Renal artery calcification
Citation, DOI & article data
Renal artery calcifications, also known as renovascular calcifications, are deposits of calcium salts on the wall of a renal artery, found incidentally on imaging, usually CT 1. They are associated with extrarenal atherosclerosis and linked to hypertension 2.
The term “renal artery calcification” refers to mineral depositions detected on/in the walls of the renal arteries (or their branches), considered when their density ≥130 Hounsfield units on CT 3. It is believed that they are representative of atherosclerotic plaques 4, defined as regions with the relevant density whose area is ≥1 mm 2,5.
Renovascular calcification is used synonymously with renal artery calcification. Although calcifications of the renal veins have been described they are very rare and usually represent the calcification of renal vein thrombus 51.
Renal artery calcifications are a common finding on CT 4.
- white race 2
- male gender 6
- aortic calcifications (when absent, renal artery calcifications are virtually non-existent) 4
- increased perirenal fat thickness 7
- leptin deficiency (in ob/ob mice), especially when high doses of vitamin D3 are administered 8
- diabetes mellitus 8
- osteoprotegerin (OPG) deficiency (in mice) or defects in OPG, its signaling pathway or ligand 9
- osteoporosis 9
- miR-125b expression 10
- hypertension (independent of cardiovascular disease risk factors, ascending aorta calcifications, kidney function, gender, and race) 2, 1.6 times more likely in patients with renal artery calcification 6
- calcification of the coronaries, carotids, thoracoabdominal aorta, iliac arteries, aortic and mitral annuli 11
- older age 12
- diastolic blood pressure 12
- body mass index (BMI) 12
- intima-media thickness (IMT) of the carotids 12
Renal artery calcification can cause renal and systemic (extrarenal) impacts. Its presence can trigger mechanisms that result in localized vasoconstriction and consequently cellular increase of the magnitude of the renin-angiotensin-aldosterone system response, which further elevates blood pressure 25. Although arterial wall calcium may or may not obstruct blood flow, it potentially signals renal atherosclerotic and small vessel disease, which in turn can affect renal blood pressure regulation, and alongside water and salt retention ultimately lead to hypertension 2. In a study, the presence of renal artery calcifications, as opposed to those of extrarenal origin, were found to be the most accurate differentiator between hypertensive and non-hypertensive patients during CT scans 6.
It is known that arterial calcifications are strongly associated with atherosclerosis, which is responsible for 90% of renal artery narrowing 26. Diffuse calcifications correlate with higher grades of renal arterial stenosis on CT angiography, especially when located bilaterally, which is strongly linked to hypertension 4.
Clinically, high-grade renal artery calcifications are significantly associated with end-stage renal disease, either as the immediate causing factor or as an inducer of intrarenal calcification or downstream ischemia, that ultimately result in end-stage renal disease 4.
One of the risk factors for renal artery calcifications is perirenal fat of increased thickness. This can be effectively assessed using CT scans, which allow unreduced measurements and trustworthy predictions of volume, as opposed to the more convenient and conventionally deployed ultrasonography. Perirenal adipose tissue actively secretes adipokines and cytokines, that trigger inflammatory processes that predispose to atherosclerosis 7.
Renal artery calcifications are also a potent non-invasive marker of subclinical atherosclerosis in insulin-independent diabetic patients 12, in which subsequent renal dysfunction is responsible for elevated morbidity and mortality 8.
Conventional calcifications, of renal or extrarenal location, are generally a result of the conversion of vascular smooth muscle cells to osteoblasts, due to retention of phosphate, hypercalcemia, previous dialysis treatment, active vitamin D administration or calcification inhibitor deficiency among other causal factors 15.
Calcifications may be present at the intima, the media or both layers of the renal arteries 16-18. Clinically distinguishing between the two laminal locations can be significantly difficult (or even impossible), as this can only be achieved through histological investigation 18,19.
Since they do not supply the heart or the brain, renal arteries are considered a part of the peripheral vascular system 20. To assess the degree and/or the severity of the calcification, the peripheral arterial calcium scoring system (PACSS) can be used 21. This system scores arterial calcifications of the intima and media layers taking into consideration their unilateral or bilateral location and length in 5 grades, using HI-fluoroscopy and DSA in AP projection, as follows:
- grade 0: no visible calcifications at the referred region
- grade 1: unilateral calcification less than 5 cm in maximum diameter
- grade 2: unilateral calcification equal to, or greater than, 5 cm in maximum diameter
- grade 3: bilateral calcification less than 5 cm in maximum diameter
- grade 4: bilateral calcification equal to, or greater than, 5 cm in maximum diameter
Alternatively, the Agatston system can be used for classification, whose score is calculated by multiplying the area of the calcification by its highest HU value 5,22-24.
