Update on the Native Kidney Biopsy: Core Curriculum 2019

The kidney biopsy is an invaluable tool that has become the gold standard for the diagnosis of pathologic kidney diseases since the early 1950s. Throughout the years, immunohistologic and ultrastructural microscopy techniques have improved and provide more information on the cause and classification of kidney diseases than that available from simple light microscopy alone. Kidney biopsy has become a preferred method to obtain critical information that can be used in conjunction with serologic, urinary, and genetic testing to diagnose a variety of kidney diseases, both acute and chronic. The kidney biopsy procedure carries relatively low risk and yields substantial information. Potential complications include bleeding requiring transfusion, gross hematuria, arteriovenous fistula formation, and perinephric hematoma, among others. Percutaneous kidney biopsies are typically performed using real-time ultrasound or computed tomographic imaging. This Core Curriculum briefly outlines the history of the kidney biopsy, then discusses indications, complications, and specific procedural aspects. The kidney biopsy is an invaluable tool that has become the gold standard for the diagnosis of pathologic kidney diseases since the early 1950s. Throughout the years, immunohistologic and ultrastructural microscopy techniques have improved and provide more information on the cause and classification of kidney diseases than that available from simple light microscopy alone. Kidney biopsy has become a preferred method to obtain critical information that can be used in conjunction with serologic, urinary, and genetic testing to diagnose a variety of kidney diseases, both acute and chronic. The kidney biopsy procedure carries relatively low risk and yields substantial information. Potential complications include bleeding requiring transfusion, gross hematuria, arteriovenous fistula formation, and perinephric hematoma, among others. Percutaneous kidney biopsies are typically performed using real-time ultrasound or computed tomographic imaging. This Core Curriculum briefly outlines the history of the kidney biopsy, then discusses indications, complications, and specific procedural aspects. FEATURE EDITOR:Asghar RastegarADVISORY BOARD:Ursula C. BrewsterMichael ChoiAnn O’HareManoocher SoleimaniThe Core Curriculum aims to give trainees in nephrology a strong knowledge base in core topics in the specialty by providing an overview of the topic and citing key references, including the foundational literature that led to current clinical approaches. FEATURE EDITOR: Asghar Rastegar ADVISORY BOARD: Ursula C. Brewster Michael Choi Ann O’Hare Manoocher Soleimani The Core Curriculum aims to give trainees in nephrology a strong knowledge base in core topics in the specialty by providing an overview of the topic and citing key references, including the foundational literature that led to current clinical approaches. The microscopic assessment of histopathologic lesions in kidney biopsy tissue was predated by macroscopic examination of kidney tissue at the time of autopsy. In the 19th century, with the invention of the microtome, autopsy reports started including renal histology on unstained specimens. With the introduction in the late 19th and early 20th centuries of various specific stains (derivatives of which are still used today), the evaluation of autopsy kidney specimens became more thorough and detailed. The first surgical biopsy of the kidney was performed by Dr George Edelbohls as part of a renal-capsule stripping technique in patients with Bright disease. These early histologic descriptions included “pronounced changes in the interstitial tissue and glomeruli, the latter having in many instances undergone fibrosis and hyaline degeneration.” Through the early to mid 20th century, surgical kidney biopsy grew in popularity. The percutaneous kidney biopsy was first realized, rather coincidentally, when kidney tissue was accidently obtained during liver biopsies. The first true aspiration needle biopsy of the kidney was performed by Nils Alwall in 1944 using x-ray and retrograde pyelography. The kidney biopsy was then mostly used for the diagnosis of renal neoplasms. The percutaneous