Medicine:Renal artery stenosis

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Renal artery stenosis
Kidney PioM.png
  • 1. Renal pyramid
  • 2. Interlobular artery
  • 3. Renal artery
  • 4. Renal vein
  • 5. Renal hilum
  • 6. Renal pelvis
  • 7. Ureter
  • 8. Minor calyx
  • 9. Renal capsule
  • 10. Inferior renal capsule
  • 11. Superior renal capsule
  • 12. Interlobar vein
  • 13. Nephron
  • 14. Renal sinus
  • 15. Major calyx
  • 16. Renal papilla
  • 17. Renal column
SpecialtyNephrology
Risk factorsSmoking, High blood pressure[1]
Diagnostic methodCaptopril challenge test, Doppler ultrasound[2][3]
TreatmentACE inhibitors[1]

Renal artery stenosis (RAS) is the narrowing of one or both of the renal arteries, most often caused by atherosclerosis or fibromuscular dysplasia. This narrowing of the renal artery can impede blood flow to the target kidney, resulting in renovascular hypertension – a secondary type of high blood pressure. Possible complications of renal artery stenosis are chronic kidney disease and coronary artery disease.[1]

Signs and symptoms

Most cases of renal artery stenosis are asymptomatic, and the main problem is high blood pressure that cannot be controlled with medication.[4] Decreased kidney function may develop if both kidneys do not receive adequate blood flow, furthermore some people with renal artery stenosis present with episodes of flash pulmonary edema.[5]

Cause

Renal artery stenosis is most often caused by atherosclerosis which causes the renal arteries to harden and narrow due to the build-up of plaque. This is known as atherosclerotic renovascular disease, which accounts for about 90% of cases.[6] This narrowing of renal arteries due to plaque build-up leads to higher blood pressure within the artery and decreased blood flow to the kidney. This decreased blood flow leads to decreased blood pressure in the kidney, which leads to the activation of the Renin-Angiotensin-Aldosterone (RAA) system. Juxtaglomerular cells secrete renin, which converts angiotensinogen to angiotensin I, which is then converted to angiotensin II by angiotensin converting enzyme (ACE). Angiotensin II then acts on the adrenal cortex to increase secretion of the hormone aldosterone. Aldosterone causes sodium and water retention, leading to an increase in blood volume and blood pressure. Therefore, people with RAS have chronic high blood pressure because their RAA system is hyperactivated.[7]

Pathophysiology

The pathophysiology of renal artery stenosis leads to changes in the structure of the kidney that are most noticeable in the tubular tissue.[8] If the stenosis is longstanding and severe, the glomerular filtration rate in the affected kidneys never recovers and (prerenal) kidney failure is the result.

Changes include:[8]

  • Fibrosis
  • Tubular cell size (decrease)
  • Thickening of Bowman capsule
  • Tubulosclerosis
  • Glomerular capillary tuft (atrophy)

Diagnosis

File:Assessment-of-the-kidneys-magnetic-resonance-angiography-perfusion-and-diffusion-1532-429X-13-70-S2.ogv The diagnosis of renal artery stenosis can use many techniques to determine if the condition is present, a clinical prediction rule is available to guide diagnosis.[9]

Among the diagnostic techniques are:

The specific criteria for renal artery stenosis on Doppler are an acceleration time of greater than 70 milliseconds, an acceleration index of less than 300 cm/sec² and a velocity ratio of the renal artery to aorta of greater than 3.5.[2]

Treatment

A diuretic (Hydrochlorothiazide)

Atherosclerotic renal artery stenosis

It is initially treated with medications, including diuretics, and medications for blood pressure control.[8] When high-grade renal artery stenosis is documented and blood pressure cannot be controlled with medication, or if renal function deteriorates, surgery may be resorted to. The most commonly used procedure is a minimally-invasive angioplasty with or without stenting. It is unclear if this approach yields better results than the use of medications alone.[15] It is a relatively safe procedure.[15] If all else fails and the kidney is thought to be worsening hypertension and revascularization with angioplasty or surgery does not work, then surgical removal of the affected kidney (nephrectomy) may significantly improve high blood pressure.[16]

Fibromuscular dysplasia

Angioplasty alone is preferred in fibromuscular dysplasia, with stenting reserved for unsuccessful angioplasty or complications such as dissection.[17]

