1Sevin Ayaz MD, 2Ümit Ya�ar Ayaz MD

1. Department of Nuclear Medicine,

Mersin State Hospital, Mersin, Turkey

2. Department of Radiology, Mersin

Women's and Children's Hospital,

Mersin, Turkey

Keywords: Pos�tron em�ss�on

tomography -Tomography

-X-Rays computed -Renal ve�ns

-Anatom�c var�at�on

Corresponding author: Dr. Sevin Ayaz, MD

Mers�n Devlet Hastanes�, Nükleer

T�p Bölümü, 33050 Mers�n, Turkey

Tel: +90 537 7639443

sev�nayaz@yahoo.com

Dr. Üm�t Ya�ar Ayaz, MD

Mers�n Kad�n Dogum ve Çocuk

Hastal�klar� Hastanes�, Radyoloj�

Bölümü, Halkkent, Toroslar,

33240 Mers�n, Turkey

Tel: +90 537 7639442

um�tyasarayaz@gma�l.com

Rece�ved:

14 April 2016

Accepted revised:

20 April 2016

Detection of retroaortic left renal vein and circumaortic

left renal vein by PET/CT images to avoid misdiagnosis

and support possible surgical procedures

AbstractObjective: We a�med to �dent�fy retroaort�c left renal ve�n (RLRV) and c�rcumaort�c left renal ve�n (CLRV) by us�ng pos�tron em�ss�on tomography/computed tomography (PET/CT) �mages, to obta�n the�r percentages and to evaluate the e�ect of gender on the�r frequenc�es. Subjects and Methods: Pla�n CT and �uor�ne-18-2-�uoro-2-deoxy-D-glucose PET/CT �mages of 222 consecut�ve pat�ents who underwent oncolog�cal PET/CT �mag�ng were used to detect RLRV and CLRV. The numbers and percentages of total left renal ve�n (LRV) var�at�ons, RLRV and CLRV were obta�ned. F�sher's exact test was used to determ�ne the relat�on between the LRV var�at�ons and gender. Results: In the whole group (n=222), the percentages and the numbers of total LRV var�at�ons, RLRV and CLRV were 5.85% (n=13), 2.70% (n=6) and 3.15% (n=7), respect�vely. In male populat�on (n=116), the percentages and the numbers of total LRV var�at�ons, RLRV, and CLRV were 6.03% (n=7), 2.58% (n=3) and 3.45% (n=4), respect�vely. In female populat�on (n=106), the percentages and the numbers of total LRV var�at�ons, RLRV, and CLRV were 5.66% (n=6), 2.83% (n=3) and 2.83% (n=3), respect�vely. The percentages of RLRV and CLRV were found to be �ndependent of gender (P=1.000). Conclusion: PET/CT �s a useful �mag�ng modal�ty �n detect�ng RLRV and CLRV. The relat�onsh�p of gender w�th RLRV or CLRV was not stat�st�cally s�gn��cant.

Hell J Nucl Med 2016; 19(2): 135-139 Epub ahead of print: 22 June 2016 Published online: 2 August 2016

Introduction

Normally a s�ngle left renal ve�n (LRV) crosses anter�or to the abdom�nal aorta before dra�n�ng �nto �nfer�or vana cava (IVC) �n the major�ty of cases. However there are also anatom�cal var�at�ons of LRV, the most common ones be�ng a

retroaort�c left renal ve�n (RLRV) and a c�rcumaort�c left renal ve�n (CLRV) [1, 2]. A RLRV �s a s�ngle LRV wh�ch dra�ns �nto IVC after a retroaort�c course. A CLRV �s a left renal ve�n complex composed of two ve�ns w�th preaort�c and retroaort�c courses wh�ch dra�n �nto the IVC after form�ng a venous collar around the abdom�nal aorta. In var�ous stud�es, a w�de range of percentages of RLRV and CLRV were reported as 0.5%-7.4% and 0.3%-6.3%, respect�vely [1-11].

