Ultrasound-guided paravertebral nerve block anesthesia for percutaneous endoscopic laser unroofing treatment of symptomatic simple renal cysts-An innovative ambulatory surgery mode

Ji Hu,Yun Zhng,Yong Liu,Xio Yu,Shogng Wng

a Department of Urology,Tongji Hospital,Tongji Medical College,Huazhong University of Science and Technology,Wuhan,China

b Department of Anesthesiology,Tongji Hospital,Tongji Medical College,Huazhong University of Science and Technology,Wuhan,China

KEYWORDS Paravertebral nerve block anesthesia;Percutaneous puncture;Simple renal cyst;Unroofing;Ambulatory surgery

Abstract Objective: This study was designed to evaluate the feasibility,efficacy,and safety of percutaneous ureteroscopy laser unroofing as an ambulatory surgery for symptomatic simple renal cysts under multilevel paravertebral nerve block anesthesia.Methods: From December 2015 to September 2017,33 simple renal cyst patients who had surgical indications were enrolled.Under ultrasound guidance,the T10/T11,T11/T12,and T12/L1 paravertebral spaces were identified,and 7-10 mL 0.5% ropivacaine was injected at each segment.Then a puncture needle was placed inside the cyst cavity under ultrasonic monitoring.A guidewire was introduced followed by sequential dilation up to 28/30 Fr.The extra parenchymal portion of the cyst wall was dissociated and incised using a thulium laser,and a pathological examination was performed.Results: Sensory loss to pinprick from T8 to L1 and sensory loss to ice from T6 to L2 were observed in all patients.None of the patients complained of pain during surgery.No serious complications occurred perioperatively.After the surgery,all patients recovered their lower limb muscle strength quickly,got out of bed,resumed oral feeding,and left the hospital within 24 h of admission.The pathologic diagnosis of all cyst walls was a simple renal cyst.The mean follow-up was 35.8 months.At the end of follow-up,the cyst units were reduced in size by more than 50% compared to the preoperative size,and no patient experienced a recurrence.Conclusion: Multi-level paravertebral nerve block for percutaneous ureteroscopy laser unroofing as an ambulatory surgery mode is feasible,safe,and effective for the treatment of simple renal cysts in selected patients.

1.Introduction

The prevalence of simple renal cyst detected by ultrasonography in the general population has been reported from 4.2% to 32.6% [1,2].Renal cysts are more common in men and elderly individuals and are associated with increased level of serum creatinine and diabetes [3].Most simple renal cysts are asymptomatic and do not require treatment[4].However,when the diameter of the cyst is more than 5 cm and renal parenchyma compression is present,surgical intervention is required [5].Several surgical treatments have been described for simple renal cysts,including cyst aspiration [6],sclerotherapy [7]with a variety of different agents,and surgical resection[8].Laparoscopic approaches to cyst unroofing have shown good results and are considered the gold standard [9].Unfortunately,general anesthesia (GA) and a three-port approach not only extend the recovery time and increase hospital costs for patients,but also are not optimal minimally invasive treatments.

Percutaneous endoscopic laser unroofing (PCELU) is a feasible innovation explored by our center to treat simple renal cysts.It can be performed with only one port and under regional anesthesia to obtain satisfactory surgical results [10].To enable the patients who undergo this operation to recover more quickly and save time and the costs of hospitalization,we aimed to improve the method of anesthesia.Paravertebral block (PVB) is an alternative regional anesthesia option and provides effective postoperative analgesia after many urological procedures [11].It has many advantages,such as a lower dosage of anesthetic,more stable hemodynamics,and improved pulmonary function,due to localized nerve blocking within the paravertebral space [12].Recently,with careful planning and use of ultrasound guidance,PVB has achieved adequate somatic and visceral sensory blockade to meet the anesthetic needs for percutaneous nephrolithotomy (PCNL) in our center [13,14].

In this study,we evaluated the feasibility,efficacy,and safety of PCELU as an ambulatory surgery mode for the treatment of symptomatic simple renal cysts under PVB anesthesia.

