Nephroliths and ureteroliths in cats: what radiography adds

Question

11-year-old spayed domestic shorthair queen at a senior health check, without clinical signs and with mildly increased creatinine. The radiograph shows small mineral opacities in both renal pelves and another 2 mm one in the retroperitoneum, caudal to the right kidney.

Which statement is correct?

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A. Most are struvite and dissolve with a dissolution diet

The vast majority of feline nephroliths and ureteroliths are calcium oxalate, which does not dissolve with diet.

B. If the radiograph shows the stones, ultrasound adds nothing

Ultrasound assesses whether there is obstruction (dilation of the pelvis and of the ureter proximal to the stone) and the renal parenchyma. It also detects small stones that radiography misses.

C. They are usually calcium oxalate and radiopaque, but radiography may miss small stones; combined with ultrasound, sensitivity increases greatly

Correct. Superimposition with the colon and small size limit radiography. Together, radiography and ultrasound detect most ureteroliths and show whether they are obstructive.

D. Every nephrolith should be removed surgically, even if it is not obstructive

Non-obstructive, non-infected nephroliths are usually monitored with imaging and bloodwork: nephrotomy damages parenchyma in kidneys that often already have chronic disease.

lightbulb Key takeaway

Include the whole retroperitoneum when radiographing cats with kidney disease: nephroliths and ureteroliths are common and nearly always calcium oxalate. An opacity along the ureteral path requires ultrasound to determine whether it is obstructive. Distinguish them from vascular or lymph node mineralisation and colonic content with the ventrodorsal view.

Which statement is correct?

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