”Percutaneous nephrolithotomy (PNL) was first performed in some countries in Europe and the United States, but since the mid-1980s, with the advancement of optical and electronic engineering technologies and the widespread use of ultrasound, radiological intervention, CT, MRI and other technologies, the clinical application of percutaneous nephrolithotomy has developed leaps and bounds. The use of minimally invasive percutaneous nephrolithotomy (MPNL) was proposed in 1997 to reduce surgical complications and damage to the renal parenchyma, but it is mostly used for the treatment of stones ≤2 cm, pediatric kidney stones or cases requiring the establishment of a second channel. The indications for the use of MPNL are limited. In China, “percutaneous nephrostomy and second-stage ureteroscopic lithotripsy” has been used since 1992, and with the improvement of surgical skills and lumpectomy equipment, minimally invasive percutaneous nephrolithotripsy with Chinese characteristics was proposed in 1998 and gradually promoted nationwide. It has been applied to most of the upper urinary tract stones that are difficult to be treated by ESWL and open surgery. In recent years, a large number of retrospective clinical reports have shown that this method is easier to master and perform than standard PNL, with a higher success rate and fewer complications than foreign techniques.
Nowadays, percutaneous nephrolithotomy (either PNL or MPNL) is playing an increasingly important role in the treatment of upper urinary tract stones.
Indications
(1) All kidney stones requiring open surgical intervention, including complete and incomplete deerstalker stones, ≥2 cm kidney stones, symptomatic stones in the calyces or diverticula, stones that are difficult to crush by extracorporeal shock wave and those that have failed treatment.
(2) Ureteral stones above L4 in the upper part of the ureter, with heavy obstruction or long diameter >
1.5cm in length; or ureteral stones with polyps and tortuous ureter, and where extracorporeal shock wave lithotripsy (ESWL) is ineffective or ureteroscopy has failed.
(3) Special types of kidney stones, including pediatric kidney stones with significant obstruction, kidney stones in obese patients, kidney stones with pelvic-ureteral junction obstruction or ureteral stenosis, isolated kidney with stone obstruction, horseshoe kidney with stone obstruction, transplanted kidney with stone obstruction, and kidney stones without effusion, etc.
Contraindications
(1) Uncorrected systemic bleeding disorders.
(2) Severe cardiac disease and pulmonary insufficiency that cannot tolerate surgery.
(3) Those with uncontrolled diabetes mellitus and hypertension.
(4) Those with pelvic wandering kidney or severe renal prolapse.
(5) Those with severe kyphosis or scoliosis deformity, extreme obesity or intolerance of prone position are also relative contraindications, but surgery can be performed in supine, lateral or supine oblique positions.
(6) If you are taking anticoagulant drugs such as aspirin or warfarin, you need to stop taking them for 2 weeks and recheck the coagulation function before surgery.
Treatment options and principles
(1) Percutaneous nephrolithotomy should be performed in a hospital where it is available. Microstomy PNL is recommended as the first choice, and the procedure should be performed by an experienced surgeon using different sized channels and different types of instruments according to the specific situation.
(2) In the early stages of the procedure, it is advisable to select simple cases, such as: single pyelonephrosis combined with moderate or above hydronephrosis, with a moderately thin patient and no other concomitant diseases.
(3) Complex or oversized renal stones are more difficult to operate, and should be treated by experienced surgeons, not excluding open surgical treatment (methods refer to open renal surgery).
(4) Combined renal insufficiency or pus accumulation in the kidney should be drained by percutaneous nephrostomy first, and the stone should be retrieved in the second stage after the renal function is improved and the infection is controlled.
(5) Complete antler-shaped kidney stones can be retrieved in multiple stages, but the number of operations should not be too many (generally ≤3 times unilaterally), and the duration of each operation should not be too long, depending on the patient’s tolerance. For residual stones >0.4 cm in diameter after multiple PNLs, ESWL can be used in combination.
