腹膜包裹症-小肠梗阻的罕见原因

Peritoneal Encapsulation(腹膜包裹) - A Rare Cause of Small Bowel Obstruction

Abstract

Peritoneal encapsulation (PE) is a rare anatomic anomaly(解剖异常) which occurs due to an accessory peritoneal sac(副腹膜囊) covering the small bowel which can cause chronic recurrent abdominal pain and even small bowel obstruction, most often in children or patients with no previous surgical history.The diagnosis is usually made during surgery, but recently it has been suggested that mindful(留神的) examination of the abdominal CT may be helpful in considering PE beforehand. We present the case of a 21-year old patient who was admitted due to intense abdominal pain, asymmetrical(不对称的) abdominal distension, air fluid levels on the abdominal X-ray, but no specific findings on the abdominal CT. He underwent emergency surgery and PE was found and the peritoneal sac was excised. The postoperative course was uneventful. Histopathologic examination of the specimen confirmed the diagnosis. PE is often misdiagnosed as abdominal cocoon or sclerosing encapsulating peritonitis, but it is a pathology with a much lower rate of recurrence and postoperative complications, which can be treated successfully if the surgeon is aware of this pathology when making the differential diagnosis.

Introduction

First reported by Cleland in 1868, peritoneal encapsulation is an abnormal secondary peritoneal sac that encompasses the entire small intestine and communicates with the bigger peritoneal cavity through a small aperture（孔） at the ileocecal junction（回盲交界处）. Very few cases have been reported in literature, the diagnosis usually being made during surgery, with some authors suggesting more recently that a preoperative CT diagnosis is possible .

We report a rare case of acute small bowel obstruction in a 21-year old male with no significant medical history, no previous abdominal surgeries and no previously diagnosed hereditary conditions（遗传性疾病）.

Case report

A 21-year old man was brought to the emergency room complaining of intense diffuse abdominal pain that had debuted（首次出现） 12 hours prior associated with non-bilious vomiting and the absence of bowel movements for 4 days. At admission the patient had no fever and the vital signs were normal.

The physical examination revealed moderate abdominal distension, slightly asymmetrical –favouring the left abdomen (which worsened after admission) with tenderness in the left upper and lower quadrants. Rectal examination revealed the absence of stool in the anal canal（肛管） and lower rectum. The white blood cell count was 14370/mm³ (84.7% neutrophils中性粒细胞), with normal findings across the rest of the blood panel.

The abdominal ultrasound showed dilated bowel loops in the central abdominal and pelvic regions and the intestinal wall was apparently thickened. No free fluid was visible in the abdominal cavity. A plain abdominal X-ray revealed a slightly dilated small bowel loop (maximum diameter of 38 mm), with multiple air fluid levels, located in the lower left quadrant, with no signs of pneumoperitoneum（腹腔积气）. An emergency contrast enhanced abdominal computerized tomography (CT) was performed, which revealed a distended stomach, duodenum and small bowel loops (Fig. 1), with multiple intraluminal（腔内） air fluid levels, thickened walls, with no signs of acute vascular distress. In the right lower quadrant, there was an area of abrupt transition（突然过渡） from a dilated bowel loop to normal-looking loops, with no visible cause for obstruction.

Considering the CT diagnosis of small bowel obstruction of uncertain cause with no other significant findings, an emergency diagnostic laparotomy was performed (Fig. 2). Upon entering the abdominal cavity, an unusual nonwhitish(非白色) peritoneal like membrane surrounding the entire small bowel was observed. It had similar features to the peritoneum and apparently（明显） it originated near to the duodeno-jejunal flexure（十二指肠空肠弯曲处）, went on to the mid transverse colon（横结肠中段） and downward from the greater curvature of the stomach（胃大弯） to the pelvic region. It communicated with the abdominal cavity through a small aperture（孔） in the ileocecal region（回盲部）, where it was bordered by the ascending colon which was in normal position (Fig. 3). Upon dissection of the sac, starting in the right iliac fossa（右髂窝）, viable（可行） if moderately dilated small bowel loops were identified, with sparse（稀疏） adhesions, mainly around the distal ileum（回肠末端）. Careful dissection of the entire small bowel and the sac were performed, with meticulous adhesiolysis（细致的粘连松解） and quasi-complete（几乎完全） resection of the capsule. Small bowel resection was not necessary, normal peristalsis（蠕动） was present throughout the entirety of the jejunum and ileum（空肠和回肠）.

