Emergency Ureteroscopic Treatment for Upper Urinary Tract Calculi Obstruction Associated with Acute Renal Failure: Feasible or Not?

Introduction

A cute renal failure (ARF) is a urologic emergency that must be managed rapidly and carefully; otherwise, the glomerular filtration rate will decline rapidly, associated with the rise of nitrogenous wastes in the blood and water-electrolyte imbalance. Then, a series of symptoms in other organs will be generated. Finally, multiple organ failure will occur, and the lives of the patients will be threatened. ¹

According to statistics, ARF can be attributed to obstruction of the urinary tract in 10% of patients. ² Ureteral calculus is one of the most important factors that cause obstruction. Traditionally, ureteral stent placement and nephrostomy tube drainage are the common approaches for patients with ureteral obstruction caused by ureteral calculi impaction. ³ The definitive management is not carried out until recovery of renal function.

With the development of advanced instruments and techniques, minimally invasive surgical procedures have gradually been applied to the management of ureteral calculi, and their traditional counterparts have been challenged. Enhancements in ureteroscope design have clearly played an important role in the advancement of upper tract endoscopic surgery. The introduction of holmium:yttrium-aluminum-garnet (Ho:YAG) laser lithotripsy, which has become the technical category of choice for impacted ureteral stones, has improved stone-free rates while decreasing the risk of complications significantly. ⁴

In this study, we evaluated the efficacy and safety of emergency ureteroscopy (URS) and Ho:YAG laser lithotripsy without previous stent placement or nephrostomy for managing calculi obstruction of the upper urinary tract that was associated with ARF.

Patients and Methods

From November 2005 to November 2008, 49 patients with ARF that was caused by upper urinary tract calculi obstruction were treated in Renmin Hospital of Wuhan University in China. Their mean age was 52 years (range 30–76 yrs). After hospitalization, the 49 patients were evaluated with history, clinical, radiologic (abdominal ultrasonoraphy, radiography of the kidneys, ureters, and bladder [KUB] and CT), and laboratory assessment (complete blood cell count, renal and liver function tests, electrolytes analysis, and prothrombin time) emergently. Of these 49 patients, the calculi were in bilateral ureters in 39 (79.6%) patients and unilateral ureters in 10 (20.4%) patients with a single functioning kidney. The average stone burden was 1.48 cm (range 1.25–3.20 cm).

Of 88 stones, 26 (29.5%) were located in the distal ureter, 29 (33.0%) in the midureter, and 33 (37.5%) in the proximal ureter (Table 1). Among the presenting complaints, oliguria was noted in 45 patients for 1 to 4 days and anuria in 4 patients for 1 day. Among the clinical findings, there was lumbodynia in 21, chest distress and palmus in 12, nausea in 11, edema in 9, and hypertension in 12 patients. The mean blood urea nitrogen (BUN) level was 15.6 mmol/L (range 12.0–20.9 mmol/L), and the mean serum creatinine (Cr) level was 265.8 μmol/L (range 140.5–680.2 μmol/L). Hyperkalemia (range 5.6–6.8 mmol/L) was observed in 12 (44.4%) patients. Hemodialysis was performed before the procedure in two patients with a serum potassium level of more than 6.5 mmol/L.

All patients received antibiotics (cefuroxime) perioperatively. The patients were placed in the lithotomy position, and general anesthesia was administered. Then retrograde URS with a 11.5F semirigid ureteroscope (Wolf, Knittlingen, Germany) and Ho:YAG laser lithotripsy were performed in all patients by staff urologists (SXY, XHL, HJQ) and by supervised residents. The ureteroscope was passed into the ureter under direct vision following the Zebra guidewire. An 8F ureteral catheter was introduced through a working channel to facilitate insertion of the ureteroscope in 10 patients with a ureteral stricture.

For lithotripsy, a 365 μm laser fiber was used. The 80-W Ho:YAG laser device (Coherent, Palo Alto, CA) was set to 1.4–1.8 J and 10–12 Hz. The criteria for terminating laser lithotripsy was residual fragments <2 mm and the expectation of spontaneous excretion. A 6F Double-J stent was routinely inserted under direct vision in 42 (85.7%) patients and kept in for 4 weeks, except in case of an adverse event; stents remained in place for up to 12 weeks in 7 (14.3%) patients. The stents were removed at the clinic of our center with the Wolf 20F cystoscope after administration of topical urethral anesthesia.

