Enhanced computed tomography after partial nephrectomy in early postoperative period to detect asymptomatic renal artery pseudoaneurysm

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1 bs_bs_banner International Journal of Urology (2014) 21, doi: /iju Original Article: Clinical Investigation Enhanced computed tomography after partial nephrectomy in early postoperative period to detect asymptomatic renal artery pseudoaneurysm Toshio Takagi, 1 Tsunenori Kondo, 1 Tsuyoshi Tajima, 2 Steven C Campbell 3 and Kazunari Tanabe 1 Departments of 1 Urology and 2 Diagnostic Imaging and Nuclear Medicine, Tokyo Women s Medical University Hospital, Tokyo, Japan; and 3 Glickman Urological and Kidney Institute, Cleveland Clinic, Cleveland, Ohio, USA Abbreviations & Acronyms ASA = American Society of Anestheologists CT = computed tomography EBL = estimated blood loss egfr = estimated glomerular filtration rate LOS = length of stay MIS = minimally-invasive surgery PN = partial nephrectomy POD = postoperative day RAP = renal artery pseudoaneurysm RENAL = (R)adius (tumor size as maximal diameter), (E)xophytic/endophytic properties of tumor, (N)earness of tumor deepest portion to collecting system or sinus, (A)nterior (a)/posterior (p) descriptor and (L)ocation relative to polar line TAE = transarterial embolization Correspondence: Toshio Takagi M.D., Department of Urology, Tokyo Women s Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo , Japan. himmeno1192@yahoo.co.jp Received 24 October 2013; accepted 10 March Online publication 8 April 2014 Objectives: We systematically examined the incidence and potential implications of renal artery pseudoaneurysm occurring after partial nephrectomy detected by computed tomography screening in the early postoperative period. Methods: Between January and December 2012, 117 patients underwent enhanced screening computed tomography on the fourth postoperative day after partial nephrectomy to evaluate for renal artery pseudoaneurysm. The size of the renal artery pseudoaneurysm and follow-up imaging were utilized to decide on pre-emptive angioembolization. Patient characteristics, tumor specifics and surgical data were analyzed. Results: A total of 17 of 117 patients (15%) were found to have renal artery pseudoaneurysm on early postoperative computed tomography. Renal artery pseudoaneurysm occurred in nine of 73 open partial nephrectomy patients (12.3%) and eight of 44 laparoscopic partial nephrectomy patients (18.2%). One early patient experienced a postoperative bleed on postoperative day 9 after diagnosis of a 3.5-mm diameter renal artery pseudoaneurysm on postoperative day 3, and this patient was successfully managed with angioembolization. There were no other postoperative bleeding episodes. Rapid growth of a renal artery pseudoaneurysm was observed in a second patient who was treated with pre-emptive angioembolization. Five patients were diagnosed with small renal artery pseudoaneurysm (2 4 mm) on postoperative day 4 and observed with follow-up imaging showing resolution of the renal artery pseudoaneurysm. Another 10 patients were diagnosed with larger renal artery pseudoaneurysm ( 4 mm) and were managed with preemptive angioembolization. Conclusions: Early postoperative computed tomography screening is able to detect modest rates of asymptomatic renal artery pseudoaneurysm. The rate of postoperative bleed remained low with a policy of selective angioembolization. Renal artery pseudoaneurysm size and interval enlargement might indicate the risk of rupture. Further studies are required to assess the potential role of pre-emptive angioembolization. Key words: computed tomography, kidney neoplasm, nephrectomy, postoperative bleed, pseudoaneurysm. Introduction PN has been strongly advocated as the treatment of choice for small renal masses with equivalent oncological outcomes and better preservation of renal function. 1 5 Recent guidelines establish PN as the reference standard for clinical T1a renal tumors. 6 More recently, the indications for elective PN have been expanded to larger tumors, such as clinical T1b and T2a, in carefully selected patients. 