Performing a percutaneous kidney biopsy

Abstract

The percutaneous kidney biopsy is an important skill in nephrology practice. Evidence-based material specifically discussing the procedural steps of a kidney biopsy is lacking. This article outlines the technical process and peri-procedural management of ultrasound-guided percutaneous kidney biopsy and is intended to serve as a useful and practical resource for nephrology trainees and consultants.

Key Words: Biopsy; Percutaneous; Kidney; Nephrology; Ultrasound

Core Tip: The percutaneous kidney biopsy is an important skill for nephrologists. A thorough understanding of anatomical and theoretical principles for each step of the procedure can improve safety and effectiveness.

INTRODUCTION

The kidney biopsy contributes to the evaluation and management of selected patients with kidney disease and is an important clinical skill for nephrologists. In Australia, kidney biopsies are performed with increasing frequency and approximately 6000 procedures are now undertaken annually[1], of which more than 90% are performed by nephrologists[2]. Most nephrologists in Australia consider the kidney biopsy to be an essential skill; however, practices vary internationally and kidney biopsies are increasingly performed by radiologists. The most frequent technique is the percutaneous ultrasound-guided kidney biopsy. Image guidance using computed tomography (CT) is an acceptable alternative to ultrasound that is frequently employed in many centres; however, CT-guided biopsy is typically less accessible, more expensive, and takes longer to perform[3,4].

Clinicians performing kidney biopsies require a thorough understanding of relevant anatomy and technical principles. Evidence supporting specific aspects of kidney biopsy technique is limited. Procedural technique is influenced by operator experience and preferences and local resources. The early stages of learning to perform a kidney biopsy usually rely on simulation models and tuition from supervisors. Because the kidney biopsy remains a core skill in many nephrology training curricula, practical, detailed, evidence-based educational material should be available.

This narrative review discusses the stepwise process of ultrasound-guided, percutaneous, native kidney biopsy. It is intended as a primer or refresher for nephrologists and trainees. Related topics such as clinical indications, histopathology and perioperative medication management are not discussed. CT-guided biopsy, transplant kidney biopsy, and the special cases of pregnant or paediatric patients are also not discussed.

METHODOLOGY

A structured search of the PubMed database was undertaken from inception to November 2025 using a range of search terms. Results were screened for relevance. A broad selection of articles was obtained and additional resources were retrieved by manual searches of references. Higher levels of evidence were prioritised. Results of the literature search were synthesised to generate this narrative, rather than systematic, review.

ANATOMY

The native kidneys are paired bean-shaped organs located in the retroperitoneal space (Figure 1). The kidneys are parallel to the psoas muscle on an oblique axis, in which the upper poles are slightly medial relative to the lower poles. Anatomically normal kidneys are approximately 12 cm in bipolar length, 6 cm wide, and 3 cm thick in the sagittal plane. They are 1-2 cm longer in males than in females and the left kidney volume is slightly larger than the right. The upper poles are at the level of the T12 vertebra and protected by the lower ribs, and the lower poles are at the level of L3. The right kidney is slightly caudal relative to the left due to displacement by the liver.

Figure 1 Anatomical relations to the kidney and depiction of a typical percutaneous biopsy path (dashed lines) in axial and sagittal planes.

The native kidneys are surrounded by a fibrous renal capsule, fascia and fatty tissue. The dorsal surface of the kidney is convex and generally 6-7 cm deep to the skin. Kidney depth may be increased in individuals with obesity. This area comprises most of the renal parenchyma. The anterior-medial surface is concave, housing the renal hilum. The renal hilum contains structures including the renal artery, renal veins and ureter. The kidneys are highly vascularised and receive approximately 20% of cardiac output. Blood vessel density is lower in the posterior-lateral aspect of the kidney parenchyma.

The outer layer of renal parenchyma is the cortex, with a mean thickness of 5-10 mm, and the deeper layer of renal parenchyma is the medulla, with a mean thickness of 15-20 mm. Sonographically, the renal cortex appears more echogenic than the medulla (Figure 2).

Figure 2 Ultrasound of the right kidney demonstrating preserved corticomedullary differentiation in which cortex is hyperechoic (solid line) relative to medulla (dashed line).

The kidneys move in a cranio-caudal direction during the respiratory cycle. During quiet breathing the lower poles of the kidneys descend approximately 1 cm whereas with forced inspiration the kidneys descend by 2-3 cm.

