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Evaluation of Crossing Vessels in Patients with Ureteropelvic Junction Obstruction by Means of Helical CT¹

¹ From the Department of Radiology, Himeji Red Cross Hospital, 5-30-1 Tatsuno-cho, Himeji City, Hyogo 670-8540, Japan (A.M.); and the Departments of Radiology (K.Y., S.A., I.T., I.J., Y.H.) and Urology (H.H., H.K.), Okayama University Medical School, Japan. Presented as a scientific exhibit at the 1998 RSNA scientific assembly. Received January 27, 1999; revision requested May 11; final revision received December 10; accepted December 13. Address correspondence to A.M.

	Abstract

Top Abstract Introduction Materials and Methods Results and Discussion Conclusions References

 
Helical computed tomography (CT) was used to demonstrate the distribution of crossing vessels in patients with ureteropelvic junction (UPJ) obstruction for planning surgical management. Twenty patients with symptomatic UPJ obstruction were evaluated with dual-phase contrast material–enhanced helical CT. In addition to axial images, coronal, sagittal, and curved paracoronal images along the crossing vessels or the UPJ were obtained by means of multiplanar reconstruction. Crossing vessels were evaluated according to type, position, and association with UPJ obstruction. Fifteen vessels in 12 of the 20 patients were found to cross the UPJ at helical CT. Nine vessels were arteries and six were veins; seven vessels crossed anteriorly and eight crossed posteriorly. In 11 patients, crossing vessels were thought to be associated with UPJ obstruction at helical CT; retroperitoneoscopic repair was performed, and the diagnosis was found to have been accurate in all except one. In the eight patients in whom no significant vessels were seen and the one patient in whom the crossing vessel was not associated with UPJ obstruction at helical CT, endopyelotomy was performed and UPJ obstruction was relieved, with no complications. Helical CT is useful for evaluation of vessels crossing the UPJ and for planning surgical management.

Index Terms: Computed tomography (CT), helical, 821.12115 • Renal arteries, 96.134 • Renal veins, 96.134 • Ureter, stenosis or obstruction, 821.842

	Introduction

Top Abstract Introduction Materials and Methods Results and Discussion Conclusions References

 
Ureteropelvic junction (UPJ) obstruction may be attributable to intrinsic or extrinsic causes. In the pediatric population, intrinsic pelviureteral abnormalities are thought to be the source of most cases of UPJ obstruction. A combination of defects in muscular arrangement, excessive collagen deposition, and abnormal intercellular conduction have been implicated in the usual form of intrinsic UPJ obstruction. Factors associated with extrinsic UPJ obstruction have included fixed kinks or angulations, bands of tissue, and high insertions of the ureter on the renal pelvis. Causes of secondary UPJ obstruction include infection, stones, surgery, ischemia, and iatrogenic injury.

The functional significance of crossing vessels at the location of UPJ obstruction is controversial. According to some reports, although crossing vessels have been implicated as the cause of UPJ obstruction, they more commonly aggravate rather than produce the obstruction (1,2). Van Cangh et al (3) reported that crossing vessels had a statistically significant negative effect on the outcome of endoureteropyelotomy, reducing the success rate from 82% to 33%. Conversely, Sampaio and Favorito (4) found incidental vessels at the UPJ in more than 70% of patients without UPJ obstruction, whereas approximately 44% of patients with UPJ obstruction had vessels crossing the UPJ. Nakada et al (5) detected significant crossing vessels with helical computed tomography (CT) in 38% of patients after successful endopyelotomy. Gupta and Smith (6) reported that the presence of a crossing vessel was potentially causally related to endopyelotomy failure in less than 4% of patients undergoing the procedure and concluded that the finding of crossing vessels before surgery need not significantly affect the treatment given. They recommended that a distinction be made between crossing vessels that appear to be incidental and those that appear to cause obstruction; however, they stated that no imaging technique currently available allows one to determine whether a vessel is obstructing the UPJ or is an incidental finding. If incidental crossing vessels and crossing vessels causing obstruction could be distinguished before surgery and treatment selected according to the results of preoperative diagnostic imaging, the success rate of endopyelotomy might be increased.

Owing to advances in CT hardware, high-speed helical CT can be performed and extensive anatomic regions can be scanned during a single breath hold (7–9). Therefore, high-quality images can be generated in combination with dynamic examination. Such examinations have been used to evaluate the vasculature of all regions of the body (10–14). The purpose of this study was to demonstrate the distribution of crossing vessels in patients with UPJ obstruction and to attempt to distinguish between crossing vessels associated with UPJ obstruction and incidental crossing vessels by means of helical CT for surgical planning and management.

	Materials and Methods

Top Abstract Introduction Materials and Methods Results and Discussion Conclusions References

 
Patient Population
Between October 1996 and March 1998, we evaluated 20 patients with symptomatic UPJ obstruction by using dual-phase contrast material–enhanced helical CT. Nine male patients and 11 female patients aged 5–67 years (mean, 37 years) were included in the study. All patients were identified as eligible for the study during the initial consultation, and no patients had indwelling ureteral stents or percutaneous nephrostomy catheters at the time of helical CT.

