The feasibility and safety of one-shot dilatation compared to conventional sequential dilatation in tubeless percutaneous nephrolithotomy: a prospective randomized controlled study

Based on the previous work by Frattini et al. 2001 [4] where both types of dilatations were compared in a prospective randomised controlled study, the difference in post-operative decrease in haemoglobin level between the two groups was 0.36 ± 0.67 mg/dl. Using a power of 80 and 5% significance level we were needed to study at least 55 in each group. Sample size calculation was achieved using PS: Power and Sample Size Calculation Software Version 3.1.2 (Vanderbilt University, Nashville, Tennessee, USA).

A written and verbal consent was obtained from all patients included in this study, explaining the indication for the procedure, its possible risks and complications, and the potential benefits from the study.

This study was randomised by simple randomization using closed 150 envelopes, divided to two equal groups. Patients were divided into two groups; A & B, where group A included patients for One-Shot dilatation, while, group B, involved the patients for conventional serial Alken dilatation. A random envelope was picked before each case by the senior registrar and the operating surgeon was informed of the result. All adult patients scheduled for tubeless PCNL were admitted in Cairo University Hospitals, in the period from March 2020 till February 2021.

Patients between 18 and 60-year-old of both genders with clinical & radiological diagnosis of renal stone burden of more than 1.5 cm, or lower calyceal stones more than 1 cm. elected for Tubeless PCNL, were included in the study.

Patients who had nephrostomy placed at the end of the operation, renal impairment, multiple punctures done in the same operation, bleeding disorders, pregnancy, ectopic or malrotated kidney, skeletal deformities or ipsilateral renal tumour were excluded.

A detailed urological history taking and examination were done for all patients. Preoperative investigations including; complete blood count, coagulation profile, liver and kidney function tests, blood grouping, and urine culture and sensitivity were asked. Urinary tract infections were treated with antibiotics according to the urine culture. Pelvi-abdominal ultrasound, plain UT x-ray and non-enhanced CTUT were done to all patients. BMI (Body Mass Index) was calculated. Data regarding the stone site, size and density (in Hounsfield units) were noted as seen in the CT scan. Also, parenchymal thickness (between renal capsule and the targeted calyx) and skin to stone distance were measured in the CT scan by the radiologist, measuring it from the point of the largest stone diameter at a 45° angle from the horizontal line in the axial view using the Marosis view. Thirty minutes prior to anaesthetic induction, patient was given a single shot of antibiotic according to the urine culture and sensitivity test. Patients with asymptomatic bacteriuria or patients with negative urine culture were given intravenous cephalosporins.

