The ureter normally originates at the renal pelvis and runs caudoventrally and medially in the retroperitoneal space to terminate at the bladder. The right ureter is closely associated with the vena cava. Circumcaval ureter, also known as retrocaval ureter, is a condition where the ureter passes dorsal to the vena cava. It results from a developmental anomaly of the inferior vena cava (caudal vena cava in nonhuman mammals) in relation to the ureter.1,2 The right caudal cardinal vein from the embryogenic venous system persists after birth instead of degenerating, pushes the ureter during its migration, and entraps it, leading to the development of circumcaval ureter.3
Circumcaval ureter has a reported frequency of 1/1,000 live births4,5 in people. It is almost exclusively right-sided,2,4 but left-sided circumcaval ureter has been observed in patients with situs viscerum inversus. A male-to-female ratio of 2:11 has been reported. More than 20% of affected people have concomitant abnormalities of the cardiovascular system and genitourinary tract.2
In human urology, circumcaval ureters have been classified into 2 clinical types according to their radiographic appearance.6 With type I, or low loop, circumcaval ureter, the middle ureteral segment sharply deviates medially, creating a fish-hook deformity.6–8 This type is the most common in people and the most frequently symptomatic.1 Symptomatic patients have right-sided abdominal pain and recurrent urinary tract infection with or without hematuria,1 and 50% of patients have moderate to severe hydronephrosis.6 With type II, or high loop, circumcaval ureter, the ureter passes around the caudal vena cava at the level of the ureteropelvic junction.8 With this type, the proximal portion of the ureter is not kinked. The renal pelvis and proximal portion of the ureter are directed almost horizontally, and the ureter travels in a gentle curve to encircle the caudal vena cava.6 This type is associated with mild or no hydronephrosis and occurs in only 10% of patients.
Treatment in symptomatic human patients with type I circumcaval ureter involves excision or stenting of the narrowed middle segment of the ureter.1,9 In patients in which ureteral resection and anastomosis has been performed, histologic evaluation of the excised ureteral segment has shown sclerosis and muscular hypertrophy.1 In symptomatic patients with type II circumcaval ureter, the stenotic ureteropelvic junction is excised, and the proximal portion of the ureter is spatulated and anastomosed to the renal pelvis.8
In cats, the ureters leave the kidney to course retroperitoneally toward the urinary bladder, where they enter at an acute angle on the bladder's dorsal surface and tunnel through the muscular wall before opening into the lumen.10
Circumcaval ureter has been reported previously in 2 dogs11,12 and 5 cats.13,14 A left circumcaval ureter was reported in a female Bernese Mountain Dog with a right divisional intrahepatic portosystemic shunt.11 The circumcaval ureter in this dog was associated with hydroureter and hydronephrosis. In another female Bernese Mountain Dog, left ureterohydronephrosis secondary to transposition of the caudal vena cava and circumcaval ureter was diagnosed by means of MRI.12 A right circumcaval ureter was identified as an incidental finding in a cat during routine dissection for teaching purposes.13 The right ureter deviated medially before crossing the vena cava dorsally at the level of the fifth lumbar vertebra. It continued between the caudal vena cava and the abdominal aorta, coursed back ventrolateral to the caudal vena cava, and entered the trigone normally.13 Hydronephrosis, hydroureter, and signs of urinary tract inflammation were not present. Right circumcaval ureters were also found in 4 other cats, all with ureteral obstruction in the proximal ureteral segment, a few centimeters cranial to the area where the vena cava crossed the ureter.14
Circumcaval ureters have been induced experimentally in rabbits. Exposure of fetal rabbits to high doses of diethylene glycol monomethyl ether, a chemical found in industrial solvents, caused circumcaval ureter and renal pelvis dilation as well as forelimb flexure, cervical spondylosis, and delayed ossification of sternebrae and the skull.15
The current scientific literature suggests that circumcaval ureters are rare in cats, but at our institution, they have been observed relatively commonly during teaching laboratories that use feline cadavers. To our knowledge, no data on the prevalence of circumcaval ureter in domestic cats have been published. The primary objective of the study reported here, therefore, was to determine the prevalence of circumcaval ureters in cats. The secondary objective was to determine whether there was macroscopic evidence of ureteral obstruction in cats in which circumcaval ureters were identified. We hypothesized that circumcaval ureters would be relatively common in cats, but that macroscopic evidence of ureteral obstruction would not be detected.
GraphPad Prism, version 4.00 for Windows, GraphPad Software Inc, San Diego, Calif.
1. Bagheri F, Pusztai C, Szántó A, et al. Laparoscopic repair of circumcaval ureter: one-year follow-up of three patients and literature review. Urology 2009; 74:148–153.
2. Perimenis P, Gyftopoulos K, Athanasopoulos A, et al. Retrocaval ureter and associated abnormalities. Int Urol Nephrol 2002; 33:19–22.
3. Artico M, Lorenzini D, Mancini P, et al. Radiological evidence of anatomical variation of the inferior vena cava: report of two cases. Surg Radiol Anat 2004; 26:153–156.
4. Sener RN. Nonobstructive right circumcaval ureter associated with double inferior vena cava. Urology 1993; 41:356–360.
5. Chou CT, Yang AD, Hong YC, et al. Bilateral retrocaval ureters with IVC duplication. Abdom Imaging 2006; 31:596–597.
6. Salonia A, Maccagnano C, Lesma A, et al. Diagnosis and treatment of the circumcaval ureter. In: European urology supplements 5. Amsterdam: Elsevier BV, 2006;449–462.
8. Basok EK, Yildirim A, Tokuc R. Type I and II circumcaval ureter in children: experience in three cases. Adv Ther 2008; 25:375–379.
9. Baba S, Oya M, Miyahara M, et al. Laparoscopic surgical correction of circumcaval ureter. Urology 1994; 44:122–126.
11. Doust RT, Clarke SP, Hammond G, et al. Circumcaval ureter associated with an intrahepatic portosystemic shunt in a dog. J Am Vet Med Assoc 2006; 228:389–391.
12. Duconseille AC, Louvet A, Lazard P, et al. Imaging diagnosis—left retrocaval ureter and transposition of the caudal vena cava in a dog. Vet Radiol Ultrasound 2010; 51:52–56.
14. Zaid MS, Berent AC, Weisse C, et al. Feline ureteral strictures: 10 cases (2007–2009). J Vet Intern Med 2011; 25:222–229.
15. Scortichini BH, John-Greene JA, Quast JF, et al. Teratologic evaluation of dermally applied diethylene glycol monomethyl ether in rabbits. Fundam Appl Toxicol 1986; 7:68–75.
16. Shiroma JT, Gabriel JK, Carter RL, et al. Effect of reproductive status on feline renal size. Vet Radiol Ultrasound 1999; 40:242–245.
17. Cornillie P, Simoens P. Prenatal development of the caudal vena cava in mammals: review of the different theories with special reference to the dog. Anat Histol Embryol 2005; 34:364–372.
18. Latshaw WK. Veterinary developmental anatomy: a clinically oriented approach. Hamilton, ON, Canada: BC Decker Inc, 1987;188–203.
19. Kyles AE, Hardie EM, Wooden BG, et al. Clinical, clinicopathologic, radiographic, and ultrasonographic abnormalities in cats with ureteral calculi: 163 cases (1984–2002). J Am Vet Med Assoc 2005; 226:932–936.
21. Soundappan SVS, Barker AP. Retrocaval ureter in children: a report of two cases. Pediatr Surg Int 2004; 20:158–160.