Descending colon volvulus in a patient with persistent left mesocolon: A case report

Abstract

Persistent descending mesocolon is a congenital anomaly in which the mesentery of the descending colon fails to fuse with the retroperitoneum, resulting in a mobile colon that is suspended by a mesentery extending from the left upper quadrant to the pelvic brim. This can predispose to intestinal obstruction by twisting of the colon, internal hernia with or without a mesenteric defect or intussusception.

We present a case report of a 30-year-old male who presented with recurrent abdominal pain and distension, with a CT diagnosis of descending colonic volvulus due to persistent left mesocolon. The patient underwent a successful resection of the affected colon and had an uneventful recovery. This case highlights the importance of considering anatomical variants in the diagnosis and management of colonic volvulus.

Introduction

Colonic volvulus is a rare condition that accounts for approximately 5% of all large bowel obstructions. It occurs when a loop of the colon twists on its mesentery, leading to obstruction, ischemia, and potential perforation. The sigmoid colon is the most common site of volvulus, followed by the cecum and the transverse colon. Anatomical anomalies, such as malrotation, redundant colon, and elongated mesentery, may predispose to volvulus formation [1,2]. We present a case of descending colon volvulus in a patient with persistent left mesocolon (Figs. 1, 2, and 3).

Fig. 1.

CT topogram: significantly distended colonic loop occupying the left upper abdomen.

Fig. 2.

Contrast-enhanced CT scan: A-B axial images; C-D-E reconstructed images in coronal plane: CT scans revealed the presence of a redundant descending colon, characterized by an excessive loop displaced in the left supramesocolic space. This segment was overdistended, measuring up to 11 cm in diameter. Coronal reconstruction provided a detailed view, highlighting the swirling appearance of the afferent vascular structures. The ascending colon appeared within normal size parameters, whereas the distal descending colon and sigmoid colon exhibited collapsed walls.

Fig. 3.

Surgical specimen: dilated segment of the descending colon extending approximately 25 cm, characterized by thinned walls and a lumen diameter of up to 10 cm.

Case report

We present a case involving a 30-year-old man with a medical history marked by recurrent abdominal bloating and distension, discomfort and irregular bowel habits characterized by periods of constipation alternating with periods of diarrhea for about 3 years. This clinical condition, initially mistaken for irritable bowel syndrome, was treated with a dedicated diet, without improvement in symptoms.

Coincidentally, a chest X-ray conducted for unrelated reasons revealed the overdistension of a colonic segment in the left upper abdomen, accompanied by the elevation of the ipsilateral hemidiaphragm.

Subsequently, the patient underwent an elective abdominal CT scan with contrast, revealing the presence of a redundant descending colon, partially displaced in the left upper abdominal quadrant. A segment of the descending colon in the left supramesocolic space appeared overdistended, measuring up to 11 cm in diameter, with swirling appearance of the afferent vascular structures, without signs of strangulation or perforation. The right colon appeared normal in size, while the distal descending colon and sigmoid colon showed collapsed walls. These findings collectively suggested a diagnosis of volvulus of the descending colon, likely attributable to the presence of a persistent and redundant descending mesocolon.

Following this, the patient underwent exploratory laparotomy, unveiling a significant dolichocolon with marked distension of the entire descending colon, extending proximally to the splenic flexure and involving a portion of the transverse colon. Additionally, observations revealed the laxity of the mesocolon and the absence of physiological fixation of the viscera.

To address the recurrent episodes of sub-occlusion induced by the torsion of the descending colon on the persistent mesocolon, the patient underwent a left colectomy. Resection was performed at the level of the sigmoid colon and transverse colon, followed by a subsequent manual colo-colic anastomosis utilizing a continuous suture technique.

The macroscopic examination of the surgical specimen revealed the presence of a dilated colonic segment extending for approximately 25 cm, characterized by thinned walls, with a lumen diameter of up to approximately 10 cm. The histological examination highlighted signs of non-specific inflammation in the mucosa and hypertrophy of ganglion cells in the intramural nerve plexuses.

Discussion

Colon volvulus stands as the third most prevalent cause of colonic obstruction, following carcinoma and diverticulitis. This condition arises from the twisting of the intestine on its mesenteric axis, resulting in either partial or complete blockage. Although it can spontaneously resolve and become a chronic issue, colon volvulus more commonly presents acutely [2].

