Volvulus and Midgut Malrotations

A volvulus is a complete twisting of a loop of intestine around its mesenteric attachment site. This can occur at various locations of the GI tract, including stomach, small intestine, caecum, transverse colon, and sigmoid colon. Midgut malrotation refers to twisting of the entire midgut about the axis of the superior mesenteric artery (SMA).¹
A knowledge of embryology is necessary to understand the mechanisms that lead to the development of volvulus and malrotation.² At the fourth week of gestation, the gastrointestinal system is a straight tube centrally located in the abdomen. During the ensuing 8 weeks, the midgut rotates and becomes fixed to the posterior abdominal wall. Arrest of development at any stage narrows the mesenteric base and impairs fixation, leaving the bowel at high risk for volvulus.¹

Nonrotation occurs in approximately 1 in 500 live births.³ However, the true incidence of malrotation is unknown, since many asymptomatic patients fail to present. Either sex can be affected with the anomaly.⁴ In approximately 60% of patients, malrotation presents by age 1 month. Another 20-30% of patients present at age 1-12 months.⁵ Thereafter, it can present at any age, and is seen in adults and even the elderly.⁶

It should be remembered that malrotation and volvulus are two distinct entities. Nonrotation may be asymptomatic and be detected as an incidental finding during gastrointestinal imaging for some other purpose. Malrotation may cause intermittent symptoms of intestinal obstruction, but if a volvulus develops, the obstruction is typically complete. The presenting features will also vary, depending on age.⁷
Bilious vomiting is the key presenting symptom. A child presenting with green or yellow vomiting should be presumed to have volvulus until proved otherwise. Infants presenting in the first 24 hours after birth through the first week of life tend to have more severe obstruction, and present with bilious vomiting and feeding intolerance. After the age of 2 months, bilious and nonbilious vomiting occur with equal frequency. Other symptoms may include failure to thrive, anorexia, constipation, bloody stools, and intermittent apnoea.^7,8
Older children may present more insidiously with cyclical vomiting, recurrent abdominal pain, protein-calorie malnutrition and immunodeficiency.⁷ Once intestinal ischaemia develops, pain becomes the most pronounced symptom.
Abdominal examination may be normal in the early stages,⁹ or may show distension.¹⁰
Careful examination may reveal a palpable abdominal mass in some patients.⁷ If ischaemia develops, the presentation is of acute abdomen, with significant abdominal distension, and signs of peritonitis. Blood or sloughed tissue may pass per rectum. Tachycardia, hypovolaemia and septic shock herald the onset of gangrene.¹¹

In the acute phase, the differential diagnosis is of acute abdomen/obstruction. Chronic vague abdominal symptoms in older children or adults raise the possibility of a wide range of other symptoms, which should include:

• Annular pancreas
• Appendicitis
• Cholecystitis
• Colic
• Constipation
• Duodenal Atresia
• Duodenal web
• Gastroenteritis
• Gastroesophageal Reflux
• Henoch-Schöenlein purpura
• Hepatitis B
• Hirschsprung Disease
• Hypertrophic Pyloric Stenosis
• Incarcerated hernia
• Intussusception
• Meckel Diverticulum
• Necrotising enterocolitis
• Ovarian torsion
• Pancreatitis
• Peptic ulcer
• Perforated viscus
• Renal stones
• Sickle cell crisis
• Urinary tract infection

Laboratory investigations

The diagnosis is usually made clinically, and management should not be delayed in order to obtain the results of laboratory tests.⁷ A full blood count helps to assess the severity of the illness, a raised white cell count may be found in sepsis or gangrene, and a low haemoglobin may suggest venous oozing. Regular urea and electroytes monitoring may help to assess the patient's general condition, and detect dehydration, sepsis and acidosis. Large amounts of fluid can migrate into the bowel lumen and interstitial space, and in such patients dehydration can occur without diarrhroea and vomiting. Hyponatremia, hyperkalemia, metabolic acidosis, increased BUN and creatinine, hypochloremia, and lactic acidosis can occur in such cases.

Plain radiography

In simple malrotation, plain radiographs are frequently normal. Upright, supine and lateral radiographs may be helpful in diagnosing bowel obstruction, but may be more contributory in large rather than small bowel obstruction. Radiographs taken several hours apart may be helpful. Dilated small-bowel loops, marked gastric or proximal duodenal dilatation, with or without intestinal gas, and air-fluid levels may be seen. Normal or equivocal results should not delay progress to other tests if the clinical situation is deteriorating.¹²In midgut volvulus, the classic radiographic finding is a partial duodenal obstruction (dilation of both stomach and proximal duodenum, with a small amount of distal bowel gas). This is known as the 'double bubble' sign. Complete obstruction of the duodenum may also be found. Less frequently are a gasless abdomen, ileus, or distal small bowel obstruction with multiple dilated loops and air-fluid levels. These are ominous signs.⁵

Contrast studies

In malrotation, the duodeno-jejunal (DJ) junction is misplaced, either at or to the right of the midline. Various displacements of lower bowel structures may also be seen.⁵
An upper GI contrast series is the investigation par excellence if volvulus is suspected. In a child, the UGI series is performed with a small amount of barium being administered either by bottle or through a nasogastric tube.Various patterns may be observed, including dilation of the proximal duodenum with a "bird-beak" obstruction and a spiral or corkscrew duodenal configuration.¹³ Selected patients may need studies of the lower bowel, using a barium enema.

Other imaging studies

Ultrasound may reveal a midline abdominal mass in suspected volvulus. Ultrasound and CT scanning can help to confirm malrotation by identifying the position of the mesenteric vessels.¹⁴ The "whirlpool sign" on colour Doppler may show a whirlpool pattern of flow within the superior mesenteric vein, indicating malrotation with volvulus.¹⁵ The low specificity of these tests suggests that whilst they may be useful screening tools, they are inferior to the UGI contrast series in the acute situation.

Non-surgical

This may be appropriate for older patients with intestinal malrotation who are asymptomatic, but they should be warned that volvulus can occur at any time. Observation and gastro-intestinal decompression with a nasogastric or orogastric tube should be commenced and a close watch kept for the development of symptoms or signs suggestive of intestinal obstruction.⁷

Surgery

The Ladd procedure is the treatment of choice in most cases. Volvulus is corrected by rotating the small intestine in a counterclockwise direction, the caecum is placed in the left abdomen, and the duodenum is directed down the right paravertebral gutter. A second-look laparotomy may be used 36 hours later to ensure viability of the remaining bowel.
A laparoscopic variation of the Ladd procedure has been used in some centers, with the general advantage of decreased adhesions and scarring, but good visualisation of the entire bowel is necessary.¹⁶

Complete and persisting midgut volvulus leads to intestinal ischaemia, mucosal necrosis, and sepsis. Untreated, perforation, peritonitis and death soon follow.⁷
Chronic intermittent volvulus may cause malabsorption with constipation interspersed with diarrhoea.¹⁷
Post-operatively, the main complication is short-gut syndrome with the consequent problems surrounding parenteral nutrition, i.e. line sepsis, hepatobiliary dysfunction and growth retardation.¹⁸

Midgut volvulus carries a mortality rate of 3-15%.¹ Survival rate is dependent to some extent on the amount of ischaemic bowel which has to be excised,¹⁹ and on the length of delay before the condition is diagnosed and treated.

Because volvulus is such a devastating complication in children, evidence supports operative treatment of asymptomatic malrotation, using the Ladd procedure. This is particularly appropriate for young children with no existing co-morbidity, as they recover quickly. There is no similar evidence base to support this approach in adults.²⁰