 |
       |
|
|
PERCUTANEOUS NEPHROLITHOTOMY (PCNL) Key hole surgery for kidney stones
S W Thatte
Hon. Associate Urologist, Bombay Hospital Institute of Medical Sciences. Mumbai 20.
During the last 10-15 yrs tremendous changes have taken place in the management of kidney stones. Prior to these modifications all the kidney stones were managed by open pyelolithotomy or nephrolithotomy which caused a significant morbidity for the majority of patients. The revolution regarding percutaneous access started way back in 1955 when Goodwin and his associates did the first percutaneous nephrostomy, a tract meant for drainage of pus and urine. In late 1970 this access was further utilised for removal of stones, initially it was for high risk patients and done at specialised centres, but over the years it has been practised in many centres and has replaced open operation in majority of patients with renal stones.
Extracorporeal shock wave lithotripsy (ESWL) has replaced percutaneous nephrolithotomy (PCNL) much as the latter replaced open surgery, but a place exists in clinical practice this day for PCNL as well as open procedure and it is important for surgeons and urologists to be familiar with this technique of PCNL.
Indications for PCNL
- Renal calculi greater than 3 cms in diameter.
- Stone with composition inappropriate for ESWL.
- Complete or partial staghorn calculus.
- Renal malformations like infundibular stenosis, pelvi - ureteric Junction obstruction.
- Cystine calculi greater than 1.5 cm.
- Failure of ESWL.
- Body habitus unsuitable for ESWL.
An ideal patient for PCNL is one who has two functioning kidneys and 2 cm stone in one of the kidneys with extrarenal pelvis with mild to moderate hydronephrosis. PCNL procedure has advantage of short hospital stay, small stab wound scar and negligible pain in the post operative period.
Even today in good centres doing large stone work 10% to 15% require PCNL either by itself or together with ESWL.
The patient needs to undergo pre operative workup as required in open operation and urine infection if present to be covered by prior antibiotics, the PCNL procedure is done with help of imaging facility like "C" Arm or fluoroscopy and under general anaesthesia.
Technique of Percutaneous Nephrostomy
Initial step of PCNL is cystoscopy and placement of an open ended or ureteric catheter on the side of the stone and injecting dye which will give the configuration of the pelvi-calyceal system. The patient is placed in prone position. Proper PCN tract is critical to the success in removing stones. Two important considerations are safety and access. Always use a posterolateral approach. Use middle or inferior calyx for pelvic or upper calyceal stone or direct access to a calyceal diverticular stone. Do not make a tract directly into the pelvis but to go through posterior calyx end on so that parenchymal hold helps in maintaining the tract.
Standard Puncture (Fig. 1)
The puncture is made with needle and help of "C" Arm. Once the needle is in pelvicalyceal system, a J tipped, Teflon coated movable core guidewire is negotiated into the renal pelvis and across the Pelviureteric Junction into the ureter, a second guide wire called the "safety wire" is also passed into ureter, if wire can not be passed into ureter than it can be coiled into the calyces so that the guide wire does not get pulled out of the kidney accidentally.
Fig. 1 : Standered Puncture. Tract Dilatation (Fig. 2)
To check if guide wire is in proper position with the rigid portion of wire across the renal parenchyma, fascia and the body layers. Dilatation need to be done under fluoroscopy to see that it is along the guide wire and it should not be bent during the process of dilatation.
Several options are available to enlarge the tract to a size of about 34 FR. Sequential Amplatz dilators, telescopic metal dilators or high pressure balloon. Balloon dilation is less traumatic and results in less bleeding but expensive. At the end Amplatz sheath is positioned over the last dilator to the appropriate site as this will be the conduit for further instrumentation.
Fig. 2 : Tract Dilatation. Stone Removal (Figs. 3,4 and 5)
As with all types of surgery, a clear field is a prerequisite to definitive treatment, after the dilatation visibility may be poor due to blood clots. Renal pelvis is flushed with irrigant through thesheath or from below by open ended catheter. Once the stone is visible, endoscopy and fluoroscopy are used to decide how it should be removed. If stone is small it can be grasped with rigid forceps and extracted intact.
Fig. 3 : X-ray with Amplatz sheath in position. Fig.4 : Nephroscope. Larger stones require fragmentation before removal and various techniques are available - electrohydrolic, ultrasonic and laser lithotripsy.
Electrohydraulic is a bipolar probe that creates a spark when fired, which will vaporize liquid, producing a gas bubble and shock wave that fragments the calculi.
Ultrasonic lithotripsy uses mechanical vibrations at a frequency above 17 cycles/Sec or 17 KHZ. Vibrations are created by applying alternating current to a ceramic crystal which then expands and contracts; this vibration is transmitted to the tip of probe where it causes formation of bubbles and produce cavitation on contact with stone. Suction on the back of the probe removes small fragments. Ultrasound probe does not damage renal tissue if it accidentally touches it. These probes are rigid hence cannot be used with flexible instruments.
Laser lithotripsy : Recently Holmium laser has been used to fragment stone, due to its cost it is not used in all the centres. Laser is capable of fragmenting even the hardest calcium oxalate monohydrate and cystine calculi.
Fig. 5 : Endoscopic view of pelvic stones. In some cases where the stone is large or has extension into different calyces than additional tract may be required in about 15% of cases. Multiple tracts help to achieve stone free Kidney.
Final steps
By fluoroscopy and nephroscopy the pelvicalyceal system is checked for residual fragments and once all the stones are removed, a malecotts catheter 24 or 26 F passed through Amplatz sheath as a nephrostomy. Nephrostogram is done after 48 hrs to check for residual fragment, extravasation and free drainage into the bladder. Nephrostomy tube is clamped and removed after 24 hrs. and patient is discharged the next day.
Complication
Meticulous technique is necessary to minimize the complication of PCNL. It is an invasive procedure hence few recognised complications are seen, during the procedure Bleeding from renal parenchyma occurs to some degree due to extremely vascular nature of the kidney, about 2-5% of patients may need blood transfusion. Perforation/Extravasation is seen but major perforation are unusual. Most occur after inadvertent over advancement of dilators or sheath. Contiguous Organ Injury : Damage to various organs including liver, spleen, duodenum or colon is reported in less than 1% of cases and is very rare. Infection, fever or urosepsis is minimized by routine prophylaxis with broad specturm IV antibiotics.
CONCLUSION
Percutaneous nephrostomy tract offers access to kidney in much the same way as urethra to the bladder. Endourological procedure have reduced the number. of open surgical procedures performed on kidney for stone removal. PCNL have been able to reduce the length of hospital stay, cost and morbidity allowing the patients to return to work early.
 |
