Division of Urology, Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
ABSTRACT
INTRODUCTION
Urolithiasis is a major public health problem in Northeastern and Northern Thailand. It can cause flank pain, nausea, pain when urinating, bloody urine, and urinary tract infection. In a study from 2020, urolithiasis was found mostly in middle-aged and the elderly between 50-69.1 The highest incidence of urolithiasis in Thailand is in the Northeast of the country, accounting for 16.9% of all cases.2
Although there is no clear definition, staghorn stones commonly refer to stones with more than one branching of the collecting system that may divide completely or partially depending on the level of occupancy.3,4 Staghorn stones are often associated with infection or metabolic abnormalities, and can lead to obstruction, kidney loss, sepsis, and death if left untreated.5,6
According to AUA and EAU guidelines, since percutaneous nephrolithotomy (PCNL) provides a higher
Corresponding author: Ekkarin Chotikawanich E-mail: ekkarinc@yahoo.com
Received 27 February 2023 Revised 14 March 2023 Accepted 23 March 2023 ORCID ID:http://orcid.org/0000-0003-3914-2770 https://doi.org/10.33192/smj.v75i5.261510
All material is licensed under terms of the Creative Commons Attribution 4.0 International (CC-BY-NC-ND 4.0) license unless otherwise stated.
stone-free rate than Shockwave Lithotripsy (SWL) or Ureteroscopy (URS), PCNL is considered as first-line therapy for symptomatic patients who have a stone burden >20 mm.7,8
Open surgery or laparoscopic/robotic-assisted procedures are alternative modalities with a good stone- free rate.3 However, some patients are not suited for this treatment or may prefer less invasive procedures. Hence, we attempted to find other modalities that could provide a stone-free rate (SFR) similar to PCNL, with a lower incidence of complications and reduced hospitalizations. We found many studies with retrograde intrarenal surgery (RIRS) in larger stones (>20 mm), with higher stone-free rates and fewer complications than PCNL due to well-developed instruments, such as the flexibility or size of the endoscope, accessory equipment, and techniques.9 Therefore, we aimed to study the safety and efficacy of the retrograde endoscopic technique in
patients with staghorn stones treated at our hospital.
MATERIALS AND METHODS
This was a retrospective observational study. At our institute, we performed retrograde intrarenal surgery in staghorn stone patients in May 2016. After the study was approved by the Ethics Committee (COA no. Si 153/2022), medical records of all patients with staghorn stones treated by RIRS in the database of our tertiary referral university hospital from May 2016 to October 2020 was reviewed. We excluded a complete staghorn stone, patients under 18 or those who had received other modalities in their first attempt such as PCNL, SWL, and open surgery, and those who denied treatment, had incomplete data, and patients who failed to follow-up. In total, we had 35 patients who underwent RIRS as their first lithotripsy attempt and were eligible for this study. Patients who possessed staghorn stones in both kidneys were considered as two subjects with a stone in each kidney. However, patients who had a non-staghorn stone on the contralateral side were counted as one subject.
The size of the stones, maximum, and mean of the Hounsfield Units (HU) were measured using the same “DICOM viewer” program and the same observer in all patients. In X-ray results, we used the widest diameter. In computerized tomography (CT) results, we used the largest diameter from both coronal and axial views.
The operative notes and techniques were reviewed, including ureteral access sheath size and fluoroscopy time. Estimated blood loss and operative time was collected by reviewing the anesthesiologist’s record, and the complications, both immediate and delayed were recorded by reviewing IPD charts, operative notes, and
OPD records up to a maximum of 6 months after the latest procedure. The glomerular filtration rate (GFR) was obtained in the same visit or at least two weeks before every operation.
Currently, intraoperative and postoperative complications are commonly classified according to modified Satava and modified Clavien classification systems.10-16 In our research, post-operative problems were categorized into four groups: fever, sepsis, others, and no complications summarized by the modified Clavien classification system. We defined sepsis according to the positive hemoculture result. To classify peri- operative complications, we employed the modified Satava classification system. However, we still specified specific complications along with classification grading to obtain a clear perspective.
There were three urologists involved in our project. After general anesthesia, cystoscopy, sheath 22Fr, and 30-degree lens were used in all cases. Hydrophilic tip wire was passed inside to the renal pelvis under a fluorograph. A double-lumen catheter was replaced over the guidewire, and the super-stiff guidewire was inserted into the hole of the catheter. Ureteral access sheath, 11/13Fr or 12/14Fr, replaced the catheter over the stiff wire. Afterwards, a flexible video ureteroscope URF-V – Olympus was inserted. Renal stones were identified and disintegrated with Ho-YAG laser setting 1J 20Hz. A retrograde pyelogram was performed, and a DJ stent inserted.
