Pediatr Radiol DOI 10.1007/s00247-013-2818-7

CASE REPORT

Cortical necrosis secondary to trauma in a child: contrast-enhanced ultrasound comparable to magnetic resonance imaging Gibran T. Yusuf & Maria E. Sellars & Dean Y. Huang & Annamaria Deganello & Paul S. Sidhu

Received: 2 May 2013 / Revised: 28 June 2013 / Accepted: 3 October 2013 # Springer-Verlag Berlin Heidelberg 2013

Abstract Cortical necrosis is an uncommon cause of renal impairment and is rarely a consequence of blunt abdominal trauma. We present a case of unilateral traumatic acute cortical necrosis in a child demonstrated on contrast-enhanced US with confirmation on MRI. Contrast-enhanced US provides a rapid, accurate evaluation of renal parenchyma abnormalities in blunt abdominal trauma in children without exposure to ionising radiation or the risk of sedation. Keywords Cortical necrosis . Trauma . Paediatric . Contrast-enhanced ultrasound . Magnetic resonance imaging

and histological confirmation. Gold standard imaging includes CT and MRI, which demonstrate the absence of renal cortical enhancement following intravascular contrast administration; however this exposes the patient to potentially nephrotoxic contrast agents. Ultrasonography has played a limited role in the establishment of acute cortical necrosis. We report a case of blunt trauma in a child resulting in unilateral acute sub-capsular cortical necrosis clearly depicted on contrast-enhanced US, with MR imaging appearances confirming the diagnosis.

Case report Introduction Renal cortical necrosis is a rare cause of renal failure and is characterised by ischaemia of the renal cortex with sparing of the medulla. The underlying mechanism is renal hypoperfusion reported following postpartum haemorrhage, systemic sepsis, renal transplantation, snake bite and renal arterial injury [1]. The predominant underlying cause is usually systemic; bilateral renal cortical necrosis results with both acute and chronic renal failure. In the acute phase complications include hyperkalaemia, fluid overload and cardiac arrhythmia and in the long term chronic renal disease may necessitate dialysis or even transplantation. Traditional diagnosis is based on a high level of suspicion in acute renal failure Electronic supplementary material The online version of this article (doi:10.1007/s00247-013-2818-7) contains supplementary material, which is available to authorized users. G. T. Yusuf : M. E. Sellars : D. Y. Huang : A. Deganello : P. S. Sidhu (*) King’s College London, Department of Radiology, King’s College Hospital, Denmark Hill, London SE5 9RS, UK e-mail: [email protected]

A healthy 3-year-old boy sustained blunt trauma when a gymnasium dumbbell weight was inadvertently dropped onto his abdomen. At admission to the hospital, clinical examination revealed generalised abdominal bruising and tenderness but with maintained haemodynamic stability. Haematological and biochemical markers were normal. A t r i p l e- p ha s e c o n t r as t - e nh a n ce d C T ex a m i n at i o n (LightSpeed Pro 32; GE Healthcare, Barrington, IL) demonstrated single-organ injury involving the left kidney (Fig. 1). A truncated left renal artery was noted and the left kidney was of low density, mildly enlarged with no contrast enhancement. The truncated left renal artery was thought to be a consequence of a traumatic arterial dissection. The child was admitted for continuing management and transferred to our institution on day 3. US examination on days 3 and 4 following initial injury demonstrated no colour Doppler signal in the left kidney. On day 5 the sonographic examination demonstrated some venous colour Doppler signal in the renal hilum (Fig. 2). To better ascertain renal vascularity a contrastenhanced US was performed using SonoVue™ as the

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performed because the injury was not thought to be suitable for vascular stenting. Three months after discharge there was persistent hypertension; diminished unilateral renal function necessitated a left nephrectomy performed via laparoscopy, with normalisation of the blood pressure post-surgery.