kidney biopsy by aspiration technique was perfected by other physicians and brought to the forefront of diagnostic tools in nephrology by Poul Iverson and Claus Brun in a landmark publication in the American Journal of Medicine in 1951. The biopsy was seen as a safe way to have a meaningful impact on diagnosis, with an early analysis by Robert Kark showing that the diagnosis was altered in 25 of 48 patients undergoing biopsy. With the advent of newer diagnostic stains and microscopic techniques, including immunofluorescence and scanning electron microscopy, the field of renal pathology began to flourish as a subspecialty of surgical pathology. Although historically nephrologists performed most kidney biopsies, currently a significant fraction are performed by physicians other than nephrologists, typically radiologists. Data collected within the last 10 years have shown that although nephrology training programs offer opportunities to acquire the required kidney biopsy skills, many graduating nephrology fellows do not feel competent to perform kidney biopsies on their own in practice. The trend toward having radiologists perform kidney biopsies likely reflects time and reimbursement constraints. Nonetheless, competence in performance of kidney biopsies, both native and transplant, is a required element of nephrology fellowship training. ►Berns JS. A survey-based evaluation of self-perceived competency after nephrology fellowship training. Clin J Am Soc Nephrol. 2010;5(3):490-496. ★ ESSENTIAL READING►Berns JS, O’Neill WC. Performance of procedures by nephrologists and nephrology fellows at U.S. nephrology training programs. Clin J Am Soc Nephrol. 2008;3(4):941-947.►Cameron JS, Hicks J. The introduction of renal biopsy into nephrology from 1901 to 1961: a paradigm of the forming of nephrology by technology. Am J Nephrol. 1997;17(3-4):347-358.►lverson P, Brun C. Aspiration biopsy of the kidney. Am J Med. 1951;11(3):324-330.►D’Agati VD, Mengel M. The rise of renal pathology in nephrology: structure illuminates function. Am J Kidney Dis. 2013;61(6):1016-1025. Case 1: A 53-year-old man with a history of type 2 diabetes mellitus for 10 years without signs of retinopathy or neuropathy and also hypertension for 5 years controlled with atenolol, 50 mg, daily and lisinopril, 10 mg, daily is presenting for evaluation of moderate lower-extremity edema. Blood pressure is 134/76 mm Hg with a heart rate of 74 beats/min, with examination findings notable for bilateral pretibial edema (1+). Laboratory test results are relatively unremarkable, with a serum creatinine (Scr) level of 1.09 mg/dL (stable for the last 3 years), with the exception of serum albumin level of 2.5 g/dL (normal 3 years prior) and urine albumin-creatinine ratio (UACR) of 4,775 μg/mg, which is higher than that from 1 year ago (when it was 185 μg/mg). Urine sediment demonstrates 5 to 10 red blood cells per high-power field, with 5% dysmorphic red blood cells.Question 1: Based on this presentation, what is the best next step in the management of this patient?a)Reassess UACR in 1 monthb)Increase lisinopril dosagec)Initiate treatment with corticosteroidsd)Proceed with kidney biopsyFor the answer to the question, see the following text. Case 1: A 53-year-old man with a history of type 2 diabetes mellitus for 10 years without signs of retinopathy or neuropathy and also hypertension for 5 years controlled with atenolol, 50 mg, daily and lisinopril, 10 mg, daily is presenting for evaluation of moderate lower-extremity edema. Blood pressure is 134/76 mm Hg with a heart rate of 74 beats/min, with examination findings notable for bilateral pretibial edema (1+). Laboratory test results are relatively unremarkable, with a serum creatinine (Scr) level of 1.09 mg/dL (stable for the last 3 years), with the exception of serum albumin level of 2.5 g/dL (normal 3 years prior) and urine albumin-creatinine ratio (UACR) of 4,775 μg/mg, which is higher than that from 1 year ago (when it was 185 μg/mg). Urine sediment demonstrates 5 to 10 red blood cells per high-power field, with 5% dysmorphic red blood cells. Question 1: Based on this presentation, what is the best next step in the management of this patient?a)Reassess UACR in 1 monthb)Increase lisinopril dosagec)Initiate