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European Journal of Radiology 83 (2014) 710–714

Contents lists available at ScienceDirect

European Journal of Radiology

j ourna l h o mepage: www.elsev ier .com/ locate /e j rad

nticlockwise swirl of mesenteric vessels: A normal CT appearance,etrospective analysis of 200 pediatric patients

ushaljit S. Sodhia,∗, Anmol Bhatiaa,1, Akshay K. Saxenaa,1, Katragadda L.N. Raob,2,rema Menonb,2, Niranjan Khandelwala,1

Department of Radiodiagnosis and Imaging, Post Graduate Institute of Medical Education and Research, Sector-12, Chandigarh 160012, IndiaDepartment of Pediatric Surgery, Post Graduate Institute of Medical Education and Research, Sector-12, Chandigarh 160012, India

r t i c l e i n f o

rticle history:eceived 5 November 2013eceived in revised form3 December 2013ccepted 27 December 2013

eywords:nticlockwisewirlesenteric

essels

a b s t r a c t

Objective: The counterclockwise rotation of the SMV on SMA is a normal and non-specific finding, whichresults in an incomplete swirl formation on CT scans. However, it has a potential to be misinterpreted as‘midgut volvulus’ resulting in serious clinical implications. The study was done to determine the frequencyand degree of counterclockwise rotation of the SMV on SMA on CT in normal otherwise asymptomaticpediatric patients undergoing CT scan.Methods: In this IRB approved study, we retrospectively analyzed abdominal CT scan examinations of200 consecutive pediatric patients (age range of 11 days to 18 years), which were performed for differentclinical indications over a period of 10 months. They were evaluated for the absence or presence anddegree of counterclockwise rotation of the mesenteric vessels.Results: Of the 200 patients, 128 (64%) patients showed no clockwise or anticlockwise rotation of mesen-

alrotationomputed tomographyhildren

teric vessels. Counterclockwise rotation of SMV on SMA was seen in 72 (36%) patients. Further, the degreeof rotation of vessels was also calculated, based on the criteria proposed by the authors.Conclusions: The counterclockwise rotation of SMV on SMA gives an appearance of mesenteric whirlpoolin otherwise normal mesenteric vessels and can be misinterpreted as midgut volvulus. It is a normal CTappearance and is due to a variation in branching pattern of mesenteric vessels. Awareness of this normalbranching pattern of mesenteric vessels is important to avoid an inadvertent laparotomy.

. Introduction

Midgut malrotation results from errors of rotation and fixationf bowel loops. It occurs in 1 in 500 live births and is one of theommon causes of intestinal obstruction in neonates [1]. However,t can be seen even in adolescents and adults [1]. Midgut volvu-us may result in fatal complications and sequelae in nearly 50% ofases. The initial symptoms seen in malrotation with acute volvu-us usually include intractable abdominal pain and bilious vomiting.ssociated complaints of fever, abdominal tenderness and leuko-ytosis may point toward the gangrenous changes. Bowel gangrene

nd perforation can occur due to prolonged volvulus and strangu-ation which is a life-threatening surgical emergency. Perforation

∗ Corresponding author. Tel.: +91 172 2756381; fax: +91 172 2745768.E-mail addresses: sodhiks@gmail.com (K.S. Sodhi), anmol bhatia26@yahoo.co.in

A. Bhatia), fatakshay@yahoo.com (A.K. Saxena), klnrao@hotmail.com (K.L.N. Rao),enonprema@hotmail.com (P. Menon), khandelwaln@hotmail.com

N. Khandelwal).1 Tel.: +91 172 2756381.2 Tel.: +91 172 2755320.

720-048X/$ – see front matter © 2014 Elsevier Ireland Ltd. All rights reserved.ttp://dx.doi.org/10.1016/j.ejrad.2013.12.026

© 2014 Elsevier Ireland Ltd. All rights reserved.

of the bowel can lead to peritonitis [1,2]. Hence, it is important todiagnose malrotation/volvulus at the earliest.

