Minimally invasive treatment of urinary stones: percutaneous nephrostolithotomy

The description of the minimally invasive treatment of urinary stones: percutaneous nephrostolithotomy covers all aspects of the surgical procedure used for the management of urinary stones. Operating room set up, position of patient and equipment, instruments used are thoroughly described. The technical key steps of the surgical procedure are presented in a step by step way: puncture area, main steps, stent placement, calyceal puncture, tract dilation, stone localization, fragmentation of calculi, drainage. Consequently, this operating technique is well standardized for the management of this condition.

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Minimally   invasive   treatment   of   urinary   stones:   percutaneous   nephrostolithotomy

Authors
F Desgrandchamps
Abstract
The description of the minimally invasive treatment of urinary stones: percutaneous nephrostolithotomy covers all aspects of the surgical procedure used for the management of urinary stones.
Operating room set up, position of patient and equipment, instruments used are thoroughly described. The technical key steps of the surgical procedure are presented in a step by step way: puncture area, main steps, stent placement, calyceal puncture, tract dilation, stone localization, fragmentation of calculi, drainage.
Consequently, this operating technique is well standardized for the management of this condition.
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2002-01
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E-publication
WeBSurg.com, Jan 2002;2(01).
URL: http://www.websurg.com/doi-ot02en253.htm

Minimally   invasive   treatment   of   urinary   stones:   percutaneous   nephrostolithotomy

1. Introduction
Percutaneous nephrostolithotomy is based on the creation of a tract in the lumbar area, between the skin and pyelocalyceal cavities. This tract, which is 1 cm in diameter, most frequently goes through the inferior pole of the renal parenchyma. A nephroscope and other instruments can then be passed through this tract to fragment or remove renal stones (Alken, 1981; Le Duc, 1991).
2. Anatomy
• Posterior border
1. 11th rib
2. 12th rib
3. Psoas muscle
4. Transversus abdominis fascia
5. Quadratus lumborum
The kidney is in direct contact with the para-lumbar muscles. Its inferior pole is not separated from these muscles by pleura or peritoneum.
• Vasculature
The risk of vascular injury is decreased if the puncture area is in the posterior part of the kidney in the axis of the posterior calyx, at the junction of the anterior and posterior vascular systems (at about a 70° angle from the frontal plane of the mid-kidney).
• Calyceal system
The calyceal system is best accessed through a posterior approach.
The inferior-pole calyceal system consists of an anterior (ventral) group and a posterior (dorsal) group and often an inferior mid-renal calyx. The only calyces that should be used for access to the urinary system are those with an inferior or posterior positioning.
3. Indications
Indications for treatment of single stones
Large renal pelvis and calyceal calculi
Large calculi (>2.5 cm) or staghorn calculi can be treated by the percutaneous surgical procedure alone or in combination with shock-wave lithotripsy of any residual stone.
Staghorn calculi best suited for this kind of treatment have few ramifications and wide branches.
Soft calculi and encrusted pyelitis

After failure of shock-wave lithotripsy:
Renal pelvis calculus
A renal pelvis or calyceal stone of less than 2.5 cm can be reached:
- via the posterior lower-pole calyx for renal pelvis and inferior or superior-pole calyceal stones (with rotation exerted on the kidney);
- via the middle-pole calyx for renal pelvis and middle-pole calyceal stones.
Upper ureteral calculus
- preferred access is via the middle-pole calyx, which allows access to the ureteropelvic junction while rotating the kidney.

Indications for calculi coupled with urinary excretory system anomalies
- ureteropelvic junction (UPJ) obstruction;
- calyceal diverticulum.