Preoperative preparation
Most kidney stones can be removed by percutaneous nephrectomy; however, PNL must be applied with caution if the patient can be treated with ESWL and the expected therapeutic outcome of PNL is not better than that of ESWL. Although PNL is a minimally invasive procedure, it still carries some invasiveness and risk. Therefore, before deciding to use this treatment, the anatomy of the patient’s kidney and its surrounding organs must be carefully evaluated to avoid complications.
Preoperative preparation is approximately the same as for open surgery. If bacteria are present in the urine culture, a sensitive antibiotic should be selected for treatment, and even if the urine culture is negative, a broad-spectrum antibiotic should be chosen to prevent infection on the day of surgery.
It must be fully recognized that the purpose of surgery is to relieve obstruction and reduce the damage of stones to renal function; residual stones are unpredictable preoperatively, and residual stones can be treated postoperatively in combination with ESWL and Chinese medicine; for meaningless residual stones can be reviewed regularly. It should be emphasized that patients and their families must be informed in writing of the possibility of bleeding, surrounding organ damage, the need for intermediate open surgery in severe cases, and even the need for nephrectomy both intraoperatively and postoperatively.
Surgical steps
(1) Positioning: B-ultrasound or X-ray C-arm machine is used for positioning. In order to show the renal collecting system, retrograde ureteral cannulation angiography is feasible. If the renal calyces are significantly dilated, the target calyces can be directly punctured under ultrasound localization; if ultrasound localization can only show the renal pelvis, a pelvis puncture can be made first to inject contrast for the next step of puncturing the target calyces under X-ray localization. If CT localization is used, puncture is performed directly into the renal collecting system without intraoperative contrast or retrograde cannulation.
(2) Puncture: The puncture site can be chosen in the area between the posterior axillary line and the scapular line from the 12th to the 10th intercostal space, and the puncture is made through the posterior group of calyces and directed toward the renal pelvis. For upper ureteral stones, multiple renal stones, and combined UPJ stenosis requiring simultaneous treatment, the posterior middle calyces approach is preferred, and the area between the posterior axillary line of the 11th intercostal space and the subscapular line is usually chosen as the puncture site. When puncturing the upper and lower group of calyces, attention must be paid to the possibility of injury to the pleura and intestinal canal.
(3) Dilation: The renal puncture channel can be dilated with a fascial dilator, an Amplatz dilator, a high-pressure balloon dilator, or a metal dilator. However, the exact type of dilator used and the size of the dilated channel must be determined by the experience of the physician, as well as the instrumentation available at the time and the cost of treatment.
(4) Intracavitary lithotripsy and stone extraction: Stones can not only be removed directly, but can also be discharged by laser, pneumatic ballistics, ultrasound, and liquid electrolysis. The ballistic lithotripter with ultrasound and suction has the function of both pneumatic ballistic lithotripsy, ultrasound lithotripsy and simultaneous aspiration of stone fragments to reduce intrarenal pressure, which is especially suitable for patients with large infected stones. It is safer to place a double J-tube and a nephrostomy tube. The nephrostomy tube is left in place at the end of the procedure to compress the puncture channel, drain the renal collecting system, reduce postoperative bleeding and urinary extravasation, and facilitate the re-treatment of residual stones, without increasing the degree of pain or prolonging the hospital stay of the patient.
Common complications and their management
The main complications are bleeding and perirenal organ damage. If intraoperative bleeding is high, the operation needs to be stopped and a nephrostomy tube placed for an elective second-stage procedure. When the nephrostomy tube is clamped, most of the venous bleeding can be stopped. Persistent, clinically significant bleeding is usually due to arterial injury and often requires angiography followed by superselective embolization. If the bleeding is aggressive and difficult to control, the procedure should be converted to open surgery in order to explore and stop the bleeding, and if necessary, remove the affected kidney.
Most delayed hemorrhage is due to arteriovenous fistula or pseudoaneurysm of the renal parenchyma, and vascular intervention with superselective renal artery embolization is an effective management method.
Most perirenal organ injuries are pleural, hepatosplenic, or colonic puncture injuries, and the emphasis is on prevention and timely detection and management consistent with surgical principles.