A prostate ultrasound is the most common way of imaging the prostate gland in detail. Most prostate ultrasounds are transrectal — the probe is inserted a short distance into the rectum, where it sits right next to the prostate and produces high-quality images. A simpler approach using a probe on the lower abdomen with a full bladder (transabdominal ultrasound) is sometimes used to estimate prostate size but cannot show internal detail.
This guide focuses on transrectal ultrasound (TRUS), which is the standard prostate examination.
Common Indications for a Prostate Ultrasound
Your doctor may request a TRUS if:
- You have urinary symptoms — slow stream, hesitancy, dribbling, incomplete emptying, or waking at night to pass urine.
- Your PSA (prostate-specific antigen) blood test is elevated.
- Your doctor felt an abnormality on a digital rectal examination.
- A prostate biopsy is needed, and the biopsy needles will be guided by ultrasound.
- Prostate cancer is known and the doctor needs to assess the volume of the prostate before treatment.
- You are being evaluated for infertility and seminal vesicle problems are suspected.
What exactly does TRUS show?
The scan shows:
- The size and shape of the prostate gland.
- The internal zones of the prostate (peripheral, central, transition zones).
- The seminal vesicles behind the prostate.
- The bladder neck and the area where the urethra exits the prostate.
- Any visible nodules, cysts, calcifications, or focal abnormalities.
TRUS is a good test for size and structure. For detecting cancer specifically, MRI is more sensitive — but TRUS remains essential for guiding biopsies and is often combined with MRI findings.
What happens during the procedure?
- You change into a gown and remove your underwear.
- You lie on your side on the exam table, knees drawn up toward your chest.
- The radiologist or sonographer covers the probe with a thin sheath and lubricating gel.
- The probe (about the diameter of a finger) is gently inserted into the rectum and rotated to get views from multiple angles.
- If a biopsy is planned, a numbing injection (local anaesthetic) is given through the probe, and small tissue samples are taken with a thin needle.
The scan itself takes about 10 to 15 minutes. With a biopsy, the total appointment can take 30 to 45 minutes.
Do I need to prepare?
For ultrasound alone (no biopsy):
- No fasting is required.
- Empty your bladder before the scan unless otherwise instructed.
- Wear comfortable clothing — you will change into a gown.
For TRUS with biopsy:
- You may be asked to take a small enema 1 to 2 hours before to clear the rectum.
- You will likely be given antibiotics before and after the biopsy to reduce infection risk.
- Stop blood-thinning medications a few days before, only on your doctor's instruction — never stop them on your own.
- Arrange for someone to drive you home; you may feel sore.
Will the test be painful?
The ultrasound itself is uncomfortable rather than painful. The probe is firm and inserting it can feel strange, but it should not hurt. Tell the radiologist immediately if it does.
If a biopsy is included, the local anaesthetic significantly reduces pain. Most patients describe the biopsy as feeling like a sharp tap or a small pinch, repeated 8 to 12 times. The whole biopsy lasts a few minutes.
How long do the results take?
For an ultrasound alone, the report usually reaches your doctor within 24 to 72 hours.
For a biopsy, the tissue samples are sent to a pathologist. Pathology results typically take 5 to 10 working days in Nigerian centres.
Are there risks?
For ultrasound alone, the risks are minimal — slight discomfort and a small chance of minor bleeding from the rectum.
For TRUS-guided biopsy, the risks include:
- Blood in the urine, semen, or stool — common, usually mild, and self-limiting. Blood in semen can persist for several weeks.
- Urinary tract infection or prostatitis — uncommon if antibiotics are given, but call your doctor immediately if you develop fever, chills, or worsening pain.
- Difficulty passing urine — temporary, usually resolves within a day or two.
- Sepsis — rare but serious; this is why prophylactic antibiotics are standard.
When to seek urgent help after a biopsy
Call your doctor or go to the nearest emergency department immediately if you develop fever, chills, severe pain, persistent heavy bleeding, or inability to pass urine after a prostate biopsy. These can signal infection or bleeding that needs prompt treatment.
What about transperineal biopsy and MRI-guided approaches?
Some centres now offer transperineal biopsy (through the skin between the scrotum and anus) instead of through the rectum. This route has lower infection rates and is becoming more popular. MRI-fusion biopsy combines pre-biopsy MRI with real-time ultrasound to target suspicious areas more precisely. Ask your urologist which approach is available and appropriate for you.
Is the ultrasound itself safe?
Yes. The ultrasound waves used are the same as any diagnostic ultrasound — no radiation, no contrast, no medications during the scan itself. The biopsy carries the risks described above, but the imaging is risk-free.
What are the important limitations?
Ultrasound does not use ionising radiation, but a useful result still depends on the clinical question, the operator, the equipment, patient anatomy, and whether the target can be reached by sound waves. Gas, bone, body habitus, pain, movement, and a limited acoustic window can hide disease. A normal scan does not automatically exclude the suspected condition; persistent or worsening symptoms need clinical reassessment and sometimes repeat ultrasound, CT, MRI, laboratory tests, or another specialist test.
Ultrasound should be used for a medical purpose, with output and examination time kept as low as reasonably achievable—especially in pregnancy and with Doppler. Internal scans and procedures require explanation, consent, privacy, and a chaperone according to patient preference and local policy.
Sources and further reading
Conclusion
A transrectal prostate ultrasound is the standard imaging test for the prostate, used to size the gland, investigate urinary symptoms, and guide biopsies. It is brief, uses no radiation, and combined with PSA and digital rectal examination, it is the cornerstone of prostate evaluation. For prostate cancer detection specifically, MRI now plays a complementary role — but TRUS remains essential for tissue sampling.