Image Acquisition
Nonenhanced helical CT of the entire kidney was performed with a HiSpeed Advantage scanner (GE Medical Systems, Milwaukee, Wis) to identify the level of the UPJ. This acquisition was performed with 10-mm collimation at 10-mm intervals during a single breath hold. Then, 100 mL of iohexol (Omnipaque 300; Daiichi Pharmaceutical, Tokyo, Japan) was injected via an antecubital vein at 2.5 mL/sec. Contrast-enhanced helical CT was performed two times during a 20–30-second breath hold after the start of injection with 3-mm collimation and a pitch of 1–1.3; a section at the level of the UPJ was set as the center of the scanning range. The first scan was begun 25 seconds and the second scan 90 seconds after the start of injection. The reconstruction interval was 1 mm.

All imaging data were viewed and interpreted prospectively on an imaging workstation (Advantage Windows; GE Medical Systems). In addition to axial images, coronal, sagittal, and curved reconstruction images along the crossing vessels or the UPJ were obtained by means of multiplanar reconstruction. Reconstructed images were displayed as multiplanar reconstruction images, not as three-dimensional rendered images. Three-dimensional image display has a number of disadvantages. With shaded-surface display of three-dimensional rendered images, high-attenuation objects within the images cannot be differentiated and the UPJ is not demonstrated (15). Moreover, when a crossing vessel is very small, clear visualization of the vessel with shaded-surface display is difficult. Conversely, multiplanar reconstruction images can clearly demonstrate a crossing vessel even when it is very small. Because the cost of implementing volume-rendering software is high (15), this technique is not suitable for every institution. In general, much time and work are required to edit the images after examination. We believe that three-dimensional image display is useful for allowing the operator to readily understand the relationships between the UPJ and crossing vessels. However, routine use of this method may be difficult at some institutions. Conversely, multiplanar reconstruction can be performed more quickly and easily and is suitable for evaluation of crossing vessels in cases of UPJ obstruction; thus, many institutions may find this method preferable for routine use.

Evaluation of Crossing Vessels
Evaluation of crossing vessels was based on the following four factors: (a) the presence of a crossing vessel along the UPJ; (b) the type of vessel (artery, vein, or both); (c) the position of the crossing vessel (anterior or posterior, medial or lateral); and (d) whether the crossing vessel was associated with UPJ obstruction. When the crossing vessel was in contact with the most stenotic point of the UPJ, we suspected that the crossing vessel was associated with UPJ obstruction. In addition to this finding, compression or deviation of the UPJ by the crossing vessel was considered supportive evidence for an association with UPJ obstruction.

	Results and Discussion

Top Abstract Introduction Materials and Methods Results and Discussion Conclusions References

 
Pyelography can demonstrate UPJ obstruction, but no information is obtained concerning crossing vessels. Angiography can demonstrate both the UPJ and crossing vessels, but information on the anatomic location of a crossing vessel is insufficient and the crossing vessel is not well demonstrated when it is a small vein. Conversely, helical CT is noninvasive and all of the required information about the presence, type (artery or vein), and anatomic location of crossing vessels in patients with UPJ obstruction can be obtained with dual-phase contrast-enhanced examination. Moreover, the appropriate treatment can be determined based on the results of this examination.

Types of Crossing Vessels
Fifteen vessels in 12 of the 20 patients were found to cross the UPJ at helical CT (Table 1). The diameter of the crossing vessels was 1–6 mm. In two cases, the crossing vessels were less than 2 mm in diameter. Nine vessels were arteries and six were veins; seven vessels crossed anteriorly and eight crossed posteriorly. Two patients had an anterior crossing artery, three had a posterior crossing artery (Fig 1), two had an anterior crossing vein (Fig 2), two had a posterior crossing vein (Fig 3), one had an anterior crossing artery and vein (Fig 4), one had a posterior crossing artery and vein (Fig 5), and one had anterior and posterior crossing arteries.

View larger version (105K): [in this window] [in a new window] [Download PPT slide]   Figure 1a.   Posterior crossing artery associated with UPJ obstruction in a 40-year-old woman. (a) Axial CT scans (left image obtained at a higher level than right image) show a dilated right renal pelvis (arrows) and a crossing vessel (arrowheads). (b) Axial CT scans show planes used for coronal (left image) and curved (right image) reconstruction. U = ureter. (c) Coronal image reconstructed along the straight line in b shows the small vessel (arrow) adjacent to the most stenotic point of the UPJ. Ao = aorta, Kd = kidney, Lt = left, RP = renal pelvis, Rt = right, U = ureter. (d) Curved image reconstructed along the course of the crossing vessel (curved line in b) shows the small vessel (arrows) branching from the aorta (Ao) and crossing the UPJ. Kd = kidney, Lt = left, RP = renal pelvis, RtPo = right posterior, U = ureter.

