I./3. fejezet: Radiology aspects of complex urinary tract lesions

Karlinger Kinga

I./3.1.: Introduction to imaging methods in urology

In this respect, we need to know the advantage of each imaging method to recognize the complex developmental defect’s morphologic lesions which appear on the product. Moreover, we need to respect – the thing is usually babies - especially the increased radiation doses caused by many imaging modalities and different kind of interventions (for example general anesthesia) which are necessary for the examination.

In urology it can’t be overemphasized - like in other abdominal bias - that ultrasound (US) is the basic imaging method in children.

What can wee see using US?

The localisation, shape, size of kidney and the thickness of renal parenchyma can be imaged/measured well. The solid lesions of the kidney can be assessed whether it is solid or cystic, furthermore, septation of cysts can be also settled using US. The dilation of the renal pyelon can be also measured. It gives further reliable information about the reflective stones. We can image the pararenal structures using this method. The wall thickness (accidentally irregular) of the full urinary bladder located in the pelvis, wall growths, diverticulum formation or bladder stone can be imaged well, as well as the amount of rest urine in the bladder which can be also assessed. The duplex US demonstrates the accidentally changed parenchymal circulation circumstances (cancer, inflammation). Doppler function helps to register the velocity changes caused by the renal artery stenosis.

The plain abdominal X-ray image provides additional information, for example size of kidney, radio-opaque stone (kidney, ureter, bladder, prostate), calcification (phlebolith, myoma), contour of psoas muscle and spine diseases.

The intravenous injected iodine contrast material allows us to collect information about the morphologic circumstances of the urinary tract through it’s renal absorption (in case of good renal function). It is called intravenous urography (nowadays we perform it very rarely and just in reasonable cases!).

It provides information about the excretional function, the location, shape, size, the cortical thickness of the kidneys, about the shape of the kidney pelvises/calyxes, about the accidental blockage of the urine ullage, about the spaciousness of the ureters and filling of the urinary bladder, its interior shadows and about the residual fluid after miction as well.

If the intravenous urography can not be carried out (for ex. GFR < 60), the urologist performs the retrograde ureteropyelography with the same water soluble iodinated contrast agent. This test reveals the contour irregularities of the ureters and the filled-up pyelon contours. Nowadays they combine this test with endoscopic inspection. The retrogradely performed cysto- and urethrography is also achieved by the urologist by recording X-ray images.

Mictional cystoureterography (MCU) can be perfomed by a renal excreted (or by retrogradely filled) contrast agent, but isotope technique is also preferred which has less radiation and registers the ureteral reflux better (using the isotope technique there is no contraindication in the reduced kidney function's point of view, moreover, it can be also registered separately, too). Furthermore, daily used, harmless contrast enhanced ultrasound test is also preferred.

In virtue of its complexity, CT sweeped among the imaging modalities, it replaced the urography in most places and respects already, but we always need to consider the amount of radiation.

The location, shape, size, the cortical thickness of the kidneys can be assessed by CT certainly. CT provides information about the thickness and density of the renal parenchyma, respectively. The information on density and contrast enhanhancement’s pattern of incidental space occupying lesions is a thoughtful differential diagnostic help.

We use the same intravenous contrast agent in CT examination like in intravenous urography, thus the excretional function of the kidneys can be also fairly assessed.

The renal pelvis, the placement and dilatation of ureters can be faily examined. We can reach urographic effect with „thickened slices” in CT images. The caliber of renal vessels, the number of veins and it’s accidental thrombosis can be also assessed.

MR imaging with its good tissue resolution, complex and optional plain representation capability is perfectly suitable to visualize these kind of morphologic changes. However, it is not available everywhere and getting asleep/monitoring the babies in the gantry is mostly a very toughish task.

Its advantage is that we do not need to administer contrast material in order to register simple anatomic variations. The urine containing urinary tract gives enough contrast to the pyelographic effect with strong T2-weighting]. It cannot visualize the „dry” materials (for ex. stone), but these materials, for example in ureter of in urine bladder, are easily recognizable signproof areas (we need to distinguish from for ex. the air bubble). Otherwise it provides similar anatomic informations as CT. We need take into consideration that the administered contrast material (Gadolinium) is not the same like as of CT, but the good renal function is also required too to prevent the long harmful effects of contrast agents.

We perform angiography (DSA) in cases if it is (very likely) followed by intervention (for ex. balloon expansion of arterial stenosis, tumor embolisation) and in case of bleeding of renal origin of unknown background (arterial malformation).

The chapter structure

• I./3.1.: Introduction to imaging methods in urology

• I./3.2.: The analysis of the interpreted case in radiologic investigation’s workflow aspect

• I./3.3.: Hydronephrosis in a radiologist point of view

• I./3.4.: Take home messages

References