Renal transplantation is a unique chance to a normal life for end-stage renal disease patients, because of the perfect morphological and functional replacement of the lost kidneys. Serum creatinine and proteinuria reflect kidney allograft function, but they are nonspecific tools.Imaging techniques plays an important role in the detection of anatomical as well as functional abnormalities in the early stages.

Renal transplantation is a unique chance to a normal life for end-stage renal disease patients, because of the perfect morphological and functional replacement of the lost kidneys. It is also the only effective way of replacement of the endocrine function of the kidneys. The survival of kidney grafts has improved considerably in recent years, due to advances in surgical techniques and in immunosupression protocols . Although improvements in surgical techniques and immunosuppression have led to longer survival, complications remain common, occurring in approximately 12%-20% of patients. Post transplantation complications can also be divided following the renal transplant's time of evolution into early complications (acute tubular necrosis, acute rejection, arterial or venous thrombosis, obstruction, urinary leak, post transplantation collections and infection) and late complications (transplant artery stenosis, arteriovenous fistulas, drugs toxicity, chronic rejection and urinary tract infection). Acute rejection (AR) is a major risk factor for chronic nephropathy and graft loss after renal transplantation (RT) . Antibody-mediated rejection (AMR) is the most common cause of allograft failure in kidney transplant recipients (KTRs) . Serum creatinine and proteinuria reflect kidney allograft function, but they are nonspecific tools. Despite its limitations (being invasive procedure with increased risk of bleeding and infection), kidney graft biopsy remains the gold standard method for confirming antibody-mediated rejection . Whilst kidney graft dysfunction could present with an elevated serum creatinine level, oliguria or pain over the graft site, it could also be asymptomatic. Imaging techniques plays an important role in the detection of anatomical as well as functional abnormalities in the early stages, thus allowing the chance for early treatment, as well as in the late post transplant period . Post-transplant complications can be divided into categories following the imaging-based classification of renal transplant complications: Perinephric collections, parenchymal abnormalities, abnormalities of the collecting system and vascular complications . The use of ultrasound to assess morphologic changes allows for the accurate and early detection of early pathologic alterations that may lead to rejection . Correlation of the ultrasound pattern with patient's history and clinical background is essential for a correct characterization. However, there are several limitations to ultrasound including its inability to assess renal function or differentiate between the different causes of renal dysfunction . Color Doppler ultrasonography, on the other hand, gives valuable information on the hemodynamics of the grafts' renal arteries. In the early post-transplant period, the resistive index(RI) measured in intrarenal arteries is thought to predict poor kidney graft performance . Doppler indices in different arteries differ in the detection of early parenchymal renal transplant complications. Resistive index of the interlobar artery proved to be more specific in the detection of early cases of parenchymal complications in a renal transplant patient . Color Doppler sonography had a limited value in the differentiation among the various etiologies of renal transplant dysfunction however the mean RI values were above normal in acute rejection and ATN . Vitamin D deficiency or vitamin D insufficiency is common and conflicting results concerning vitamin D deficiency -associated graft failure and mortality were described in kidney transplant recipients (KTRs). Many studies showed that Vitamin D deficiency , measured as 25-hydroxyvitamin D [25(OH)D] or 1,25-dihydroxyvitamin D [1,25(OH)2D], relates to kidney dysfunction in renal disease and graft loss in kidney transplant recipients . The association between low 1,25(OH)2D and graft failure was seen and was dependent on renal function. This association is not unexpected since the 1a-hydroxylase of the kidney, i.e., the enzyme that converts 25(OH)D into 1,25(OH)2D, is damaged simultaneously with the deterioration of renal function.

Inclusion Criteria:

• All pediatric patients aged 1 to 18 years old
• first renal transplant during the first year, pre and post complications.

Exclusion Criteria:

• patients with recurrent renal transplantation.
• Parental refusal to participate.
• Patients with chronic rejection

All pediatric renal transplant recipients in their first year of transplantation.