Introduction: The lack of peritoneal dialysis (PD) catheters designed explicitly for neonates creates significant challenges in the provision of neonatal PD. High resource settings can circumvent this limitation by resorting to alternative extracorporeal dialysis methods. However, in low-resource settings, PD remains the preferred dialysis modality, and the use of off-label catheters for PD results in complications such as omental wrapping and occlusion. This study introduces a novel catheter design featuring a multi-diameter side port configuration and a helical geometry. Methods: We employed numerical simulations to identify an optimal multi-diameter side port configuration, to address fluid dynamic issues that lead to catheter occlusion and omental wrapping. Following the simulations, we experimentally evaluated the catheter’s performance in a series of benchtop tests designed to simulate physiological conditions encountered in neonatal PD. Results: Our experimental evaluations demonstrated that the helical catheter outperforms commonly utilized pigtail catheters with same-sized diameter side ports by consistently achieving superior drainage efficiency during fibrin clot occlusion and omental wrapping tests. Conclusion: The catheter is intended to be placed at the bedside to perform renal replacement therapy for neonates in low-resourced settings.

Peritoneal dialysis (PD) is an extensively used [1] procedure for neonates suffering from acute kidney injury (AKI), which is prevalent in 40% of hospitalized neonates [2]. Of these, approximately 5% require renal replacement therapy (RRT) to manage their condition, highlighting the critical need for accessible RRT options [3]. In low-resource settings (LRS), PD often represents the only viable RRT due to limited access to more advanced therapies [4]. However, the high cost of PD catheters poses a significant challenge in LRS, where financial constraints prevent families from acquiring the necessary equipment, thereby increasing the vulnerability of children to health risks. Neonates in LRS with severe AKI requiring RRT often do not have access to surgical expertise for chronic PD catheter placement, nor access to extracorporeal therapies. As a result, bedside placement of a temporary PD catheter remains the best practical option for RRT, yet catheter options are limited.

As of 2020, it has been shown that 68% of patients in LRS were dialyzed with PD, in comparison to patients in high resource settings where 72% were dialyzed with hemodialysis (HD) [1]. A retrospective study demonstrated that in an audit review of 593 pediatric patients who required dialysis from 1998 to 2020 at the Red Cross War Memorial Hospital in Cape Town, South Africa, 56.8% required dialysis for less than 5 days and 80.8% required dialysis for 7 days or less. Additionally, of the patients that received dialysis, 38.6% weighed less than 5 kg and 61.6% weighed less than 10 kg [5]. In retrospect, PD remains underutilized in LRS, where a large gap in the utilization of PD is seen. Reasons for this gap include, but are not limited to, the cost of PD fluids and associated equipment, workforce shortages and limited expertise to prescribe and perform PD, and socio-economic barriers such as the unavailability of electricity and running water [6]. In addition to challenges in utilizing PD, there are also challenges in administering the therapy. In comparison to HD, PD offers lower clearance and lower and less precise fluid removal [7]. The majority of PD equipment is also not intended for use in neonates, and the nature of anatomy in neonates with limited intra-peritoneal space and thin abdominal walls makes the insertion of the standard Tenckhoff catheters and stylet-based rigid catheters difficult with associated high complication rates [8]. One retrospective study observed that 46% of pediatric patients initially undergoing acute PD transitioned to HD due to technique failure, with 8% experiencing catheter malfunction and 20% demonstrating inadequate clearance during PD [1, 9‒13]. Specifically in infants, a separate study reported leakage at the exit site to occur in 31% of patients, blockage in 26%, migration in 23%, and infection in 18% during acute PD [14].

Suboptimally sized catheters can increase complication rates in PD, including occlusion, omental wrapping, infection, and leakage. In two separate studies evaluating the Cook Multipurpose Drainage catheters for PD at the Red Cross War Memorial Hospital, the prevalence of catheter occlusion ranged from 15% to 36% [15, 16]. In 2017, an international survey of pediatric nephrologists reported that PD is available in 100% of the sites where pediatric nephrologists practice [17]. Yet, the only device that was designed for acute PD that was appropriately sized for neonates, the Cook Acute Straight Peritoneal Dialysis Catheter, is no longer commercially available due to changing regulatory requirements and business conditions. This catheter, however, also had significant design limitations for treatment of neonates, such as blockage [16]. The absence of a catheter intended and sized for neonatal use leads to off-label use of other catheters that were not designed for PD, resulting in an elevated risk of mechanical malfunction among other complications [15]. This gap in specialized catheters leaves a vulnerable population underserved, emphasizing the urgent need for accessible and cost-effective resources.