Calcified renal arteries are firm, dense, and tubular, with solid white plaques 27.
Microscopically, as renal arteries are of muscular type, their internal elastic lamina and medial musculature are surrounded by a band of total calcification 27.
When atherosclerotic plaques become of type V, calcium becomes their main component, rendering them almost completely calcified 28.
On the other hand, when mixed type plaques are present, diffuse renal artery calcifications are more common, which are strongly associated with higher-grade stenosis 4.
It is crucial to highlight that there are no specific immunohistochemical/immunohistological markers for the detection of microscopic calcification. However, several markers can be helpful, especially when connected to the etiological factor.
In diabetic patients, calcification sites upregulate the expression of ALP, Runx2 and annexin II, while downregulating annexin V. Alizarin red stain was found to be able to reveal calcium deposition in resected aortic valves of patients with diabetes mellitus 29.
The expression of S100A/calgranulin, and especially S100A9 is induced in patients with ectopic cardiac calcification of pre-existing cardiovascular disease 30, but is more diffusely associated with atherosclerosis in general 32.
In cases of increased osteoblast activity and/or transformation of vascular smooth muscles cells to osteoblasts, markers such as osteoprotegerin, osteopontin, osteocalcin, MGP and bone matrix protein (BMP) are expected to be overexpressed 31. The more atherosclerotic plaques progress to type V and of fibrocalcific type, the more markers like BMP2 and transcription factors such as Cbfa1 and osterix are expressed 33.
As one of the main causes of renal artery calcification is a disequilibrium in mineral-bone metabolism, the levels of certain serological markers are expected to be disturbed in affected patients. More notably, serum osteoprotegerin, bone-specific alkaline phosphatase (BAP), intact PTH, phosphorus and osteocalcin levels are usually elevated, while 25[OH]D3, 1,25[OH]2D3 and fetuin A levels are usually reduced 34.
The presence of the Asp allele regarding the eNOS Glu298Asp polymorphism was found to predispose to calcified renal arterial atherosclerotic plaque formation 35, alongside the ACE1-D allele (deletion polymorphism) 36.
Virtually, the only way to confirm the presence of arterial calcification is through radiological imaging modalities. X-rays, ultrasonography and non-contrast CT may be used to detect macrocalcifications, whilst 18F-NaF PET scans are able to assess microcalcifications and angiography aids to visualize vascular stenosis 39. MRI is of limited value in the detection of calcifications, as they are proton-poor and diamagnetic, thus inconspicuous on conventional sequences 13,14.
Vascular calcifications appear on x-rays as radiopaque areas of bone-like attenuation, following the course of the affected vessels 40. When not extensive enough, they can be difficult to detect on x-rays, and appropriate magnification may be needed for their visualization.
Ultrasonography is one of the best modalities for the detection and characterization of calcifications on the walls of the renal arteries, mainly due to the convenience of their anatomical location in the abdomen.
The main ultrasonographic appearance of vascular calcification is that of hyperechoic foci accompanied by acoustic shadowing 41. Its pattern of sound reflection allows an echogenicity seven times greater than that of the normal vessel wall and three times greater than uncalcified (lipid-rich, hemorrhagic or fibrotic) atherosclerotic plaques 42.
It is important to note that small renal calculi (≤1 cm maximal diameter) can be almost impossible to differentiate from renal artery calcification (this does not apply to calculi larger than 2 cm, as their curvilinear shape allows confident distinction) when calcium is deposited proximally to the renal sinus. In these cases, an abdominal x-ray should be performed to avail in terms of differential diagnosis 41.
CT is the modality of choice for the detection of renal artery calcification 28,37, serving as a non-invasive, straightforward, fast, and reliable quantifying technique 43.
Calcium appears white on non-contrast CT images due to its high Hounsfield value 38, diagnostically accepted when equal to, or greater than, 130 HU. These hyperdense lesions are typically found on the arterial walls in any plane, and the combination of coronal, axial and sagittal views offers an excellent 3D anatomical topographic localization.
