Elsevier

Current Problems in Diagnostic Radiology

Volume 49, Issue 6, November–December 2020, Pages 476-488
Current Problems in Diagnostic Radiology

Fluoroscopic Diagnosis of Malrotation: Technique, Challenges, and Trouble Shooting

https://doi.org/10.1067/j.cpradiol.2019.10.002Get rights and content

Abstract

A fluoroscopic upper gastrointestinal series is the most commonly used investigation for the diagnosis of malrotation and midgut volvulus. However, both false positive and false negative results can occur causing diagnostic confusion. Several physiologic states and pathologic conditions can mimic fluoroscopic appearance of malrotation. Proper fluoroscopic technique is essential to maximize diagnostic accuracy. In this pictorial essay, we discuss common diagnostic challenges in the diagnosis of malrotation and strategies radiologists can use to clarify the diagnosis in equivocal cases.

Introduction

Malrotation of the gastrointestinal (GI) tract is a congenital abnormality that predisposes patients to midgut volvulus, a potentially fatal condition.1 An upper GI fluoroscopic examination is commonly requested either on an urgent basis in children having bilious vomiting or in an outpatient setting in children with various abdominal symptoms. Several physiologic states can cause diagnostic confusion on upper GI series.2 It is important that the radiologists familiarize themselves with the optimal method of performing and interpreting a pediatric upper GI series to maximize diagnostic accuracy. In this review article, we discuss commonly encountered challenges in the diagnosis of malrotation and offer suggestions for troubleshooting.

Malrotation is a spectrum of disorders leading to abnormal position of the bowel in the abdomen due to abnormal embryologic bowel rotation.3

The gut in early embryonic period is a straight tube-like structure. As the gut lengthens during subsequent weeks, it also rotates 270° counterclockwise around the superior mesenteric artery (SMA) axis in several stages (Fig 1). Due to this rotation the cranial portion of the gut which forms the duodenum migrates to a location posterior to the SMA with the duodenojejunal junction (DJJ) to the left of SMA. The caudal portion of the gut which contains the cecum rotates counterclockwise from the left side of the abdomen in such a way that the cecum comes to rest in the right lower quadrant (RLQ).4

At completion of rotation, the ascending colon is fixed to the retroperitoneum on the right and the descending colon is fixed to the retroperitoneum on the left (Fig 2). Majority of the duodenum is also retroperitoneal.5 The small bowel mesentery has a wide root extending between 2 fixed points, the first being the DJJ in the left upper quadrant and the second being the ileocecal valve in the RLQ.6 The DJJ is suspended by the ligament of Trietz which is a peritoneal fold extending from the right esophageal crus of diaphragm and connective tissue around the coeliac artery and SMA.7 The ligament of Trietz is a surgically identifiable landmark and denotes the point where the small bowel becomes an intraperitoneal structure.

Malrotation may affect small bowel or large bowel, or both.8 Any deviation from the normal pattern of intestinal rotation leads to an abnormal position of the DJJ and/or cecum. With decreased distance between the 2, the mesentery has a narrower root thus increasing the risk of twisting or volvulus.9 Abnormal rotation of the gut is also associated with peritoneal bands extending from the cecum to other structures which can cross the duodenum and cause obstruction.10

Malrotation affects about 1 in 500 live births. Vast majority of affected children present in the neonatal period, most commonly with bilious vomiting. Older children may present with nonspecific symptoms like intermittent vomiting, abdominal pain, and poor weight gain. Sometimes malrotation is an incidental finding on imaging done for other purposes.11 Malrotation is associated with several syndromes and disorders including but not limited to gastroschisis, congenital diaphragmatic hernia, omphalocele, and heterotaxy syndromes.10

On a normal upper GI series, the proximal duodenum extends posteriorly from the pylorus, as seen on the lateral view, and extends toward the spine to its retroperitoneal location. The duodenum then crosses over to the left side of the spine and turns cranially to extend to the DJJ. The DJJ is identified on fluoroscopy as the cranial most and leftward most part of the bowel where it takes a definite inferior turn. A normally located DJJ should be to the left of the left-sided pedicle of the adjacent vertebral body (Fig 3). The DJJ should be at the level of the duodenal bulb or higher on the frontal view and located posteriorly on the lateral projection.10,12,13 The proximal jejunal loops are usually located in the left upper quadrant and cecum in the RLQ.

If the esophagus is to be evaluated, a left side down position should be used for the lateral view to avoid unintended gastric emptying. Esophageal evaluation in the right side down position may cause early emptying of contrast into the duodenum causing the first pass of contrast through the duodenum to be missed. Volume of contrast used should be kept to minimum necessary as excessive contrast in the stomach can obscure the DJJ. Patients referred from the inpatient or emergency services may already have a nasogastric (NG) tube placed. Delivery of contrast through the NG tube can allow more control over contrast volume. It should however be kept in mind that in younger children postpyloric enteric tubes can distort anatomy and displace the DJJ.14

Once desired amount of contrast has reached the stomach the child should be positioned in right side down position to assess extension of duodenum to the retroperitoneum. The radiologist should be vigilant and ready to image quickly as in some patients there is prompt gastric emptying in this position. After the proximal duodenum is opacified the child should be placed in supine position to assess position of the DJJ in the frontal view. Continuous fluoroscopy while the child is moved from the lateral to supine position is beneficial to capture the first pass of contrast through the duodenum. If there is a delay in movement of contrast through the third portion of the duodenum to the left, a transient left posterior oblique positioning of the patient may aid forward movement of contrast. The child then can be quickly returned to the supine position to document the anatomy. Once the location of the DJJ on the frontal view is documented, a lateral view should also be obtained to demonstrate its posterior retroperitoneal location.

If the DJJ is obscured by contrast in the stomach gentle palpation to displace the stomach may aid in visualization of the DJJ (Fig 4). The first pass of contrast through the duodenum may sometimes be missed if the stomach empties too quickly. Opacification of proximal jejunal loops may then hinder identification of the DJJ. If this happens intermittent fluoroscopy over next several minutes may be beneficial. After the contrast disperses within the jejunum the child may again be positioned in the right side down position and a second bolus of contrast may be allowed to enter the duodenum. A densely opacified DJJ can be identified through overlapping loops of jejunum (Fig 5). If the position of the DJJ remains equivocal the study should be extended to determine the position of proximal jejunal loops and the cecum.

Section snippets

Malrotation

An upper GI series is the preferred imaging study to diagnosis malrotation with sensitivity of 93%-100%.15, 16, 17 Demonstration of an abnormal position of the DJJ is the most important fluoroscopic finding to clinch the diagnosis. Findings that suggest malrotation are–(1) the DJJ projects medial to the left-sided pedicle; (2) DJJ is inferior to the duodenal bulb; (3) DJJ is located more anterior than usual suggesting an intraperitoneal location (Fig 6).10,12,13 While most patients with

Conclusions

An upper GI series is the most commonly performed radiological test for the diagnosis of malrotation and midgut volvulus. Unfortunately, several physiologic and pathologic conditions can have a fluoroscopic appearance similar to subtle cases of malrotation causing diagnostic dilemma. Proper technique in performing the upper GI study is vital to maximize diagnostic yield. The radiologist should be familiar with physiologic variations in duodenal anatomy. Several strategies such as gastric

Conflict of Interest

The authors declare that they have no conflict of interest.

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