Postoperative intestinal intussusception in children, an easily missed culprit of postoperative intestinal obstruction: Case series and literature review

Highlights • Most of our patients presented in the first two weeks after the primary operation and managed successfully with operative manual reduction with no postoperative complications.• Postoperative intestinal intussusception secondary to surgical reduction of ileocolic intussusception is an exceedingly rare cause of postoperative intestinal obstruction.• Usually, postoperative intestinal intussusception is misdiagnosed as postoperative adhesive obstruction.• Postoperative intestinal intussusception is challenging in diagnosis and needs a very high index of suspicion.• By keeping the possibility of POI in mind, one can easily diagnose it and prevent its consequences.


Introduction
There are many etiologies for intestinal intussusception though it is largely idiopathic in origin [1]. Less common causes include POI with reported incidence after laparotomies of 0.01 to 0.25% [2]. POI presents with bilious vomiting, high nasogastric tube output, abdominal pain or abdominal distension during the first two weeks postoperatively in 90% of patients [3,4]. Because POI is a forgotten cause of postoperative obstruction, and to increase the awareness of this rare entity, we present three cases of ileoileal POI and one case of ileocolic POI.

Case 1 [POI following a colostomy]
A two year-old female patient underwent exploratory laparotomy with end sigmoid colostomy after a penetrating rectal injury. The intraoperative and early postoperative periods were uneventful. After ten days following the surgery, the child presented three times with a picture of intestinal obstruction. However, at each time, she was admitted for two days, treated conservatively, and improved. One month following the surgery, she developed diffuse severe colicky abdominal pain with vomiting, diarrhea and abdominal distension. Abdominal standing x-ray showed multiple air fluid levels with dilated loops. She was taken to the operating  room and underwent a laparotomy and found an ileoileal intussusception. Manual reduction and resection of the necrotic part were performed. The child's postoperative course was uneventful.

Case 2 [POI following ileocolic intussusception]
A five-month-old female underwent surgical reduction of idiopathic ileocolic intussusception (Fig. 1). Initially, the infant did not tolerate the slow advancement of her diet and this was managed as postoperative ileus. The infant developed bilious vomiting on postoperative day seven. Her abdominal x-ray showed multiple dilated bowel loops. Abdominal ultrasound showed ileoileal intussusception. At laparotomy, an ileoileal intussusception was identified and reduced manually, with resection of a short necrotic segment (Fig. 2). Subsequently, the infant did very well and was discharged home.

Case 3 [POI following revision of an ileostomy]
A seven month-old male with Hirschsprung's disease, underwent a loop ileostomy at the age of 12 days due to intestinal perforation. At the age of three months, the infant presented with prolapse of his ileostomy necessitating revision of the ileostomy. Two months following laparotomy, the infant developed a prolonged course of watery diarrhea and malabsorption with poor weight gain. Cow's milk protein allergy was suspected and formula was changed with no improvement. At the age of seven months, the infant underwent pull through procedure. An ileocolic intussusception was identified incidentally and managed by manual reduction. The infant's stool production and intestinal absorption normalized after the reduction. His postoperative course was uneventful.

Case 4 [POI following a colostomy]
A six month-old male with Hirschsprung's disease, underwent laparotomy with leveling colostomy. Three days after the operation, the infant developed abdominal distention with bilious vomiting. Plain abdominal x-ray was performed and showed mul- tiple air fluid levels with dilated bowel loops. The infant failed to improve with conservative therapy. The patient was taken back to the operating room five days after the initial laparotomy and an ileoileal intussusception was identified and reduced manually. The infant progressed well postoperatively and was discharged home at POD5. Tables 1 and 2 summarize the clinical details and symptoms and signs experienced by our patients. Unfortunately, we did not perform genetic testing for any patient.

