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| | | Year : 2010 | Volume : 21 | Issue : 1 | Page : 123-127 | | | Changes in renal cortical and medullary perfusion in a patient with renal vein thrombosis | | | Jafar Al-Said1, Olfat Kamel2
1 Department of Nephrology, Bahrain Specialist Hospital, Manama, Bahrain,
2 Department of Radiology, Bahrain Specialist Hospital, Manama, Bahrain,
Click here for correspondence address and email | Date of Web Publication | 8-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 2014 Mar 3];21:123-7. Available from: http://www.sjkdt.org/text.asp?2010/21/1/123/58786 |
| Introduction | |  |
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 | | |
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 | | |
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 | | |
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 | | |
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 | | |
| 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.  | | 2. | Betram KL, William KF. Laboratory assessment of renal disease. Brenner and Rector's. TheKidney, Saunders. 6 th edition. 2000:1129-1142. | | 3. | | | 4. | Rosner M, Bolton K. Renal function testing. Am J Kidney Dis 2006;47(1):174-83. | | 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. | | 6. | Flavio G, Norberto P. Plasma Clearance of Nonradioactive Iohexol as a measure of GFR. J Am Soc Nephrol 1995;6:2. | | 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. | | 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. | | 9. | Lindblad HG, Berg UB. Comparative evaluation of Iohexol and Inulin clearance for GFR determinations. Acta Pediatr 1994;83(4):418-22. | | 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. | | 11. | O'Dell-Aderson KJ. Determination of GFR in dogs using contrast enhanced computed tomography. Vt Radiol Ultrasound 2006;47(2):127-35. | | 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. |
Correspondence Address:
Jafar Al-Said
Bahrain Specialist Hospital, P.O. Box 10588, Manama, Bahrain
PMID: 20061706
[Figure 1], [Figure 2], [Figure 3], [Figure 4] | |
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