PERCUTANEOUS NEPHROLITHOTRIPSY (PCNL)
MADHU S AGRAWAL
Associate Professor and Consultant Urologist, Urology Division, Department of Surgery, SN Medical College, Agra.
Management of nephrolithiasis has been revolutionized by the advent of shock-wave lithotripsy and percutaneous nephrolithotomy. Percutaneous nephrostomy was a procedure known since 1955 (Goodwin et al). However, it was not until 1976 when the first percutaneous nephrostomy for the specific purpose of removing a kidney stone was performed by Ferstrom and Johannson. Over the next few years, Smith and colleagues at the University of Minnesota, Alken and Marberger in West Germany, and Wickham and colleagues in the United Kingdom, began to remove selected stones in the renal pelvis and ureter through percutaneous nephrostomy tracts. By the early 1980s, it was apparent that it was possible to remove renal stones safely and reliably percutaneously, not only through a previously made PCN tract, but also as a single procedure with considerably shortened period of hospitalization (Segura et al, 1983).
The management of staghorn calculi continues to be somewhat challenging. The most widely accepted choice at the present time appears to be a combination of SWL and PCNL, what has been called the ‘sandwich therapy’. At our centre, which is fully equipped with facilities for both endourology and SWL, the standard policy for staghorn calculi is PCNL ‘monotherapy‘. All attempts are made to clear the stone completely endourologically only, in more than one session if needed, reserving SWL to situations where the stone can not at all be removed by PCNL.
TECHNIQUE OF PERCUTANEOUS STONE REMOVAL
The procedure may be divided into two parts : A) access into the collecting system and B) removal of the stone.
The excretory urogram or retrograde pyelogram should be reviewed to determine the relationship of the stone to the collecting system and to determine the optimum access tract. The retroperitoneal location of the kidney permits access through a posterolateral "window". Access should be performed under fluoroscopic or ultrasonic control.
Optimum access is generally through a lateral calyx, one of the lower polar calyces in most instances. If the goal is a caliceal stone or a diverticular stone, access should be through that particular calyx or diverticulum. Approach through the upper polar calyces is useful for access to the pelvis and UPJ, but the risk of pleural injury is significantly increased.
The procedure is mostly done under epidural, spinal or general anaesthesia, but can be done under intravenous sedation and local anaesthesia as well. An 18-gauge needle is placed through the flank into the kidney at the point where access is desired. A guide wire of 0.035 or 0.38 size is passed through the needle. It is very desirable that this wire be placed down the ureter as far as the pelvic ureter in order to minimize the possibility of inadvertent loss of the tract.
The tract is enlarged by passing serial or telescopic Teflon or metal dilators co-axially over the guide wire. Dilatation proceeds under fluoroscopic control to 30 Fr and an Amplatz sheath is passed over the last dilator, to provide direct access to the collecting system. The nephroscope is passed through the sheath to visualize the inside of the collecting system.
B) Stone Removal
Small stones can be removed intact with forceps or basket. More commonly, some form of power lithotripsy is required to break the stone into manageable fragments. The options available now are, ultrasonic lithotripsy, electrohydraulic lithotripsy, and pneumatic lithotripsy. Whatever the choice of energy source, the action of the probe is that of a "jackhammer", battering the stone into progressively smaller pieces (Fig. 1). The pieces are removed as they are broken up. Stone removal continues until the patient is free of stone or until it is necessary to stop the procedure. Common reasons for this include progressive bleeding which obscures the surgeon’s vision so that the rate of stone removal is considerably slowed, and extravasation of irrigating fluid.
If the patient is not free of stone at the termination of the procedure, the nephroscope can safely be reinserted through the same tract after 48 hours. At this point, the tract is matured and bleeding has almost always stopped, so that removal of residual fragments is usually straightforward. As the size of the stones and complexity of these situations increase, the odds rise considerably that a second and occasionally a third treatment will be required.