Contraindications
- hemostatic defect;
- bacteriuria;
- pyelonephritis.
4. Preop period
The patient must have a negative urine culture before undergoing the procedure. When the urine is sterile, the patient is given a preventative dose of second generation cephalosporine. In case of bacteriuria, antibiotic treatment is started at least 10 days prior to the surgical procedure, and completed with double antibiotic therapy started 48 hours preoperatively (third generation cephalosporin or fluoroquinolone, and aminoglycoside).
In case of pyelonephritis in an obstructed kidney secondary to a stone, a drainage procedure (ureteral stenting or percutaneous nephrostomy) is required. The retrieval of urinary calculi is accomplished after prolonged drainage and proper antibiotic treatment (20 days minimum).
In all cases, urine sterility must be confirmed the day before surgery by bacteriologic culture.
5. Operating room
• Upper collecting system
All OR personnel must wear lead aprons.
The procedure is performed under general anesthesia. Fluoroscopy or ultrasound is available in the room for localization of the upper collecting system.
The initial step for fluoroscopic guidance is placement of the ureteral stent:
- the patient lies supine with the thighs flexed;
- the surgeon is positioned at the lower end of the table, facing the perineum;
- the monitor and magnifier are to the right of the surgeon.
• Percutaneous approach
The second step is the percutaneous step:
- the patient lies in the prone position, one roll under the shoulders and another under the iliac crests, to allow free respiratory movement;
- the thorax is flexed opposite the area of puncture to open up the space between the 12th rib and iliac crest;
- the surgeon is positioned on the side of the kidney that will be operated on;
- the assistant stands next to the surgeon;
- the monitor is at the head of the table;
- the fluoroscopic screen and ultrasound machine face the surgeon;
- the lithotripsy instruments (ultrasound, laser or electrohydraulic) are placed next to the surgeon;
- the instrument table is placed behind the surgeon.
If a double J stent is already in place because of an obstructive stone, the upper collecting system can be opacified in a retrograde manner by injection of contrast into the urinary bladder through the urinary catheter.
6. Puncture area
Landmarks
In most cases, percutaneous nephrostolithotomy is best performed through the lower-pole calyx.
The landmarks for puncture of this calyx of entry are as follows:
- between the 12th rib and the iliac crest;
- on the posterior axillary line;
- the needle is inserted at a 45° angle on a horizontal plane and a 45° angle on a frontal plane.
An overly posterior puncture near the sacro-lumbar muscles must be avoided, because the opening of the tract would then be perpendicular to the axis of the calyx, making access to the collecting system more difficult for the surgeon. An overly lateral puncture might cause injury to the colon, and should be avoided as well.
If the position of the stone and structure of the collecting system make it unavoidable, a direct puncture into the superior calyx is performed between the 11th and 12th ribs. This approach involves a risk of pleural laceration.
Due to the congenital malrotation associated with a horseshoe kidney, the inferior calyx is in a very posterior location. Therefore, in the case of a horseshoe kidney, the puncture should be made posteriorly, near the sacro-lumbar muscles, and almost vertically in order to be in alignment with the axis of the calyx.
7. Main steps
• The 6 steps
There are 6 main steps in the percutaneous management of a kidney stone (Le Duc et al., 1999):
- placement of the ureteral stent;
- puncture of the calyx;
- dilatation of the tract;
- search for the stone(s);
- fragmentation of the stone(s);
- postoperative drainage.
The instruments used are first described (placement of stent, percutaneous approach, extraction of stones).
• Placement of stent
1. Fiberoptic cystoscope
2. Rounded tip stent for retrograde ureteropyelogram
3. Straight ureteral stent with cut end

For placement of the stent:
- irrigation with saline;
- contrast agent;
- 0.035 inch metallic guidewire;
- fluoroscope;
- 1 L bag with a mixture of saline, contrast agent and methylene blue.
• Percutaneous approach
1. Puncture needle adaptable to a 0.035 inch metallic guidewire
2. Metal telescoping dilators
3. Plastic sheath, 1 cm in diameter

For creation of the tract:
- two 0.035 inch metallic guidewires or bougie dilators or inflatable balloon dilator;
- intraoperative ultrasound;
- fluoroscope;
- safety wire;
- safety guide wire introducer.
• For extraction of stones
1. Fiberoptic nephroscope
2. Forceps (with 2 jaws) or tripod forceps