Detect�on of LRV var�at�ons �s cl�n�cally �mportant for both surg�cal [12, 13] and d�ag-nost�c [14] reasons. Potent�al ser�ous compl�cat�ons can be avo�ded by �dent��cat�on of these ve�ns var�at�ons �n retroper�toneal surgery [3, 13]. Careful evaluat�on of CT �mages �s necessary to d��erent�ate LRV var�at�ons from retroper�toneal lymphadenopathy [14]. Hel�cal CT [2] and mult�detector CT [7, 8] are e��c�ent, fast and rel�able �mag�ng moda-l�t�es �n �dent��cat�on of LRV var�at�ons. Bes�des hel�cal CT and mult�detector CT, pos�t-ron em�ss�on tomography/computed tomography (PET/CT) has also been used to demonstrate RLRV and CLRV [15] but to our knowledge, the present study �s the �rst to report the percentages of RLRV and CLRV found by us�ng PET/CT �mages. We a�med to �dent�fy the most common LRV var�at�ons (RLRV and CLRV), to obta�n the�r percentages and to evaluate the e�ect of gender on the�r frequenc�es, by us�ng PET/CT �mages wh�ch were read�ly obta�ned �n our da�ly pract�ce of oncolog�cal �mag�ng.

Data analysis

Study populat�on

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93 Hellenic Journal of Nuclear Medicine May-August 2016• www.nuclmed.gr135

Between June 2014 and November 2015, PET/CT �mages of 225 consecut�ve pat�ents who underwent rout�ne oncolo-g�cal PET/CT exam�nat�ons for �mag�ng (�n�t�al d�agnos�s of a mal�gnancy, stag�ng of a known cancer, assess�ng tumour response to therapy etc.) were evaluated �n th�s prospect�ve study. Three of them, all male, were excluded. One of the excluded pat�ents had pelv�c ectop�c left k�dney, one had left s�ded IVC (transpos�t�on of IVC) and one pat�ent was very cachect�c, wh�ch made the evaluat�on of LRV �mposs�ble. Our study group (n=222) cons�sted of 116 males and 106 females. The�r mean age was 56.53±14.1 years (range, 16-84 years). All procedures were performed accord�ng to the World Med�cal Assoc�at�on Declarat�on of Hels�nk� (rev�sed �n 2000, Ed�nburgh) [16]. All pat�ents or the�r close relat�ves were �nformed about the PET/CT exam�nat�on procedures, and the�r �nformed consent was obta�ned. S�nce all pat�ents were referred w�th oncolog�cal �nd�cat�ons, pat�ents w�th non-cancerous �nd�cat�ons for a PET/CT study were not �ncluded.

PET/CT protocol and �mage analys�s18Both abdom�nal pla�n CT �mages and rad�olabeled F-FDG

abdom�nal PET/CT �mages were used to detect the two ma�n LRV var�at�ons, RLRV and CLRV. S�nce our a�m was to use only the rout�ne PET/CT �mages wh�ch were read�ly obta�ned for oncolog�cal �mag�ng, we d�d not get any ad-d�t�onal CT �mages for more deta�led or further v�sual�sat�on of LRV var�at�ons, �n order to avo�d any unnecessary rad�-at�on exposure. The pat�ents fasted for at least 6 hours before the study, w�th a plasma glucose level below 150-

18200mg/dL was obta�ned at the t�me of F-FDG adm�n�-18strat�on (mean plasma glucose level, 100mg/dL). The F-

FDG was �njected �ntravenously �n a dose of 259-399.6MBq. Whole-body em�ss�on scann�ng (7-14 bed pos�t�ons; acqu�s�t�on t�me, 3m�n/bed pos�t�on) was performed 50

18m�nutes after F-FDG adm�n�strat�on, the pat�ent ly�ng �n sup�ne pos�t�on. In the major�ty (n=213) of the pat�ents, scann�ng was performed from head to the prox�mal th�gh. The rest of the pat�ents (n=9) were scanned from head to feet. Hybr�d �mag�ng was performed us�ng a D�scovery 610 (General Electr�c Med�cal Systems, LLC, Waukesha, WI, USA) PET/CT scanner. Computed tomography �mages were obta�ned dur�ng breath hold�ng us�ng the follow�ng parameters: detector row con�gurat�on, 16x1.25mm; tube voltage, 120-140kVp; max�mum tube current, 220mA; beam coll�mat�on, 20.0mm; table speed, 27.5mm/rotat�on; p�tch, 1.375:1; hel�cal th�ckness, 3.75mm and 512x512 matr�x. Pr�or to PET/CT exam�nat�on, a solut�on of �od�nated non�on�c contrast mater�al was g�ven orally for bowel opac��cat�on. We d�d not adm�n�ster �ntravenous by �od�nated contrast med�a. Images from PET/CT for each scan were evaluated by a Board-cert��ed nuclear med�c�ne spec�al�st w�th 13 years exper�ence and by a Board-cert��ed rad�olog�st w�th 14 years exper�ence, �n consensus, report�ng together on the same sett�ng. Anatom�c track�ng of LRV through �ts course was performed by follow�ng �t from renal h�lus to IVC un�nterruptedly by us�ng consecut�ve �mages. A s�ngle LRV wh�ch dra�ned �nto IVC after a preaort�c course was accepted as normal LRV (F�gure 1).

