CT Findings After Nephron-Sparing Surgery of Renal Tumors

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1 Lee et al. CT of Renal Tumors fter Nephron-Sparing Surgery Genitourinary Imaging Pictorial Essay Downloaded from by on 04/26/18 from IP address Copyright RRS. For personal use only; all rights reserved Mu Sook Lee 1 Young Taik Oh 1 Woong Kyu Han 2 Koon Ho Rha 2 Young Deuk Choi 2 Sung Joon Hong 2 Seung Choul Yang 2 Ki Whang Kim 1 Lee MS, Oh YT, Han WK, et al. Keywords: CT, kidney, nephron-sparing surgery, postoperative change, urinary system DOI: /JR Received May 10, 2007; accepted after revision June 7, Department of Diagnostic Radiology and Research Institute of Radiological Science, Yonsei University College of Medicine, Seodaemun-ku Shinchon-dong 134, Seoul , Republic of Korea. ddress correspondence to Y. T. Oh (oytaik@yumc.yonsei.ac.kr). 2 Department of Urology, Yonsei University College of Medicine, Seoul, Republic of Korea. WE This is a Web exclusive article. JR 2007; 189: X/07/ merican Roentgen Ray Society CT Findings fter Nephron-Sparing Surgery of Renal Tumors OJECTIVE. The purpose of this article is to show the CT findings of the various postoperative changes, surgical complications, and tumor recurrence after nephron-sparing surgery for the treatment of renal tumors. CONCLUSION. Familiarity with the various postoperative changes after nephron-sparing surgery may help radiologists in differentiating these changes from tumor recurrence or surgical complications. adical nephrectomy has been considered the standard treatment of R localized renal cell carcinoma (RCC). Today, advances in renal imaging, improved surgical technique, and the increasing number of incidentally detected small RCCs and benign renal tumors have stimulated the interest in and use of nephronsparing surgery and partial nephrectomy [1]. Imaging surveillance after nephron-sparing surgery is usually done with CT. CT findings after nephron-sparing surgery are different from those after radical nephrectomy. However, there is little in the literature describing CT findings after nephron-sparing surgery [2, 3]. Therefore, we aim to show the CT findings after nephron-sparing surgery, including the postoperative changes, tumor recurrence, and complications based on our vast retrospective reviews of follow-up CT scans. lso, we will discuss the differential points that help radiologists discriminate postoperative changes from tumor recurrence or complications. Surgical Techniques Nephron-sparing surgery can be performed by open surgery or laparoscopically. efore the excision of renal tumors, renal artery and renal vascular pedicles are usually clamped to decrease bleeding and to provide a clear surgical field. The acceptable warm ischemic time may be less than 30 minutes [4]. There are several surgical techniques for nephron-sparing surgery: segmental polar nephrectomy, wedge resection, transverse resection and enucleation; the method used depends on the mass size and location [5] (Fig. 1). ll of these techniques involve complete excision of the renal tumor with a proper margin of normal renal tissue [6] and preservation of the largest possible amount of functioning renal parenchyma. Hilar tumors, complex tumors such as deeper infiltrating tumors that require repair of the pelvicaliceal system, multiple tumors, and tumors with coexisting renovascular disease are a specific and significant technical challenge for nephron-sparing surgery [7]. fter excision of all gross tumors, hemostasis and closure of the collecting system (if required) can be managed by various methods, including surgical suture, electrocautery, laser, or various hemostatic agents such as glues [8, 9]. The parenchymal defect is then sutured or sealed by hemostatic agents. Occasionally, the parenchymal defect may be filled with adjacent fat or bioabsorbable agents as bolsters for the removal of dead space and for improved hemostasis [8]. fter the reconstruction of the kidney is finished, the vascular clamp is released to restore circulation. Characteristics of CT Findings fter Nephron-Sparing Surgery CT is the most important imaging technique in postoperative surveillance. No standard protocol exists for CT follow-up; generally, the initial CT is performed 3 6 months after surgery, and regular checkups will continue, especially in the early years [2]. n unenhanced scan should be obtained to detect the presence of enhancement in the lesion of interest. Dynamic CT is performed during the corticomedullary (early arterial) phase at seconds and the parenchymal phase at seconds W264 JR:189, November 2007

