Renal tract ultrasound in children

Ultrasound is a safe and non-invasive way of assessing the anatomy of the urinary tract in children. Renal tract ultrasound is one of the most commonly performed imaging examinations in paediatric radiology departments around the UK. Performing imaging investigations in children is often challenging and, together with the array of specific pathologies that may be encountered, necessitates a dedicated approach to obtain high quality diagnostic images. The majority of imaging in children therefore will be carried out either within a specialist children’s hospital or in a district general hospital by an imaging professional who has a specialist interest and experience in paediatric imaging. This specific approach begins before the patient arrives at hospital. The bladder should ideally be examined distended with urine although patients who are not potty trained will, of course, not be able to fill their bladder. However as the age of this varies, most parents of patients over the age of two years old will receive advice on bladder filling. On arrival at the radiology department it is important that children are kept calm as it is likely to be an unfamiliar and potentially frightening environment. A selection of toys for a variety of ages and if possible a play area make the process of waiting much easier and will mean children will be calmer for the examination. Once the patient arrives in the ultrasound room it is essential that the room is equipped properly. Most children’s hospitals will have further toys in the room as well as a selection of distraction devices such as projectors, mobiles, lights and a TV with a DVD player. Most modern ultrasound machines are capable of interrogating the urinary tract in children. However, specific considerations include the need for a wide variety of transducers to image the variety of sizes of children. The kidneys of a 500 gram pre-term neonate are ideally visualised with a high frequency linear array transducer (we use a 14KHz linear probe in premature neonates) whereas some larger teenagers will require a lower frequency, curvilinear probe for initial analysis followed by a higher frequency probe for more focal interrogation. It is essential to be able to use Duplex, power Doppler and pulse wave Doppler to assess renal vascular anatomy as well as to assess the ureteric jets within the bladder. These functions are now almost universal on modern ultrasound machines.