The postoperative course was uneventful, the patient was discharged 4 days after surgery with no abdominal pain, restored and normal bowel movements and normal blood tests. Follow-up after one and six months revealed no postoperative issues, bowel transit and digestive tolerance were reported to be normal.

The histopathological(组织病理学) examination of the fragments of excised sac showed characteristics of fibrous and adipose tissue(脂肪组织) covered by mesothelium(间皮) of peritoneal（腹膜） origin, as well as inflammatory cells. There was no evidence of fungal（真菌） or bacterial infection.

Discussion

Peritoneal encapsulation is a rare anatomical finding, where an abnormal return of the midgut（中肠） into the abdominal cavity of the fetus（胎儿） during the 12th week of gestation（妊娠期） causes the covering layer of yolk sac（卵黄囊） to encapsulate the small bowel instead of remaining in the umbilical pedicle（脐蒂）. The peritoneal accessory sac covers the small bowel partially or entirely, can be covered by the greater omentum（大网膜） (but it can also be absent), and usually extends from the ascending and descending colon laterally, superiorly to the mid transverse colon and inferiorly to the pelvic parietal peritoneum. This pathology should be taken into consideration when a patient with no previous surgical history presents with symptoms indicating small bowel obstruction, with a higher degree of suspicion if the patient reveals past episodes of recurring abdominal pain with no discernable（可辨别的） cause, or upon physical examination, asymmetrical abdominal distension is observed. During surgery it is very important to recognize the secondary fold of peritoneum（腹膜次级皱襞） and to remove as much as possible. Simple adhesiolysis in areas susceptible for obstruction will not suffice（足够） and recurrence is to be expected.

Even though less than 60 cases have been reported in the medical literature so far, there are hypotheses that peritoneal encapsulation might be associated with other anatomical anomalies, such as situs inversus（内脏逆位） or congenital epigastric hernia（先天性上腹部疝）. This was not the case with our patient, no other abnormalities being identified during surgery.

There are at least two other pathologies that have been wrongly reported as peritoneal encapsulation, but upon further inspection, have been categorised as having different etiologies: sclerosing encapsulating peritonitis（硬化性包裹性腹膜炎）(SEP) and the abdominal cocoon.SEP is a condition that presents itself as a similar encapsulation of the small bowel, but with a thicker wall, more fibrous, of greywhite colour, being directly caused by certain specific aetiological factors（某些特定的病因因素）. The factor most often cited is chronic peritoneal dialysis, but recurrent peritonitis, ventriculo-peritoneal（脑室-腹腔） and peritoneo-venous shunts（腹膜-静脉分流术）, sarcoidosis（结节病）, tuberculosis, Mediterranean fever（地中海热）, protein-S deficiency, following liver transplantation, systemic lupus erythematosus（系统性红斑狼疮）, and fibrogenic foreign material（纤维化异物） have also been identified as causing SEP. Emergency surgery in SEP has a much higher mortality than true peritoneal encapsulation.The abdominal cocoon is another controversial concept, still under debate as to cause and potential treatment options, but so far theories most often indicated it might be caused by retrograde（逆行的） menstruation（月经来潮）, retrograde peritonitis（腹膜炎） and recurrent gynecological infections（复发性妇科感染）.

Conclusions

While peritoneal encapsulation is a rarely reported cause of small bowel obstruction, identifying certain aspects be it in the medical history of the patient or on the CT images can help the surgeon in choosing the right therapeutic approach.In this case, during emergency surgery, adhesiolysis with complete resection of the secondary peritoneal sac ensured a smooth postoperative course. During short-term follow-up, recurrence was not reported.