Angiographic techniques are unable to depict macrocalcification, microcalcification or atherosclerotic plaques. They employ the excellent vascular imaging potential of contrast media to visualize arteries and all their branches, to assess any possible narrowing. It is known that calcifications are a causal factor of arterial stenosis, hence acting as a surrogate marker for the presence of vascular calcium deposition 44.
PET using 18F-NaF, a detector of cellular mechanisms related to bone formation 45,46, is significantly helpful for the assessment of microcalcification, since the pathophysiological mechanism of vascular calcifications connects the procedure to osteoblast-related mechanisms. Despite its low spatial resolution, PET has excellent sensitivity for calcifications.
Contrary to conventional CT, 18F-NaF PET can detect early active calcium deposition on arterial walls in the form of microcalcifications, due to significantly higher resolution 47-49.
When in doubt, alizarin red stain can be used to verify 18F-NaF in sites suspicious for microscopic calcification 50.
- 1. Siegel CL, Ellis JH, Korobkin M, Dunnick NR. CT-detected renal arterial calcification: correlation with renal artery stenosis on angiography. (1994) AJR. American journal of roentgenology. 163 (4): 867-72. doi:10.2214/ajr.163.4.8092026 - Pubmed
- 2. Thomas IC, Ratigan AR, Rifkin DE, Ix JH, Criqui MH, Budoff MJ, Allison MA. The association of renal artery calcification with hypertension in community-living individuals: the multiethnic study of atherosclerosis. (2016) Journal of the American Society of Hypertension : JASH. 10 (2): 167-74. doi:10.1016/j.jash.2015.12.003 - Pubmed
- 3. Rennenberg RJ, Schurgers LJ, Kroon AA, Stehouwer CD. Arterial calcifications. (2010) Journal of cellular and molecular medicine. 14 (9): 2203-10. doi:10.1111/j.1582-4934.2010.01139.x - Pubmed
- 4. Tolkin, Lior, Bursztyn, Michael, Ben-Dov, Iddo Z., Simanovsky, Natalia, Hiller, Nurith. Incidental renal artery calcifications: a study of 350 consecutive abdominal computed tomography scans. (2009) Nephrology Dialysis Transplantation. 24 (7): 2170. doi:10.1093/ndt/gfp051
- 5. Chiu YW, Adler S, Budoff M, Takasu J, Ashai J, Mehrotra R. Prevalence and prognostic significance of renal artery calcification in patients with diabetes and proteinuria. (2010) Clinical journal of the American Society of Nephrology : CJASN. 5 (11): 2093-100. doi:10.2215/CJN.03730410 - Pubmed
- 6. Allison MA, Lillie EO, DiTomasso D, Wright CM, Criqui MH. Renal artery calcium is independently associated with hypertension. (2007) Journal of the American College of Cardiology. 50 (16): 1578-83. doi:10.1016/j.jacc.2007.07.015 - Pubmed
- 7. Koo BK, Denenberg JO, Wright CM, Criqui MH, Allison MA. Associations of Perirenal Fat Thickness with Renal and Systemic Calcified Atherosclerosis. (2020) Endocrinology and metabolism (Seoul, Korea). 35 (1): 122-131. doi:10.3803/EnM.2020.35.1.122 - Pubmed
- 8. Almeida YE, Fessel MR, do Carmo LS, Jorgetti V, Farias-Silva E, Pescatore LA, Gamarra LF, Andrade MC, Simplicio-Filho A, Mangueira CLP, Rangel ÉB, Liberman M. Excessive cholecalciferol supplementation increases kidney dysfunction associated with intrarenal artery calcification in obese insulin-resistant mice. (2020) Scientific reports. 10 (1): 87. doi:10.1038/s41598-019-55501-3 - Pubmed
- 9. Bucay N, Sarosi I, Dunstan CR, Morony S, Tarpley J, Capparelli C, Scully S, Tan HL, Xu W, Lacey DL, Boyle WJ, Simonet WS. osteoprotegerin-deficient mice develop early onset osteoporosis and arterial calcification. (1998) Genes & development. 12 (9): 1260-8. doi:10.1101/gad.12.9.1260 - Pubmed
