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Saudi Journal of Kidney Diseases and Transplantation
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ORIGINAL ARTICLE Table of Contents   
Year : 2006  |  Volume : 17  |  Issue : 2  |  Page : 168-170
Diagnostic Value of Doppler Ultrasound in Differentiating Prerenal Azotemia from Acute Tubular Necrosis in Children


1 Department of Pediatrics, Al-Zahra Hospital, Isfahan University of Medical Sciences, Iran
2 Department of Radiology, Al-Zahra Hospital, Isfahan University of Medical Sciences, Iran

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   Abstract 

Differentiating acute tubular necrosis (ATN) from prerenal azotemia is critical for selecting the appropriate treatment. This study was conducted to evaluate the diagnostic value of Doppler ultrasonography in differentiating ATN from prerenal azotemia in children. A total of 50 oliguric or anuric children with previous normal renal laboratory data were included. Doppler examination and calculation of resistive index (RI) was performed within 24 hours of admission and in the recovery phase of ARF. The sensitivity and specificity of RI in differentiating ATN from prerenal azotemia were assessed. At the cut-off point of RI = 0.75, the sensitivity and specificity of RI in differentiating prerenal failure and ATN was 91.3% and 85.2%, respectively. We conclude that Doppler ultrasonography is helpful in differentiating ATN from prerenal azotemia in children. The cut-off value of 0.75 has the highest accuracy for this purpose.

Keywords: Ultrasound, Doppler, acute tubular necrosis, acute renal failure, prerenal.

How to cite this article:
Gheisari A, Haghighi M. Diagnostic Value of Doppler Ultrasound in Differentiating Prerenal Azotemia from Acute Tubular Necrosis in Children. Saudi J Kidney Dis Transpl 2006;17:168-70

How to cite this URL:
Gheisari A, Haghighi M. Diagnostic Value of Doppler Ultrasound in Differentiating Prerenal Azotemia from Acute Tubular Necrosis in Children. Saudi J Kidney Dis Transpl [serial online] 2006 [cited 2019 Jul 21];17:168-70. Available from: http://www.sjkdt.org/text.asp?2006/17/2/168/35785

   Introduction Top


Finding a reliable diagnostic modality for differentiating ATN from prerenal azotemia in children is important for multiple reasons. First, hypovolemia due to general medical problems such as gastroenteritis and poor nutrition is more common in children who are more susceptible to hypovolemia-induced renal failure than adults. Second, urinary diagnostic indices, including fractional excretion of sodium (FENa) and urine to plasma osmolality often cannot be used accurately, because of previous use of diuretics, crystalloids, or when the patient is completely anuric.

A few studies have been performed to evaluate the diagnostic value of Doppler ultrasonography (US) in ATN and prerenal azotemia. [1],[2],[3],[4],[5] Resistive index (RI) is the mostly used parameter, however the cut-off points are variable in different studies. Furthermore, the subjects in most of these studies are adults, while the renal blood flow indices are different in children.[6]

This study was conducted to evaluate the diagnostic value of Doppler US in different­iating prerenal failure from ATN, and to find an accurate cut-off point for RI in children.


   Patients and Methods Top


We studied 50 children with acute renal failure (ARF) (30 males, 20 females) aged one month to 15 years (mean 9.1 ± 0.9 years). They were referred to Al-Zahra university hospital, Isfahan, Iran between September 2003 and May 2004. All the patients were oliguric or anuric with previous normal renal function profile.

The diagnosis of ATN or prerenal azotemia was made on the basis of history, chart review, clinical follow-up and laboratory studies. In all the patients, Doppler US examination was performed within 24 hours of admission. The patients were treated appropriately based on clinical and laboratory findings. In the recovery phase of ARF (urine output> l cc/kg/hr), Doppler sonography was repeated in all of the cases.

Sonographic examinations were performed using a real-time ultrasound machine with color Doppler facility (Dornier, Germany) and a 5 MHz convex-type probe. Doppler ultrasound included conventional sonography to rule out morphologic abnormalities such as hydronephrosis or perirenal collections that may result in increased renal vascular resistance. The mean RI [(peak-systolic velocity - end-diastolic velocity) / peak-systolic velocity] was calculated as an average value obtained from three waveforms. Subsequently, the mean RI for each patient was considered as an average of both kidneys.


   Statistical Analysis Top


The two-tailed Student's "t" test was used to compare the values of RI between ATN and prerenal failure groups. Values of P < 0.05 were considered statistically significant. Sensitivity and specificity of RI in differentiating ATN from prerenal azotemia were determined in accordance with an optimally calculated cut-off point. Analyses were performed with the SPSS version 11 statistical package.


   Results Top


The mean RI in patients with ATN was significantly higher than in those with prerenal azotemia (0.82 ± 0.07 vs 0.76 ± 0.06, p<0.01). The mean reduction in RI values after treatment was also greater in patients with ATN (0.26 ± 0.01 vs 0.04 ± 0.00, p<0.01). The sensitivity and specificity of the RI=0.75 in differentiating prerenal failure and ATN was 91.3% and 85.2%, respectively.


   Discussion Top


ATN and prerenal failure are major causes of ARF. Differentiating these two conditions is important for appropriate management of the ARF cases. Because invasive examinations such as renal biopsy may not be feasible in critically ill patients, and because urinary indices may not be accurate due to prior use of diuretics, a safe and easily available diagnostic modality is highly warranted.

