Volvulus

Etiology and imaging appearance of volvulus

The development of volvulus is closely linked to anatomical prerequisites. The main predispose factor is the presence of a persistent dorsal suspending mesentery, which creates excessive mobility of the bowel loops, creating ideal conditions for their rotation around their axis.

When performing conventional radiocontrast examinations using a water-soluble contrast agent, the classic sign of strangulation is visualized. At the exact site of the twist, the contrast forms a narrowing known as the "bird's beak" sign ('bird's beak' sign). This sign is pathognomonic and indicates acute mechanical obstruction.

In cases of an asymptomatic or intermittent course of the disease, the examination strategy changes. To confirm the presence of abnormal colonic redundancy and to reliably exclude other obstructive lesions, patients are indicated for double-contrast barium enema (DCBE) or CT colonography (CTC).

CT semiotics: key signs

Computed tomography (CT) is the leading diagnostic method for volvulus, providing a detailed spatial depiction of the affected area.

• Whirl sign ('whirl sign'): Characterizes the twisting of bowel loops and mesenteric vessels. Notably, the visual prominence of this sign is directly proportional to the degree of bowel rotation.
• X-marks-the-spot sign ('X-marks-the-spot' sign): This phenomenon is best visualized when analyzing coronal slices. At the site of the twist, two overlapping transition points are distinctly identified, forming a characteristic cross-like pattern.
• Features of caecal volvulus (caecum): In this case, the caecum is markedly dilated. Due to excessive mobility and gas accumulation, it can atypically displace into the left upper quadrant of the abdomen.

The main goal of early detection of these signs is the prevention of severe complications, which include bowel ischemia (bowel ischaemia) and wall perforation.

Differential diagnosis: intussusception and endometriosis

When analyzing CT scans with signs of bowel obstruction, other pathological processes must also be considered.

Intussusception (Intussusception) In adult patients, colonic intussusception has a fundamentally different nature than in children—it is almost always secondary and develops against the background of a tumor process. In modern practice, this pathology is much more frequently detected using CT, completely replacing the traditional barium enema.

Gastrointestinal endometriosis (Endometriosis) Gastrointestinal tract involvement occurs in 12–37% of female patients with endometriosis. Predilection sites include the sigmoid colon (sigmoid) and small bowel loops located in the pelvis; the caecum is involved significantly less often. The pathogenesis is that serous implants deeply invade the muscularis propria of the bowel wall. This causes pronounced fibrosis, local wall contraction, and a mass effect. Meanwhile, the mucosa paradoxically remains intact. Despite the mucosal integrity, the disease may clinically manifest with rectal bleeding.

On contrast-enhanced studies, endometriosis demonstrates a localized mass effect with typical retracted (contracted) mucosal folds. However, the modality of choice today is MRI. It reliably detects fibrous plaques (areas of low MR signal) that can completely obliterate the pouch of Douglas and involve the rectosigmoid region.

Acute appendicitis and incidental findings on tomograms

In addition to obstructive states, imaging methods are actively used to diagnose inflammatory processes and identify asymptomatic phenomena.

MRI appearance of acute appendicitis (especially relevant for pediatric patients):

1. On T2-weighted images (T2-WI) in the axial plane, mild mural thickening of the appendix and its characteristic stratification at the tip are visualized.
2. On diffusion-weighted images (DWI) using a high b-value (e.g., 600), the presence of restricted diffusion at the tip is confirmed. This sign reliably indicates active focal inflammation.

Pneumatosis intestinalis and mesenterica Sometimes an incidental finding is discovered during CT. On coronal slices, extensive bubbly gas localized directly within the bowel wall (bubbly mural gas) as well as mesenteric gas (mesenteric gas) can be clearly visualized. It is extremely important to remember the clinical significance of this phenomenon: such an alarming CT picture can be observed in completely asymptomatic patients undergoing examination for entirely different complaints.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• CT colonography (CTC) technique and patient preparation
• Degrees of bowel wall ischemia and their CT patterns
• MR protocols for detecting pelvic endometriotic lesions
• Principles of interpreting high b-value DWI in abdominal radiology
• Differential diagnosis of benign and life-threatening pneumatosis intestinalis

Other topics in the section "Diagnostic Radiology of the Abdominal Organs"

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