Prostatic Cyst

A prostatic cyst is a fluid filled cavity in the prostate. Most are found incidentally on transrectal ultrasound or MRI, in about 1 to 5% of men.

Most are asymptomatic and need no treatment. Larger cysts can obstruct the ejaculatory ducts or the urethra, causing infertility, pain and infection.

Pathophysiology. Types:

• Prostatic utricle cyst: dilatation of the utricle, a remnant of the paramesonephric (Müllerian) duct, in the midline and often connected to the urethra. It contains no sperm.
• Müllerian duct cyst: midline cyst separate from the urethra, also without sperm.
• Ejaculatory duct cyst (Wolffian): lateral or paramedian, communicating with the ducts, and containing sperm.
• Retention cyst: from obstructed prostatic glands, often acquired, in older men with benign enlargement.
• Cystic degeneration of benign enlargement, parasitic cysts (hydatid), cystic neoplasm and abscess (rare).

Associations: proximal hypospadias and disorders of sex development (enlarged utricle), unilateral renal agenesis (seminal vesicle cyst with ejaculatory duct obstruction, Zinner syndrome), and cystic fibrosis spectrum disease.

Most men have no symptoms. Others have low semen volume and infertility, painful ejaculation, haemospermia, perineal pain, dysuria, weak stream, retention, recurrent urinary infection and epididymitis. In boys, a utricle cyst causes difficulty in passing a urethral catheter, post-void dribbling and infection. Stones can form in the cyst.

• Transrectal ultrasound: a well defined anechoic midline or paramedian cyst, with dilated seminal vesicles in obstruction. Debris suggests infection or haemorrhage.
• MRI of the pelvis: cyst contents, extent and relation to the urethra and ducts.
• Cyst aspiration under ultrasound: fluid containing sperm indicates an ejaculatory duct cyst, and sperm free fluid indicates a utricle or Müllerian duct cyst.
• Semen analysis (volume, pH, fructose, sperm count), and CFTR testing for absent vasa.
• Cystoscopy and urethrography for communication with the urethra. Renal ultrasound for agenesis. In children with hypospadias: karyotype and hormone testing.
• Urinalysis, culture and PSA when indicated.

Differential diagnosis.

• Seminal vesicle cyst
• Ejaculatory duct obstruction from other cause
• Retention cyst or cystic benign enlargement
• Prostatic abscess
• Cystic prostate cancer (rare)
• Hydatid or other parasitic cyst
• Bladder diverticulum

• Asymptomatic cysts: no treatment and no follow up.
• Infection: culture directed antibiotic. Ciprofloxacin 500 mg orally twice daily for 2 to 4 weeks (reduced when eGFR is under 50), or levofloxacin 500 mg once daily, for symptomatic infection, with longer courses when relapse occurs.
• Pain: ibuprofen 400 mg every 8 hours for up to 2 weeks with food, and tamsulosin 400 micrograms orally once daily after a meal for voiding symptoms.
• Symptomatic, obstructive or infertility related cysts:
  • Transurethral unroofing or resection of the cyst and ejaculatory ducts. Semen quality improves in about 50 to 75%, and pregnancy follows in about 20 to 30%.
  • Complications: epididymitis, urine reflux into the ducts, retrograde ejaculation, and rectal or bladder neck injury.
  • Ultrasound directed aspiration, with or without antibiotic instillation, gives temporary relief and recurs often. It is used for diagnosis, and for infected cysts.
  • Laparoscopic or robotic excision for large, recurrent or retrovesical cysts.
• Perioperative cefazolin 2 g intravenously (3 g if over 120 kg) as a single dose.
• Infertility with obstruction not amenable to surgery: sperm retrieval and intracytoplasmic sperm injection.
• Children: surgery for recurrent infection, stones or catheterisation problems, with management of hypospadias.

Monitoring. Semen analysis at 3 and 6 months after resection, and symptom review. Recurrence is possible.

Referral and escalation. Refer to urology for infertility, pain, recurrent infection, obstruction or stones. Urgent referral for retention or abscess.