2.Patients and methods

2.1.Patients

This present study was approved by the Ethical (Helsinki)Committee of Tongji Hospital of Tongji Medical College of Huazhong University of Science and Technology (TJC20151105).All the study participants provided written informed consents.All the methods were carried out in accordance with the relevant guidelines and regulations.From December 2015 to September 2017,33 patients who had surgical indications or symptomatic simple renal cysts were evaluated via abdominal ultrasonography and contrast-enhanced CT.All patients were assessed according to the Bosniak Classification system[15],and 30 patients had Class I and three had Class II cyst lesions.

Patients with a local anesthetic allergy,coagulopathy,or complex cystic kidney disease were excluded from this study,as were patients with an American Society of Anesthesiologists physical status scores Ⅳ-V.Of the 33 patients,24 complained of flank pain and mild abdominal bloating or aching,and their mean pain visual analog scale(VAS)score was 4.1(standard deviation[SD]1.1).The other patients were asymptomatic and were found to have a renal cyst on a routine imaging examination.There were nine patients in whom the cysts were in the upper pole,17 in the middle pole,and seven in the lower pole.The mean diameter of the cysts was 6.1 (range: 5.3-8.7) cm.

The operative procedure,the possible complications,and the invasiveness of the procedure were carefully explained to each patient.Additionally,alternative treatment methods,such as the laparoscopic unroofing procedure,were also described to the patients.They were actively involved in the decision-making process,and the preferred treatment option was chosen by each patient.The characteristics of the patients are given in Table 1.All patients were admitted on the morning of the surgery day after completing related examinations in the outpatient department.

Table 1 Patient characteristics.

2.2.Anesthetic technique

All patients underwent ultrasound-guided PVB anesthesia.All procedures were performed by experienced anesthetists.On arrival at the operating room,the patient was first placed in a supine position.Standard intraoperative monitoring with electrocardiography,pulse oximetry,and noninvasive blood pressure measurement was performed.Hydromorphone 1-2 mg was administered intravenously 10 min prior to the nerve block for the patient comfort during the puncture.Then the patients were turned to a lateral position with the side to be operated facing upward.Oxygen was provided by facemasks at 5 L/min.Multisegment PVB was performed as previously described [13].

Figure 1 The procedures for ultrasound-guided paravertebral block anesthesia.(A) The levels of nerve block planned for patients were T10/T11,T11/T12,and T12/L1,respectively,and the linear array ultrasound 5-to 10-MHz probe was rotated to the sagittal plane;(B) The transverse processes of T11 and T12 were in the same visual field,and the superior costotransverse ligament and pleura were identified(the blue area);(C) A 100-mm,21-gauge Tuohy needle (arrow)was introduced into superior costotransverse ligament under direct visualization of the needle tip;(D) Sensory loss to pinprick from T8 to L2 and sensory loss to ice from T6 to L2 were evaluated in all patients 20 min after administration of block.

The levels of the nerve blocks planned for all patients were T10/T11,T11/T12,and T12/L1 (Fig.1A).Ultrasound-guided PVB was performed using a linear array ultrasound 5-to 10-MHz probe.The probe was positioned parallel to the rib through the lumbar back.With the probe being moved cephalad or caudad,the transverse process of T10 to L1 was identified(Fig.1B).The T10/T11,T11/T12,and T12/L1 paravertebral spaces of the patients were selected for injection under ultrasound guidance.After infiltrating 2% lignocaine,a 100 mm,21-gauge Tuohy needle (Epineed,Terumo Co.,Tokyo,Japan) was induced 2.5 cm lateral to the spinous process and then advanced perpendicularly until it made contact with the transverse process.Then the needle was redirected and walked off the upper end of the transverse process,advancing approximately 1 cm into the paravertebral space (Fig.1C).A total of 7-10 mL 0.5% ropivacaine was injected into each segment.Twenty minutes after administration of the block,sensory loss to pinprick from T8 to L2 and sensory loss to ice from T6 to L2 were evaluated for each patient(Fig.1D).

