Cowpers duct syringocele

Axial contrast-enhanced CT (top), axial T2W MRI (middle), and sag T2W with fat-saturation MRI (bottom)
demonstrate an ovoid cystic structure associated with the midline posterior aspect of the bulbous urethra

• The Cowper glands (bulbourethral glands) are paired pea-sized accessory exocrine glands analogous to the Bartholin glands in females
• The main glands lie within the urogenital diaphragm
• The ducts insert into the bulbous urethra  
• Provide lubrication of the urethra and protection of the sperm
• Obstruction of the ducts may result in formation of retention cysts, also referred to as syringoceles
• May be congenital or acquired 
• Most often asymptomatic although when large, may result in urinary obstruction and hematuria
• Categorized as either open or closed 
• Open cysts communicate with the lumen of the urethra and may mimic a urethral diverticulum or even an ectopic ureter
• More likely to cause symptoms of postvoid dribbling, purulent discharge and hematuria
• Closed or imperforate cysts become dilated due to duct obstruction resulting in cyst dilatation and extrinsic mass effect on the bulbar urethra
• More likely to result in obstructive symptoms
• Imaging typically detects a Cowper duct cyst as a unilocular cystic lesion at the posterior or posterolateral aspect of the posterior urethra 
• Open cysts may be opacified during urethrography 
• Closed cysts may appear as a smooth extrinsic filling defect on the ventral wall of the bulbous urethra 
• MRI is useful to exclude solid neoplasms and to detect complications such as hemorrhage or infection
• Symptomatic cases are treated surgically with cyst unroofing. Transperineal ligation of the Cowper gland ducts may be performed in refractory cases

References

1. Shebel HM, Farg HM, Kolokythas O, El-Diasty T. Cysts of the lower male genitourinary tract: embryologic and anatomic considerations and differential diagnosis. Radiographics. 2013 Jul-Aug;33(4):1125-43.
2. Surana S, Elshazly M, Allam A, Jayappa S, AlRefai D. A Case of Giant Cowper's Gland Syringocele in an Adult Male Patient. Case Rep Urol. 2015; 2015:682042.
3. Melquist J, Sharma V, Sciullo D, McCaffrey H, Khan SA. Current diagnosis and management of syringocele: a review. Int Braz J Urol. 2010 Jan-Feb;36(1):3-9.
4. Moskowitz PS, Newton NA, Lebowitz RL. Retention cysts of Cowper's duct. Radiology. 1976 Aug;120(2):377-80.
5. Kickuth R, Laufer U, Pannek J, Kirchner TH, Herbe E, Kirchner J. Cowper's syringocele: diagnosis based on MRI findings. Pediatr Radiol. 2002 Jan;32(1):56-8