825

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Intestinal

Diagnosis Malrotation

of in Infants:

Importance of the Relative Positions Superior Mesenteric Vein and Artery

Ed Weinberger1 William D. Winters Robert M. Liddell David M. Rosenbaurn Dale Krauter

OBJECTIVE.

An abnormal

relative

position

of the superior

of the

mesenteric

vein and artery

can be present in patients with intestinal malrotation. We undertook this retrospective study to see how often we could determine the relative position of these vessels on

abdominal

sonograms

associated

with malrotation.

in infants

and how often

abnormal

position

of the vessels

was

MATERIALS AND METHODS. We reviewed the radiology files and medical records of 337 infants with vomiting who were referred for sonography because of possible pylonc stenosis. We used sonograms and written reports to determine the position of the superior mesenteric vessels. The position was considered normal when the superior mesenteric vein was to the right of the superior mesenteric artery on transverse sonograms. The position was considered abnormal when the vein was directly ventral to the artery or when the vein was to the left of the artery. Sonographic findings were compared with results of upper gastrointestinal series when possible and with clinical outcome. RESULTS. The relative positions of the superior mesenteric vein and artery were evident in 249 (74%) of the 337 patients. Abnormal orientation of the mesenteric vessels was detected in nine patients. In five patients, the superior mesenteric vein was located to the

left

of

the

artery,

and

all

five

had

intestinal

malrotation.

In four

patients,

superior mesenteric vein was directly ventral to the artery, and one of malrotation. CONCLUSION. Sonographic assessment of the relative positions of the artery and vein is an important adjunct in the examination of infants with pyloric stenosis. Patients in whom sonograms show an abnormal position of should have further examination to detect malrotation. AJR

159:825-828,

October

the

these

had

mesenteric suspected the vessels

1992

Abnormal orientation of the superior mesenteric vessels has been reported in patients with intestinal malrotation [1 -5] with the superior mesenteric vein (SMV) immediately ventral (anterior) to the superior mesenteric artery (SMA), or the SMV to the left of the SMA.

assessment for infants

Received February vision April 13, 1992. sity

26, 1992; accepted after re-

‘All authors: Departments of Washington, School

WA 98195, Center,

98105.

and Children’s

of Radiology, of Medicine,

Hospital

UniverSeattle,

During

of the positions having sonography

the past

several

years,

we have

included

sonographic

of the SMA and SMV as part of our routine workup because of possible pyloric stenosis. We undertook

this retrospective study to see how often an abnormal orientation of the SMV and SMA could be detected in these infants and how often such an abnormal orientation was associated with intestinal malrotation. Because intestinal malrotation can become a life-threatening emergency if the common complications of obstruction by Ladd’s diagnosis

bands or midgut volvulus are not detected of this disorder is important.

Materials

and

and treated

promptly,

early

and Medical

4800 Sand Address

at Children’s

Point Way, N.E., Seattle, WA reprint requests to E. Weinberger

Hospital and Medical Center.

0361-803X/92/i 594-0825 CAmencan Roentgen Ray Society

During

because

a

21/2

Methods year period,

of suspected

pyloric

343 patients stenosis.

at our hospital Ten

patients

had

had 353 sonographic two

examinations

examinations (the

second

one

826

usually

WEINBERGER

after

surgery

for pyloric

stenosis),

and the results

ET AL.

AJR:159,

October

1992

of these

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second examinations were excluded from our study. Six patients’ sonograms or charts were unavailable for review, and these patients also were excluded. The remaining 337 sonographic studies in 337 patients formed the basis of our investigation. We follow a standard technique for sonographic examination of the abdomen [6]. We also attempt to visualize the SMV and SMA by placing the transducer

ventral to the mesenteric vessels and assessing their orientation as far caudal to the confluence of the portal and splenic veins as possible. The position of the SMV was considered normal when the vein was located laterally to the right of the SMA. The position was considered abnormal when the vein was located ventral to or laterally to the left of the SMA. Patients of the vessels were

whose sonograms showed that the positions abnormal then had an upper gastrointestinal

series. At our hospital,

an upper gastrointestinal

series is the proce-

dure of choice

for an infant with suspected malrotation, both. Sonography is the first and usually the only imaging

when pyloric

stenosis

when the clinician wants nonbilious vomiting.

For our retrospective

is suspected

because

to rule out pyloric

of clinical findings

stenosis

in an infant

or with

study, the radiology files and medical records

of all 337 patients were reviewed. All of the sonograms were reviewed and compared with the written report of the study with regard to the positions of the SMV and the SMA.

The study population the patients

stenosis,

was

.