2.3.Surgical technique

PCELU was performed as previously described [10].Briefly,patients were placed in the prone position for percutaneous puncture and tract dilation after the PVB was finished.Under ultrasound guidance,the cyst was identified,and an eighteen-gauge access needle was placed inside the cyst cavity (Fig.2A).A guidewire was introduced into the cyst cavity,followed by tract dilation with fascial dilators in a sequential fashion up to 28/30 Fr.Finally,a 28/30 Fr Amplazt sheath (Cook Medical Holdings LLC,Bloomington,IN,USA) was placed inside the cyst cavity (Fig.2B).An 8/9.8 Fr rigid ureteroscope (Karl Storz,Tuttlingen,Germany)connected to a normal saline irrigant was inserted through the Amplazt access sheath and advanced into the cyst cavity (Fig.2C).Then both the Amplazt sheath and ureteroscope were returned to the exterior of the cyst until they reached a proper plane between the extra parenchymal portion of the cyst wall and the surrounding perirenal adipose tissue (Fig.2D).The exterior cyst wall was dissociated from the perirenal adipose tissue with an ureteroscope and the irrigation pump pressure(150-250 mmHg).A portion of the collapsed cyst wall was gently pulled toward the Amplazt sheath interior and incised as much as possible with a thulium laser (Vela? XL power 40-50 W,continuous wave mode) (Fig.2E).The dilated 28/30 Fr tract can hold the rigid ureteroscope(thulium laser),guidewire,and endoscopic gripper at the same time within the Amplazt sheath to incise the cyst wall more efficiently and avoid mutual interference between the instruments during the operation.Finally,a 22 Fr nephrostomy tube was placed after the procedure,and the cystic fluid and cyst wall tissue were sent for cytological and histopathologic analysis (Fig.2F).

3.Results

The efficiency of PVB was assessed 20 min after the administration of the block.Sensory loss to pinprick from T7 to L2 and sensory loss to ice from T7 to L2 were achieved in majority of patients (Table 2).No complications attributed to PVB,such as local anesthetic toxicity,vascular puncture,pneumothorax,or Horner syndrome,were encountered.Rescue analgesics were administered to none of the patients.

Figure 2 The procedures for percutaneous ureteroscopy laser unroofing treatment of simple renal cysts.(A) A needle(arrow)was introduced inside the cyst cavity under ultrasound guidance;(B) Using fascial dilators,a working channel was dilated in a sequential fashion up to 28/30 Fr,and a 28/30 Fr Amplazt sheath was placed inside the cyst cavity;(C) The interior cyst was observed with an 8/9.8 Fr rigid ureteroscope;(D) The sheath and the ureteroscope both returned to the exterior cyst,and then reached a proper plane between the extra-parenchymal portion of the cyst and perirenal adipose;(E) The exterior cyst wall was dissociated and grasped and pulled towards the Amplazt sheath interior,and then it was incised using a thulium laser;(F) The incised cyst wall tissue was sent for histopathologic analysis.

Table 2 Assessment of the sensory block level in patients 20 min after paravertebral block (n=33).

All patients were able to turn into the prone position by themselves without assistance after PVB.None of the patients complained of pain during the establishment of the percutaneous tract,dissociation and cutting of the cyst wall,or placement of the nephrostomy tubes.No additional opioids or nonsteroidal anti-inflammatory drugs were needed during the operation.None of the patients suffered dramatic fluctuations in mean arterial pressure or heart rate during the procedure.The mean operative time was 25.6(range:15-46)min.No serious complications occurred intraoperatively or postoperatively,such as active bleeding,urinary leakage,or injury of the renal parenchyma or adjacent organs.Three of these patients suffered mild pain according to the VAS 6 h after surgery and were rated as Clavien grading score 1,which requires nonsteroidal anti-inflammatory drug treatment.