Figure 1. Ax�al pla�n CT (A) and fused PET/CT (B) �mages of normal (s�ngle, preaort�c) LRV (wh�te arrows).

A s�ngle LRV wh�ch dra�ned �nto IVC after a retroaort�c course was accepted as RLRV. Double left renal ve�ns wh�ch dra�ned �nto IVC after form�ng a venous collar around abdom�nal aorta w�th preaort�c and retroaort�c courses,

18were accepted as CLRV. Accumulat�on of F-FDG �n left renal pelv�s and �n prox�mal left ureter prov�ded a contrast e�ect to d�st�ngu�sh these structures from adjacent LRV. In order to d��erent�ate the LRV or �ts var�at�ons from the adjacent left renal artery (LRA) and from any detectable accessory LRA, these arter�es were followed un�nter-ruptedly from the�r or�g�ns-most commonly from the left lateral aspect of the abdom�nal aorta to the left k�dney by us�ng consecut�ve �mages. In pat�ents w�th atheroscleros�s, hyperdense atheromatous calc��cat�ons on pla�n CT �mages were used as patholog�c landmarks to detect the or�g�n of LRA.

Stat�st�cal analys�sThe percentages and the numbers of total LRV var�at�ons, RLRV and CLRV were obta�ned. F�sher's exact test was used to determ�ne the relat�on between the LRV var�at�ons (RLRV, CLRV) and gender. P values<0.05 were cons�dered as stat�-st�cally s�gn��cant. All analyses were done w�th SPSS soft-ware (vers�on 16.0; SPSS Inc; Ch�cago, IL, USA).

Results

Regard�ng the whole study group (n=222), the percentages and the numbers of total LRV var�at�ons, RLRV (F�gure 2) and CLRV (F�gure 3) were 5.85% (n=13), 2.70% (n=6) and 3.15% (n=7), respect�vely. In the male populat�on (52.25%, n=116) , the percentages and the numbers of total LRV var�at�ons, RLRV, and CLRV were 6.03% (n=7), 2.58% (n=3) and 3.45% (n=4), respect�vely. In female populat�on (47.75%, n=106), the percentages and the numbers of total LRV var�at�ons, RLRV, and CLRV were 5.66% (n=6), 2.83% (n=3) and 2.83% (n=3), respect�vely. The percentages of both RLRV and CLRV were found to be �ndependent of gender (P=1.000). Descr�pt�ve and percentage �nformat�on about the pat�ents �s g�ven �n Table 1. D�str�but�on of LRV var�at�ons �s g�ven �n Table 2.

D�scuss�on

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93Hellenic Journal of Nuclear Medicine May-August 2016• www.nuclmed.gr 136

Figure 2. Ax�al pla�n CT (A) and fused PET/CT (B) �mages of RLRV (black arrows). Ax�al pla�n CT (a) and fused PET/CT (b) �mages of RLRV (black arrows).

Figure 3. Ax�al pla�n CT (A, C) and fused PET/CT (B, D) �mages of CLRV (wh�te arrows: preaort�c component, black arrows: retroaort�c component).

Subcard�nal ve�ns wh�ch ma�nly dra�n the k�dneys, develop dur�ng the �fth to seventh week of the embryolog�cal per�od and LRV forms as a result of the anastomos�s betwe-en the subcard�nal ve�ns [17]. However, dur�ng the embryolog�cal per�od, var�at�ons of LRV can occur due to the unusual pers�stence or regress�on of these anastomoses: a CLRV results from the pers�stence of both an �ntersub-card�nal anastomos�s anter�or to the aorta (dorsal l�mb of the embryon�c left renal ve�n) and an �ntersupracard�nal anastomos�s poster�or to the aorta (dorsal arch of the renal collar), whereas a RLRV results from the pers�stence of the poster�or �ntersupracard�nal anastomos�s (dorsal arch of the renal collar) w�th regress�on of the ventral arch of �ntersubcard�nal anastomos�s [18, 19].

