Peritoneal encapsulation: a rare cause of small bowel obstruction

Abstract

Peritoneal encapsulation syndrome (PES) is a rare cause of small bowel obstruction (SBO) in patients with no prior history of abdominal surgery. First described by Cleland in 1868, PES is a congenital condition characterised by small bowel encasement in an accessory, but otherwise normal peritoneal membrane. ^{1 2} A result of abnormal rotation of the midgut during early development, the condition causes fibrous encapsulation of the intestines, thus preventing bowel distention.³ While preoperative diagnosis is difficult, several case reports have described clinical and imaging signs that can help clinicians with not only recognising the condition but also preparing appropriately for perioperative discovery of anatomical variants. ^{3 4}

Background

Small bowel obstruction (SBO) is an important cause of morbidity worldwide, accounting for up to 15% of surgical admissions for acute nontraumatic abdominal pain.⁵ While adhesion formation and hernias are commonly associated with SBOs, maintaining a broad differential diagnosis is important for any physician evaluating these patients. Our patient presented at age 38 with no prior surgical history and a 24-hour history of abdominal pain with associated nausea, emesis and abdominal distention. Obstruction secondary to an internal hernia sac visualised on CT scan was suspected as the initial aetiology. However, on exploratory laparotomy the small bowel was found to be encased in a hernia sac, and a congenital band causing a closed loop obstruction was visualised with an associated anomalous artery. These findings are consistent with peritoneal encapsulation syndrome (PES), a rare yet clinically important cause of SBO that deserves recognition among clinicians worldwide.

Case presentation

A 38-year-old male patient presented to the emergency department of our hospital with a 24-hour history of severe, sharp, right lower quadrant abdominal pain with associated abdominal distention, nausea, several episodes of emesis and back pain. This patient had no previous history of abdominal surgery, and his medical history was notable only for hypertension. Physical examination revealed an ill-appearing man in distress. His pulse was 74 beats/min, temperature was 36.6°C, blood pressure was 137/85 mm Hg. There was no cyanosis or jaundice, and no abnormalities of the chest or cardiovascular system were noted. Examination of the abdomen revealed firmness with moderate distension and diffusely tympany to percussion with voluntary guarding on palpation of the left abdomen with a soft, non-distended right abdomen. Examination was negative for rebound tenderness. There was no hepatomegaly or splenomegaly noted.

Investigations

Routine laboratory workup revealed a total leucocyte count of 22.05x 10⁹/L, haemoglobin of 145 g/L and normal serum chemistry except for an elevated anion gap of 18 mmol/L. Serum lactate was significantly elevated at 3.3 mmol/L. Liver function tests, lipase and urinalysis were unremarkable. CT scan of abdomen and pelvis (figure 1) revealed multiple dilated loops of bowel which appeared to be contained within a hernia sac, consistent with an internal hernia and resulting in a closed loop obstruction due to a congenital band.

Figure 1.

Preoperative CT scan demonstrating multiple loops of bowel encased in a hernia sac. SMA, superior mesenteric artery; SMV, superior mesenteric vein. The normal orientation of these two structures rules out a complete malrotation.

Differential diagnosis

The differential diagnosis included an internal hernia due to congenital adhesions, partial malrotation with volvulus and a paraduodenal hernia.

Treatment

The patient was started on intravenous fluids and antibiotics due to concern for an intra-abdominal infection, and a nasogastric tube was placed. Given his CT findings and accompanying lactic acidosis, he was taken to the operating room emergently for an exploratory laparotomy.

On opening the peritoneum, there was evidence of a large hernia sac in the mid abdomen slightly to the left of midline, which appeared to contain most of the small bowel. Congenital adhesions were noted between the omentum and left upper quadrant, as well as between the hernia sac and the left peritoneal reflection. There was no evidence of a defect in the transverse colon mesentery and the entire colon appeared to have normal retroperitoneal attachments. Adhesiolysis was performed, and the hernia sac was opened. Decompressed proximal small bowel with relatively dilated mid small bowel and decompressed distal small bowel was visualised, along with a twisted mesentery. Lysis was performed of a congenital adhesive band from the base of the mesentery in the left abdomen to the right lower quadrant along the mesentery of the terminal ileum, which relieved the closed loop obstruction. An aberrant artery and vein were then discovered, initially presumed to be the right gonadal artery and vein, but ultimately found to be an aberrant unnamed vessel. These vessels were ligated following skeletonisation and vessel looping to confirm bowel viability in their absence, as their position crossing the terminal ileum posed a significant risk of subsequent reherniation beneath them. The hernia sac was not fully excised, as it was connected to the peritoneum in several places. The entire small intestine was run proximally from the ligament of Trietz to the ileocecal valve with no evidence of ischemia or serosal injury.

