Ultrasound is the primary imaging modality after kidney transplantatio
n. Its general availability and the absence of radiation exposure and
discomfort for the patient also make it a suitable procedure for follo
w-up. Simple B-mode sonography provides comprehensive information on t
he morphology of the renal transplant and surrounding structures, whil
e color-coded duplex sonography (CCDS) additionally allows assessment
of the anastomoses and organ perfusion. More recent technical advances
such as power Doppler ultrasound appear to improve in particular the
assessment of peripheral circulation. The possibilities and limitation
s of the various sonographic techniques in the evaluation of kidney tr
ansplants are discussed with special reference to the most important c
linical aspects and some basic technical concepts.