Plain KUB radiography and abdominal ultrasonography were performed to evaluate treatment efficacy on the first postoperative day. The urine volume, serum Cr and BUN levels, and electrolytes values were monitored daily until they returned to normal. After 3 months, all patients were evaluated with abdominal ultrasonography and intravenous urography to further confirm stone clearance and to exclude ureteral stricture formation.

Results

URS and laser lithotripsy was successfully performed in 49 patients. No severe intraoperative complication, such as ureteral perforation, fracture, and mucosal avulsion, occurred. No procedure was converted to open surgery. The mean operative time was 35 minutes (range 13–58 min). The successful fragmentation rate was 95.5% (84/88). The overall stone-free rate was 91.8% (45/49). Stones migrated into the kidney during the procedure in four patients, for whom subsequent extracorporeal shockwave lithotripsy (SWL) was used after recovery of renal function. The final stone-free rate was 100% (49/49) (Table 1). Inflammatory polyps, which had wrapped up the calculi and made lithotripsy difficult in 10 (20.4%) patients, were resected by Ho:YAG laser.

At 6 to 24 hours postoperation, all patients entered into the polyuria stage, and the mean urine volume was 4500 mL/24 hours (range 3500–7500 mL/24h). Seven days after operation, the urine 24-hour volume gradually returned to 1800 mL (range 1500–2000 mL). The renal function of 46 (93.8%) patients returned to normal within 7 days. The mean BUN level descended to 6.5 mmol/L (range 5.5∼8.0 mmol/L), and the mean Cr level descended to 75 μmol/L (range 69∼130 μmol/L). Three (6.1%) patients with giant hydronephrosis had not recovered normal function until 3 months after the operation. There were no hyperpyrexia, lumbago, and severe infection postoperatively. The stents were removed in 4 to 12 weeks. No stone fragments remained, and no postoperative ureteral stricture occurred, which was determined by abdominal ultrasonography and intravenous urography after 3 months.

Discussion

Prospective studies have demonstrated that 1% to 5% of all patients admitted to a general medical/surgical hospital unit will develop ARF, a severe problem. ⁵ It is a syndrome characterized by progressive azotemia, accompanied by metabolic disorder of water and electrolytes. Clinically, it can be separated into three major categories: Prerenal, intrarenal, and postrenal. ⁶

Postrenal ARF is caused by an acute obstruction of the urinary tract that affects the normal flow of urine out of the kidney. ⁷ The blockage causes pressure to build in all of the renal nephrons. The excessive fluid pressure ultimately causes the nephrons to shut down. Among various factors, prevalence of ureteral calculus, whose prevalence is estimated to be 2% to 3%, ⁸ is the most common etiologic factor that causes obstruction of the urinary tract.

The recovery of renal function depends primarily on the extent and the duration of the obstruction and infection. ⁹ Therefore, the most important treatment principle for obstruction-based ARF is to relieve the obstruction as soon as possible and to prevent the infection effectively, for which either a percutaneous nephrostomy or a ureteral stent may serve to decompress the upper tract immediately. Radical pathologic problems, however, are not removed, and a secondary procedure is needed to manage the stones, which will greatly impact the internal milieu of the patients and increase morbidity.

At present, because of the development of advanced technology, minimally invasive treatment options are available for ureteral calculi. Through the minimally invasive treatment era, SWL was generally accepted as first-line treatment for upper tract ureteral stones; however, there was some controversy concerning use for middle and lower tract ureteral stones because of the difficulties in visualizing stones overlying the sacrum and lower success rates for large impacted ureteral calculi. ^{10 –12}

URS plays an important role in the management of urinary calculi as increasing technologic advancements allow easier access to stones in all parts of the kidney and ureter. Regardless of the location of the ureteral stone, access and definitive treatment are commonly achieved with minimal risk of complications. Semirigid and flexible URS provides a 90% to 100% stone-free rate for distal ureteral calculi and a 74% stone-free rate for proximal ureteral calculi. ¹³

Among Lithoclast lithotripsy, electrohydraulic lithotripsy, and Ho:YAG laser lithotripsy, Ho:YAG laser lithotripsy is the current gold standard ¹⁴ because of its effectiveness in fragmenting stones of any composition and its excellent safety profile. In a comparative study between Ho:YAG and Lithoclast lithotripsy for ureteral stones, Jeon and associates ¹⁵ reported their experience in 51 patients. The immediate stone-free rate for Ho:YAG laser and Lithoclast lithotripsy was 96% and 73.1%, respectively. At 3 months, the stone-free rate was 96% and 84.6%, respectively. A Ho:YAG laser was associated with shorter operative times and shorter hospital stays in comparison with Lithoclast lithotripsy. ¹⁵