- irrigation with saline;
- intracorporeal lithotripsy instrumentation (ultrasound, electrohydraulic or laser);
- fibroscope (optional).
8. Stent placement
Ureteropyelogram
This step facilitates puncture of the calyx by the injection of contrast into the upper collection system by the ureteral catheter.
A cystoscope is inserted into the bladder. A retrograde ureteropyelogram is performed with a rounded tip catheter.
A metallic guidewire is introduced and a straight ureteral catheter is inserted over it under fluoroscopic guidance until the pelvis is reached. This catheter is anchored to a urinary catheter to avoid movement when the patient is later put into a prone position.
To identify the lithiasis on the fluoroscope screen, it is important to avoid overfilling the collecting system with contrast agent at this stage.
9. Calyceal puncture
• Landmarks
Localization of stones must be carefully studied on the urogram to choose the best calyx of entry.
• Puncture
The ultrasound probe is placed on the para-lumbar area to locate the kidney and stones. A combination of saline, contrast agent and methylene blue is injected through the ureteral catheter. The inferior-pole calyx is punctured under fluoroscopic and ultrasound guidance.
• Needle insertion
The following radiological signs indicate that the needle has reached its target:
- movement of the kidney when the needle touches its capsula;
- deformation of the calyx when the needle reaches its distal wall;
- mobilization of the needle causes simultaneous mobilization of the infundibulum.
The stylet of the needle is removed. Outflow of methylene blue confirms satisfactory placement of the needle in the collecting system.
10. Tract dilation
Creation of the tract
This is done over a metallic guide by the use of:
- metal telescoping dilators;
- bougie dilators;
- an inflatable balloon dilator.

Telescoping dilators
This technique is the most effective. Introduction of the telescoping dilator through the tract is done by alternating axial rotation and pressure. If there is resistance, the dilator is retracted a few millimeters, and the rotation-pressure movement is resumed.

Bougie dilators
In this type of dilation, the axis of dilation is not maintained constantly as smaller bougie dilators are progressively replaced by larger ones.

Inflatable balloon dilator
This type of dilatation is fairly gentle and gradual. The main drawback of this technique is its cost. The theoretical advantage is reduced bleeding by continuous tamponade.
A safety guidewire is placed during the dilation, either through a large internal diameter dilator or through a safety guide wire introducer.
Dilation is continued until the sheath of a nephroscope or a plastic sheath can be inserted, according to the surgeon’s preference.
11. Stone localization
The first step is aspiration of blood clots via the nephroscope.
Usually, the stone is seen immediately, often coupled with an adherent clot.
If not clearly visualized, the stone must be looked for by exploration of the cavities, under fluoroscopic guidance, and sometimes with the use of a flexible nephroscope.
12. Fragmentation of calculi
• Stone retrieval
A small urinary stone can be caught with a tripod grasper and extracted in one piece.
• Fragmentation of calculi
Large stones must be fragmented.
Ultrasonic lithotripsy can progressively destroy the stone. The fragments are rapidly suctioned out by the probe.
Electrohydraulic or laser lithotripsy devices can break these stones into pieces that can be extracted with a tripod grasper.
13. Drainage
End of procedure
It is best to end the procedure by placing a nephrostomy tube under fluoroscopic guidance. This drains urine and maintains access for the retrieval of residual stones.
In some cases, if the procedure is rapid and the bleeding minimal, placement of a nephrostomy tube may be omitted (Bellman et al., 1997).
14. Difficult cases
Puncture problems
- a mobile kidney that is difficult to puncture can be held in place by a needle previously inserted through the parenchyma.
- retracted excretory pyelocaliceal cavities: the inferior-pole calyx cannot be accessed. The puncture should be performed directly over the stone.
- horseshoe kidney: the puncture should be performed in a posterior and almost vertical manner, because of the associated congenital malrotation that modifies the axis of the posterior calyces.

