Relatively radiolucent stones are a potential blind spot for low dose CT. It was tempting to read the low dose CT as "no renal stone", but when comparing with prior studies there had been a shadowing calculus at the interpolar kidney. When looking at the most recent CT available before that, there was a faintly hyperattenuating area at an interpolar kidney medullary pyramid tip.

Although uncommon, this suggested that the patient may have a radiolucent stone / matrix / medication-induced stone. On review of the patient's chart he had been administered antiretrovirals (dolutegravir/rilpivirine), and this class of medications has been associated with matrix stones.