After the operation, stone analysis was carried out using the Fourier transform infrared spectroscopy (FTIR) technique at our institute after authorization by nephrologists. The maximum compound from stone analysis was used to represent the etiology of the stone of the patient.
Stone-free was defined as no residual stone or a stone fragment less than 2 mm on a standard radiograph, CT scan, or sonography (depending on the type of stone) at a maximum of six-month follow-up after the latest procedure. The remaining stones were categorized into a lower pole and a non-lower pole.
The data was divided into four parts as follows: patient data including gender, age, race, underlying disease, medication, glomerular filtration rate, hydronephrosis, and previous treatment history. Surgical data included operative time, blood loss during surgery, size of access sheath used, perioperative complications, and fluoroscopy time. Post-surgery data included number of procedures performed, post-operative complications, glomerular filtration rate, and post-treatment stone-free rate. Last but not least, stone data included size, type, location,
opacity, Hounsfield Units, and stone analysis.
Descriptive statistics were used to characterize populations. Qualitative variables such as gender was presented as frequency and percentage. Quantitative variables such as age, size, and Hounsfield Units, which are non-normal distributions of continuous data, were represented by the median and min-max or IQR values. The frequency of stone-free rates and complications were reported as number and percentage. Unfortunately, the number of patients was limited, so we were unable to analyze the statistic module.
RESULTS
A total of 36 participants in the study were divided into 12 men, and 23 women, with a median age of 63 (IQR 56-73). The underlying medical conditions were as follows: hypertension, 25 people (71.43%), hyperlipidemia,
19 people (54.29%), diabetes, 15 people (42.86%), chronic kidney disease, nine people (25.71%), any type of cancer, two people (5.71%), and no underlying disease, four people (11.43%), respectively.
The median size of all staghorn stones was 3.1 cm, with a range from 1.5-7.16 cm, and 10 people had it on the right and 25 on the left side. The median of maximum Hounsfield Units was 1226 HU (IQR 813- 1661) and the median of the mean of Hounsfield Units
was 950 HU (IQR 584-1332). Twelve subjects (34.29%) had radiopaque stones and 21 (60%) had radiolucent stones, and the remainder were unspecified (5.71%). In total, 13 people had hydronephrosis (37.14%). The demographic data is shown in Table 1.
In this study, we divided stones into three main types: calcium, non-calcium stones, and uric stones. The most common type were calcium-based stones, accounting for 18 (51.4%), followed by nine uric stones (25.7%), five non-calcium stones (14.3%), and three uncategorized stones (8.6%).
The peri-operative and post-operative outcomes are shown in Table 2. The stone-free rate was 31.43%, and 59.55% after the first and second procedures, respectively. The stone-free rate did not increase after the second procedure.
For the operation, we used ureteral access sheaths size 11/13Fr or 12/14Fr in almost all cases. The median operative time was 80 minutes for the first procedure, 60 minutes for the second, 35 minutes for the third, and 90 minutes for the fourth procedure, with an estimated blood loss of less than 30 ml in each session, except for patients who switched to PCNL.
A total of 10 patients were pre-stented for RIRS due to a narrowed or swollen ureter, and inability to access the stones. Nine underwent pre-stenting before the first
TABLE 1. Demographic data.
Sex male (n,%) | 12 | 34.3% |
Sex female (n,%) | 23 | 65.7% |
Age (Median, IQR) | 63 | 56.0-73.0 |
DM (n,%) | 15 | 42.9% |
HT (n,%) | 25 | 71.4% |
DLP (n,%) | 19 | 54.3% |
CA (n,%) | 2 | 5.7% |
CKD (n,%) | 9 | 25.7% |
no U/D (n,%) | 4 | 11.4% |
Lt. staghorn | 25 | 71.4% |
Rt. Staghorn | 10 | 28.6% |
CT size (Median, Min-Max) | 3.1 | 1.5-7.16 |
HU max (Median, IQR) | 1226.0 | 813.0-1661.0 |
HU mean (Median, IQR) | 950.0 | 584.0-1332.0 |
Hydronephrosis (n,%) | 13 | 37.1% |
TABLE 2. Perioperative outcomes.
