Diagnosing Nocturnal Polyuria from a Single Nocturnal Urine Sample.

Patients with nocturnal polyuria (NP) experience a unique surge in nocturnal diuresis rate during the early hours of sleep.

To determine the diagnostic utility of the volume and osmolality of a single early nocturnal urine sample in detecting NP.

Analysis of 1 am urine samples obtained from two prospective observational studies at Ghent University Hospital involving participants recruited from a urology ambulatory care unit and those who consulted a continence clinic. Nocturic participants (one or more nocturnal void[s]; n=176) were stratified based on the presence (n=87) or absence (n=89) of NP (>90ml/h).

Receiver operating characteristic curves with Youden's Index were used to determine cutoff values for urine volume and urine osmolality (Uosm).

Individuals with NP demonstrated higher 1 am volume (400 [interquartile range 300-515] vs 210 [160-300] ml, area under the curve [AUC]=0.843, p< 0.001, cutoff = 350 ml) and lower Uosm (274 [201-348] vs 430 [320-664] mOsm/kg H2O, AUC=0.774, p<0.001, cutoff=314 mOsm/kg H2O) than those without NP. In combining cutoffs, the criteria of either 1 am volume ≥350ml or Uosm ≤314 mOsm/kg H2O were 85% sensitive and 75% specific for NP, while criteria of both 1 am volume ≥350ml and Uosm ≤314 mOsm/kg H2O were 60% sensitive and 92% specific for NP. Comparable AUC values, sensitivities, and specificities were observed in both men and women. Limitations include post hoc design and a relatively small study sample.

Individuals with NP are more likely than those without NP to produce a higher volume of more dilute urine (ie, "aquaresis") in the early hours of sleep. Analysis of easily measurable parameters of the first nocturnal void (for which 1 am values serve as a surrogate) in men and women with nocturia can predict a diagnosis of NP with a reasonably high degree of sensitivity and specificity.

Urologists often try to understand the specific reason why people wake up to urinate at night by asking them to record the amount of urine they make every time they go to the bathroom (also known as a "voiding diary") during the nighttime as well as the daytime-typically for a total of 1-3 days. In this study, we showed that an analysis of the composition of the urine that people produce when they first wake up to urinate at night might be sufficient to determine whether their symptoms are caused by excessive urine production or something else, and some people might find this urine study easier than keeping a voiding diary.

European urology focus. 2019 Oct 16 [Epub ahead of print]

Thomas F Monaghan, Joseph G Verbalis, Rebecca Haddad, Kim Pauwaert, Christina W Agudelo, An-Sofie Goessaert, Marie-Astrid Denys, Jason M Lazar, Donald L Bliwise, Johan Vande Walle, Alan J Wein, Jeffrey P Weiss, Karel Everaert

Department of Urology, State University of New York Downstate Health Sciences University, Brooklyn, NY, USA. Electronic address: ., Division of Endocrinology and Metabolism, Department of Medicine, Georgetown University Medical Center, Washington, DC, USA., Department of Urology, Ghent University Hospital, Ghent, Belgium; Sorbonne Université, UPMC Univ Paris 06, AP-HP, GRC 01, Groupe de Recherche Clinique en Neuro-Urologie (GREEN), Service de Rééducation Neurologique, AP-HP, Hôpitaux Universitaires Est Parisien, Paris, France., Department of Urology, Ghent University Hospital, Ghent, Belgium., Department of Urology, State University of New York Downstate Health Sciences University, Brooklyn, NY, USA., Division of Cardiovascular Medicine, Department of Medicine, SUNY Downstate Health Sciences University, Brooklyn, NY, USA., Department of Neurology, Emory University School of Medicine, Atlanta, GA, USA., Department of Pediatric Nephrology, Ghent University Hospital, Ghent, Belgium., Department of Urology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.