Fig. 1.-24-day-old

boy who had nonbillous

(range,

2-21 8 days);

patients

had no evidence

the SMA,

Results

showed

The relative positions of the SMV and SMA were evident from the sonograms or the written reports in 249 (74%) of 337 patients. In 56 patients (1 7%), bowel gas prevented adequate visualization of the vessels. In 32 patients (9%), neither the sonograms nor the written report included mention of the vessels (26 of these 32 patients had pyloric stenosis, so the examination may have been abbreviated). Abnormal orientation of the mesenteric vessels was detected in nine of the 249 patients in whom the relationship of the vessels could be evaluated. In five of these patients, the SMV was located to the left of the SMA; all five had intestinal malrotation. One patient had had surgery for malrotation and midgut volvulus (results of an upper gastrointestinal series confirmed malrotation but without obstruction). One patient had had repair of a gastroschisis on the day of birth and had pyloric stenosis (Fig. 1). The other three patients had unmalrotation

confirmed

by

series

tion (Fig. 3).

In four of the patients, the SMV was ventral to the All four patients had upper gastrointestinal series. One four had malrotation and obstruction due to Ladd’s and had immediate surgical repair (Fig. 4). (A history of not known review

at the time of sonography, of this

patient’s

medical

SMA. of the bands bilious

was noted chart.)

in

Another

had small-bowel obstruction as a result of adhesions from previous surgical repair of an inguinal hernia. The other two

of malrotation

and are clinically

by upper

in whom the SMV was to the right of

37 (1 5%) had upper

no evidence

as shown well.

gastrointestinal

series,

which

of malrotation.

Discussion

Intestinal embryologic

mairotation encompasses a wide spectrum of failures of rotation and fixation of the gut, result-

ing in a narrow-based

presence sent

of abnormal

indirect

predispose

attempts

attachment peritoneal at fixation

to midgut volvulus

of the mesentery and the (Ladd’s) bands that repre[4].

These

and obstruction.

abnormalities

Although

most

patients have bilious vomiting and signs of obstruction in the first few months of life [7-9], some may remain asymptomatic

or have atypical clinical findings that may be misleading [4, 9]. In this last group of patients, earlier diagnosis might prevent complications of malrotation, including bowel ischemia, necrosis, and death. We were able to detect intestinal malrotation correctly

subsequent

upper gastrointestinal series. Two of these had obstruction due to Ladd’s bands and had immediate surgical repair (Fig. 2); one had microgastria and had malrotation without obstruc-

retrospective

for 36

127 had pylonc

Of the 240 patients

vomiting,

vomiting

chisis on day of birth.

gastrointestinal

intestinal

projectile

hr. Transverse sonogram shows superior mesenteric vein (v) to left of superior mesentenc artery (a). Lumen of superior mesenteric artery can be recognized by surrounding rim of echogenicity. Note thick pyloric muscle (arrowheads). Patient had pyloromyotomy for pyloric stenosis. Intestinal malrotation was substantiated during surgical repair of gastros-

included 239 boys and 98 girls. Mean age of

6.6 weeks

and 2i 0 did not.

suspected

i_u

volvulus, or study done

on sonograms

in four patients

in whom

this problem

was not suspected, and in only one of these patients did a review of the chart suggest bilious vomiting. In 1983, Nichols and Li [1] described three adults in whom CT showed that the SMV was located on the left ventral aspect of the SMA instead of the right ventral aspect. They termed this finding the “SMV rotation sign”; upper gastrointestinal examinations showed various degrees of intestinal malrotation in all three patients. In 1 986, Blumhagen and

Weinberger [2] detected the same abnormal position of the two vessels on sonograms of a 15-year-old girl with intestinal malrotation. In 1987, Gaines et al. [3] showed sonographically that the SMV was located directly anterior to or to the left of

INTESTINAL

AJR:159, October 1992

MALROTATION

:

;).e.s:’4P1

:

827

#{149}:‘w’ .w.

.

-.

IN INFANTS

.

-

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‘U.

Fig. 2-18-day-old boy who had intermittent nonbilious vomiting for 48 hr. A, Transverse sonogram below level of confluence of splenic and portal veins shows mesenteric vein (v) at left lateral aspect of superior mesenteric artery (a). ao = aorta, i vena cava. B, Sonogram

shows

intermittent

distension

of duodenum

After upper gastrointestinal Ladd’s bands.

series, surgery confirmed

the SMA

and two adults

in three

children

b

=

duodenal

known

malro-

=

bulb.

with obstruction

boy with emesis.

