First clinical application of the novel 6.3 Fr disposable digital flexible ureteroscope for treatment of lower calyx renal stones in anticoagulated patient

Abstract

Managing urinary tract stones in patients on anticoagulant therapy is challenging due to increased bleeding risks. Flexible ureteroscopy (FURS) offers a low-bleeding-risk alternative. A 75-year-old female on Edoxaban for atrial fibrillation presented with recurrent hematuria and a right renal lower calyx stone. FURS using a 6.3 Fr disposable ureteroscope and 10/12 Fr suctioning ureteral access sheath successfully cleared the stone with no complications. The 6.3 Fr disposable digital flexible ureteroscope is effective for managing renal stones in anticoagulant patients, reducing bleeding risks, ureteral injury, and infection. Further research is needed for broader patient applications.

1 Introduction

Urinary tract stones are one of the most common diseases of the urinary system, with a prevalence ranging from 1 % to 20 %. In China, the pooled prevalence of urinary tract stones, renal stones, ureteral stones, and urethral and bladder stones is 8.1 %, 7.8 %, 3.2 %, and 0.5 %. In high-income countries such as Canada, Sweden, and the United States, the prevalence of kidney stones is significantly higher (>10 %), and in some regions, the incidence of kidney stones has increased by more than 37 % over the past 20 years. With the widespread use of anticoagulants and antiplatelet drugs, urologists often encounter kidney stone patients who are on these medications, which presents challenges in treatment. During anticoagulant or antiplatelet therapy, the risk of surgical bleeding increases, while discontinuing these medications may elevate the risk of thrombosis. ^,

According to the European Association of Urology (EAU) guidelines, extracorporeal shock wave lithotripsy (SWL) and percutaneous nephrolithotomy (PCNL) are considered high-risk procedures for bleeding, while flexible ureteroscopy (FURS) is considered a low-bleeding-risk surgical option. In cases of untreated bleeding disorders or ongoing antithrombotic therapy, FURS is a viable alternative to SWL and PCNL due to its lower incidence of complications. The International Association of Urolithiasis (IAU) also considers FURS a low-bleeding-risk procedure, making it a safe and effective treatment option for patients undergoing anticoagulant or antiplatelet therapy. In recent years, disposable digital flexible ureteroscopes have gradually replaced traditional reusable ureteroscopes, as they not only address issues related to high maintenance costs and complex sterilization but also provide comparable or even superior performance in terms of optical resolution, deflection angles, and irrigation flow rates. ^,

In this study, we successfully used the smallest available 6.3 Fr disposable digital flexible ureteroscope for the first time to treat a patient with right renal lower calyx stones who was undergoing Edoxaban therapy for atrial fibrillation. We further evaluated the advantages and limitations of this device in stone management and discussed its potential for clinical application.

2 Case presentation

A 75-year-old female patient presented with “recurrent visible hematuria for 3 months” at a local hospital. She was diagnosed with “right renal lower calyx stone, urinary tract infection, atrial fibrillation, coronary heart disease, post-coronary artery stent placement, type 2 diabetes mellitus, diabetic nephropathy, hyperlipidemia, hypertension, hyperuricemia, carotid artery plaque, and multiple gallstones” and was referred to the Urology Department at the Hong Kong University Shenzhen Hospital. The patient had been taking Edoxaban long-term due to “atrial fibrillation” but discontinued the medication two days prior to her transfer.

Upon admission, laboratory tests showed the following: serum creatinine 125 μmol/L (normal range 44–80 μmol/L), HbA1c 8.0 % (normal range 4.1–6.0 %), uric acid 497.2 μmol/L (normal range 142–339 μmol/L), and urine culture positive for Escherichia coli (ESBL-positive). Liver function, C-reactive protein, procalcitonin, and coagulation tests were all normal. A CT scan revealed a right renal lower calyx stone measuring 17mm × 10mm ( Fig. 1 ).

After admission, the patient was treated for hyperglycemia and hypertension, and low-molecular-weight heparin was used for bridging anticoagulation. She was also given antibiotics, and the urine culture turned negative after treatment. The patient underwent right-sided FURS with stone fragmentation. Under general anesthesia, the patient was placed in a lithotomy position. A semi-rigid 6/7.5 Fr ureteroscope was inserted through the urethra. The bladder appeared normal, and after identifying the right ureteral orifice, a 0.035″ guidewire (150 cm; NiCore® Nitinol, Bard Inc., XXXX, GA, USA) was advanced into the ureter. A 10/12 Fr tip-flexible suctioning ureteral access sheath (TFS-UAS; Shenzhen Kangyibo Technology Development Co., Ltd., Shenzhen, China) was successfully placed over the guidewire, followed by the insertion of a 6.3 Fr disposable digital flexible ureteroscope (HU30M HugeMed) through the access sheath, which revealed the right renal lower calyx stone. A 200μm holmium laser fiber (Lumenis Pulse™ 100H Holmium Laser System, Boston Scientific, XXXX, California, USA) was connected and used to fragment the stone. Afterward, all stone fragments were aspirated with the TFS-UAS. The TFS-UAS was withdrawn under direct vision via the flexible ureteroscope, and no ureteral injury was observed. An Fr 5 Marflow D-J stent (APR Medtech, Oxfordshire, UK) was placed along the guidewire and the suture at the stent tail was fixed to the catheter. The entire procedure was completed smoothly without any intraoperative complications, and the total duration of the surgery was 102 minutes.