1st Operation 2nd Operation 3rd Operation 4th Operation | |||||||||
Frequency | Percent | Frequency | Percent | Frequency | Percent | Frequency | Percent | ||
Patients (N) | 35 | 100.0% | 15 | 100.0% | 3 | 100.0% | 1 | 100.0% | |
Cumulative SFR | 11 | 31.4% | 9 | 59.6% | 0 | 59.6% | 0 | 59.6% | |
Operative time (Median, IQR) | 80 | 60.0-120.0 | 60 | 35.0-85.0 | 35 | 20.0-35.0 | 90 | 90.0-90.0 | |
Overall complication | 8 | 22.9% | 3 | 20.0% | 0 | 0.0% | 0 | 0.0% | |
Fever | 3 | 8.6% | 3 | 20.0% | 0 | 0.0% | 0 | 0.0% | |
Sepsis | 2 | 5.7% | 0 | 0.0% | 0 | 0.0% | 0 | 0.0% | |
Injury | 2 | 5.7% | 0 | 0.0% | 0 | 0.0% | 0 | 0.0% | |
IRS | Other complication | 1 | 2.9% | 0 | 0.0% | 0 | 0.0% | 0 | 0.0% |
R | No complication | 28 | 80.0% | 12 | 80.0% | 3 | 100.0% | 1 | 100.0% |
RIRS session and one patient before the second RIRS session. Intra-operative problems of this step were seen in two subjects with a ureteral injury, which falls under Grade 1 of the modified Satava classification system. Meanwhile, the patient had a low-grade fever during post-operative problems. All cases resolved after stenting and routine post operative care.
We had a total of 35 patients who underwent RIRS as the first step. Grade 1 and 3A complications of the modified Clavien classification were noted in four and two patients respectively. Two patients had a fever, two were septic, one had acute urinary retention, and one had both ureteral injury and fever. The remaining 28 patients had no complications. One patient also had pure ureteral injury, not including the other patient mentioned before, accounting for Grade 1 of the modified Satava classification system. All patients recovered after conservative treatment. The stone-free success rate of the first procedure was 31.43% (11 patients). The remaining stones were found in the lower pole accounting for 95.83% (23 patients) and in the non-lower pole location for 29.17% (7 patients). In some cases, there was more than one location of the remaining stone.
During the second procedure, six patients stopped operative management, with three switching to medical treatment, and two failing to follow-up. The remaining stones were all lower pole stones characterized by four
calcium base stones, one uric, and one unknown type. The size was about 0.8-2.5 cm. The remaining 18 patients in this group were divided into two subgroups, including three patients who underwent PCNL and 15 who underwent RIRS. In the RIRS group, we found three patients that had a fever (Grade 1 of modified Clavien), however, the other 12 had no complications. The stone-free rate was 60.00% (9 out of 15 patients) for this procedure and the cumulative stone-free rate for the RIRS group was 59.55%. Since some patients had more than one site of remaining stones, they were in both the lower pole and non-lower pole group for three patients (50%) and three patients (50%) in the lower pole group. In terms of complications, we found two patients with fever, while the other patient had a serious bleeding complication and required transfusion, which falls under Grade 1 and 2 of the modified Clavien classification. Also, PCNL did not improve the stone-free rate in the second procedure. Remaining stones from PCNL were found in the lower pole of all three patients, accounting for 100%.
In the third and fourth procedures, we had only five patients in both groups, and we didn’t notice any complications and the stone-free rate did not increase significantly. We found only one patient who was stone- free from PCNL in the third procedure. It was difficult to use statistical methods and percentage reports in these groups because the population was too small.
In summary, a total of four patients underwent PCNL due to stone burden. The number of patients in this group was too small to conclude and justify the stone-free rate and surgical complications for PCNL. However, in these cases, three patients had an estimated blood loss of 250, 300, and 600 ml, respectively, but only one person required a transfusion. The estimated blood loss in the PCNL group tended to be higher than RIRS. The operative time was more than 120 minutes in most cases, which is higher than the average of RIRS as mentioned above.
DISCUSSION
Percutaneous kidney stone surgery is considered by both the American Urological Association (AUA) and European Association of Urology (EAU) as first- line therapy for kidney stones over two centimeters in size and branching calculi, with a single-stage rate of 83%-95% stone-free.7,8 The indication for PCNL includes many factors such as stone size, stone location, patient, and stone composition, all of which affect the surgeon’s decision. Stones larger than 2 cm, staghorn stones, and lower pole stones more than 1 cm are not suitable for SWL. Meanwhile, obese patients or patients with distal obstruction preventing the passage of stone fragments are suitable for PCNL. The stone composition and hardness are also factors to be concerned about. For example, the PCNL method is preferred to treat cystine stones.3,7,8
Although we already have past data on stone-free rates, data on complications was lacking. In the past, there was no definitive criteria for PCNL complications. The decision was made by the surgeon who reported on complications, and mostly focused on intraoperative periods making it difficult to compare the actual complications of PNCL. Data on PCNL complications from multiple studies revealed that a lack of standardized reporting led to a large disparity in outcomes of grading complications, which explains the wide incidence range of 20% to 83%.17-23 Fortunately, nowadays, the severity of PCNL complications is classified using the modified Clavien classification system, which allows for more standardized storage of the complications.10,11,16 Consequently, the data collection process revealed that complications under this system decreased from the previous incidence, however, serious complications remained.