After induction of anaesthesia, ureteric catheter was inserted using cystoscopy. The patient was then placed usually in prone position (supine position in some rare cases such as very obese and asthmatic cases whose prone position would compromise the ventilation parameters). A retrograde pyelogram was done to decide which calyx to puncture. The kidney was then punctured under fluoroscopic guidance carefully using an 18G puncture needle, then a J-tip guidewire was inserted through the needle. The puncture needle is removed and replaced with a reversed central Alken dilator with the smallest Alken dilator was placed over it, then the central Alken was removed to place a second ‘safety’ guidewire. The central Alken was placed over the ‘working’ guidewire then according to the dilatation method allocated, if serial dilatation was chosen, then conventional dilatation using telescopic metal Alken dilators (Karl Storz Telescopic bougie set 27090 A 9-24Fr Germany) was done. If One-Shot dilatation was chosen then a 30 Fr Amplatz dilator (30 Fr single use Amplatz dilator Boston Scientific with renal sheath M0062601120 USA) was placed over the central Alken and dilated carefully into the desired calyx with fluoroscopic guidance. Amplatz sheath was placed over the dilator. The nephroscope (Karl Storz nephroscope 27092 AMA, 19 cm with sheath 27093 CD 24Fr Germany) was then introduced to confirm successful intra-renal access and to view the stone(s), which was then dealt with accordingly. At the end of the procedure, all guide wires and access sheath were removed and the wound was sutured. Ureteric stent was fixed in patients with either residual stones, renal pelvic perforation or post-operative persistent pain, fever or leakage. Intraoperatively, the total operative time was measured from the time of anaesthetic induction to the end of the procedure, after removing the Amplatz sheath. Also, total fluoroscopy time during the whole procedure was recorded from the fluoroscopy unit. More specifically two more timings were recorded to avoid bias; dilatation time or renal access time measured starting from after placing the central Alken rod over the guide wire, till after dilatation when the Amplatz sheath is placed inside the calyx. Also, fluoroscopy time during dilatation was recorded from the fluoroscopy unit during that same duration. Post-operatively, periodic vital signs and temperature were measured and abdominal examination was done to exclude signs of rigidity. Urine output and colour were monitored throughout the hospital stay. Wound dressing was periodically inspected for signs of leakage and once it became dry, the ureteric catheter was removed. Usually, the ureteric catheter was removed after 24 h unless there was no urine leakage. Time taken for the wound to be dry was noted. Documentation of the post-operative pain was done using a pain scale from 0 to 10, where 0 means no or negligible pain and 10 correlates to maximum pain perceived by the patient, also the frequency of analgesia (NSAIDs) given to the patient was noted. Complications were documented and classified according to the Clavien-Dindo classification. Post-operative haemoglobin concentration and serum creatinine level were measured. Blood transfusion was administered when the haemoglobin drop was less than 9 g/dl or hypotension despite fluid resuscitation. A non-contrast CTUT was done on post-operative day 1 to assess the possibility of any residual stones present and noted if they were larger than 5 mm. Residual stone burden was measured as total of their maximum diameter using post-operative CTUT. Hospitalization time, since the operation was documented in hours. The patient was eligible for hospital discharge when he was vitally stable, no active haematuria, regained normal bowel habits and no significant pain. Patients received the follow-up timing schedule to do abdominopelvic ultrasound and urine analysis.

The mean age for both groups was is 43.8 ± 12.1 years, where it was 43.2 ± 13.0 years for Group A, and 44.6 ± 11.1 years for Group B. Regarding the gender demography of both groups; most of the patients included in the study were males. No significant difference between both groups regarding patients who underwent previous ipsilateral renal surgery for past stones (Open or endoscopic) or ESWL. There was no statistical difference regarding mean BMI for both groups.

The mean number of stones for all patients was 1.81 ± 1.08 stones; 1.63 ± 0.989 stones for Group A and 2.03 ± 1.15 stones for Group B (p = 0.03). There was no significant difference between both groups regarding the stone burden for both groups which was 2.7 ± 1.1 cm (2.64 ± 1.15 for Group A and 2.78 ± 1.09 for Group B) and the mean stone density with a mean of 979.95 ± 353.35 Hounsfield units (940.27 ± 362.97 for Group A and 1028.53 ± 337.96 for Group B) (Table 1). Most stones were single pelvic stones (Fig. 1). There was no significant difference between both groups regarding the parenchymal thickness and skin to stone distance which were measured by the CT scan (Table 1).

Patients who underwent OSD PCNL had statistically significant shorter total fluoroscopy time, shorter fluoroscopy time during dilatation and shorter renal access time during dilatation than Group B (Table 2).

Thirty patients encountered post-operative complications, 8 of them were from Group A while 22 patients were from Group B indicating a statistically significant difference in the rate of complications between both groups (p < 0.001). Most of these patients were complicated by fever (> 38 °C) which was managed conservatively with antibiotics, urinary leakage that was treated conservatively by observation and fluid restriction, and bleeding that required intravenous colloids or blood transfusion, and lastly pain that required opioid analgesics. All of those patients fell under the Clavien-Dindo classification grades I-II except for a single patient that required delayed stenting, who fell under grade IIIa. Another patient who underwent serial dilatation was complicated by infundibular stenosis that was diagnosed 4 months later by CT scan and required delayed stenting. There was a statistical difference in the number of patients who experienced post-operative urinary leakage between both groups with only a single patient in Group A, and nine patients in Group B (p = 0.003). Group A had a significant decrease in pain scores and fewer analgesic doses were needed than Group B (p = 0.006). Patients who underwent OSD have experienced less post-operative fever than patients who underwent serial dilatation. Group A showed shorter average post-operative hospitalization time. There was no statistically significant difference between both groups regarding stone-free rate for group A was 55/71 (77.5%), group B was 48/58 (82.8%) (Table 2).