Urodynamics

Urodynamics

What is urodynamics?

Urodynamics involves examining the functionality of the lower urinary tract, comprising the bladder and urethra, through physical measurements like urine pressure and flow rate, alongside clinical evaluation.

The evaluation commences with a medical history and examination, which may uncover lower abdominal or pelvic abnormalities contributing to urinary tract symptoms.

Subsequently, the patient maintains a urination diary for three days to record fluid intake, output, and incidents of incontinence.

The diary documents:

- Bladder capacity
- Urination frequency
- Incontinence episodes
- Nocturia (nighttime urination)

Additionally, a urine sample is sent to the laboratory to rule out infection.

For women experiencing urinary incontinence, a pad test may be conducted to quantify the severity. This involves wearing a pre-weighed pad while performing daily activities after drinking water. An increase in pad weight signifies urinary incontinence.

What diagnoses can be made from urodynamic studies?

Urine, produced by the kidneys, flows to the bladder via the ureters' rhythmic contractions. The bladder empties through the urethra upon contraction of the relaxed detrusor muscle lining its wall.

Detrusor muscle instability may lead to lower urinary tract symptoms like frequency, urgency, and nocturia. An unstable detrusor may contract between voids, causing high bladder pressures, urgency, and urine leakage.

In men, similar symptoms may result from prostate enlargement (BPH), and urodynamic studies help differentiate between the two causes.

For obstruction diagnosis, urodynamic pressure-flow studies remain the gold standard. Stress urinary incontinence (SUI) and urge incontinence are the two primary types of urinary incontinence, each demonstrated through urodynamic filling cystometry.

Filling cystometry involves measuring bladder pressure as it's filled with saline solution at a controlled rate. Compliance and stability of the detrusor muscle are assessed through a cystometrogram (CMG).

During CMG, vesical pressure, abdominal pressure, and detrusor pressure are monitored. Normal compliance allows the bladder to stretch to its capacity at low pressures. Stability is determined by observing detrusor activity during bladder filling.

Flow-pressure studies, conducted after CMG, assess urethral obstruction by measuring detrusor pressure at maximum flow. Videocystourethrography combines flow-pressure studies with X-ray screening for complex cases.

Who should undergo urodynamics?

Not all patients with urinary tract symptoms require comprehensive urodynamic assessments. However, these studies are crucial if prior treatments have failed or before surgical interventions for incontinence or bladder prolapse.