Previous studies have reported the influence of side port dimension in preventing occlusions in ventricular catheters [18‒20]. In this study, we propose an innovative neonatal PD catheter to be placed at the bedside for acute RRT in LRS. Our design addresses the common mechanical malfunctions during PD – catheter occlusion and omental wrapping – by incorporating a novel side port configuration and catheter geometry.

Catheter Design

We numerically simulated the fluid dynamics of an 8.5 Fr Multipurpose Drainage Catheter (Cook, Bloomington, IN, USA), a catheter used at the bedside for temporary PD in LRS. Utilizing COMSOL Multiphysics, we made a 2D computer fluid dynamics analysis of the flow through the catheter’s side ports. The simulation assumed a laminar flow through the catheter and used the Navier-Stokes equation to calculate the steady state velocity values. While the peritoneal cavity presents a complex structure, we simplified the simulation by representing it as a large rigid-wall rectangle as our interest is solely on the fluid dynamics in the proximity of the side ports. The catheter was modeled as the lumen’s cross-section pattern, and it was simulated as internal walls with no slip boundary condition. The outer wall was set as the inlet boundary condition with a pressure of 15 mm Hg and the drain of the catheter was set as the outlet boundary condition at atmospheric pressure. A parametric study was conducted systematically varying the diameter of the side ports to generate an evenly distributed flow across all the side ports.

The novel catheters employed in this study were 8.5 Fr polyurethane catheters fabricated through a thermoforming process, utilizing a custom-made mold to shape the distal end into a helical geometry. Described in Figure 1a, the catheters were heated to 175°C for 10 min and immediately cooled in an ice bath for 2 min. Ten side ports corresponding to the previous numerical analysis were created with an appropriately sized punch on the inside of the helix spaced 10 mm apart.

Fig. 1.

a Catheter shaping process. b Normal function of a drainage catheter for the use of PD. c Fibrin clot occlusion of catheter side ports during PD. d Simulated fibrin occlusion of side ports in a bench top setting. e Method for simulating a peritoneal cavity. f Simulated peritoneum with drainage catheter placement in a bench top setting.

Fig. 1.

a Catheter shaping process. b Normal function of a drainage catheter for the use of PD. c Fibrin clot occlusion of catheter side ports during PD. d Simulated fibrin occlusion of side ports in a bench top setting. e Method for simulating a peritoneal cavity. f Simulated peritoneum with drainage catheter placement in a bench top setting.

Close modal

The helical geometry, featuring 10 side ports, extends along the distal 5 cm of the catheter, with this length specifically designed to suit the size of a neonate’s peritoneum. The overall catheter length was 25 cm to align with the experimental setups devised for testing. This helical design, with side ports along the inner side of the helix, protects the side ports from omental wrapping. The optimized side ports configuration reduces high-pressure zones, thus preventing particle accumulation at a single location and reducing the probability of catheter occlusion.

Experimental Evaluation

To test our novel side port configuration efficacy to reduce fibrin clot occlusion, we utilized a clot analog (True Clot, Charlottesville, VA, USA) prepared at a ratio of 1:5 to replicate a fibrin-rich clot consistency. Mimicking the peritoneal cavity during PD as seen in Figure 1b and c, a water reservoir filled to generate a hydrostatic pressure of 15 mm Hg was prepared for catheter insertion and testing shown in Figure 1d. Both catheters evaluated, the pigtail and the helical, had a proximally placed fibrin clot analog occluding the side ports, and the resulting outflow rate was measured for both.

To evaluate the effectiveness of the helical catheter geometry in preventing omental wrapping, we simulated the peritoneal cavity by filling a plastic bag with 1 L of water. A thin sheet of omentum analog, generated by diluting the clotting solution to a 1:10 ratio, replicated a gelatinous omentum-like consistency. The catheters under examination were introduced into this peritoneal cavity replica beneath the omentum analog to induce omental wrapping shown in Figure 1e. Utilizing a blood pressure cuff, we applied a 15 mm Hg pressure in the peritoneal cavity model to drive fluid out, and the resulting outflow rates were measured for each catheter configuration as shown in Figure 1f. All experiments were repeated five times to obtain consistent and reliable results.

