(1)
Surgery, University of Melbourne, Parkville, Victoria, Australia
Introduction
The kidney is a solid mobile organ with a profuse blood supply and a relatively thin poorly supported collecting system.
Anatomical Factors Related to PCNL Complications
The Kidney
The kidney is a solid fragile organ that easily splits.
The kidney is a pedicled organ, surrounded by fat. As a result, it is very mobile in all directions.
The lower pole of the kidney lies anterior to the upper pole due to its relationship to the psoas muscle behind.
Hence, it is easily displaced forwards by needle puncture, track dilation and endoscopic manipulation.
Following previous surgery or urinary extravasation, the kidney parenchyma, capsule and collecting system can become rigid, fixed and more “brittle”.
Hence, previously operated kidneys are harder to dilate and more prone to split and tear during dilation and nephroscopy.
As a result, kidneys that have undergone previous open or percutaneous surgery are more prone to injuries of the collecting system, segmental vessels and parenchyma during PCNL.
Blood Supply
Twenty per cent of the body’s circulation flows through the kidneys at the rate of one litre per minute.
The wide bore renal arteries divide anteriorly and posteriorly with the posterior supplying the upper pole. They form segmental arteries before entering the renal substance.
The renal segments or renules are supplied by these segmental end arteries.
Damage to segmental arteries can result in infarction, severe bleeding, pseudoaneurysm or arteriovenous fistulae.
A well-planned radial incision, as used in a nephrotomy, will pass between the segmental supply and is almost bloodless.
Similarly, a properly placed PCNL dilates between segments rather than cutting vessels, so causing minimal renal damage.
The great vessels, e.g. renal vein, IVC, aorta and renal arteries, are in close proximity to the renal hilum and pelvis and so can be damaged during track dilation or nephrolithotomy.
The segmental renal venous drainage, unlike the end arteries, have a cross-circulation. Hence, intrarenal venous injuries are less damaging than arterial injuries.
Collecting System
The collecting system is:
Only connected to the parenchyma at the fornices.
Thin and so easily perforated or torn.
Less supported elsewhere, so the calyces, infundibulae and renal pelvis are all prone to direct damage and tearing.
Has small volume; the capacity of the average renal pelvis is less than 5 ml.
Muscular and if irritated, the pelvis and calyces will spasm, making radiological identification of a calyx particularly difficult or impossible in an unobstructed kidney. Hence, many emergency radiological nephrostomies enter through the renal pelvis rather than the tip of the calyx.
Access to the Kidney Is Blind
The surgeon cannot see the access track, unlike open or laparoscopic surgery.
This is a “foreign” concept for most urologists.
The puncture needle, guide wire, dilators and Amplatz sheath are inserted “blindly” using screening alone.
Radiological imaging is not a familiar skill for most surgeons and requires extensive education, training and practice.
Intrarenal Anatomy
The intrarenal collecting system is small volume and collapses easily, especially when suction is used.
As a result, it is difficult to aspirate or barbotage blood clot (unlike the capacious bladder).
The complex angulation of most calyces from the pelvis is greater than the curvature of most flexible nephroscopes.
As a result of this angulation, irrigation, instrumentation and laser lithotripsy are compromised when using flexible instruments, because the small irrigation and instrument channels are further reduced by angulation of the tip of the flexible nephroscope.
Consequently, the majority of nephroscopies for PCNL are still performed using rigid endoscopes. These provide optimal irrigation and a straight instrument channel for the deployment of powerful lithotrites and strong stone graspers.
Although the instruments are rigid, it is my experience that the smaller “mini perc” sheaths have increased intrarenal mobility than larger nephroscopes, particularly when the guide wire is external to the sheath.
As most calculi treated by PCNL are large and dense, it would seem that rigid nephroscopes are unlikely to be replaced in the near future.
Because the orientation and direction of the calyces prevent easy access to all areas from a single puncture, complex calculi require multiple access tracks. It is rare to be able to endoscope the entire collecting system from a single track.
Summary
PCNL has many unique potential complications. Most are anatomically based. Serious complications such as bleeding, splitting of the kidney and laceration of the collecting system in particular can occur abruptly.
They can also be anticipated by a history of previous surgery, or anatomical variations seen on the preoperative CT–IVU.
Like TUR prostate, but unlike open and laparoscopic surgery, PCNL is an operation that can be safely terminated and completed at a later date.
Therefore:
Don’t panic or resort to open surgery (unless absolutely indicated, e.g. catastrophic haemorrhage, dismemberment of the ureter).
Inform the patient during pre-operative consent that the PCNL may be terminated early for medical indications and completed at a later date.
If PCNL extends for more than 2 h, or surgical complications occur, particularly bleeding not controlled by irrigation, place a nephrostomy and cease the operation.
Anticipate complications. Have a “battle plan” to avoid and manage complications – each PCNL is unique and should be planned carefully with particular attention to previous history and anatomy of the patient, perirenal structures, the kidney and the stone.
Always be prepared to return another day.
Complications Related to the Nephrostomy Puncture
Guide Wire Kinking During Dilation
Avoid!
