1. History Wang Chuansheng, Department of Urology, Lu’an Hospital of Traditional Chinese Medicine In 1981, Pfister proposed the Trocameedle technique and Segal proposed the Catheter needle technique; in 1983, Hunter Lawson proposed the retrograde route puncture method and Claymen proposed the one-step balloon expansion method. In 1998, Wu Kaijun and Li Xun proposed multichannel percutaneous nephrostomy [2]. With repeated technical innovations and advances in equipment, this technique has become increasingly accurate and safe [3, 4].
With the development of PCN technology, the practice standards committee of the society of cardiovascular and interventional radiology has developed new guidelines for diagnostic improvement and new definitions of PCN and related technologies [5]: (1) percutaneous nephrostomy (2) Successful percutaneous nephrostomy: placement of a catheter of appropriate caliber to allow adequate drainage of the renal collecting system or successful dilation of the channel for interventional treatment of the fistula.
3. Methods X-ray fluoroscopy and B-ultrasound guidance are the usual methods of puncture guidance.
The patient lies prone with a pillow on the abdomen to limit renal movement with breathing. Continuous epidural anesthesia is often used due to the patient’s surgical position.
The area between the subscapularis and the posterior axillary line below the 12th rib is routinely chosen as the access area, and the collection system is entered through the renal parenchyma via the posterior lateral aspect of the kidney, avoiding direct puncture of the renal pelvis. This is because direct puncture of the renal calyces is likely to damage the renal vasculature during dilatation, and the establishment of access is difficult to achieve. In the case of a stone patient undergoing PCN to retrieve a stone, the stone in the renal pelvis is entered through the inferior or middle calyces, while the stone in the middle calyces is entered directly.
3.3.1 Ultrasound guidance: Ultrasound can clearly visualize the cross-section of the collection system when there is significant fluid accumulation. However, if the collection system is dilated <2 cm, it is significantly more difficult to accurately and stably display the collection system cross-section by ultrasound, and it is also significantly more difficult to puncture the collection system, which can be effectively solved by retrograde cannulation to create artificial hydronephrosis[6] .
3.3.2 Fluoroscopic guidance: To identify the puncture target before performing the puncture, the collection system needs to be displayed. There are two methods of display: (1) intravenous nephrography, in which contrast is injected intravenously during the procedure and the collecting system of the kidney is visualized. This method is convenient but does not reveal well in cases of abnormal renal function and has a short revealing time. (2) Retrograde ureteral cannulation with contrast can clearly visualize the collecting system and dilate it appropriately to facilitate successful puncture, and the contrast can be repeated as many times as needed to clearly visualize the collecting system[7] .
3.4 Establishment of percutaneous nephrostomy access: A small incision is made in the skin of the selected puncture site, and the collection system is punctured with a needle core in the proposed position. The guidewire is inserted through the sheath into the renal collection system, preferably into the ureter, so that the guidewire is less likely to dislodge and twist during the dilatation of the channel. After placement of the guidewire, the needle sheath is withdrawn, and the puncture channel is dilated and left in place. The following points should be noted during the dilation operation: (1) The surgeon should operate by gently pulling the guidewire with one hand to keep the guidewire under tension and holding the fascial dilator with the other hand for dilation. The assistant only assists in the fixation and delivery of the guidewire. (2) The fascial dilator tube must be dilated along the guidewire. (3) The fascial dilator tube is rotated back and forth, advancing while rotating, so that the fascial dilator reaches the set depth. (4) When the fascial dilator reaches the set depth, there should be urine or fluid flow[2] .
The advantages and disadvantages of X-ray fluoroscopic guidance and B-ultrasound guidance are: accurate positioning and clear images. The disadvantages are: it can only provide a flat image with precise superior-inferior relationship, but the anterior-posterior relationship is basically determined by experience; it requires contrast injection to show the renal collecting system, which is risky in cases of renal impairment; the impact of X-rays on human health is greater; X-ray positioning requires an X-ray C-arm machine, which to a certain extent limits the clinical development of PCN surgery.
The advantages of B-ultrasound positioning for percutaneous nephrostomy have been reported in clinical practice[8] , including: the ability to clearly visualize the upper, middle, and lower calyces of the kidney, and the ability to visualize both the stone and the fluid-filled calyces where the stone is located; the ability of B-ultrasound to provide the distance from the fluid-filled calyces to the skin on the channel during the monitoring of channel expansion, which provides a reliable basis for the operator to grasp the depth of puncture and expansion; and the ability to continuously monitor the expansion process and the position of the expansion instrument in the kidney in real time, which increases the efficiency of percutaneous nephrostomy. It increases the flexibility and accuracy of percutaneous renal puncture and reduces blood loss during puncture of the dilated channel; it is not harmful to human health. The disadvantages are: compared with X-ray localization, B-ultrasound image is not as clear as X-ray image, which requires higher technical requirements; in cases of kidney stones without hydronephrosis, B-ultrasound localization is more difficult to puncture; the tip of the dilator cannot be clearly displayed, and it is easy to puncture too deep and cause mucosal damage or even perforation of the renal calyx[9,10] .