View larger version (105K): [in this window] [in a new window] [Download PPT slide]   Figure 1b.   Posterior crossing artery associated with UPJ obstruction in a 40-year-old woman. (a) Axial CT scans (left image obtained at a higher level than right image) show a dilated right renal pelvis (arrows) and a crossing vessel (arrowheads). (b) Axial CT scans show planes used for coronal (left image) and curved (right image) reconstruction. U = ureter. (c) Coronal image reconstructed along the straight line in b shows the small vessel (arrow) adjacent to the most stenotic point of the UPJ. Ao = aorta, Kd = kidney, Lt = left, RP = renal pelvis, Rt = right, U = ureter. (d) Curved image reconstructed along the course of the crossing vessel (curved line in b) shows the small vessel (arrows) branching from the aorta (Ao) and crossing the UPJ. Kd = kidney, Lt = left, RP = renal pelvis, RtPo = right posterior, U = ureter.

View larger version (108K): [in this window] [in a new window] [Download PPT slide]   Figure 1c.   Posterior crossing artery associated with UPJ obstruction in a 40-year-old woman. (a) Axial CT scans (left image obtained at a higher level than right image) show a dilated right renal pelvis (arrows) and a crossing vessel (arrowheads). (b) Axial CT scans show planes used for coronal (left image) and curved (right image) reconstruction. U = ureter. (c) Coronal image reconstructed along the straight line in b shows the small vessel (arrow) adjacent to the most stenotic point of the UPJ. Ao = aorta, Kd = kidney, Lt = left, RP = renal pelvis, Rt = right, U = ureter. (d) Curved image reconstructed along the course of the crossing vessel (curved line in b) shows the small vessel (arrows) branching from the aorta (Ao) and crossing the UPJ. Kd = kidney, Lt = left, RP = renal pelvis, RtPo = right posterior, U = ureter.

View larger version (108K): [in this window] [in a new window] [Download PPT slide]   Figure 1d.   Posterior crossing artery associated with UPJ obstruction in a 40-year-old woman. (a) Axial CT scans (left image obtained at a higher level than right image) show a dilated right renal pelvis (arrows) and a crossing vessel (arrowheads). (b) Axial CT scans show planes used for coronal (left image) and curved (right image) reconstruction. U = ureter. (c) Coronal image reconstructed along the straight line in b shows the small vessel (arrow) adjacent to the most stenotic point of the UPJ. Ao = aorta, Kd = kidney, Lt = left, RP = renal pelvis, Rt = right, U = ureter. (d) Curved image reconstructed along the course of the crossing vessel (curved line in b) shows the small vessel (arrows) branching from the aorta (Ao) and crossing the UPJ. Kd = kidney, Lt = left, RP = renal pelvis, RtPo = right posterior, U = ureter.

View larger version (149K): [in this window] [in a new window] [Download PPT slide]   Figure 2a.   Anterior crossing vein associated with UPJ obstruction in a 31-year-old man. (a) Urogram shows left hydronephrosis. (b) Axial CT scans show the dilated left renal pelvis (left image) and a crossing vessel (arrows in right image). (c) Sagittal image reconstructed along the line in b shows the adjacent crossing vessel (arrow) anterior to the UPJ obstruction. An = anterior, Po = posterior, RP = renal pelvis, U = ureter.

View larger version (117K): [in this window] [in a new window] [Download PPT slide]   Figure 2b.   Anterior crossing vein associated with UPJ obstruction in a 31-year-old man. (a) Urogram shows left hydronephrosis. (b) Axial CT scans show the dilated left renal pelvis (left image) and a crossing vessel (arrows in right image). (c) Sagittal image reconstructed along the line in b shows the adjacent crossing vessel (arrow) anterior to the UPJ obstruction. An = anterior, Po = posterior, RP = renal pelvis, U = ureter.

View larger version (113K): [in this window] [in a new window] [Download PPT slide]   Figure 2c.   Anterior crossing vein associated with UPJ obstruction in a 31-year-old man. (a) Urogram shows left hydronephrosis. (b) Axial CT scans show the dilated left renal pelvis (left image) and a crossing vessel (arrows in right image). (c) Sagittal image reconstructed along the line in b shows the adjacent crossing vessel (arrow) anterior to the UPJ obstruction. An = anterior, Po = posterior, RP = renal pelvis, U = ureter.

View larger version (139K): [in this window] [in a new window] [Download PPT slide]   Figure 3a.   Posterior crossing vein associated with UPJ obstruction in a 60-year-old man. (a) Axial CT scan shows a dilated right renal pelvis. (b) Axial CT scans obtained at a lower level than a show a crossing vessel (arrowheads in left image) and a plane used for oblique sagittal reconstruction (right image). (c) Oblique sagittal image reconstructed along the line in b shows the small vessel (arrow) adjacent to the most stenotic point of the UPJ; this vessel is suspected of compressing the UPJ. AnRt = anterior right, Kd = kidney, PoLt = posterior left, RP = renal pelvis, U = ureter. (d) Axial CT scans (shown from superior [left image] to inferior [right image]) show that enhancement disappears proximal to the crossing vessel (arrow). RA = renal artery.

