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Introduction

Retrocaval ureter is a rare condition thatresultsfromananomalyinthedevelopmentoftheinferiorvenacava(1).Theincidencewasreportedto be approximately 1 in 1000 people, withmale predominance (2). The anomalous vesselcompresses the ureter, causing varying degreesofhydronephrosis.Thepatientsareusually30to40yearsofageatthetimeofdiagnosisduetothegradualdevelopmentofhydronephrosis.Imagingstudies are usually sufficient for an accuratepre-operative diagnosis, which is important forsuccessfulsurgicalintervention(2).

Case Report

A 62-year-old man was referred to theurology clinic due to incomplete voiding anddribbling of urine for the past 5 years. Clinicalexamination was unremarkable except for amildly enlarged prostate gland. Laboratoryinvestigations were normal. Ultrasound (US) oftheabdomenandpelvisshowedamildlyenlargedprostate.Thepatientwasdiagnosedand treatedforbenignprostatichypertrophy.DuringtheUSexamination,righthydronephrosisandproximalhydroureter were incidentally discovered. Therewas no calculus detected. Because there wasevidence of a right obstructed system, abdomenand pelvis multislice computed tomography

Case Report

Submitted: 21Dec2010Accepted: 30Jan2011

(MSCT)wasperformedtoruleoutrighturetericcalculus, which could be missed on US. MSCTshowed a persistent right hydronephrosis andhydroureterbutdidnotdemonstrateanycalculus.Therightureterwasdilateduptoitsmidlevel,butnot traceable along the expected coursedistally,mainlydue topoorfillingof contrastwithin theureter. Correlating with US findings, there is apossibility of a right ureteric stricture from aprevious passage of calculus. Based on US andCT findings, cystoscopy was then performed,and kinking of the right ureter at level L3 wasnoted.Therightureterproximaltothekinkwasdilatedwithno intraluminal lesionseen.Arighturetericstentwastheninserted.Thispatienthadan intravenous urography (IVU) done after theprocedure,andthefindingswerecharacteristicofaretrocavalureter(Figure1).Therightretrocavalureter could actually be seenwhen the axialCTimageswereretrospectivelyreviewed(Figure2),butthiswasnotdemonstratedonthemultiplanarreformatted images or the 3-dimensionalreconstructed images because of poor contrastopacification of the distal ureter (Figure 3). Aretrogradepyelogram(RPG)performed2monthslater showed no ureteric calculus. The patientrecovered well after the removal of the uretericstent,butherefusedfurthersurgicalintervention.

Retrocaval Ureter: The Importance of Intravenous Urography Radhiana Hassan, Azian abd aziz, Siti Kamariah CHe MoHaMed

Department of Radiology, Kulliyyah of Medicine, International Islamic University Malaysia, Bandar Indera Mahkota, 25200 Kuantan, Pahang, Malaysia

Abstract Retrocavalureterisararecauseofhydronephrosis.Itsrarityandnon-specificpresentationposeachallengetosurgeonsandradiologistsinmakingthecorrectdiagnosis.Differentiationfromothercausesofurinarytractobstruction,especiallythemorecommonurolithiasis,isimportantforsuccessfulsurgicalmanagement.Currentpracticehasseenmultislicecomputedtomography(MSCT)rapidlyreplaces intravenousurography(IVU) in theassessmentofpatientswithhydronephrosisdue to suspected urolithiasis, especially ureterolithiasis. However, MSCT, without adequateopacificationoftheentireureter,mayallowthephysiciantooverlookaretrocavalureterasthecauseofhydronephrosis.High-resolutionIVUimagescandemonstratethetypicalappearancethatleadstotheaccuratediagnosisofaretrocavalureter.WereportedacasethatillustratesthisscenarioandhighlightstheimportanceofIVUintheassessmentofacomplexcongenitaldisorderinvolvingtheurinarytract.

Keywords:computed tomography, hydronephrosis, ureteral diseases, urography, urology

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Discussion

ChangingpracticepatternshaveledtoMSCTreplacingIVUintheassessmentofpatientswithsuspectedurolithiasis,especiallyuretericcalculus(3,4).MSCTispreferredoverIVUbyphysiciansbecause of its high sensitivity (96%), specificity(99%), and accuracy (96%) for the detectionof ureteric calculus (5). MSCT is fast, widelyavailable, canbedonewithorwithout contrast,depending on clinical indication, and can alsoshowsignsofurinarytractobstruction.However,in complex cases of congenital anomaly, thediagnosis may be missed due to its rarity andsubtlenature.Asillustratedinourpatient,MSCTscan was not able to visualise the entire rightureterduringtheexcretoryphaseduetopoolingofcontrastinthedilatedrenalpelvisandproximalureter. Thus, the multiplanar reformatted and3-dimensional reconstruction image was not

Figure 1: Intravenous urogram showing right-sidedhydronephrosisandthedilationoftheproximalureteruptothelevelof the L3 transverse process. Themedialdeviationof theureterat thislevel (arrow) gives rise to the typicalfishhookorreversedSappearance.

