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Saudi Journal of Kidney Diseases and Transplantation
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CASE REPORT Table of Contents   
Year : 2010  |  Volume : 21  |  Issue : 1  |  Page : 123-127
Changes in renal cortical and medullary perfusion in a patient with renal vein thrombosis


1 Department of Nephrology, Bahrain Specialist Hospital, Manama, Bahrain
2 Department of Radiology, Bahrain Specialist Hospital, Manama, Bahrain

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Date of Web Publication8-Jan-2010
 

   Abstract 

Dynamic renal perfusion computerized tomographic (CT) scan was performed to test the cortical and medullary perfusion in a patient with unilateral renal vein thrombosis secondary to idiopathic focal and segmental glomerulosclerosis (FSGS). Forty mL of Iohexol was injected intra­venously. Multiple fixed repeated axial renal CT scan cuts at specific intervals, over the mid pole, were recorded over 400 seconds. Radio density was measured over the aorta, cortex and medulla during that period. Graphs for the radio contrast density against time were plotted. Aortic, cortical and medullary perfusions were calculated by estimating the slopes of the curves. Based on the CT scan findings, perfusion of different parts of the kidney was measured. The reduction in kidney function with renal vein thrombosis seems to be secondary to hypoperfusion of renal cortex and medulla. Further studies are required to confirm this observation. The blood flow to the kidney im­proved within four days after therapy with anticoagulation and pulse steroids. The sequences of events that take place need further studies for validation.

How to cite this article:
Al-Said J, Kamel O. Changes in renal cortical and medullary perfusion in a patient with renal vein thrombosis. Saudi J Kidney Dis Transpl 2010;21:123-7

How to cite this URL:
Al-Said J, Kamel O. Changes in renal cortical and medullary perfusion in a patient with renal vein thrombosis. Saudi J Kidney Dis Transpl [serial online] 2010 [cited 2020 Jan 29];21:123-7. Available from: http://www.sjkdt.org/text.asp?2010/21/1/123/58786

   Introduction Top


Renal vein thrombosis (RVT) is one of the known complications of the nephrotic syndrome. Its reported incidence is higher in association with malignancies and membranous nephropathy with nephrotic syndrome. [1],[2] Alteration in perfu­sion of the renal cortex and medulla has not been studied in patients with RVT. In this case, we report renal perfusion of the cortex and me­dulla using a dynamic renal perfusion compu­terized tomographic (CT) scan in a patient with acute RVT, before and after therapy.


   Case Presentation Top


The studied patient is a 45-year-old male, who had six months history of lower extremity edema and foamy urine. He was diagnosed to have the nephrotic syndrome due to biopsy proven pri­mary focal and segmental glomerulosclerosis (FSGS). He presented to the emergency room with sudden onset of severe right flank pain with chills and sweating of few hours duration. During this period, he had two bouts of gross hematuria, but no other urinary symptoms. The patient had history of hypertension. He had no fever. At presentation, he was taking prednisone 40 mg and perindopril 4 mg daily for few weeks. On physical examination, he was in pain, the blood pressure was 140/90 mmHg, pulse rate was 100/min and temperature was 36.6°C. Apart from significant tenderness over the right loin, examination of the chest, heart and abdomen were normal. Laboratory evaluation showed: hemoglobin (Hb) of 12 gm/L, white blood cell (WBC) count of 19.7 Χ 10 9 /L, blood urea of 69 mg/dL, and serum creatinine of 1.9 mg/dL with eGFR of 33 mL/min. About two weeks prior to presentation, his serum creatinine was 1.3 mg/dL. Urine analysis revealed specific gravity of 1020, numerous red blood cells (RBC) and spot urine albumin/creatinine ratio of 1500 mg/gm. Ultra­sound of the kidneys had been performed a few weeks prior to presentation and it was normal. CT scan of the abdomen showed complete RVT on the right side and edematous enlarged right kidney with perinephric stranding [Figure 1]. The patient was given intravenous (i.v.) heparin infusion with target PTT of 70-80 secs. Three days later, warfarin was started. Target INR was kept between 2-3. Solumedrol 500 mg i.v. was given daily for three doses followed by predni­sone 60 mg/day. The patient's clinical condition and kidney function improved within 24 hours. Serum creatinine and urea started decreasing. Serum creatinine after two weeks from admis­sion was 1.2 mg/dL. CT scan was repeated four days later and showed that the size of the right kidney was reduced with disappearance of the edema and the perinephric stranding [Figure 2]. The thrombus in the right renal vein had be­come smaller. After six weeks of treatment, the calculated creatinine clearance was 87 mL/min. Renal perfusion CT scans were performed be­fore starting the treatment and four days later. The procedure was done with 40 mL of iohexol injected i.v. Multiple fixed repeated axial renal CT scan cuts at specific intervals over the mid­pole were recorded for 400 seconds. Radio den­sity was measured over the aorta, cortex and medulla during that period. Graphs for the radio contrast density against time were plotted. Aor­tic, cortical and medullary perfusion were cal­culated by estimating the slopes of the curves.