- 10. Chao CT, Han DS, Huang JW. Circulating microRNA-125b Levels Are Associated With the Risk of Vascular Calcification in Healthy Community-Dwelling Older Adults. (2021) Frontiers in cardiovascular medicine. 8: 624313. doi:10.3389/fcvm.2021.624313 - Pubmed
- 11. Allison MA, DiTomasso D, Criqui MH, Langer RD, Wright CM. Renal artery calcium: relationship to systemic calcified atherosclerosis. (2006) Vascular medicine (London, England). 11 (4): 232-8. doi:10.1177/1358863x06073449 - Pubmed
- 12. Freedman BI, Hsu FC, Langefeld CD, Bowden DW, Moossavi S, Dryman BN, Carr JJ. Renal artery calcified plaque associations with subclinical renal and cardiovascular disease. (2004) Kidney international. 65 (6): 2262-7. doi:10.1111/j.1523-1755.2004.00645.x - Pubmed
- 13. Wu Z, Mittal S, Kish K, Yu Y, Hu J, Haacke EM. Identification of calcification with MRI using susceptibility-weighted imaging: a case study. (2009) Journal of magnetic resonance imaging : JMRI. 29 (1): 177-82. doi:10.1002/jmri.21617 - Pubmed
- 14. Chen W, Zhu W, Kovanlikaya I, Kovanlikaya A, Liu T, Wang S, Salustri C, Wang Y. Intracranial calcifications and hemorrhages: characterization with quantitative susceptibility mapping. (2014) Radiology. 270 (2): 496-505. doi:10.1148/radiol.13122640 - Pubmed
- 15. Disthabanchong S. Vascular calcification in chronic kidney disease: Pathogenesis and clinical implication. (2012) World journal of nephrology. 1 (2): 43-53. doi:10.5527/wjn.v1.i2.43 - Pubmed
- 16. Koleganova N, Piecha G, Ritz E, Schirmacher P, Müller A, Meyer HP, Gross ML. Arterial calcification in patients with chronic kidney disease. (2009) Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association. 24 (8): 2488-96. doi:10.1093/ndt/gfp137 - Pubmed
- 17. Usman A, Ribatti D, Sadat U, Gillard JH. From Lipid Retention to Immune-Mediate Inflammation and Associated Angiogenesis in the Pathogenesis of Atherosclerosis. (2015) Journal of atherosclerosis and thrombosis. 22 (8): 739-49. doi:10.5551/jat.30460 - Pubmed
- 18. Amann K. Media calcification and intima calcification are distinct entities in chronic kidney disease. (2008) Clinical journal of the American Society of Nephrology : CJASN. 3 (6): 1599-605. doi:10.2215/CJN.02120508 - Pubmed
- 19. Drüeke TB. Arterial intima and media calcification: distinct entities with different pathogenesis or all the same?. (2008) Clinical journal of the American Society of Nephrology : CJASN. 3 (6): 1583-4. doi:10.2215/CJN.03250708 - Pubmed
- 20. Morcos R, Louka B, Tseng A, Misra S, McBane R, Esser H, Shamoun F. The Evolving Treatment of Peripheral Arterial Disease through Guideline-Directed Recommendations. (2018) Journal of clinical medicine. doi:10.3390/jcm7010009 - Pubmed
- 21. Rocha-Singh KJ, Zeller T, Jaff MR. Peripheral arterial calcification: prevalence, mechanism, detection, and clinical implications. (2014) Catheterization and cardiovascular interventions : official journal of the Society for Cardiac Angiography & Interventions. 83 (6): E212-20. doi:10.1002/ccd.25387 - Pubmed
- 22. Neves PO, Andrade J, Monção H. Coronary artery calcium score: current status. (2017) Radiologia brasileira. 50 (3): 182-189. doi:10.1590/0100-3984.2015.0235 - Pubmed
- 23. González G, Washko GR, Estépar RS. AUTOMATED AGATSTON SCORE COMPUTATION IN A LARGE DATASET OF NON ECG-GATED CHEST COMPUTED TOMOGRAPHY. (2016) Proceedings. IEEE International Symposium on Biomedical Imaging. 2016: 53-57. doi:10.1109/ISBI.2016.7493209 - Pubmed