In another comparative study between electrohydraulic and Ho:YAG laser in ureteroscopic management of ureteral calculi, a total of 23 and 47 consecutive patients underwent electrohydraulic and Ho:YAG lithotripsy, respectively. Success rates for Ho:YAG laser lithotripsy and electrohydraulic lithotripsy at the end of the procedure were 97% and 65%, respectively. The 3-month stone-free rate was 94% vs 97% for electrohydraulic and Ho:YAG lithotripsy, respectively. ¹⁶ These studies demonstrate that the combination of URS with the Ho:YAG laser can improve stone-free rates while decreasing the risk of complications and has become an excellent choice for impacted ureteral stones. ¹⁷

The mechanism of Ho:YAG laser lithotripsy is photothermal. Ho:YAG energy heats the stones to a critical thermal threshold at which the stone composition is altered, yielding a stone crater and small fragments, thereby minimizing upward stone migration. ¹⁸ The advantage of the Ho:YAG compared with other intracorporeal lithotripter devices lies mainly in the miniaturization of instruments and excellent fragmentation of all types of calculi, including calcium oxalate monohydrate and cystine. ¹⁹ It fragments stones with an ablative effect, removing portions of the stone as dustlike particles during the fragmentation procedure. This makes it suitable for large ureteral stones while avoiding the need for removal of larger fragments by baskets or forceps.

As expected, the successful fragmentation rate was 95.5% (84/88) in our study. The complete disintegration reduces the number of entries through the ureteral orifice and shortens operative time. In this study, the overall stone-free rate was 91.8% (45/49), and the mean operative time was 35 minutes (range 13–58 min). Furthermore, the wavelength of 2100 nm of Ho:YAG laser, which is absorbed by water present in tissue, provides the laser with tissue ablation properties. ²⁰ Because of these unique effects, the holmium laser is also useful in stricture incision and tissue resection. In this study, inflammatory polyps had wrapped up the calculi and made lithotripsy difficult in 10 patients; polyps were resected by Ho:YAG laser with satisfactory results.

Despite its low incidence, ureteral perforation is a severe complication that should be prevented during the operation. In our experience, to avoid ureteral perforations, the operator should pay more attention to the following two principles: First, the staff urologists should have skilled technique in endoscopic manipulation and Ho:YAG laser lithotripsy. The procedure should be gentle and a clear field of vision should be maintained. Second, it is important to always visually identify the laser tip and its tracer light during disintegration. The safe distance between the laser tip and the ureteral mucosa should be more than 1 mm.

The purpose of URS and Ho:YAG laser lithotripsy for patients with ARF is to relieve obstruction and restore renal function. Therefore, we need to shorten the operative time as much as possible, and we do not need to clear out all the calculi in a single operation. In this study, stones migrated into the pelvis during the procedure in four patients. SWL was used after recovery of renal function; successful fragmentation was achieved after the secondary procedure. The stone-free status was determined by abdominal ultrasonography and intravenous urography after 3 months.

We consider that a Double-J stent should be inserted routinely after the operation for these reasons: During lithotripsy, ureteral mucosa will be irritated to various degrees, which will result in hyperemia and edema of the ureteral wall. In this situation, the stone debris, even if very small, may suddenly cause postoperative ureteral obstruction. The poor drainage caused by hyperemia, edema, and stone debris would increase renal pressure and cause kidney infection. All of these would increase the chance of postoperative complications, such as infection, backstreaming, and ureteral stricture. In this study, all of the patients routinely had insertion of a Double-J stent at the end of the operation. No postoperative ureteral stricture was found 3 months postoperatively.

Although Ho:YAG laser lithotripsy gives us a safer and more efficacious treatment option, it is not indicated in all patients with ARF caused by upper urinary tract calculi obstruction; patients must be strictly selected. Patients with severe urethral stricture, severe benign prostatic hyperplasia, or deformity of the hip joint need to be treated by other methods, such as percutaneous nephrostomy or ureterolithotomy. For patients with serious urinemia, especially severe hyperkalemia, hemodialysis should be the priority before operation. ²¹ In this study, hemodialysis was performed in two patients with serum potassium higher than 6.5 mmol/L preoperatively, after which lithotripsy were performed successfully with lower risk.

Conclusion

The combination of URS with Ho:YAG laser is an excellent choice for managing calculi obstruction of the upper urinary tract that is associated with ARF. This combination technique can be used safely and effectively by skilled urologists who are familiar with standard endoscopic procedures and trained in the use of the holmium laser in strictly selected clinical situations.