The lower urinary tract (LUT) is sensitive to nervous system pathologies, injuries and dysfunctions that may lead to the loss or reduction of bladder fullness sensation. Urination assistive devices aimed at supporting bladder emptying and continence control have been proposed so far. However, patients may not perceive the urge to urinate and activate the device accordingly. In this framework, bladder pressure and volume monitoring is crucial and would lead to optimize the use of assistive devices and reduce side effects for the patient. Despite its centrality in restoring LUT functions, urinary bladder monitoring remains not fully explored, yet. In this review paper, we summarize the efforts performed at the clinical and research level towards efficient bladder monitoring. The analysis of the current state of the art enabled to identify the challenges of the field and to draw potential future directions in LUT dysfunction management by engineering solutions. After the introduction of technologies to support urination, a major focus is placed on three groups of monitoring devices, that is, instruments for a clinical setting, wearable devices for continuous and domestic monitoring, and implantable sensors for chronic monitoring. Finally, the main challenges are identified and discussed, highlighting the most crucial points and the main treatment opportunities.INDEX TERMS Bladder pressure monitoring, bladder volume monitoring, implantable biorobotic organs, implantable sensors, urinary dysfunctions. FIGURE 3. Examples of clinical imaging instruments to monitor the urinary bladder. Ultrasound-based volume reconstruction systems (Bladder Scan BVI 9400 [253]) through (a) 2D and (b) 3D methods [102], Copyright 1998, Published by Elsevier Inc., [105]. Bioimpedance tomography device employed for EIT [132], Copyright 2016, Taiwanese Society of Biomedical Engineering, with 16 electrodes arranged along different configurations for bladder volume reconstruction and imaging [128], ((c) EIT electrodes [254], Copyright 2020, IEEE). NIRS method exploiting water or oxyhemoglobin as chromophores and detecting light absorption variations during the filling-voiding cycles (d) [142], Copyright 2018, IEEE, and NIRS device [255]. MRI (picture of Michal Jarmoluk from Pixabay): Cavalieri method to compute the volume (e) [153], and representation of a commercial scanner.

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Urinary bladder cancer is the tenth most common cancer in the world with an incidence of approximately 550,000 new cases each year [1]. Non-muscle invasive tumors are locally removed with trans urethral resection or chemotherapy, while invasive tumors (30% of cases) are generally treated with the surgical removal of the entire bladder and the urethra (radical cystectomy) to avoid recurrence [2]. Following cystectomy, uretero- cutaneostomy (i.e., urine drainage from the kidneys to an external container) or neobladder reconstruction with autologous intestine are possible solutions. Although they are standard clinical procedures, they present several complications including possible onset of infections, rupture of the neobladder, tumor recurrence, as well as low patient’s quality of life [3]. This scenario motivates the development of alternative solutions to restore bladder functions, i.e., urinary continence and controlled micturition. Over the years, researchers moved towards the development of fully implantable bioartificial [4] and artificial [5] bladder systems. Considering the Valsalva maneuver (i.e., abdominal torsion) as a possible voiding strategy, two functions are crucial for a complete bladder system: urine collection and fullness sensitivity. In this regard, some preliminary sensing systems have been proposed in literature. However, the solutions are closely related to specific and not bio-inspired geometries [5] or suitable only for small animals [6]. In this framework, we propose a novel biorobotic organ composed of a soft hexagonal-shaped artificial bladder (AB) coupled to a resistive textile sensors-based volume monitoring apparatus. The foldable structure of the AB together with the small thickness and flexibility of the embedded sensors make the system compact and suitable for implantation. The design and fabrication processes are here shown together with a preliminary validation of the sensorized AB.