Diagnosis of enlarged prostate

Diagnosis of BPH is made based on medical history, physical examination and some confirmatory special tests.

Symptoms of BPH can be grouped as either obstructive or irritative (see symptoms). Diagnosis cannot be made on symptoms alone as many diseases can mimic the symptoms of BPH. A careful history will give clues to conditions other than BPH as the cause of symptoms.

Diseases that can mimic BPH:

  • Urethral stricture (narrowing of the tube of the penis)

  • Bladder cancer

  • Bladder infection

  • Bladder stones

  • Prostatitis (chronic infection in the prostate gland)

  • Neurogenic bladder (abnormal bladder function due to a neurological abnormality such as a stroke, Parkinson’s disease or multiple sclerosis)

  • Diabetes mellitus

Urethral stricture can result from previous trauma, instrumentation (i.e. catheter) or infection such as gonorrhoea. Blood in the urine may indicate bladder cancer. Burning and pain with passing urine may indicate infection or stones.

Diabetes can cause frequent passage of urine, as well as poor bladder emptying due to its effect on bladder muscle and nerve function.

Symptom scores are checklists used to assess the severity of prostatic symptoms and can help to determine if an individual needs further evaluation or treatment. The most widely used is the American Urological Association symptom index.

Symptoms are classified according to the total score as mild (1-7), moderate (8-19) or severe (20-35). Generally, no treatment is needed if symptoms are mild. Moderate symptoms usually require some form of treatment and severe symptoms most often lead to surgical treatment.

Physical examination:
On physical examination the doctor will assess the patient's general health and examine the abdomen for the presence of a full bladder. A digital rectal examination will be performed to assess the size, shape and consistency of the prostate gland.

This examination involves the insertion of a gloved finger into the rectum. The prostate gland is situated immediately adjacent to the anterior rectal wall and is easily palpable in this manner. The test is mildly uncomfortable, but should not be painful. BPH classically leads to smooth, rubbery enlargement, whereas prostate cancer causes hard irregular nodular enlargement of the prostate.

Unfortunately prostate size alone correlates poorly with symptoms or obstruction. Many large prostates cause no symptoms or obstruction at all, and some very small prostates can lead to severe obstruction with symptoms and/or complications.

An enlarged prostate per se is not an indication for treatment. In patients who do need treatment, the size of the gland can influence which treatment option is selected. A neurological examination is indicated if the history suggests a possible neurological cause for the symptoms.

Special tests:

Special tests are used to confirm diagnosis, rule out other causes of symptoms, prove or disprove obstruction and identify complications related to the obstruction.

Minimum recommended evaluation for BPH:

  • Medical history including symptoms index (see above)

  • Physical examination, including digital rectal examination (see above)

  • Urine analysis

  • Urine flow rate

  • Assessment of renal function (serum creatinine)

Optional tests:

  • Pressure/flow urodynamic testing

  • Serum PSA (prostate specific antigen)

  • Abdominal ultrasound of kidneys, ureter and bladder

  • Transrectal ultrasound of prostate gland

Simple urine analysis can be performed in the office with dipstix. If this indicates possible infection a urine culture should be obtained. If the urine contains blood this should be further investigated to rule out other causes.

A urine flow rate is performed by asking the patient to pass urine into a machine, which measures urine flow rate. Most machines measure the volume of urine, the maximum flow rate and the time taken to empty the bladder. For a flow rate test to be of value the patient needs to pass at least 125-150 ml of urine at one time.

The most useful parameter is the maximum flow rate or Q-max, measured in millilitres per second. Although flow is only an indirect measure of obstruction, most patients with a flow rate less than 10 ml/second will prove to have bladder outflow obstruction, whereas most patients with a flow rate of more than 15 ml/second will not have evidence of obstruction.

Patients with a low flow rate prior to surgery tend to do better following surgery as compared to those with higher initial flow rates. A low flow rate however cannot be used to distinguish between obstruction and poor bladder muscle function as the cause of poor flow.

Serum creatinine is measured on a blood sample and is a fair reflection of renal function. Creatinine is one of the waste products excreted by the kidneys. If serum creatinine level is elevated due to bladder outflow obstruction, it is prudent to drain the bladder with a catheter and allow the kidneys to recover prior to embarking on prostate surgery.

Pressure/flow urodynamic testing is the most accurate method of proving obstruction of the bladder outlet. It involves simultaneous measurement of pressure within the bladder and flow of urine. Obstruction is characterised by high pressure and low flow. It is an invasive test with probes inserted into the bladder and rectum. Most authors do not recommend routine measurement of pressure/flow urodynamics for patients with prostate symptoms. It can however be invaluable in cases that are not clear-cut.

Indicators for pressure flow analysis:

  • Any neurological abnormality, e.g. stroke, Parkinson’s disease and multiple sclerosis

  • Severe symptoms with a normal flow rate (>15ml/s)

  • Longstanding Diabetes mellitus

  • Previous failed prostate surgery

Serum PSA is elevated by BPH, but more so by prostate cancer. The routine use of serum PSA as a screening test for prostate cancer is controversial. The American Urological Association and most urologists recommend annual PSA testing in men over 50 years with a 10-year life expectancy.

Black men and men with a positive family history of prostate cancer should start PSA testing at age 40. PSA levels rise before prostate cancer becomes clinically evident, enabling early diagnosis and treatment while the disease is still curable.

Abdominal ultrasound can be useful to assess the kidneys for hydronephrosis (swelling and dilatation) and to measure the post void residual, that volume which remains in the bladder after the patient has passed urine. Residual urine volume does not correlate well with other symptoms and signs of prostatism and does not predict the outcome of surgery.

It is uncertain whether large post void residual volumes indicate impending bladder or renal damage. Most authors feel that patients with large post void residual volumes should be monitored more closely if they opt for non-surgical therapy.

Kidney impairment due to obstruction is associated with dilatation (hydronephrosis). In patients with raised serum creatinine, ultrasound can confirm whether the kidney impairment is due to obstruction or not.

Transrectal ultrasound of the prostate gland is not routinely indicated in patients with BPH. It can measure prostate volume (size) very accurately. Its main role is in guiding prostate biopsies in cases of suspected prostate cancer.

Read more:
How healthy is your prostate?
Sex Zone

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