CONTRAINDICATIONS

Awareness of contraindications to kidney biopsy enables individualised assessment of risks and benefits and informs peri-procedural care. A kidney biopsy is avoided in patients with a severe bleeding diathesis, in patients who decline to consent, and in patients who are unable to cooperate. A biopsy may still be necessary in certain individuals with relative contraindications, accepting increased procedural risk. Relative contraindications may include structurally abnormal kidneys or a solitary kidney, concurrent urinary or overlying soft tissue infection, uncontrolled hypertension, and anaemia. Important considerations for procedural planning are outlined in Table 1[5-22].

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.

EQUIPMENT

Tray and trolley setup

Basic surgical materials are laid out on a sterile tray and back table cover upon a procedure trolley (Figure 3). Standard equipment includes needles, syringes, local anaesthetic, gauze, skin cleansing solution, a scalpel blade, ultrasound gel with a sterile probe cover, a sterile fenestrated drape, and dressings.

Figure 3 Standard equipment and trolley setup for percutaneous biopsy.

Lidocaine is most commonly used for local anaesthesia. Clinicians should be familiar with the safe maximal doses of local anaesthetics. Admixture of local anaesthetic with adrenaline reduces bleeding and prolongs the duration of action, though not specifically studied in the context of solid organ biopsy.

Personal protective equipment should be worn. Sterile gloves are essential, but the need for a sterile gown is not mandated by all institutions. Although widely recommended, data on the utility of personal protective equipment are scarce. Local hospital policies should be observed. The risk of infective complications through contamination is very low[13].

Kidney biopsy may be performed either at the patient’s bedside or in a dedicated procedure area, provided that aseptic technique is maintained.

Biopsy device

The devices available for percutaneous biopsies can be categorised as automatic or manual, disposable or reusable, and by needle size (Figure 4).

Figure 4 Examples of disposable automatic (left), sterilisable automatic (centre) and manual (right) needle biopsy devices.

Manual biopsy devices feature a needle which is cored into tissue using screwing, aspiration or cutting motions. Automatic devices are spring-loaded guns containing a cutting stylet at the end of the needle that is deployed after activating the device, such as by pressing a button, often referred to as the needle’s ‘throw’. The device’s triggering button is located on the shaft of the handle or near the top of the handle. Manual devices are uncommon in contemporary practice. Spring-loaded guns are associated with a higher diagnostic yield and a lower incidence of haemorrhagic complications[23-26], and are generally simpler and faster to operate than manual devices.

Percutaneous biopsy is usually accomplished through a 14-gauge (14G), 16-gauge (16G) or 18-gauge (18G) needle. Needle diameter may influence the risk of post-procedure bleeding complications. In a meta-analysis of 34 studies including 9474 kidney biopsies, blood transfusions were more frequently required after 14G needle biopsies compared with smaller needles (2.1% vs 0.05%, P < 0.01)[22]. There were no significant differences in the rates of bleeding between 16G and 18G needles in retrospective studies[27,28].

Larger needles yield more diagnostic tissue and glomeruli than smaller needles. A North American registry of more than 120000 biopsies showed significant differences in the mean number of sampled glomeruli for each needle gauge (25 glomeruli for 14G, 12 for 16G and 10 for 18G; P < 0.01)[29]. However, adequate tissue is still obtained in most instances regardless of needle choice, suggesting that needle gauge per se is rarely the determining factor in the ability to confirm a diagnosis[30,31]. Specimen adequacy may be more important in complex cases such as pathologic interpretation of kidney transplant biopsies.

The Caring for Australians and New Zealanders with Renal Impairment (CARI) guidelines recommend that a 16G automatic spring-loaded gun be preferentially used for percutaneous kidney biopsy[26]. The Society of Interventional Radiology guidelines do not make a specific recommendation but state that operators should appreciate the strengths and weaknesses of each biopsy method[32].

Ultrasound

A portable ultrasound machine with a curvilinear probe is required. Real-time ultrasound guidance enhances success and safety compared with alternative methods, such as blind percutaneous biopsy or biopsy guided by static ultrasound marking[33-35], and shortens procedural time. Some practitioners perform percutaneous biopsy using a fixed needle guide. Needle guides are brackets mounted on the ultrasound probe, through which a biopsy needle is channelled. Needle guides purportedly aid visualization by maintaining alignment between the ultrasound beam and needle in a long-axis view. There are insufficient data to recommend needle guides as opposed to a standard freehand technique.