At the end of the procedure, a nephrostomy tube is placed through the tract into the collecting system, large enough to maintain an adequate tract to permit blood and clots to drain readily. After 48 hours, a nephrostogram is obtained. If there are no leaks, the nephrostomy tube is clamped. If the patient tolerates this procedure, the tube is removed and the patient is discharged from the hospital. The drainage site will usually close within 24 hours. Time of disability varies; most patients return to average activity levels within a week or so. A return to vigorous activity should probably take place in another week
Indications for PCNL
Since the availability of extracorporeal shock wave lithotripsy, it has become the treatment of choice for small and medium sized uncomplicated stones. Following over a decade’s experience with ESWL, which has allowed better understanding of its usefulness and limitations, the indications of PCNL have been redefined.
1. Stone size (staghorn calculi)
Although it is possible to treat large stones with shock wave lithotripsy, the high retreatment rates and the high residual stone rates make such treatment unattractive (Lingeman et al, 1989). PCNL is particularly effective with such stones because of its ability to remove large volumes of stone material over a relatively short period of time. For this reason, if the stone is 2.0 to 3.0 cm or more, PCNL is preferred, especially if other factors may compromise the utilization of shock wave lithotripsy (Table 1).
AUA nephrolithiasis clinical guidelines (1994)Treatment recommendations for calculi in non-dilated non-obstructed adult collecting systems
Stone size Surface area Treatment Exceptions >1 cm <100 mm2 SWL - 1.1- 2 cm
PCNL for cystine calculi, lower caliceal calculi
2.1 - 3 cm
500-1000 mm2 PCNL SWL for soft calculus in pelvis or upper pole >3cm > 1000 mm2 PCNL -
Staghorn calculi constitute a special problem that has always tested surgical abilities. Most staghorn stones are composed of struvite, although stones composed of uric acid, calcium oxalate monohydrate, and especially cystine occasionally fill enough of the collecting system to give it a staghorn appearance, Because most staghorn calculi are composed of struvite, they are infected, and as such no substitute exists for complete removal. This was true when all such stones were treated by open surgical removal, and it is true now. Failure to achieve complete stone removal allows the persistence of infection and the eventual re-growth of the stone.
Although struvite staghorn stones are usually managed by a combination of PCNL and shock wave lithotripsy (Table 1), excellent results can be achieved by percutaneous means alone, with stone-free rates of 85 to 90 per cent in experienced hands (Patterson et al, 1987). In our own experience, PCNL monotherapy has proved to be both feasible as well as cost effective for staghorn calculi (Table 2).
Our experience with staghorn (Large, Branched) calculi
No. of cases : 276 (233 Pts.) Age : 9-71 years Sex : M:F = 1.8:1 Complete clearance : 259 Residual fragments : 17 ESWL : 10 Medical treatment : 7 Complications Major (mortality, loss of kidney) : Nil Minor (Pyrexia, haematuria, transient leak) : 42
2. Obstructive Uropathy
If an anatomic abnormality is present that will prevent stone fragments from passing spontaneously, shock wave lithotripsy is usually contraindicated. These situations are ideal for PCNL, inasmuch as the obstructive uropathy can also be corrected after stone removal employing endourological procedures. Ureteropelvic junction (UPJ) obstruction may coexist with calculi in the collecting system. Such stones are best removed by percutaneous means because the obstruction can be treated by endopyelotomy, usually at the same time.
Clinical diverticula often contain stones, and their connections to the collecting system are usually such that broken fragments after shock wave lithotripsy will not only remain in the diverticula but the obstructive uropathy will remain untreated. Management of diverticular stones by PCNL with enlargement of the connection to the collecting system or obliteration of the diverticulum by electrocoagulation is the usual treatment today.
