Renal biopsy is an integral part of diagnosis which decides the course of treatment of kidney diseases. However, it is not without risk of complications. Studies on traditional risk factors like elderly age, higher BMI, lower eGFR and presence of coagulation abnormalities have provided insights into making the procedure of kidney biopsy more safe [3,4,5, 7, 16]. However, very few studies have sought to correlate sonological parameters of the kidney like kidney length, renal cortical and parenchymal thickness, and renal parenchymal changes by ultrasonography—to renal biopsy complication [8, 9]. A limited number of studies have actively surveyed for haematoma and looked for its correlation to biopsy complications. We have, in our present study, examined the correlation of traditional as well as the renal sonological risk factors with post-renal biopsy complications. Furthermore, we conducted an active surveillance for asymptomatic haematomas in order to correlate the size of haematomas with the development of other complications.

Our study has a lower rate of major complications which is comparable to other studies [5, 17,18,19] including gross haematuria not requiring intervention [16], blood transfusion [4, 17, 20] and hypotension requiring IV fluids for resuscitation [17, 21]. We also observed haematomas in 41.25% of the cases—higher than reported in other studies [16, 17] which resulted in an apparently higher percentage of minor complications in this study. The difference observed could be because other studies only screened for haematomas which were clinically significant, while, in our study, we carried out an active surveillance for haematomas which were, by and large clinically silent. A meta-analysis found that studies which actively screened for haematomas have reported more number of haematomas than studies where active surveillance was not carried out [16]. When CT scans were carried out immediately post-renal biopsy, haematoma was observed in 50% of the cases in such studies [22].

In our study, 83.33% of the haematomas were observed immediately after biopsy, 15.5% new-onset haematomas were observed at 12 h post-biopsy and only 1% of new-onset haematomas were found to occur between 12 and 24 h post-renal biopsy, i.e. a total 99% of the haematomas were detected by 12 h after renal biopsy. This finding is similar to the observations of Simard-Meilleur et al. where 84% of the complications were detected by the first 8 h, 86% by 12 h and 94% by 24 h after renal biopsy [23]. Whittier et al. also found that 85% of the complications are detected at ≤ 12 h post-renal biopsy and 89% by ≤ 24 h [19]. Marwah et al. in their study also found that most of the renal biopsy complications (95%) were detected within 12 h post-renal biopsy [24]. Further correlation of the haematoma size with the risk of development of other renal biopsy complications revealed that size of haematoma of > 1.17 cm immediately post-renal biopsy and > 1.2 cm at 12 h post-renal biopsy were sensitive predictors of a need for blood transfusion; however, the specificity for the same was ~ 70%.

Kidney bipolar length did not show any correlation with increased risk of renal biopsy complication in our study. Many previous studies such as by Roger et al. [25], Jiang et al. [26] and Trajceska et al. [3] reported that a smaller kidney size was associated with higher risk of percutaneous renal biopsy complication. This difference in observation may be due to our strict screening methods, where we deferred from doing biopsies of patients with kidney size < 8.5 cm as they were reflective of kidney with CKD. The mean kidney length in our study was 9.67 ± 0.91 cm. Even among the complications group, the mean kidney length was 9.59 ± 0.90 cm. Renal cortical thickness and renal parenchymal thickness were significantly different among the complications and no complications groups. A study by Zhang et al. found patients with renal parenchymal thickness < 1.5 cm to be at a higher risk for a renal biopsy complication [8]. Mejía-Vilet et al. found that renal cortical thickness < 0.8 cm was associated with chronic renal changes and more likely to have a bleeding complication post-renal biopsy [9]. The study also found that patients with higher grade renal parenchymal changes and poor cortico-medullary differentiations of the kidney on ultrasonography were associated with CKD and were more likely to have a higher risk of renal biopsy complications. In our study, however, on multivariate analysis, there was no significant difference between the no complications and complications groups. This may be due to our stringent screening practices, where we deferred renal biopsy of patients with thinner renal parenchyma or lesser cortical thickness in anticipation of complications. Renal parenchymal changes were statistically different between the complications and no complications groups, with a higher grade of renal parenchymal changes (grade 2 and grade 3) being associated with a higher risk of renal biopsy complication. This could be because a higher grade of renal parenchymal change is associated with chronic renal changes such as seen in CKD and hence, pose greater bleeding risk on biopsy.

Similar to other studies, traditional risk factors like older age, higher blood urea, lower eGFR and native kidney biopsy, haemoglobin fall at 12 h, haematocrit % fall at 6 and 12 h post-biopsy, severe IFTA on biopsy, in our study were indicative of a risk of renal biopsy complication [3, 4, 17, 27,28,29]. However, gender, BMI, kidney biopsy by trainee/consultant, blood pressure and comorbidities like hypertension/diabetes, pre-biopsy haemoglobin and platelets, proteinuria, coagulation profile, antiplatelet use and number of passes taken were not significantly different between any of the groups.

The strength of our study is that it is one of the few studies to look for association between the renal sonological parameters and the renal biopsy complications. Furthermore, we have carried out an active surveillance for haematomas post-renal biopsy and analysed this for predicting post-renal biopsy complications.