Clinical Radiology (1987) 38, 51-53

Midgut Malrotation Diagnosed by Ultrasound P. A. GAINES, A. J. S. SAUNDERS and D. DRAKE*

Department of Diagnostic Radiology and *Department of Paediatric Surgery, Guy's Hospital, London, SE1 9RT

Ultrasound was used to demonstrate the abnormal orien- tation of the mesenteric vessels in six cases of midgut malrotation. Five of these patients were known to have an abnormality of rotation before the ultrasound scan. In one patient malrotation was predicted from the ultra- sound scan and confirmed by a barium study and at operation.

Midgut malrotation is a potentially lethal condition usually presenting as small bowel obstruction in the neonate. Occasionally the presentation is atypical or the conventional barium examination difficult to interpret. Nichols & Li (1983), using computed tomography, demonstrated an anomalous alignment of the mesen- teric vessels in midgut malrotation. The superior mesen- teric vein was seen to lie on the left ventral aspect of the superior mesenteric artery rather than the right ventral aspect. This prompted us to study our recent cases of malrotation using ultrasound.

METHOD AND RESULTS

Five patients with malrotation of the midgut already diagnosed by an upper gastro-intestinal study were examined using a 6 mHz (children) or 3.5 mHz (adults) sector probe. A sixth patient had an ultrasound examination as part of a series of investigations for urinary tract infection. In addition to crossed ectopia of the right kidney she was found to have abnormal mesen- teric vessel orientation. An upper gastrointestinal barium examination confirmed malrotation. In retro- spect her symptoms of recurrent bilious vomiting were thought to be typical of intermittent intestinal obstruc- tion and a Ladds procedure was subsequently per- formed. Axial images were obtained. The relevant clinical details and ultrasound findings are summarised in Table 1. Three patients were examined post- operatively but the surgery performed involved dividing the peritoneal bands and widening the mesenteric bases and therefore did not change the orientation of the mesenteric vessels. The vessels were studied immediately distal to the confluence of the superior mesenteric vein and splenic vein and were traced caudally, if possible. Normally the superior mesenteric vein lies ventrally and to the right of the superior mesen- teric artery (Fig. 1). In five of the cases, the superior mesenteric artery was found to lie immediately anterior to the superior mesenteric vein (Fig. 2) and when the vessels were traced caudally in three cases the superior mesenteric vein was found to swing to the left of the superior mesenteric artery. In one patient (Case 5) the superior mesenteric vein lay persistently to the left of the superior mesenteric artery and again when traced caudally, the superior mesenteric vein was found to

move further to the left (Fig. 3). We have only encoun- tered this anomalous orientation of the mesenteric vessels in those patients demonstrated to have midgut malrotation.

DISCUSSION

The term 'midgut malrotation' refers to a spectrum of conditions resulting from incomplete rotation of the midgut in the fetus. The mechanics of intestinal rotation around the superior mesenteric artery have been well discussed elsewhere. (Houston and Wittenborg, 1965; Snyder and Chaffin, 1954; Wang and Welch, 1963) and will be briefly summarised here. If the fetus is viewed from the front then the superior mesenteric artery forms the axis of rotation. The duodenum and jejunum are initially placed superior to the superior mesenteric artery and rotate in an anti-clockwise direction through 270 ° to pass under and eventually to the left of this vessel. Similarly the terminal ileum and caecum start inferiorly and rotate in an anti-clockwise direction through 270 ° passing over the superior mesenteric artery to lie on the right side of this vessel. Although we could find no reference to the involvement of the superior mesenteric vein in this rotation, from our own observa- tions and those of Nichols and Li (1983), it would appear that when rotation is incomplete the superior mesenteric vein comes to lie in an abnormal position in relation to the superior mesenteric artery. Abnormal rotation of the midgut results in a group of disorders, the exact anatomy of which depends upon the time of arrest of the rotation. The disorders include:

1. Total failure of the midgut to return to the abdomen (exomphalos). Abnormal rotation is also found in most cases of diaphragmatic hernia and gastroschisis.