2 CT of Renal Tumors fter Nephron-Sparing Surgery Downloaded from by on 04/26/18 from IP address Copyright RRS. For personal use only; all rights reserved after contrast injection. ecause most primary and recurring RCCs show early arterial enhancement, the corticomedullary phase is important in detecting early tumoral enhancement [2]. Postoperative changes of the kidneys and retroperitoneal spaces on CT vary from patient to patient. To categorize these various postoperative changes, we classify them according to their specific CT findings. Renal Parenchymal Changes Parenchymal changes depend mainly on surgical techniques and hemostatic methods. The degree of complete repair of the vessel, the collecting system, and the parenchymal defects and the duration of the postoperative period also play a role. Postoperative granuloma Postoperative granulomas can be seen as a delayed minimally enhancing lesion at the excision site. fter the tumor is excised, parenchymal defects are closed with or without bolsters. The bolsters, such as fat and bioabsorbable agents, are spontaneously absorbed. However, they are usually visible on the initial follow-up CT images. Some degree of foreign body reaction occurs with the remaining bolsters or suture material at the excision site and may form small granulomas. previous report has shown suture foreign body granulomas mimicking renal tumors on partial nephrectomy sites [10]. This case was an unusual extensive foreign body reaction resulting in a granuloma mimicking a renal mass. Meanwhile, even in cases without the use of bolsters, postoperative granulomas can form at the excision site because of reaction to a suture material as a foreign body, a small amount of urine leakage, and bleeding. These granulomas are usually smaller than 1 cm and round or ovoid. On enhanced CT images (especially dynamic CT images), they reveal delayed minimal enhancement, a characteristic enhancement pattern of granuloma (Fig. 2). Their sizes decrease on sequential CT studies. Fat at the excision site Occasionally, fat can be seen in the surgical scar [3]. Fat is seen in the patients in whom it was used as the filling material. Fat shows as a low-density lesion at the parenchymal defect, has negative attenuation, and can be easily differentiated from tumor recurrence (Fig. 3). Linear or stellate parenchymal scar linear or stellate parenchymal scar shows a narrow and elongated linear or stellate line that runs through the renal parenchyma like a lacerated scar (Fig. 4). These scars are usually seen in patients with parenchymal closure without bolsters and may result from minimal granulation tissue at the excision site. The scar is well delineated and of low density without enhancement. The width of the scar is variable, usually measuring less than 0.3 cm, but it may be more than 0.5 cm. The size of the scar decreases on sequential CT studies. Parenchymal defect lthough the previous parenchymal changes are seen in cases of wedge, segmental, and transverse resection, parenchymal defects can be seen in cases of enucleation of an exophytic mass. Parenchymal defects are sharply demarcated defects of the renal parenchyma, primarily the cortex (Fig. 5). Usually they show no significant interval change on sequential CT studies. Other parenchymal changes Other parenchymal changes may occur that do not belong to the previous categories. If a confident diagnosis is difficult to make, close follow-up or immediate biopsy should be done to differentiate postoperative changes from early recurrence. Retroperitoneal Space Changes Postoperative changes are also noted in the retroperitoneal space. The patterns of retroperitoneal space change are mainly perinephric strands (Fig. 6), mass-like lesions (Fig. 7), or a mixture of the two (Fig. 8). mass-like lesion is defined as a lesion that shows increased attenuation in the neighboring perinephric fat, but with no significant enhancement or mass effect. These retroperitoneal postoperative findings can be considered to be part of an imaging spectrum ranging from strands to a mass-like lesion and usually show no enhancement and a decreased extent as time passes. These changes may be due to various factors, such as surgical damage, the presence of subclinical