User login
Is gouty nephropathy real? It’s a question that has been posed often in rheumatology over the last several decades.
A new study found 36% of patients with untreated gout at a medical center in Vietnam have diffuse hyperechoic renal medulla as seen on ultrasound, which could indicate the presence of microcrystalline nephropathy. However, the results, published in Kidney International, may raise more questions than answers about the existence of gouty nephropathy and its relation to chronic kidney disease (CKD).
In their study, Thomas Bardin, MD, of the department of rheumatology at Lariboisière Hospital in Paris and colleagues evaluated 502 consecutive patients from Vien Gut Medical Center in Ho Chi Minh City, Vietnam, using B-mode renal ultrasound. The patients were mostly men with a median age of 46 years, body mass index of 25 kg/m2, estimated disease duration of 4 years, and uricemia of 423.2 micromol/L (7.11 mg/dL). Patients had a median estimated glomerular filtration rate (eGFR) of 78 mL/min per 1.73 m2. There was a history of hypertension in 112 patients (22.3%), type 2 diabetes in 58 patients (11.5%), renal lithiasis in 28 patients (5.6%), and coronary heart disease in 5 patients (1%).
While 39% of patients had previously used allopurinol for “a generally short period,” patients were not on urate-lowering therapy at the time of the study. Clinical tophi were present in 279 patients (55.6%), urate arthropathies in 154 patients (30.7%), and 43 patients (10.4%) used steroids daily.
B-mode renal ultrasound showed 181 patients (36%; 95% confidence interval, 32%-40%) had “hyperechoic pattern of Malpighi pyramids compared with the adjacent cortex,” which was “associated with twinkling artifacts” visible on color Doppler ultrasound. There was a significant association between renal medulla hyperechogenicity and patient age, disease duration, use of steroids, clinical tophi, and urate arthropathy (P less than .0001 for all). A significant association was also seen between renal medulla hyperechogenicity and decreased eGFR (P < .0001), proteinuria (P = .0006), leukocyturia (P = .0008), hypertension (P = .0008), hyperuricemia (P = .002), and coronary heart disease (P = .006).
In a multivariate analysis, there was a significant association between renal medulla hyperechogenicity and clinical tophi (odds ratio, 7.27; 95% CI, 3.68–15.19; P < .0001), urate arthropathy (OR, 3.46; 95% CI, 1.99–6.09; P < .0001), estimated gout duration (OR, 2.13; 95% CI, 1.55–2.96; P < .0001), double contour thickness (OR, 1.45; 95% CI, 1.06–1.97; P < .02), and eGFR (OR, 0.30; 95% CI, 0.09–0.89; P < .034).
“The finding was observed mainly in tophaceous gout, which involved a large proportion of our patients who had received very little treatment with urate-lowering drugs and was associated with moderately impaired renal function and urinary features compatible with tubulointerstitial nephritis,” Dr. Bardin and colleagues wrote in the study. The researchers also found “similar features” in 4 of 10 French patients at the Paris Necker Hospital in Paris, and noted that similar findings have been reported in Japan and Korea, which they said may mean hyperechoic medulla “is not unique to Vietnamese patients.”
Relation to CKD still unclear
In a related editorial, Federica Piani, MD, and Richard J. Johnson, MD, of the division of renal diseases and hypertension at the University of Colorado at Denver, Aurora, explained that gout was considered by some clinicians to be a cause of CKD in a time before urate-lowering therapies, because as many as 25% of patients with gout went on to experience kidney failure and about half experienced lower kidney function.
The association between gout and CKD was thought to be attributable to “frequent deposition of urate crystals in the tubular lumens and interstitium in the outer medulla of these patients,” but the concept was later challenged because “the crystals were generally found focally and did not readily explain the kidney damage.”
But even as interest in rheumatology moved away from the concept of gouty nephropathy to how serum uric acid impacts CKD, “the possibility that urate crystal deposition in the kidney could also be contributing to the kidney injury was never ruled out,” according to Dr. Piani and Dr. Johnson.
Kidney biopsies can sometimes miss urate crystals because the crystals dissolve if alcohol fixation is not used and because the biopsy site is often in the renal cortex, the authors noted. Recent research has identified that dual-energy CT scans can distinguish between calcium deposits and urate crystals better than ultrasound, and previous research from Thomas Bardin, MD, and colleagues in two patients noted a correlation between dual-energy CT scan findings of urate crystals and hyperechoic medulla findings on renal ultrasound.
The results by Dr. Bardin and associates, they said, “have reawakened the entity of urate microcrystalline nephropathy as a possible cause of CKD.”
