Ultrasound of the urinary system
When is this exam indicated?
The study of the urinary system by ultrasound is indicated in those patients who present with a history of recurrent infections, macrohaematuria, a history of urolithiasis (stones in the urinary tract), renal insufficiency, lumbar colic or major urinary disorders.
Ultrasound can be used to measure the size of the individual kidneys, study their location and morphology, parenchymal thickness, and cortical to medullary ratio. Renal ultrasonography is an essential examination to distinguish liquid-containing structures (renal cysts) from solid masses.
It is particularly useful in the study of hydroureteronephrosis (by which we mean a dilatation of the excretory cavities of the kidney and ureter) and in the diagnosis of radiopaque and radiotransparent stones, which appear as hyperechogenic structures with a posterior cone of shadow, a typical feature of dense structures that cannot be crossed by the ultrasound beam. Through ultrasonography it is also possible to study the lower excretory system, and in particular the bladder. Bladder ultrasonography is used for the diagnosis of neoformations, diverticula or bladder stones and for the evaluation of the post-minctional residue. In order to improve the sensitivity of the method to identify suspected vegetative lesions, it is useful that the bladder walls are distended at the time of the examination. It is also possible to perform a morphological evaluation of the prostate and assess its size (this parameter is particularly important in patients who complain of urination disorders).
How is it performed?
The examination requires advanced ultrasound apparatus, equipped with a convex probe and the possibility of observing the blood flow in the form of colored images, using the physical phenomenon called "Doppler effect". The examination is performed with the patient in supine position. In order to better visualize the upper excretory tract, the patient might be asked to assume different positions (on his side, on the other side, on his stomach) or hold his breath. In order to better evaluate the bladder walls, it is helpful to have the bladder distended at the time of the examination.
However, there are several limitations to this method, such as the presence of anatomical barriers (bowel contents, bone structures) to the passage of ultrasound; the bladder is properly explored by this technique only if properly replete. The ureters cannot be explored except in the proximal and iuxtavesical tracts when they are dilated. Finally, it is a method where the diagnostic accuracy is closely related to the ability and experience of the clinician and the characteristics of the device.