The main indication for PCN is urinary tract obstruction, and stones, tumors, and medical injury are common causes of obstruction. Most patients are not aware of the obstruction until they develop azotemia or urinary tract infection, sepsis, or incidental physical examination imaging.5,11,12 ] PCN not only facilitates the maximum recovery of renal function, but also allows the accurate measurement of urine volume, urine p H value, urine specific gravity, urine biochemistry of the obstructed kidney during drainage, as well as B ultrasound measurement of renal cortical thickness to dynamically monitor the morphological and functional changes. The morphological and functional changes can be monitored dynamically during drainage to guide further treatment. In patients with chronic obstructive renal failure, hemodialysis can be avoided or the duration of dialysis can be reduced [13], and in a small number of patients with progressive intra-abdominal or pelvic organ malignancies or extensive metastases that are ineligible for surgery, PCN is sometimes even better than ureteral stent drainage [14].
The role of PCN is to drain pus or fluid and to obtain important bacteriologic information directly from drainage fluid culture to guide treatment, control infection, and rescue and protect renal function [15]. Acute obstructive sepsis is common in clinical practice, especially in elderly patients with poor systemic condition, who are prone to rapid onset of infectious toxic shock, and PCN is a minimally invasive way to rapidly relieve the threat of infection and provide a basis for second-stage surgery [16].
5.3, Urinary extravasation or fistula: In the presence of urinary extravasation and fistula, unobstructed drainage or complete urinary diversion is essential to reduce extravasation and promote fistula healing. Some renal and ureteral injuries may not be treated in one stage for various reasons, resulting in the formation of a urinary cyst or fistula, and pelvic fistula drainage is the first and most important step in their management [17].
5.4, perform other operations or endoscopy[5] :
5.4.1 Percutaneous nephrostomy for stone extraction: PCN is an essential technique and preoperative preparation for percutaneous nephrolithotomy and ureteroscopy, and 50% of PCNs are used for stone extraction in some specialized hospitals abroad.
5.4.2 Injection of drugs into the collecting system: for lithotripsy of certain renal and ureteral stones and for infusion of BCG vaccine for the treatment of metastatic epithelial tumors in the upper urinary tract.
5.4.3 Others: Ureteral placement when retrograde ureteral intubation is not appropriate or when retrograde ureteral intubation has failed, and for removal of foreign bodies such as broken or displaced ureteral catheters.
5.5 Urinary diversion for hemorrhagic cystitis: The use of PCN for transplanted kidneys is generally consistent with that for autologous kidneys, and sometimes PCN can be used as an experimental treatment to identify renal failure due to obstruction or rejection. In summary, the indications for PCN include: urinary tract obstruction with or without co-infection, stones, preparation for endoscopy or other procedures, drug infusion or chemotherapy, and urinary diversion.
6 , contraindications [1 ,18 ]
Contraindications to PCN are: severe coagulation disorders that are difficult to correct (liver failure or multi-system organ failure); severe kyphosis of the spine, unable to lie prone; severe heart disease and pulmonary insufficiency, unable to tolerate the procedure; uncorrected severe diabetes mellitus and hypertension; extreme obesity, waist skin-kidney distance of more than 20 cm, difficulty in establishing skin-kidney access; taking aspirin, warfarin, etc. Patients on aspirin, warfarin, and other drugs should stop taking them for 3 to 4 weeks before surgery; patients with advanced disease or dying.
Patients with severe metabolic disorders, hyperkalemia, or metabolic acidosis should be corrected to avoid cardiac arrhythmias or cardiac arrest.
The age of the patient is not a limiting factor for PCN, which has a high safety profile in the pediatric population and even in infants. A group of children with a mean age of 3.4 years and a minimum weight of 12 kg has been reported to have successfully completed PCN under sedation without serious complications [19].
7, Complications and management Generally, PCN is relatively safe, with an operative mortality rate of approximately 012%. Complications are classified according to their prognosis, with significant ones resulting in hospitalization, prolonged hospitalization, elevated level of care, permanent sequelae, or death, and minor ones requiring hospitalization for observation according to medical procedures in addition to significant complications [18].
The incidence of major complications is about 4% and the incidence of minor complications is about 15%; the incidence of both together is about 19% [5 ].