   Discussion Top


Renal CT Perfusion Scan

CT scan has been used widely in medical diag­nosis. The contrast material given with CT scan is infused i.v. it perfuses the venous system and then passes to the arterial system. When it rea­ches the kidneys, it passes through the major renal arteries to the interlobar, arcuate, and then to the interlobular arteries. The contrast then passes through the afferent arterioles, the glome­rular tuft and finally to the efferent arterioles. From the juxtamedullary glomeruli, the contrast passes through the efferent arterioles to the des­cending vasa recta then to the outer and inner medulla to form the tubular capillary bed. Part of the blood that perfuses the renal cortex will form the glomerular filtrate. The remaining will return through the venous system to the sys­temic circulation. Urine, which is the part of the glomerular filtrate that did not undergo reab­sorption or got secreted in the tubules, will pass through the collecting tubules to the ureters and the urinary bladder.

Theoretically, if we could measure the concen­tration of contrast over time during its passage with the blood through the kidney, starting from the major vessels to the renal pelvis, then the perfusion and the function of each part of the kidney can be identified and measured sepa­rately. Since it is not practical to get a sample of blood from different parts of the nephron, kno­wing that different concentration of the contrast will generate different radio density, the corre­lation tested in a separate experiment showed an R 2 of 0.95. Thus, by measuring the contrast opacification, i.e. radio density in different parts of the kidney, the contrast concentration can be estimated. Plotting these measurements against time would produce a functional and perfusion curves at different segments of the kidney. In other words, we could substitute radio density for all concentrations and use it for calculation of GFR and to determine perfusion.

Iohexol (Omnipaue)

Iohexol is a non-ionic low osmolar, iodine­based hydrophobic contrast. It is minimally bound to plasma protein and has low molecular weight of 821 kilo Daltons in comparison to inulin, which has a molecular weight of 5000 kilo Dal­tons. Iohexol is mainly excreted unchanged in the urine, after it perfuses the renal circulation in the sequence mentioned above. It is not me­tabolized in the body. The half-life with normal kidney function is approximately two hours. [3] Investigators have used it to measure the GFR. Published studies since the mid-eighties had used animal and human models to measure the GFR using plasma concentration of iohexol at different time intervals. [4],[5],[6],[7],[8],[9] In few studies, it was compared to inulin, which is the gold standard of measuring kidney function. The clearance curves of both substances were plotted for di­fferent populations including pediatric, normal adults, patients with impaired kidney function and even in ICU patients. [10],[11] These compara­tive studies had concluded that iohexol is as good as inulin in measuring the GFR. Some studies concluded that iohexol clearance is even more accurate in representing GFR in patients having advanced renal disease. [12]




   Mathematical Calculations Top


Correlation of the concentration of the contrast with the radio density was tested by measuring the density of different known concentrations at 25% concentration increments of the contrast with CT scan. R 2 was found to be 0.95 in an experimental model.

The upward slope of the curve from time zero till the peak over the aorta, renal artery, renal cortex, and renal medulla was calculated using mathematical equation to reflect the perfusion of that part of the kidney. The cortical and me­dullary perfusion curves follow aortic curves but have lower peaks and take longer time to reach maximum peaks. These curves are almost identical to isotope renal scan curves as ob­served in unpublished data.

The renal perfusion CT scan was performed on our patient at admission, and it showed cor­tical and medullary hypoperfusion of the right kidney as compared to the contralateral kidney [Figure 3]. There was a significant statistical difference in the radio density between the right and left renal cortex (P< 0.0001). The aortic up­wards radio density slope was 0.01. The upward slope for the right cortical radio-density was 0.25, while that for the left cortical radio den­sity was 0.037.

After four days of therapy with anticoagu­lation, CT perfusion scan was repeated and it showed an improvement in perfusion of both the cortex and medulla. The upward radio den­sity slope over the right cortex was 0.05 and over the right medulla was 0.06. There was a significant difference in the radio density curve of the right cortex before and after therapy (P< 0.0001). The difference in the radio density of the right medulla before and after therapy was also highly significant (P< 0.0001). On the other hand, the difference between the left cortical radio-density before therapy and the right corti­cal radio-density after therapy was not statis­tically significant P= 0.05, [Figure 4].

