Postoperative Renal Abscess Following Tip-Flexible Suctioning Ureteral Access Sheath and Digital Ureteroscopic Lithotripsy: A Case Report

Introduction

Ureteral access sheaths (UAS) are designed to facilitate flexible ureteroscopy (FURS) in the treatment of urolithiasis by improving surgical vision, reducing intrarenal pressure, and decreasing postoperative infectious complications [1,2]. The tip-flexible suctioning (TFS) UAS is a relatively novel device, and small-scale retrospective cohort studies found that it was superior to traditional UAS [1,3,4]. Reported complications of the TFS-UAS combined with FURS included perirenal infection, urinary extravasation, and bleeding. However, the incidence of postoperative renal abscess formation was not reported in the literature.

We present the case of a 57-year-old woman who underwent TFS-UAS with digital flexible ureteroscopic lithotripsy for multiple right renal stones. Stone clearance was 100%. However, she had renal abscess formation 8 days later, which progressed to septic shock. She was successfully treated with more aggressive antibiotics.

Case Report

A 57-year-old woman presented with right lumbar pain that had persisted for 1 year. She was afebrile. A plain computed tomography (CT) scan revealed multiple renal pelvicalyceal stones (maximum diameter 20×9 mm; maximum CT value 1373 Hounsfield units [HU]; average CT value 1093 HU; Figure 1A) and a stone located in the lower calyx (5×4 mm; Figure 1B). Biochemistry results revealed a white blood cell count of 8.19×109/L with 74.5% leukocyte ratio, and serum procalcitonin was 0.07 ng/mL. Preoperative urine culture was negative. She denied a history of any underlying medical illness.

She was scheduled for elective digital disposable flexible ureteroscopic lithotripsy (7.5 Fr; HU30S, Shenzhen HugeMed Medical Technical Development Co., Ltd., Shenzhen, China) combined with a novel TFS-UAS (12–14 Fr; 35 cm; Shenzhen Kangyibo Technology Development Co., Ltd., Shenzhen, China; Figure 2). The setting of the negative-pressure suctioning system was 200 mmHg. The irrigation system pump system was initially maintained at a 0.2 L/min flow rate during stone fragmentation and switched to 0.5 L/min during suction with 30 mmHg pressure throughout. Holmium laser lithotripsy (Lumenis Pulse™ 100H Holmium Laser System, Boston Scientific, NJ, USA) was performed at 0.6 J energy setting and 50 Hz frequency. A Cook® stone removal basket was used to move the stone located at the lower calyx to the upper calyx and fragmentation. All fragments were effectively removed and a 5 Fr double-J stent was implanted at the right ureter before conclusion of the operation. The operation lasted 88 minutes. Approximately 5 L of irrigation saline was used. The patient received postoperative antibiotics for 48 hours and was discharged on the second postoperative day.

Eight postoperative days later, she presented to the emergency department due to persistent high fever unresolved by home remedies. Her body temperature was 39.6°C and other vitals were stable. Emergency plain CT was performed and showed that the double-J stent was intact and there was no residual stone. She was admitted to the urology department for observation while she received intravenous Ertapenem. Her condition deteriorated as blood pressure dropped to 80/50 mmHg and body temperature was 41.3°C, which immediately led to the suspicion of septic shock. She was immediately transferred to the Intensive Care Unit (ICU) to receive resuscitation and IV meropenem. Enhanced CT revealed formation a right renal abscess (Figure 3). She remained in the ICU for 4 days and was transferred back to the urology department to continue antibiotic therapy with levofloxacin once she became stable. Urine culture showed E. coli infection. The patient was discharged 8 days later when her fever subsided and her vitals were stable. She was prescribed a 2-week oral levofloxacin regimen. Follow-up ultrasound revealed that the right renal abscess had resolved.

