Urinary Dysfunction Common Among Younger Patients

Patricia Inácio, PhD avatar

by Patricia Inácio, PhD |

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Bladder problems leading to urinary incontinence and other manifestations are common among children, adolescents and young adults with Prader-Willi syndrome (PWS), a study shows.

The study, “High prevalence of lower urinary tract dysfunction in patients with Prader–Willi syndrome,” was published in the journal Neurourology and Urodynamics.

PWS is caused by loss of, or defects in, paternal genes on chromosome 15 that control metabolism, appetite, growth, intellectual skills, and social behavior.

In school-age children, research has shown that the most frequent symptoms of lower urinary tract dysfunction (LUTD) are urinary incontinence, holding maneuvers (physical distractions to avoid urinating), and urinary urgency (a sudden urge to urinate).

A previous study based on questionnaires to parents reported that 13.6% of PWS patients presented nocturnal enuresis (bed-wetting) and 3.8% daily urinary incontinence. However, studies using objective tools to assess LUTD in patients with PWS are still lacking.

Here, researchers in Taiwan evaluated the incidence of symptoms of LUTD among children, adolescents, and young adults with PWS using non-invasive tools, including uroflowmetry and post-void residual urine (PVR).

The uroflowmetry test is a simple procedure to measure the flow of urine over time. The person taking the test has to urinate into a special funnel connected to a measuring instrument that records the flow and total volume of urine. Results are translated into a graph that can indicate whether there are bladder issues.

The PVR measures the amount of urine retained in the bladder after a voluntary void (emptying the bladder).

In total, the study included 37 patients with PWS (mean age 17.7 years, 15 males and 22 females). Among those with known cause of PWS, 16 patients (43.2%) had a deletion of paternal genes, while three (8.1%) had uniparental disomy — inheriting both copies of chromosome 15 from the mother rather than one from each biological parent.

The mean body mass index (a measure of body fat) was 28.5 kg per square meters, which is in the overweight range. Eight patients had diabetes and were given insulin or oral hypoglycemic agents, used to manage blood sugar levels.

Most patients had intellectual disability, with a mean IQ of 51.9.

A total of 34 participants completed the uroflowmetry examination. An abnormal pattern was detected in 13 patients — six patients showed an obstruction, three with a staccato (indicative of overactive sphincter, which controls the flow of urine through the urethra), two patients had an intermittent pattern, and one had a “tower pattern,” indicative of hyperactive bladder. For the remaining 22 patients a normal bell curve pattern was observed.

Almost 30% (10 patients) had a low peak flow rate below 15 milliliters per second (ml/s), which is indicative of LUTD in people ages 7 and older.

PVR was measured in 20 patients. Half had elevated PVR value for their age.

Combining the results of both tests, uroflowmetry and PVP, revealed that 17 PWS patients (50%) had at least one urinary abnormality.

The researchers then divided the group into patients with and without LUTD symptoms. These included frequency, urgency, straining, urinary incontinence, nocturnal enuresis, and difficulty voiding. Urinary incontinence affected seven patients (18.9%).

Symptomatic patients had significantly lower peak flow rate (14.4 ml/s vs. 24.0 ml/s) and bladder capacity (143.5 ml vs. 247.7 ml) than those without symptoms.

In particular, bladder capacity was significantly lower among PWS patients with LUTD symptoms than among those without, 36.1% vs. 56.9%.

The scientists then conducted a video urodynamic test in three patients. With this exam, they record images and analyze the pressure and flow in the urinary tract.

Results showed that all three patients had detrusor sphincter dyssynergia, meaning bladder dysfunction due to a neurologic abnormality. They showed occasional urgency and urge incontinence, and two also had constipation.

Overall, the findings suggest that “low urinary tract dysfunction was common in PWS patients with or without [LUTD symptoms],” the researchers wrote.

Non-invasive tests are “recommended in all PWS patients and invasive study in selected cases with repeat abnormal uroflowmetry curves and elevated PVR,” they concluded.

Among the study limitations, the team mentioned the low compliance with PVR, difficulty having certain patients do a second uroflowmetry, and the wide age range (5 to 34 years) of the participants.