Prostatic Calculi

Prostatic calculi are calcified concretions within the prostate. They are very common, found on ultrasound in about 70 to 90% of men over 50, and are usually harmless.

They matter when they cause pain, voiding symptoms, haematuria or recurrent infection, because they hold bacteria that antibiotics do not reach.

Pathophysiology. Two types:

• Endogenous (corpora amylacea) calculi, formed by calcification of secretions in the acini. They are small, multiple, scattered and related to age and benign enlargement.
• Exogenous (ductal) calculi, formed when urine refluxes into the prostatic ducts, depositing calcium phosphate and carbonate apatite, and sometimes struvite in infection. They are larger and cluster near the urethra.

Associated conditions: benign prostatic enlargement, chronic prostatitis and chronic pelvic pain syndrome, urethral stricture and bladder outlet obstruction, and ejaculatory duct obstruction. Large calculi may obstruct the prostatic urethra or ducts.

Usually asymptomatic. Symptoms when present: perineal or suprapubic pain, painful ejaculation, haemospermia, lower urinary tract symptoms, recurrent urinary infection, and relapsing prostatitis. A large calculus may be felt on rectal examination as a gritty nodule.

• Transrectal ultrasound: hyperechoic foci with or without acoustic shadowing, scattered, clustered or lining the urethra.
• Pelvic CT or plain film shows calcification, and MRI shows signal voids.
• Urinalysis and culture, first void urine nucleic acid tests, and the two glass or four glass test for chronic infection.
• PSA may be moderately raised. Interpret with prostate volume and repeat after infection is treated.
• Uroflowmetry, post-void residual and cystoscopy or urethrography for obstruction and stricture.
• Semen analysis when fertility is at issue.

Differential diagnosis.

• Calcification in prostate cancer
• Chronic prostatitis
• Urethral calculus
• Calcified benign prostatic nodules
• Tuberculosis or schistosomiasis of the prostate
• Calcified seminal vesicles or vas deferens
• Brachytherapy seeds or surgical clips

• Asymptomatic calculi: no treatment.
• Chronic bacterial infection with calculi: culture directed antibiotics with prostatic penetration for 4 to 6 weeks, repeated for relapse.
  • Ciprofloxacin 500 mg orally twice daily, with the dose reduced to 250 to 500 mg every 12 hours when eGFR is 30 to 50, and every 24 hours when under 30.
  • Levofloxacin 500 mg once daily, reduced when eGFR is under 50.
  • Co-trimoxazole 960 mg twice daily (halved when eGFR is 15 to 30, avoided when under 15).
  • Doxycycline 100 mg twice daily for 2 to 4 weeks for atypical organisms.
• Relapse prevention: low dose suppression with nitrofurantoin 50 to 100 mg orally at night (eGFR over 45) or trimethoprim 100 mg at night.
• Pain and voiding symptoms: tamsulosin 400 micrograms once daily after a meal, ibuprofen 400 mg every 8 hours for up to 2 weeks, and pelvic floor physiotherapy.
• Procedures for obstructing, symptomatic or infected calculi that resist treatment:
  • Transurethral resection or laser enucleation of the prostate, with removal of the calculi, which also treats obstruction.
  • Holmium laser fragmentation of urethral and ductal calculi.
  • Open or laparoscopic removal is rarely needed.
• Perioperative cefazolin 2 g intravenously (3 g if over 120 kg) as a single dose.
• Treat the cause: urethral stricture and bladder outlet obstruction.

Monitoring. Symptom review and urine culture at 4 weeks and 3 months after treatment. PSA at 6 to 8 weeks when it was raised. Recurrence of calculi after resection is uncommon.

Referral and escalation. Refer to urology for recurrent infection, large or obstructing calculi, persistent pain or abnormal PSA. Urgent referral for retention, sepsis or abscess.