View larger version (106K): [in this window] [in a new window] [Download PPT slide]   Figure 3b.   Posterior crossing vein associated with UPJ obstruction in a 60-year-old man. (a) Axial CT scan shows a dilated right renal pelvis. (b) Axial CT scans obtained at a lower level than a show a crossing vessel (arrowheads in left image) and a plane used for oblique sagittal reconstruction (right image). (c) Oblique sagittal image reconstructed along the line in b shows the small vessel (arrow) adjacent to the most stenotic point of the UPJ; this vessel is suspected of compressing the UPJ. AnRt = anterior right, Kd = kidney, PoLt = posterior left, RP = renal pelvis, U = ureter. (d) Axial CT scans (shown from superior [left image] to inferior [right image]) show that enhancement disappears proximal to the crossing vessel (arrow). RA = renal artery.

View larger version (95K): [in this window] [in a new window] [Download PPT slide]   Figure 3c.   Posterior crossing vein associated with UPJ obstruction in a 60-year-old man. (a) Axial CT scan shows a dilated right renal pelvis. (b) Axial CT scans obtained at a lower level than a show a crossing vessel (arrowheads in left image) and a plane used for oblique sagittal reconstruction (right image). (c) Oblique sagittal image reconstructed along the line in b shows the small vessel (arrow) adjacent to the most stenotic point of the UPJ; this vessel is suspected of compressing the UPJ. AnRt = anterior right, Kd = kidney, PoLt = posterior left, RP = renal pelvis, U = ureter. (d) Axial CT scans (shown from superior [left image] to inferior [right image]) show that enhancement disappears proximal to the crossing vessel (arrow). RA = renal artery.

View larger version (85K): [in this window] [in a new window] [Download PPT slide]   Figure 3d.   Posterior crossing vein associated with UPJ obstruction in a 60-year-old man. (a) Axial CT scan shows a dilated right renal pelvis. (b) Axial CT scans obtained at a lower level than a show a crossing vessel (arrowheads in left image) and a plane used for oblique sagittal reconstruction (right image). (c) Oblique sagittal image reconstructed along the line in b shows the small vessel (arrow) adjacent to the most stenotic point of the UPJ; this vessel is suspected of compressing the UPJ. AnRt = anterior right, Kd = kidney, PoLt = posterior left, RP = renal pelvis, U = ureter. (d) Axial CT scans (shown from superior [left image] to inferior [right image]) show that enhancement disappears proximal to the crossing vessel (arrow). RA = renal artery.

View larger version (109K): [in this window] [in a new window] [Download PPT slide]   Figure 4a.   Anterior crossing artery and vein associated with UPJ obstruction in a 29-year-old woman. (a) Axial CT scans (left image obtained at a higher level than right image) show right hydronephrosis (left image) and a crossing vessel (arrowheads in right image). (b) Axial CT scans show planes used for oblique sagittal (left image) and curved (right image) reconstruction. (c) Oblique sagittal image reconstructed along the straight line in b shows two anterior crossing vessels (arrows) adjacent to the most stenotic point of the UPJ. AnLt = anterior left, Kd = kidney, PoRt = posterior right, RP = renal pelvis, U = ureter. (d) Curved image reconstructed along the course of the UPJ (curved line in b) shows two crossing vessels (arrows) anteromedial to the UPJ. Kd = kidney, LtAn = left anterior, RP = renal pelvis, RtPo = right posterior, U = ureter. (e) Other oblique sagittal images (shown from anterolateral [left image] to posteromedial [right image]) show two distinct vessels (arrows).

View larger version (110K): [in this window] [in a new window] [Download PPT slide]   Figure 4b.   Anterior crossing artery and vein associated with UPJ obstruction in a 29-year-old woman. (a) Axial CT scans (left image obtained at a higher level than right image) show right hydronephrosis (left image) and a crossing vessel (arrowheads in right image). (b) Axial CT scans show planes used for oblique sagittal (left image) and curved (right image) reconstruction. (c) Oblique sagittal image reconstructed along the straight line in b shows two anterior crossing vessels (arrows) adjacent to the most stenotic point of the UPJ. AnLt = anterior left, Kd = kidney, PoRt = posterior right, RP = renal pelvis, U = ureter. (d) Curved image reconstructed along the course of the UPJ (curved line in b) shows two crossing vessels (arrows) anteromedial to the UPJ. Kd = kidney, LtAn = left anterior, RP = renal pelvis, RtPo = right posterior, U = ureter. (e) Other oblique sagittal images (shown from anterolateral [left image] to posteromedial [right image]) show two distinct vessels (arrows).