Robert Terkeltaub, MD, professor of medicine at the University of California, San Diego, and section chief of Rheumatology at the San Diego VA Medical Center, said in an interview that he also believes the findings by Dr. Bardin and associates are real. He cited a study by Isabelle Ayoub, MD, and colleagues in Clinical Nephrology from 2016 that evaluated kidney biopsies in Germany and found medullary tophi were more likely to be present in patients with CKD than without.
“Chronic gouty nephropathy did not disappear. It still exists,” said Dr. Terkeltaub, who was not involved in the study by Dr. Bardin and colleagues.
The prospect that, if “you look hard enough, you’re going to see urate crystals and a pattern that’s attributed in the renal medulla” in patients with untreated gout is “very provocative, and interesting, and clinically relevant, and merits more investigation,” noted Dr. Terkeltaub, who is also president of the Gout, Hyperuricemia and Crystal-Associated Disease Network.
If verified, the results have important implications for patients with gout and its relationship to CKD, Dr. Terkeltaub said, but they raise “more questions than answers.
“I think it’s a really good wake-up call to start looking, doing good detective work here, and looking especially in people who have gout as opposed to just people with chronic kidney disease,” he said.
The authors reported no relevant conflicts of interest. Dr. Johnson, who coauthored an accompanying editorial, reported having equity in XORTX Therapeutics, serving as a consultant for Horizon Pharma, and having equity in Colorado Research Partners LLC. Dr. Terkeltaub reported receiving a research grant from AstraZeneca in the field of hyperuricemia and consultancies with AstraZeneca, Horizon, Sobi, Selecta Biosciences.
Is gouty nephropathy real? It’s a question that has been posed often in rheumatology over the last several decades.
A new study found 36% of patients with untreated gout at a medical center in Vietnam have diffuse hyperechoic renal medulla as seen on ultrasound, which could indicate the presence of microcrystalline nephropathy. However, the results, published in Kidney International, may raise more questions than answers about the existence of gouty nephropathy and its relation to chronic kidney disease (CKD).
In their study, Thomas Bardin, MD, of the department of rheumatology at Lariboisière Hospital in Paris and colleagues evaluated 502 consecutive patients from Vien Gut Medical Center in Ho Chi Minh City, Vietnam, using B-mode renal ultrasound. The patients were mostly men with a median age of 46 years, body mass index of 25 kg/m2, estimated disease duration of 4 years, and uricemia of 423.2 micromol/L (7.11 mg/dL). Patients had a median estimated glomerular filtration rate (eGFR) of 78 mL/min per 1.73 m2. There was a history of hypertension in 112 patients (22.3%), type 2 diabetes in 58 patients (11.5%), renal lithiasis in 28 patients (5.6%), and coronary heart disease in 5 patients (1%).
While 39% of patients had previously used allopurinol for “a generally short period,” patients were not on urate-lowering therapy at the time of the study. Clinical tophi were present in 279 patients (55.6%), urate arthropathies in 154 patients (30.7%), and 43 patients (10.4%) used steroids daily.
B-mode renal ultrasound showed 181 patients (36%; 95% confidence interval, 32%-40%) had “hyperechoic pattern of Malpighi pyramids compared with the adjacent cortex,” which was “associated with twinkling artifacts” visible on color Doppler ultrasound. There was a significant association between renal medulla hyperechogenicity and patient age, disease duration, use of steroids, clinical tophi, and urate arthropathy (P less than .0001 for all). A significant association was also seen between renal medulla hyperechogenicity and decreased eGFR (P < .0001), proteinuria (P = .0006), leukocyturia (P = .0008), hypertension (P = .0008), hyperuricemia (P = .002), and coronary heart disease (P = .006).
In a multivariate analysis, there was a significant association between renal medulla hyperechogenicity and clinical tophi (odds ratio, 7.27; 95% CI, 3.68–15.19; P < .0001), urate arthropathy (OR, 3.46; 95% CI, 1.99–6.09; P < .0001), estimated gout duration (OR, 2.13; 95% CI, 1.55–2.96; P < .0001), double contour thickness (OR, 1.45; 95% CI, 1.06–1.97; P < .02), and eGFR (OR, 0.30; 95% CI, 0.09–0.89; P < .034).
“The finding was observed mainly in tophaceous gout, which involved a large proportion of our patients who had received very little treatment with urate-lowering drugs and was associated with moderately impaired renal function and urinary features compatible with tubulointerstitial nephritis,” Dr. Bardin and colleagues wrote in the study. The researchers also found “similar features” in 4 of 10 French patients at the Paris Necker Hospital in Paris, and noted that similar findings have been reported in Japan and Korea, which they said may mean hyperechoic medulla “is not unique to Vietnamese patients.”