7 PN for small renal masses is carried out by several techniques including open, laparoscopic and robot-assisted approaches depending on individual tumor characteristics, surgeon experience or institutional factors. The main advantage of PN is preservation of renal function, but PN is a more challenging procedure with slightly higher morbidity than radical nephrectomy PN yields a reconstructed kidney that must heal, and can be associated with postoperative bleeding or urinary fistula. The incidence of postoperative bleeding in most PN series ranges from approximately 1 3%, and typically occurs in the first 14 days after surgery. 11 The most common etiology appears to be RAP, although arteriovenous fistula has also been described. 11 At the Tokyo Women s Medical University Hospital, Tokyo, Japan, five of 434 patients (1.2%) who underwent PN between 2005 and 2011 developed symptomatic RAP The Japanese Urological Association

2 High incidence of asymptomatic RAP after PN Over the past 12 months, we have investigated the potential role of CT to screen for early postoperative complications, including RAP. Herein we report the incidence of RAP based on this screening policy, and discuss potential implications for management. Methods Patients An institutional review board-approved retrospective review was carried out of 160 consecutive patients who underwent PN at Tokyo Women s Medical University Hospital between January 2012 and December Patients who could not undergo enhanced CT as a result of an allergic reaction to the contrast agent, impaired kidney function or severe asthma were excluded from the present study. In total, 117 patients underwent screening CT, all on POD 3 5, most commonly on POD 4. CT technique Patients received 3-D dynamic enhanced CT for screening for RAP. Three-dimensional helical CT imaging was carried out using a 64-row multidetector CT scanner in a craniocaudal direction during one-breath-hold helical acquisition. Collimation was 0.5 mm and CT pitch was Non-ionic contrast agent was administered at mg/kg, and the injection rate was ml/s. Bolus tracking was carried out s after the start of injection. The arterial phase was initiated 10 s after the triggering level of the abdominal aorta reached +100 HU. CT analyses CT data were reformatted into 3-D images including multiplanar reconstruction and 50-mm-slab thicknessmaximum intensity projection using the online workstations. Two experienced abdominal radiologists (TT, MK), who had no knowledge of the surgical or clinical results, independently reviewed axial images (1 mm and 5 mm) and discretional crosssectional images (0.5-mm-multiplanar reconstruction image, 50-mm- maximum intensity projection images), and assessed the vascular complications, such as RAP, irregularity of renal arteries and contrast extravasation. RAP was defined as a saccular- or fusiform-shaped dilatation of the renal arterial branches compared with the surrounding normal renal arterial branches. Potential RAP smaller than 2 mm in diameter were excluded because of limitations, such as slice-related pseudolesion or possibility of renal artery stump dilation. Disagreement of interpretation was resolved by consensus. Therapeutic strategy for renal artery pseudoaneurysm Patients diagnosed with large RAP (>4 mm diameter) underwent pre-emptive TAE, based on previous experience with rapid growth and instability of RAP >4 mm, we used 4 mm as a cut off for pre-emptive intervention. Patients diagnosed with small RAP (2 4 mm) underwent repeat enhanced 3-D CT within 15 days after the first 3-D CT. Enlarging RAP were also treated with TAE. Surgery For open PN, a flank incision was made at the 11th rib to approach the kidney extraperitoneally. The kidney was mobilized within Gerota s fascia, except for the perirenal fat around the tumor. The renal artery and vein were then clamped en bloc (Satinsky clamp) at the renal hilum and ice slush was placed around the kidney. Transected branch arteries and veins at the parenchymal margin were ligated using 4-0 non-absorbable sutures. The opened collecting system was repaired using 4-0 absorbable sutures. In approximately 50% of cases, hemorrhagic areas on the surface of renal parenchyma were ligated using 4-0 absorbable sutures, and the renal capsule was reapproximated using 1 or 2-0 absorbable sutures with the resection bed stuffed with oxidized cellulose (Surgicel; Ethicon, Somerville, NJ, USA). In the other cases, hemorrhagic