PREPARATION

Patient preparation for kidney biopsy should be individualised (Table 1)[5-22]. Data supporting specific pre-procedure instructions are generally lacking. Guidelines, such as those published by CARI, and local policies should be considered.

Informed consent must be obtained and allergies should be clarified. It is prudent to gain peripheral intravenous access before the procedure. Antibiotic prophylaxis is not usual practice. Non-invasive monitoring, including pulse oximetry and blood pressure measurements, should be available. Society guidelines recommend monitoring every 5 minutes when intravenous sedation is administered[36,37], but there is no consensus on how to record vital signs during procedures performed using only local anaesthetic. Guidelines for perioperative antithrombotic medication management and the use of intravenous desmopressin to reduce haemorrhagic complications are available. Although uraemia is a risk factor for post-biopsy bleeding, a small retrospective study did not show any benefit from pre-emptive haemodialysis[38].

PROCEDURE TECHNIQUE

The following section describes a typical approach to percutaneous ultrasound-guided kidney biopsy. There is no single best way to perform kidney biopsy, and it is recognised that alternative procedural techniques are also frequently practiced depending on operator preference and individual patient circumstances. Common technical variations are summarised in Table 2[39-44].

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

Patient positioning

The patient is positioned prone with a pillow or padding placed beneath their lower abdomen and pelvis. This improves accessibility by straightening the lower back and splinting the kidneys nearer to the skin surface[45]. Positioning the patient’s hips parallel to the ceiling helps to minimise parallax error with needle advancement.

A preliminary bedside ultrasound is performed to clarify the position of the kidneys and their suitability for biopsy. The movement and depth of the lower pole of the kidney throughout the respiratory cycle is observed.

A right-handed proceduralist typically stands on the prone patient’s left side and targets the patient’s left kidney (Figure 5). The ultrasound machine and screen are situated in a comfortable line of sight for the operator.

Figure 5 Patient positioning for kidney biopsy.

Preparing the surgical site

The area is cleaned and draped to create a sterile field. The necessary equipment is assembled. The ultrasound probe within a sterile cover is placed on the patient and the needle approach is planned. A complete discussion of the principles of procedural ultrasound guidance is beyond the scope of this article. Some practitioners may choose to mark the skin with a surgical pen.

Local anaesthetic is infiltrated subcutaneously with a small needle. Next, a long spinal needle is used to infiltrate anaesthetic to the deeper tissues along the biopsy track under ultrasound guidance (Figure 6). The spinal needle is visualised using a long-axis (‘in-plane’) ultrasound view. Approximately 10 mL of 1%-2% lignocaine is typically sufficient. Since the biopsy specimens must be obtained as the patient holds their breath, it is important to anticipate the kidney’s position during the respiratory cycle when anaesthetising the tract.

Figure 6 Real-time long-axis needle visualisation along a tract from the skin to the level of the kidney.

Deploying the biopsy gun

The lower pole of the left kidney is most often targeted for biopsy. The operator should choose a short path that allows reasonable access to the renal cortex of the lower pole. Typically, the needle is advanced at an angle of approximately 45 degrees in a cranial direction, involving a tract length of around 10 cm (Figure 7); however, exact dimensions will vary depending on patient body habitus.

Figure 7 Biopsy needle tip approaching the left kidney lower pole at approximately 45 degrees (left), and examples of alternative needle trajectories targeting renal cortex (right, dashed lines) relative to the standard trajectory (right, solid line).

A small stab incision is made at the skin entry site with a scalpel blade to facilitate passage of the larger biopsy needle. Ensure the throw of the biopsy device is dialled to the correct setting. Under ultrasound guidance, the biopsy needle is advanced carefully through the skin nick and along the anaesthetised tract to the level of the renal capsule. Changes in resistance are felt as the needle passes through connective tissue and muscle layers. It is imperative to maintain alignment between the ultrasound plane and the needle during advancement (Figure 8). Although echogenicity of the biopsy needle is low, the location of the needle tip must be known with confidence throughout the procedure.

Figure 8 Advancing the biopsy needle under real-time ultrasound guidance.

Tenting of adjacent soft tissues with slight inward displacement of the renal parenchymal border on ultrasound signifies abutting of the needle tip at the renal capsule. This is the location from which to deploy the biopsy needle. The patient is asked to hold their breath in the desired phase of respiration. During the breath hold, the biopsy device is then triggered. When activated, the length of the spring-loaded biopsy gun throw will penetrate 1-2 cm into renal cortex and snare a small tissue core.

