Solo Ultrasonography-Guided Percutanous Nephrolithotomy for Single Stone Pelvis

Introduction

F ernström and colleagues ¹ were the first to describe percutaneous nephrolithotomy (PCNL) in 1976. As a result of the progress of instrumentation and appearance of different methods of stone disintegration, PCNL is considered as first-line treatment of renal stones that are more than 2 cm in diameter. ² Pelvicaliceal system (PCS) access is the first and most important step in successful PCNL, and it is mostly performed under fluoroscopy guidance, which carries risk for all the medical team. In an attempt to decrease this risk, Osman and associates ³ described PCNL puncture under ultrasonography (US) guidance; then they completed all the remaining steps under fluoroscopy guidance. Hosseini and coworkers ⁴ also described US-guided PCNL for single stone pelvis (24–46 mm in diameter) in mildly to moderately dilatated PCS. In our study, we evaluated the safety and the outcomes of totally US-guided PCNL in single stone pelvis (20–30 mm in diameter) in moderately to markedly dilatated PCS.

Patients and Methods

From April 2008 to April 2010, a prospective study of 34 patients (22 men and 12 women) whose ages ranged from 25 to 55 years (mean 29.5 y) were included in our study (Table 1). All patients had unilateral single stone pelvis in a moderately to markedly dilatated PCS with stone size ranging from 20 to 30 mm (mean 24 mm).

Patients with multiple stones, staghorn stone, mild or nondilatated PCS even with single stone pelvis, anomalous kidney, and stone in a caliceal diverticulum were excluded from our study. All patients were subjected preoperatively to complete history, clinical examination, laboratory investigation in the form of blood values, coagulation profile, level of serum creatinine, liver function, and urinalysis and culture.

Radiologic investigations preoperatively were radiography of the kidneys, ureters, and bladder (KUB) to measure the stone size, abdominal US to measure radiolucent stone, and intravenous urography to evaluate the degree of hydronephrosis.

The procedures were performed in our urology department under general anesthesia by an experienced urologist; 1 g of cefatriaxone was administered 2 hours perioperatively; cystoscopy was performed, and a 6F ureteral catheter was inserted with the patient in the lithotomy position; then the position was changed to the prone position with elevation of the flank to allow fixation of the kidney during the procedures. Initially, US was performed to exclude the presence of any organ in the path of the puncture. Saline was infused through the ureteral catheter to ensure the ballooning of the PCS, followed by midcaliceal puncture through the most convex point of the distended middle calix by using 18-gauge needle through the US needle-guided system. A real-time gray scale ultrasound system with 3.5 MHz transducer (BK Medical, Herlev, Denmark) was used in this study. All the punctures were subcostal, apart from 3 cases where the punctures were supracostal.

The puncture was evaluated by:

A J-tipped 0.038 Teflon guidewire was inserted; then the exact length of the needle from the skin and the PCS was measured. The tract was dilated by using Amplatz Teflon dilators in 26 patients and telescopic metallic Alken dilators in 8 patients; a 30F Amplatz sheath was used in all patients (Table 2).

In our institution, we used the telescopic metallic Alken dilators routinely in all cases of fluoroscopy-guided PCNL. Hence, we began the first 8 cases in our study by using the Alken metallic dilators, but we shifted to the Teflon dilators in the remaining cases because we found difficulty in monitoring both the central metallic bar tip and the dilator tip simultaneously.

The dilation was monitored by:

Then a 26F Wolf rigid nephroscope was applied, and the stones were disintegrated using a pneumatic Swiss lithoclast followed by extraction of the fragments by grasping forceps.

A C-arm was available in the operating theater for any emergency need for fluoroscopy guidance of the maneuver. At the end of the procedure, US was performed to exclude the presence of residual significant fragments (>4 mm) that may have migrated to another calix during disintegration. We found significant fragments that had migrated to the upper calix in one patient and to the lower calix in another patient. For these two patients with migrated large fragments, a second US-guided caliceal puncture was performed and was successful in both cases, because aflexible nephroscope is not available in our institution (Table 2). Finally, a nephrostomy tube was fixed. The ureteral catheters were replaced by Double-J stents in two patients where perforation of the PCS occurred during dilation.