- 24. Vashishtha D, McClelland RL, Ix JH, Rifkin DE, Jenny N, Allison M. Relation Between Calcified Atherosclerosis in the Renal Arteries and Kidney Function (from the Multi-Ethnic Study of Atherosclerosis). (2017) The American journal of cardiology. 120 (8): 1434-1439. doi:10.1016/j.amjcard.2017.07.020 - Pubmed
- 25. Oparil S, Oparil ZM, Oparil CD, Oparil. Pathogenesis of hypertension. (2003) Annals of internal medicine. doi:10.7326/0003-4819-139-9-200311040-00011 - Pubmed
- 26. Lao D, Parasher PS, Cho KC, Yeghiazarians Y. Atherosclerotic renal artery stenosis--diagnosis and treatment. (2011) Mayo Clinic proceedings. 86 (7): 649-57. doi:10.4065/mcp.2011.0181 - Pubmed
- 27. Wanda M. Haschek, Colin G. Rousseaux, Matthew A. Wallig. Haschek and Rousseaux's Handbook of Toxicologic Pathology. (2013) ISBN: 9780124157590
- 28. Stary HC. The development of calcium deposits in atherosclerotic lesions and their persistence after lipid regression. (2001) The American journal of cardiology. 88 (2A): 16E-19E. doi:10.1016/s0002-9149(01)01713-1 - Pubmed
- 29. Mosch J, Gleissner CA, Body S, Aikawa E. Histopathological assessment of calcification and inflammation of calcific aortic valves from patients with and without diabetes mellitus. (2017) Histology and histopathology. 32 (3): 293-306. doi:10.14670/HH-11-797 - Pubmed
- 30. Yan L, Bowman MA. Chronic sustained inflammation links to left ventricular hypertrophy and aortic valve sclerosis: a new link between S100/RAGE and FGF23. (2014) Inflammation and cell signaling. doi:10.14800/ics.279 - Pubmed
- 31. Pal SN, Golledge J. Osteo-progenitors in vascular calcification: a circulating cell theory. (2011) Journal of atherosclerosis and thrombosis. 18 (7): 551-9. doi:10.5551/jat.8656 - Pubmed
- 32. Xiao X, Yang C, Qu SL, Shao YD, Zhou CY, Chao R, Huang L, Zhang C. S100 proteins in atherosclerosis. (2020) Clinica chimica acta; international journal of clinical chemistry. 502: 293-304. doi:10.1016/j.cca.2019.11.019 - Pubmed
- 33. Rebecca C. Johnson, Jane A. Leopold, Joseph Loscalzo. Vascular Calcification. (2006) Circulation Research. doi:10.1161/01.RES.0000249379.55535.21
- 34. Osorio A, Ortega E, Torres JM, Sanchez P, Ruiz-Requena E. Biochemical markers of vascular calcification in elderly hemodialysis patients. (2013) Molecular and cellular biochemistry. 374 (1-2): 21-7. doi:10.1007/s11010-012-1500-y - Pubmed
- 35. van Onna M, Kroon AA, Houben AJ, Koster D, Zeegers MP, Henskens LH, Plat AW, Stoffers HE, de Leeuw PW. Genetic risk of atherosclerotic renal artery disease: the candidate gene approach in a renal angiography cohort. (2004) Hypertension (Dallas, Tex. : 1979). 44 (4): 448-53. doi:10.1161/01.HYP.0000141440.02210.da - Pubmed
- 36. Missouris CG, Barley J, Jeffery S, Carter ND, Singer DR, MacGregor GA. Genetic risk for renal artery stenosis: association with deletion polymorphism in angiotensin 1-converting enzyme gene. (1996) Kidney international. 49 (2): 534-7. doi:10.1038/ki.1996.76 - Pubmed
- 37. Agatston AS, Janowitz WR, Hildner FJ, Zusmer NR, Viamonte M, Detrano R. Quantification of coronary artery calcium using ultrafast computed tomography. (1990) Journal of the American College of Cardiology. 15 (4): 827-32. doi:10.1016/0735-1097(90)90282-t - Pubmed
- 38. Ichii M, Ishimura E, Shima H, Ohno Y, Ochi A, Nakatani S, Tsuda A, Ehara S, Mori K, Fukumoto S, Naganuma T, Takemoto Y, Nakatani T, Inaba M. Quantitative analysis of abdominal aortic calcification in CKD patients without dialysis therapy by use of the Agatston score. (2013) Kidney & blood pressure research. 38 (2-3): 196-204. doi:10.1159/000355768 - Pubmed