Remove the biopsy needle quickly and instruct the patient to resume normal breathing. If venous ooze is noted at the skin entry site upon removal of the needle, apply manual pressure for several minutes to achieve haemostasis. The process is repeated as needed to obtain a number of samples.

INTERPRETATION AND SPECIMEN COLLECTION

Specimen collection, handling and interpretation are complex and beyond the scope of this review. Practices are frequently contingent on patient and centre factors. At least two sufficient tissue cores should be obtained for pathologic analysis, typically including light microscopy and immunofluorescence. The number of needle passes is associated with the risk of post-procedure bleeding. The rates of major complications substantially increase when 4 or more passes are attempted[46,47].

AFTERCARE AND COMPLICATIONS

Complications

The most important mechanical complication of kidney biopsy is haemorrhage. Post-biopsy haemorrhage ranges in severity from mild bruising or haematuria to exsanguination necessitating surgical intervention. Asymptomatic perinephric haematoma is commonly seen on ultrasound and its presence is not a reliable predictor of clinically significant bleeding events[48]. Routine post-biopsy ultrasound is therefore not recommended. Haematoma can be identified on CT in 75% of patients following biopsy[13]. Macroscopic haematuria develops in 4% of patients and is usually benign; however, concurrent flank or abdominal pain or the passage of urinary clots is predictive of major haemorrhage and warrants immediate attention. The rates of blood transfusion, endovascular intervention and nephrectomy after kidney biopsy are approximately 1%, 0.6% and 0.01%, respectively[49].

Post-procedure monitoring

After a kidney biopsy all patients should be admitted to a recovery area for a period of close observation. The purpose of observation is to mitigate risk factors that lead to complications and to aid in the early detection of any such complications. The kidney biopsy is usually a day procedure but patients deemed at higher risk may be admitted to hospital overnight for monitoring.

The CARI guidelines recommend a post-biopsy observation period of 6-8 hours for low-risk biopsies and up to 24 hours for high-risk biopsies[18]. Two small randomised trials reported no differences in outcomes among low-risk patients who were allocated to observation for 6 hours vs 24 hours[50,51]. Patient selection should influence the period of observation. Over a third of major complications occurred beyond 8 hours in several retrospective cohorts[18], while more than 90% of complications were detected within 4 hours in a recent large Australian audit[52].

Vital signs and urine output are regularly examined during the observation period to check for signs of bleeding. The intervals for measuring these parameters are directed by local protocols; the authors’ practice is to prescribe post-procedure monitoring for 6 hours, checking vital signs every 15 minutes for the first 2 hours, every 30 minutes for the next 2 hours, then hourly for the final 2 hours. Systolic blood pressure should be maintained below 160 mmHg using antihypertensive medication as needed. Although there are no data directly validating this approach, the value of avoiding hypertension is well recognised in the setting of haemorrhagic shock.

The urine is inspected for post-biopsy macroscopic haematuria. However, the relevance of painless macroscopic haematuria is unclear. There was no association between haematuria and the need for blood transfusions[19] or the incidence of renal arteriovenous fistula formation[18] in observational studies, although clot-related urinary tract obstruction has been reported. Haematuria diminishes over time. A reasonable approach may be for individuals with macroscopic haematuria to be advised to remain in hospital until bleeding resolves. Checking a urinalysis for microscopic haematuria in asymptomatic individuals is probably unwarranted.

The patient is instructed to maintain bedrest for around 6 hours. Confinement to bedrest theoretically minimises haemodynamic changes and clot disturbance. There is good evidence that longer periods of bedrest than 6 hours do not further reduce the likelihood of post-biopsy bleeding[51,53]. Protocols incorporating only 2 hours of bedrest have been described but are not a standard practice.

Discharge advice

Patients should avoid strenuous exertion and heavy lifting for 1-2 weeks. Exertion is inconsistently defined, but frequently cited examples include sexual activity, contact sports or carriage of greater than 5-10 kg. Some clinicians advise patients not to drive a motor vehicle for up to 7 days post-biopsy. There is minimal evidence to substantiate any particular post-discharge instructions.

CONCLUSION

The percutaneous kidney biopsy plays an important role in nephrology can be performed safely and effectively.