Several studies have evaluated the efficacy of Doppler US in the assessment of acute rejection of renal transplant. [7],[8],[9],[10],[11] Also a few studies have been performed to evaluate the role of Doppler US in discriminating the ATN and the prerenal failure. [1],[2],[3],[4],[5],[6] Overall, these studies proposed that Doppler US could be an accurate modality in differentiating between the ATN and the prerenal disease. However, there are two caveats: first, the studies failed to reach a unique cut-off value for RI; second, children were not included, which is important due to the fact that RI is influenced by age. [6]

Our results indicate that Doppler US had a high sensitivity and specificity in different­iating between ATN and prerenal azotemia in children. The measured sensitivity and speci­ficity are higher than prior reports in adults,[12],[13] which may indicate the higher accuracy of RI in children. The reported decrease of RI values after appropriate treatment ranges from 0.10 to 0.15 in patients with ATN, and from 0.01 to 0.02 in prerenal azotemia, which is lower than our data in children. [13],[14] This difference may be explained by the revers­ibility of the perfusion defects in children, and the different etiologies of the ATN in children and adults (e.g. decreased intravascular volume in children versus drug toxicity in adults).

In conclusion, our findings suggest that Doppler US is helpful in differentiating ATN from prerenal azotemia in children. The cut­off value of 0.75 has the highest accuracy for this purpose.

 
   References Top

1.Izumi M, Sugiura T, Nakamura H, Nagatoya K, Imai E, Hori M. Differential diagnosis of prerenal azotemia from acute tubular necrosis and prediction of recovery by Doppler ultrasound. Am j Kidney Dis 2000;35(4):713-9.  Back to cited text no. 1    
2.Wong SN, Lo RN, Yu EC. Renal blood flow pattern by noninvasive Doppler ultra­sound in normal children and acute renal failure patients. J Ulrasound Med 1989;8: 135-41.  Back to cited text no. 2    
3.Platt JF, Rubin JM, Ellis JH. Acute renal failure: possible role of duplex Doppler US in distinction between acute renal failure and acute tubular necrosis. Radiology 1991;179:419-23.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]
4.Yoon D, Kim H, Na D, et al. Doppler sonography in experimentally induced acute renal failure. Invest Radiol 1995;30:168-72.  Back to cited text no. 4    
5.Rivers BJ, Walter PA, Polzin DJ, King VL. Duplex doppler estimation of intrarenal pourcelot resistive index in dogs and cats with renal disease. J Vet Intern Med. 1997; ll(4):250-60.  Back to cited text no. 5    
6.Briscoe DM, Hoffer FA, Tu N, Harmon WE. Duplex Doppler examination of renal allo­grafts in children: correlation between renal blood flow and clinical findings. Pediatr Radiol 1993;23(5):365-8.  Back to cited text no. 6    
7.Tranquart F, Lebranchu Y, Haillot O, Pourcelot D, Grezard O, Pourcelot L. The use of peri­operative Doppler ultrasound as a screening test for acute tubular necrosis. Transpl Int 1993;6:14-7.  Back to cited text no. 7  [PUBMED]  
8.Arima M, Takahara S, Ihara H, et al. Predictability of renal allograft prognosis during rejection crisis by ultrasound Doppler flow technique. Urology 1982;19:389-94.  Back to cited text no. 8  [PUBMED]  
9.Perrella RR, Duerinckx AJ, Tessler FN, et al. Evaluation of renal tranplant dysfunction by duplex Doppler sonography: a prospective study and review of the literature. Am J Kidney Dis 1990;15:544-50.  Back to cited text no. 9  [PUBMED]  
10.Lee SK, Wang ML, Su YG, Shen WC, Ho YJ. Detection of renal allograft dysfunction with color Doppler flow ultrasound. Chung Hua I Hsueh Tsa Chih Taipei 1993;51(4):257-65.  Back to cited text no. 10    
11.Meyer M, Paushter D, Steinmuller DR. The use of duplex Doppler ultrasonography to evaluate renal allograft dysfunction. Trans­plantation 1990;50(6):974-8.  Back to cited text no. 11    
12.Handa N, Fukunaga R, Etani H, Yoneda S, Kimura K, Kamada T. Efficacy of echo-Doppler examination for the evaluation of renovascular disease. Ultrasound Med Biol 1988;14(l):l-5.  Back to cited text no. 12    
13.Yamaguchi S, Fujii H, Kaneko S, et al. Ultra­sonographic study on kidneys in patients with acute renal failure. Nippon Hinyokika Gakkai Zasshi 1991;82(10): 1561-7.  Back to cited text no. 13    
14.Sauvain JL, Bourscheid D, Pierrat V, et al. Duplex Doppler ultrasonography of intra­renal arteries. Normal and pathological aspects. Ann Radiol Paris. 1991;34(4): 237-47.  Back to cited text no. 14    

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Correspondence Address:
Alaleh Gheisari
Department of Pediatrics, Al-Zahra Hospital, Isfahan University of Medical Sciences, Isfahan
Iran
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PMID: 16903622

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    Abstract
    Introduction
    Patients and Methods
    Statistical Analysis
    Results
    Discussion
    References
 

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