At the end of the procedure, US was performed to exclude the presence of any fluid collection, and chest radiography was performed for patients with supracostal puncture to exclude any pulmonary complications. All patients were assessed in the second day after surgery for residual stones by US and radiography of the KUB. The combination of US and KUB radiography could detect any residual fragments up to 2 mm that may have been missed by using KUB radiography alone. A patient was considered stone free if no stone fragments were detected or only very small gravels <4 mm were found.

Residual significant stones were detected in two patients who underwent shockwave lithotripsy. The nephrostomy tubes were removed 24 hours postoperatively; then the ureteral catheter was removed 24 hours later to allow good sealing of the nephrostomy tract and to avoid any urinary leakage. The two Double-J stents were removed 4 weeks postoperatively.

The procedure was evaluated for access success, complications in the form of organ injury, pulmonary complications (pneumothorax or hydrothorax), intraoperative bleeding (the need for blood transfusion), perforation, fluid collection, postoperative fever, stone clearance, and the need for auxiliary maneuver.

Results

Of the 34 patients, the stone involved the right system in 19 and the left side in 15. Stones were radiopaque in 26 and radiolucent in 8 patients. The size of the stone ranged from 20 to 30 mm in diameter (mean 24 mm). The degree of dilatation of the PCS was moderate in 25 cases and severe in 9 patients. Previous ipsilateral open surgeries for renal stones were recorded in seven patients (Table 1).

The access to the PCS was successful in all cases. A successful second puncture was applied in two patients because of the migration of significant fragments to the upper calix in one case and to lower calix in the other case. The mean operative time was 60 minutes (range 40–85 min), and the mean hospital stay was 1.4 days (range 1–3 d).

Access-related complications, such as bending of the guidewires, bleeding that necessitated blood transfusion and/or termination of the maneuver, visceral organ injury, intraperitoneal perforation and collection were not reported in any patients. Pulmonary complications (pneumothorax or hydrothorax) were not reported in any patients who underwent the supracostal approach; however, perforations of the PCS during tract dilation were detected in two patients with Alken metal dilators mostly because the US monitoring of the tip of the central metallic bar and the metal dilator at the same time was difficult. This perforation was managed conservatively by insertion of a 7F Double-J stent for 4 weeks.

Although a C-arm was available in the operating theater for any emergency need, we did not use it in any case.

Postoperative fever was detected in five patients, which was controlled by parenteral administration of antibiotic and antipyretic agents within 3 days.

Thirty-two (94%) patients were stone free on postoperative day 2 without any fragments seen in the KUB radiography or US; residual stones that measured 8 and 10 mm were detected in two patients. The two residual stones were located in the renal pelvis at the time of SWL. Perhaps these stones were missed because only US was used intraoperatively. For these two patients, SWL was applied on the second day after the removal of the nephrostomy tube, and the patients became stone free 10 days postoperatively.

Discussion

Successful puncture of the PCS is the most important step for the success of PCNL. Frequent exposure to radiation carries the risk of complications for all the medical team with its bad effects on the thyroid, gonads, bone marrow, and eye lens. ⁵ Moreover, Loree and colleagues ⁶ stated that some molecular changes in animal tissues induced by fluoroscopy are possibly carcinogenic. Radiation exposure may also cause genetic mutation ⁷ ; thus, the need for alternative guidance for PCNL is aroused. Successful access to PCS was 100% in our series, and these results also were achieved by others. ^4,8 Basiri and associates ⁹ reported, however, 94% access success with US guidance because of the mild degree of hydronephrosis that was reported in one third of their patients but was excluded from our study. Another factor that allows the success rate of the puncture to be 100% is the use of saline infusion during the puncture, which allows continuous distension of the PCS. The same method also was reported by Etemadian and coworkers. ¹⁰

The use of US with a needle-guided system is very important to achieve success and for the puncture of the most convex point of the desired calyx. Desai ¹¹ reported that US-guided access is best performed with a needle guide, because the dotted line allows reaching the desired calix in am accurate way plus monitoring the depth of the puncture. Also, he reported that US-guided access without using a needle-guide system is suboptimal. ¹¹

We approach the PCS through the most convex point to avoid any vascular injury, and as a result of this approach, there was no intraoperative bleeding. The approach through the cup of the desired calix also was reported by Osman and associates ³ and Karami and colleagues ¹² to traverse minimal cortical tissue and to avoid injury of any major intrarenal vessels.