Relation to CKD still unclear
In a related editorial, Federica Piani, MD, and Richard J. Johnson, MD, of the division of renal diseases and hypertension at the University of Colorado at Denver, Aurora, explained that gout was considered by some clinicians to be a cause of CKD in a time before urate-lowering therapies, because as many as 25% of patients with gout went on to experience kidney failure and about half experienced lower kidney function.
The association between gout and CKD was thought to be attributable to “frequent deposition of urate crystals in the tubular lumens and interstitium in the outer medulla of these patients,” but the concept was later challenged because “the crystals were generally found focally and did not readily explain the kidney damage.”
But even as interest in rheumatology moved away from the concept of gouty nephropathy to how serum uric acid impacts CKD, “the possibility that urate crystal deposition in the kidney could also be contributing to the kidney injury was never ruled out,” according to Dr. Piani and Dr. Johnson.
Kidney biopsies can sometimes miss urate crystals because the crystals dissolve if alcohol fixation is not used and because the biopsy site is often in the renal cortex, the authors noted. Recent research has identified that dual-energy CT scans can distinguish between calcium deposits and urate crystals better than ultrasound, and previous research from Thomas Bardin, MD, and colleagues in two patients noted a correlation between dual-energy CT scan findings of urate crystals and hyperechoic medulla findings on renal ultrasound.
The results by Dr. Bardin and associates, they said, “have reawakened the entity of urate microcrystalline nephropathy as a possible cause of CKD.”
Robert Terkeltaub, MD, professor of medicine at the University of California, San Diego, and section chief of Rheumatology at the San Diego VA Medical Center, said in an interview that he also believes the findings by Dr. Bardin and associates are real. He cited a study by Isabelle Ayoub, MD, and colleagues in Clinical Nephrology from 2016 that evaluated kidney biopsies in Germany and found medullary tophi were more likely to be present in patients with CKD than without.
“Chronic gouty nephropathy did not disappear. It still exists,” said Dr. Terkeltaub, who was not involved in the study by Dr. Bardin and colleagues.
The prospect that, if “you look hard enough, you’re going to see urate crystals and a pattern that’s attributed in the renal medulla” in patients with untreated gout is “very provocative, and interesting, and clinically relevant, and merits more investigation,” noted Dr. Terkeltaub, who is also president of the Gout, Hyperuricemia and Crystal-Associated Disease Network.
If verified, the results have important implications for patients with gout and its relationship to CKD, Dr. Terkeltaub said, but they raise “more questions than answers.
“I think it’s a really good wake-up call to start looking, doing good detective work here, and looking especially in people who have gout as opposed to just people with chronic kidney disease,” he said.
The authors reported no relevant conflicts of interest. Dr. Johnson, who coauthored an accompanying editorial, reported having equity in XORTX Therapeutics, serving as a consultant for Horizon Pharma, and having equity in Colorado Research Partners LLC. Dr. Terkeltaub reported receiving a research grant from AstraZeneca in the field of hyperuricemia and consultancies with AstraZeneca, Horizon, Sobi, Selecta Biosciences.
Is gouty nephropathy real? It’s a question that has been posed often in rheumatology over the last several decades.
A new study found 36% of patients with untreated gout at a medical center in Vietnam have diffuse hyperechoic renal medulla as seen on ultrasound, which could indicate the presence of microcrystalline nephropathy. However, the results, published in Kidney International, may raise more questions than answers about the existence of gouty nephropathy and its relation to chronic kidney disease (CKD).
In their study, Thomas Bardin, MD, of the department of rheumatology at Lariboisière Hospital in Paris and colleagues evaluated 502 consecutive patients from Vien Gut Medical Center in Ho Chi Minh City, Vietnam, using B-mode renal ultrasound. The patients were mostly men with a median age of 46 years, body mass index of 25 kg/m2, estimated disease duration of 4 years, and uricemia of 423.2 micromol/L (7.11 mg/dL). Patients had a median estimated glomerular filtration rate (eGFR) of 78 mL/min per 1.73 m2. There was a history of hypertension in 112 patients (22.3%), type 2 diabetes in 58 patients (11.5%), renal lithiasis in 28 patients (5.6%), and coronary heart disease in 5 patients (1%).
While 39% of patients had previously used allopurinol for “a generally short period,” patients were not on urate-lowering therapy at the time of the study. Clinical tophi were present in 279 patients (55.6%), urate arthropathies in 154 patients (30.7%), and 43 patients (10.4%) used steroids daily.