Discussion

Fig. 1 Contrast-enhanced CT in a 3-year-old boy following blunt trauma to the abdomen. Axial image at the level of the renal arteries demonstrates a truncated left renal artery (short arrow) and a non-perfused left kidney that is diffusely enlarged (long arrow) in comparison to the right kidney. The truncated left renal artery was thought to be a consequence of a traumatic arterial dissection

microbubble contrast agent (1.2 ml, Bracco SpA, Milan, Italy). A 6-MHz curvilinear transducer on an ACUSON S2000 (Siemens, Mountain View, CA) was used, and a low mechanical index technique (CPS™; Siemens, Mountain View, CA) was employed to image the kidney with the microbubble contrast agent. In contrast to the CT examination (which had been performed 5 days earlier), US showed the left kidney to be perfused with enhancement of the entire medulla of the kidney but with obvious non-enhancement of the sub-capsular renal cortex (Fig. 3) (Video 1). MR imaging on a MAGNETOM Avanto machine (Siemens, Erlangen, Germany) was performed within 24 h and demonstrated a high signal within the peripheral sub-capsular renal cortex on T2-weighted images; however on gadolinium-enhanced T1-weighted images there was no enhancement of the renal cortex (Fig. 4). The child remained stable with no radiologic intervention

Fig. 2 Colour Doppler US in a 3-year-old boy 5 days after abdominal trauma. Longitudinal B-mode sonographic image of the left kidney demonstrates colour Doppler signal in the hilum (arrow), which was demonstrated to be venous on spectral Doppler (not shown)

We describe a child with substantial blunt trauma to the abdomen, with vascular compromise to the left kidney, who developed acute sub-capsular cortical necrosis demonstrated elegantly on a contrast-enhanced US examination. Imaging findings were identical to those on contrast-enhanced MR imaging. Contrast-enhanced US allowed a definitive assessment of non-vascularity of the sub-capsular renal cortex but also demonstrated the preservation of medullary vascularity. Collaterals from the adrenals, lumbar and peri-ureteric arteries normally preserve medullary vascularity. The vasa recta that supply the medulla arise from juxtamedullary efferent arterioles and these vessels are proximal to the outer cortex; occlusion of the outer cortical vessels causes cortical necrosis and sparing of the medulla. The usefulness of contrast-enhanced US in a child to demonstrate acute sub-capsular cortical necrosis was confirmed on MR imaging. Real-time imaging with patient tolerance in a contrast-enhanced US examination has the potential to obviate the need for CT and MR imaging and the risks associated with contrast administration, ionising radiation and sedation. The unilateral nature of the subcapsular cortical necrosis did not result in immediate renal compromise but eventual surgical nephrectomy was required. Cortical necrosis is a rare cause of acute renal failure, accounting for only about 2% of cases. Renal failure in these cases is thought to be caused by prolonged arterial hypo-perfusion, usually bilateral. The exact aetiology of cortical necrosis remains unclear, but it has been presumed that there is an intense vasospasm of the arterioles, and if this vasospasm remits then acute tubular necrosis ensues. However if the vasospasm persists then micro-vascular thrombosis occurs in the distal arterioles and glomeruli, resulting in cortical necrosis. Different forms of cortical necrosis have been described depending on the extent of necrotic change. In the acute phase the clinical presentation is with anuria and acute kidney injury, and subsequently chronic renal failure may ensue and carries a mortality rate of up to 50% when bilateral [1]. Prevention of chronic complications can be averted by early dialysis, emphasising the need for prompt recognition and treatment. Contrast-enhanced US provides excellent spatial resolution and can accurately determine the extent of devascularisation better than colour Doppler imaging

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Fig. 3 Contrast-enhanced US in a 3-year-old boy 5 days after abdominal trauma. a Longitudinal image of the left kidney 15 s following contrast administration, in the early arterial phase, demonstrates no enhancement of the cortex (arrows) but marked enhancement of the remainder of the

kidney. b Transverse view through the renal hilum at 1 min 58 s following contrast enhancement demonstrates the cortical non-enhancement (short arrow). There is contrast enhancement of the main left renal vein (long arrow)

while maintaining the advantage of being portable and available for bedside use. Cortical necrosis has been described with contrast-enhanced CT [2] and MR imaging [3]. Contrast-enhanced CT demonstrates an avascular cortex but preserved medullary enhancement. However in the acute phase the CT appearances can be nonspecific and show diffusely low-density, poorly visualised kidneys, which can lead to an overestimation of the degree of ischaemia, as was seen in our case. MR imaging demonstrates similar appearances with poor cortico-medullary differentiation on T1-W imaging, while T2-weighted images show cortical hyperintensity and T1-weighted contrastenhanced images show a lack of cortical enhancement. Both the CT and MR examinations provide a snapshot of the clinical abnormality, whereas contrast-enhanced US allows for the continued and uninterrupted visualisation of the dynamic manifestations of the disease process, which when recorded as a cine-loop allows for repeated viewing and interpretation. The inherent superior resolution of a sonographic examination, particularly in a child, allows for subtle changes to be observed. The findings on grey-scale sonography are non-specific, although description of peripheral

