Performing a percutaneous kidney biopsy

Table 2 Technique considerations in performing percutaneous kidney biopsy

Biopsy step	Technical point
Ultrasound views	Guidance using a short-axis (‘out-of-plane’) view is uncommon because of poorer needle tracking, although results were similar between short- and long-axis approaches in observational studies[39]
	A short-axis window might be helpful, for instance, in situations where biopsy is performed laterally from the patient’s flank or where a vertical needle trajectory is used
Positioning	The prone position is almost universal for percutaneous kidney biopsy. It is comfortable for patients and ergonomic for the proceduralist
	Less common positions include seated or lateral decubitus. Retrospective reports showed kidney biopsy to be safe and effective in these alternative positions[40-42]
	In exceptional circumstances like pregnant or mechanically ventilated patients, any position deemed to optimise tolerability and needle view on ultrasound can be used[43]
	The biopsy may be performed with the patient’s breath held in either of inhalation or exhalation in order to facilitate a safe path to the kidney
Needle insertion method	There are two needle systems that are commonly used for percutaneous biopsy: A freehand technique, as described in the main text, or a coaxial technique
	In the coaxial method, a hollow trocar needle is advanced to the kidney and its tip placed at the renal capsule. The thinner needle of a spring-loaded biopsy gun can then be introduced repeatedly through the trocar as required
	Possible advantages of the coaxial method include consistency when needle visualisation is difficult, less soft tissue trauma, and the ability to inject haemostatic pledgets to seal the biopsy tract. An advantage of the freehand method is flexibility to redirect the needle trajectory with each pass
	In a trial of 166 patients randomised to a coaxial or non-coaxial needle technique, there was a higher average yield of glomeruli (18 vs 9, P < 0.01) and a significantly shorter procedural time (5 minutes vs 14 minutes, P < 0.01) in the coaxial group, but no differences in the rates of major haemorrhage or in the likelihood of positively determining a diagnosis[44]
Needle trajectory	The trajectory of the biopsy tract and needle must account for the kidney’s anatomy, movement with respiration, and closeness to surrounding organs
	The needle tangent should ensure that the biopsy throw length remains entirely in renal cortex, minimizing the likelihood of inadvertently puncturing hilar vessels or medulla
	The main text outlines the most common approach to the kidney lower pole cortex. Various alternative trajectories are also possible, with no high-quality data favouring any specific approach
Laterality	The left kidney is more frequently biopsied than the right
	The right kidney can be obscured by overlying liver
	Where embolisation is required for biopsy-induced haemorrhage, trans-arterial selective catheterisation of the left renal artery is anecdotally easier than the right
	Comparative studies are absent