**5. Complications**

Complications related to the graft following a renal transplant can be didactically divided into medical complications (MC), urological complications (UC) including fluid collections (FC), and vascular complications (VC). Neoplasms (NEO), and recurrent native renal disease are also complications that can occur but in minor incidence. The most common complications of renal transplantation are discussed bellow and listed in Table 1.

#### **5.1. Medical complications**

In the early post-transplant period, delayed graft function (DGF) occurs when the decline of the serum creatinine concentration is slower than wanted. The most common medical complications (MC) related to DGF are acute tubular necrosis (ATN), drug toxicity (mainly causes by calcineurin inhibitors - CNI), and rejection. In general, imaging tools in evaluating MC following renal transplantation are non-specific [24-26]. The major role of imaging in this setting is to exclude urologic, collections, and/or vascular complications. To date, quantitative criteria for the diagnosis of acute graft dysfunction with MR renography or nuclear medicine have not been adequately standardized. Promising techniques, especially using quantitative and functional MRI are objects of interest in this field [14, 27, 28].
