Genitourinary Interventional Radiology

Percutaneous Renal Access

The safest point for calyceal puncture is the centre of the calyx, approached through the relatively avascular plane (Brödel's line) between the branches of the anterior and posterior divisions of the renal artery
Puncturing the centre of the calyx avoids injury to the arcuate divisions that course around the infundibulum – puncture into the infundibulum or renal pelvis may lacerate larger arterial branches
A further potential hazard is the posterior renal artery division (the only major division lying posterior to the collecting system) ▸ typically it lies behind the upper renal pelvis but is occasionally behind the upper pole infundibulum (where it can be injured by an infundibular puncture)
Typically the upper and lower pole calyces are fused (therefore larger and easier to access
The posterior calyx is ideal for access (closer to the skin surface) and also allow better intrarenal navigation (access to the PUJ is easier from an interpolar or upper pole calyx)
Upper pole access may require an intercostal entry

Two-part 21G needle system (micropuncture access system): puncture with a 21G needle through which a 0.018 inch platinum tipped wire is inserted, followed by a 4Fr dilator and finally a 0.035 inch working guidewire ▸ smaller puncture site
One-part 18G 4Fr sheath system: 18G diamond point needle, over which a 4Fr sheath and the whole is inserted as a single unit

A soft flexible with good torque to navigate out of the calyx (rigidity less vital) – e.g. a straight tipped Bentson wire
Once out of the calyx and into the renal pelvis / ureter, rigidity becomes more important (e.g. stiffer Amplatz type wire) ▸ a stiff shaft hydrophilic wire is less prone to kinking than other wires

Navigation: a short angled-tip (e.g. Kumpe) or Cobra shape high torque catheter is best ▸ hydrophilic catheters are useful for bypassing tight ureteric strictures
Drainage: a pigtail catheter with large side holes ▸ a pigtail may not easily form in a small renal pelvis

Indications: urinary tract obstruction ▸ pyonephrosis ▸ urinary leakage / fistula / access for interventional or endoscopic procedures
Data suggest that PCN and ureteric stents are equally effective
No absolute contraindications (severe coagulopathy is a relative contraindication) ▸ in patients with a limited life expectancy a nephrostomy should only be inserted only if it leads to improved quality of life and survival
INR < 1.3 ▸ platelets >80,000/dL ▸ antibiotic prophylaxis
Technique
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  Prone / prone oblique position ▸ performed under monitored sedo-analgesia + local anaesthetic infiltration down to the renal capsule
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  Following appropriate puncture of an appropriate calyx, urine is aspirated to confirm position ▸ contrast medium (10 ml) injected to confirm puncture site if there are no signs of sepsis ▸ overdistension should be avoided to avoid bacteraemia ▸ if the puncture site is suitable, a wire is inserted and the tract dilated for catheter insertion
Nephrostomy removal should be performed under fluoroscopic guidance using a guidewire

posterior calyces are the most superficial and medial with the patient lying prone

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