Kidney biopsy

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?

• 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.

• 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.

• 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.

• 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.

• 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.

• 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?

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

• Isolated glomerular hematuria without evidence of kidney dysfunction or proteinuria

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

• 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

• 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.