areas on the surface of the renal parenchyma were coagulated by monopolar soft-coagulation (SOFT COAG, VIO 300D; ERBE Elektromedizin, Tubingen, Germany). TachoSil tissue sealing sheet (CSL Behring Japan, Tokyo, Japan) was placed on the surface of the parenchymal incision and compressed for 5-min immediately after unclamping the renal hilum without renal capsule closure. The choice of these two hemostatic approaches was dependent on each surgeon. For laparoscopic procedures, en bloc clamping of the renal hilum was applied for all transabdominal cases. Six laparoscopic procedures were carried out by a retroperitoneal approach, and separate bulldog clamps were utilized for the artery and vein in all of these instances. In the setting of laparoscopic surgery, renorrhaphy is carried out in one or two layers, which is dependent on the depth of tumors. A 2-0 absorbable suture with a knot and Hem-o-Lok Clip (Teleflex Medical, Kenosha, WI, USA) applied to the free end was used as running suture of the tumor excision bed to ligate larger vessels, as well as entries into the collecting system. The suture was brought through the renal capsule with the final throw and secured with two sliding Hem-o-Lok clips. The renal capsule was reapproximated using a continuous 2-0 absorbable suture with the resection bed stuffed with oxidized cellulose. Statistical analysis Estimations of surgical blood loss and percentage of preserved renal parenchyma were recorded at case completion. Intraoperative visual estimation of the preserved renal parenchyma was based on a consensus between the surgeon and the assistant. Tumor complexity was defined by the RENAL-NS. 12 Radiographic tumor size was utilized for all analyses as determined by CT. All statistical analyses were carried out using the JMP software (SAS Institute, Cary, NC, USA). Quantitative parameters were compared using the Mann Whitney U-test, and qualitative parameters were compared using Fisher s exact test. P-values of less than 0.05 were considered to show statistical significance. Results Table 1 provides patient characteristics for the total cohort, which appears to be representative of conventional PN populations. The mean age of patients at surgery was 56 years, and 73% were male. The mean preoperative egfr was 74.6 ml/ 2014 The Japanese Urological Association 881

3 T TAKAGI ET AL. Table 1 Patient characteristics No. patients (n) 117 Pseudoaneurysm, n (%) 17 (15) Mean age, years (median, range) 56 (56, 26 82) Mean body mass index, kg/m 2 (range) 23.9, (23.3, ) Sex, n (%) Male 85 (73) Female 32 (27) Mean preoperative egfr, ml/min/m (73.5, ) (median, range) ASA score, n (%) 1 24 (21) 2 84 (72) 3 9 (7) RENAL nephrometry score, n (%) Total (35) (45) (20) Mean surgery time, min (median, range) 200 (202, ) Surgical approach, n (%) Open 73 (62) Laparoscopic 44 (38) Mean total ischemia time, min (median, range) 36.0 (32, 5 76) Ischemia method, n (%) Cold 77 (66) Warm 40 (34) Hilum clamp, n (%) En bloc 111 (95) Separate 6 (5) Mean EBL, ml (range) 133 (60, ) Patients transfused, n (%) 2 (2) Median length of stay, days (range) 5 (4 28) Pathological, n (%) Renal cell carcinoma 105 (90) Benign lesion 12 (10) Parenchymal suture, n (%) Yes 71 (61) No 46 (39) min/m 2 (range ml/min/m 2 ). The mean body mass index was 23.9 kg/m 2. RENAL nephrometry score distribution included 35% with low complexity, 45% with intermediate complexity and 20% with high complexity. A total of 25% of tumors were more than 4 cm in diameter, and 58% invaded, touched and/or approached within 4 mm of the sinus or collecting system. A total of 68% of tumors were endophytic (exophytic/endophytic factor = 2 3 by RENAL classification), and 46% of tumors were located in the central portion of the kidney. A total of 73 patients (62%) underwent open surgery. Parenchymal suturing was carried out in 71 patients (61%), including all MIS cases. A total of 105 patients (90%) were diagnosed with malignancy after pathological examination. A total of 17 of 117 patients (15%) were diagnosed with RAP by screening CT on POD 3 5 (Table 2). RAP occurred in nine of 73 open PN patients (12.3%) and eight of 44 laparoscopic PN patients (18.2%; P = 0.38). Two of 23 patients (8.6%) with high complexity tumors (RENAL nephrometry score 10 12) were diagnosed with