treatment with corticosteroidsd)Proceed with kidney biopsy For the answer to the question, see the following text. The kidney biopsy is an invasive procedure with potential risks. A kidney biopsy should be recommended when kidney tissue is required to make a definitive diagnosis that might affect treatment or provide information about disease progression or prognosis. A biopsy should be avoided when the potential risk to the patient exceeds any likely benefit from procuring kidney tissue. A biopsy should be contemplated for certain patients with acute kidney injury (AKI), proteinuria, or hematuria (Table 1). However, not every such patient requires a kidney biopsy. Patients with AKI due to decreased kidney perfusion or obstruction need not undergo a kidney biopsy unless the initial cause for injury has been corrected and there is still confusion regarding the cause of AKI. Patients with intrinsic AKI may have tubulointerstitial disease, vascular disease, or glomerular disease. Patients with a diagnosis of hemodynamically mediated AKI (acute tubular injury or necrosis) do not usually need a biopsy unless the cause of the AKI is unclear or there are other features that suggest a need for a biopsy, such as new proteinuria or hematuria. In patients with possible acute interstitial nephritis, a biopsy may be necessary if there is ambiguity in the diagnosis or if necessary before initiating immunosuppression treatment with glucocorticoids.Table 1Indications for Kidney BiopsyIndicationsCommentsHematuriaPresence of acanthocytes or red blood cell casts with an elevated Scr level or proteinuriaProteinuriaProteinuria > 1 g/d as measured on multiple visits with no clear comorbidity; proteinuria > 3 g/d in the absence of diabetes or a rapid increase in proteinuria even with diabetes; proteinuria < 3 g/d with an elevated Scr level with no clear comorbid conditions such as diabetes or hypertensionAKIIn the setting of ATI, persistent injury despite reversal of cause or if Scr did not return to baseline with 7-14 d of injury onset; in the setting of presumptive AIN, if there has been no resolution of injury despite removal of culprit medicationCKDRapid elevation in Scr level or new-onset hematuria or proteinuriaAbbreviations: AIN, acute interstitial nephritis; AKI, acute kidney injury; ATI, acute tubular injury; CKD, chronic kidney disease; Scr, serum creatinine. Open table in a new tab Abbreviations: AIN, acute interstitial nephritis; AKI, acute kidney injury; ATI, acute tubular injury; CKD, chronic kidney disease; Scr, serum creatinine. The presence of new-onset proteinuria or proteinuria accompanied by hematuria is often an indication for kidney biopsy to assess for and diagnose glomerular disease and guide therapy. Patients with low-grade proteinuria (protein excretion < 0.5-1 g/d) may not require a biopsy unless there is an accompanying elevated Scr level, hematuria, or evidence of a systemic disease (such as systemic lupus erythematosus). In diabetic patients with new onset of nephrotic-range proteinuria without antecedent proteinuria, a biopsy should generally be performed because such patients often have a lesion other than any underlying diabetic kidney disease. Patients with isolated hematuria with normal estimated glomerular filtration rates without proteinuria, in whom other nonkidney diseases of the genitourinary tract have been excluded, may not require a biopsy. These patients will most often have nonproteinuric immunoglobulin A (IgA) nephropathy or thin basement membrane disease. The course of such patients is usually benign with excellent prognosis unless proteinuria or a worsening estimated glomerular filtration rate develops, at which time a biopsy could be considered. Hematuria in the presence of proteinuria and elevated Scr level generally requires a biopsy to make a diagnosis. Patients with known or suspected systemic lupus erythematosus or other glomerular diseases who present with hematuria or proteinuria with or without an elevated Scr level should generally undergo biopsy to classify the specific glomerular lesion and guide subsequent therapy. In addition, patients with previously biopsied lupus nephritis may also benefit from a later repeat biopsy to assess kidney disease activity