Patients with severe tophaceous gout are likely to have monosodium urate crystal deposits visible on ultrasound images of the renal medulla, researchers have reported in Annals of the Rheumatic Diseases.
The findings suggest that renal ultrasound can be used instead of CT to diagnose these deposits.
This report describes the use of dual-energy CT scans and ultrasonography to reveal widespread crystal deposition in the renal medulla of 2 patients with severe gout. Patient 1, a 50-year-old French man with severe tophaceous gout and frequent flares, was poorly adherent to urate-lowering medications. A CT scan of his lower back due to persistent lower back pain revealed urate deposits in his intervertebral discs and renal medulla. Doctors then performed a renal ultrasound, which revealed normal cortical echogenicity and renal size but strong hyperechogenicity with massive acoustic shadowing on both medulla. On Doppler mode, doctors also saw twinkling artefacts typical for microcrystalline deposits.
Patient 2, a 40-year-old Vietnamese man who experienced his first gout flare in 2014 and his first tophus in 2015, had never received urate-lowering medications as of June 2018, despite reporting a number of acute flares per month.
The CT scan and radiographs showed dense crystal deposits in the medulla, and ultrasonography showed reduced kidney length and a strongly hyperechogenic medulla with numerous twinkling artefacts and posterior acoustic shadowing.
Study investigators conclude that “[ultrasound] examination, which is cheaper and more available than [dual-energy] CT, is routinely used to look for urinary stones in gout. These two cases show that [ultrasound] examination can also be used to detect crystal deposition in the renal medulla, a classical but somewhat forgotten feature of the gouty kidney.”
REFERENCE: Bardin et al. Renal medulla in severe gout: typical findings on ultrasonography and dual-energy CT study in two patients. Ann Rheum Dis. 2018. https://ard.bmj.com/content/early/2018/09/26/annrheumdis-2018-214174