Nocturnal polyuria: Use these tools to make Dx

Nocturnal polyuria can't be diagnosed using a standard history alone, researchers say.

"You should do a 24-hour voiding diary in addition to medication history and examination in order to diagnose polyuria," Jeffrey P. Weiss, MD, of State University (SUNY) Downstate in Brooklyn, NY, told Urology Times.The study was presented by Harjot Singh of SUNY Downstate at the AUA annual meeting in San Francisco.

Nocturnal polyuria as a cause of nocturia may affect a person's quality of life and lead to increased falls and even death. The International Continence Society defines nocturnal polyuria as urine volume in excess of 33% of 24-hour urine volume in people over 65 years of age. Alternatively, Bosch et al have proposed defining nocturnal polyuria as more than 90 mL/hr of urine production without reference to 24-hour output.

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To measure the importance of previously identified risk factors for nocturnal polyuria, Dr. Weiss, Singh, and their colleagues retrospectively analyzed data on 524 patients who had completed a 24-hour flow volume chart during an evaluation of lower urinary tract symptoms.

They extracted data on past medical history, surgical history, and eight groups of medications: alpha-blockers, diuretics, angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, muscarinic antagonists, beta blockers, 5-alpha-reductase inhibitors, and phosphodiesterase-type-5 inhibitors.

They measured rates of overactive bladder, BPH, urethral stricture, urinary incontinence, hypertension, hypothryroidism, diabetes, urethral obstruction, prostate cancer, pedal edema, neurogenic bladder, Parkinson's disease, and sleep apnea.

In this population, some risk factors were overrepresented compared to the general population, including OAB and BPH, while others were underrepresented, including urinary incontinence, urethral obstruction, prostate cancer, and hypertension.

They divided the patients into two groups: 145 (96 male and 49 female) with nocturnal polyuria, defined as greater than 0.33 on the Nocturnal Polyuria Index, and 379 (242 male and 137 female) with normal urine production, defined as less than 0.33.

The authors found no statistically significant differences in risk factors between the two groups. They were particularly surprised to find that established risk factors such as sleep apnea and pedal edema did not correlate to nocturnal polyuria, they said. They speculated that this was due to the small sample size.

Continue to the next page for more data.They also found no statistically significant differences in medication use between the two groups, except for alpha-blockers. Forty-three percent of those with nocturnal polyuria were using these medications, compared to 57% of those without nocturnal polyuria (p=.041).

Of the other classes of medications, diuretics came closest to a statistically significant difference, with 51% used by those with nocturnal polyuria compared to 49% of those without the condition (p=.065).

Using binomial logistic regression to see which other factors might be independently associated with nocturnal polyuria, the authors found three that were statistically significant:

• The mean age of the people with nocturnal polyuria was 71.5 years, while the mean age of those without was 60.2 years (p=.01).
• The mean number of 24-hour voids was 11.8 for those with nocturnal polyuria, and 10.6 for those without (p=.003).
• The mean number of nocturnal voids was 3.5 for those with nocturnal polyuria, and 1.34 for those without (p=.001).

On the other hand, the maximum voided volume was 325 mL for those with nocturnal polyuria and 316 mL for those without, a difference that was not statistically significant (p=.561)

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Likewise, the 24-hour voided volume was 1,872 mL for those with nocturnal polyuria and 1,738 mL for those without, another difference that was not significant (p=.554).

The authors called for larger studies with more representative study populations. In the meantime, their findings underscored the importance of a 24-hour frequency volume chart as the gold standard for diagnosing nocturnal polyuria, Dr. Weiss said.

"Voiding diaries are good medicine, and as far as I know, nobody ever died of doing a voiding diary," said Dr. Weiss. "Why don't doctors tell their patients to do diaries more often? Because it's time consuming for the doctor and patient. It takes time to explain how to do the voiding diaries."

But the effort is worthwhile, because it can help distinguish patients with polyuria from those with nocturnal polyuria, he said. That's important because polyuria can be an indication of serious underlying conditions, such as untreated diabetes mellitus, he pointed out.