of the prostate gland.

Clinical Features
These cysts also may present with symptoms related to bladder irritation and obstruction. Commonly reported symptoms include abdominal, perineal, and pelvic pain; ejaculatory pain; dysuria; frequency; hematuria; urinary tract infections; and symptoms of epididymitis and prostatitis. Other reported symptoms include infertility, hemospermia, and, rarely, enuresis. Cysts of the seminal vesicles greater than 12 cm have been termed "giant" cysts and often are present with symptoms of bladder and colonic obstruction because of mass effect. Less commonly, seminal vesicle cysts have been discovered in prepubertal boys examined for epididymitis and chronic urinary tract infections.

Seminal vesicle cysts may be congenital or acquired. Present since birth, congenital cysts develop and become symptomatic in young adulthood. Accumulation of secretions in the gland owing to insufficient drainage, which is associated with atresia of the ejaculatory ducts, causes subsequent distention of the seminal vesicles, leading to formation of a cyst. The cysts are usually unilateral with no predilection for side. Acquired cysts are often bilateral and are seen in an older age group after a history of chronic prostatitis or prostate surgery.

Embryology
Normal development of the kidney depends on induction by the ureteral bud and mesonephric duct. Complete failure of the mesonephric duct will result in absence of the ipsilateral kidney, ureter, hemitrigone, and seminal vesicle. Failure of the ureteral bud to develop and meet the metanephric blastema will lead to ipsilateral renal agenesis or dysplasia; however, the seminal vesicle will develop normally. If the ureteral bud arises in a more cephalic position off the mesonephric duct, delayed absorption of the caudal mesonephric duct will result in the distal ureteral bud emptying into mesonephric duct derivatives, including the vas deferens, seminal vesicle, ejaculatory duct, or into the bladder neck and urethra.

Differential Diagnosis
The differential diagnosis of cystic pelvic masses in the male includes müllerian duct cysts and ejaculatory duct cysts, both of which are midline in location. The presence of spermatozoa in the aspirate may differentiate seminal vesicle cysts from müllerian duct cysts. Other possibilities include prostatic cysts and, more lateral in location, diverticulosis of the ampulla of the vas deferens, ectopic ureterocele, and abscess. Tumors in a seminal vesicle cyst associated with ipsilateral renal agenesis are exceedingly rare, with two cases of papillary adenocarcinoma reported.

IVP
Excretory urography can show ipsilateral renal dysgenesis and an abnormal appearance of the collecting system. A large cyst may display an extrinsic smooth-walled filling defect in the bladder that is suggestive of a seminal vesicle cyst

Computed Tomography
May display a cystic pelvic mass with a thick irregular wall to a solid mass and apparent enlargement of the ipsilateral seminal vesicle. Other findings could include a well-defined low-attenuation retrovesicular mass arising from the seminal vesicle, cephalic to the prostate gland, with associated renal anomalies.

MRI
The multiplanar ability of MR imaging to define abdominal and pelvic anatomy and to differentiate cystic malformations of the pelvis make it the ideal imaging study.

The usual appearance of a seminal vesicle cyst is that of cysts located elsewhere in the body, showing low T1-weighted and high T2-weighted signal intensity. However, seminal vesicle cysts may show increased T1-weighted and T2-weighted signal intensity, thought to reflect increased concentration of proteinaceous material or hemorrhage.

Treatment
Surgical excision of a seminal vesicle cyst depends on the size and location of the cyst and presence of clinical symptoms. MR imaging may be helpful to accurately show anatomic relationships particularly in the setting of surgical planning for seminal vesicle cyst excision.

References

Livingston L & Larsen C. Seminal Vesicle Cyst with Ipsilateral Renal Agenesis. AJR 2000, 175: 177-180

King BF, Hattery RR, Lieber MM, Berquist TH, Williamson B Jr, Hartman GW. Congenital cystic disease of the seminal vesicle. Radiology 1991;178:207 –211

Sheih C-P, Hung C-S, Wei C-F, Lin C-Y. Cystic dilatations within the pelvis in patients with ipsilateral renal agenesis or dysplasia. J Urol 1990;144:324 –327.

Rappe BJM, Meuleman EJH, Debruyne FMJ. Seminal vesicle cyst with ipsilateral renal agenesis. Urol Int 1993;50:54 -56

Heaney JA, Pfister RC, Meares EM Jr. Giant cyst of the seminal vesicle with renal agenesis. AJR 1987;149:139 -140

Kenney PJ, Leeson MD. Congenital anomalies of the seminal vesicles: spectrum of computed tomographic findings. Radiology 1983;149:247 –251

Trigaux J-P, Van Beers B, Delchambre F. Male genital tract malformations associated     with ipsilateral renal agenesis: sonographic findings. J Clin Ultrasound 1991;19:3 -10