A post-operative CT scan on the first day showed that all stones had been successfully cleared ( Fig. 2 ). On the second postoperative day, the patient’s urine color returned to normal, and the catheter and DJ stent were removed at the bedside. The patient resumed Edoxaban anticoagulation therapy on the same day. A follow-up 3 months after surgery showed no recurrence of stones. The patient had a good recovery with no postoperative complications. The stone composition was identified as calcium oxalate monohydrate.

3 Discussion

In the United States, over 6 million patients receive long-term anticoagulant therapy due to atrial fibrillation, mechanical heart valve replacement, or venous thromboembolism. Additionally, dual antiplatelet therapy with aspirin and thienopyridines after coronary artery stent placement has also significantly increased. Each year, about 10 % of patients on anticoagulant therapy undergo surgeries or other invasive procedures that require temporary cessation of medication, and these patients experience a markedly higher incidence of perioperative thromboembolic events and major bleeding compared to the general population. The risk of major perioperative bleeding depends on the type of surgery, the residual effects of anticoagulant drugs, and the timing of restarting anticoagulant therapy postoperatively. The thrombotic risk is primarily determined by underlying conditions (such as valve replacement, atrial fibrillation, venous thrombosis, etc.) and the duration of anticoagulant withdrawal.

The patient in this case was diagnosed with atrial fibrillation three years ago and has been on long-term Edoxaban therapy with no history of hematuria, hematochezia, or other bleeding symptoms. Three months prior, she started experiencing recurrent visible hematuria, which was considered related to her advancing age, diabetic nephropathy, and increased stone burden. Given the patient’s age (75), history of hypertension and diabetes, and a CHADS ₂ score of 3, which indicates a moderate stroke risk with a stroke rate of 5.9–8.5 % per 100 patient-years, discontinuing anticoagulation would further elevate her stroke risk. After discussing with the patient, we decided to opt for a low-bleeding-risk surgery, FURS, to treat the right renal lower calyx stones, instead of high-bleeding-risk surgeries like SWL and PCNL. This approach would minimize bleeding risk and allow for the early resumption of anticoagulation therapy to reduce stroke risk. Therefore, we chose the world’s smallest 6.3 Fr disposable digital flexible ureteroscope to reduce mechanical damage to the ureter and renal pelvis mucosa. A 10/12 Fr TFS-UAS was used during the procedure to reduce ureteral injury, facilitate early removal of the DJ stent, and help alleviate renal pelvic pressure while evacuating stone fragments. In this case, we successfully used the 6.3 Fr disposable digital flexible ureteroscope to clear the right renal lower calyx stones, and postoperative CT showed no residual stones. The recovery was smooth with no infection or other complications. On the second postoperative day, the urine color returned to normal, and the catheter and DJ stent were removed. Anticoagulation therapy with Edoxaban was resumed on the same day.

This new 6.3 Fr disposable digital flexible ureteroscope is currently the smallest commercially available disposable flexible ureteroscope on the market ( Fig. 3 A). Despite its diameter of only 6.3 Fr, the working channel is the same as traditional 7.5 Fr or larger ureteroscopes at 3.6 Fr, and its tip has a smaller bending radius ( Fig. 3 B). This scope offers 285° of bidirectional deflection, adjustable by a dial, allowing the scope body to rotate 60° in either the clockwise or counterclockwise direction, providing visual and operational performance comparable to that of larger ureteroscopes. Compared to the commonly used 7.5 Fr ureteroscopes, The 6.3Fr flexible ureteroscope is thinner, which significantly reduces mechanical trauma to the ureter and lowers the risk of postoperative ureteral stricture, inflammation, and discomfort. The average maximum internal diameter of a child’s ureter is about 3.8 mm, which imposes specific requirements on the instruments used. The smaller diameter of this ureteroscope holds great promise for future use in treating pediatric urinary tract stones. The small bending radius of this scope also makes it advantageous for handling lower calyx stones with small infundibular-pelvic angles (IPA).