Outcome and follow-up

The patient’s postoperative recovery period was complicated by a community-acquired pneumonia diagnosed on the second postoperative day and treated with antibiotics. He demonstrated return of bowel function on the third postoperative day, and was subsequently discharged on the fourth postoperative day. Now, 4 months after surgery, he is doing well and has returned to his normal activities without any limitations or further symptoms.

Discussion

This condition was first documented in the UK by Cleland in 1868, though it was first observed about 10 years prior.¹ A Medline search revealed that only 29 cases have been reported since then worldwide, with only one case documented in the USA in Chicago in 1992.⁶ PES should not be confounded with abdominal cocoon syndrome, characterised by total or partial encasement of the small bowel in a fibrocollagenous cocoon-like sac with extensive intrinsic small bowel adhesions, or with retroperitoneal fibrosis, characterised by retroperitoneal tissue fibrosclerosis often encasing the ureters.^{2 7} Of note, several cases with features more consistent with abdominal cocoon syndrome have been reported as PES.⁸ Another similar yet unique condition is sclerosing encapsulating peritonitis, in which the small bowel is covered by a dense grey collagen membrane with a clearly suspected underlying aetiology.⁹

PES is a congenital condition, thought by some to be caused by malrotation of the midgut during development.³ Others, however, believe its underlying aetiology is related to the chorionic cavity entering the abdomen with the intestines during development instead of remaining at the base of the umbilical cord.¹⁰Patients typically present with acute gastrointestinal symptoms such as abdominal pain, nausea and emesis; however, several reports have described a history of episodic pain that resolved spontaneously in the past.^{6 11 12} Many reports have also described asymptomatic patients in which the condition was diagnosed either incidentally at laparotomy or found at autopsy.^12–17 Though the condition may present as an isolated anomaly, it has also been described with incomplete situs inversus.¹⁸

Preoperative diagnosis is difficult but possible if clinical suspicion is high. One report discusses two clinical signs typically indicative of PES: fixed, asymmetrical distention of the abdomen and palpating different consistencies of the abdominal wall. While the flat area of the abdomen should be firm due to the dense fibrous capsule, the distended area should be soft.³ Conventional radiographs are typically consistent with bowel obstruction, as are CT images. Mitrousias et al believe preoperative diagnosis of this condition is aided by identification of a ‘helix sign’ on CT scan in which the loops of bowel are visualised in a pinwheel-type pattern.⁴

A commonality among all patients with PES is intraoperative discovery of a sac morphologically similar to peritoneum encasing the small bowel, though some reports such as ours also describe an obstructive band and associated aberrant artery. In these reports, the band was divided to relieve the obstruction, and its associated vessel was observed to divide into two branches above the terminal ileum.^19–21 Histological examination of the sac typically reveals mesothelium of peritoneal origin covering fibrovascular tissue.²²

Complete sac excision, band division and aberrant artery division is indicated to reduce risk of recurrence or further complications, even if found incidentally.²⁰ Histological analysis of the excised sac can be performed to confirm the diagnosis or to exclude any concerning pathologies, if necessary. Laparotomy has been the mainstay of treatment for this condition, though a laparoscopic approach may be possible if the condition is properly diagnosed preoperatively.⁴ While overall prognosis of PES is excellent and recurrence has yet to be described, it should not be considered a harmless condition. Not only does the condition pose an inherent risk of strangulation and consequent bowel necrosis requiring partial excision, but acute aortic occlusion secondary to extrinsic compression from the bowel sac has also been described.^{6 23}

Learning points.

• A combination of vigilant and informed clinical and radiologic examinations can not only aid in the detection of peritoneal encapsulation syndrome (PES) but also reduce perioperative and postoperative complications.

• Awareness of radiographic signs associated with PES may allow for preoperative detection of the condition, which can allow for a more informed preoperative discussion about the expected outcomes.

• Early detection can help surgeons adequately prepare for perioperative procedures, and help them detect anatomic abnormalities that might lead to subsequent obstruction or infarction.

• Accurate preoperative diagnosis may allow surgeons to first employ a laparoscopic approach, rather than a more invasive laparotomy.