leakage of blood or urine into the perinephric space after the operation, or a degree of combined inflammation. Usually, these changes show no enhancement and are seen to a decreased extent as time passes. Postoperative retroperitoneal space changes should be differentiated from postoperative complications such as urinoma, hematoma, or abscess because postoperative complications require immediate management. In contrast to postoperative changes, urinoma, hematoma, and abscess show clinical symptoms and signs such as inflammation, infection, or bleeding. Radiologic findings of postoperative complications are also different, displaying mass effect and larger size. Local Recurrence Local recurrence occurs in two ways in the kidney treated with nephron-sparing surgery: recurrence at the surgical site and at the perinephric space. Local recurrence at the excision site should be differentiated from postoperative changes. clue for differentiation: almost all recurrences show masses at the excision site with strong enhancement on contrast-enhanced scans, especially in the corticomedullary phase (Fig. 9), and an increase in size on subsequent follow-up CT scans (Fig. 10). These findings are not seen in postoperative changes. Local tumor recurrence at the perinephric space also shows masses with strong early enhancement (Fig. 11) in contrast to postoperative changes in the retroperitoneal space, which show no enhancement. Complications Reported complication rates for nephronsparing surgery are variable, ranging from 4% to 37% [11, 12]. Complication rates can be influenced by many factors, including patient status, mass size, surgeon skill, imperative indication, and so on. Most complications can be managed by conservative methods or, at most, endoscopy or interventional radiology [11]. Commonly reported complications include urinary leak or fistula, bleeding (Fig. 12), acute renal failure, and infection (Fig. 13). These complications usually occur in the early part of the postoperative period. Other complications, including ischemic changes in the renal parenchyma (Figs. 14 and 15) and ureteral or renal pedicle stricture (Fig. 16), can be recognized on CT [3]. Conclusion Nephron-sparing surgery is becoming more popular in the treatment of renal tumors. CT is the most effective imaging technique for surveillance after this procedure. Our article shows the various postoperative changes, tumor recurrences, and complications of nephron-sparing surgery. Familiarity with these findings may help the radiologist differentiate postoperative changes from tumor recurrence or complications. References 1. Volpe, Panzarella T, Rendon R, Haider M, Kondylis FI, Jewett M. The natural history of incidentally detected small renal masses. Cancer 2004; 100: Lang EK, Thomas R, Davis R, et al. Multiphasic helical CT criteria for differentiation of recurrent neoplasm and desmoplastic reaction after laparoscopic JR:189, November 2007 W265

3 Lee et al. Downloaded from by on 04/26/18 from IP address Copyright RRS. For personal use only; all rights reserved resection of renal mass lesions. J Endourol 2004; 18: Israel GM, Hecht E, osniak M. CT and MR imaging of complications of partial nephrectomy. RadioGraphics 2006; 26: Ramani P, Ryndin I, Lynch C, Veetil RT. Current concepts in achieving renal hypothermia during laparoscopic partial nephrectomy. JU Int 2006; 97: Novick C. Partial nephrectomy. In: Sam D, Graham J, eds. Glenn s urologic surgery. Philadelphia, P: Williams & Wilkins, 2004: Porpiglia F, Fiori C, Terrone C, ollito E, Fontana D, Scarpa RM. ssessment of surgical margins in C renal cell carcinoma after nephron sparing: a comparative study laparoscopy vs open surgery. J Urol 2005; 173: Gill IS, Colombo JR Jr, Frank I, Moinzadeh, Kaouk J, Desai M. Laparoscopic partial nephrectomy for hilar tumors. J Urol 2005; 174: ; discussion Yair Lotan JC, ishoff JT. Minimally invasive, nephron-sparing interventions for renal lesions: laparoscopy and ablative techniques. In: Robert G, Moore JT, Loening S, Docimo SG, eds. Minimally invasive urologic surgery. London, UK: Taylor & Francis, 2005: Thompson T, Ng CF, Tolley D. Renal parenchymal D hemostatic aids: glues and things. Curr Opin Urol 2003; 13: Dogra PN, Tandon S, nsari MS, nupama, Chopra P. Suture foreign body granuloma masquerading as renal neoplasm. Int Urol Nephrol 2005; 37: Stephenson J, Hakimi, Snyder ME, Russo P. Complications of radical and partial nephrectomy in a large contemporary cohort. J Urol 2004; 171: Pasticier G, Timsit MO, adet L, et al. Nephronsparing surgery for renal cell carcinoma: detailed analysis of complications over a 15-year period. Eur Urol 2006; 49: Fig. 1 Techniques for nephron-sparing surgery for kidney tumors. M, Drawings illustrate segmental resection ( D), wedge resection (E G), transverse resection (H J), and enucleation (K M). (Fig. 1 continues on next page) W266 JR:189, November 2007