Imaging plays an important role in diagnosis of intestinal malro-tation with volvulus. An upper gastrointestinal contrast study usinga water-soluble contrast agent is the standard modality for diag-nosing malrotation and volvulus, where oral contrast medium doesnot pass beyond the duodenum. Furthermore, a typical corkscrewappearance may be seen,however, it is seen in less than 50% ofall cases. Computed tomography (CT) signs of midgut malrota-tion include inverted transposition of SMA and SMV, rotation ofthe superior mesenteric vein (SMV) around the SMA described aswhirlpool or concentric circle sign, horizontal part of duodenumnot reaching medioventral line or just reaching but encircled rightdown behind superior mesenteric artery (SMA), jejunal loops inright middle abdomen while ileum on the left side, and an ectopicileocecal junction [3,4].

Normally, the SMV lies to the right of SMA and its tributariescourse anteriorly to the SMA in a clockwise fashion on consecutive

CT images seen from cranial to caudal direction. The counterclock-wise rotation giving a whirlpool appearance is described in casesof midgut malrotation. However, counterclockwise rotation of SMVaround SMA is a normal and non-specific finding, and can be seen in

nal of Radiology 83 (2014) 710–714 711

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Table 1Categorization of the patients (n = 200) in different groups and subgroups based onrotation of rotation of mesenteric vessels.

Groups Number of patients (%)

Ia 128 (64%)IIb 72 (36%)IIAc 24 (33.3%)IIBd 24 (33.3%)IICe 24 (33.3%)

a Normal mesenteric vessels without any counterclockwise rotation.b Counterclockwise rotation of SMV around SMA.

An upper gastrointestinal contrast study series with a water-soluble contrast agent is the standard modality for diagnosingmalrotation and volvulus [1,9]. When volvulus occurs, there maybe partial or complete duodenal obstruction. A beaked tapering of

Table 2Distribution of associated intraabdominal pathologies in Group II patients.

Pathologies Groups

IIA IIB IIC

K.S. Sodhi et al. / European Jour

ormal patients [5,6]. This finding should not be misinterpreted as aartial or incomplete midgut volvulus. The aim of this study was toetermine the frequency and degree of counterclockwise rotationf SMV around SMA on abdominal CT scans in pediatric populationnd to highlight its occurrence in otherwise normal asymptomatichildren.

. Materials and methods

This study was approved by our institution’s Internal Reviewoard. The requirement for informed consent was waived. Abdom-

nal CTs of 200 pediatric patients between October 2012 and august013, done for the different clinical indications (trauma, tumors,

nfection and inflammatory pathologies) were retrospectively ana-yzed. None of the CT scans had been performed for a suspected

alrotation or volvulus. All patients had also undergone abdomi-al ultrasound 1–10 days prior to CT scan, which did not show theresence of volvulus.

All the CT scans were performed on 64 detector Toshiba Aquilon4 scanner. Of the 200 patients in the study group, there were17 (58.5%) males and 83 (41.5%) females. The age range of theatients was 11 days to 18 years. The kVp ranged from 80 (in 11ays child) to 120 (in 18 years old patient). The milli-amperagemA) was between 60 (in 11 days child) and 200 (in 18 yearsld patient). The pitch used was 0.828. 750–1500 ml of oral con-rast was used followed by intravenous contrast @1.5–2 ml/kg bodyeight, as per our departmental protocol for CT abdomen in pedi-

tric population. Use of oral contrast depends on the indicationnd age of the patient. The studies were evaluated on the worktation (Aquarius intuition edition, version 4.3 from Tera Reconnc.). The images were evaluated by two pediatric radiologistsy consensus. Both the radiologists had more than 10 years ofxperience in pediatric radiology. Clockwise and counterclockwiseotation was used to describe the route of mesenteric vein dur-ng the evaluation of the consecutive images from cranial to caudalirection.

The patients in our study were divided into two groups as fol-ows:

Group I: Normal mesenteric vessels without any counterclockwiserotation.Group II: Counterclockwise rotation of SMV around SMA.