and guide therapy. In case 1, this patient with diabetes has not had evidence of significant proteinuria in the recent past. The sudden onset of nephrotic-range proteinuria in a patient with diabetes should be evaluated with a kidney biopsy. Empirically treating the patient with corticosteroids would not be advised because without a diagnosis, the therapy is unclear and corticosteroids may elevate blood glucose level significantly. Titration of his lisinopril dosage would not be enough if this were nondiabetic glomerular disease. Thus, the best answer is (d). ►Hogan JJ, Mocanu M, Berns JS. The native kidney biopsy: update and evidence for best practice. Clin J Am Soc Nephrol. 2016;11(2):354-362. ★ ESSENTIAL READING►Mazzucco G, Bertani T, Fortunato M, et al. Different patterns of renal damage in type 2 diabetes mellitus: a multicentric study on 393 biopsies. Am J Kidney Dis. 2002;39(4):713-720.►Parikh SV, Alvarado A, Malvar A, Rovin BH. The kidney biopsy in lupus nephritis: past, present, and future. Semin Nephrol. 2015;35(5):465-477.►Pham TT, Sim JJ, Kujubu DA, Liu IL, Kumar VA. Prevalence of nondiabetic renal disease in diabetic patients. Am J Nephrol. 2007;27(3):322-328.►Sharma SG, Bomback AS, Radhakrishnan J, et al. The modern spectrum of renal biopsy findings in patients with diabetes. Clin J Am Soc Nephrol. 2013;8(10):1718-1724. Case 2: A 43-year-old woman with a history of chronic hypertension and a congenitally solitary kidney is presenting for evaluation of new-onset proteinuria. Her blood pressure is treated with hydrochlorothiazide and lisinopril. Examination demonstrates blood pressure of 138/72 mm Hg and she has lower-leg edema (2+). Scr level is stable at 1.4 mg/dL and UACR is 6,835 mg/g, higher than that from 6 months ago (when it was 108 mg/g).Question 2: Based on this presentation, what is the best next step in the management of this patient?a)Refer to surgery for an open surgical kidney biopsyb)Proceed with a percutaneous kidney biopsyc)Empirically treat with corticosteroidsd)Increase lisinopril dose and monitorFor the answer to the question, see the following text. Case 2: A 43-year-old woman with a history of chronic hypertension and a congenitally solitary kidney is presenting for evaluation of new-onset proteinuria. Her blood pressure is treated with hydrochlorothiazide and lisinopril. Examination demonstrates blood pressure of 138/72 mm Hg and she has lower-leg edema (2+). Scr level is stable at 1.4 mg/dL and UACR is 6,835 mg/g, higher than that from 6 months ago (when it was 108 mg/g). Question 2: Based on this presentation, what is the best next step in the management of this patient?a)Refer to surgery for an open surgical kidney biopsyb)Proceed with a percutaneous kidney biopsyc)Empirically treat with corticosteroidsd)Increase lisinopril dose and monitor For the answer to the question, see the following text. The kidney biopsy is a procedure that comes with risk, most notably bleeding. Contraindications to kidney biopsy are associated with patient characteristics that increase the risk for significant postprocedure bleeding (Table 2). Patients undergoing an elective biopsy with uncontrolled hypertension who cannot be managed with intravenous or oral medications should have the biopsy delayed. Patients undergoing an emergent biopsy in whom blood pressure cannot be appropriately controlled may benefit from a surgical biopsy or interventional transjugular biopsy, in which extracapsular bleeding can be intervened upon.Table 2Contraindications to Kidney BiopsyContraindicationCommentBleeding riskIncreased bleeding risk with platelet count < 120 × 103/μL, elevated INR, and use of anticoagulation including aspirin, warfarin, heparin, and direct factor Xa inhibitors Anticoagulation concernsHigher risks would exist in patients in whom stopping anticoagulation therapy would pose significant medical risk (mechanical valve, active VTE disease, high CHADS2 score, LVAD, active APLS)HypertensionIf systolic BP > 140 mm Hg, BP should be lowered before proceedingSmall hyperechoic kidneysIndicative of chronic disease and should be avoided if eGFR is < 30 mL/min/1.73 m2Anatomical kidney problemsVascularity of kidney anomalies or multiple cysts increase bleeding risk Horseshoe kidneyPreferred route