RAP, as were eight of 53 patients (15.1%) with intermediate complexity tumors (score 7 9) and seven of 41 patients (17.0%) with low complexity tumors (score 4 6; Table 2 Patient characteristics and treatment for RAP Symptom Treatment Diameter of RAP on POD 6 19 Nephrometry score Hilum clamp Diameter of RAP on POD 3-5 Patient Age Sex Surgery Laterality Tumor size (mm) Total R E N L 1 61 Male Open Right En bloc 3.5 mm 29 mm Hematuria TAE 2 26 Female Open Left En bloc 2.9 mm 6.8 mm No TAE 3 57 Male Open Right En bloc 3 mm Undetected No Observation 4 43 Female MIS Right En bloc 3.5 mm Undetected No Observation 5 51 Male MIS Left En bloc 3 mm Undetected No Observation 6 57 Male Open Left En bloc 2.5 mm Undetected No Observation 7 71 Female Open Right En bloc 2.5 mm Undetected No Observation 8 72 Male open Left En bloc 7 mm No TAE 9 54 Male Open Left En bloc 8.8 mm No TAE Male MIS Right En bloc 5 mm No TAE Female MIS Right Separate 4 mm No TAE Male MIS Left En bloc 4 mm No TAE Male Open Left En bloc 5 mm No TAE Male Open Left En bloc 9.3 mm No TAE Male MIS Left En bloc 10 mm No TAE Female MIS Left En bloc 6 mm, 3 mm No TAE Female MIS Right En bloc 9 mm x 2 No TAE The Japanese Urological Association

4 High incidence of asymptomatic RAP after PN (a) (b) (c) (d) Fig. 1 RAP that ruptured identified by screening CT (patient 1). (a) Screening dynamic CT on POD3 after partial nephrectomy showed a small (3.5 mm) RAP. (b) CT on POD 9 after hemorrhagic symptoms shows interval growth of the RAP to 29 mm. (c) Angiography shows extravasated contrast from a renal artery branch, consistent with ruptured RAP. (d) Angiography confirms successful obliteration of the RAP. (a) (b) (c) (d) Fig. 2 RAP shown by screening CT with interval growth and pre-emptive angioembolization (patient 2). (a) Screening dynamic CT on POD 4 after partial nephrectomy shows a small (2.9 mm) RAP. (b) Follow-up CT on POD 7 shows interval growth of the RAP to 6.8 mm. (c) Angiography confirms a complex RAP, and pre-emptive angioembolization was carried out. (d) Angiography confirms successful obliteration of the RAP. P = 0.47). In general, a MIS approach was mostly applied for the low and intermediate complexity cases, and this appeared to correlate with a higher incidence of RAP in these subgroups, although this did not reach statistical significance. All 23 high complexity tumors were removed through an open approach, whereas MIS was applied for 16/53 (30%) intermediate complexity tumors and 28/41 (68%) of low complexity tumors. A total of 16 of 111 patients (14%) with en bloc hilar clamping had RAP, whereas one of six patients (17%) with separate hilar clamping had RAP (P = 0.88). RAP occurred in 13 of 71 patients (18%) with parenchymal suturing and four of 46 patients (9%) without parenchymal suturing (P = 0.15). One early patient (patient 1; Table 2) was diagnosed with a 3.5-mm RAP on POD3, and then developed gross hematuria and ipsilateral flank pain on POD9. Urgent CT confirmed a markedly enlarged RAP (29-mm diameter) with active bleeding, and angioembolization was successfully carried out (Fig. 1). Subsequent to this, a more proactive approach was used (Table 2), with a policy of pre-emptive angioembolization for all moderate-to-large ( 4 mm) RAP or for those showing interval growth (Fig. 2). There were no complications related to pre-emptive embolization, and all such procedures were successful as assessed by postprocedure angiography. Five small RAP (<4 mm) were observed, and all appeared to resolve on interval imaging (Table 2). There were no additional bleeding episodes. There were no notable differences in perioperative parameters between patients with spontaneous resolution of RAP versus those with enlargement or bleeding of RAP, including estimated blood loss, operation time and postoperative laboratory findings. Discussion RAP after PN is an uncommon, but potentially devastating, complication. Incidence rates of RAP have ranged from 1% to 5% based on previous reports, 11,13 18 with most studies reporting an increased incidence after MIS approaches, although the learning curve appears to be a contributing factor. For instance, Netsch et al. reported four RAP out of 289 (1.4%) after open PN, compared with four out of 40 (10%) after laparoscopic PN. 13 Similarly, Ghoneim et al. reported seven RAP after 1160 (0.6%) open PN versus eight RAP after 301 (2.6%) laparoscopic PN. 11 More recent series suggest lower rates of RAP after minimally-invasive PN primarily related to 2014 The Japanese Urological Association 883

