Urogenital disorders

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

The examination workflow’s elaboration of the interpreted complex developmental defect case needs a careful consideration, because the verification of almost all defects are possible in various effective ways.

The developmental defects can be visualized by ultrasound, intravenous urography, (retrograde urography), CT and MR.

In case of vascular anomaly we angiography can be performed. MR and DSA is not appropriate to diagnose urolithiasis (even bigger, radiolucent stones are visible on DSA test during intervention if the injected contrast agent excretes, and the stones look like filling defects in the urinary system). Additional imaging methods are always capable to visualize the stone according to the situations.

The complex developmental defect seen on our preparate and onr of its part can be visualized in utero by ultrasound. The partial hydronephrosis and the extremely dilated ureter were already present apparently. The second ureter is too narrow to be visualized in foetal intrauterine examination. The consequently dilated, full bladder raises the possibility of developmental defect (mostly posterior urethra valve), too.

Ultrasound after birth is also the first choice of imaging modalities. In that time period the degree of hydronephrosis severity associated with dilated ureter can be assessed:

• - Gr 1.: the pelvis is dilated, but the calyces are normal. The parenchymal thickness is intact.

• - Gr 2.: both the pelvis and the calyces are dilated, the parenchyma is a bit thin.

• - Gr 3.: the pelvis is „cystically” dilated, the calyces cannot be recognised any more, the parenchyma is significantly thinned.

• - Gr 4.: „sack kidney”, the parenchyma is thinned so significantly, that it cannot be recognised.

Ultrasound visualizes the dilated ureter well, but the visualization of the thinner ureter –for good assessment - is usually less likely. The ureterolith comes with stone reflection and typical acoustic shadow due to the fact that it is located in the dilated ureter with abundant fluid. The US image of the ureterokele: it cambers into the bladder and looks like narrow contour lesion with sac: „cyst in the bladder”.

The ureter stone might be visualized on plain films, if it is big enough and adequately X-ray absorbing. In our case, most of the lesions of the preparate are soft tissues, thus these are not visible on plain film.

Hydronephrotic pyelon and ureter can be filled up using intravenous urography if there is an existing renal function in the parenchyma of the thicker ureter. Furthermore, the thinner ureter is also visible with its normal partial pyelon. Using the Weigert-Meyer-formula we can see the crossing of the two ureter because the insertion of the ureter, which arrives from the upper pole of the kidney, to the kidney is more caudal than the ureter of the lower pole (it is visible on our preparate). The protrusion of the dilated ureter’s end towards the bladder („cobra head sign”) can be surely visualized on the X-ray cystography which can be imaged after the examination. The interior surface of the kele is certainly ureter trace, whilst the outer surface is the bladder trace itself. X-ray transparent rim girdles around the dilated ureter end, thus the contrast filled urinary bladder can be separated from the contrast filled ureter’s shadow.

Megaloureter can be excellently visualized on CT urography and MRI scan. The another ureter of a smaller caliber can be detected as well by both imaging methods in addition to the dilated and normal pyelon parts belonging to the small ureter as well. Calcium containing kidney stone (ureterolith) can be seen already on the unenhanced CT examination. However, following contrast excretion this stone can be hidden in the hyperdense background. Accordingly, the small density difference between them does not allow the easy distinction of the calcium containing stone and the contrast material. Ureterokele can be detected easily already prior to the arrival of the contrast material to the bladder, however, it can be distinguished from the content of the filled up bladder later as well (cobra head).

Adventage of the MRI examination is that no contrast material is needed since the stationary fluid has a high signal on the strongly T2 weighted image. In this case, thick slices should be performed or reconstructed („slab”) on which the ureters, located dorsally in superior and caudally in ventral position, can be visualized in entire length along with the bladder. This image provides the perfect urography: above the dilated ureter we can observe the belonging hydronephrotic part with the dilated pyelon and calyces. Furthermore, remnants of the renal parenchyma can be also detected (according to the grade of hydronephrosis).

However, ureter stone can be not visualized directly by MRI (since moving protons are needed for MRI imaging. See the appropriate chapter). The larger ureter stone will be visible via its signal loss – indirectly – in the thick, fluid containing, hyperintense ureter. If the stone is small, the resolution is not enough that its signal loss could separate the very high signal intense urine, thus it cannot be visualized. However, the very thin, thinner ureter is well visible along with its belonging, normal pyelon. The entry point of the thick ureter into the bladder terminates in the kele which protrudes towards the bladder. It is visible in a similar appearence as with the above mentioned imaging methods.