Saudi Journal of Kidney Diseases and Transplantation

ORIGINAL ARTICLE
Year
: 2006  |  Volume : 17  |  Issue : 2  |  Page : 168--170

Diagnostic Value of Doppler Ultrasound in Differentiating Prerenal Azotemia from Acute Tubular Necrosis in Children


Alaleh Gheisari1, Mahshid Haghighi2,  
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

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

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.



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;17:168-170


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 2021 May 15 ];17:168-170
Available from: https://www.sjkdt.org/text.asp?2006/17/2/168/35785


Full Text

 Introduction



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



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



The two-tailed Student's "t" test was used to compare the values of RI between ATN and prerenal failure groups. Values of P [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.

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