Hydronephrosis - Pitalls
1. Extra-Renal Pelvis
This is a normal finding, seen in ~10% of population, that mimics hydronephrosis whereby the renal pelvis is not confined within the renal hilum. As such, the renal pelvis looks dilated and anechoic -- like hydronephrosis. However, the calyces are NOT dilated which differentiates it from hydronephrosis.
This is a normal finding, seen in ~10% of population, that mimics hydronephrosis whereby the renal pelvis is not confined within the renal hilum. As such, the renal pelvis looks dilated and anechoic -- like hydronephrosis. However, the calyces are NOT dilated which differentiates it from hydronephrosis.
Notice how the renal pelvis is dilated though there is no dilatation of the calyces. From another view, the renal pelvis is notably outside the kidney.
Here is another view of the same kidney which clearly shows the renal pelvis is external to the hilum with no calyceal dilatation.
2. Renal Cyst
This is not an uncommon finding. The renal cyst is usually a circular like hypoechoic structure most common found in the cortex though it can be seen in the medulla as well. The cyst can be simple (anechoic without septation) or complicated (echogenic and septated).
The way to distinguish this from hydronephrosis is that the the cyst DOES NOT connect with the renal pelvis. So it is imperative to sweep through to entire kidney in order to evaluate this properly.
This is not an uncommon finding. The renal cyst is usually a circular like hypoechoic structure most common found in the cortex though it can be seen in the medulla as well. The cyst can be simple (anechoic without septation) or complicated (echogenic and septated).
The way to distinguish this from hydronephrosis is that the the cyst DOES NOT connect with the renal pelvis. So it is imperative to sweep through to entire kidney in order to evaluate this properly.
A cyst is visualized at the inferior pole of the kidney. Although the cyst encroaches into the medulla, notice that it DOES NOT connect with the renal pelvis.
Here is the left kidney with a simple cyst located in the superior pole of the cortex. Again, it DOES NOT connect with the renal pelvis.
Take Home Message:
- Extra-renal pelvis and renal cyst can be mistaken as hydronephrosis
- With extra-renal pelvis, the renal calyces are NOT dilated
- With renal cyst, it does NOT connect with the renal pelvis