Trans.

by

tation, as shown by previous upper gastrointestinal series. Gaines et al. also suggested the diagnosis of malrotation on the basis of sonographic findings in an 1 i-year-old child in whom abnormal orientation of the mesenteric vessels was discovered during sonography done because of urinary tract infection. These studies, as well as ours, suggest that using sonography to evaluate the relationship between the SMV

scans showed that the SMV was to the left of the SMA but in whom upper gastrointestinal series did not show malrotation. Conversely, normal orientation of mesenteric vessels (SMV to the right of SMA) does not ensure normal intestinal rotation, even though this was seen in our patients who had subsequent upper gastrointestinal series. Leiberman and Haaga [1 1 ] described a patient with malrotation shown by upper gastrointestinal series in whom CT scans showed

and the SMA may be helpful intestinal malrotation.

normal orientation of mesenteric vessels. Finally, the finding of the SMV directly ventral to the SMA is probably indeter-

in the diagnosis

with

by fluid.

intestinal malrotation

Fig. 3.-b-day-old

verse sonogram just below level of confluence of splenic and portal veins shows superior mesentenc vein (v) at left ventral aspect of superior mesenteric artery (arrowhead). so = aorta, s = spine. Upper gastrointestinal series showed malrotation and microgastna.

superior inferior

of unsuspected

Malrotation was present in all our patients in whom the SMV was located to the left of the SMA; and although this seems to be the rule [1 -5], it is not always the case. Zerin and DiPietro [1 0] described a 20-year-old patient in whom CT

minate

for

malrotation;

one

of our

vascular relationship had malrotation. scan farther caudally in the patients might have found more inferiorly.

that the SMV

four

patients

with

this

If we had been able to without malrotation, we

was to the right

of the SMA

Sonographic assessment of the orientation of mesenteric vessels must be done with great care. Two important points in technique are worth mentioning. First, scanning must be

done as far caudally as possible from the confluence of the splenic and portal veins, because at this level the SMV may be almost directly ventral to the SMA, resulting in an incorrect diagnosis Fig.

4.-Trans-

verse

sonogram superior mesenteric vein (v) ventral to superior mesenteric artery shows

(arrowhead).

Upper

gastrointestinal sers showed duodenal obstruction. At surgery, malrotation with Ladd’s bands was found.

of abnormal

orientation

of mesenteric

vessels.

Sec-

ond, the transducer must be placed in the midline directly anterior to the vessels in order to assess orientation correctly. As the vessels may be obscured by gas, it is often tempting to move the transducer to the right of midline to use the liver as an acoustic window. This, however, results in the SMV appearing to have a more leftward or clockwise orientation with

respect

to the SMA,

resulting

in an incorrect

of abnormal orientation. We do not think that sonography gastrointestinal

examination

for

the

should diagnosis

diagnosis

replace

upper

of intestinal

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828

WEINBERGER

malrotation. Rather, sonographic assessment of the relationship of the mesenteric vessels may provide useful information in patients with intestinal malrotation who are asymptomatic or have atypical signs and symptoms. Specifically, our study suggests that sonographic assessment of the relationship of the mesenteric vessels is an important adjunct in the evaluation of the young child who has signs suggestive of pyloric stenosis. When the position of the SMV with respect to the SMA is abnormal, further evaluation via an upper gastrointestinal series is warranted. REFERENCES 1 . Nichols DM, Li DK. Superior mesentenc malrotation. AJR i983;1 41:707-708

2. Blumhagen JD, Weinberger In: 5anders 1986:99-140

RC,

Hill

M,

vein rotation: a CT sign of midgut

E. Pediatric gastrointestinal eds.

Ultrasound

annual.

ultrasonography. New York: Raven,

ET AL.

3. Gaines

AJR:159, October 1992

PA, Saunders

AJS,

Drake D. Midgut :51-53

ultrasound. Clin Radiol i987;38 4. Loyer E, Eggli KD. Sonographic relationship

in malrotation.

malmotation

diagnosed

by

evaluation of superior mesentenc vascular

Pediatr

Radiol

i989;19:

173-175

5. Shatzkes 0, Gordon DH, HaIler JO, Kantor A, DeSilva A. Malrotahon of the bowel: malalignment of the superior mesentenc artery-vein oomplex shown by CT and MR. J Comput Assist Tomogr i990;14:93-95 6. Blumhagen JD, Macun L, Krauter D, Rosenbaum DM, Weinberger E. Sonographic diagnosis of hypertrophic pyloric stenosis. AJR i988;1 50: 1367-1370 7. Stewart

DR, Colodny

AL, Daggett

WC. Malrotation

of the bowel

in infants

and children: a 15 year review. Surgery 1976;79 :716-720 8. Andrassy RJ, Mahour GH. Malmotation of the midgut in infants and children: a 25-year review. Arch Surg i98i;1 16:158-160 9. Spigland N, Brandt ML, Ya.zbeck S. Malmotation presenting beyond the neonatal period. J Pediatr Surg i990;25: 1139-1142 10. zenn JM, DiPietro MA. Mesenteric vascular anatomy at cT normal and abnormal appearances. Radiology i99i;179:739-742 1 1 . Lieberman JM, Haaga JR. Duodenal malrotation. J Comput Assist Tomogr 1982;6: 101 9-1 020