Deterioration in kidney function is one of the features of RVT. According to the perfusion graphs discussed above, the impaired kidney function associated with RVT could be secon­dary to hypoperfusion of the cortex and medulla, i.e. the thrombus will cause a high intravascular hydrostatic pressure in the second tubular capil­lary bed and perhaps the first capillary bed. This causes stunting of the blood flow or vaso­constriction with impaired perfusion as shown by the flat curves of radio contrast over both the cortex and medulla [Figure 3] and [Figure 4]. The ede­ma and swelling that is noticed in [Figure 1] could be an inflammatory reaction that is induced by ischemia or, a result of increased intravascular hydrostatic pressure in the affected kidney, lea­ding to extravascular fluid leak. The contribu­tion of the hemodynamic factor, as noticed in the perfusion scan, could trigger an inflam­matory reaction due to ischemia causing the release of cytokines, which causes activation of the inflammatory cascades. The disappearance of the edema after four days of therapy could be explained by combined anti-inflammatory ac­tion of the pulse steroid used and the fibrinolysis of part of the thrombus, which caused a reduction of the intravascular hydrostatic pressure with re­sumption of the normal cortical and medullary blood flow.


   Conclusion Top


Renal vein thrombosis causes cortical and me­dullary hypoperfusion. The blood flow was no­ticed to improve within four days after therapy with anti-coagulation and pulse steroids. The sequences of events that take place after acute RVT need further studies for validation.

 
   References Top

1.Wysokinsk WE, Gosk-Bierska I, Greene EL, Grill D, Wiste H, McBane RD 2nd. Clinical characteristics and long term follow-up of patients with renal vein thrombosis. Am J Kidney Dis 2008;51(2):224-32.  Back to cited text no. 1      
2.Betram KL, William KF. Laboratory assessment of renal disease. Brenner and Rector's. TheKidney, Saunders. 6 th edition. 2000:1129-1142.  Back to cited text no. 2      
3.  Back to cited text no. 3      
4.Rosner M, Bolton K. Renal function testing. Am J Kidney Dis 2006;47(1):174-83.  Back to cited text no. 4      
5.Anupama M, Robert T. Measurement of kidney function. In, Brian P, Mohammed S, Peter B. (Eds). Chronic kidney disease, Dialysis and Trans­plantation. Elsevier Saunders, 2nd edition. 2005: 20-30.  Back to cited text no. 5      
6.Flavio G, Norberto P. Plasma Clearance of Non­radioactive Iohexol as a measure of GFR. J Am Soc Nephrol 1995;6:2.  Back to cited text no. 6      
7.Flavio G, Guerini E. Perico N, et al. Glomerular filtration rate determine from a single plasma sample after intravenous Iohexol injection: Is it reliable? J Am Soc Nephrol 1996;7:12.  Back to cited text no. 7      
8.Erley CM, Badr BD, Berger ED, et al. Plasma Clearance of iodine contrast media as a measure of glomerular filtration rate in critical ill pa­tients. Crit Care Med 2001;29(8):1544-50.  Back to cited text no. 8      
9.Lindblad HG, Berg UB. Comparative evalua­tion of Iohexol and Inulin clearance for GFR determinations. Acta Pediatr 1994;83(4):418-22.  Back to cited text no. 9      
10.Hackstein N, Wiegand C, Rau WS, Langheinrich AC. Glomerular Filtration rate measured by using triphasic helical CT with a two-point Patlak Plot technique. Radiology 2004;230:221-6.  Back to cited text no. 10      
11.O'Dell-Aderson KJ. Determination of GFR in dogs using contrast enhanced computed tomo­graphy. Vt Radiol Ultrasound 2006;47(2):127­-35.  Back to cited text no. 11      
12.Poggio ED, Nef PC, Wang X, et al. Performance of the Cockcroft - - Gault and MDRD equations in estimating GFR in ill hospitalized patients. Am J Kidney Dis 2005;46(2):242-52.  Back to cited text no. 12      

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Correspondence Address:
Jafar Al-Said
Bahrain Specialist Hospital, P.O. Box 10588, Manama, Bahrain

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PMID: 20061706

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]



 

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    Abstract
    Introduction
    Case Presentation
    Discussion
    Mathematical Cal...
    Conclusion
    References
    Article Figures
 

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