View larger version (139K): [in this window] [in a new window] [Download PPT slide]   Figure 4c.   Anterior crossing artery and vein associated with UPJ obstruction in a 29-year-old woman. (a) Axial CT scans (left image obtained at a higher level than right image) show right hydronephrosis (left image) and a crossing vessel (arrowheads in right image). (b) Axial CT scans show planes used for oblique sagittal (left image) and curved (right image) reconstruction. (c) Oblique sagittal image reconstructed along the straight line in b shows two anterior crossing vessels (arrows) adjacent to the most stenotic point of the UPJ. AnLt = anterior left, Kd = kidney, PoRt = posterior right, RP = renal pelvis, U = ureter. (d) Curved image reconstructed along the course of the UPJ (curved line in b) shows two crossing vessels (arrows) anteromedial to the UPJ. Kd = kidney, LtAn = left anterior, RP = renal pelvis, RtPo = right posterior, U = ureter. (e) Other oblique sagittal images (shown from anterolateral [left image] to posteromedial [right image]) show two distinct vessels (arrows).

View larger version (157K): [in this window] [in a new window] [Download PPT slide]   Figure 4d.   Anterior crossing artery and vein associated with UPJ obstruction in a 29-year-old woman. (a) Axial CT scans (left image obtained at a higher level than right image) show right hydronephrosis (left image) and a crossing vessel (arrowheads in right image). (b) Axial CT scans show planes used for oblique sagittal (left image) and curved (right image) reconstruction. (c) Oblique sagittal image reconstructed along the straight line in b shows two anterior crossing vessels (arrows) adjacent to the most stenotic point of the UPJ. AnLt = anterior left, Kd = kidney, PoRt = posterior right, RP = renal pelvis, U = ureter. (d) Curved image reconstructed along the course of the UPJ (curved line in b) shows two crossing vessels (arrows) anteromedial to the UPJ. Kd = kidney, LtAn = left anterior, RP = renal pelvis, RtPo = right posterior, U = ureter. (e) Other oblique sagittal images (shown from anterolateral [left image] to posteromedial [right image]) show two distinct vessels (arrows).

View larger version (61K): [in this window] [in a new window] [Download PPT slide]   Figure 4e.   Anterior crossing artery and vein associated with UPJ obstruction in a 29-year-old woman. (a) Axial CT scans (left image obtained at a higher level than right image) show right hydronephrosis (left image) and a crossing vessel (arrowheads in right image). (b) Axial CT scans show planes used for oblique sagittal (left image) and curved (right image) reconstruction. (c) Oblique sagittal image reconstructed along the straight line in b shows two anterior crossing vessels (arrows) adjacent to the most stenotic point of the UPJ. AnLt = anterior left, Kd = kidney, PoRt = posterior right, RP = renal pelvis, U = ureter. (d) Curved image reconstructed along the course of the UPJ (curved line in b) shows two crossing vessels (arrows) anteromedial to the UPJ. Kd = kidney, LtAn = left anterior, RP = renal pelvis, RtPo = right posterior, U = ureter. (e) Other oblique sagittal images (shown from anterolateral [left image] to posteromedial [right image]) show two distinct vessels (arrows).

View larger version (104K): [in this window] [in a new window] [Download PPT slide]   Figure 5a.   Posterior crossing artery and vein in a 5-year-old boy. (a) Axial CT scans (left image obtained at a higher level than right image) show left hydronephrosis (left image) and two crossing vessels (arrowheads in right image). (b) Axial CT scans show planes used for coronal (left image) and sagittal (right image) reconstruction. (c, d) Coronal (c) and sagittal (d) images reconstructed along lines c and d in b, respectively, show a crossing vessel (arrow) adjacent and posteromedial to the UPJ obstruction. On these images, only one crossing vessel is seen. An = anterior, Ao = aorta, Kd = kidney, Lt = left, Po = posterior, RP = renal pelvis, Rt = right, U = ureter. (e, f) Coronal (e) and sagittal (f) images reconstructed along lines e and f in b, respectively, show two vessels (arrows). An = anterior, Ao = aorta, Kd = kidney, Lt = left, Po = posterior, RP = renal pelvis, Rt = right. Like CT, retroperitoneoscopy also showed that two crossing vessels (artery and vein) were adjacent and posterior to the UPJ and that both vessels were associated with UPJ obstruction.

View larger version (108K): [in this window] [in a new window] [Download PPT slide]   Figure 5b.   Posterior crossing artery and vein in a 5-year-old boy. (a) Axial CT scans (left image obtained at a higher level than right image) show left hydronephrosis (left image) and two crossing vessels (arrowheads in right image). (b) Axial CT scans show planes used for coronal (left image) and sagittal (right image) reconstruction. (c, d) Coronal (c) and sagittal (d) images reconstructed along lines c and d in b, respectively, show a crossing vessel (arrow) adjacent and posteromedial to the UPJ obstruction. On these images, only one crossing vessel is seen. An = anterior, Ao = aorta, Kd = kidney, Lt = left, Po = posterior, RP = renal pelvis, Rt = right, U = ureter. (e, f) Coronal (e) and sagittal (f) images reconstructed along lines e and f in b, respectively, show two vessels (arrows). An = anterior, Ao = aorta, Kd = kidney, Lt = left, Po = posterior, RP = renal pelvis, Rt = right. Like CT, retroperitoneoscopy also showed that two crossing vessels (artery and vein) were adjacent and posterior to the UPJ and that both vessels were associated with UPJ obstruction.