The group II studies were further evaluated for the degree ofounterclockwise rotation of SMV around SMA and categorized asollows:

Group A: >90◦ to <180◦ counterclockwise rotation of SMV aroundSMA (Fig. 1a).Group B: >180◦ to <270◦ counterclockwise rotation of SMV aroundSMA (Fig. 1b).Group C: >270◦ counterclockwise rotation of SMV around SMA(Fig. 1c).

The group II studies were also evaluated for the presence ofny abdominal pathologies which could potentially increase therobability or the degree of counterclockwise rotation of SMVround SMA. These included the intra-peritoneal or retroperitonealolid/cystic lesions, mesenteric lesions and ascites. Unilateralesions were further categorized as either right sided or left sidedausing mass effect on the mesentery, thereby probably distorting

he normal anatomical arrangement of vessels.

A descriptive analysis of the results was done and number ofatients belonging to different groups and subgroups expressed inercentages.

c >90◦ to <180◦ counterclockwise rotation of SMV around SMA.d >180◦ to <270◦ counterclockwise rotation of SMV around SMA.e >270◦ counterclockwise rotation of SMV around SMA.

3. Results

3.1. CT findings

Table 1 summarizes the categorization of the patients in two dif-ferent groups according to absence or presence of counterclockwiserotation. Further categorization of group II patients (Fig. 2) basedon the degree of counterclockwise rotation is also summarized inTable 1.

Of the 72 patients belonging to group II, 16 (22%) patients werefound to have associated intraabdominal pathologies which couldpossibly lead to an increase in the degree of counterclockwise rota-tion, thereby changing the group division. Table 2 summarizes theassociated abdominal pathologies in patients (n = 16) belonging togroup II which could have possibly lead to an increase in the degreeof counterclockwise rotation.

4. Discussion

Midgut malrotation is a congenital anomaly which occurs dueto errors in rotation of gastrointestinal tract around the SMA andfixation of the bowel during development. It occurs in 1 in 500 livebirths and is recognized as one of the common causes of intestinalobstruction in neonates with a male predominance [1,2]. Approxi-mately 75% of all cases eventually develop volvulus, of which 75%present within the first month of life [1].

A 270◦ counterclockwise rotation of the midgut at the tenthweek of life results in the normal adult position of duodenumbehind SMA with the transverse colon seeing crossing anteriorly.The duodenum gets fixed to retroperitoneum at the ligament of Tre-itz, while cecum becomes fixed in the right lower quadrant [1,7,8].In cases of mixed rotation, duodenum descends to the right of thespine, and the colon tends to lie below the antropyloric region.Ladd’s bands, which are firm and fibrous adhesions fix the cecumand ascending colon to abdominal wall. These fibrous adhesionscan lead to kinking or compression of the second part of duode-num. Furthermore, active peristalsis leads to twisting of the unfixedsmall bowel and ascending colon leading to volvulus [1].

Left renal mass – – 5Right renal mass – 3 –Ascites 1 2 2Mesenteric cysts – 3 –

712 K.S. Sodhi et al. / European Journal of Radiology 83 (2014) 710–714

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Fig. 1. Schematic images showing the anticlockwise rotation of SMV (b

bstructed duodenum is seen in complete obstruction. The pathog-omonic corkscrew pattern of the twisted duodenum and jejunum

s seen due to their clockwise twisting around SMA, however isemonstrated in less than half of all cases on these studies [1,10].

The “whirlpool sign”, first described in a case of midgut volvulusy Fisher on CT scan is created by small bowel loops encircling theMA [11]. The SMA is closely wrapped by clockwise coils of the bow-ls and mesentery-embedded SMV resulting in multiple concentric

ircles on cross-sectional imaging. This “whirlpool sign” has beenescribed as pathognomonic for midgut malrotation with volvu-

us in pediatric patients in a few studies [11,12]. This “whirlpoolign” however can result due to counterclockwise rotation of SMV

ig. 2. Axial CT images of the patients showing the anticlockwise swirl of SMV around SM).

round SMA (red) of >90◦ to <180◦ (a), >180◦ to <270◦ (b) and >270◦ (c).

