Midgut Volvulus Imaging

Introduction

Midgut volvulus is an intestinal condition in which malrotation causes them to twist over themselves. Intestinal malrotation occurs when there is an interruption in the embryologic bowel development and mesenteric malfixation. Midgut volvulus can occur at any age but is more common in children and infants. Bilious emesis (extrinsic compression of the duodenum due to obstruction) is the initial feature of the midgut volvulus. Midgut volvulus often involves both chocoholic and duodenojejunal loops and in some cases, it affects the duodenojejunal loops only.

What Are the Symptoms of Midgut Volvulus?

The symptoms of malrotation and volvulus include:

• Vomiting bile (greenish) fluid.

• Stomach pain.

• Diarrhea.

• Swollen belly.

• Constipation.

• Rectal bleeding.

• Bloody stools.

What Is the Pathophysiology of Midgut Volvulus?

• In the fetus, the intestine develops in three portions which include the foregut, midgut, and hindgut. The fetal midgut portion shows the rapid growth that the abdominal cavity cannot house the whole intestine. Hence, a part of the intestine herniates into the umbilical cord. By the eighth to twelfth week of gestation, the intestine herniates back into the abdominal cavity with a 270-degree counter-clock rotation to position the duodenojejunal junction (DJJ) in the left upper quadrant and cecum in the right lower quadrant.

• Once reaching the final anatomic position, mesenteric attachments provide stability to the bowel loops. If there is a genetic mutation that affects the signaling for normal intestinal rotation, the bowel loops residing in the abnormal position in the abdomen also fail to stabilize in the abdomen. For example, a mutation in the BCL6 gene results in the absence of left-sided expression of the transcript, causing malrotation. In an incomplete rotation, the fibrotic band arises between the duodenum (first part of the small intestine) and the retroperitoneum, and the cecum remains in the epigastric region. The fibrotic bands are also called Ladd’s bands which cross the second part of the duodenum and connect the cecum to the lateral abdominal wall. The Ladd’s band acts as a point of obstruction.

• The mesenteric takeoff leads to constriction of all the branches of the superior mesenteric artery supplying the midgut. The volvulus can occur around the base of the mesentery, obstructing the proximal jejunum and resulting in midgut ischemia.

What Are The Imaging Techniques Used in the Diagnosis of Midgut Volvulus?

Computed Tomography (CT) Scan:

• Though a CT scan is not used as a common imaging tool in the diagnosis of midgut volvulus, it can be used to detect abnormal bowel rotation.

Some of the suspective findings of malrotation in CT scans are as follows:

• Duodenum does not reach the midline.

• Abnormal relationship between SMV and SMA.

• The third part of the duodenum is found to be anterior to the SMA.

• Ectopic ileocecal junction.

• Jejunal bowel loops are found in the right abdomen, and ileal bowel loops are found in the left abdomen.

Ultrasonography:

• Ultrasonography shows both direct and indirect signs of midgut volvulus.

• In ultrasound, if the superior mesenteric vein (SMV) is found posterior or left to the superior mesenteric artery (SMA), it is indicative of malrotation.

• In about 30 percent of patients, SMV lies slightly ventral and right to SMA along with malrotation.

• On color doppler ultrasonography, the midgut volvulus shows a whirlpool sign in which blood flow within the superior mesenteric vein wraps around the superior mesenteric artery in a clockwise direction.

• Fluid-filled, dilated duodenum is often seen in patients having obstruction without volvulus.

• Ultrasound helps detect the third part of the duodenum, which is positioned between the aorta and SMA.

• Ultrasound findings are a more reliable marker of rotation than detecting the duodenojejunal junction (DJJ) because of the movement of the DJJ in children and infants.

• Bedside ultrasound can be used to detect volvulus in newborns.

Upper Gastrointestinal (GI) Series:

• The upper GI series is also known as the barium swallow study or barium meal. It is a special test using barium to detect diseases affecting the upper gastrointestinal tract (GI). The upper GI tract includes the throat, esophagus, stomach, and the first part of the small intestine.

• Barium is a white-colored substance mixed with water to make it like a thick milkshake to drink during the procedure. When it passes through the body, barium coats the food pipe and stomach, which makes the organ visible on an X-ray, it will appear as black or white during imaging on the screen.

• The upper GI series shows 96 percent sensitivity in detecting malrotation in infants and children.

• The upper GI series is an excellent diagnostic tool for detecting midgut volvulus with malrotation.

• The classic radiographic findings of midgut volvulus in the upper GI series are dilatation of the stomach and proximal duodenum, the presence of a small amount of distal bowel gas, and partial duodenal obstruction.

• Complete duodenal obstruction may be found.

• Some less common signs are the gasless abdomen, ileus obstruction, distal small bowel obstruction, air-fluid levels, and multiple dilated loops.

• Findings of malrotation in the upper GI series include the following:

• Downward and right side displacement of DJJ is shown on the frontal view.

• The lateral view shows an abnormal duodenal course.

• An abnormal jejunum position on the right side of the abdomen is indicative of malrotation.

• Findings of malrotation with midgut volvulus in upper GI series include the following:

• Fluid-filled and dilated duodenum.

• Proximal small bowel obstruction.

• Corkscrew Pattern - In midgut volvulus, the proximal jejunum and distal duodenum show a spiral appearance.

• Thick folds and mural edema.

• The proximal jejunum and distal duodenum do not cross the midline; instead, they are found in the downward direction.

What Are the Treatment Options for Midgut Volvulus?

• When the volvulus is suspected, immediate intervention is needed to prevent the ischemic process. Ladd's procedure is usually performed, which does not help with malrotation but opens the narrow mesenteric pedicle, preventing the recurrence.

• Ladd's procedure involves lysis of the band formed between the lateral abdominal wall and cecum and also between the terminal ileum and duodenum, which relaxes the superior mesenteric artery.

• This procedure relaxes the duodenum into the right lower quadrant and cecum into the left lower quadrant and does not require sutures to secure.

What Are the Differential Diagnoses of Midgut Volvulus?

• Bowel (intestine) obstruction in newborns.

• Neonatal sepsis (infection involving the bloodstream of neonates).

• Necrotizing enterocolitis (a serious condition that causes the death of the intestinal tissues commonly affects premature infants).

• Pediatric duodenal atresia (congenital closure of the duodenum).

• Pediatric gastroesophageal reflux (backward flow of the stomach content through the food pipe into the mouth in babies under two years old).

• Intestinal volvulus (intestinal obstruction due to twisting of the intestine).

Conclusion

The upper GI series shows 85 to 95 percent sensitivity and high specificity in diagnosing midgut volvulus. Normal abdominal radiographs cannot detect malrotation. Intestinal volvulus and malrotation are more common in males than females. A plain abdominal radiograph shows a paucity of gas in the intestine with few air-fluid levels. When these findings are evaluated, the patient should immediately undergo fluid resuscitation followed by proper surgery. With the delayed diagnosis and management, mesenteric ischemia develops into small bowel gangrene. Hence early diagnosis and surgical treatment can prevent the need for small bowel resection (surgical removal).