5 T TAKAGI ET AL. increased surgeon experience. For instance, Gill et al. have reported a two to threefold reduction in the incidence rates of RAP or postoperative bleeding with further experience and with modifications of their technique, including the introduction of robotic technology. 19,20 In our hospital, between 2005 and 2011, five of 434 (1.2%) patients who underwent PN developed RAP, including four symptomatic patients and one asymptomatic patient. The median time of presentation after PN was 9 days, consistent with the delayed pattern of presentation observed in most other studies. Our incidence of clinical RAP thus appears to be representative for this literature. For academic reasons, and with consideration of the potential implications of a postoperative bleeding episode, we elected to carry out an institutional review board-approved screening CT study after PN during the calendar year 2012 for all patients without relative or absolute contraindications to administration of intravenous contrast. In this series, we observed a total of 17 RAP after 117 PN (15%) based on screening CT on POD 3 5. This incidence is much greater than previous reports, suggesting that most of such lesions were destined to remain asymptomatic. In addition, five small RAP (2 3.5 mm) in this series could not be reliably confirmed on follow-up imaging, suggesting possible false positive diagnoses, despite two independent reviews of the initial studies. Another potential explanation of this finding is spontaneous resolution related to interval healing. Clot formation could seal off the defective portion of the artery and initiate a healing phase. Hyams et al. also reported two patients with spontaneous radiographic resolution of RAP during inpatient monitoring. Both of their patients were symptomatic at presentation, so this appears to be a real phenomenon. 14 Interval expansion of RAP was observed in two patients in the present series, one of whom bled on POD 9 mandating angioembolization. A second patient was embolized pre-emptively after interval growth was observed. Beyond this, all moderate-tolarge ( 4 mm) RAP were pre-emptively embolized, and no further bleeding episodes were observed. Although the precise etiology of RAP is unknown, it is thought to arise from a transected or punctured branch artery that leaks into a contained hematoma cavity. Transected branch arteries can retract away from the field and go into spasm, and thus cannot be adequately visualized and addressed intraoperatively. Alternatively, suture ligation might paradoxically destabilize the branch artery, predisposing to subsequent rupture. Either way, presentation is often delayed until the patient increases activity, typically occurring a few to several days after surgery. To reduce the risk of RAP, a variety of maneuvers can be considered. The traditional approach has been to pursue adequate hemostasis of the resection bed by careful identification and suturing of all substantial transected vessels, which can be facilitated by removing the venous clamp and carrying out a Valsalva maneuver. Hemostatic agents might also be helpful, although their true value has never been adequately established. For MIS procedures, careful inspection of the field after deflation of the abdomen should be routinely carried out. Risk factors for RAP after PN are not well defined, although central tumor location and en bloc clamping of the renal hilum have been proposed as potential predisposing factors. In the present series, the great majority of cases (95%) were carried out utilizing en bloc clamping, and a meaningful comparison of these cases with those that were performed with individualized clamping could not be carried out. Several series suggested that central location or high RENAL scores correlate with major urological complications including postoperative bleeding. For instance, Nadu et al. reported a 7.5% (4/53) incidence of RAP after PN for central tumors, whereas none of the 159 patients with peripheral tumors had RAP. 21 In the present series, the