Diagnostic tests in Urology

Laboratory tests and urinalysis

It can provide information about:

• red blood cells;
• white blood cells;
• bacteria;
• protein;
• glucose;
• pH;
• crystals.

It identifies microorganisms and determines their antibiotic susceptibility.

It must be interpreted together with symptoms and the clinical context.

Creatinine and estimated glomerular filtration rate allow assessment of renal function.

Prostate-specific antigen is a marker produced by prostate tissue.

It is not a cancer-specific marker.

It can change in different situations and must always be interpreted in the clinical context.

Ultrasound

It is one of the most widely used tests in Urology because:

• it does not use ionizing radiation;
• it is accessible;
• it allows evaluation of the kidneys and bladder;
• it can assess the prostate;
• it detects urinary tract dilation;
• it allows measurement of postvoid residual;
• it can identify certain masses, stones, and cysts.

It is especially useful for evaluating:

• testicular masses;
• hydrocele;
• epididymis;
• trauma;
• scrotal pain.

Doppler provides information about vascularization.

Uro-CT / Computed tomography

CT allows the urinary tract to be studied in great detail.

Depending on the protocol, it can be used to evaluate:

• stone disease;
• hematuria;
• renal masses;
• trauma;
• obstruction;
• urinary tract tumors.

Non-contrast CT is very useful for detecting urinary stones.

When contrast and specific phases are used, the following can be studied:

• renal parenchyma;
• collecting system;
• ureters;
• bladder.

Magnetic resonance imaging

MRI offers excellent soft-tissue characterization and avoids ionizing radiation.

It has important applications in:

• prostate cancer;
• characterization of certain renal lesions;
• vascular assessment;
• staging of some tumors;
• situations where CT does not provide sufficient information or is contraindicated.

Multiparametric prostate MRI currently plays a central role in the evaluation of patients with suspected prostate cancer.

Functional studies

Unlike anatomical studies, they try to determine how the urinary tract works.

It records urinary flow during voiding.

It shows:

• maximum flow rate;
• average flow rate;
• voided volume;
• curve shape.

A low flow indicates impaired emptying, but by itself it does not determine the cause.

It measures the amount of urine that remains in the bladder after voiding.

It can be done by ultrasound.

An elevated residual can result from:

• obstruction;
• decreased bladder contractility;
• a combination of both.

It studies the function of the bladder and urethra during storage and emptying.

It can analyze:

• sensation;
• capacity;
• pressures;
• compliance;
• involuntary contractions;
• pressure-flow relationship.

Not all patients need urodynamics.

Which test to choose?

A simple approach for the student:

Suspected infection → urinalysis ± urine culture.

Renal colic → ultrasound and/or CT depending on the clinical scenario.

Hematuria → risk-based evaluation, usually combining upper urinary tract imaging and, when appropriate, cystoscopy.

Renal mass → CT or MRI with an appropriate protocol.

Suspected prostate cancer → PSA + clinical evaluation → prostate MRI as indicated.

Voiding problem → uroflowmetry + postvoid residual as initial tools.

Complex functional problem → consider urodynamics.