is transjugular biopsy Multiple bilateral cystsIf cysts are numerous, it may be difficult to visualize areas that are cyst freeHydronephrosisBiopsy should be delayed until the obstruction is relieved and only pursued if injury persists despite adequate timeSolitary kidneyIf the kidney is visible and biopsy is safe, there is no increased risk with a solitary kidney performed by an experienced providerInfectionSkin infection over the site of needle insertion can lead to sepsis; ongoing pyelonephritis could worsen infection and lead to sepsisAltered mental statusIf the patient cannot cooperate with the biopsy, the risk for injury may be too significantAbbreviations and definitions: APLS, antiphospholipid syndrome; BP, blood pressure; CHADS2, congestive heart failure, hypertension, age (≥65 years = 1 point, ≥75 years = 2 points), diabetes, and stroke/transient ischemic attack (2 points); eGFR, estimated glomerular filtration rate; INR, international normalized ratio; LVAD, left ventricular assist device; VTE, venothromboembolic. Open table in a new tab Abbreviations and definitions: APLS, antiphospholipid syndrome; BP, blood pressure; CHADS2, congestive heart failure, hypertension, age (≥65 years = 1 point, ≥75 years = 2 points), diabetes, and stroke/transient ischemic attack (2 points); eGFR, estimated glomerular filtration rate; INR, international normalized ratio; LVAD, left ventricular assist device; VTE, venothromboembolic. The use of anticoagulation agents also increases the risks of a kidney biopsy. Patients on long-term anticoagulation therapy may undergo a biopsy if it is safe to withhold the anticoagulation treatment for a sufficient time for reversal of the anticoagulant effect and some time afterward. Patients who are on warfarin or direct-acting factor Xa inhibitor therapy should withhold the anticoagulant for at least 72 hours hours before the biopsy, depending on pharmacokinetics and the patient’s underlying thromboembolic risk. If necessary, a short-acting injectable form of low-molecular-weight heparin, or for inpatients, standard heparin intravenously, can be used up until 8 to 12 hours before biopsy. If patients need an urgent biopsy and are on warfarin therapy with an elevated international normalized ratio (INR), either vitamin K or fresh frozen plasma can be administered to acutely reverse the INR. Resuming anticoagulation therapy should occur no sooner than 12 hours after the biopsy and preferably 48 to 72 hours after the biopsy, weighing risks for bleeding and thromboembolism. In patients with underlying bleeding diathesis, whether acquired or genetic, biopsy should be avoided unless the bleeding disorder can be safely reversed and managed immediately postbiopsy. Antiplatelet agents, including aspirin, clopidogrel, and prasugrel, also confer increased risk for bleeding. Standard practice is to withhold these agents for 7 days before the procedure. However, no study has demonstrated a significantly decreased risk for bleeding complication when this is followed. There may be an increased risk for minor, but not major, bleeding, if these drugs are not withheld before the biopsy. The presence of small hyperechoic kidneys generally suggests irreversible advanced chronic kidney disease. Pursuing a biopsy in such patients will most likely not yield clinically meaningful data and thus is usually avoided. A horseshoe kidney or kidneys with multiple large renal cysts or tumors should be approached with caution because the vascular anatomy of these kidneys may be misleading. Doppler duplex ultrasound may be useful in assessing this, and alternative biopsy approaches should be considered. Patients with hydronephrosis should not undergo biopsy until the obstructive process can be reversed. A solitary kidney (or single functioning kidney) can be biopsied safely with a percutaneous approach by an experienced provider because the risk for complications leading to serious injury requiring nephrectomy is low. However, if nephrectomy is required, the patient will be left functionally anephric. Two absolute contraindications include patients who have an active kidney infection or skin infection at the site of needle insertion because the risk for sepsis is increased in these circumstances. In