# Renal Imaging: Select the Modality for the Question

Review results, arrange needed follow-up, and ensure that important incidental findings do not disappear between teams.

![Infographic: Renal Imaging: Select the Modality for the Question](https://urinenephrology.org/visual-reference/images/mastery-renal-imaging.png?v=20261003c)

## Different tests reveal different things

Ultrasound, CT, MRI, Doppler, and nuclear techniques assess structure, obstruction, vessels, masses, or function with different strengths.

## Match modality to the question

Use ultrasound for kidney size, bladder retention, and hydronephrosis; a noncontrast CT protocol is useful for many stone questions. Suspected infarction, vascular disease, or a renal mass needs a different targeted protocol. Tell radiology the diagnosis being tested rather than requesting a generic renal scan.

## Assess tradeoffs

Consider radiation, contrast, pregnancy, hemodynamic stability, kidney function, and the consequences of a missed diagnosis. Contrast-associated and contrast-induced injury are not interchangeable terms.

## Interpret a negative study within its limits

Ultrasound without hydronephrosis does not exclude very early or nondilated obstruction. A noncontrast stone CT does not reliably exclude renal infarction. If the clinical stakes remain high, discuss the appropriate next study or urologic evaluation instead of repeating the same insensitive test.

## Communicate the uncertainty

Ask radiology for a targeted protocol and explain the clinical concern. Incidental cysts or small abnormalities require context before becoming diagnoses.

## Close the loop

Review results, arrange needed follow-up, and ensure that important incidental findings do not disappear between teams.

## Source lessons

- [renal imaging](https://urinenephrology.org/mastery/ckd-advanced/renal-imaging.html)

Read alongside the full lessons; the findings and decisions shown here require the stated clinical context.