Figure 2: Contrast-enhanced computedtomography scan in the axialview showing (A) the dilatedright ureter (U) proximal to itsobstruction.Theureterfollowsamedialcourseatthislevel(solidarrow),posterior to the inferiorvena cava (C). At a lower scan(B),theretrocavallocationoftherightureterismedialcomparedwith the normal location of theleftureter(dashedarrow).

useful in this instance. A normal size non-opacifieduretercanbedifficulttotrace;therefore,acongenitalanomaly,suchasaretrocavalureter,canbemissed if it isnot considered.One studyreported low sensitivity (59%) in the detectionofureteralabnormality(ureteralduplication)onaxial non-contrasted CT, even when the imageswerereviewedbyradiologistswhospecialisedingenitourinaryimaging(6). IVU has some advantages; it can providegood image resolution and the examination canbemodified according to the clinical needs, forexample, obtaining delayed images or changingthepatient’spositiontotrytovisualisetheentirelength of the ureter. Although not diagnostic,the appearance of retrocaval ureter on IVU istypical and is highly suggestive of the diagnosis(7).MSCT,however,isperformedtoconfirmthediagnosisandtoruleoutothercausesofureteraldeviation. On a CT scan, the lateral placement

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Malaysian J Med Sci. Oct-Dec 2011; 18(4): 84-87

Figure 3: A 3-dimensional reconstructionimagefromtheexcretoryphaseofcomputed tomography showingthe normal course and calibreof the left ureter (short arrows).However, the right ureter wasnot visualised due to inadequateopacification and contrast filling.The contrast is seen pooling inthe dilated right renal pelvis andproximalureter(longarrow).

of the IVC to the right pedicle is found in allpatients with retrocaval ureters but in only 6%ofnormalpatients(1,8).Recently,MRIwasalsoreportedtobeusefulindemonstratingretrocavalureter and correlated well with IVU (2,9). Ithas theadvantageofbeingradiation freeandofproviding multiplanar images. However, it maynotbepracticalinoursettingduetoitshighcostand limited availability in some health centres.Inourcase,themainfocuswastodetectpossibleureteric calculus that was thought to cause theobstruction; therefore,whenUSandCTdidnotshow any calculus, invasive procedures, such ascystoscopyandRPG,couldbeperformed. Theradiologicalfeaturesofretrocavalureteron IVU are divided into 2 types. In Type 1, theuretercrossesbehind the IVCat the levelof the3rdlumbarvertebraandhasafishhook–shaped

or S-shaped deformity of the ureter. It is alsoknownasthelowloopretrocavalureter.Markedhydronephrosisisseeninover50%ofpatients.InType2,theretrocavalsegmentisatthesamelevelastherenalpelvis;thesickle-shapeappearanceoftheinvolveduretercanberesolvedonIVU.Type2 generally causes mild hydronephrosis and islesscommoncomparedwithType1(10). Treatment depends on the clinicalpresentation,theseverityofhydronephrosis,andthe impairment of renal function. Patients withmild hydronephrosis without renal impairmentor any associated complication can bemanagedconservatively with periodic examinations (2).Ureteroureteral reanastomosis anterior to theIVC with resection of the retrocaval segment isthefavouredsurgicaltreatment,withgoodresultsreported(2). IVU, which is an old and traditionalexamination that is considered to be almostobsolete by some, is still valuable for theassessment of genitourinary tract pathology,especially congenital anomaly, as demonstratedinthiscase.

Authors’ Contribution

Conceptionanddesign,draftingofthearticle:RHCollection,assembly,analysisandinterpretationofthedata,criticalrevisionandfinalapprovalofthearticle:RH,AAA,SKCM

Correspondence

DrRadhianaHassanMD(USM),MMedRadiology(USM)DepartmentofRadiology,KulliyyahofMedicineInternationalIslamicUniversityMalaysiaBandarInderaMahkota25200KuantanPahang,MalaysiaTel:+609-5572056Fax:+609-5149396Email:radhianahassan@gmail.com

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