Osman and coworkers ³ and Desai ¹¹ reported that the US-guided approach must be performed by an urologist experienced in using US, as was done in our series.

We reported two (5.9%) cases of perforation of the PCS during dilation by the metal dilators because of difficulty in monitoring the metal dilator and the tip of the central metallic bar at the same time. Therefore, we recommend the use of Teflon Amplatz dilators, because no perforation was detected in our series. Hosseini and colleagues ⁴ reported perforation in four (8.51%) patients by Teflon dilators, although they operated on single stone pelvis only, similar to our series, mostly because of bigger stone size (range 24–46 mm) and lower degree of PCS dilatation (mild to moderate degree of hydronephrosis). Although balloon dilation carries the advantage of single-step dilation, its dye inflation cannot be monitored except under fluoroscopy.

Zhou and associates, ¹³ in their series of 92 patients, reported the need for a second tract in 22.8%, which is a higher rate than ours. This is because multiple stones and staghorn stones constitute about two-thirds of their cases. We needed a second tract in only two (5.8%) patients. The second tract was successfully accomplished in our series without any difficulty when it is compared with those that were performed under fluoroscopy guidance and were associated with dye extravasation.

A C-arm was available in the operatiing theater, but we did not use it in any case; this also was reported by others. ⁸ In another study of US-guided PCNL, however, it was needed in 2 of 47 cases. ⁴ Although we did not use the C-arm in our series because of our restriction criteria, we recommend its availability in the operating theater for any emergency need during the operation. ¹⁴

Eight cases of radiolucent stones were included in our study, and all were managed successfully. This represents one of the advantages of US-guided PCNL, and this was also reported by Hosseini and coworkers. ⁴

The need for auxiliary procedures was 6% in our study. Hosseini and associates ⁴ also reported a rate of about 6.4%, but their patients took about 4 weeks longer than ours to reach a 100% stone-free rate because of the bigger size of their stones. Osman and colleagues ³ reported a 33% need for auxiliary measures after the initial PCNL (in the form of SWL, second PCNL, and ureteroscopy) because most of their stones were partial staghorn stones. In our series, we applied this procedure for single stone pelvis only.

Basiri and coworkers ⁸ reported that there were no major intraoperative or postoperative complications. None of their patients was subjected to any visceral injuries mostly because any organ in the path of the puncture can be seen on US. ¹⁵ Only five patients needed blood transfusion, all of whom had calculi larger than 700 mm². Similar results were reported in our study, except that no bleeding or blood transfusions were reported because of the smaller size of the stones in our series (less than 30 mm).

US-guided PCNL carries many advantages, such as the high success rate of the second puncture, the detection and monitoring of both radiolucent and radiopaque stones intraoperatively, the elimination of radiation exposure, and the ability to see any organ in the path of the puncture. Moreover, the operator and the medical team will be able to get rid of all the radiation protection devices (the lead aprons, the protective eye glasses, and the thyroid shield) to allow them to work easily. ¹⁶

The following factors are crucial for the success of solo US-guided PCNL: The stone size (less than 3 cm), the degree of hydronephrosis (moderate and severe), the pelvic location of the stone, the use of US with a needle-guided system to avoid entering the PCS from any point rather than the most convex point that is coincident with the caliceal fornix (least vascular point), and an experienced urologist.

Well-dilated PCS with single calculus is found only in a small percentage of patients worldwide; however, stones are endemic in our locality, so those patients represent a big percentage of our patients.

According to our exclusion criteria, our technique will not be applicable for all cases of renal stones. Because our technique must be performed by an experienced urologist only, therefore we advise the junior urologist to be trained well on renal US or alternatively to be trained on biologic models like that described by Hacker and coworkers. ¹⁷

Conclusion

Solo US-guided PCNL can be performed safely and radiation free with little complication in selected cases (single stone pelvis, less than 3 cm in diameter, and moderate to marked hydronephrosis) with an urologist experienced in using a US needle-guided system.