In the past, �ntervent�onal and more �nvas�ve �mag�ng methods such as renal venography were used to detect LRV var�at�ons [3]. However non-�nvas�ve or relat�vely less �nvas�ve, non-�ntervent�onal modal�t�es are more often used over the last few decades [1, 2, 4-10, 20-22]. Color Doppler ultrasonography can be used to evaluate LRV var�at�ons [5, 21], but �t �s rather operator-dependent, t�me consum�ng and has l�m�ted value �n obese pat�ents [10]. Var�at�ons of LRV can also be demonstrated by us�ng magnet�c resonance �mag�ng (MRI) w�thout expos�ng the pat�ent to �on�z�ng rad�at�on and w�thout adm�n�strat�on of any �ntravenous contrast med�a [1]. However, MRI �s more costly and t�me consum�ng as compared to hel�cal or mult�sl�ce CT [2]. Intravenous contrast-enhanced CT exam�nat�ons w�th hel�cal or mult�sl�ce dev�ces were reported to be the pre-ferred methods �n �dent��cat�on of LRV var�at�ons because of be�ng less costly, less t�me consum�ng, e��c�ent, more pract�cal and w�th h�gh pat�ents' compl�ance [2]. Never-theless, �on�z�ng rad�at�on and potent�al nephrotox�c�ty of contrast med�a st�ll rema�n to be the ma�n unfavourable features of contrast-enhanced CT exam�nat�ons [23, 24]. In our PET/CT stud�es we do not adm�n�ster �ntravenous contrast med�a. Although �on�z�ng rad�at�on or�g�nat�ng

18from �ntravenously adm�n�stered F-FDG and the CT dev�ce �s the major d�sadvantage of PET/CT, �ts use �s �nev�table �n current and common oncolog�cal �mag�ng pract�ce. To �dent�fy LRV var�at�ons �n our or�g�nal study, we �ntended to evaluate the �mages of the pat�ents who already underwent PET/CT �mag�ng for oncolog�cal purposes, w�thout perform�ng any further �mag�ng study wh�ch would �ncrease the rad�at�on burden for the pat�ent.

By us�ng PET/CT both morpholog�cal and funct�onal data can be obta�ned �n oncolog�cal �mag�ng. However, one should be aware of some d�agnost�c p�tfalls �n PET/CT �mages. A thrombosed RLRV can m�m�c a retroper�toneal neoplasm [25] so �f one �s fam�l�ar w�th LRV var�at�ons may avo�d m�sd�agnos�s. Furthermore, �n pat�ents w�th sol�d tumours, evaluat�on of LRV on PET/CT �mages has cl�n�cal �mportance �n d�agnos�ng a poss�ble tumour thrombus �n th�s ve�n [26]. Co�nc�dental patholog�es such as nutcracker syndrome can also be detected on PET/CT �mages [27]. Bes�des these patholog�cal �nd�ngs, normal anatom�c var�at�ons of LRV can also be �dent��ed by PET/CT �n cancer pat�ents [15, 28]. The left paraaort�c reg�on �s a common locat�on of normal vascular and other anatom�c structures wh�ch may m�m�c tumours on CT �mages [29]. Wh�le evaluat-

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A B

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Table 1. Descr�pt�ve and percentage �nformat�on about the pat�ents

Gender Females Males

Number 106 116

Percentage (%) 47.75% 52.25%

Age (Mean±Standard Deviation)

53.75±13.68 years

59.08±14.09 years

Table 2. D�str�but�on of LRV var�at�ons

Females Males P values*

Total LRV 5.66% 6.03% 1.000

RLRV 2.83% 2.58% 1.000

CLRV 2.83% 3.45% 1.000

*P values < 0.05 were considered as statistically signicant.

93 Hellenic Journal of Nuclear Medicine May-August 2016• www.nuclmed.gr137

ing these locat�ons w�th PET/CT, the LRV var�at�ons should be taken �nto cons�derat�on to avo�d m�sd�agnos�s. Further-more, these var�at�ons should be reported because may be useful for treatment plann�ng, such as to decrease the number of �mproperly pos�t�oned IVC �lters �n treat�ng cancer pat�ents [28]. Be�ng �nformed about the LRV var�a-t�ons before perform�ng retroper�toneal surgery �s very �mportant for a surgeon to avo�d any �njury to these struc-tures, to prevent subsequent hemorrhage and poss�ble death [9, 13, 30]. The pat�ents who undergo PET/CT for oncolog�cal �mag�ng are cand�dates for many of the above ment�oned r�sky �ntervent�onal procedures. In our study,

18patholog�cal F-FDG uptake of metastat�c retroper�toneal lymph nodes helped us to d�st�ngu�sh LRV and �ts var�at�ons wh�ch was surg�cally �mportant for the pat�ents who would undergo retroper�toneal lymph node/mass b�opsy or sur-gery. We cons�der that the results we obta�ned from our study w�ll emphas�ze the �mportance of �dent�fy�ng and report�ng the LVR var�at�ons �n these pat�ents.

