MDCT Findings of Renal Trauma

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1 MDT of Renal Trauma Genitourinary Imaging Pictorial Essay Downloaded from by on 04/06/18 from IP address opyright RRS. For personal use only; all rights reserved D E M N E U T R Y L I M I G O F I N G Soo Jin Park 1 Jeong Kon Kim Kyoung Won Kim Kyoung-Sik ho Park SJ, Kim JK, Kim KW, ho K-S Keywords: T, kidney, MDT, trauma, urinary tract DOI: /JR Received March 28, 2005; accepted after revision June 7, ll authors: Department of Radiology, san Medical enter, Poongnap-dong, Songpa-gu, Seoul , South Korea. ddress correspondence to J. K. Kim (rialto@amc.seoul.kr). JR 2006; 187: X/06/ merican Roentgen Ray Society MDT Findings of Renal Trauma OJETIVE. The purposes of this pictorial essay are to show MDT findings of renal trauma and describe the indications and protocol for MDT. ONLUSION. T is indicated when patients have gross hematuria, hypotension, lumbar spinal injury, and fractures of lower ribs or the transverse process. The T examination must be designed specifically for urinary tract evaluation, and MDT is especially useful for this purpose. Injury to the kidney is graded I to V according to degree of laceration and amount of hematoma. he urinary tract is commonly involved in abdominal trauma, ac- T counting for 8 10% of trauma-related injuries to abdominal organs [1 3]. urrent concepts of management of renal trauma tend to promote the use of less invasive procedures and conservative management. In some cases of severe injury, however, surgical intervention is mandatory [1, 3 5]. It therefore is important to precisely determine whether to provide conservative or surgical treatment. mong the various imaging tools, T is the technique of choice for evaluating renal trauma [2 4]. MDT in particular can give accurate information about the status of the renal parenchyma, blood vessels, and collecting system because this technique can cover a target organ in a shorter time and with a thinner section slice than conventional T. In this pictorial essay, we show MDT findings of renal trauma and discuss the indications and protocol for MDT. Indications for T Gross hematuria is the most reliable indicator of serious urologic injury, although the degree of hematuria does not correlate with the degree of renal injury [1 3]. T is generally indicated when injured patients have gross hematuria, hypotension (systolic blood pressure < 90 mm Hg), lumbar spinal injury, and fractures of the lower ribs or a transverse process [1 3]. Whenever urinary tract injury is clinically suggested, it is necessary to perform T designed specifically for urinary tract evaluation. In particular, children with blunt trauma should undergo renal imaging regardless of the presence of hypotension or the degree of hematuria [2]. Patients need to be able to tolerate immobilization for several minutes during the examination, and therefore T sometimes is unsuitable for patients in hemodynamically unstable condition. MDT Protocol for Evaluation of the Urinary System For appropriate evaluation of the urinary system, it is necessary to evaluate all parts of the urinary tract, including the renal vasculature and parenchyma. Our institution therefore routinely obtains vascular phase scans and nephrographic excretory phase scans. late excretory phase scan can be added for patients with urinary tract obstruction. Three-dimensional reconstruction can be performed to supplement the information obtained on transverse T images. It is difficult to determine scanning parameters because MDT detector array systems vary. The general rule, however, is to specify slice thickness, table speed, voltage, and current. Scan delay is important in urinary tract imaging. For vascular phase scans, a scan delay of seconds is reasonable. However, because hemodynamic status varies greatly according to patient factors, automatic bolus tracking is better than a fixed scan delay. For evaluating the urinary tract, the scan delay can vary (180 minutes or more) according to the degree of urinary obstruction. Section thickness is another important parameter in T acquisition. For renal vascular JR:187, ugust