View larger version (147K): [in this window] [in a new window] [Download PPT slide]   Figure 5c.   Posterior crossing artery and vein in a 5-year-old boy. (a) Axial CT scans (left image obtained at a higher level than right image) show left hydronephrosis (left image) and two crossing vessels (arrowheads in right image). (b) Axial CT scans show planes used for coronal (left image) and sagittal (right image) reconstruction. (c, d) Coronal (c) and sagittal (d) images reconstructed along lines c and d in b, respectively, show a crossing vessel (arrow) adjacent and posteromedial to the UPJ obstruction. On these images, only one crossing vessel is seen. An = anterior, Ao = aorta, Kd = kidney, Lt = left, Po = posterior, RP = renal pelvis, Rt = right, U = ureter. (e, f) Coronal (e) and sagittal (f) images reconstructed along lines e and f in b, respectively, show two vessels (arrows). An = anterior, Ao = aorta, Kd = kidney, Lt = left, Po = posterior, RP = renal pelvis, Rt = right. Like CT, retroperitoneoscopy also showed that two crossing vessels (artery and vein) were adjacent and posterior to the UPJ and that both vessels were associated with UPJ obstruction.

View larger version (158K): [in this window] [in a new window] [Download PPT slide]   Figure 5d.   Posterior crossing artery and vein in a 5-year-old boy. (a) Axial CT scans (left image obtained at a higher level than right image) show left hydronephrosis (left image) and two crossing vessels (arrowheads in right image). (b) Axial CT scans show planes used for coronal (left image) and sagittal (right image) reconstruction. (c, d) Coronal (c) and sagittal (d) images reconstructed along lines c and d in b, respectively, show a crossing vessel (arrow) adjacent and posteromedial to the UPJ obstruction. On these images, only one crossing vessel is seen. An = anterior, Ao = aorta, Kd = kidney, Lt = left, Po = posterior, RP = renal pelvis, Rt = right, U = ureter. (e, f) Coronal (e) and sagittal (f) images reconstructed along lines e and f in b, respectively, show two vessels (arrows). An = anterior, Ao = aorta, Kd = kidney, Lt = left, Po = posterior, RP = renal pelvis, Rt = right. Like CT, retroperitoneoscopy also showed that two crossing vessels (artery and vein) were adjacent and posterior to the UPJ and that both vessels were associated with UPJ obstruction.

View larger version (130K): [in this window] [in a new window] [Download PPT slide]   Figure 5e.   Posterior crossing artery and vein in a 5-year-old boy. (a) Axial CT scans (left image obtained at a higher level than right image) show left hydronephrosis (left image) and two crossing vessels (arrowheads in right image). (b) Axial CT scans show planes used for coronal (left image) and sagittal (right image) reconstruction. (c, d) Coronal (c) and sagittal (d) images reconstructed along lines c and d in b, respectively, show a crossing vessel (arrow) adjacent and posteromedial to the UPJ obstruction. On these images, only one crossing vessel is seen. An = anterior, Ao = aorta, Kd = kidney, Lt = left, Po = posterior, RP = renal pelvis, Rt = right, U = ureter. (e, f) Coronal (e) and sagittal (f) images reconstructed along lines e and f in b, respectively, show two vessels (arrows). An = anterior, Ao = aorta, Kd = kidney, Lt = left, Po = posterior, RP = renal pelvis, Rt = right. Like CT, retroperitoneoscopy also showed that two crossing vessels (artery and vein) were adjacent and posterior to the UPJ and that both vessels were associated with UPJ obstruction.

View larger version (151K): [in this window] [in a new window] [Download PPT slide]   Figure 5f.   Posterior crossing artery and vein in a 5-year-old boy. (a) Axial CT scans (left image obtained at a higher level than right image) show left hydronephrosis (left image) and two crossing vessels (arrowheads in right image). (b) Axial CT scans show planes used for coronal (left image) and sagittal (right image) reconstruction. (c, d) Coronal (c) and sagittal (d) images reconstructed along lines c and d in b, respectively, show a crossing vessel (arrow) adjacent and posteromedial to the UPJ obstruction. On these images, only one crossing vessel is seen. An = anterior, Ao = aorta, Kd = kidney, Lt = left, Po = posterior, RP = renal pelvis, Rt = right, U = ureter. (e, f) Coronal (e) and sagittal (f) images reconstructed along lines e and f in b, respectively, show two vessels (arrows). An = anterior, Ao = aorta, Kd = kidney, Lt = left, Po = posterior, RP = renal pelvis, Rt = right. Like CT, retroperitoneoscopy also showed that two crossing vessels (artery and vein) were adjacent and posterior to the UPJ and that both vessels were associated with UPJ obstruction.