2. Complete non-rotation where the duodenum des- cends straight down to the right side of the superior mesenteric artery. The small bowel lies entirely on the right side of the abdomen and the colon on the left (usually asymptomatic).

3. Incomplete rotation (commonly referred to as malrotation) in which there is some rotation of the bowel but the duodeno-jejunal flexure does not achieve its correct position and the caecum may or may not be correctly sited.

4. Reverse rotation (rare). 5. Paraduodenal hernia (rare).

The majority of patients (63% to 80%) present in the neonatal period with obstruction of the small bowel. Peritoneal or Ladds' bands crossing and usually com- pressing the duodenum are always present and small bowel volvulus is found in 50 to 80% of cases (Snyder and Chaffin, 1954; Kiesewetter and Smith, 1958; Ber- don et al., 1970; Simpson et al., 1972; Stewart et al., 1976). There may be other abnormalities associated

52

Table 1 - Case details

CLINICAL RADIOLOGY

Case Presentation Abnormality

1 Neonatal small bowel obstruction. Post-operative ultrasound examination Incomplete rotation 2 Neonatal small bowel obstruction. Post-operative ultrasound examination Incomplete rotation 3 Small bowel obstruction, agcd 18 months. Post-operative ultrasound examination Incomplete rotation 4 Aged 45. Intermittent abdominal pain Non-rotation 5 Aged 39. Incidental finding Non-rotation 6 Aged 11. Presented with urinary tract infcction. Abnormal mesenteric vessel Incomplete rotation

orientation was discovered during an ultrasound scan for investigation of crossed renal ectopia

1976). There may be other abnormalities associated with malrotation. Hirschsprungs disease and intus- susception occur more commonly than expected by chance (Brereton et al. , 1986; Filston and Kirks, 1981). Most radiologists now prefer the upper gastrointestinal barium study as the initial diagnostic procedure and in the majority of cases this will provide a correct diag- nosis. The typical findings are: a duodeno-jejunal flex- ure in an abnormal position (usually to the right of the mid-line but occasionally just to the left); obstruction of

the second or third part of the duodenum by the Ladds' bands; a small bowel volvulus if present; the small bowel lying entirely on the right side of the abdomen; and an abnormally positioned caecum.

If a barium enema is performed then the caecum and proximal colon are either entirely in the left flank or cross to the right and then angle back to point to the left hypochondrium.

Occasionally, however, the presentation is atypical or studies with contrast agents are misleading. Fewer than 20% of children with malrotation present with their initial symptoms after their first birthday (Stewart el al.,

(a)

R L

IVC

(b) Fig. 1 -Transverse image through the pancreas showing normal orien- tation of the superior mesentefic artery and vein. [], Pancreas; CBC, common bile duct; SMV, superior mesenteric vein; SMA, superior mesenteric artery; Ao, aorta.

(a)

L

IVC Ao

(b) Fig. 2 - Case 1; transverse image showing superior mesenteric vein immediately anterior to the artery. Symbols as Fig. 1 ; LRV, left renal vein.

M I D G U T M A L R O T A T 1 O N D I A G N O S E D BY U L T R A S O U N D 53

(a)

R L

IVC

(b)

Fig. 3 - Case 4; transverse image showing superior nrcsenteric vein lying to the left of the artery. Symbols as Fig 1.

