Overactive Bladder Patients With and Without Urgency Incontinence: A Spectrum of One Condition or Different Phenotypes?
Authors: Torosis Michele , Jackson Nicholas , Nitti Victor , Ackerman A. Lenore 
Published: April 2023

ABSTRACT
The International Continence Society classifies overactive bladder (OAB) as a storage symptom syndrome characterized by “urgency, with or without urgency urinary incontinence, usually with increased daytime frequency and nocturia.” Although heterogenous in nature, some OAB patients exhibit only frequency and urgency (“OAB-dry”), whereas others exhibit frequency and urgency with urgency incontinence (“OAB-wet”). This study aimed to further explore the unique features of each of these diagnoses via comparison of data for women seeking lower urinary tract symptom (LUTS) care, including data such as physical examination findings, self-reported symptoms, and demographic data. Better understanding of OAB-wet and OAB-dry definitive features may lead to more effective treatment.
Through the LURN (Lower Urinary Tract Dysfunction Research Network)—sponsored via the research network NIDDK (National Institute of Diabetes and Digestive and Kidney Diseases)—physical examination, demographic data, and questionnaire data were obtained for women seeking LUTS-based care at 6 centers in the United States. Enrollment entailed categorization of patients into urinary incontinence subtypes, as determined by LURN clinical staff from patient LUTS Tool responses. Subgroups included both OAB-dry and OAB-wet categories, as well as a control LUTS group lacking symptoms.
The multicenter data set found 545 LUTS-presenting women, with 84 patients being defined as OAB-wet, 56 patients defined as OAB-dry, and 67 patients defined as the control population. The study population was predominantly White (83%), with mean age of the cohort as 58.8 ± 14.1 years. Demographics did not vary between the categories. The groups experienced very similar symptoms, except OAB-wet patients had urgency incontinence, and OAB-dry reported significantly more bladder pain, incomplete emptying, and straining to urinate.
Both OAB groups exhibited identical levels of frequency, nocturnal, urgency, and level of bother. Both OAB groups experienced more bother than controls. However, bother for OAB-wet was directly related to severity of incontinence, and bother for OAB-dry was directly related to pelvic floor tenderness on examination. These results may indicate that the individual conditions hail from divergent etiologies, which contradicts traditional disease concepts.
Since OAB-dry patients commonly report sensations of incomplete emptying, bladder pain, and straining to urinate, the authors hypothesized that these symptoms may represent a pelvic floor muscle dysfunction rather than a true bladder pathology. This hypothesis is based on the significant overlap between bladder symptoms of OAB-dry and bladder symptoms in high-tone pelvic floor dysfunction (HTPFD) patients (or those with myofascial pelvic pain). Possible causes were this to be the case might be changes in muscle function leading to alterations in the resting angle of the urethrovesical junction and irritation of the bladder neck or urethra. In addition, neuromuscular dysfunction may lead to symptoms of HTPFD and OAB.
Strengths of this study include its large study parameters involving multiple centers across the nation, including all patients seeking care for LUTS. Because most women in the study were White, generalizability of the study to a more diverse patient population is limited. In addition, patient self-reporting of incontinence type lacked simultaneous objective testing. Moreover, significant pelvic pain excluded patients from this cohort, which may have excluded patients with more severe forms of OAB-dry from the study population.
Although traditionally grouped and treated together under a larger OAB diagnosis, OAB-wet and OAB-dry have unique symptomatic features, suggesting divergent etiologies. Unique symptoms such as pain, a feeling of incomplete emptying, and straining with urination all suggest pelvic floor myofascial dysfunction for OAB-dry patients. Further examination of a distinct pathophysiology for these 2 groups is warranted.