The results of the numerical analysis performed on the control pigtail catheter with 5 equal-diameter side ports shown in Figure 2a demonstrate increased velocity at the 2 most proximal side ports while the remaining 3 side ports had a velocity close to 0 m/s. Based on the velocities obtained from the software and the surface area of the side ports, the percent of fluid drained through each side port was calculated. The bar plot shown in the insert of Figure 2a shows that over 70% of fluid will drain through the two most proximal side ports, creating a high-pressure region adjacent to these side ports. This high-pressure region in a critical section of the catheter is detrimental to its performance in cases of occlusion as it concentrates surrounding solid particles in a confined area, increasing the likelihood of catheter occlusion.

Fig. 2.

a COMSOL simulation of control side port design drainage; inset: distribution of drainage along each side port number from left to right along the simulated control catheter. b COMSOL simulation of variable side port size design drainage; inset: distribution of drainage along each side port number from left to right along the simulated variable side port catheter. c Image of helical shaped multi-diameter side port drainage catheter. d Drainage volume of helical and control catheters with the presence or absence of a fibrin clot analog. e Drainage volume of helical and control catheters with the presence or absence of omental wrapping. f Difference in drainage in the presence of a different occlusion method.

Fig. 2.

a COMSOL simulation of control side port design drainage; inset: distribution of drainage along each side port number from left to right along the simulated control catheter. b COMSOL simulation of variable side port size design drainage; inset: distribution of drainage along each side port number from left to right along the simulated variable side port catheter. c Image of helical shaped multi-diameter side port drainage catheter. d Drainage volume of helical and control catheters with the presence or absence of a fibrin clot analog. e Drainage volume of helical and control catheters with the presence or absence of omental wrapping. f Difference in drainage in the presence of a different occlusion method.

Close modal

Leveraging the numerical analysis and manufacturing feasibility, we selected a multi-diameter side port configuration consisting of 10 side ports, where the first 5 proximal side ports are 1 mm in diameter and the 5 distal side ports are 2 mm in diameter, shown in Figure 2b. This reduces the flow rate at the proximal side ports and evens the distribution of the flow rate across the tip of the catheter. The bar plot in the insert of Figure 2b demonstrates how the additional side ports extend the draining area of the catheter, thus maintaining the functionality of each of the side ports, and significantly reducing the flow concentration at a single location.

After establishing the ideal side port configuration to mitigate clot formation in the proximal side ports, we next sought to test our design, shown in Figure 2c, against occlusions from fibrin clots within the peritoneum. The outflow rate was measured for both the control and helical catheters under free flow and occlusion, and the results are plotted in Figure 2d. The mean total volume drained after 5 min by the pigtail catheter with free flow was 462 ± 6.9 mL, and when occluded, the flow decreased to 345 ± 55 mL. The helical design with multi-diameter side ports drained a mean total volume of 308 ± 2.3 mL, and when occluded, the flow decreased to 289 ± 13.3 mL. The greater the difference between free flow and occluded conditions indicates the fibrin clot analog hinders the draining performance of the catheter decreasing the outflow rate.

As shown in Figure 2e, the wrapped helical catheter drained a mean total volume of 163 ± 9.2 mL, while during free flow, it drained 215 ± 1.8 mL. The pigtail control total volume drained during free flow was 224 ± 8.9 mL and during omental wrapping decreased to 75 ± 42.8 mL. The discrepancy between the total volume drained by each catheter during the fibrin clot occlusion versus the omental wrapping test is attributed to the difference in experimental setups. The fibrin clot occlusion experimental setup had constant hydrostatic pressure, while the pressure during the omental wrapping experimental setup was applied through a blood pressure cuff.

The change in drainage performance for each condition is shown in Figure 2f. During the occlusion experiment, the pigtail control had a decrease of 117 mL and the helical catheter demonstrated a decrease of 19 mL. The tendency continued for the omental wrapping experiment, where the drainage decrease of the pigtail control was 149 mL versus 52 mL the helical catheter. Therefore, the helical design enabled more consistent drainage performance in the simulation of fibrin clot occlusion and omental wrapping.

Catheter occlusion and poor drainage have been reported as main causes of termination or catheter change during PD. Our innovative neonatal PD catheter design addresses these challenges by introducing two critical modifications compared to commercially available catheters. The first key feature is the incorporation of a multi-diameter side port configuration, strategically designed to mitigate the high-pressure zones typically observed in the two most proximal side ports of standard catheters equipped with five same-sized diameter side ports. This novel design aims to evenly distribute pressure across all side ports, thus preventing the formation of localized high-pressure zones. Specifically, the integration of smaller diameter side ports in the proximal section introduces increased resistance to flow, redirecting more flow toward larger diameter side ports. This distribution strategy minimizes the risk of concentration for particles, clots, or solids at any specific side port, reducing the likelihood of catheter occlusion. In contrast, catheters featuring same-sized diameter side ports tend to concentrate the majority of the flow, along with associated particles, clots, and solids, into the proximal side ports, leading to occlusion and rendering the catheter ineffective. The second feature involves a helical geometry designed to minimize surface contact between the catheter and the omentum, effectively protecting the side ports from exterior occlusion and thereby reducing the likelihood of adhesion and subsequent omental wrapping. Notably, the side ports are strategically positioned on the inner side of the helix, while the outer side acts as a protective barrier, preventing omental occlusion of the side ports.

