Mesosigmoid Fossa Herniation: A Case of Jejunal Obstruction

Introduction

The protrusion of small intestine, omentum, or other abdominal organs through a normal or abnormal aperture within the peritoneum or mesentery is called an internal hernia, which can lead to strangulation, ischemia, or perforation [1]. The hernia sack may be either a normal anatomical structure or a pathological or congenital deficiency. Internal hernia is an extremely rare situation, leading to small-bowel obstruction [2,3]. There are many types of internal hernias, such as paraduodenal hernia, which is the most common, accounting for more than half (53%) of reported cases of internal hernias. Other types include pericaecal hernia (13%), internal hernia of foramen of Winslow (8%), transmesenteric hernia (8%), transomental hernia (1–4%), and pelvic internal hernias (6%) [4]. Hernias that occur through the mesocolon of the sigmoid account for less than 6% of all cases of internal hernias [5]. The sigmoid mesocolon is a folding of the peritoneum that attaches the sigmoid colon to the pelvic wall. The mesocolon apex is a V-shaped pocket that lies in front of the left ureter and the left common iliac vessels and can be a site of internal hernia. This pocket varies in size, from small holes to great fossae [6]. This mainly congenital fossa can form when the fusion of the left part of the peritoneal surface of the sigmoid mesocolon and the parietal peritoneum of the posterior abdominal wall does not complete successfully during the fifth month of the fetal life [7]. Although most intersigmoid herniation cases occur due to congenital causes, the mean age at diagnosis is 38 years [8].

The preoperative diagnosis of internal hernias can be very difficult, especially those that involve the mesosigmoid. The clinical signs are not specific, so there is a high risk of delaying the diagnosis and treatment, which is surgical. To prevent the risk of malpractice, an abdominal CT can be a valuable diagnostic tool letting the surgeon understand the location of the obstruction [9]. A C-shaped (or sometimes U-shaped) cluster of dilated intestinal loops is the characteristic CT sign. The bowel loop is depicted to be entrapped lateral and posterior to the sigmoid colon, with displacement of the sigmoid anteromedially [10].

Treatment of internal hernias largely depends on the severity. Internal hernias sometimes resolve without surgery, using conservative measures such as food restriction and increased fluid intake. However, surgery is sometimes inevitable, and can be either open or minimally invasive, according to the severity [7].

Diagnosis of mesosigmoid internal hernia mainly occurs in the operating room by surgical exploration. The earlier the surgery takes place, the better the outcome will be. If the strangulated bowel is untreated, the internal hernias can lead to critical situations, as mortality occurs in about half of such cases [11,12]; decompression of the bowel and/or resection of any perforated part should occur as early as possible to avoid symptoms of peritonitis [13].

Case Report

A 47-year-old woman, without any medical history except being allergic to paracetamol and penicillin, was admitted to the Emergency Surgical Department with a 24-hour colic pain that started at the epigastrium and then shifted to the left pelvic region. She also reported several episodes of “green/brown-color” vomiting in the past 12 hours, also known as feculent vomiting. Furthermore, our patient had anorexia, constipation, and bloating for the last 4 days, but never had constipation. The patient had no history of similar abdominal pain episodes or any abdominal surgical procedures. Lastly, the patient did not report any use of alcohol or tobacco.

Her vital signs were normal, the heart rate was 68 pulses per minute, the levels of arterial blood pressure were 132/73 mmHg, the oxygen saturation level measured by a pulse oximeter was 98%, and body temperature was 36.4°C. The clinical examination revealed abdominal distention and an overall tenderness, especially in the right iliac region. Auscultation revealed tinkling bowel sounds.

ECG detected negative precordial T waves, so a bedside ultrasound examination was performed. Life-threatening cardiologic events were excluded by ultrasound and normal troponin and D-dimer levels.

The laboratory analysis of blood revealed increased white blood cells (WBC) at 13 360/μL (normal range: 4000-11 000/μL). Neutrophils were 11 700/μL (87.6% of total WBC – normal range: 40–70%), while other blood test results were within normal limits.

The chest X-ray was normal, but an erect abdominal X-ray revealed a small-bowel dilatation. Several dilated intestinal loops were also recognized on X-ray, and some gas-fluid levels were also recognized in the small intestine (Figure 1). The findings could set the diagnosis of intestinal obstruction, also implying that an umbilical hernia must be considered in the differential diagnosis. A nasogastric tube was placed to relieve pressure.

