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Female Mixed Urinary Incontinence (MUI)


Editor: Kevin Rademakers, Maastricht University Medical Centre


Terminology and epidemiology

Mixed Urinary Incontinence is defined by the International Continence Society (ICS) as the complaint of involuntary leakage associated with urgency and also with physical exertion, effort sneezing or coughing (1, 2). About 30% of the women with incontinence have Mixed Urinary Incontinence (MUI), with the degree of bother in this group being higher than pure stress urinary incontinence (SUI) (3). In this perspective, this form of incontinence is important to crystallize in terms of diagnostic evaluation and treatment. Both of which have proven to be difficult for MUI.

Diagnostic evaluation

When discussing Mixed Urinary Incontinence evaluation detailed history taking is of upmost importance. Labor, neurologic disorder, pelvic floor trauma, surgery, voiding behavior (from earlier childhood on) and defecation pattern should be addressed. In 2013, Digesu et al. published a study in which the highlighted the importance of history taking. Determination of the first occurring and most bothersome symptom related closely to the urodynamic diagnosis. Therefore they drew attention to a symptom-guided approach to direct to optimal therapy (4, 5).
Stress urinary incontinence or stress leakage is assessed by the observation of involuntary leakage from the urethra, synchronous with exertion/effort, or sneezing or coughing preferable before or after cystoscopy. Overactive bladder (OAB) syndrome is assessed by detailed history taking and a bladder diary. A bladder diary is preferable above general Frequency-Volume Charts (FVC) adding also incontinence and sensation information.
In case there is still uncertainty about the underlying cause of incontinence and predominant factor (stress or urgency) causing the incontinence, urodynamics may be performed. Several indicators appear to be indicative for persisting urge after treatment, such as high pressure detrusor overactivity (6), lower urethral closing pressure, higher urethral opening pressure (7). Although some indicators for persisting symptoms have been explored, in general conventional urodynamic studies do not give sufficient additional information on the pathophysiological background. Therefore, ambulatory urodynamic studies (UDS) may be considered. The advantages of ambulatory UDS having a longer recording period, multiple micturition cycles, additional stress-testing, and the observation of urinary leakage combined with pressure-flow traces makes it more suitable for potential detection of the predominant cause of the urinary incontinence (8).
Robinson et al. assessed whether ultrasound bladder wall thickness measurement could replace ambulatory urodynamics in 128 patients women with a conventional urodynamic diagnosis not explaining their urinary symptoms. The authors concluded that in women with stress incontinence ambulatory urodynamics remains the investigation of choice (9).
There is currently only limited literature on the specific role of ambulatory UDS in identification of the origin of incontinence with attention to detrusor overactivity (DO) as well as the stress component. However, the available literature suggests that ambulatory UDS improves the ability to detect an underlying pathophysiology compared to conventional urodynamics (10).

Therapy

Conservative treatment for MUI in general consists of pelvic floor strength training (11) to reduce the stress incontinence component, together with a anticholinergic drug or beta-3 agonist to reduce urgency. In case of failure of conservative treatment, more invasive options should be discussed intensively with the patient, i.e. primary treatment of stress or urgency component. In addition, lifestyle advice should be given to the patient (fluid restriction, timed voiding, bladder training and weight loss).
Determination of the first occurring and most bothersome symptom in women with MUI should form the starting point for the treatment of choice. In 1998 Scotti et al. published a series of 58 women with MUI and concluded that patients with stress incontinence as primary symptom and later develop urge incontinence are 2.5 times likely to be cured of urge incontinence by Burch colposuspension, compared to those with urge incontinence as primary presenting symptom (12). Kulseng-Hanssen confirmed these results in a large series of women treated with TransVaginal Tape (TVT) (13). In general, about 50-60 percent of the women treated for the stress component the urge component improves.
In patients with predominant urge incontinence sacral neuromodulation should be considered as treatment option. However, until now there in only very limited evidence on this treatment modality in relation to MUI.