3. Anatomic Abnormalities
In very obese patients, or in patients with skeletal abnormalities like severe kyphoscoliosis, shock wave lithotripsy is impossible because the stone cannot be placed in the focal point of the machine. Percutaneous removal will be possible if the distance from the skin to the stone is less than the length of the nephroscope or the sheath.
4. Stone Location
Stones located in the lower pole calyces are less likely to pass after shock wave breakup, particularly if the collecting system is grossly dilated or otherwise abnormal. If it is important that all fragments be removed, PCNL is probably preferable.
5. Stone Composition
Struvite stones should be treated with PCNL in order to be sure that all the fragments are removed. Stone composition is otherwise an important consideration due to the fact that with ESWL hard stones will frequently not fragment into pieces small enough for spontaneous passage with minimal discomfort. This same hard stone may be equally difficult to remove with power lithotripsy after percutaneous access, but it will be possible to remove the pieces via PCNL, irrespective of how difficult it was to break up the stone.
The commonest hard renal stones are composed of calcium oxalate monohydrate. As these stones become larger, the more likely it is that multiple shock wave lithotripsy treatments or other instrumentation may be necessary. One should consider that it might be more cost-effective and actually less morbid to remove these stones with PCNL.
6. Certainty of the Final Result
Residual stones are not acceptable for many patients. The most common example is the commercial airline pilot. However, many people find themselves considerably inconvenienced, for whatever reason, by the uncertainty as to whether a small fragment might pass. The very high stone-free rate after PCNL makes this method an ideal choice for such people.
7. Other Modality Failure
As mentioned, shock wave lithotripsy may fail or ureteroscopy may fail. Equally, stones may remain after an open surgical procedure. PCNL may retrieve these otherwise lost procedures.
Contra-Indications of PCNL
The only absolute contraindications for PCNL are uncorrected bleeding disorder and pregnancy (due to the risk of radiation). The other relative contra indications which may be considered are, medical problems making the patient unsuitable for anaesthesia, and, stone location making access risky, (e.g., pelvic kidney), By and large, the procedure is possible in majority of the patients, including those considered unsuitable for the other modalities like open surgery and shock wave lithotripsy.
The advent of shock wave lithotripsy has changed the definition of what constitutes a successful result. Considerable discussion has occurred about "clinically insignificant residual fragments" ("CIRF"), referring to broken up fragments of various sizes and their propensity for spontaneous passage. Because of a lack of unanimity as to the precise definition of CIRF, a consensus has emerged that the only true definition of success is a stone-free state. This point is an important consideration in measuring the effectiveness of PCNL against other methods of stone management.
If results are restricted to the best selected patients, i.e., those with the least difficult stones to access, stone-free rates of 98 to 99 per cent can be achieved (Brannen et al, 1985; Lingeman et al, 1989; Segura et al, 1985; White and Smith, 1984). As the size of the stone increases, and as the complexity of the situation increases, the stone free rate drops to 75 to 80 per cent. Better results are achievable with greater effort, and it becomes a matter of judgement as to whether a given residual stone is worth the effort required to remove it.
COMPLICATIONS OF PERCUTANEOUS STONE REMOVAL
As with any other surgical procedure, problems may complicate any aspect of the percutaneous stone removal. One may conveniently divide events into three groups : A) complications related to access (tract dilatation), B) complications related to stone removal.
A. Complications Related to Access
The ultimate success of the procedure is a function of adequate access. Poor tract placement may make safe, expeditious stone removal an impossibility. Prudence dictates that a sub-optimal access point should be changed prior to dilatation and lithotripsy.
The retroperitoneal position of the kidney permits access through a percutaneous window that enables entry into the kidney without trauma to adjacent peritoneal structures. Pathologic states and variations in normal anatomy may result in situations in which damage to adjacent organs can occur. Injury may occur to the adjacent organs, like spleen, pleura (specially in cases of supra-costal puncture), peritoneum, colon or duodenum rarely.