impact of RENAL or central tumor location was difficult to evaluate because of differences in patient selection for open versus MIS approaches. MIS surgery correlated with a trend towards increased incidence for RAP after PN in our series, but this did not reach statistical significance, and might relate to the learning curve, as aforementioned. The present study is the first to report the results of screening for RAP by enhanced CT in the early postoperative period, and although the findings are interesting, the true utility of this approach remains to be determined. As shown by the discussion of risk factors for RAP, at-risk populations for such screening efforts are not particularly well defined. In addition, potential indications for pre-emptive embolization will also require further study, and it is important to recognize that this procedure is not free of potential complications, which can include renal artery dissection, post-embolization syndrome 22 and additional loss of renal function. 23 Other risks of CT and embolization, such as radiation exposure and contrast-induced acute kidney injury, should also be considered. The effective radiation dose for multiphase abdomen/pelvic CT is reportedly 31 msv, 24 and 5 70 msv for interventional radiological procedures. 25 Increased awareness of the oncological risks of radiation exposure tempers enthusiasm for such studies until proven to be beneficial. Contrast-induced acute kidney injury is the third leading cause of hospital-acquired acute renal failure, 26 and is recognized as a significant contributor to in-hospital morbidity and mortality. Fiscal issues are another consideration, because 3-D CT costs more than $300 in Japan, and is much more expensive in many other countries. Nevertheless, selective screening might still make sense in certain situations, such as particularly challenging PN for hilar tumors, or whenever there is concern about the quality of the capsule that is available for closure. Other high-risk patients might include those requiring reinstitution of anticoagulant therapy shortly after PN, for whom the risk of bleeding is likely increased. In all of these instances, clinical judgment will remain of paramount importance, recognizing the need for higher quality data about this issue. Like all studies, the present study had a variety of limitations, including its retrospective nature, and the somewhat arbitrary cut-points that were utilized for decisions about pre-emptive embolization. Furthermore, patients who could not undergo enhanced CT because of a history of allergic reaction to intravenous contrast, impaired kidney function or severe asthma were excluded from the present study. Therefore, our data might not apply to all patients undergoing PN, particularly patients with such characteristics. Although our study defines a high rate of asymptomatic RAP, the clinical implications of these lesions will require further study, and management strategies and implications for screening efforts remain incompletely defined The Japanese Urological Association

6 bs_bs_banner High incidence of asymptomatic RAP after PN In conclusion, CT screening in the early postoperative period after PN showed a high incidence of asymptomatic RAP. Most patients should not be considered for routine postoperative CT because of radiation exposure and cost, but this might be of utility in high-risk situations. Further study will be required to determine target populations at risk for RAP that might benefit from screening, and the potential role of pre-emptive angioembolization. Acknowledgments The authors thank Ms Elizabeth Kiritani for English language assistance with the preparation of the manuscript. We also thank Dr Kenji Omae, Dr Kazuhiko Yoshida and Ms Nobuko Hata for arranging the database. Conflict of interest None declared. References 1 Lee CT, Katz J, Shi W, Thaler HT, Reuter VE, Russo P. Surgical management of renal tumors 4 cm. or less in a contemporary cohort. J. Urol. 2000; 163: Lane BR, Babineau DC, Poggio ED et al. Factors predicting renal functional outcome after partial nephrectomy. J. Urol. 2008; 180: ; discussion Lau WK, Blute ML, Weaver AL, Torres VE, Zincke H. Matched comparison of radical nephrectomy vs nephron-sparing surgery in patients with unilateral renal