Figure 1. Bladder cycling diagram depicting saline bag 20 cm above bladder continuously instilling via suprapubic tube. Reprinted with permission from Children’s Hospital of Philadelphia 2022.

Figure 2. Bladder volumes over time after initiation of continuous daily bladder cycling.

For pediatric urologists, the management of defunctionalized bladders prior to kidney transplantation (KT) remains challenging without clear guidelines for management. Low capacity, defunctionalized bladders can lead to increased hydrostatic pressures and compromise graft kidney function.¹ Many surgeons resort to major reconstructions such as bladder augmentation or urinary diversion to improve storage dynamics. Although bladder augmentation successfully increases bladder capacity and compliance, it also commits children to a lifetime of catheterization and morbidity associated with augmentation.²

Attempts have been made to increase bladder capacity through a variety of techniques. Catheter placement via urethra and manual distention of the bladder has been reported but is associated with significant discomfort/pain and poor efficacy. In the mid-2010s, Dr Douglas A. Canning (DAC) developed a novel technique for expanding bladder volume. The method emphasizes pressure regulation during bladder cycling, rather than volume regulation. This has been primarily used in patients who are believed to have embryologically “normal” bladders secondary to early surgical removal of the kidneys and/or bilateral renal dysplasia.

The method involves patients undergoing placement of a suprapubic tube via percutaneous (preferred) or open approach. Bladders are then exposed to a constant pressure of 20 cm H₂O by mounting the meniscus of a 1 L saline bag 20 cm above the bladder (Figure 1). Bladder cycling is continuous and autonomous 24 h/d. During the day, these bags are held at the appropriate height in a small backpack worn by the patient if able. Patients are surveilled every 2-3 months with suprapubic tube exchange under anesthesia, renal-bladder ultrasound, and assessment of bladder capacity.

Through a multi-institutional collaboration, we sought to determine if our novel method for bladder cycling could successfully increase bladder capacity and avoid bladder augmentation in patients with small defunctionalized bladders. All patients were on near-lifelong renal replacement therapy secondary to primary renal disease or bilateral nephrectomy with defunctionalized bladders presumed to be embryologically normal. To date, a total of 7 patients have undergone this method of bladder cycling with a mean age at the start of cycling of 2.5 years and median initial bladder capacity of <5 cc.

Our patients have shown consistent and significant increases in bladder volumes with duration of bladder cycling (Figure 2). In our cohort, 6 of 7 patients have shown excellent volumetric bladder growth within a relatively short time period. No patients have required bladder augmentation and all patients who underwent KT are volitionally voiding. The median time from start of bladder cycling to KT was 11 months (IQR 6-18) with a mean bladder capacity of 62 cc at time of transplantation. To date, 5 patients have undergone successful KT with no short-term complications in terms of graft or bladder function. Six of the 7 patients were initially recommended bladder augmentation or urinary diversion at an outside institution.

Bladder cycling for small defunctionalized bladders prior to KT is not a new concept. Serrano et al investigated bladder cycling in adults with renal failure who had been anuric for 15-26 years. Their protocol included 3-5 days of intense cycling to assess the degree of bladder dysfunction and expansion potential.³ Moreover, Al Khudair and Mansi were successful with bladder expansion in a 17-year-old patient using twice weekly intermittent catheterization and instillation of saline.⁴ They found that after 3 months of intermittent cycling bladder compliance significantly improved and bladder capacity increased from a mean of 80 to 320 mL. Inoue⁵ and Errando et al⁶ also looked at 11 patients pretransplant with small, poorly compliant bladders and showed that intermittent cycling via suprapubic tube significantly increased bladder capacity and improved urodynamic parameters. Although manual irrigation and intermittent catheterization are alternative techniques to increase bladder capacity, both are less physiological and more demanding than our method of continuous daily bladder cycling. Our technique provides a more physiological, pressure-based method with the potential for 24-hour autonomous bladder cycling.

The DAC technique for bladder expansion is safe, well tolerated, and effective at increasing bladder capacity in patients with defunctionalized, small bladders awaiting KT. Although long-term durability and functionality of these rehabilitated bladders remain unknown, the DAC technique appears to be an excellent initial management strategy that can help avoid bladder augmentation in these patients.