Renal trauma : Optimum access traverses the bulk of the thickness of renal parenchyma to enter the collecting system through one of the calyces. Placement of the tract in a line too medial or too lateral may tear the parenchyma. The pedicle or other large branch vessels may be injured if the access tract enters the collecting system medial to the calyces or if the tract goes beyond the collecting system inadvertently. Proper placement of the tract through the calyx and infundibulum and into the renal pelvis minimizes the risk of such injury.
B. Complications Related to Stone Removal
Problems at the time of stone removal may be related to bleeding, extravasation, inadvertent perforation of the collecting system, incomplete stone removal and sepsis.
Although a small amount of bleeding may occur all throughout the procedure, significant blood loss may complicate the situation at any time. The most common type of bleeding is venous, which may be compared with the sinus bleeding that occurs with transurethral resection of the prostate. This can be managed by clamping the nephrostomy tube for 30 to 45 minutes. This step allows a clot to form in the collecting system, tamponading the bleeding.
Arterial bleeding is a more serious problem. This may occur during the procedure (primary) but also may occur in the postoperative period up to a week or 10 days (secondary). In these cases, arteriography will confirm the diagnosis, usually revealing a pseudo-aneurysm, and will also permit embolization of the offending artery. Surgery should be avoided if possible, as at exploration nephrectomy or partial nephrectomy may appear the only alternatives. Most large series report an incidence of this problem less than 1 per cent.
Normal saline should be used as the irrigation fluid to minimize adverse effect when extravasation occurs. When an Amplatz sheath is employed, most of the irrigation fluid travels out the sheath, rendering extravasation less likely. Despite the technical details, the operating personnel should monitor the quantity of irrigation fluid used and compare this amount with the quantity in various collecting bags. Discrepancies that cannot be accounted for should suggest the possibility of extravasation.
Retroperitoneal extravasation is inevitable if the collecting system has been perforated. If the perforation was identified when it was made, it may be possible to complete the procedure by rigorously controlling the amount of irrigation. Sometimes, retroperitoneal extravasation may not be obvious unless it is noted that the kidney seems to be moving "away" from the flank and that the nephroscope must be placed farther in to access the stone.
3. Retained Fragments
As in any method of stone management, the presence of residual fragments on a post-procedure plain film can be an unwanted finding. Reinsertion of the nephroscope through the tract, kept open by the nephrostomy tube, will permit removal of the stone fragments. Sometimes stones are extruded through the collecting system or are noted in the perinephric tissues outside the kidney. It is not necessary to remove these stones, as experience has shown them to be clinically unimportant. Their main import has been to generate confusion on subsequent plain abdominal radiographs.
4. UPJ Obstruction
Occasionally follow up studies show partial or complete UPJ obstruction resulting in progressive dilatation of pelvi-calyceal system. This may be either due to pre-existing obstruction missed at the time of operation, or may be the result of trauma to UPJ during surgery. The incidence is greatest in cases where the stone was impacted at the UPJ.
Many patients experience a rise in temperature after stone removal, although true sepsis is rare. Preoperative urine culture results will identify the patient who should be treated prior to the procedure. Special attention should be paid to those patients with infected stones. It is usual to provide a prophylactic antibiotic cover, using a broad-spectrum antibiotic that covers the common uro-pathogens for these patients.
Percutaneous surgery is an effective and safe method for the management of a wide variety of renal and ureteral stones. Today, it is selected mainly in certain specific situations in which the result justifies its invasive nature. Recognition of which patient can benefit from the procedure minimizes the number of other less successful attempts at stone removal and optimizes the chance that the problem will be managed safely, expeditiously, and economically.
PCNL as the primary treatment for staghorn renal calculi offers the twin advantage of minimally invasive therapy and complete stone clearance. With a little motivation and extra effort, majority of these cases can be completed by PCNL alone, reserving secondary ESWL for really inaccessible calyceal calculi. This helps in shortening the overall treatment duration and significant saving in costs as compared to sandwich therapy.
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