cell carcinoma and a normal contralateral kidney. Mayo Clin. Proc. 2000; 75: McKiernan J, Simmons R, Katz J, Russo P. Natural history of chronic renal insufficiency after partial and radical nephrectomy. Urology 2002; 59: Thompson RH, Frank I, Lohse CM et al. The impact of ischemia time during open nephron sparing surgery on solitary kidneys: a multi-institutional study. J. Urol. 2007; 177: Novick AC, Campbell SC, Belldegrun A. Guideline for Management of the Clinical Stage 1 Renal Mass. American Urological Association Education and Research, Linthicum, MD, Thompson RH, Siddiqui S, Lohse CM, Leibovich BC, Russo P, Blute ML. Partial versus radical nephrectomy for 4 to 7 cm renal cortical tumors. J. Urol. 2009; 182: Van Poppel H, Da Pozzo L, Albrecht W et al. A prospective, randomised EORTC intergroup phase 3 study comparing the oncologic outcome of elective nephron-sparing surgery and radical nephrectomy for low-stage renal cell carcinoma. Eur. Urol. 2011; 59: Pasticier G, Timsit MO, Badet L et al. Nephron-sparing surgery for renal cell carcinoma: detailed analysis of complications over a 15-year period. Eur. Urol. 2006; 49: Touijer K, Jacqmin D, Kavoussi LR et al. The expanding role of partial nephrectomy: a critical analysis of indications, results, and complications. Eur. Urol. 2010; 57: Ghoneim TP, Thornton RH, Solomon SB, Adamy A, Favaretto RL, Russo P. Selective arterial embolization for pseudoaneurysms and arteriovenous fistula of renal artery branches following partial nephrectomy. J. Urol. 2011; 185: Kutikov A, Uzzo RG. The R.E.N.A.L. nephrometry score: a comprehensive standardized system for quantitating renal tumor size, location and depth. J. Urol. 2009; 182: Netsch C, Brüning R, Bach T, Gross AJ. Management of renal artery pseudoaneurysm after partial nephrectomy. WorldJ.Urol.2010; 28: Hyams ES, Pierorazio P, Proteek O et al. Iatrogenic vascular lesions after minimally invasive partial nephrectomy: a multi-institutional study of clinical and renal functional outcomes. Urology 2011; 78: Shapiro EY, Hakimi AA, Hyams ES, Cynamon J, Stifelman M, Ghavamian R. Renal artery pseudoaneurysm following laparoscopic partial nephrectomy. Urology 2009; 74: Singh D, Gill IS. Renal artery pseudoaneurysm following laparoscopic partial nephrectomy. J. Urol. 2005; 174: Jain S, Nyirenda T, Yates J, Munver R. Incidence of renal artery pseudoaneurysm following open and minimally invasive partial nephrectomy: a systematic review and comparative analysis. J. Urol. 2013; 189: Albani JM, Novick AC. Renal artery pseudoaneurysm after partial nephrectomy: three case reports and a literature review. 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Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer. Arch. Intern. Med. 2009; 169: Mettler FA, Huda W, Yoshizumi TT, Mahesh M. Effective doses in radiology and diagnostic nuclear medicine: a catalog. Radiology 2008; 248: Nash K, Hafeez A, Hou S. Hospital-acquired renal insufficiency. Am. J. Kidney Dis. 2002; 39: Editorial Comment Editorial Comment to Enhanced computed tomography after partial nephrectomy in early postoperative period to detect asymptomatic renal artery pseudoaneurysm Takagi et al. have presented a very informative article regarding the use of contrast-enhanced computed tomography (CT) scan after partial nephrectomy (PN) as a means of detecting renal artery pseudoaneurysm (RAP). 1 This study seems to be the only one of its kind and presents very interesting data. Based on their patient population, approximately 15% of patients after PN (open or minimally invasive) were diagnosed with a RAP by screening CT scan carried out between postoperative days 3 5. Of these, only one patient of the 17 was symptomatic. This incidence is much higher than what we found in our metaanalysis, 2 which was limited to symptomatic patients only. The article affirms what many of us believe: RAP are more common in incidence than they are symptomatic. It also is one of the first to show that observation is a reasonable option for patients with RAP after PN. However, it leaves some very important, unanswered questions. What is the optimal RAP size to allow for observation versus intervention in this patient population? The cut-off of >4 mm that Takagi et al. used was 2014 The Japanese Urological Association 885