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Diagnostic investigations in urology

Last updated: February 24, 2021

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Patients with urological symptoms are diagnosed based on clinical features and routine diagnostics. Urodynamic tests help to evaluate functional and anatomical abnormalities of the lower urinary tract. The most common tests are cystometry, uroflowmetry, urethral pressure profile, and leak point pressure. Imaging may be used in combination to diagnose underlying pathologies and is often used to assess for anatomical obstructions or abnormalities (e.g., urinary obstructions caused by kidney stones, renal masses).

For more on renal function tests, urinalysis, urine dipstick, and renal biopsy, see diagnostic evaluation of the kidney and urinary tract.
For more on urine culture, see “Laboratory tests” under diagnostics in urinary tract infections.

Urodynamic studies use the characteristics of urinary flow (pressure and flow rate at various points during micturition and at rest) to evaluate the functional and anatomical abnormalities of the lower urinary tract.

Cystometry

  • Description
    • Assesses bladder pressure during filling
    • Determines detrusor and bladder function (activity, sensation, capacity, and compliance)
    • The bladder is filled with water through a urethral catheter at a steady rate → the vesical pressure is measured through this urethral catheter, while the intraabdominal pressure is measured via a vaginal or rectal pressure catheter → detrusor pressure = the difference in pressure between these two catheters
  • Indications

Uroflowmetry

  • Description
    • Measures the volume of urine voided over time
    • The patient is asked to void into a funnel that measures the volume and rate of urine flow.
      • Normal: a continuous, single bell-shaped curve with urine volume > 200 mL (over 15–30 seconds) and at a rate > 15 mL/sec
      • Abnormal: an abnormal curve or urine volume at a rate < 15 mL/sec (a urine volume < 150 mL increases the risk of an inaccurate assessment)
  • Indications

Pressure-flow study

Urethral pressure profile

  • Description
    • Assesses intrinsic sphincter function
    • Measures the intraluminal urethral integrity at different pressures (filling and voiding pressures are measured under different types of provocation, e.g., Valsalva maneuver, coughing, etc.)
    • A specialized urethral catheter, mounted with microtransducers, is withdrawn at a slow and steady rate from the bladder until it exits the external urethral meatus.
  • Indications

Leak point pressure

Postvoid residual volume

Electromyelogram (EMG)

  • May be performed during cystometry
  • Studies the electrical potentials of depolarized muscle, specifically the neural pathways involved in micturition (by evaluating the segment of the sacral spinal cord involved)
  • Electrodes or a concentric needle are inserted into the urethral sphincter.
  • Indication: to determine neurological abnormalities of the bladder (e.g., hypotonic bladder)

References:[1][2][3][4][5][6][6]

Ultrasound

The bladder should be full to visualize pelvic structures!

CT

  • Indications

MRI

Renal scintigraphy (also known as renal radionuclide scan, radioisotope renography)

  • Description
    • IV administration of technetium (Tc-99m pertechnetate/gamma emitter) and measurement of its distribution in the body with a gamma camera
    • Static renal scintigraphy
      • Procedure
        • Tc-99m DMSA is injected.
        • Imaging is performed ∼ 3 hours after injection, when the dye has reached the kidneys for renal clearance.
      • Helps visualize the renal morphology (position, form, size, anomalies)
    • Dynamic renal scintigraphy (MAG3 renal scan)
  • Indications

Voiding cystourethrogram

Intravenous urography (excretory urogram, IV urography)

CT urography

  • Description: a CT with contrast dye injected inravenously to assess the anatomy and, to a certain degree, function of the urinary collecting system, renal calyces, ureters, and bladder.
  • Indications: a first-line imaging test to assess for genitourinary abnormalities (e.g., malignancy, stricture)

Retrograde urethrogram

Retrograde CT cystography

References:[1][8][9][10][11][12]

References:[13]

  1. Hanson KA. Diagnostic Tests and Tools in the Evaluation of Urologic Disease: Part II. Urol Nurs. 2003; 23 (6).
  2. Whitfield HN. Urological evaluation. BMJ. 2006; 333 (7565): p.432–435. doi: 10.1136/bmj.333.7565.432 . | Open in Read by QxMD
  3. DeRidder PA, Dauben RD. Electromyelography, a useful test for evaluation of the sacral spinal cord. J Urol. 1981; 125 (6): p.835-838.
  4. Chernecky CC, Berger BJ. Laboratory Tests and Diagnostic Procedures. Elsevier Health Sciences ; 2012
  5. Nitti VW. Pressure flow urodynamic studies: The gold standard for diagnosing bladder outlet obstruction. Rev Urol. 2005; 7 (Suppl 6): p.S14-S21.
  6. Chapple CR, MacDiarmid SA, Patel A. Urodynamics Made Easy. Elsevier Health Sciences ; 2012
  7. Reynard J, Brewster S, Biers S. Oxford Handbook of Urology. OUP Oxford ; 2013
  8. Dunnick R, Sandler C, Newhouse J. Textbook of Uroradiology. Lippincott Williams & Wilkins ; 2012
  9. Voiding cystourethrography. https://radiopaedia.org/articles/voiding-cystourethrography-1. Updated: January 16, 2017. Accessed: January 16, 2017.
  10. Warrell DA, Cox TM, Firth JD. Oxford Textbook of Medicine. Oxford University Press ; 2015
  11. Adam A, Dixon AK, Gillard JH, Schaefer-Prokop C, Grainger RG, Allison DJ. Grainger & Allison's Diagnostic Radiology E-Book. Elsevier Health Sciences ; 2014
  12. Intravenous Urography. https://radiopaedia.org/articles/intravenous-urography. Updated: January 1, 2017. Accessed: November 19, 2017.
  13. Urethrography. https://radiopaedia.org/articles/urethrography. Updated: January 1, 2017. Accessed: November 19, 2017.
  14. Urologie Online Lehrbuch. http://www.urologielehrbuch.de. . Accessed: January 1, 2012.