Anatomic Locations of Crossing Vessels
The position of the crossing vessel relative to the UPJ was anterior in five cases (42%), posterior in six cases (50%), and anterior and posterior in one case (8%) (Fig 6). When the one case of anterior and posterior crossing vessels is included, posterior crossing vessels were seen in seven of 12 cases (58%). Therefore, we speculated that the prevalence of crossing vessels located posterior to the UPJ may not be as low as reported in previous anatomic investigations (4,16) and that performing ureteronephroscopic endopyelotomy without confirming the position of crossing vessels is associated with a high risk of hemorrhagic complications. It is possible that the small number of patients in our study may be the reason for this discrepancy. In addition, the difference between our findings and those of Sampaio and Favorito (4) may be attributable to the fact that their study was performed on cadavers without UPJ obstruction. Conversely, Farrés et al (17) reported that the vessel crossed the UPJ posteriorly in six of 13 cases, a relatively high frequency. They also reported that the crossing vessels were obstructive in 10 of 13 cases (17). These results are comparable with those of our study.

View larger version (127K): [in this window] [in a new window] [Download PPT slide]   Figure 6a.   Anterior and posterior crossing arteries associated with UPJ obstruction in a 26-year-old man. (a) Axial CT scan shows right hydronephrosis. (b) Axial CT scans obtained at a lower level than a show two crossing vessels (arrows in left image) and a plane used for oblique sagittal reconstruction (right image). We confirmed the connection between the two vessels and the aorta by tracing them on many images. (c) Oblique sagittal image reconstructed along the line in b shows one artery located anterior and the other posterior to the UPJ (arrows); the UPJ is sandwiched and compressed between the arteries. AnRt = anterior right, PoLt = posterior left, RP = renal pelvis, U = ureter.

View larger version (108K): [in this window] [in a new window] [Download PPT slide]   Figure 6b.   Anterior and posterior crossing arteries associated with UPJ obstruction in a 26-year-old man. (a) Axial CT scan shows right hydronephrosis. (b) Axial CT scans obtained at a lower level than a show two crossing vessels (arrows in left image) and a plane used for oblique sagittal reconstruction (right image). We confirmed the connection between the two vessels and the aorta by tracing them on many images. (c) Oblique sagittal image reconstructed along the line in b shows one artery located anterior and the other posterior to the UPJ (arrows); the UPJ is sandwiched and compressed between the arteries. AnRt = anterior right, PoLt = posterior left, RP = renal pelvis, U = ureter.

View larger version (59K): [in this window] [in a new window] [Download PPT slide]   Figure 6c.   Anterior and posterior crossing arteries associated with UPJ obstruction in a 26-year-old man. (a) Axial CT scan shows right hydronephrosis. (b) Axial CT scans obtained at a lower level than a show two crossing vessels (arrows in left image) and a plane used for oblique sagittal reconstruction (right image). We confirmed the connection between the two vessels and the aorta by tracing them on many images. (c) Oblique sagittal image reconstructed along the line in b shows one artery located anterior and the other posterior to the UPJ (arrows); the UPJ is sandwiched and compressed between the arteries. AnRt = anterior right, PoLt = posterior left, RP = renal pelvis, U = ureter.

In 11 of our 12 cases, the crossing vessels were considered to be associated with UPJ obstruction at helical CT. In the remaining case, in which there was a posterior crossing artery, an oblique coronal image showed that the crossing vessel was located slightly under the point of UPJ obstruction (Fig 7); we therefore judged that the crossing vessel was not associated with UPJ obstruction. When differential diagnosis based on coronal images and sagittal images is difficult, oblique coronal, oblique sagittal, or curved reconstruction images are helpful. In the 11 cases in which we suspected that crossing vessels were associated with UPJ obstruction, retroperitoneoscopic repair was performed. In 10 of these 11 cases, the crossing vessels were associated with UPJ obstruction, in agreement with the helical CT findings. The vessel associated with obstruction was an artery in five cases and a vein in three cases; an artery and a vein were associated with obstruction in two cases. When the two cases of an artery and a vein associated with obstruction are included, a vein was involved in 50% of the cases, not a low frequency. The vessels were anterior to the UPJ in five cases, posterior in four cases, and anterior and posterior in one case (Table 3). In the remaining case, the vessel located near the UPJ did not compress the UPJ (Fig 8). Although we could rule out an association with UPJ obstruction in one case, in this remaining case even curved reconstruction images did not provide adequate information. Determining whether crossing vessels are associated with UPJ obstruction is difficult in some cases even if the vessel is assessed according to the two radiologic findings discussed previously: contact with the most stenotic point of the UPJ and compression or deviation of the UPJ.