4 CT of Renal Tumors fter Nephron-Sparing Surgery Downloaded from by on 04/26/18 from IP address Copyright RRS. For personal use only; all rights reserved E F G H I J K L M Fig. 1 (continued) Techniques for nephron-sparing surgery for kidney tumors. M, Drawings illustrate segmental resection ( D), wedge resection (E G), transverse resection (H J), and enucleation (K M). JR:189, November 2007 W267

5 Lee et al. Downloaded from by on 04/26/18 from IP address Copyright RRS. For personal use only; all rights reserved C D Fig. 2 Round postoperative granuloma in 47-year-old woman after left nephron-sparing surgery for renal cell carcinoma., On preoperative axial corticomedullary phase CT, 3- cm-diameter solid mass (arrow) is seen in left kidney. and C, On axial corticomedullary phase () and axial parenchymal phase (C) CT performed 3 months after nephron-sparing surgery, delayed, minimally enhancing, and round postoperative granuloma is seen at excision site (arrow) in left kidney. D, On axial parenchymal phase CT performed 6 months after nephron-sparing surgery, size of round postoperative granuloma has decreased (arrow). Fig. 3 Fat at excision site in 53-year-old woman after left nephron-sparing surgery for renal cell carcinoma., On preoperative axial parenchymal phase CT, 4-cmdiameter solid mass (arrow) is seen in left kidney., On axial corticomedullary phase CT performed 3 months after nephron-sparing surgery, low-density lesion with negative CT attenuation ( 45 H) is seen at excision site (arrow), suggesting fat at excision site. Fig. 4 Linear or stellate parenchymal scar in 33-yearold man after right nephron-sparing surgery for angiomyolipoma., On preoperative axial parenchymal phase CT, large fat-containing mass (arrow) is seen in right kidney., On axial parenchymal phase CT performed 3 months after nephron-sparing surgery, 2-mm-diameter, narrow elongated linear line (arrow) that runs through renal parenchyma is seen at surgical site in right kidney. Line shows no enhancement. Fig. 5 Parenchymal defect in 44-year-old woman after right nephron-sparing surgery., On axial corticomedullary phase CT performed 4 months after nephron-sparing surgery, sharply demarcated renal parenchyma defect involving mainly cortex (arrow) is seen in right kidney., On axial parenchymal phase CT performed 14 months after nephron-sparing surgery, parenchymal defect with no significant change (arrow) is seen in surgical site. W268 JR:189, November 2007

6 CT of Renal Tumors fter Nephron-Sparing Surgery Downloaded from by on 04/26/18 from IP address Copyright RRS. For personal use only; all rights reserved Fig. 6 Perinephric strands in retroperitoneal space in 53-year-old man after nephron-sparing surgery for renal cell carcinoma., On preoperative axial parenchymal phase CT, 2-cmdiameter solid mass is seen in right kidney (arrow)., On axial corticomedullary phase CT performed 3 months after nephron-sparing surgery, linear strands are seen in retroperitoneal space (arrows). C Fig. 7 Mass-like lesion in retroperitoneal space in 65-year-old man after right nephron-sparing surgery for papillary neoplasia., On preoperative axial unenhanced CT, 1.5-cm-diameter solid mass (arrow) is seen in right kidney., On axial corticomedullary phase CT performed 6 months after nephron-sparing surgery, mass-mimicking lesion with soft-tissue density is seen in retroperitoneal space (arrow) with no enhancement or mass effect. C, On axial parenchymal phase CT performed 1 year after nephron-sparing surgery, extent of mass-like lesion has decreased (arrow). C Fig. 8 Mixture of perinephric strands and mass-like lesion in retroperitoneal space in 47-year-old man after right nephron-sparing surgery for renal cell carcinoma., On preoperative axial parenchymal phase CT, 1-cm-diameter solid mass (arrow) is seen in right kidney., On axial parenchymal phase CT performed 6 months after nephron-sparing surgery, soft-tissue-density lesion (solid