See also

  • Renovascular hypertension

References

  1. ↑ 1.0 1.1 1.2 "Renal Artery Stenosis". http://www.niddk.nih.gov/health-information/health-topics/kidney-disease/renal-artery-stenosis-ras/Pages/facts.aspx. 
  2. ↑ 2.0 2.1 2.2 Granata, A.; Fiorini, F.; Andrulli, S.; Logias, F.; Gallieni, M.; Romano, G.; Sicurezza, E.; Fiore, C.E. (December 2009). "Doppler ultrasound and renal artery stenosis: An overview". Journal of Ultrasound 12 (4): 133–143. doi:10.1016/j.jus.2009.09.006. PMID 23397022. 
  3. ↑ 3.0 3.1 Ong, Yong Yau (2005-01-01). A Clinical Approach to Medicine. World Scientific. ISBN 9789812560735. https://books.google.com/books?id=t0KmTrzxAlEC&q=captopril%2520challenge%2520test%2520%2520renal%2520artery%2520stenosis&pg=PA1243. 
  4. ↑ MedlinePlus Encyclopedia Renovascular hypertension
  5. ↑ Messerli, F. H.; Bangalore, S.; Makani, H.; Rimoldi, S. F.; Allemann, Y.; White, C. J.; Textor, S.; Sleight, P. (2 September 2011). "Flash pulmonary oedema and bilateral renal artery stenosis: the Pickering Syndrome". European Heart Journal 32 (18): 2231–2235. doi:10.1093/eurheartj/ehr056. PMID 21406441. 
  6. ↑ Vassallo, Diana; Kalra, Philip A. (2017). "Atherosclerotic renovascular disease – epidemiology, treatment and current challenges". Advances in Interventional Cardiology 3 (3): 191–201. doi:10.5114/aic.2017.70186. PMID 29056991. 
  7. ↑ Safian, Robert D. (March 2021). "Renal artery stenosis". Progress in Cardiovascular Diseases 65: 60–70. doi:10.1016/j.pcad.2021.03.003. PMID 33745915. 
  8. ↑ 8.0 8.1 8.2 Renal Artery Stenosis at eMedicine
  9. ↑ Steyerberg, Ewout (2008-12-16). Clinical Prediction Models: A Practical Approach to Development, Validation, and Updating. Springer Science & Business Media. ISBN 9780387772448. https://books.google.com/books?id=kHGK58cLsMIC&q=clinical%2520prediction%2520rule%2520is%2520used%2520in%2520renal%2520artery%2520stenosis&pg=PA12. 
  10. ↑ Protasiewicz, Marcin; Kądziela, Jacek; Początek, Karol; Poręba, Rafał; Podgórski, Maciej; Derkacz, Arkadiusz; Prejbisz, Aleksander; Mysiak, Andrzej et al. (November 2013). "Renal Artery Stenosis in Patients With Resistant Hypertension". The American Journal of Cardiology 112 (9): 1417–1420. doi:10.1016/j.amjcard.2013.06.030. PMID 24135303. 
  11. ↑ Talley, Nicholas Joseph; O'Connor, Simon (2013-09-20). Clinical Examination: A Systematic Guide to Physical Diagnosis. Elsevier Health Sciences. ISBN 9780729541473. https://books.google.com/books?id=cTFkBgAAQBAJ&q=costal%2520margin%2520auscultation%2520renal%2520artery%2520stenosis&pg=PA208. 
  12. ↑ Taylor, Andrew T. (May 2014). "Radionuclides in Nephrourology, Part 2: Pitfalls and Diagnostic Applications". Journal of Nuclear Medicine 55 (5): 786–798. doi:10.2967/jnumed.113.133454. PMID 24591488. 
  13. ↑ Sam, Amir H.; James T.H. Teo (2010). Rapid Medicine. Wiley-Blackwell. ISBN 978-1405183239. 
  14. ↑ Attenberger, Ulrike I; Morelli, John N; Schoenberg, Stefan O; Michaely, Henrik J (December 2011). "Assessment of the kidneys: magnetic resonance angiography, perfusion and diffusion". Journal of Cardiovascular Magnetic Resonance 13 (1): 70. doi:10.1186/1532-429X-13-70. PMID 22085467. 
  15. ↑ 15.0 15.1 Jenks, Sara; Yeoh, Su Ern; Conway, Bryan R (5 December 2014). "Balloon angioplasty, with and without stenting, versus medical therapy for hypertensive patients with renal artery stenosis". Cochrane Database of Systematic Reviews 2014 (12): CD002944. doi:10.1002/14651858.CD002944.pub2. PMID 25478936. 
  16. ↑ Fine, Richard N.; Webber, Steven A.; Harmon, William E.; Kelly, Deirdre; Olthoff, Kim M. (2009-04-08). Pediatric Solid Organ Transplantation. John Wiley & Sons. ISBN 9781444312737. https://books.google.com/books?id=NmHE1XsZ6ScC&q=nephrectomy%29%2520%2520may%2520reduce%2520hypertension&pg=PA155. 
  17. ↑ Chrysant, Steven G.; Chrysant, George S. (February 2014). "Treatment of hypertension in patients with renal artery stenosis due to fibromuscular dysplasia of the renal arteries". Cardiovascular Diagnosis and Therapy 4 (1): 36–43. doi:10.3978/j.issn.2223-3652.2014.02.01. PMID 24649423. 

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