B-mode renal ultrasound showed 181 patients (36%; 95% confidence interval, 32%-40%) had “hyperechoic pattern of Malpighi pyramids compared with the adjacent cortex,” which was “associated with twinkling artifacts” visible on color Doppler ultrasound. There was a significant association between renal medulla hyperechogenicity and patient age, disease duration, use of steroids, clinical tophi, and urate arthropathy (P less than .0001 for all). A significant association was also seen between renal medulla hyperechogenicity and decreased eGFR (P < .0001), proteinuria (P = .0006), leukocyturia (P = .0008), hypertension (P = .0008), hyperuricemia (P = .002), and coronary heart disease (P = .006).
In a multivariate analysis, there was a significant association between renal medulla hyperechogenicity and clinical tophi (odds ratio, 7.27; 95% CI, 3.68–15.19; P < .0001), urate arthropathy (OR, 3.46; 95% CI, 1.99–6.09; P < .0001), estimated gout duration (OR, 2.13; 95% CI, 1.55–2.96; P < .0001), double contour thickness (OR, 1.45; 95% CI, 1.06–1.97; P < .02), and eGFR (OR, 0.30; 95% CI, 0.09–0.89; P < .034).
“The finding was observed mainly in tophaceous gout, which involved a large proportion of our patients who had received very little treatment with urate-lowering drugs and was associated with moderately impaired renal function and urinary features compatible with tubulointerstitial nephritis,” Dr. Bardin and colleagues wrote in the study. The researchers also found “similar features” in 4 of 10 French patients at the Paris Necker Hospital in Paris, and noted that similar findings have been reported in Japan and Korea, which they said may mean hyperechoic medulla “is not unique to Vietnamese patients.”
Relation to CKD still unclear
In a related editorial, Federica Piani, MD, and Richard J. Johnson, MD, of the division of renal diseases and hypertension at the University of Colorado at Denver, Aurora, explained that gout was considered by some clinicians to be a cause of CKD in a time before urate-lowering therapies, because as many as 25% of patients with gout went on to experience kidney failure and about half experienced lower kidney function.
The association between gout and CKD was thought to be attributable to “frequent deposition of urate crystals in the tubular lumens and interstitium in the outer medulla of these patients,” but the concept was later challenged because “the crystals were generally found focally and did not readily explain the kidney damage.”
But even as interest in rheumatology moved away from the concept of gouty nephropathy to how serum uric acid impacts CKD, “the possibility that urate crystal deposition in the kidney could also be contributing to the kidney injury was never ruled out,” according to Dr. Piani and Dr. Johnson.
Kidney biopsies can sometimes miss urate crystals because the crystals dissolve if alcohol fixation is not used and because the biopsy site is often in the renal cortex, the authors noted. Recent research has identified that dual-energy CT scans can distinguish between calcium deposits and urate crystals better than ultrasound, and previous research from Thomas Bardin, MD, and colleagues in two patients noted a correlation between dual-energy CT scan findings of urate crystals and hyperechoic medulla findings on renal ultrasound.
The results by Dr. Bardin and associates, they said, “have reawakened the entity of urate microcrystalline nephropathy as a possible cause of CKD.”
Robert Terkeltaub, MD, professor of medicine at the University of California, San Diego, and section chief of Rheumatology at the San Diego VA Medical Center, said in an interview that he also believes the findings by Dr. Bardin and associates are real. He cited a study by Isabelle Ayoub, MD, and colleagues in Clinical Nephrology from 2016 that evaluated kidney biopsies in Germany and found medullary tophi were more likely to be present in patients with CKD than without.
“Chronic gouty nephropathy did not disappear. It still exists,” said Dr. Terkeltaub, who was not involved in the study by Dr. Bardin and colleagues.
The prospect that, if “you look hard enough, you’re going to see urate crystals and a pattern that’s attributed in the renal medulla” in patients with untreated gout is “very provocative, and interesting, and clinically relevant, and merits more investigation,” noted Dr. Terkeltaub, who is also president of the Gout, Hyperuricemia and Crystal-Associated Disease Network.
If verified, the results have important implications for patients with gout and its relationship to CKD, Dr. Terkeltaub said, but they raise “more questions than answers.
“I think it’s a really good wake-up call to start looking, doing good detective work here, and looking especially in people who have gout as opposed to just people with chronic kidney disease,” he said.
The authors reported no relevant conflicts of interest. Dr. Johnson, who coauthored an accompanying editorial, reported having equity in XORTX Therapeutics, serving as a consultant for Horizon Pharma, and having equity in Colorado Research Partners LLC. Dr. Terkeltaub reported receiving a research grant from AstraZeneca in the field of hyperuricemia and consultancies with AstraZeneca, Horizon, Sobi, Selecta Biosciences.
FROM KIDNEY INTERNATIONAL