cortical low echogenicity has been noted. A recent study of contrast-enhanced US in adult renal transplant patients to demonstrate the non-vascularisation of the renal cortex concluded that other imaging is not necessary to establish the diagnosis of cortical necrosis [4]. Microbubble contrast agents have become widely used in adults, with recent guidelines establishing the accuracy and usefulness of this technique [5]. Although licensed for use in many countries in Europe and Asia, microbubble contrast agents for radiology are not licensed in North America. The application of these microbubble contrast agents in children remains controversial [6]. Previously only Levovist™ (Schering, Berlin, Germany), a US contrast microbubble that is no longer manufactured, was licensed for use in children, and then only for the demonstration of vesico-ureteric reflux. In a survey of paediatric radiologists, 60% did not perform contrast-enhanced US in children but more than 40% desired paediatric approval [7]. Even if a product is not licensed for paediatric use physicians can use a product off-licence providing they are well-informed and the intent is to “practice medicine”, and in these cases there is no need for specific

Fig. 4 MRI in a 3-year-old boy with blunt abdominal trauma. a Axial T1-weighted image at the level of the left renal artery. b Axial T2weighted image at the level of the kidneys demonstrates faint sub-capsular high signal intensity (arrows), with overall reduced signal of the left

kidney in comparison to the right kidney. Movement artefact degrades the image. c Axial gadolinium-enhanced T1-weighted image at the level of the kidneys confirms the contrast-enhanced US diagnosis of acute cortical necrosis, with identical imaging findings

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registration [5]. An essential component is an understanding of the risk profile; microbubble contrast agents remain safe in the adult population with very few minor adverse events recorded. In the adult population the reported complications after the administration of microbubble contrast agents is lower than that of contrast agents used in MR imaging. There are now reports of the practice of deploying microbubble contrast agents in paediatric patients in a variety of different clinical situations, aiding in diagnosis and without reported adverse effects [8]. We have described the use of contrast-enhanced US in a paediatric patient, clearly demonstrating acute subcapsular cortical necrosis with imaging that mirrors that seen on MR. The ability to demonstrate this abnormality accurately and safely on US has implications for cost as well as for patient morbidity in relation to ionising radiation and sedation.

Conflict of interest Maria E. Sellars, Annamaria Deganello, and Paul S. Sidhu have, all in the past received, lecture fees from Bracco SpA the manufacturer of the contrast media used for the present case. Gibran T. Yusuf and Dean Y. Huang have no conflict of interest.

References 1. Prakash J, Vohra R, Wani IA et al (2007) Decreasing incidence of renal cortical necrosis in patients with acute renal failure in developing countries: a single-centre experience of 22 years from eastern India. Nephrol Dial Transplant 22:1213–1217 2. Goergen T, Lindstrom RR, Tan H et al (1981) CT appearance of acute renal cortical necrosis. AJR Am J Roentgenol 137:176–177 3. Jeong JY, Sim JS, Lee HJ et al (2002) MR findings of renal cortical necrosis. J Comput Assist Tomogr 26:232–236 4. Fernandez CP, Ripolles T, Martinez MJ et al (2013) Diagnosis of acute cortical necrosis in renal transplantation by contrast-enhanced ultrasound: a preliminary experience. Ultraschall in Med 34:338–342 5. Piscaglia F, Nolsoe C, Dietrich CF et al (2012) The EFSUMB guidelines and recommendations on the clinical practice of contrast enhanced ultrasound (CEUS): update 2011 on non-hepatic applications. Ultraschall in Med 32:33–59 6. Sidhu PS, Choi BI, Bachmann-Nielsen M (2012) The EFSUMB guidelines and recommendations on the clinical practice of contrast enhanced ultrasound (CEUS): a new dawn for the escalating use of this ubiquitous technique. Ultraschall in Med 32:5–7 7. Riccabona M (2012) Application of a second-generation US contrast agent in infants and children – a European questionnaire-based survey. Pediatr Radiol 42:1471–1480 8. Piskunowicz P, Kosiak W, Batko T (2012) Intravenous application of second-generation ultrasound contrast agents in children: a review of the literature. Ultraschall in Med 33:135–140

Cortical necrosis secondary to trauma in a child: contrast-enhanced ultrasound comparable to magnetic resonance imaging.

Cortical necrosis is an uncommon cause of renal impairment and is rarely a consequence of blunt abdominal trauma. We present a case of unilateral trau...
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