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Arrangement of side holes in a double J stent for high urine flow in a stented ureter
Kyungwuk Kim,Hyoung-Ho Kim,최영호,이승배,Yasutaka Baba,Sang-Ho Suh 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.2
A double J stent (DJS) is widely used as an ureteral stent these days. A DJS is composed of a shaft and proximal and distal coils, and it has multiple side holes along the stent axis. The role of side holes must be a supply of detour. Several studies on side holes have been conducted. Various parameters, such as the number of side holes, the distance between adjacent side holes, and the degree of ureteral stenosis, have been evaluated. Studies have shown that increasing the number of side holes increases the overall flow rate, but it has not presented an important role in the absence of ureteral stenosis. In the absence of ureteral stenosis, only a few proximal and distal side holes show a role of detour, and the flow of urine through a stent is negligible. Here, we examine whether urine flow through a stented ureter is maximized by removing side holes in the midshaft and increasing the number of side holes in the proximal and distal segments of the stent shaft. We establish an undulated curved ureter model and compare a stent with only proximal and distal side holes in the shaft with a stent with side holes along the entire shaft in a point of flow rates in the ureter and flow patterns around side holes. The stent with side holes along the entire shaft (16.5 mL/h) shows a higher total flow rate compared with the stent with only proximal and distal side holes in the shaft (12.7 mL/h).
Numerical analysis of the effect of side holes of a double J stent on flow rate and pattern.
Kim, Kyung-Wuk,Choi, Young Ho,Lee, Seung Bae,Baba, Yasutaka,Kim, Hyoung-Ho,Suh, Sang-Ho Pergamon Press 2015 Bio-medical materials and engineering Vol.26 No.1
<P>A double J stent has been used widely these days for patients with a ureteral stenosis or with renal stones and lithotripsy. The stent has multiple side holes in the shaft, which supply detours for urine flow. Even though medical companies produce various forms of double J stents that have different numbers and positions of side holes in the stent, the function of side holes in fluid dynamics has not been studied well. Here, the flow rate and pattern around the side holes of a double J stent were evaluated in curved models of a stented ureter based on the human anatomy and straight models for comparison. The total flow rate was higher in the stent with a greater number of side holes. The inflow and outflow to the stent through the side holes in the curved ureter was more active than in the straight ureter, which means the flow through side holes exists even in the ureter without ureteral stenosis or occlusion and even in the straight ureter. When the diameter of the ureter changed, the in-stent flow rate in the ureter did not change and the extraluminal flow rate was higher in the ureter with a greater diameter.</P>
Numerical analysis of the urine flow in a stented ureter with no peristalsis.
Kim, Hyoung-Ho,Choi, Young Ho,Lee, Seung Bae,Baba, Yasutaka,Kim, Kyung-Wuk,Suh, Sang-Ho Pergamon Press 2015 Bio-medical materials and engineering Vol.26 No.1
<P>A ureteral stenosis or occlusion causes the disturbance of normal urine flow and results in renal failure. Ureteral stents are used to relieve the stagnation of urine in the upper urinary tract. Peristalsis in the ureter, which occurs to help urine flow, becomes to weaken when a stent is inserted and effective peristalsis disappears as time goes on, and a stented ureter seems to be tubular and curved in the human body. Double J stents, which are manufactured by many medical companies and are used widely these days, have different geometries of side holes in the stent shafts. In total, 12 models-six curved models of a stented ureter according to different numbers and positions of side holes and ureteral and stent stenoses and another six straight models for comparison with the curved ones-were made based on the data collected from 19 men. The flow rate and pattern in the stented ureter were evaluated using computational fluid dynamics (CFD). According to the results, curved models reflecting the human anatomy seem to be more desirable in the CFD simulation of urine flow and must be good for evaluating the effect of geometrical variations in stent design on urine flow.</P>
주변 온도가 폐쇄성 수면무호흡증에 미치는 영향에 관한 전산유체역학 연구
박세현(Se-Hyun Park),최영호(Young-Ho Choi),유수타카 바바(Yasutaka Baba),선상원(Sang Won Sun),이창제(Chang Je Lee),곽태수(Tae-Soo Kwak),김경욱(Kyungwuk Kim),김형호(Hyoung-Ho Kim) 대한기계학회 2021 大韓機械學會論文集B Vol.45 No.11
비강과 인두로 구성된 상기도는 호흡 시 표면을 통한 열전달을 포함한 여러 기능을 가지고 있다. 호흡 시 주변 공기온도는 상기도 내부 유동에 관계가 있다. 이때 주변 온도가 폐쇄성 수면무호흡증에 미치는 영향을 분석하기 위해, 폐쇄성 수면무호흡증 환자의 주변 온도(16°C, 20°C, 24°C)에 의한 영향과 상기도의 유동 패턴은 전산유체역학을 이용하여 분석하였다. 상기도 내부 열교환은 비강부분에서 안정화되었으며, Re 수와 Nu 수는 주변 온도가 낮을 때보다 주변 온도가 높을 때 감소하였다. 압력강하는 주걱턱 수술 전에는 16°C에서 4.71 Pa, 24°C에서 4.50 Pa로 감소하였고, 수술 후에도 16°C에서 11.78 Pa, 24°C에서 11.64 Pa로 미소하게 감소하는 경향을 보였다. 상기도 내 유동저항은 압력강하와 같은 경향을 나타내었다. 결론적으로 따뜻한 주변 공기온도에서 호흡하는 것이 폐쇄성 수면무호흡증에 저감에 유리할 것으로 보인다. The upper airway comprising the pharynx and nasal cavity has several functions, including heat transfer during the respiratory cycle to the surface. The ambient temperature is generally consistent in the air flow of the upper airway. Computational fluid dynamics (CFD) was therefore used to analyze the effects of ambient temperatures (16°C, 20°C, and 24°C) and flow patterns of obstructive sleep apnea (OSA) patients. Heat transfer was observed to be stable in the anterior zone, and the Reynolds (Re) and Nusselt (Nu) numbers tended to decrease when the ambient temperature increased. The pressure drops in the pre-orthognathic operation condition were 4.71 Pa at 16°C and 4.50 Pa at 24°C, whereas those in the post-operation condition were 11.78 Pa at 16°C and 11.64 Pa at 24°C. The airway resistance also exhibited the same tendency as the pressure drop. Thus, a higher ambient temperature is likely to be beneficial for reducing OSA.
