Pathophysiology: Ladd's bands
In malrotation, the process of intestinal fixation within the abdominal cavity is disrupted. Attempting to anchor itself, the intestine forms abnormal peritoneal adhesions known as Ladd's bands (Ladd’s bands). These structures extend from the cecum (which is often abnormally located high on the right) to the retroperitoneum in the right lower quadrant.
The problem is that Ladd's bands cross the duodenum and can compress it, causing mechanical obstruction. It is precisely these bands that must be divided during surgical correction.
Ultrasound diagnostics
Ultrasonography (ultrasound) is the initial imaging modality for critically ill neonates.
- Indirect signs of obstruction: ultrasound can reveal a distended, fluid-filled stomach and proximal duodenum.
- Abnormal vascular positioning: in approximately 66% of patients with malrotation, the superior mesenteric vein (SMV) lies to the left of or ventral to the superior mesenteric artery (SMA). However, this sign lacks high specificity and sensitivity.
- The whirlpool sign: this is a key diagnostic marker of volvulus. Color Doppler imaging demonstrates the SMV spiraling (clockwise) around the SMA. If a neonate exhibits this sign, no further studies are required prior to emergency surgery.
In addition, the sonographer attempts to visualize the third part of the duodenum in its normal position (between the aorta and the SMA), but this is often hampered by bowel gas.
Contrast radiography
An upper gastrointestinal contrast study is recognized as the "gold standard" in the diagnosis of malrotation and volvulus.
The primary radiographic marker of volvulus is the corkscrew pattern. Images show the duodenum and loops of the jejunum twisting in a spiral around the axis of the mesenteric vessels. Alterations in bowel caliber at the level of the duodenojejunal flexure (DJF) are also frequently observed.
Normally, the DJF should be located to the left of the midline at the level of the pylorus. In developmental anomalies, the DJF may be located below this level, resulting in a horizontal orientation of the stomach (although this position can occasionally be a normal variant in neonates).
Surgical treatment (Ladd's procedure)
The standard treatment method is Ladd's procedure (Ladd’s procedure). Stages of the operation:
- Evisceration of the intestines (delivery into the surgical wound), detorsion (untwisting), and thorough inspection.
- Division of pathological Ladd's bands.
- Surgical widening of the base of the mesentery to prevent recurrent volvulus.
- Non-anatomical placement of the bowel back into the abdominal cavity: the duodenum and jejunum are placed on the right, and the colon on the left.
- Performance of a prophylactic appendectomy.
It is important to remember that the operation does not restore normal anatomy (the DJF permanently remains in an atypical position). If the mesentery was not sufficiently widened, volvulus can recur. Therefore, a history of Ladd's procedure does not rule out volvulus as a cause of abdominal pain in the future.
Duodenal atresia and stenosis
The duodenum begins to form during the 4th week of embryogenesis. By weeks 5–6, active mucosal proliferation temporarily occludes the intestinal lumen. Normally, recanalization (restoration of the lumen) follows. Disruption of this process leads to the formation of atresia (complete obliteration) or stenosis (narrowing).
Clinically, atresia most frequently (in 80% of cases) manifests as bilious vomiting, as the obstruction is located distal to the ampulla of Vater.
These malformations are often associated with other anomalies:
- Down syndrome (approx. 30% of cases).
- Congenital heart defects (approx. 20%).
- Malrotation (20–30%).
Briefly: answers to topical questions
What clinical symptoms are characteristic of acute midgut volvulus in a neonate?
In symptomatic neonates, acute volvulus presents in the first few days of life with bilious vomiting.
The clinical presentation depends on the patient's age:
- Neonates — the presence of bile in vomitus is a key factor in determining further management and is considered a red flag symptom.
- Older children — non-specific manifestations, including recurrent abdominal pain combined with bilious vomiting, diarrhea, and failure to thrive.
What late postoperative complications can occur in patients who have undergone Ladd's procedure?
Following Ladd’s procedure, patients may experience recurrent volvulus. This complication develops if the base of the mesentery was not adequately widened during surgery. Furthermore, the operation does not restore normal anatomy; therefore, the duodenojejunal flexure always remains in an abnormal position. A history of this surgery does not rule out volvulus as a cause of abdominal pain in the future.
What is the normal anatomical relationship between the superior mesenteric vein and artery on ultrasound?
The sources do not explicitly state the normal relationship between the superior mesenteric vein and artery. It is noted that in malrotation, the vein lies ventrally or to the left of the artery; this sign is detected in approximately two-thirds of patients and is neither sensitive nor specific for malrotation.
Class and exam questions
Which ultrasound sign definitively indicates intestinal volvulus in a neonate?
The whirlpool sign on color Doppler mapping, where the vein wraps around the artery.
Why is the appendix always removed during Ladd's procedure?
This is a preventive measure, because after surgery the colon and cecum are placed atypically (on the left), which would complicate the diagnosis of appendicitis in the future.
Does Ladd's procedure restore normal intestinal anatomy?
No, the duodenojejunal flexure remains in an abnormal position, and the intestine is placed atypically (small intestine on the right, large intestine on the left).
What causes bilious vomiting in duodenal atresia?
In 80% of cases, the level of obstruction in atresia is distal to the ampulla of Vater (the site where the bile ducts empty), allowing bile to enter the stomach and vomitus.
What else to study on this topic
- Other causes of duodenal obstruction (webs, annular pancreas)
- Gastrointestinal embryogenesis and rotation stages
- Incidental findings of malrotation in adults: management strategy
- Differential diagnosis of bilious vomiting in neonates
- Preduodenal portal vein as a cause of obstruction
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