PERCUTANEOUS NEPHROSTOMY
A percutaneous nephrostomy is a drainage catheter (a small plastic tube) that is inserted into the urinary collection system of the kidney and creates a direct connection between the kidney and the outside of the body, allowing the urine to flow outside the body.
WHEN IS IT INDICATED?
Obstruction of the urinary tract: percutaneous nephrostomy is indicated in all those cases in which there is a blockage to the passage of urine along the normal excretory tract. In these cases, hydronephrosis occurs (urine accumulates in the kidney, dilating it and causing pain) and the kidney suffers, up to the total and irreversible loss of its functionality. It is therefore necessary to protect the kidney and allow it to continue to function, and this can be done by discharging urine outside though a nephrostomy. Urinary obstructions are most commonly determined by stones or tumors, but they can also occur following injuries of the urinary tract (accidents, surgery), with subsequent scarring and obstruction, usually affecting the ureter.
Inflammation or infection of the kidney: A nephrostomy may be performed to remove pus or otherwise infected material from one kidney (usually coexisting with urinary tract obstruction).
Renal pelvis injury. A nephrostomy allows urine to be collected externally, rather than flowing out of the kidney through the lesion, thus contributing significantly to the healing of the lesion.
Urinary tract protection in case of ablative treatments (minimally invasive treatment of kidney tumors, with radiofrequencies, microwaves or cryoablation): if necessary, a nephrostomy is placed in the kidney to be treated to have access to the urinary tract in case of need (e.g. lesion of the renal pelvis), and possibly to carry out continuous irrigation which reduces the risk of complications on the excretory tract.
WHEN IS IT CONTRAINDICATED?
The only real contraindication is an uncorrectable coagulopathy, i.e. a state of impaired coagulation that increases the risk of haemorrhage and cannot be corrected, not even for the time necessary to perform the procedure.
This contraindication, however, can be considered relative and not absolute, and therefore a nephrostomy can and must be placed in all those cases in which the risk of not performing a nephrostomy is greater than the risk of a possible haemorrhage, for example a state of severe urosepsis, i.e. a generalized inflammation starting from the kidney, where drainage of the kidney is mandatory for the resolution of the infectious/inflammatory condition, in the face of potentially fatal consequences.
If possible, however, an INR ≤ 1.5 and a number of platelets ≥ 50,000 are always preferable.
WHAT TO DO BEFORE NEPHROSTOMY
As far as the doctor is concerned, it is obviously mandatory to review all the available imaging tests and the patient's medical record (indications, anatomy, procedure planning, evaluation of the complete blood count with coagulation structure, etc.).
For the patient are needed:
Fasting for at least six hours
Peripheral venous access
Antibiotic prophylaxis
Informed consent
HOW NEPHROSTOMY IS PERFORMED
The nephrostomy is performed in the angiography room, i.e. an operating room equipped with a radiological device that continuously delivers x-rays showing images of the body and surgical devices in real time.
Percutaneous nephrostomy is a procedure that is performed with the patient awake, conscious, under local anesthesia (with the injection of anesthetic only at the cutaneous access site and along the subcutaneous route to the kidney).
The patient is generally placed in the prone position (belly down), and only in exceptional cases on the side.
Ultrasound guidance is used for local anesthesia and the puncture of the kidney, after which fluoroscopic guidance (X-rays) is used for the subsequent steps.
The steps to follow for a nephrostomy are as follows:
1 - After the preparation of the surgical site, with adequate disinfection of the skin and using strictly sterile materials, as for any other surgical procedure, the ultrasound-guided injection of the anesthetic is performed from the skin to the kidney, along the subcutaneous route to the kidney.
2 - Subsequently, ultrasound-guided puncture of the inferior or middle caliceal group (the superior one is less preferable), at the level of the avascular plane of Brodel, the least vascularised portion of the kidney (to reduce the risk of haemorrhage). A very thin Chiba needle is generally used to minimize trauma and possible complications.
3 - The guidewire is then placed into the needle, the needle is removed and the catheter is placed over the guidewire. If a Chiba needle has been used, a plastic introducer is inserted on the first thin guidewire, a larger guidewire is then inserted in the introducer and eventually the nephrostomy catheter is positined over this larger guidewire (the guidewire that enters the Chiba needle is too thin and soft to support the nephrostomy catheter).
4 - Once the positioning and functioning of the nephrostomy have been checked, the catheter is fixed to the skin with a stitch or with specific devices and is connected to an external collection bag.
WHAT TO DO AFTER NEPHROSTOMY
Immediately after the nephrostomy the patient returns to the ward.
Some pain can be normal, but it is treated with simple painkillers and it is usually short-lived.
It is normal to find some blood in the urine drained from the nephrostomy into the collection bag, for 48-72 hours . The important thing is that it is not bright red blood, or that there is not only blood without urine.
In the 12-18 hours following the procedure, the patient should rest in bed, but can eat and move if there are no problems. Vital parameters are constantly monitored.
Blood tests are usually done 3 and 18 hours after the procedure, to make sure there is no bleeding and that everything is fine.