2 Downloaded from by on 04/06/18 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old woman with grade I injury., Drawing shows subcapsular hematoma., ontrast-enhanced T scan at early excretory phase shows crescent-shaped fluid collection (arrows) between renal capsule and renal parenchyma., Sagittal reformation of shows fluid collection (arrows). imaging, most MDT systems operate with a section thickness of mm, which seems adequate for visualization of the status of the renal vasculature because the diameter of the main renal artery is 4 6 mm and that of the accessory arteries is usually mm. n overlapped reconstruction interval is recommended for T angiography. For evaluation of the renal parenchyma, a section thickness of mm is sufficient. For visualization of the status of the rest of the urinary tract, a section thickness of mm seems appropriate. eam pitch of 1 or 1.5 seems suitable for MDT, and voltage of kv is appropriate. Tube current should be carefully considered in young patients to reduce radiation hazard. ccording to one guideline [6], the weighted T dose index for the entire T examination should be less than 35 mgy. To meet that criterion, our institution uses m of current for each scan phase. lunt Trauma Induced Renal Injury lunt trauma can be associated with various kinds of trauma, such as motor vehicle accidents, falls, and blunt physical contact [1]. The main mechanism of blunt trauma is exertion of deceleration force on the renal parenchyma, major renal vessels, and renal collecting system [4]. Rapid deceleration thrusts the kidney against the rib cage or vertebral column, resulting in contusion, laceration, hemorrhage, and avulsion of the renal pedicle [7]. 542 JR:187, ugust 2006

3 MDT of Renal Trauma Downloaded from by on 04/06/18 from IP address opyright RRS. For personal use only; all rights reserved Severity Grade and orresponding T Findings Grade I Grade I renal injuries, which account for approximately 80% of renal injuries, are Fig year-old man with grade II injury to left kidney., Drawing shows cortical laceration less than 1 cm deep and perinephric hematoma., ontrast-enhanced T scan at corticomedullary phase shows cortical laceration (arrow) and perinephric hematoma (arrowheads). Fig. 3 5-year-old boy with grade III injury., Drawing shows laceration more than 1 cm deep and perinephric hematoma. (Fig. 3 continues on next page) characterized by contusion and nonexpanding subcapsular hematoma without parenchymal laceration [1 3]. The T findings of renal contusion include ill-defined and discrete areas of low density and decreased enhancement. Subcapsular hematoma shows high-density fluid collection between the renal capsule and renal parenchyma on unenhanced scans and no contrast enhancement [1, 3] (Fig. 1). JR:187, ugust

4 Downloaded from by on 04/06/18 from IP address opyright RRS. For personal use only; all rights reserved Fig. 3 (continued) 5-year-old boy with grade III injury., ontrast-enhanced T scan at early excretory phase shows cortical laceration (arrow) more than 1 cm deep and perinephric hematoma., Thin-slab maximum intensity projection in oblique coronal plane shows laceration (arrow) and hematoma. Fig. 4 6-year-old boy with grade IV injury to right kidney., Drawing shows laceration extending through renal collecting system., Thin-slab maximum-intensity-projection T scan in oblique coronal plane obtained at corticomedullary phase shows laceration throughout parenchyma (arrow). (Fig. 4 continues on next page) 544 JR:187, ugust 2006

5 MDT of Renal Trauma Downloaded from by on 04/06/18 from IP address opyright RRS. For personal use only; all rights reserved Fig. 4 (continued) 6-year-old boy with grade IV injury to right kidney., Maximum intensity projection shows leakage of contrast material (arrows) caused by laceration of collecting system. D, Volume-rendering oblique coronal image shows leakage of contrast material (arrows). Grade II Grade II renal injuries are characterized by nonexpanding perinephric hematoma confined to the retroperitoneum and by cortical laceration < 1 cm deep without involvement of the collecting system [1]. The T finding of perinephric hematoma is illdefined, high-density fluid collection between the renal parenchyma and Gerota s fascia [1] (Fig. 2). On T scans renal parenchyma laceration appears as irregular or linear parenchymal defects, which may contain blood clots. Grade III Grade III renal injuries are characterized by nonexpanding perinephric hematoma confined to the retroperitoneum and by laceration more than 1 cm deep. In this grade of injury, the collecting system is preserved, and laceration involves the renal cortex and medulla [1] (Fig. 3). Fig. 5 8-year-old girl with segmental renal artery infarction in left kidney. ontrastenhanced T scan in early excretory phase shows well-circumscribed wedgeshaped nonenhancing areas (arrow). Grade IV Grade IV renal injuries are characterized by lacerations extending through the renal collecting system and by damage of main renal vessels [1] (Fig. 4). Segmental infarction can be caused by thrombosis, dissection, or laceration of segmental renal arteries [1]. T findings of segmental infarction include wellcircumscribed linear or wedge-shaped, multifocal nonenhancing areas in the renal parenchyma [1 3] (Fig. 5). D JR:187, ugust