Discussion

Technical advancements and increased experience in FURS combined with laser lithotripsy has yielded excellent outcomes in the management of stones. There has been an increasing trend of employing FURs in treating upper urinary tract stones with diameters ≥2 cm rather than percutaneous nephrolithotomy [5]. The addition of UAS in FURS remains controversial. A statewide collaborative study demonstrated that UAS significantly increased the odds of postoperative emergency department visits and hospitalization for flank pain, other unspecified causes, hematuria, urinary tract infection (UTI)/pyelonephritis, and fever [6]. However, this is the first documented case of renal abscess following uncomplicated FURS.

There are many options for conventional UAS, but 12/14F UAS are regarded as the universal UAS that accepts all FURS [7]. To maintain a safe intrarenal pelvic pressure (IPP), it is recommended to follow the basic rule where the ratio of ureteroscope-sheath diameter (RUSD) is ≤0.75 [8]. TFS-UAS are often combined with negative-pressure suctioning systems, also known as flexible vacuum-assisted UAS, which are considered an upgrade to traditional negative-pressure UAS [9]. When utilizing negative-pressure UAS, an in vitro study recommended that a RUSD <0.85 to maintain a safe IPP [10]. In our case, the RUSD was 0.63, which was much lower than recommended. The reduced and controlled IPP allows FURS to cross the ureteropelvic junction and enter the renal pelvis and calices without causing impact [3]. The suction system, combined with the irrigation flow, can effectively remove renal stones, thereby increasing stone clearance rates [11].

In our case, the patient did not present with any risk suggestive of postoperative infectious complications. Therefore, it was suspected that her sepsis due to the combination of increased IPP and the presence of bacteria in the urinary tract. A systematic analysis revealed that a prolonged operative time, recent history of positive urine culture, UTI, or antibiotic use, pyuria/nitrites, small-caliber ureteral access sheath, struvite stone, high irrigation rate, and comorbidities are independent risk factors for infection after retrograde intrarenal surgery (RIRS) [12]. Gauher et al compared the efficacy of 2 different sizes of flexible and navigable suction UAS in RIRS and found that the 10 Fr size demonstrated a higher stone-free rate than the 12 Fr size, and no infectious complications occurred [13]. However, a retrospective by Zhang et al found that the incidence of infectious complications was significantly lower in TFS-UAS than traditional UAS (8.8% vs 18.8%, p=0.037, respectively) [1]. Unfortunately, there remains limited evidence to determine the actual rate of postoperative sepsis of TFS-UAS.

Chen et al used a patented designed intelligent irrigation and suctioning intraluminal pressure-control platform and integrated pressure-measuring suctioning UAS during FURS suctioning lithotripsy that could effectively achieve excellent stone-free rates in the management of 2–3 cm upper urinary tract stones, which was comparable to the effect of percutaneous nephrolithotomy [14]. Novel ureteroscopes have also been developed to sense IPP [15,16], further research is needed to elucidate its efficacy. Regardless, it is necessary to carefully use these devices to reduce the risk of postoperative UTI.

The inability to monitor intraoperative IPP is a shortcoming of our patient’s operation. IPP fluctuations and sudden raise may have caused our patient’s postoperative renal abscess formation. Our center is experienced in performing RIRS for urinary tract stones, and we found the novel TFS-UAS with its flexible tip is an innovative design that helps reach the target calyx. The addition of a negative-pressure suctioning system can effectively suck out most debris from ureteroscopic lithotripsy. Even small, residual segments that are asymptomatic can be removed, which can possibly reduce the chances of stone relapse within 5 years after surgery [17]. Additionally, the need of using stone-retrieval baskets is reduced, thereby reducing operation cost [1,18]. Nonetheless, this case report shows the risk of renal abscess formation after uncomplicated TFSUAS combined with digital flexible ureteroscopic lithotripsy.

Conclusions

TFS-UAS combined with digital flexible ureteroscopic lithotripsy can achieve excellent stone clearance. However, intraoperative IPP changes can increase the risk of renal abscess formation, even after an uncomplicated procedure.