View larger version (97K): [in this window] [in a new window] [Download PPT slide]   Figure 7a.   Posterior crossing artery not associated with UPJ obstruction in a 57-year-old woman. (a) Axial CT scans show a crossing vessel (arrows in left image) adjacent to the UPJ and a plane used for oblique coronal reconstruction (right image). U = ureter. (b) Oblique coronal image reconstructed along the line in a shows left hydronephrosis and the vessel (arrow) crossing adjacent and posterior to the UPJ; however, the vessel is located slightly under the point of UPJ obstruction. LtPo = left posterior, RP = renal pelvis, RtAn = right anterior, U = ureter. (c) Oblique coronal image obtained immediately posteromedial to b shows no crossing vessel at the most stenotic point of the UPJ. Kd = kidney, LtPo = left posterior, RP = renal pelvis, RtAn = right anterior, U = ureter.

View larger version (119K): [in this window] [in a new window] [Download PPT slide]   Figure 7b.   Posterior crossing artery not associated with UPJ obstruction in a 57-year-old woman. (a) Axial CT scans show a crossing vessel (arrows in left image) adjacent to the UPJ and a plane used for oblique coronal reconstruction (right image). U = ureter. (b) Oblique coronal image reconstructed along the line in a shows left hydronephrosis and the vessel (arrow) crossing adjacent and posterior to the UPJ; however, the vessel is located slightly under the point of UPJ obstruction. LtPo = left posterior, RP = renal pelvis, RtAn = right anterior, U = ureter. (c) Oblique coronal image obtained immediately posteromedial to b shows no crossing vessel at the most stenotic point of the UPJ. Kd = kidney, LtPo = left posterior, RP = renal pelvis, RtAn = right anterior, U = ureter.

View larger version (116K): [in this window] [in a new window] [Download PPT slide]   Figure 7c.   Posterior crossing artery not associated with UPJ obstruction in a 57-year-old woman. (a) Axial CT scans show a crossing vessel (arrows in left image) adjacent to the UPJ and a plane used for oblique coronal reconstruction (right image). U = ureter. (b) Oblique coronal image reconstructed along the line in a shows left hydronephrosis and the vessel (arrow) crossing adjacent and posterior to the UPJ; however, the vessel is located slightly under the point of UPJ obstruction. LtPo = left posterior, RP = renal pelvis, RtAn = right anterior, U = ureter. (c) Oblique coronal image obtained immediately posteromedial to b shows no crossing vessel at the most stenotic point of the UPJ. Kd = kidney, LtPo = left posterior, RP = renal pelvis, RtAn = right anterior, U = ureter.

View larger version (105K): [in this window] [in a new window] [Download PPT slide]   Figure 8a.   Posterior crossing vein not associated with UPJ obstruction in a 10-year-old boy. (a) Axial CT scans show a crossing vessel (arrows in left image) posterior to the UPJ and a plane used for sagittal reconstruction (right image). (b) Sagittal image reconstructed along the line in a shows the crossing vessel (arrows) adjacent to the most stenotic point of the UPJ. We therefore suspected that the crossing vessel was associated with UPJ obstruction. However, the vessel was found not to compress the UPJ at retroperitoneoscopy. An = anterior, Kd = kidney, Po = posterior, RP = renal pelvis, U = ureter.

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 8b.   Posterior crossing vein not associated with UPJ obstruction in a 10-year-old boy. (a) Axial CT scans show a crossing vessel (arrows in left image) posterior to the UPJ and a plane used for sagittal reconstruction (right image). (b) Sagittal image reconstructed along the line in a shows the crossing vessel (arrows) adjacent to the most stenotic point of the UPJ. We therefore suspected that the crossing vessel was associated with UPJ obstruction. However, the vessel was found not to compress the UPJ at retroperitoneoscopy. An = anterior, Kd = kidney, Po = posterior, RP = renal pelvis, U = ureter.

In our patient population, retrograde ureteronephroscopic endopyelotomy was performed in the eight patients in whom no crossing vessels were seen at helical CT; the UPJ obstruction was relieved in all cases, without any complications such as bleeding due to injury to blood vessels. In the one patient in whom the crossing vessel was considered not to be associated with UPJ obstruction at helical CT, endopyelotomy was performed by avoiding the location of the crossing vessel as shown on the CT images, with no complications.

	Conclusions

Top Abstract Introduction Materials and Methods Results and Discussion Conclusions References

 
Even if it is difficult to clearly distinguish between crossing vessels that are incidental versus those that are causing obstruction, dual-phase helical CT is a noninvasive examination and allows us to determine the appropriate treatment by providing a large amount of useful information regarding the presence, type, and anatomic location of crossing vessels in patients with UPJ obstruction. Therefore, we believe that dual-phase helical CT should be performed in all patients with UPJ obstruction.

	Footnotes

 
See the commentary by Assimos.

Abbreviation: UPJ = ureteropelvic junction

	References

Top Abstract Introduction Materials and Methods Results and Discussion Conclusions References

 

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