인체 기반 요관 모델에서의 뇨 흐름에 대한 유체구조 연동해석
김형호(Hyoung-Ho Kim),최영호(Young Ho Choi),이승배(Seung Bae Lee),Yasutaka Baba,김경욱(Kyung-Wuk Kim),서상호(Sang-Ho Suh) 대한기계학회 2018 大韓機械學會論文集B Vol.42 No.9
요관은 뇨를 신장으로부터 방광으로 전달하는 역할을 한다. 요관에 협착이나 폐색같은 문제가 발생하면 임상의는 요관 스텐트를 요관계의 방광으로부터 신우로 삽입한다. 요관에 요관 스텐트를 삽입하게 되면 연동운동은 줄어들거나 소멸되게 된다. 따라서 요관 스텐트가 삽입되었을 때 발생하는 변화에 대해 알아야 할 필요가 있다. DJS가 움직임에 따라 뇨가 내부로 흐르는 유량이 커진 것을 관찰할 수 있었다. DJS의 변형량을 관찰한 결과 신장 깔대기와 방광에서는 변형량이 크지 않았으며 Curl 부분만 조금 움직이는 것으로 나타났다. DJS는 요관의 중간 부분에서 변형량이 큰 것으로 나타났다. DJS가 협착된 부분을 밀치거나 충돌하는 현상이 DJS의 부작용을 더욱 악화시키는 요인이 될 수 있다. The ureter serves to transfer urine from the kidney to the bladder. If stenosis or obstruction occurs in the ureter, clinicians must insert a double J stent (DJS) in the upper urinary system from the renal pelvis to the bladder. When a double J stent is inserted in the ureter, peristaltic movement is reduced or eliminated. Therefore, it is necessary to accurately understand urine flow through the ureter and to predict the changes that may occur when a stent is inserted. Movement of the DJS occurred such that the flow rate of urine inside the stent increased. Observation of DJS deformation revealed that the amount of deformation in the curl portion was moved slightly. Furthermore, the DJS exhibited a large amount of deformation in the middle portion of the ureter. The pushing or colliding of the stenosis with the DJS may further exacerbate side effects.
인체 기반 요관 모델에서의 뇨 흐름에 대한 유체구조 연동해석
김형호(Hyoung-Ho Kim),최영호(Young Ho Choi),이승배(Seung Bae Lee),Yasutaka Baba,김경욱(Kyung-Wuk Kim),서상호(Sang-Ho Suh) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
The ureter serves urine transfer from the kidney to the bladder. If problems such as stenosis or obstruction in the ureter occur, clinicians would like to insert a double J stent in the upper urinary system from the renal pelvis to the bladder. Urine in the ureter smoothly flows with a help of hydrodynamic forces and peristalsis. When a double J stent is inserted in the ureter, peristaltic movement is reduced or eliminated. Therefore, it is necessary to accurately understand urine flow in the ureter and to know the changes which could happen when a stent is inserted. Fluid structure interaction (FSI) simulation was used for the analysis. The FSI simulation is an appropriate method for finding the relationship between urine and a stent in the ureter. Previous studies have been conducted considering only the motion of the ureter. However, in this study considered the motion of the ureter and a double J stent coupled with and analyzed the movement of the stent by urine and its effect.
Analysis of Urine Flow in Three Different Ureter Models
Kim, Kyung-Wuk,Choi, Young Ho,Lee, Seung Bae,Baba, Yasutaka,Kim, Hyoung-Ho,Suh, Sang-Ho Hindawi 2017 Computational and mathematical methods in medicine Vol.2017 No.-
<P>The ureter provides a way for urine to flow from the kidney to the bladder. Peristalsis in the ureter partially forces the urine flow, along with hydrostatic pressure. Ureteral diseases and a double J stent, which is commonly inserted in a ureteral stenosis or occlusion, disturb normal peristalsis. Ineffective or no peristalsis could make the contour of the ureter a tube, a funnel, or a combination of the two. In this study, we investigated urine flow in the abnormal situation. We made three different, curved tubular, funnel-shaped, and undulated ureter models that were based on human anatomy. A numerical analysis of the urine flow rate and pattern in the ureter was performed for a combination of the three different ureters, with and without a ureteral stenosis and with four different types of double J stents. The three ureters showed a difference in urine flow rate and pattern. Luminal flow rate was affected by ureter shape. The side holes of a double J stent played a different role in detour, which depended on ureter geometry.</P>