Performing a percutaneous kidney biopsy

Table 1 Important considerations for kidney biopsy preparation

Checklist	Explanatory notes
Fasting	Patients should be fasted if procedural sedation is anticipated
	Practices vary and local protocols should be followed
Medical imaging	Urinary tract imaging should be requested to exclude structural kidney disease and confirm suitable anatomy for biopsy
	Reduced cortical thickness and bipolar kidney length have been associated with an increased risk of haemorrhagic complications[5-9] and poorer diagnostic sample adequacy[10,11]
	There is no evidence that a solitary or horseshoe kidney predisposes to a higher rate of post-biopsy haemorrhage[12,13]; however, patients risk the loss of their only kidney in the event of misadventure
	Percutaneous biopsy is traditionally avoided in cystic kidneys. Sufficient renal parenchymal tissue is difficult to obtain and there are theoretic risks of haematoma or infection from cyst trauma
Urine culture	Urine cultures should be requested prior to biopsy to identify bacteriuria, which may increase the risk of UTI
	An audit of 1812 consecutive biopsies identified only 2 cases of post-procedure UTI[14]
	Abscess formation, pyomyositis, and bacteraemia have been reported after biopsies of patients with active pyelonephritis
Blood pressure	Hypertension is a risk factor for major bleeding, particularly when the systolic blood pressure exceeds 160 mmHg[15]
	A systolic blood pressure of 160 mmHg is a commonly accepted upper limit for kidney biopsy
	Hypertension on the day of biopsy often leads to patients having their procedure postponed. The effect of rapidly lowering blood pressure with antihypertensives immediately before biopsy are unknown
Haemoglobin	The approach to pre-biopsy anaemia is contentious and based on anecdotal evidence. Many local protocols recommend a pre-biopsy haemoglobin greater than 100 g/L
	Anaemic patients are more likely to require a blood transfusion after biopsy, especially when the pre-procedure haemoglobin is less than 80 g/L[18,22]
	In observational studies the need for transfusion was independent of clinical bleeding events[21], implying that transfusion rates were mediated by other factors such as comorbidities or protocolised haemoglobin targets
Coagulation studies	Kidney biopsy is classified by the Society of Interventional Radiology as a high-risk procedure for bleeding[16]
	The international normalised ratio must be less than 1.5 and the platelet count greater than 50 ×109/L prior to kidney biopsy[17,18]. Data supporting these recommendations are poor[17,19,20]
	The utility of the APTT is unclear. The Caring for Australians and New Zealanders with Renal Impairment guidelines recommend checking the APTT pre-biopsy but do not comment on its interpretation[18]

APTT: Activated partial thromboplastin time; UTI: Urinary tract infection.

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