™ Patient is placed in the prone position with padded support underneath the abdomen, chest and elbows.
™ Anatomical window for puncture of the kidney: cranially, inferior costal margin of 12th rib; caudally, iliac crest; medially, paravertebral musculature; laterally, posterior axillary line (lateral abdominal wall).
™ Puncture is directed either with ultrasound or radiographic guidance into the lower calyx with an 18-gauge needle. The access is completed using the Seldinger technique.
™ Ultrasound is performed to delineate the PCS and ascertain the exact location of the upper, middle and lower calyces. The ultrasound probe has an incorporated needle-guiding facility to direct the puncture into the desired target area.
™ Alternatively, radiographic guidance with the aid of a C-arm can be used to achieve access to the PCS. Retrograde pyelography via the ureteric catheter is performed to delineate the calyx. One dimensional radiographic access is extremely cumbersome and thus not recommended.
™ Advantages of lower calyceal puncture:
™ Stone fragments can be removed from the lower calyx where they are most likely to collect.
™ The calyx and the infundibulum offers a favourable axis for the passage of the rigid nephroscope into the pelvis.
™ In calyceal diverticular stones: puncture directly into the diverticulum. ™ Stones in middle or upper calyx (see operative tips).
™ Guidewire is placed well within the renal pelvis or even into the upper calyx if possible.
™ Insert the guiding rod coaxially to the guide-wire and avoid kinking of the guidewire.
™ Establishment of the working tract is achieved by progressive dilatation with the aid of concentric metal serial dilators.
™ Dilatation under radiographic guidance prevents perforation of renal pelvis.
™ Finally, the sheath of the nephroscope is advanced into the renal pelvis. Be aware of risk of perforation since there is no resistance to the advancing nephroscope.
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