Prolonged CT urography in duplex kidney

Abstract

Background: Duplex kidney is a common anomaly that is frequently associated with multiple complications. Typical computed tomography urography (CTU) includes four phases (unenhanced, arterial, parenchymal and excretory) and has been suggested to considerably aid in the duplex kidney diagnosi. Unfortunately, regarding duplex kidney with prolonged dilatation, the affected parenchyma and tortuous ureters demonstrate a lack of or delayed excretory opacification. We used prolonged-delay CTU, which consists of another prolonged-delay phase (1- to 72-h delay; mean delay: 24 h) to opacify the duplicated ureters and affected parenchyma.

Methods: Seventeen patients (9 males and 8 females; age range: 2.5-56 y; mean age: 40.4 y) with duplex kidney were included in this study. Unenhanced scans did not find typical characteristics of duplex kidney, except for irregular perirenal morphology. Duplex kidney could not be confirmed on typical four-phase CTU, whereas it could be easily diagnosed in axial and CT-3D reconstruction using prolonged CTU (prolonged-delay phase).

Results: Between January 2005 and October 2010, in this review board-approved study (with waived informed consent), 17 patients (9 males and 8 females; age range: 2.5 ~ 56 y; mean age: 40.4 y) with suspicious duplex kidney underwent prolonged CTU to opacify the duplicated ureters and confirm the diagnosis.

Conclusion: Our results suggest the validity of prolonged CTU to aid in the evaluation of the function of the affected parenchyma and in the demonstration of urinary tract malformations.

Keywords: Duplex kidney; Duplicated ureters; Multi-slice spiral CT urography; Prolonged-delay contrast enhancement.

Fig. 1

Case 1. A 56-year-old male patient with right side duplex kidney. Unenhanced supine axial CT (a) shows a solitary round, iso-dense, soft-tissue mass with a clear boundary (short arrow). The irregularly annular calcified shadow around the mass was equivalent to multiple annular low-density shadows in the ileocecal junction (long arrow). The mass was not clearly intensified after contrast enhancement (b) and one-hour delayed (c) CTU scanning. Interestingly, it was obviously strengthened after 18-h delay (d), confirming duplex kidney. Furthermore, we found a band of high-density shadows that was confirmed to be duplicated ureters (double-headed arrow). Reformatted 3D CTU after segmentation of bone structures also showed the entire course of the dilated ureters (e)

Fig. 2

Case 2. CT scans obtained in a 46-year-old woman with left duplex kidney & ectopic ureter openings. Non- enhanced scan obtained at the level of the upper-middle pole of the left kidney shows areas of abnormal low-density (red faint arrow) and stone shadow (red solid arrow) (a). Contrast-enhanced scans obtained at the same level as in (a). The upper-middle pole of the left kidney (blue arrow) shows no enhancement on the 6-min scan (b) and abnormal low density enhancement on the 3 h (c), 18 h (d), 24 h (e) and 45 h (f) scan, and ectopic ureter openings can be seen in (e) (blue arrow)

Fig. 3

Case 3. CT obtained in a 3.5-year-old boy with left duplex kidney & ureters, and congenital megaflop-ureter. Non- enhanced scan obtained at the abdomen & pelvis shows fluid-filled loops, the normal bowel loops are compressed to the right side of the abdominal wall, and a tendon-like shadow can be seen in the bowel loop-like areas (red arrow) (a). The tendon-like shadow was intensified as the normal ureter (red arrow) (b), and the normal bladder was also intensified in the left side pelvis (red arrow) on the 54-min scan (c). Meanwhile, MIP reconstruction shows the position and course of left ureter changed (red arrow) (d). The left ureter shows delayed enhancement on the 3-h and 13-min scan (e). The area of the left side kidney shows a little irregular enhancement on the 23 h and 9-min scan (red arrow) (f). Operation findings (g)

Fig. 4

Case 4. CT scans obtained in a 2.5-year-old girl with left duplex ureters and congenital megalo-ureter. Non-enhanced scan obtained at the level of the inferior-middle pole of the left kidney shows a huge round-like area of low density (red arrow) (a). Contrast-enhanced scans were obtained at the same level as in (a), this area showed no enhancement on (b) the 26-h scan, and the tortuous contrast agent can be seen retroperitoneally (red arrow) (b). The huge round-like area of low density was intensified on the 48-h scan (red arrow) (c)

Fig. 5

Case 5. CT scans obtained in a 20-year-old man with left congenital megaloureter. Nonenhanced scan obtained at the abdomen & pelvis shows huge fluid-filled loops (red arrow), and the normal bowel loops are compressed to the right side of the abdominal wall (a). The left renal pelvis and calyces show marked dilation, with parenchyma thinning (red arrow) on parenchymal phase enhancement (b), for unknown reason the images of prolonged phase were missing