The contraindications for PCNL include pregnancy, bleeding disorders, and uncontrolled urinary tract infections. PCNL can cause many complications such as bleeding, infection, pneumothorax, hydrothorax, hemothorax, urinothorax, persistent nephrocutaneous fistula, rupture of the pelvicalyceal system, small bowel perforation, liver
injury, splenic injury, and colonic perforation. A mini- review by the Clinical Research of the Endourological Society (CROES) on the topic of “Complications associated with percutaneous nephrolithotomy” reported an overall complication rate of 21.5%. This was the result from an international multi-center study of 5,803 patients conducted across 96 centers in Europe, Asia, North America, South America, and Australia. They found that the complication rate reported by the modified Clavien system was as follows: no complications (79.5%), I (11.1%), II (5.3%), IIIa (2.3%), IIIb (1.3%), IVa (0.3%),
IVb (0.2%), and V (0.03%) respectively.17 The most common minor complication was transient fever, which is consistent with the results of our study. Major PCNL complications were grades III, IV, and V of the modified Clavien system and involved renal pelvis perforation, serious bleeding, severe infection, or adjacent organ injury as mentioned above.
While PCNL demonstrated a strong therapeutic effect, it is also riskier due to its invasiveness nature and some limitations.3,18,23 For instance, it has higher complication rates, increased risk of bleeding, and can lead to perioperative blood loss which may require transfusion, embolization, or in rare instances, nephrectomy leading to a lengthy hospital stay compared to RIRS. Moreover, the prone position is often preferred in PCNL procedures, but it requires significantly more effort by an anesthesiologist during operation. As the acceptable risk in each patient may be different, PCNL may not be feasible for every situation, so minimally invasive procedures such as RIRS is much more appealing in fragile patients.
In recent times, RIRS has received more attention and has been used in staghorn stone patients in a variety of research. RIRS yields a lower stone-free rate initially but is comparable to PCNL after several staged RIRS sessions. RIRS also has fewer complications and severity. Many studies showed a decent efficacy with an 83%-93% stone-free rate after three procedures and it is able to cover a large group of patients, including the high-risk as an alternative option to standard treatment.9,24-29
In our study, we present a single-center tertiary care series of RIRS for any staghorn stones. The treatment and follow-up data were obtained retrospectively. The stone-free rates in our institutions were only 31% during the first procedure, but this increased to 59.6% after the second procedure, respectively. Since the procedure was performed in patients contraindicated for PCNL and those with complicated cases in the tertiary care center, in combination with other factors such as the small sample size, the surgeon’s experience, and case selection methods, the stone-free rate may differ from
other studies. Additionally, thirteen patients who were in the non-stone-free group stopped the procedure and switched to medical treatment divided into six, five, and two patients from the first, second, and third procedures sequentially.
RIRS complications seem to be high when we calculate in percent due to a small sample size. However, in this study, there were no serious complications like those found in PCNL, such as injury to adjacent organs or bleeding that required transfusion. This study had 2 patients (6%) of grade IIIa complication which was septicemia, this figure was higher than an usual complication for RIRS which septic complication was 0.9%.30 This because of a small sample size as well as staghorn stone is at high risk of infection according to it is mostly infected stone and the surgery requires prolong operative time regards the stone size. PCNL is still considered as the first-line therapy for kidney stones over two centimeters with a favorable stone-free rate. But, in some patients with limitations such as uncorrectable coagulopathies, impaired renal function, single kidney, morbid obesity, severe obstructive pulmonary disease, postural contracture, or those who require treatment preserving renal parenchyma, RIRS is a good choice to reduce the likelihood of complications and have an acceptable stone-free rate in multistage RIRS.
A limitation of this study was that it was a single- center, non-randomized study with a small sample size, and post-operative imaging using plain x-ray may miss small residual stones. Also, the experience of surgeons in tertiary care services may differ. Due to these reasons, the obvious limitation is the reproducibility of the results. Nevertheless, a larger sample size undergoing RIRS with preferable outcomes and usefulness of our described technique will be reviewed.
CONCLUSION
Percutaneous nephrolithotomy (PCNL) is still considered the first-line therapy for kidney stones over two centimeters with a favorable stone-free rate. But, in some patients with limitations such as uncorrectable coagulopathies, impaired renal function, single kidney, and morbid obesity, RIRS is a good choice to reduce the likelihood of serious complications and have an acceptable stone-free rate. However, a prospective study should be performed to confirm these findings.
ACKNOWLEDGEMENTS
The authors gratefully acknowledge Ms. Julaporn Pooliam and Ms. Jitsiri Chaiyatho for assistance with statistical analysis.
There are no conflicts of interest to report. There are no sources of funding to disclose.
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