Measuring the volume of urine in the bladder is a significant issue in patients who suffer from the lack of bladder fullness sensation or have problems with timeliness getting to the restroom, such as spinal cord injury patients and some of the elderlies. Real-time monitoring of the bladder, therefore, can be highly helpful for urinary incontinence. Bladder volume monitoring technologies can be divided into two distinct categories of invasive and non-invasive. In invasive techniques, a catheter is directly inserted into the urethra to measure the amount of urine accurately. However, it is painful, limits the user’s ordinary movements, and may hurt the urinary tract. Current non-invasive techniques measure the volume of the bladder from the skin using different stationary or portable apparatus at health centers. Both techniques have difficulties and are not cost-effective to use for a long period. Recently, both invasive and non-invasive methods have been attempted to be produced in the form of wearable devices utilizing different sensing and communication technologies. Wearable bladder monitoring devices can be easily used by patients with no or few clinical steps, making them much more affordable than non-wearable devices. While wearable devices seem to be a highly convenient and effective solution, they suffer from few drawbacks, such as relatively low precision. Hence, a great number of studies have been conducted to address these issues. In this article, we review and discuss non-invasive and minimally invasive methods for monitoring the bladder volume. We focus on the most practical and state-of-the-art methods employed in wearable devices, classify them by engineering and medical characteristics, and investigate their specifications, architectures, and measurement algorithms. This study aims to introduce the latest advances in this field to practitioners while comparing the advantages and disadvantages of existing approaches. Our study concludes with open problems and future trends in the area of bladder monitoring and measurement systems.

对于缺乏膀胱充盈感或无法及时上厕所的患者（例如脊髓损伤患者和一些老年人），测量膀胱中的尿量是一个重要问题。因此，实时监测膀胱对尿失禁非常有帮助。膀胱容量监测技术可分为侵入性和非侵入性两大类。在侵入性技术中，将导管直接插入尿道以准确测量尿量。然而，它是痛苦的，限制了使用者的正常运动，并且可能伤害尿道。当前的非侵入性技术在健康中心使用不同的固定或便携式设备从皮肤测量膀胱的体积。这两种技术都有困难，长期使用也不划算。最近，已经尝试使用不同的传感和通信技术以可穿戴设备的形式生产侵入性和非侵入性方法。没有或几乎没有临床步骤的患者可以轻松使用可穿戴膀胱监测设备，这使得它们比非可穿戴设备更实惠。虽然可穿戴设备似乎是一种非常方便和有效的解决方案，但它们也有一些缺点，例如相对较低的精度。因此，已经进行了大量研究来解决这些问题。在本文中，我们回顾和讨论了用于监测膀胱容量的无创和微创方法。我们专注于可穿戴设备中采用的最实用和最先进的方法，根据工程和医学特性对它们进行分类，并研究它们的规格、架构和测量算法。本研究旨在向从业者介绍该领域的最新进展，同时比较现有方法的优缺点。我们的研究以膀胱监测和测量系统领域的开放性问题和未来趋势结束。