Perspectives and controversies

- The term Mixed Urinary Incontinence implicates an equal presence of stress- and urge incontinence in every MUI patient. However, in daily practice patients most commonly present themselves with predominant stress (with the urge component on the background), or predominant urge with a stress component on the background. Looking at applicability of the term and implications for further treatment it seems better to define MUI with the predominant component (stress predominant MUI / urge predominant MUI).
- There still remains much controversy on the pathophysiological basis of MUI. Do patients have 2 separate phenomena (urge- and stress urinary incontinence); one affecting the bladder and causing urge incontinence, and the other secondary to intrinsic urethral dysfunction causing stress incontinence, or can MUI be explained by one pathophysiologic process (14).
- In terms of diagnostic evaluation further analysis of novel diagnostic tests to differentiate predominant cause of incontinence in cases of MUI should be explored. For example the use of Ambulatory Urodynamics and development of less invasive tests such as bladder wall thickness measurements
- With regard to treatment much focus has been put to treatment of the stress incontinence component in patients with MUI. However, there is only very limited evidence on treatment of the urge incontinence component with, for example, sacral neuromodulation or botulinum toxin injections. Therefore, exploring additional treatment options for women with MUI specifically focusing on the urgency component is of importance.

References
1. Abrams P, Cardozo L, Fall M, Griffiths D, Rosier P, Ulmsten U, et al. The standardisation of terminology of lower urinary tract function: report from the Standardisation Sub-committee of the International Continence Society. Neurourol Urodyn. 2002;21(2):167-78.
2. Haylen BT, Freeman RM, Swift SE, Cosson M, Davila GW, Deprest J, et al. An International Urogynecological Association (IUGA)/International Continence Society (ICS) joint terminology and classification of the complications related directly to the insertion of prostheses (meshes, implants, tapes) and grafts in female pelvic floor surgery. Neurourol Urodyn. 2011;30(1):2-12.
3. Dooley Y, Lowenstein L, Kenton K, FitzGerald M, Brubaker L. Mixed incontinence is more bothersome than pure incontinence subtypes. Int Urogynecol J Pelvic Floor Dysfunct. 2008;19(10):1359-62.
4. Digesu GA, Derpapas A, Hewett S, Tubaro A, Puccini F, Fernando R, et al. Does the onset or bother of mixed urinary incontinence symptoms help in the urodynamic diagnosis? Eur J Obstet Gynecol Reprod Biol. 2013;171(2):381-4.
5. Digesu GA, Salvatore S, Fernando R, Khullar V. Mixed urinary symptoms: what are the urodynamic findings? Neurourol Urodyn. 2008;27(5):372-5.
6. Schrepferman CG, Griebling TL, Nygaard IE, Kreder KJ. Resolution of urge symptoms following sling cystourethropexy. J Urol. 2000;164(5):1628-31.
7. Panayi DC, Duckett J, Digesu GA, Camarata M, Basu M, Khullar V. Pre-operative opening detrusor pressure is predictive of detrusor overactivity following TVT in patients with pre-operative mixed urinary incontinence. Neurourol Urodyn. 2009;28(1):82-5.
8. Rademakers K, Drossaerts JM, Rahnama'i MS, van Koeveringe GA. Differentiation of lower urinary tract dysfunctions: The role of ambulatory urodynamic monitoring. Int J Urol. 2015;22(5):503-7.
9. Robinson D AK, Cardozo L, Bidmaed J, Hobon P, Khullar V. Can ultrasound replace ambulatory urodynamics when investigating women with irritative urinary symptoms. BJOG. 2002;109(2):4.
10. Dokmeci F, Seval M, Gok H. Comparison of ambulatory versus conventional urodynamics in females with urinary incontinence. Neurourol Urodyn. 2010;29(4):518-21.
11. Dumoulin C, Hay-Smith J. Pelvic floor muscle training versus no treatment, or inactive control treatments, for urinary incontinence in women. The Cochrane database of systematic reviews. 2010(1):CD005654.
12. Scotti RJ, Angell G, Flora R, Greston WM. Antecedent history as a predictor of surgical cure of urgency symptoms in mixed incontinence. Obstet Gynecol. 1998;91(1):51-4.
13. Kulseng-Hanssen S, Husby H, Schiotz HA. Follow-up of TVT operations in 1,113 women with mixed urinary incontinence at 7 and 38 months. Int Urogynecol J Pelvic Floor Dysfunct. 2008;19(3):391-6.
14. Murray S, Lemack GE. Overactive bladder and mixed incontinence. Current urology reports. 2010;11(6):385-92.