1. What are the major clinical uses for a kidney biopsy?

A kidney biopsy is performed to help establish a diagnosis and aid in the selection of an appropriate therapy when clinical and laboratory tests are unrevealing. The degree of active and chronic changes helps generate valuable information regarding the prognosis and likelihood of a treatment response. A kidney biopsy is routinely used to differentiate causes of transplant allograft dysfunction.

2. In which clinical settings is a kidney biopsy most useful as an aid in the evaluation and management of a patient with undiagnosed kidney disease?

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  Acute Kidney Injury (AKI) : A kidney biopsy is recommended when a patient has unexplained AKI that does not improve with supportive therapy. Prerenal disease, acute tubular necrosis, and obstruction must be ruled out, as these can be diagnosed based on clinical history.

  
  
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  Nephrotic Syndrome: Adults with evidence of nephrotic syndrome with no apparent underlying cause should undergo a kidney biopsy. Children with nephrotic syndrome are presumed to have minimal change disease and are treated empirically with steroids. A kidney biopsy is reserved for children with atypical features, including steroid resistance, hematuria, or kidney impairment.

  
  
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  Systemic Disease: Patients with vasculitis, systemic lupus erythematous, and viral infection-related nephropathy often require a kidney biopsy. Information is important in not only confirming a diagnosis but also in dictating further therapy based on the extent of active or chronic changes. In patients diagnosed with diabetes mellitus with kidney dysfunction, a kidney biopsy is sometimes suggested in the presence of features inconsistent with diabetic nephropathy, such as rapid progression or persistent hematuria. Additionally, a kidney biopsy is often recommended in the setting of various dysproteinemias when information would change the management strategy.

  
  
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  Hematuria: In patients with isolated microscopic hematuria, urologic causes must first be excluded. Patients with persistent non-urologic microscopic hematuria with proteinuria and/or kidney insufficiency often require a kidney biopsy for diagnostic and therapeutic purposes. In contrast, a kidney biopsy is usually not required in isolated microscopic non-urologic hematuria without kidney insufficiency, hypertension, or proteinuria. One may consider a kidney biopsy with microscopic hematuria and unique circumstances, such as in the evaluation of potential living kidney donors, life insurance, or employment purposes.

  
  
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  Transplant Allograft: Kidney biopsy is used in transplant kidney recipients who develop hematuria, proteinuria, or kidney transplant dysfunction to differentiate between the various forms of rejection versus other causes of kidney failure.

  
  
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  Chronic Kidney Disease: A kidney biopsy may be useful in prognostication for patients with unexplained chronic kidney disease and normal-sized kidneys on imaging.

3. What are some clinical scenarios when a kidney biopsy may not be necessary?

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  Acute kidney injury in which a clinical diagnosis of pre-renal disease, acute tubular necrosis, or obstruction is evident

  
  
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  Isolated glomerular hematuria without evidence of kidney dysfunction or proteinuria

  
  
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  Isolated non-nephrotic proteinuria with the absence of kidney insufficiency or glomerular hematuria

  
  
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  Patients with an insidious onset of proteinuria with a known diagnosis of long-standing diabetes mellitus (with slow progression of kidney disease) or massive obesity with presumed secondary focal segmental glomerulosclerosis

  
  
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  Patients with chronic kidney disease with small, hyperechoic kidneys. These patients are at higher risk of biopsy complications and are unlikely to have reversible disease.

4. What are the clinical components of the pre-biopsy evaluation?

A complete history, physical examination, and selected laboratory tests are performed prior to a kidney biopsy. Current medications need to be reviewed with particular attention to antiplatelet agents, aspirin, nonsteroidal anti-inflammatory drugs, and anticoagulants. Ideally, patients should be alert, cooperative, and able to follow simple directions. The skin overlying the planned biopsy site needs to be free from infection.

5. What laboratory data should be obtained before undertaking a kidney biopsy?

Routine laboratory tests that are obtained before biopsy include a complete biochemical profile, complete blood count, platelet count, prothrombin time, partial thromboplastin time, blood type, antibody screen for cross-matching, and a urinalysis. The practice of obtaining bleeding times prior to a percutaneous kidney biopsy is debated among different medical centers due to the lack of randomized, prospective studies, availability, and consistency. In a large prospective study of more than 1000 percutaneous kidney biopsies using real-time ultrasound guidance, patients with a bleeding time greater than 7.5 minutes had higher rates of biopsy-related complications. About 50% of these patients had a serum creatinine greater than 1.5 mg/dL. However, other studies have reported no increased risk. The use of bleeding times prior to a percutaneous kidney biopsy thus remains center dependent.

6. What are the contraindications to percutaneous kidney biopsy?

The absolute contraindications for performing a percutaneous kidney biopsy, as defined by the Health and Public Policy Committee of the American College of Physicians in 1988, include:

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  Uncooperative patient

  
  
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  Solitary native kidney

  
  
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  Uncontrolled severe hypertension

  
  
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  Uncontrolled bleeding diathesis

With the exception of an uncontrolled bleeding diathesis, many consider these to be relative contraindications, which may be overridden in specific clinical circumstances. Percutaneous kidney biopsy of a solitary kidney has been performed successfully in small studies with technological advances of real-time ultrasound guidance and the use of automated needles. Other relative contraindications include:

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  Active pyelonephritis

  
  
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  Perinephric abscess

  
  
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  Skin infection over the biopsy site

  
  
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  Hydronephrosis

  
  
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  Multiple cysts

  
  
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  Kidney tumor

  
  
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  Small hyperechoic kidneys

  
  
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  Uncontrolled hypertension

  
  
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  Hypotension

7. What are non-percutaneous methods of kidney biopsy?

A non-percutaneous kidney biopsy is performed when contraindications to the percutaneous method exist but tissue is required for diagnosis and treatment.

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  Transvenous Kidney Biopsy : The transvenous, usually transjugular, kidney biopsy is performed by an interventional radiologist. The major indication for this technique is in patients with a bleeding diathesis. The reason that the transvenous approach is preferred for patients with bleeding diathesis is not that bleeding complications are less compared to the percutaneous approach, it is that an immediate bleeding complication can be treated quickly with the use of interventional techniques. A transvenous biopsy is also preferred in patients with morbid obesity, requiring multiple organ biopsies, and following unsuccessful attempts via the percutaneous route. Contraindications include bilateral internal jugular vein thrombosis and allergies to contrast material. The cost, the risk of contrast induced nephropathy, the variable operator experience, and the obtaining of an inadequate sample to establish a diagnosis are limitations of this technique.

  
  
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  Open Kidney Biopsy : The open, or surgical, kidney biopsy is a safe and effective technique to obtain kidney tissue. The indications are similar to those outlined for the transvenous kidney biopsy, and it is performed in intensive care patients who are being mechanically ventilated. The risk of bleeding is low and mortality is rare. However, disadvantages of this technique include the risk of general anesthesia, fever, atelectasis, and a longer recovery time compared to the percutaneous approach.

  
  
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  Laparoscopic Kidney Biopsy : Experience thus far suggests that the laparoscopic route is a safe, reliable, and accurate procedure to obtain kidney tissue.