Multi-modality imaging review of congenital abnormalities of kidney and upper urinary tract

Abstract

Congenital abnormalities of the kidney and urinary tract (CAKUT) include a wide range of abnormalities ranging from asymptomatic ectopic kidneys to life threatening renal agenesis (bilateral). Many of them are detected in the antenatal or immediate postnatal with a significant proportion identified in the adult population with varying degree of severity. CAKUT can be classified on embryological basis in to abnormalities in the renal parenchymal development, aberrant embryonic migration and abnormalities of the collecting system. Renal parenchymal abnormalities include multi cystic dysplastic kidneys, renal hypoplasia, number (agenesis or supernumerary), shape and cystic renal diseases. Aberrant embryonic migration encompasses abnormal location and fusion anomalies. Collecting system abnormalities include duplex kidneys and Pelvi ureteric junction obstruction. Ultrasonography (US) is typically the first imaging performed as it is easily available, non-invasive and radiation free used both antenatally and postnatally. Computed tomography (CT) and magnetic resonance imaging (MRI) are useful to confirm the ultrasound detected abnormality, detection of complex malformations, demonstration of collecting system and vascular anatomy and more importantly for early detection of complications like renal calculi, infection and malignancies. As CAKUT are one of the leading causes of end stage renal disease, it is important for the radiologists to be familiar with the varying imaging appearances of CAKUT on US, CT and MRI, thereby helping in prompt diagnosis and optimal management.

Keywords: Congenital abnormalities; Kidney; Urinary tract; Multi cystic dysplastic kidneys; Pelvi ureteric junction obstruction; Computed tomography urography; Congenital abnormalities of the kidney and urinary tract; End stage renal disease; Horse shoe kidneys

Core tip: Congenital abnormalities of the kidney and urinary tract (CAKUT) are one of the leading causes of end stage renal disease. They can be classified on embryological basis in to three major categories: (1) abnormalities in the renal parenchymal development; (2) aberrant embryonic migration; and (3) abnormalities of the collecting system. Ultrasonography, computed tomography and magnetic resonance imaging are the primary imaging modalities used in the detection of various CAKUT. Clinical features vary widely depending on the type, severity and laterality of renal anomaly. Timely diagnosis is crucial in selected anomalies to minimize renal damage, prevent or delay the onset of end stage renal disease (ESRD), and provide supportive care to avoid complications of ESRD.