Materials and Methods: From January 2014 to August 2016, 183 US-guided biopsies were performed in our institution on renal transplanted patients.
Over that period We decided to optimize our biopsy protocol, switching from the initial 24 hours hospitalization and observation period of every patient undergoing a graft biopsy to an outpatient protocol of 6 hours observation and discharge after blood count control. Furthermore, we evolved from an initially shared technique made by radiologists and nephrologist together to the current US guided biopsy performed by the nephrologist alone.
On the other hand we decided to change from the 14 G biopsy needle to the more suitable 16 G needle over the same period of time, being used on the outcome and the nephrologist alone protocols.
We retrospectively analyzed the results of those changes and compared outcomes of each group
Results:183 renal graft biopsies performed. 79,8%  by radiologist and nephrologist together. 20,2% by nephrologist alone. Outpatient protocol with 6 hours observation  performed on 51,4% of patients. 48,6% underwent programed admission and discharge after 24 hours observation. Automatic biopsy gun 14 G were used in 43,2%, 16 G in 37,7%, 18 G in 6%. 13,1%  needle information not recorded.
Mean age was 54 ± 14, 66,7% male. Mean needle passes  2 ± 1, mean number of useful samples 1,5 ±0,5. Mean pre-biopsy hemoglobin 11,5 ± 1,8 gr/dl, post-biopsy 10,9 ± 1,75 gr/dl, and  mean Hb change was 0,65 ± 0,62. Mean obtained glomeruli was 18 ± 11.
The 14 G biopsy gun was mainly used for the inpatient protocol ( 52%) and for the nephrologist and radiologist shared technique ( 54,8%), while 16 G biopsy gun was mainly used in outpatient cases ( 47%) and in all nephrologist independent technique cases.
The overall rate of complications was 7,7%. It was higher in the shared technique cases vs. Nephrologist independent cases ( 8,2 vs 5,4%). There were no differences between complications observed in the inpatient vs. outpatient cases ( 7,8 vs. 7,4%).
There were more complications observed in those biopsies using 14 G compared to 16 G  ( 11,2 vs. 4,3%)
Only one case ( 0,3%) required intravascular segmental embolization of transplanted kidney due to severe active bleeding after biopsy. There were no nephrectomies or deaths during the study period.
Conclusion: We observed fewer complications with appropriate sample obtainment using 16 G biopsy needle compared with 14 G.
We found no differences in complications rate between inpatient vs. outpatient with 6 hours of observation protocol.
We found less complications when biopsy performed by nephrologist alone compared with shared technique, although when comparing  only cases in which 16 G needle was used,  complication rates were similar.
We believe US-guided renal graft biopsy using 16 G needle, with only 6 hours of observation after procedure and performed by nephrologist alone is safe,efficient, cost-saving and optimizes the renal graft biopsy process.