Dilation problems
- buckling of the guidewire: a flexible dilator is passed over the buckled guidewire. The latter is removed and a new guidewire is passed into the dilator. To avoid future buckling, the axis of the guidewire placement should be identical to that of the initial needle puncture.
- resistance during the passage of the dilators: the skin incision should be lengthened along the guidewire, particularly in kidneys previously operated on.

Problems in localizing the stones
If the stone is not found after complete aspiration of the blood clots, the surgeon must explore the collecting system under fluoroscopic guidance.
A flexible scope may be useful if the stone is not accessible by the initial calyceal entry.
A second puncture may be necessary.

En bloc extraction of a large stone
If the surgeon wishes to extract a large stone whose diameter is superior to that of the plastic sheath, a longitudinal incision may be made on the sheath.

Loss of the tract
If the surgeon is no longer in the collecting system and loses the tract, the pearly-white appearance of the collecting system wall is replaced by fibrous tissue, representing peri-renal fat.
Injection of methylene blue through the ureteral catheter serves as a guide to find the way back into the tract.
If this method fails, the security guidewire should be used to put the nephroscope back into its proper position.
15. Complications
Bleeding
An increase in the irrigation flow allows continuation of the procedure if minor bleeding occurs.
If there is heavy bleeding, the procedure should be stopped and a 18 Fr to 20 Fr nephrostomy tube is inserted and immediately clamped.
Venous bleeding is stopped with simple increase of pressure in the collecting system, by accumulating blood clots after a clamping time of 20 to 30 minutes.
Arterial bleeding will persist in spite of temporary clamping. This is properly managed by immediate arteriogram with embolization of the bleeding renal or intercostal artery.

Pleural effusion
A pleural effusion is caused by the diffusion of irrigation fluid to the pleural cavity through a small pleural laceration. It is treated by simple thoracentesis.
Sometimes intercostal thoracic puncture, with deliberate pleural laceration, is chosen as a means of accessing stones that are difficult to reach.

Colon perforation
Colon injuries are mostly retroperitoneal. They are associated with very lateral puncture sites and partly retro-renal colon positioning. Diagnosis may be intraoperative with visualization of the lumen of the colon with the nephroscope. A drain is placed in the colic lumen, the procedure is stopped, and the urinary collecting system is drained separately.
Diagnosis of this complication is usually made on the third or fourth postoperative day. It is clinically characterized by the manifestation of lumbar pain and fever. An abdominal CT scan with contrast confirms diagnosis with demonstration of a transcolic nephrostomy tube. This drain should be left in place and the collecting system should be independently drained.
In addition to distinct drainage of colon and kidney, antibiotic treatment should be started and a normal diet is resumed very slowly. The colic drain is progressively pulled out over a period of 10 days. The colo-cutaneous fistula tract will spontaneously close. The renal drain is then taken out.
16. Reference
Alken P, Hutschenreiter G, Gunther R, Marberger M. Percutaneous stone manipulation. J Urol
1981;125:463-6.
Bellman GC, Davidoff R, Candela J, Gerspach J, Kurtz S, Stout L. Tubeless percutaneous renal
surgery. J Urol 1997;157:1578-82.
Dore B, Irani J, Bon D, Marroncle M, Aubert J. Un artifice technique pour l'extraction percutanee en
monobloc de certains calculs renaux superieurs a 10 mm. Prog Urol 1994;4:248-50.
Le Duc A. La chirurgie percutanée du rein lithiasique. Chirurgie 1991;117:19-21.
Le Duc A, Desgrandchamps F, Cortese A, Cussenot O, Teillac P. Chirurgie percutanée du rein pour
lithiase. Encycl Méd Chir (Elsevier, Paris), Techniques chirurgicales – Urologie, 41-090-B, 1999, 14p.