After the surgery,all patients recovered their lower limb muscle strength quickly (10 patients were rated as Grade IV,and 23 patients were Grade III) and got out of bed,moved,and were able to consume food and drink orally.All of the patients met the discharge standards,had the nephrostomy tube removed,and left the hospital on the surgery day in the afternoon or in the morning on the day after surgery.The entire hospital stay was no more than 24 h.No patient needed oral analgesics when they were discharged.Cyst fluid cytology was negative for malignancy,and the histopathologic diagnosis of all cyst walls was consistent with a simple renal cyst.The mean VAS score of flank and abdominal pain at 5 h postoperatively was 2.3 (SD: 0.5),and the VAS scores were significantly improved compared with those before the operation(p＜0.05).

The patients were followed up at least every 6 months for the first year with an abdominal CT scan and annually by a routine physical examination thereafter with a CT scan or bilateral ultrasonography.One patient was reluctant to return to the hospital due to the benign nature of the disease and was lost to follow-up.The remaining 32 patients had at least one-year follow-up with a mean of 35.8(range:30.0-48.0) months.Twenty-six cyst units (81.2%) were completely resolved with almost 100% disappearance of the cyst,and six cyst units(18.8%)were reduced in size by more than 50% compared to the preoperative size (Fig.3).No patients had cyst recurrence during the follow-up period.

4.Discussion

Enhanced recovery after surgery re-examines traditional practices,creating a multimodal approach of patient-centered perioperative pathways designed to reduce hospitalization without increasing the rate of complications or readmissions[16].It is accompanied by surgery performed in ambulatory settings,which has increased exponentially due to advances in surgical and anesthetic techniques and perioperative care [17,18].Enhanced recovery after surgery has become an important focus of perioperative management in many types of surgeries,including general surgery [19],orthopedics [20],and gynecologic oncological surgery [21].Cystectomy is the most common enhanced recovery after surgery pathway performed in urology,due to a reduction in the rate of complications and the length of stay [22-24].However,reported data about the development of ambulatory surgery programs in urologic diseases are limited.

Antegrade PCELU to treat simple renal cysts is a novel approach explored by our center [10].It only requires a single incision and can achieve a high surgical efficiency similar to the laparoscopic approach.Our previous study demonstrated that the cyst volume shrank by more than 50% compared to the preoperative volume in 95.8% of the patients [10].The recurrence rate was 4.2% during a mean follow-up of almost 1 year,compared to 4.5%-5.0% after the laparoscopic approach reported by other study [25].

With the continuous improvement of this technology,we achieved a very low recurrence rate and high safety in this study (no recurrence occurred during follow-up).The most critical steps in this technology are the identification and dissociation of the exterior cyst wall.When the cyst was punctured and dilated by the operator,its volume was reduced and it collapsed.Then the assistant kept the guidewire inside the cyst cavity at all times(Fig.2D),while the sheath and ureteroscope were backed into the exterior cyst by the operator.A trans-interfascial plane between the perirenal adipose tissue and the exterior cyst wall could be identified (Fig.2D).If the right plane could not be found due to poor visualization,puncture bleeding,or other reasons,the ureteroscope might be re-entered into the cyst cavity through the guidewire and the above process could be tried again.In our opinion,the best puncture spot is the center of the cyst wall.The method of complete dissociation is the puncture spot as the center,with outward expansion of the layers by using a ureteroscope and a hydrodissection technique until near the normal renal parenchyma.During the operation,gentle action and resection of the cyst wall should be ensured.In our study,no patient had renal parenchyma or surrounding organ damage.It is crucial to select the proper patients.According to our experience,patients with a solitary,larger posterior renal cyst possess an appropriate puncture route and are considered ideal surgical candidates.Patients with an anterior cyst are not recommended to undergo this procedure due to the limited ability to achieve dissociation and resection,causing high postoperative recurrence rates[10].Our viewpoint is also supported by the study of Chen et al.[26].