7.1 Hemorrhage, perirenal hematoma, and hematuria: There is usually minor bleeding after PCN, mostly in the form of hematuria, which disappears within 1 week. The incidence of hemorrhage can be largely reduced by selecting a relatively non-vascular area of the kidney at the time of puncture, and the compression of the renal tissue by the fistula itself can limit bleeding. If the hematuria is obvious, the fistula can be clamped for 30 to 60 minutes and the bleeding usually stops on its own. In rare cases, severe bleeding occurs due to vascular injury, requiring blood transfusion, selective vascular embolization, or even surgery to stop the bleeding. Some patients may develop perirenal hematoma, which is usually asymptomatic and progressive and does not require special management [11,12]. In patients with indications for puncture, abnormalities in prothrombin time and partial thromboplastin time alone do not lead to a significantly higher incidence of bleeding unless combined with active liver disease, coagulopathy, recent use of warfarin and heparin, and platelets below 100 × 109/L [20]. In such cases, PCN should be performed only after improving liver function and coagulation, discontinuing warfarin and heparin, and raising platelets.
7.2 Infection and fever: Patients undergoing PCN have the potential for infection, with the latter being more likely in renal transplantation. In addition to the existing infection in the urinary tract, the fever may be related to retrograde ureteral cannulation, flushing, long operation time and high pressure in the renal calyces. The fever usually resolves within 48 h. Prophylactic antibiotics are necessary before PCN surgery.
7.3 Catheter-related complications: Within 1 week after PCN, before the sinus tract is formed, the fistula is not easily reinserted through the original channel, so it is important to improve the care of the fistula during this period. In addition, fistulae may become blocked, displaced, or difficult to remove. The catheter should usually be replaced once every 3 months or so.
7.4 Injury to adjacent organs: Pleural injury can result in pneumothorax. Pneumothorax rarely occurs with a subcostal puncture fistula at 12 ribs, unless the needle enters too high. The chance of pleural injury is reduced by entering the needle after end-expiratory closure. Even after passing through the thoracic cavity, only a small amount of air or fluid enters the thoracic cavity and can be absorbed on its own, provided a suitable postoperative fistula is placed. The main abdominal organ injuries are intestinal and liver and spleen injuries, which are unlikely to occur, but can have serious consequences if not vigilant. During the operation, the puncture should be accurately positioned, and the needle should be inserted and dilated rather shallowly than deeply. The needle should be inserted posteriorly and dorsally in the posterior axillary line as much as possible to avoid damage to the abdominal organs. The patient’s general condition and abdominal condition should be closely observed during the operation, and complications should be detected and treated early, and open surgery should be performed if necessary.
7.5 Perforation and laceration of the renal collecting system: Prevention of perforation and laceration of the renal collecting system is important, and the key is to operate gently. If these complications occur, a double J ureteral stent and a nephrostomy tube can be placed as long as the bleeding is not very serious and not excessive.
7.6 Renal penetrating injury: Usually conservative treatment can stop the bleeding, but if the bleeding is severe and the patient has early changes in vital signs, early open surgery or selective renal artery embolization via interventional radiology is required.
7.7 Renal arteriovenous fistula: selective renal artery embolization with interventional radiology is effective.
7.8 Pelvic ureteral junction stenosis: open pyeloplasty can be performed [9], or the stenotic segment can be lumpectomized or balloon dilated after 3-6 months.
7.9 Urinary extravasation: Mostly urine leaks into the perinephric area through the punctured dilated dermal kidney channel. A small amount of extravasation is usually not treated and can be absorbed on its own, while a large amount must be drained perirenally. In cases of severe hydronephrosis, if the fistula is removed too early after surgery, the thin renal cortex may lose its contractile function and the fistula may not close easily, resulting in extravasation. If a perirenal fluid dark area is found on postoperative B-ultrasound, puncture and aspiration or drainage tube can be placed.
7.10 Late hemorrhage: The amount can be more than 200-500 ml, mostly occurring 8-12 days after surgery, and the patient often has a history of kidney stone infection or open surgery. The intraoperative injury bleeding is more obvious, accompanied by the affected kidney distension and lumbago, the bladder is blocked by blood clots or even filling, followed by fever and chills, and even shock symptoms may appear if the bleeding volume is large. Braking and anti-shock treatment should be taken immediately to clear the bladder clot and flush the bladder. If the bleeding cannot be controlled, early radiological intervention for highly selective renal artery embolization should be performed, which can receive immediate effect.
7.11 Others: Contrast extravasation, etc.
In conclusion, PCN opens up a new way for minimally invasive treatment of urological diseases, and its operation techniques and materials and equipment are still being improved and updated so that this technique can be applied more widely and safely.