around SMA. This finding was first highlighted as a normal variantin a child with normal intestinal rotation in 2005 [5]. It occurs dueto a proximal jejunal branch of the SMV which before joining themain SMV, circles in a counterclockwise fashion between SMA andaorta (Fig. 3). It was reported to be present in 10% of normal controlpatients by Taylor GA in his study performed in 138 patients (100patients without malrotation and 38 with proven malrotation) todetermine whether a retroperitoneal third duodenal segment can

reliably exclude malrotation [6]. The counterclockwise rotation inour study was found in 36% of the patients and none of our patientsprior to CT had a clinico-sonological profile suggestive of malrota-tion/volvulus (ultrasound abdomen performed 1–10 days prior to

A belonging to group IIA (>90◦ to <180◦ , a), IIB (>180◦ to <270◦ , Bb) and IIC (>270◦ ,

K.S. Sodhi et al. / European Journal of Radiology 83 (2014) 710–714 713

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ig. 3. Consecutive axial thick maximum intensity projection images (cranial to cahe proximal jejunal tributary (black arrows) of SMV around SMA.

he CT scan did not report any definite volvulus or altered SMA-SMVxis). Zerin et al. [13] described various anatomic relations betweenMV and SMA in patients with and without mesenteric inversions.ll of the patients belonging to group II in our study showed theattern similar to patients with mesenteric inversion described byerin et al. Hence, this finding should not be misinterpreted as aartial or incomplete midgut volvulus.

Some authors have proposed that whirlpool sign, although anding highly suggestive of volvulus, can occur in any situation thatroduces rotation or twisting of bowel and its mesenteric attach-ent [14]. In our study, abdominal pathologies were encountered

n 16 patients of group II which could have possibly increased theegree of counterclockwise rotation, but was actually not true inll cases as right sided masses were also seen in three patients withroup IIB rotation (counterclockwise rotation of >180◦ to <270◦).e feel that, though displacement can occur because of abdominal

athologies, it is difficult to explain the rotation or whirl in patientsith right sided lesions in abdomen.

Midgut volvulus is known to produce fatal complications andequelae in nearly 50% of cases. Intractable abdominal pain andilious vomiting are usually the initial symptoms seen in malrota-ion with acute volvulus. Associated complaints of fever, abdominalenderness and leukocytosis may point toward the gangrenoushanges. This needs surgical exploration on an emergency basis1,2]. None of the patients in our study had any such complaintsr findings which could possibly point to presence of malrotationith volvulus.

There are a few limitations in our study. The first one is a rel-

tively small study group for such an anatomical description ofariants of branching pattern of abdominal vessels. We proposeurther studies with a large sample population. The second and

ore important limitation is that though none of our patients

a–c) of a patient belonging to group IIC showing the counterclockwise rotation of

had undergone CT for malrotation, we have no surgical proof thatour patient population had normal intestinal rotation. Ideally, ofcourse contrast study is diagnostic for malrotation/volvulus. How-ever, gastrointestinal contrast study was not done in any of thesechildren as there was no clinico-sonological profile indicative ofmalrotation/volvulus. Ultrasound abdomen performed 1–10 daysprior to CT also did not report any definite volvulus or alteredSMA-SMV axis. Another limitation is inclusion of patients withintraabdominal pathologies which could possibly increase thedegree of counterclockwise rotation. This has possibly led to anunusual equality of the number (n = 24) of patients in each subgroupof group II patients.

To conclude, the whirlpool sign refers to clockwise rotationof the bowel and SMV about the SMA and a counterclockwisewhirlpool appearance may be seen, but does not represent abnor-mality. This counterclockwise appearance can be misinterpreted asmidgut volvulus. It is important for radiologists to be aware of thisnormal CT appearance of mesenteric vessels, which can be seenin up to one-third of normal population to avoid an unnecessarylaparotomy and avoid the increasing load of additional radiologicalinvestigations in the present era.

Conflicts of interest

The authors have no conflicts of interest to declare.

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