I only use hydrophilic guide wires as they do not kink and can be held by artery forceps without damage to the wire.
However, some surgeons find hydrophilic wire more difficult to control as the wires are slippery to hold and prone to “springing out” if not carefully controlled.
If using a coiled metal guide wire, it is critical at every stage of the dilation that the dilator and guide wire be parallel with each other to avoid kinking of the guide wire.
If a metallic guide wire does kink, it is usually very difficult or impossible to continue with the dilation using that wire and so one needs to re-puncture.
However, it is always worth trying to pass a 6 Fr fascial dilator over the wire. This may enter the kidney and allow the wire to be replaced without re-puncturing.
Alternatively, sometimes the wire can be advanced under screening so that the kink is inside the kidney or down the ureter – not often successful, but always worth trying before removing the wire.
Damage to Neighbouring Organs
Carefully review the preoperative CT–IVU to plan the puncture, to assess the proximity of neighbouring organs.
Bowel
Generally, the ascending and descending colon lies posterior to the kidney in about one in six patients, most commonly in relation to the left lower pole.
The specific procedures that are most commonly at risk of bowel perforation include the following:–
Horseshoe kidney (always puncture the lateral upper pole calyx)
Ectopic kidney
Kyphosis/scoliosis
Gastric bypass surgery
Previous open renal surgery
Distended colon
Transplant kidney
Needle Puncture of the Bowel
If one suspects a needle has punctured the bowel, aspirate.
If gas, it is almost certainly in bowel
If clear fluid is aspirated, this can be confusing, as it may be small bowel content or urine.
Infuse contrast and methylene blue through the ureteric catheter in the first instance to determine whether the needle is in the collecting system.
If no contrast is aspirated after RGS infusion, inject a few millilitres (only) of contrast through the puncture needle under II screening to assess whether it is in bowel.
If bowel is outlined, insert a guide wire through the needle sheath.
Leave the guide wire (avoids leaks and helps with the placement of the subsequent calyceal puncture).
Re-puncture into a calyx.
Remove the original guide wire.
A single fine needle puncture of bowel that has not been dilated rarely compromises the PCNL or requires treatment.
Gas bubbles in the needle or through a nephrostomy track almost always herald a problem, either a bowel or pleural transgression.
Remember, “bubbles usually mean troubles”!
Always involve a colorectal colleague if there is suspicion of a bowel injury.
Dilator Trauma to the Bowel
It is possible to complete an uneventful PCNL unaware that the procedure has been performed through a colonic perforation. I find significant bowel injuries are not common, particularly with helical CT, the surgeon should always be prepared for (and can usually avoid) the complication by planning the track or opting for an alternative approach such as FURS. The injury can be diagnosed at various stages:
During track dilation
At the end of the PCNL
Delayed – usually within 24–48 h
During Track Dilation
The colon is mobile and has a tough muscular serosa. As such, the “capsular give” sensation is different when the PCN needle perforates the colon. It seems to require more effort, is prolonged and gives a sensation of “thickness” – difficult to describe but simple to experience. This sensation arouses suspicion.
Usually, the needle has continued through to the targeted calyx, as the puncture is monitored by II. If colon’s perforation is unrecognised, then a guide wire is inserted into the kidney and dilators introduced.
If using serial dilators, bubbles may exit from the track between dilators. If so, reinsert the dilator, place an Amplatz sheath, and endoscope the track. I have found that even a small colonic perforation is easily recognisable endoscopically. A cannula can be fed into the colon through the nephroscope and contrast infused to confirm the diagnosis radiologically. My corresponding colorectal surgeons are adamant that firstly, as the perforation is extraperitoneal, it will settle without exploration and secondly, the drain (e.g. Yeates) should be placed alongside the colon, but not through the perforation, to avoid the development of a cutaneous fistula.
At this stage, the PCNL is terminated. If no bubbles appear, one may still be suspicious during dilation, as the dilators often displace rather than perforate the bowel as the bowel musculature is thick. This can be suspected by renal displacement during imaging. The management is the same as for “bubbles”, i.e. endoscopy of the track.
Recognition of Perforation at the End of the PCNL
This diagnosis is generally made on the post-PCNL nephrostogram after or when placing the nephrostomy.
The principles of management are to:
Involve your colorectal colleague.
Explore the abdomen if there is any suggestion of intraperitoneal leak (e.g. on imaging).
If the injury appears to be extraperitoneal, separate the bowel and urinary drainage and manage conservatively.
Colonic injuries are rare, variously quoted around at about 1 % of PCNLs.
As a result, experience is limited and so approaches differ. Most agree that a double J stent should be placed into the kidney to create a “tubeless” nephrostomy. The question as to how the bowel diversion is managed I believe should be made by the colorectal surgeon. The team I work with do not favour a tube, such as a Cope nephrostomy, diverting the colon. They prefer a drain alongside the colon. They believe this decreases cutaneous fistulisation from the bowel and assists with closure of the enterotomy. Others recommend a colonic tube. Hence it is essential to have a close working relationship with your corresponding surgeon and manage the patient together.
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