- 39. Wang Y, Osborne MT, Tung B, Li M, Li Y. Imaging Cardiovascular Calcification. (2018) Journal of the American Heart Association. doi:10.1161/JAHA.118.008564 - Pubmed
- 40. BOHATIRCHUK F. USE OF X-RAYS IN THE DETECTION OF CALCIUM IN BIOLOGICAL TISSUES AT MICROLEVEL. (1963) Canadian Medical Association journal. 89: 1171-7. Pubmed
- 41. Kane RA, Manco LG. Renal arterial calcification simulating nephrolithiasis on sonography. (1983) AJR. American journal of roentgenology. 140 (1): 101-4. doi:10.2214/ajr.140.1.101 - Pubmed
- 42. Picano E, Landini L, Distante A, Benassi A, Sarnelli R, L'Abbate A. Fibrosis, lipids, and calcium in human atherosclerotic plaque. In vitro differentiation from normal aortic walls by ultrasonic attenuation. (1985) Circulation research. 56 (4): 556-62. doi:10.1161/01.res.56.4.556 - Pubmed
- 43. Becker CR, Knez A, Ohnesorge B, Schoepf UJ, Flohr T, Bruening R, Haberl R, Reiser MF. Visualization and quantification of coronary calcifications with electron beam and spiral computed tomography. (2000) European radiology. 10 (4): 629-35. doi:10.1007/s003300050975 - Pubmed
- 44. Summaries for patients. Diagnosis of renal artery stenosis. (2004) Annals of internal medicine. 141 (9): I66. doi:10.7326/0003-4819-141-9-200411020-00003 - Pubmed
- 45. Even-Sapir E, Metser U, Mishani E, Lievshitz G, Lerman H, Leibovitch I. The detection of bone metastases in patients with high-risk prostate cancer: 99mTc-MDP Planar bone scintigraphy, single- and multi-field-of-view SPECT, 18F-fluoride PET, and 18F-fluoride PET/CT. (2006) Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 47 (2): 287-97. Pubmed
- 46. BLAU M, NAGLER W, BENDER MA. Fluorine-18: a new isotope for bone scanning. (1962) Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 3: 332-4. Pubmed
- 47. Joshi NV, Vesey AT, Williams MC, Shah AS, Calvert PA, Craighead FH, Yeoh SE, Wallace W, Salter D, Fletcher AM, van Beek EJ, Flapan AD, Uren NG, Behan MW, Cruden NL, Mills NL, Fox KA, Rudd JH, Dweck MR, Newby DE. 18F-fluoride positron emission tomography for identification of ruptured and high-risk coronary atherosclerotic plaques: a prospective clinical trial. (2014) Lancet (London, England). 383 (9918): 705-13. doi:10.1016/S0140-6736(13)61754-7 - Pubmed
- 48. Doherty TM, Fitzpatrick LA, Inoue D, Qiao JH, Fishbein MC, Detrano RC, Shah PK, Rajavashisth TB. Molecular, endocrine, and genetic mechanisms of arterial calcification. (2004) Endocrine reviews. 25 (4): 629-72. doi:10.1210/er.2003-0015 - Pubmed
- 49. Dweck MR, Jenkins WS, Vesey AT, Pringle MA, Chin CW, Malley TS, Cowie WJ, Tsampasian V, Richardson H, Fletcher A, Wallace WA, Pessotto R, van Beek EJ, Boon NA, Rudd JH, Newby DE. 18F-sodium fluoride uptake is a marker of active calcification and disease progression in patients with aortic stenosis. (2014) Circulation. Cardiovascular imaging. 7 (2): 371-8. doi:10.1161/CIRCIMAGING.113.001508 - Pubmed
- 50. Irkle A, Vesey AT, Lewis DY, Skepper JN, Bird JL, Dweck MR, Joshi FR, Gallagher FA, Warburton EA, Bennett MR, Brindle KM, Newby DE, Rudd JH, Davenport AP. Identifying active vascular microcalcification by (18)F-sodium fluoride positron emission tomography. (2015) Nature communications. 6: 7495. doi:10.1038/ncomms8495 - Pubmed
- 51. Wang Y, Chen S, Wang W, Liu J, Jin B. Renal vein thrombosis mimicking urinary calculus: a dilemma of diagnosis. (2015) BMC urology. 15: 61. doi:10.1186/s12894-015-0054-1 - Pubmed