Treating urological conditions

Target zone:

The renal arteries and renal veins enter the kidney at the renal hilum and divide into larger anterior and smaller posterior divisions passing around the renal collecting system. The least vascular zone, and therefore the safest area, lies within the arc shown – aka Brödel's avascular line ( Fig. 41.1 ). Posterior calyces in the mid and lower pole are the best target and provide the most favourable approach for intervention. Direct puncture of the renal pelvis should be avoided, as this increases the risk of major vascular injury and persistent urine leak. Puncture of the upper pole calyces is only necessary for nephrolithotomy and is associated with a significant risk of pneumothorax ( Fig. 41.2 ). Avoid anterior punctures; in addition to providing the least favourable access and causing renal haemorrhage, you may well traverse the colon, liver or spleen.

Ultrasound-guided puncture:

Ultrasound guidance is by far the easiest and safest technique. It is easy to be anxious to get to the needlework, but take time at the start to get the ultrasound just right. If you have not read the section on ultrasound-guided punctures ( Ch. 26 ), then read it now, if nothing else!

• 1.

  Before all the drapes are applied, scan the patient in either a prone or a prone/oblique position, aiming to find a posterolateral approach to target a posterior interpolar calyx. Mark the potential site of entry on the skin and remember you are aiming at a posterior calyx so the puncture should only traverse the retroperitoneum – that's at the back of the patient! If the puncture is very lateral or even anterior, look for a better window.

• 2.

  Drape the patient, infiltrate local anaesthetic along the needle track and make a 5-mm skin nick with a scalpel. Advance the puncture needle under continuous ultrasound guidance. When the needle tip reaches the calyx, advance it 5–10 mm with a darting motion. There may be a sudden ‘give’ as the calyx is entered. Apply gentle suction while slowly withdrawing the needle; aspiration of urine indicates entry to the system. Do not completely decompress the system, as it makes subsequent wire and catheter manipulation more difficult.

• 3.

  Inject a small amount of contrast to opacify the system and confirm the lie of the land.

Achieving drainage:

It seems nothing could be simpler now than to advance the nephrostomy drain into position, but many procedures go wrong at this stage and frustrating hours can then be spent trying to puncture a now undilated system.

• 1.

  If you are using a coaxial set (e.g. Neff/AccuStick), initially introduce the 0.018-inch wire, ensuring the soft leading section (the most radio-opaque section on fluoroscopy) is completely within the pelvicalyceal system. The support from the stiffer section of the wire is needed to advance the coaxial dilator system. Exchange the needle for the coaxial dilator system over the guidewire. Remember the metal stiffener does not like corners and unlock the stiffener at the point of entry into the calyx to support advancing the plastic sections.

• 2.

  Remove the inner plastic dilator and leave the 0.018 inch wire in place – this is your safety wire.

• 3.

  Using fluoroscopy, introduce the 0.035-inch guidewire parallel to the 0.018-inch wire, this should advance without resistance. If you are lucky, the wire will pass straight down the ureter but often it will pass into an upper pole calyx or coil in the renal pelvis (see Troubleshooting , below).

• 4.

  Advance dilators over the 0.035-inch guidewire to 1F larger than the drain. Leave the dilator in place on the wire to tamponade the track.

• 5.

  In an uninfected system, a 6F nephrostomy catheter is adequate, but pus requires at least an 8F drain for satisfactory drainage. Advance the nephrostomy drain until the tip is just within the ureter, then withdraw the wire to form the pigtail.

• 6.

  Inject a small amount of contrast to confirm your position.

  Alarm

  Never over-distend an obviously infected system with contrast. This is a sure way to give the patient septicaemia.

• 7.

  If the catheter is a locking pigtail, secure the catheter via the locking mechanism. Some centres also secure the catheter in position with either an adhesive dressing or a suture. Make sure that the catheter is firmly attached or you will be replacing it later!

• 8.

  Remove the safety wire once position is confirmed and the drainage catheter is secured.

• 9.

  Finishing off : remember when documenting the procedure to highlight if you have used a locking pigtail catheter, this is important when removing the drain.

Alarm

Removal without releasing the locking mechanism is painful and can disrupt the pelvicalyceal system or fracture the catheter. Finally, hopefully this catheter will be removed, and in addition to releasing the lock, make sure that the nylon suture does not get left behind when the catheter is withdrawn, as it can act as a nidus for infection or stone formation.

Unless you have performed an immaculate puncture, a formal nephrostogram should be left for 24 h, as blood clot can simulate stones or tumour.

Aspirate the drainage catheter:

• Pus: completely decompress the system

• Blood – rosé-coloured: connect to drainage bag

• Blood – claret-coloured: lavage with normal saline until it clears to rosé.

Difficult visualization:

Optimize the ultrasound; spend time looking for a good acoustic window before you start.

• Use a suitable probe: 3.5–5 MHz is best for nephrostomy

• Use the best ultrasound machine available.

Aspiration of urine but cannot advance guidewire:

The needle/sheath is sitting against the wall of the calyx. Do not use force as the calyx can be perforated. Very gently inject a little contrast to outline the position and carefully retract the needle/sheath and advance the guidewire.

Wire passes into the renal pelvis or an upper pole calyx:

Use a Cobra catheter and hydrophilic wire to direct it into the ureter. If there is a proximal ureteric obstruction, allow the wire to coil in the renal pelvis to improve your purchase.

Unable to advance dilators/drainage catheter:

Check the skin nick. Have you passed the needle through it? Is it large enough? Enlarge the nick as required.

The guidewire has kinked:

The wire most often kinks either at the skin surface or at the renal cortex. If you have inserted enough wire into the ureter or renal pelvis, it will be possible to withdraw the wire until the kink is outside the skin. If there is insufficient wire, advance a 4F dilator into the renal pelvis, this will usually pass over the most kinked wire. Exchange for a new stronger wire and this time do not let the wire ride forward during catheter insertion. Rarely, a stronger wire than the heavy-duty J-wire is needed. Steer a 4F catheter into the ureter, then gently insert an Amplatz wire.