addition, if the patient cannot cooperate with the biopsy due to cognitive impairment, psychiatric disease, or other alterations in mentation, a percutaneous biopsy should not be performed. In case 2, the patient has new-onset nephrotic syndrome and should proceed with a kidney biopsy. The patient has a solitary kidney, but this should not be a contraindication to biopsy assuming that risks are managed with adequate blood pressure control and, if possible, temporarily withholding anticoagulation therapy. Thus, the best answer is (b); however, the biopsy should be performed by an experienced proceduralist. Case 3: A 27-year-old woman who is at 16 weeks’ gestation is presenting with mildly elevated blood pressure at 138/86 mm Hg, a facial rash, and lower-extremity edema that have been present for the last 9 days. Scr level is 1.4 mg/dL (baseline at beginning of pregnancy of 0.8 mg/dL) and UPCR is 3,651 μg/mg, which is new in onset since the beginning of pregnancy. At the time of consult, antinuclear antibody test results are pending, C3 level is 82 mg/dL, and C4 level is 16 mg/dL.Question 3: Based on this presentation, what is the best next step in management of this patient?a)Start patient on empirical corticosteroid therapy for new-onset lupus nephritisb)Proceed with a computed tomography (CT)-guided percutaneous biopsyc)Proceed with an ultrasound-guided percutaneous kidney biopsyd)Start the patient on lisinopril therapy to help control blood pressure and proteinuriaFor the answer to the question, see the following text. Case 3: A 27-year-old woman who is at 16 weeks’ gestation is presenting with mildly elevated blood pressure at 138/86 mm Hg, a facial rash, and lower-extremity edema that have been present for the last 9 days. Scr level is 1.4 mg/dL (baseline at beginning of pregnancy of 0.8 mg/dL) and UPCR is 3,651 μg/mg, which is new in onset since the beginning of pregnancy. At the time of consult, antinuclear antibody test results are pending, C3 level is 82 mg/dL, and C4 level is 16 mg/dL. Question 3: Based on this presentation, what is the best next step in management of this patient?a)Start patient on empirical corticosteroid therapy for new-onset lupus nephritisb)Proceed with a computed tomography (CT)-guided percutaneous biopsyc)Proceed with an ultrasound-guided percutaneous kidney biopsyd)Start the patient on lisinopril therapy to help control blood pressure and proteinuria For the answer to the question, see the following text. Kidney disease in pregnancy can present with either proteinuria or hematuria or an acute increase in Scr level. The time relationship of AKI patterns in pregnancy allows for probable diagnosis based on history, timing of symptom onset, and hematologic and serologic evaluations. Biopsies in pregnant patients are generally safe, with studies showing a low complication risk before 20 weeks’ gestation and case reports showing on average a 2-fold increase in bleeding after 20 to 25 weeks’ gestation. Ideally, the pregnant patient should undergo a percutaneous ultrasound-guided kidney biopsy because CT-guided and transjugular biopsies involve radiation exposure. The technique is similar to that for the nonpregnant patient with the exception of positioning favoring the lateral decubitus or sitting upright position as opposed to the prone position after the 20th week of pregnancy. In case 3, the patient has AKI, hypertension, proteinuria, and a facial rash, suggestive of systemic lupus erythematosus. She should undergo a percutaneous biopsy. Ultrasonography should be used because CT exposes the developing baby to unnecessary radiation. Empirical glucocorticoid therapy should be avoided until the biopsy is complete. Lisinopril should never be used in a pregnant patient. Thus, the best answer is (c). Patients with cirrhosis are at risk for developing AKI or disease. The patient with liver failure may present with significant bleeding risk due to a low platelet count or coagulopathy and elevated INR. Cirrhotic patients appear to have increased risk for postbiopsy bleeding. However, if a percutaneous biopsy is necessary due to lack of interventional expertise, a single pass yielding 1 core can be obtained and used for light microscopy, immunohistochemistry, and electron microscopy, thereby