1976; Berdon et al., 1970; Snyder and Chaffin, 1954; Kiesewetter and Smith, 1958) and the occurrence of malrotation in adolescents and adults is well docu- mented (Wang and Welch, 1963; Devlin et al. , 1968). At this age, not only may the diagnosis be unsuspected, but the symptoms can be different. Intermittent abdominal pain and vomiting is common and a presentation like coeliac disease is well recorded (Houston and Witten- borg, 1965; Stewart et al. , 1976). A barium examination of the gut is not always possible in the ill patient and may be difficult to interpret. The patient may not be

obs t ruc t ed at the t ime of the examina t i on . If the s tudy is not e x t e n d e d pas t the first pa r t of the d u o d e n u m the a n o m a l o u s pos i t ion of the d u o d e n o - j e j u n a l f lexure can be missed , and occas iona l ly the f lexure can lie on the left s ide of the spine and still be incor rec t ly pos i t ioned . Ha l f the rad io log is t s con t ac t ed by B e r d o n et al. (1970) had e n c o u n t e r e d m a l r o t a t i o n with a ' n o r m a l ' l igament of Tre i tz and they also r e c o r d e d six cases themselves . H o u s t o n r e p o r t e d that ou t of the 65 cases examined with oral ba r i um, 15 had a n o r m a l l y s i ted d u o d e n o - j e j u n a l f lexure and five had a ' n o r m a l ' s tudy. The ba r ium e n e m a is cons ide red to be less useful than the b a r i u m mea l because 5% of midgu t ma l ro t a t i ons have a no rma l ly si ted co lon (K ie sewe t t e r and Smith , 1958), a high mob i l e caecum in the r ight h y p o c h r o n d r i u m may not be a s soc ia t ed with midgu t m a l r o t a t i o n and i leal ref lux of b a r i u m f requen t ly m a k e s iden t i f ica t ion of the caecum difficult ( B e r d o n et al., 1970; S impson et al., 1972).

W e have d e m o n s t r a t e d that i n c o m p l e t e ro ta t ion and n o n - r o t a t i o n of the midgu t m a y be d i agnosed by ul tra- sound and is, t he re fo re , r e c o m m e n d e d when ba r ium studies are difficult to i n t e rp re t or as" the initial inves t iga t ion .

Acknowledgments. The authors wish to thank Dr Salari at Sydenham Children's Hospital for bringing Case No. l to their attention.

REFERENCES

Berdon, WE, Baker, DH, Bull, S & Santull, TV (1970). Midgut malrotation and volvulus. Which films are the most helpful? Radio- logy, 96, 375-383.

Brereton, RJ, Taylor, B & Hall, CM (1986). Intussusception and intestinal malrotation in infants: Waugh's syndrome. British Jour- nal of Surgery 73, 55-57.

Devlin, HB, Williams, RSM & Pierce, JW (1968). Presentation of midgut malrotation in adults. British Medical Journal, i, 803-807.

Filston, HC & Kirks, DR (1981). Malrotation - the ubiquitous ano- maly. Journal of Paediatric Surgery, 16, No. 4 Suppl. 1,614-620.

Houston, CS & Wittenborg, MH (1965). Roentgen evaluation of anomalies of rotation and fixation of the bowel in children. Radio- logy, 84, 1-17.

Kiesewener, WB & Smith, JW (1958). Malrotation of the midgut in infancy and childhood. Archives of Surgery, 77, 483-491.

Nichols, DM & Li, DK (1983). Superior mesenteric vein rotation: A CT sign of midgut malrotation. American Journal of Roentgenol- ogy, 141,707-708.

Simpson, AJ, Leonidas, JC, Krasha, IH, Becket, JM & Schneider, KM (1972). Roentgen diagnosis of midgut malrotation: value of upper gastrointestinal radiographic study. Journal of Paediatric Surgery, 7, 243-252.

Snyder, WH & Chaffin, L (1954). Embryology and pathology of the intestinal tract: presentation of 40 cases of malrotation. Annals" of Surgery, 140, 368-379.

Stewart, DR, Colodny, AL & Daggen, WC (1976). Malrotation of the bowel in infants and children: a 15 year review. Surgery, 79, 716- 720.

Wang, C & Welch, CE (1963). Anomalies of intestinal rotation in adolescents and adults. Surgery, 54, 839-855.