6 Downloaded from by on 04/06/18 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old woman with grade V injury to left kidney., Drawing shows shattered kidney., ontrast-enhanced T scan at early excretory phase shows shattering (arrow). Fig year-old man with grade V injury to left kidney., Drawing shows laceration of main renal artery resulting in devascularization of affected kidney., ontrast-enhanced T scan at nephrographic phase shows hematoma (arrows) around left renal artery and lack of enhancement of kidney. Grade V Grade V renal injuries are characterized by shattering or devascularization of the kidney [1, 3], by avulsion of the ureteropelvic junction, and by complete thrombus or laceration of the main renal vessels. Shattered kidney refers to gross disruption of the renal parenchyma by multiple lacerations (Fig. 6). The T findings of traumatic renal infarction caused by complete thrombus or laceration of the main renal artery include lack of enhancement in the nephrographic phase on the affected side (Fig. 7) and retrograde opacification of the renal vein from the inferior vena cava [3]. Iatrogenic Injury The kidneys can be exposed to iatrogenic injuries such as intraabdominal surgery, needle biopsy, percutaneous nephrostomy, and extracorporeal shock wave lithotripsy. These iatrogenic injuries can result in renal hematoma, laceration, pseudoaneurysm, and arteriovenous fistula (Fig. 8). 546 JR:187, ugust 2006

7 MDT of Renal Trauma Downloaded from by on 04/06/18 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old woman with iatrogenic arteriovenous fistula sustained during biopsy., ontrast-enhanced T scan at corticomedullary phase shows fistula (arrow)., Maximum intensity projection in coronal plane shows fistula (arrow). Fig year-old man with infected hematoma after cortical laceration. ontrast-enhanced T scan at early excretory phase shows fluid collection with wall enhancement (arrows) around right kidney. omplications fter Renal Trauma The complication rate for renal trauma ranges from 3% to 10% [2]. Early complications include urinoma, delayed bleeding, urinary fistula, abscess, and hypertension [2, 8]. Urinoma is the most common complication of renal trauma, and delayed bleeding usually occurs within 1 2 weeks after injury [2]. Urinary fistula and abscess can be associated with an undrained fluid collection or a large segment of devitalized renal parenchyma (Fig. 9). Late complications after renal trauma include hydronephrosis, arteriovenous fistula, pyelonephritis, calculus formation, and delayed hypertension [2]. References 1. Smith JK, Kenney PJ. Imaging of renal trauma. Radiol lin North m 2003; 41: Kawashima, Sandler M, orl FM, et al. Imaging of renal trauma: a comprehensive review. Radio- Graphics 2001; 21: Harris, Zwirewich V, Lyburn ID, Torreggiani W, Marchinkow LO. T findings in blunt renal trauma. RadioGraphics 2001; 21:S201 S Goldman SM, Sandler M. Urogenital trauma: imaging upper GU trauma. Eur J Radiol 2004; 50: Heyns F. Renal trauma: indications for imaging and surgical exploration. JU Int 2004; 93: European guidelines on quality criteria for computed tomography. vailable at: guidelines/ct/quality/mainindex.htm. ccessed ugust Mcninch JW, Santucci R. Genitourinary trauma. In: Walsh P, ed. ampbell s urology, 8th ed. Philadelphia, P: Saunders, 2002: Santucci R, Wessells H, artsch G, et al. Evaluation and management of renal injuries: consensus statement of the renal trauma subcommittee. JU Int 2004; 93: JR:187, ugust