Subsequent experimental evaluation supports the efficacy of our multi-diameter side port configuration. In the fibrin clot occlusion setup, the helical catheter demonstrated superior performance compared to the pigtail catheter that served as the control. The helical design exhibited a smaller decrease in outflow rate during occlusion, emphasizing its resilience against fibrin clot hindrance. The quantified differences in total volume drained under free flow and occluded conditions underscore the advantage of the multi-diameter side port configuration in maintaining consistent drainage performance. The variation in total drainage volume between the control and helical catheters primarily arises from the elevated hydraulic resistance attributed to the difference in their lengths. The extended length of the helical catheter leads to an increase in hydrostatic pressure within the catheter’s lumen, influencing the results.

Furthermore, the helical geometry’s effectiveness in preventing omental wrapping was evident in the experimental setup simulating the peritoneal cavity. The helical catheter demonstrated a substantially smaller reduction in total volume drained during omental wrapping compared to the pigtail catheter. This outcome highlights the helix’s ability to resist omental adhesion, providing an additional layer of catheter robustness in clinical scenarios prone to omental wrapping.

Limitations exist to the design and implementation of this catheter. The current experimental setup has yet to be tested with an industry-standard proximal drainage port. However, the addition of this component is not expected to contribute to occlusion or decrease in flow rate. Additionally, this catheter is only designed for acute indications, specifically in neonates. If chronic dialysis were to become necessary, this catheter would bridge the time for clinicians and hospitals to allocate resources and/or transfer the patient for placement of a tunneled PD catheter.

Our findings suggest that both the multi-diameter side port configuration and helical geometry contribute significantly to improving the performance and durability of a PD catheter designed to deliver RRT to neonates. These design modifications address critical issues such as occlusion and omental wrapping, which are prominent causes of catheter failure. Implementation of these innovations could potentially enhance the reliability and lifespan of neonatal PD catheters, especially in resource-constrained settings. Importantly, addressing the cost-effectiveness of these solutions is crucial for their adoption in these countries. The cost of a Cook Fuhrman catheter, often used off-label for this application in LRS, can exceed USD 100. In contrast, producing a device for this specific indication allows for modifications that can reduce costs like material selection, streamline the manufacturing process, and make an efficient regulatory path. Our catheter is designed such that it can be placed at the bedside via the Seldinger technique, allowing its use in approximately 84% of patients who receive PD at bedside in LRSs that may not have ready access to pediatric surgical care [5]. Beyond the scope of neonatal care, this technology has the potential to be scaled up for applications in infant, young child, and adult PD. Further preclinical studies are warranted to evaluate these promising results prior to clinical validation.

We would like to thank Dyvia Patil for her support in providing knowledge of Cook Medical’s products and arranging stock material to be provided for this project. Additionally, we would like to thank Ty Morgan for sharing his concept of a helical-shaped catheter.

An ethics statement was not required for this study type since no human or animal subjects or materials were used.

Cook Medical provided material support by supplying stock catheter tubing for test samples. Carl Russell III was employed by Cook Medical between August 2020 and August 2022.

Funding was provided by the Indiana University School of Medicine and Purdue University’s Weldon School of Bioengineering in the form of an Engineering in Medicine Pilot Award (D.E.S., H.W.L., A.L.). Catheter tubing was purchased from COOK Medical. The funder had no role in the design, data collection, data analysis, and reporting of this study. The authors have no conflicts of interest to report.

Sergio Ruiz Vega, Carl Russell III, Mignon McCulloch, Aaron Lottes, Hyowon Lee, and Danielle E. Soranno conceptualized the experimental design. Sergio Ruiz Vega and Carl Russell III collected and analyzed data. Sergio Ruiz Vega, Carl Russell III, and Siting Zhang drafted the manuscript. Aaron Lottes, Hyowon Lee, and Danielle E. Soranno provided critical revisions. All authors approved the final manuscript.

All relevant data are reported in the article. Additional data are available upon request to the corresponding author.

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