In the absence of complications, the patient can be discharged within 24 hours (i.e. after only one night of hospitalization), and can resume a normal life, obviously paying attention to the nephrostomy tube and the relative collection bag.
WHEN AND HOW IS NEPHROSTOMY REPLACED?
It is necessary to replace the nephrostomy every 90 days. The replacement procedure is simpler and quicker than the first placement, since the skin route already created for the nephrostomy to be replaced is used, without further punctures.
URETERAL STENT (DOUBLE J STENT)
A ureteral stent or double J stent (also just double J or JJ stent), is a small plastic or metal tube that is inserted into the ureter with one end in the kidney and one in the bladder. It serves to directly connect the kidney to the bladder, bypassing the ureter.
It's called double J because it has a curled shape at both ends that allows it to stay in place, without slipping up or down.
HOW TO PLACE THE URETERAL STENT
The ureteral stent can be positioned in two different ways.
Antegrade: from the kidney to the bladder, then from the top to the bottom. To do this, obviously, it is first necessary to access the kidney, with the same procedure that is performed for a nephrostomy. What changes is that the guidewire is advanced into the bladder, and the stent is then guided through the guidewire into the bladder, while the other end is released into the renal pelvis. In these cases, however, a nephrostomy is also positioned in the same kidney, to allow drainage of any blood and clots that can easily occur in an invasive procedure and which could occlude the stent. The nephrostomy left as a protection allows to verify when the urine is clear and to check, with the contrast medium and in the angiography suite, if the stent is working correctly. If so, the nephrostomy is removed and only the stent remains.
Retrograde: from the bladder to the kidney, then from the bottom to the top. It is a urological manoeuvre. The cystoscope is inserted into the bladder, the ureteral meatus is visualized and a guidewire is inserted up to the kidney, and on this the stent is positioned. This approach certainly has fewer peri-procedural risks than the anterograde approach (there is no need to puncture the kidney!) and therefore, whenever possible, it should be attempted first. If it is not successful, or there are no conditions to attempt this approach, then one can decide for antegrade positioning.
INDICATIONS
The double J stent has indications that partially overlap with nephrostomy and others that are specific.
Urinary tract obstruction. As with nephrostomy, placement of a double-J catheter is indicated for urinary tract obstruction, provided the stent can be passed through the obstruction.
Urinary diversion (urinary leak, fistulas). In case of damage to the urine collection and excretion system, the positioning of the double J allows to bypass the lesion point with a triple advantage: it allows urine to be collected in the bladder while maintaining the normal functionality of the system; it avoids spilling of urine outside the urinary tract; it allows for faster healing of the lesion.
Preoperative localization of the ureter - ureteral protection. One of the risks of pelvic surgery is the involuntary injury of the ureters. The preoperative positioning of the double Js allows the surgeon to locate the ureters more easily, even by palpation, since the ureteral stent is a small tube with a certain consistency that can be easily recognized even just by touching it. Furthermore, in the event of an injury, the stent is already in place, thus allowing for faster healing and avoiding further problems.
CONTRAINDICATIONS
If it has to be inserted with an antegrade approach, i.e. passing through the kidney, the ureteral stent has a contraindication in common with nephrostomy:
Uncorrectable coagulopathy. In this case, a retrograde approach should be attempted first if a ureteral stent is indicated. If this fails, or for various reasons it cannot even be tried, then an antegrade approach can be considered, if absolutely necessary.
Contraindications for ureteral stenting with any approach, antegrade or retrograde:
Untreated infections of the urinary system: the stent becomes infected, and is therefore a possible source of continuous infections, or does not allow the infectious state to resolve. If necessary, it can still be positioned, but it must be replaced frequently until the urinary infection is resolved.
All pathological conditions that do not allow spontaneous urination through the physiological way (the urethra): bladder fistula - neurological bladder - bladder outlet obstruction. The ureteral stent, in fact, allows urine to flow from the kidney to the bladder, but does not allow it to be discharged to the outside, like a nephrostomy. It is therefore necessary that the elimination of urine from the bladder is normal.
HOW AND WHEN SHOULD THE URETERAL STENT BE REPLACED?
The ureteral stent should be replaced every six months. The approach is from below, as for the retrograde placement. The old stent is hooked through the bladder, a guidewire is placed in it and reaches the kidney, and then the new stent is inserted over the guidewire.
COMPLICATIONS
Complications relate almost exclusively to nephrostomy and antegrade positioning of the ureteral stent, i.e. procedures involving percutaneous access and puncture of the kidney.
Major (4%)
Massive hemorrhage requiring surgery or arterial embolization: 1-3.6%
Sepsis: 1-2%
Pneumothorax: <1%
Death by hemorrhage: <0.2%
Peritonitis: rare
Minors (15%)
Macroscopic hematuria: very common, up to 48-72 hours
Pain: common, usually easily controllable with painkillers
Extravasation of urine: <2%
Perirenal bleeding: rare
Urinary infection: 1.4-21%
Catheter dislocation: 2% within the first month; up to 11-30% during follow-up
Catheter occlusion: 1%