Due to the differential diagnostic issues, abdominal CT was performed, showing a C-shaped cluster (Figure 2) of small-bowel loops (jejunum) posterior and lateral to the sigmoid colon, between the psoas muscle and the sigmoid colon. Moreover, there was displacement of the sigmoid anteromedially due to mass effect (Figure 3A). The end of the loop segment and sigmoid vessels converged to the same point (intersigmoid fossa). Dilated loops of proximal small bowel, compared with normal distal small bowel, suggested the need for emergency surgery. Moreover, CT showed fluid collection to the peritoneal cavity, mainly in the left paracolic gutter (Figure 3B).

The patient underwent an exploratory laparotomy, during which an entire loop of jejunum was surprisingly recognized within the intersigmoid fossa (Figure 4A, 4B). It was attached to the mesosigmoid bowel and was easily extracted out of the fossa, then the fossa (Figure 4C) was sutured. A slight erythema was noticed in the extracted bowel. This part of the bowel was examined carefully and it was decided that there was no need for a bowel resection, as the operation was performed in just a few hours.

The patient’s postoperative period at the Surgical Department was without any complications and she was discharged on the 5th postoperative day. Follow-up at 20 days after surgery showed normal wound incision healing and the patient reported no digestive tract or other symptoms. The patient was examined 6 and 12 months after the operation, at the outpatient department, without any remarkable findings.

Discussion

Internal hernias can be caused by postoperative or congenital issues. This type of hernia occurs because the viscera protrude through the mesentery or the peritoneum and into recesses. Mesosigmoid internal hernias are rare [8]. The turning point of the sigmoid colon is where the mesocolon often has a defect called an intersigmoid fossa. Although we think of it as a rare anatomical variation, a 2017 cadaver study found intersigmoid fossa was present in three-quarters of cadavers examined [14].

In 1964, Benson and Killen published their “Internal Hernias Involving the Sigmoid Mesocolon” article, proposing classification of sigmoid mesocolon hernias into 3 categories:Transmesosigmoid hernia: This hernia does not have a sac, and the loops of the small intestine pass through a defect in the sigmoid mesocolon.Intersigmoid hernia: The herniation occurs into the inter-sigmoid fossa.Intramesosigmoid hernia: It is not directly connected with the intersigmoid fossa. The hernia’s sac is a congenital defect lateral to the mesosigmoid, at the lateral peritoneal wall [15].

Preoperatively distinguishing between the last 2 subtypes (intersigmoid and intramesosigmoid) is neither easy nor essential, and the differential diagnosis may include other conditions, such as adhesive small-bowel obstruction. The diagnosis is confirmed only in the operating room, either with laparoscopy or with laparotomy [2]. Distinguishing between intersigmoid and intramesosigmoid hernia by CT findings is not necessary, because the treatment, mortality, and morbidity are similar [16]. On the contrary, transmesosigmoid hernia has both a higher percentage of bowel resection compared to the other 2 types (transmesosigmoid hernia ~50%, intersigmoid hernia: 18.8%, intramesosigmoid hernia: 13.8%) and a higher death rate (transmesosigmoid hernia: 7.1%, intersigmoid hernia: <0.1%, intramesosigmoid hernia >0.1%) [17]. There are more cases of small-bowel resection in transmesosigmoid hernias than in intersigmoid or intermesosigmoid hernias because the small-intestine loop that passes through the mesosigmoid defect is usually longer and can be easily strangulated. On the other hand, the intersigmoid fossa cannot create a large cavity, so the herniated loop is often short. Therefore, there tends to be less strangulation and intestinal necrosis, with less need for intestine resections. [18].

In our patient, the radiographic findings revealed not only the bowel obstruction but also the “C-shaped cluster” that was pathognomonic for the intersigmoid hernia. According to the literature, the criterion standard treatment of intersigmoid hernias is surgical release of the obstructed segment from the intersigmoid fossa. In some cases, bowel excision should be considered. In our patient, the segment of the small intestine that was “trapped” did not seem to need excision. In a 30-year literature review by Chiarini et al, only 32 out of 106 cases needed bowel excision of the incarcerated/perforated segment [9]. Delayed surgery can cause increased incarceration [7].

Conclusions

Internal hernias are rare, and sigmoid mesocolon hernias are even less frequent than other types. This type of hernia often establishes a small-intestine obstruction or even ischemia and perforation if untreated.

A plain abdominal X-ray can help find an obstruction, but the cause of the intestinal obstruction can be identified only by CT scan of the abdomen and pelvis. The “C-cluster” sign on the CT images is the diagnostic key to sigmoid mesocolon hernias identification.

To reduce the risk of delayed diagnosis, as well as associated mortality and the morbidity, of internal hernias of the sigmoid mesocolon, surgeons need to be aware of the anatomical variations and the pathological dynamics of these hernias. Except for congenital mesosigmoid fossae, there are also acquired postoperative mesocolic deficits that should be taken into consideration. Finally, early intervention is vital and can determine whether bowel resection is needed.