Incomplete common mesentery results from a rotation anomaly of the digestive tract, the prevalence of which is estimated at between 0.5% and 1% of the world population based on autopsy series [1].

During embryological development, the primitive intestine undergoes 3 rotations of 90° each [2]. When intestinal rotation stops at 180°, the position known as incomplete common mesentery is reached, resulting in the cecum rising upwards and to the right in a sub-hepatic position, with the duodenojejunal angle to the right of the rachis. The first jejunal loop and the last ileal loop are therefore located next to each other.

The position of the cecum forms an abutment between the cecum and the right upper parietal peritoneum known as Ladd's Bride.this position is at high risk of volvulus given the proximity of the first and last loop of the cecum.

Clinically, uncomplicated incomplete common mesentery is often asymptomatic or manifested by nonspecific abdominal symptoms such as chronic pain and diarrhoea, and can be diagnosed in a wide variety of circumstances, usually incidentally on radiological examination, or rarely during surgery, as in our case [3].

In these asymptomatic patients, the diagnosis may be revealed during attacks of ectopic appendicitis [12] or by chance during radiological examination. Complications of intestinal rotation anomalies can be acute or chronic in adults. Acute complications include duodenal flange occlusion and total volvulus of the small bowel, which remains exceptional in adults, but has a dreadful prognosis. Chronic complications arise from incomplete duodenal stenosis or chronic small bowel volvulus with mesenteric arterial insufficiency. The diagnosis of total small bowel volvulus can be made in a wide variety of circumstances: in an emergency, in the face of acute intestinal obstruction, or even a state of shock [13] that can lead to death.

The gold standard for diagnosing an incomplete, uncomplicated common mesentery is an abdominal CT scan, which shows Treitz's angle, the whole of the small intestine to the right of the spine, the cecum in a subhepatic position and malposition of the mesenteric vessels, with the superior mesenteric vein directly behind the superior mesenteric artery. Abdominal MRI provides the same results as CT. Abdominal Doppler ultrasound is of little interest, but in certain cases it can visualize malposition of the mesenteric vessels [3].

Ladd's procedure is the reference treatment for volvulus on incomplete common mesentery, and consists in detorsion of the small intestine, release of the cecum, appendectomy in principle and placement in complete common mesentery at 90° [2]. Appendectomy in principle is performed because of the risk of diagnostic delay when placing the patient back in complete common mesentery at 90°, as the appendix will be in the left iliac fossa in this situation [4].

Pexy is of no interest, as it does not prevent the intestine from returning to the malrotation position, and may even lead to complications such as internal flanges and hernias [2].

When an incomplete common mesentery is discovered incidentally on radiology or intraoperatively, there is no consensus in the literature on whether to perform a prophylactic or elective Ladd procedure [5]. Some authors believe that all malrotations should be operated on [6]. The elective Ladd procedure in adults presents few post-operative complications, the most dreaded of which is occlusion due to post-operative flange formation [3,7]. Laparoscopy presents fewer complications than laparotomy, with less risk of post-operative flange formation, and remains a less invasive approach [8].

Laparoscopy is contraindicated in cases of volvulus on incomplete common mesentery [2]. In our case, there were no post-operative complications.

It is estimated that the prevalence of these congenital malformations in adulthood is in the order of 0.2% to 0.5% [10,11], at which age they very often remain asymptomatic and therefore undiagnosed.