Case of the month: January 2025

Figure 1

A 75 year-old female was referred to the nephrology clinic for evaluation of kidney stones and cysts. A ultrasound performed in the clinic showed hyperechoic foci with acoustic shadowing in each kidney consistent with stones (Fig. 1 and 2).

Figure 2

In addition, several cystic areas were seen (Fig. 3).

Figure 3

A key finding was that the medullary pyramids, which are normally less echogenic than the cortex, were echogenic (Fig. 4), indicating some process within the medulla.

Figure 4

The differential diagnosis includes interstitial nephritis, nephrocalcinosis, gouty kidney, and medullary sponge kidney. There is no shadowing from the medullae, which is inconsistent with nephrocalcinosis. A closer look at the “stones” revealed that they were located at the apices of the pyramids, in other words, in the papillae, indicating that they are likely to be calcified papillae. This can be the initial finding in papillary necrosis.

Figure 5

Closer inspection of the “cysts” reveals that they are located within the echogenic medullae (Figure 5).

This is also apparent when you zoom in on Fig. 1 (right). Thus, these cysts are actually papillary cavities. These findings are typical for analgesic nephropathy. When asked during the sonogram, the patient admitted to chronic back pain with a long history of NSAID use.

This case illustrates several points. First, not all echogenic foci with shadows are stones. Second, not all cystic lesions are simple cysts. Lastly, and most importantly, this case illustrates the importance of nephrologists performing and interpreting renal ultrasounds. A differential diagnosis often needs to be established during the exam, along with immediate clinical correlation, in order to guide and focus the examination.

Case of the month: December 2024

A 41 y.o. female with a history of bilateral stone disease resulting in a right nephrectomy in the past. An ultrasound was performed in the renal clinic.

A stone is present in the lower pole (black arrow) on a longitudinal image. Note that there is large shadow (white arrows) not emanating from the stone, without an obvious source.

The renal parenchyma is thin, indicative of chronic damage, and there is some dilatation of the renal pelvis and proximal ureter.

On further longitudinal imaging, there is an echogenic focus within the renal pelvis (while arrow) that is distinct from the lower pole stone (black arrow).

This was confirmed on transverse imaging through the mid kidney.

In the bladder, transverse imaging revealed two separate echogenic structures that appeared connected on longitudinal imaging. While stones can be present in the bladder, they should either be affixed to the wall or lie against the dependent surface.

On further questioning, the patient recalls that there may have been a stent inserted in the left ureter in the past. This would explain the shadow of unapparent source, the additional echogenic focus in the renal pelvis and the findings in the bladder. Stents are often not visible on sonograms due to their variable relationship to the sound beam. The mild dilatation of the renal pelvis and proximal ureter is common with stents unless the bladder is empty. So instead of multiple stones, this patient probably has just one stone. This was confirmed on a subsequent CT scan.

This case illustrates several important points:

• sonography often requires interpretation and clinical correlation during the study, which is one reason why nephrologists should be performing renal ultrasounds.

• Not every echogenic structure with shadowing is a stone.

• The bladder should always be examined.