Discussion
Postoperative intestinal obstruction is a common problem encountered in children and is mostly attributed to intestinal adhesions and adynamic ileus [5,6]. One forgotten cause of postoperative intestinal obstruction is postoperative intestinal intussusception [7]. Postoperative intestinal intussusception (POI) was reported to follow many abdominal and non-abdominal operations. 51.2% and 20.5% of POI occurs in gastrointestinal tract and retroperitoneal tumor resection procedures respectively. Laparotomy, surgical reduction of ileocolic intussusception, and Hirschsprung's disease repair operations were all previously reported to be associated with POI [2].
The reported incidence of POI is 0.01-0.25% [2] with higher incidence rates in pancreatic resection operations of 2.1% [8] and abdominal tumor resection operations of 1.2% [4]. POI has higher incidence rates in males [2] and mentally disabled patients [6]. POI is not only a complication of pediatric procedures, it also has been reported in adult procedures albeit less commonly [9].
Being reported after many different primary surgeries, POI can have different underlying mechanisms. Although etiology of POI remains unclear, several theories were proposed to explain its pathophysiology, including early postoperative adhesions, excessive bowel manipulation, altered peristalsis, neurogenic factors, electrolyte disturbances, and medications (anesthetics and opioids) [10]. The most common site of POI is the small bowel with ileoileal intussusception predominance [2]. Other reported POI sites are jejunojejunal, jejunoileal, ileocolic and multiple intussusceptions. Ileoileal POI is frequently reported with abdominal procedures while ileocolic POI being reported more commonly with non-abdominal procedures [3].
The typical presentation of the idiopathic intussusception involves painful abdominal cramps, vomiting, a palpable abdominal mass, and rectal bleeding [2]. Lethargy and altered level of consciousness are reported as well [11]. Table 3 shows characteristics of non-postoperative intussusception and postoperative intussusception.
Unlike idiopathic intussusception, the POI frequently presents with non-specific "prolonged adynamic ileus" [12] symptoms with bilious vomiting being the most commonly reported presentation. Abdominal distension and increased bilious nasogastric tube output are other common presentations, with rare reporting of restlessness, bloody stools and palpable abdominal mass [2,6]. Frequently, there is no identifiable lead point [13].
POI is challenging in diagnosis and needs a high index of suspicion, mainly due to its rarity, atypical presentation, and the abundance of postoperative adynamic ileus [6,13,14]. Frequently, POI is misdiagnosed as postoperative adhesive obstruction [5,15]. Helpful diagnostic tools may include abdominal radiograph, abdominal ultrasonography, contrast study and computerized tomography (CT) scan [3]. Abdominal radiographs may demonstrate air-fluid levels although it is of little diagnostic yield [3,5,16]. One can use abdominal ultrasonography to differentiate a mechanical obstruction from other causes of obstruction (i.e. ileus) with a high specificity of 100% and sensitivity of 89% [4,6]. Contrast studies are diagnostic in up to 95% of cases of small-bowel intussusception [12]. However, in one of our patients, the contrast study was not diagnostic.
Although 90% of POI patients present within the first two weeks following the operation [4], one of our patients had ileocolic POI two months after prolapsed ileostomy revision. One study reported a similar case with three months duration postoperatively [6]. However, some authors may consider this as a coincidental idiopathic intussusception occurring during postoperative period [3]. Table 4 shows characteristics of the previously reported ileoileal POI secondary to surgical reduction of ileocolic intussusception. Seven of nine patients were male with mean age of 6.2 months. All patients presented initially with bilious vomiting and abdominal distention. All patients presented and were managed successfully with manual reduction within the first week following the primary procedures. Interestingly, all cases of POI were reported to follow surgical reduction of ileocolic intussusception. But, no cases were reported to follow surgical reduction of ileoileal or other types of intestinal intussusception.
A late diagnosis of POI poses a risk of ischemia and necrosis, and need for subsequent bowel resection. It also increases the morbidity and mortality [2,5,17], underscoring the need for early diagnosis and prompt management [14]. The mortality of POI was found as high as 6%-7% [15]. POI is usually managed by operative manual reduction with resection and anastomosis in select cases [2,10]. Two of our patients were found to have patches of necrosis and one of them  needed a bowel resection. Interestingly, some reported cases resolved spontaneously [3,18]. Hydrostatic reduction can be employed in cases of non-abdominal operations or abdominal operations without anastomoses [2,6]. Suggested preventative measures for POI include gentle handling, avoidance of desiccation of the bowel and using a minimally invasive approach [3,10].

Conclusion
Frequently, POI is misdiagnosed as postoperative adhesive obstruction. POI is a rare cause of intestinal obstruction with POI after surgical reduction of ileocolic intussusception being an extremely rare variant. POI is challenging in diagnosis and needs a very high index of suspicion. Contrast studies and abdominal ultrasonography are diagnostic in the majority of cases.

Funding
No funding or grant support.

Ethical approval
The study is exempt from ethnical approval in our institution.

Consent
The patient consents were all obtained by the infants' parents. And all parents accepted the final edition of the article.