Few systematic data exist to estimate the complication rate of kidney biopsy. The current standard procedure for kidney biopsy involves the use of real-time ultrasound guidance and an automated spring-loaded biopsy device that may be associated with lower rates of procedural complications [10]. The bleeding complications include silent hematomas detected only by post-biopsy imaging (Fig. 12.5), macroscopic hematuria (Fig. 12.6), large hematomas and blood loss requiring erythrocyte transfusion (Fig. 12.7), arteriovenous fistula (Fig. 12.8), and, rarely, the need for emergent angiographic intervention (Fig. 12.9) or nephrectomy. The incidence of the complications associated with kidney biopsy and possible predictors fluctuates across studies, due to different definitions and patient selection, procedural technique, and monitoring protocol. A rare complication is the page kidney, caused by the accumulation of blood in the perinephric or subcapsular space resulting in extrinsic compression of the involved kidney, renal ischemia, activation of the renin-angiotensin-aldosterone system, and systemic hypertension [11].

In a recent systematic review and meta-analysis, the authors aimed to evaluate the incidence of hemorrhagic complication in terms of rates of macroscopic hematuria and the need for erythrocyte transfusion after native kidney biopsy performed with real-time ultrasound guidance and automated spring-loaded biopsy device and to identify potential risk factors [12]. The rate of macroscopic hematuria was 3.5 % and erythrocyte transfusion was 0.9 %. Significantly higher rates of transfusion were seen with the following covariates: 14-gauge compared with smaller needles (2.1 % vs 0.5 %), serum creatinine level greater than 2.0 mg/dl, female gender, acute kidney injury, mean age of 40 years or older, and mean systolic blood pressure greater than 130 mmHg. Although macroscopic hematuria and the need for erythrocyte transfusion are important complications of kidney biopsy because they may necessitate hospital admission and therefore increased health-care expenditure and patient morbidity, the most frequent bleeding complication of kidney biopsy, i.e., the perinephric hematoma, was not considered among principal outcomes of this study, since the presence of hematoma was reported inconsistently in source studies, with rates varying by whether ultrasonography was performed routinely or for symptoms. The rate of this complication increases remarkably when screened using computed tomography. Even though the majority of these hematomas are clinically asymptomatic, the presence of perinephric hematoma increases the discomfort for the patient and the costs due to further laboratory and instrumental examinations with longer hospitalization. In a minority of cases, the hematoma is a clinically relevant complication, which needs an even longer stay at the hospital for diagnostic and therapeutic procedures (artery embolization).

In conclusion the risk of hemorrhagic complications is relatively low with real-time ultrasound guidance and automated biopsy needles. However, to improve patient safety, the use of large-gauge needles (14 gauge) should be discouraged. Since the prognostic value of potential risk factors is debatable, further studies are necessary to find more sensitive tests to assess coagulation disorders and to better identify patient and procedural characteristics required to improve biopsy technique and patient selection in an effort to improve the safety profile of kidney biopsy. Finally, the use of DDAVP should be considered among modifiable procedure, since the only randomized controlled trial included in this review demonstrates the risk reduction of bleeding complication in treated group compared to controls [13]. A caution in the use of this drug should be considered in patients at thromboembolic risk.