S�nce our study was based on the evaluat�on of PET/CT �mages wh�ch were read�ly obta�ned �n our da�ly pract�ce of oncolog�cal �mag�ng, we d�d not use MRI or CT ang�ography for compar�son. Several stud�es were conducted w�th CT or CT ang�ography �n order to obta�n the percentages of LRV var�at�ons [2, 4, 8-11]. In a study w�th mult�detector CT an-g�ography, total LRV var�at�ons were detected �n 68 (3.6%) of the 1856 pat�ents [10]. In a newer study w�th the same modal�ty ment�oned above, the percentages of RLRV and CLRV were 2.1%, 30/1452 and 2.1%, 31/1452, respect�vely [8]. By us�ng rout�ne abdom�nal CT scans, LRV var�at�ons were �dent��ed �n 23 (3.1%) of 739 cases [11]. In a large-scale study w�th contrast-enhanced abdom�nal hel�cal CT [2], the percentages of the total LRV var�at�ons, RLRV and CLRV were reported as 5.2%, 3.1%, and 2.1%, respect�vely. Though we d�d not use �ntravenous contrast med�a, the percentages that we obta�ned ut�l�z�ng PET/CT are close to those of above ment�oned contrast-enhanced stud�es. Our results are also comparable to those obta�ned by us�ng MRI [1], �n wh�ch the percentage of total LRV var�at�ons was reported as 2.68%. Our results are also w�th�n the range stated �n an analys�s of a vast range of percentages obta�ned from several stud�es [3]. Regard�ng the poss�ble unfavourable surg�cal and cl�n�cal outcomes, these var�at�ons were not thought be �rare� [1]. After evaluat�ng our results and those obta�ned from prev�ous stud�es w�th other �mag�ng modal�t�es, we cons�der that abdom�nal PET/CT �mages can be used �n the �dent��cat�on of LRV var�at�ons. Thus, we recommend to look for and report these var�at�ons �n da�ly PET/CT pract�ce.

In �mag�ng stud�es performed w�th CT [4, 7, 8] and MRI [1], no s�gn��cant relat�onsh�p between gender and LRV var�at�ons was reported as �n the present study for the most common var�at�ons of RLRV and CTRV.

Because a relat�vely l�m�ted number of pat�ents popu-lat�on could be recru�ted dur�ng the 18 months study per�od and s�nce �ntravenous contrast-enhanced CT or CT anj�o-graphy �mages were not obta�ned dur�ng our PET/CT pract�ce, we could not clearly �dent�fy other types of LRV var�at�ons, d��erent from RLRV and CLRV. Th�s can be ac-cepted as a l�m�tat�on of our study. We suppose that further

stud�es w�th PET/CT �nclud�ng larger and d��erent pat�ent groups w�ll follow. We cons�dered that the number of our pat�ents was su��c�ent to demonstrate the usefulness of PET/CT �n �dent�fy�ng these two most frequent, cl�n�cally �mportant LRV var�at�ons. Us�ng all consecut�ve �mages, careful track�ng of LRV un�nterruptedly-from renal h�lus to IVC-helped us to �dent�fy RLRV and CLRV correctly. The lack of �ntravenous contrast mater�al was part�ally compansated

18by F-FDG accumulated �n left renal pelv�s and �n prox�mal left ureter, wh�ch had a contrast e�ect s�m�lar to �od�nated contrast med�a �n the pyelogram phase and helped us d�st�ngu�sh these structures from adjacent LRV. In each case, LRA was also followed from abdom�nal aorta to left renal h�lus �n order to d��erent�ate �t from LRV. In ava�lable pat�ents, hyperdense atheromatous calc��cat�ons were also helpful �n determ�n�ng the or�g�n and course of renal arter�es.

In conclus�on, accord�ng to the results of our or�g�nal paper, rout�ne abdom�nal PET/CT �mages are useful �n detect�ng RLRV and CLRV. The relat�onsh�p of gender w�th RLRV or CLRV was not stat�st�cally s�gn��cant.

The authors declare that they have no con�icts of interest

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Original Article

Antonio Casanova. Nurse and patient, 1893. Oil in wood, 12x21cm, private collection.

93 Hellenic Journal of Nuclear Medicine May-August 2016• www.nuclmed.gr139