The surgical technique has been improved for the treatment of simple renal cysts.Anesthesia also needs to be improved,and effective perioperative analgesia is the foundation of quick postoperative recovery [16].In our previous study [10],we performed regional anesthesia,mainly with continuous epidural anesthesia instead of GA in this operation,which reduced the average length of stay compared with the laparoscopic approach and decreased the average hospitalization costs.In this study,we further explored a faster postoperative recovery for the patients and were able to convert this technique into ambulatory surgery using multiple segment PVB.As highly localized pain management,PVB has been widely used for postoperative analgesia or assistance with GA for kidney area surgery,such as PCNL and laparoscopic nephrectomy[27,28].However,limited literature has documented its use as the only anesthesia covering the kidney area during surgery.It is worth mentioning that we have accumulated experience in multiple segment injections of PVB as perioperative analgesia for PCNL [13,14];therefore,the same principles also apply for PCELU theoretically.Anatomically,the achievement of adequate analgesia for percutaneous nephro-ureteroscopy requires blockage of both of the somatic nerves that innervate the skin and muscle tissue and the visceral nerves that innervate the kidney and the upper ureters.The surgery tract is typically established in the 11th to 12th intercostal space [29].Sensory nerves in this area are readily blocked by thoracic PVB.Renal pain is thought to be transmitted via nerves originating from T10 to L1.The upper ureter is innervated by nerves originating from T10 to L2[30].Based on this anatomical knowledge,a complete blockade of unilateral spinal nerves from T10 to L2 can provide sufficient analgesia.

Technically,our study has shown that multiple segment injections of PVB fully meet the needs of surgery.More importantly,preoperative PVB reduced intraoperative and postoperative opioid consumption,postoperative pain,and the need for antiemetics.The reduction in opioid consumption decreases both the costs and the incidence of postoperative nausea and vomiting compared with GA[31,32].In addition,PVB can reduce postoperative intestinal paralysis and retain the patient’s muscular strength in the lower limbs[33],which leads to an early resumption of oral feeding and ambulation after surgery and accelerates their recovery compared with continuous epidural anesthesia.In our study,all patients were hospitalized for no more than 24 h and had no anesthetic-related complications during the follow-up period,which met the requirements of ambulatory surgery.

What needs to be acknowledged is that there are difficulties in more obese patients,such as finding the paravertebral space to perform anesthesia,and the scope of ureteroscopic movement is limited during dissociation of the exterior cyst wall even with the longer sheath.It is also difficult to reach a proper plane between the extra parenchymal portion of the cyst wall and the surrounding perirenal adipose tissue in patients with an inflammatory cyst.In addition,we recognize that there is undoubtedly a learning curve associated with the paravertebral technique,which is currently an uncommon anesthesia procedure,but it is easy to master for anesthesiologists based on the experience of our center,and we believe this is similar to learning curves for any other new regional anesthetic technique.

Other limitations to this study include its nature as a single-center retrospective analysis and the relatively small sample size.Further research is needed to validate this result through a multicenter,randomized,prospective study with a large sample.

5.Conclusion

We here shed new light that ultrasound-guided multi-level PVB for PCELU as an innovative ambulatory surgery mode is feasible,safe,and effective for the treatment of symptomatic solitary,larger posterior,non-inflammatory simple renal cysts,especially for patients who are moderate in size,not obese,and have a risk of postoperative complications following general or neuraxial anesthesia.By using this mode,it could not only save the time and costs of hospitalization,but also improve their satisfaction.

Author contributions

Study concept and design: Shaogang Wang,Jia Hu.

Surgery procedures: Shaogang Wang,Jia Hu,Xiao Yu.

Anesthesia procedures: Yong Liu.

Data acquisition: Jia Hu,Yuan Zhang.

Data analysis: Jia Hu,Yuan Zhang.

Drafting of manuscript: Jia Hu.

Critical revision of the manuscript: Shaogang Wang.

Conflicts of interest

The authors declare no conflict of interest.

Acknowledgments

We thank Prof.Jihong Liu and Prof.Zhangqun Ye (Department of Urology,Tongji Hospital,Tongji Medical College,Huazhong University of Science and Technology,Wuhan,China)for critical reading of the paper prior to submission.