minimizing the risk for bleeding in this cohort of patients in which risk for bleeding has not been fully realized. Mechanical ventilation leads to positional challenges, with the patient needing to be prone while intubated, sitting upright, or placed in the right lateral decubitus position. Timing of sample acquisition can be adequately achieved with an inspiratory or expiratory hold with the ventilator. Patients with ventricular assist devices require near-constant anticoagulation therapy and therefore withholding anticoagulation in these patients introduces considerable risk. ►Francoz C, Glotz D, Moreau R, Durand F. The evaluation of renal function and disease in patients with cirrhosis. J Hepatol. 2010;52(4):605-613.►Hogan JJ, Mocanu M, Berns JS. The native kidney biopsy: update and evidence for best practice. Clin J Am Soc Nephrol. 2016;11(2):354-362. ★ ESSENTIAL READING►Piccoli GB, Daidola G, Attini R, et al. Kidney biopsy in pregnancy: evidence for counselling? A systematic review. BJOG. 2013;120(4):412-427. The risk for infection is minimal because the kidney biopsy is performed under sterile conditions. Estimated infection risks are reported to be as low as 0.2%. It can be increased in patients who have an underlying kidney infection or who are immunocompromised. Avoiding cutaneous areas that show signs of infection can help minimize this risk. Proper sterile technique should be maintained throughout the entire procedure by the physician performing the biopsy and, if applicable, by the ultrasonography operator. Blood pressure control is important when performing a kidney biopsy. A recent study of 293 patients undergoing kidney biopsy demonstrated a more than 10-fold increase in biopsy complication risk when systolic blood pressure was > 140 mm Hg and diastolic blood pressure was > 90 mm Hg. The risk for complications was further increased in patients who had blood pressure > 170 mm Hg (with an odds ratio of 23.3). Therefore, efforts should be made to decrease the blood pressure with either intravenous or oral antihypertensives before the biopsy. Oral blood pressure medications can be used, especially if the biopsy is nonurgent. Blood pressure should also be monitored immediately after the biopsy, with efforts to keep blood pressure < 140/90 mm Hg. In the postprocedure period, an elevated blood pressure that is refractory to treatment may be suggestive of a capsular hematoma and should warrant repeat imaging (see below for complications). Given the vascularity of the kidney, bleeding is a substantial risk in patients undergoing kidney biopsy and efforts should be made to mitigate this risk. Uremia, thrombocytopenia, and coagulopathies increase the risk for bleeding. As platelet levels decrease to <200 × 103/μL, there is an incremental increased risk for bleeding, with more significant bleeding occurring when platelets decrease to <120 × 103/μL. In patients with platelet levels < 80 to 100 × 103/μL, platelet transfusions can be used to bring platelet counts closer to normal if the operator believes it is necessary. An elevated INR should be reversed with vitamin K or fresh frozen plasma to help reduce the risk for bleeding, although the exact target has not been appropriately defined. Desmopressin (dose of 0.3 μg/kg) administered 1 half-hour before biopsy has also been recommended in patients with azotemia. A randomized study of 162 adults demonstrated decreased bleeding in patients using desmopressin relative to those assigned placebo. However, this study included patients with Scr levels of 1.5 mg/dL and estimated glomerular filtration rates > 60 mL/min/1.73 m2. Therefore, the utility of desmopressin in high-risk patients is unclear. After the procedure, the patient should remain supine for 4 to 6 hours. Overnight stay has not been shown to be more beneficial in reducing bleeding risks relative to those who are monitored for up to 6 hours. Although a third of complications still occur at more than 8 hours after the procedure, observation will identify a decrease in hemoglobin level and possibly result in increased transfusions, but it is unclear whether a longer stay will improve postbiopsy outcomes. The choice of an overnight observation should be at discretion of the physician perfo