Volvulus typically impacts colon segments with a mesentery, including the sigmoid, cecum, and transverse colon. In rare instances, volvulus may occur at the splenic flexure due to congenital absence or surgical division of normal fixation structures like the gastrocolic, phrenicocolic, and splenocolic ligaments [3,4]. The ascending and the descending colon, usually surrounded by peritoneum on three sides, are retroperitoneal structure without a mesocolon. However, during fetal development in the fourth or fifth month of gestation, the primitive dorsal mesocolon might fail to fuse with the parietal peritoneum, resulting in a persistent descending mesocolon [5]. This condition allows mobility of the ascending or descending colon, leading to variations in position and the potential for complications. The persistence of the descending mesocolon is far less common than that of the ascending mesocolon. This anomaly permits mobility of the descending colon, which can lead to considerable changes in its position and often result in torsion and volvulus.

The persistent descending mesocolon is categorized into three types based on the degree of displacement of the descending colon and the extent of adhesion. Type A represents a complete lack of fixation for both the ascending and descending colon, along with the absence of the transverse colon. Type B involves moderate displacement of the descending colon toward the midline or slightly to the left. Type C corresponds to marked displacement of the descending colon with paracecal fixation [5]. The persistent descending mesocolon is also categorized as long-S and short-S types, depending on the length of the sigmoid colon and its adhesion to the descending colon. In the long-S type, there is excessive adhesion between the lengthy sigmoid colon and the descending colon, while in the short-S type, the descending colon runs straight without adhering to the sigmoid colon [1].

From a clinical perspective, a patient's periodic abdominal discomfort and distention, combined with recurrent constipation, may indicate episodes of recurrent volvulus with spontaneous derotation. The diagnosis of colonic volvulus can typically be suspected using conventional abdominal radiography and confirmed with a barium enema. A distinctive CT sign indicative of volvulus is the whirl sign [6], which proves particularly valuable in diagnosing sigmoid [7] and cecal volvulus [8]. The whirl is comprised of tightly twisted bowel, mesentery, and vessels. The tightness of the whirl correlates with the degree of rotation, and when blood supply to the bowel is compromised, necrosis and perforation can occur. CT findings indicative of strangulation encompass circumferential thickening of the bowel wall, intestinal pneumatosis, mesenteric congestive haziness, and mesenteric hemorrhagic fluid [9]. In instances of perforation, abdominal X-rays and CT scans exhibit the presence of free air in the abdomen, primarily beneath the diaphragm. CT proves to be significantly more specific than a barium study in ascertaining the presence, cause, level, and degree of bowel obstruction, as well as signs of strangulation and any associated abnormalities outside the bowel wall.

In our patient, the conspicuously distended bowel loop on radiography suggested the possibility of volvulus, but the exact level of obstruction was hard to identify with confidence. The whirl sign identified in the CT scan within the left colonic compartment served as a diagnostic marker for volvulus, and the level of obstruction was determined by recognizing the afferent and efferent loops as originating from the descending colon.

The main differential diagnosis is splenic flexure volvulus, which is caused by lack of fixation structures and a resultant highly mobile colon. However, in our patient the normal position of the splenic flexure and the arrangement of afferent and efferent loops at the level of the descending colon are highly discriminatory features.

Surgical exploration may be necessary in certain cases to establish a definitive diagnosis.

The treatment for volvulus is contingent upon whether the bowel is strangulated. In cases of non-strangulated volvulus, the therapeutic objectives involve relieving torsion through decompression via methods such as barium enema, colonoscopy, or elective surgery, with a focus on preventing recurrence. In our patient, although there was no clinical or radiological evidence of strangulation or perforation, a left colectomy was performed as a preventive measure against the recurrence of volvulus.

Strangulated volvulus, on the other hand, constitutes a surgical emergency requiring immediate operative reduction and carries a serious prognosis.

Conclusion

Colonic volvulus represents a rare but potentially life-threatening condition requiring prompt diagnosis and intervention. Clinical manifestations are often nonspecific and may mimic other gastrointestinal pathologies, including acute diverticulitis and bowel obstruction. Imaging modalities, particularly contrast-enhanced CT and barium enema, are essential for diagnostic confirmation, localization, and evaluation of the extent of torsion. CT is particularly valuable in identifying complications such as strangulation or perforation, thus facilitating appropriate therapeutic planning.

Predisposing factors include anatomical variants such as an elongated mesentery and redundant colon. A persistent left mesocolon, a rare congenital anomaly, may contribute to volvulus of the descending colon by permitting excessive colonic mobility and loop formation.

This case underscores the importance of recognizing anatomical variations in the pathogenesis, diagnosis, and management of colonic volvulus. Early imaging and prompt surgical intervention are critical to optimizing patient outcomes.

Patient consent

Informed written consent was obtained from the patient for publication of the Case Report and all imaging studies. Consent form on record.