arrow) with perinephric strands (dashed arrow) is seen in retroperitoneal space with no enhancement. C, On axial parenchymal phase CT performed 2 years after nephron-sparing surgery, extent of mixture of perinephric strands and mass-like lesion in retroperitoneal space has decreased. Fig. 9 Local recurrence at surgical site in 41-year-old man after right nephron-sparing surgery for renal cell carcinoma., On preoperative axial corticomedullary phase CT, 1- cm-diameter solid mass (arrow) is seen in right kidney., On axial corticomedullary phase CT performed 3 months after nephron-sparing surgery, marked enhancing recurring nodule (arrow) is seen at excision site. JR:189, November 2007 W269

7 Lee et al. Downloaded from by on 04/26/18 from IP address Copyright RRS. For personal use only; all rights reserved C Fig. 10 Local recurrence at surgical site in 56-year-old woman after right nephron-sparing surgery for renal cell carcinoma., On preoperative axial parenchymal phase CT, 1-cm-diameter solid mass (arrow) is seen in right kidney., On axial corticomedullary phase CT performed 3 months after nephron-sparing surgery, small, strongly enhancing nodule (arrow) is seen at surgical site. C, On sequential axial corticomedullary phase CT, size of enhancing nodule (arrow) has increased. Nodule was found to be local recurrence. Fig. 11 Recurrence at perinephric space in 41-yearold man after right nephron-sparing surgery for renal cell carcinoma., On preoperative axial corticomedullary phase CT, 1- cm-diameter solid mass (arrow) is seen in right kidney., On axial corticomedullary phase CT performed 3 months after nephron-sparing surgery, multiple enhancing recurrent nodules (arrows) are seen at perinephric site. C Fig. 12 In 74-year-old man, hematoma as complication after right nephron-sparing surgery for renal cell carcinoma. Gross hematuria and anemia developed 2 weeks after surgery., On preoperative axial corticomedullary phase CT, large heterogeneously enhancing solid mass (arrow) is seen in right kidney., On axial unenhanced CT performed 2 weeks after nephron-sparing surgery, homogeneous mass (arrows) with attenuation of 70 H is seen around surgical clips. C, Coronal reformatted unenhanced CT also shows hyperattenuated mass, which is consistent with hematoma at surgical site (arrows). C Fig. 13 bscess as complication of nephron-sparing surgery in 66-year-old man after right nephron-sparing surgery., On preoperative axial parenchymal phase CT, 1.5-cm-diameter solid mass (arrow) is seen in right kidney., On axial parenchymal phase CT performed 2 weeks after nephron-sparing surgery, loculated fluid collection with thick enhancing wall (arrows) is seen at anterior pararenal space. This was found to be abscess. C, On axial parenchymal phase CT performed 3 months after nephron-sparing surgery, postoperative abscess has disappeared. W270 JR:189, November 2007

8 CT of Renal Tumors fter Nephron-Sparing Surgery Downloaded from by on 04/26/18 from IP address Copyright RRS. For personal use only; all rights reserved C Fig. 14 Ischemia as complication of nephron-sparing surgery in 39-year-old woman after left nephron-sparing surgery for cystic renal cell carcinoma., On preoperative axial corticomedullary phase CT, cystic mass with enhancing thick septa (arrow) is seen in left kidney., On axial parenchymal phase CT performed 1 year after nephron-sparing surgery, parenchyma at surgical site shows decreased enhancement and mild atrophied change (arrow) in comparison with remnant renal parenchyma. C, On coronal reformatted parenchymal phase CT, ischemic change is also seen at surgical site (arrow). Change was regarded as postoperative ischemia. Fig. 15 nother case of ischemia in 45-year-old man after right nephron-sparing surgery for renal cell carcinoma. On coronal reformatted parenchymal phase CT, right kidney shows atrophied change and lack of parenchymal enhancement. Fig. 16 Ureteral or renal pedicle stricture as complication of nephron-sparing surgery in 55-year-old woman after left nephron-sparing surgery for renal cell carcinoma., On preoperative coronal reformatted parenchymal phase CT, 3-cm-diameter solid mass (arrow) is seen in left kidney., On axial parenchymal phase CT performed 1 year after nephron-sparing surgery, renal vascular luminal narrowing (arrow) and hydronephrosis with parenchymal atrophy are seen, suggesting ureteral or renal pedicle stricture. JR:189, November 2007 W271