|Year : 2018 | Volume
| Issue : 6 | Page : 554-558
Type 5 congenital pouch colon and its embryopathogenesis
Department of Paediatric Surgery, Kota Medical College, Kota, Rajasthan, India
|Date of Submission||24-Jan-2018|
|Date of Acceptance||15-May-2018|
|Date of Web Publication||15-Nov-2018|
Department of Paediatric Surgery, Kota Medical College, Kota, Rajasthan
Source of Support: None, Conflict of Interest: None
Congenital pouch colon (CPC) is a rare variant of anorectal malformation. It has been classified anatomically into five types as per the length of colon involved. Type 5 is the rarest form of CPC with only six cases reported in the literature till date. It has been originally described as pouch-like (segmental) dilatation of the colon with intervening normal colon of varying length, the distal pouch opening into the genitourinary system with a fistula. We present here a 3-day-old male neonate with CPC Type 5, managed with excision of both pouches and end ileostomy; abdominoperineal posterior sagittal anorectoplasty is planned.
Keywords: Anorectal malformation, colovesical fistula, congenital pouch colon, double pouch colon, embryopathogenesis, Type 5
|How to cite this article:|
Gupta R. Type 5 congenital pouch colon and its embryopathogenesis. Med J DY Patil Vidyapeeth 2018;11:554-8
| Introduction|| |
Congenital pouch colon (CPC) is a rare variant of high anorectal malformation (ARM). The majority of cases of CPC have been reported from northern part of Indian subcontinent. It has been classified anatomically into five types as per the length of colon involved. Type 5 is the rarest form of CPC.,,,,, One more case of CPC Type 5 is being added to the six cases reported in the literature till date, and a brief review of embryopathogenesis of CPC is performed.
| Case Report|| |
A 3-day-old term male neonate (2300 g) presented to us with complaints of absent anal opening, progressive abdominal distension, and vomiting. There was no history of meconuria. On examination, the general condition of the child was poor. There were visible veins and visible bowel loops with marked abdominal distention. The perineum was flat with poorly developed gluteal folds and absent anal opening. There was no musculoskeletal deformity; ultrasonography of the abdomen showed bilateral normal kidneys. Abdominal radiograph (anteroposterior erect view) showed two large air-fluid levels on either side of the abdomen [Figure 1]. Invertogram showed rectal gas shadow above the pubococcygeal line, indicating high ARM.
|Figure 1: Upright abdominal radiograph showing two large air-fluid levels, one on the left side (red arrow) and other on the right side (blue arrow) of the abdomen; both these dilated loops are less than half of the abdominal girth. The absence of air in the lower abdomen is also seen|
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At exploratory laparotomy, Saxena-Mathur classification CPC Type 5 was found. Ileum was opening directly into a dilated segment (pouch) of the colon [Figure 2]; there was no appendix and tinea was absent on the dilated pouch. The pouch was communicating distally with normal looking intervening colon of approximately 2 cm length [Figure 3]. The distal pouch was opening into the middle of posterior wall of the bladder through a wide fistula. The vascular supply was from the superior mesenteric vessels. The middle colic and left colic vessels were absent and replaced by an abnormal arborizing vessel supplying both the pouches and the intervening colon. The colovesical fistula from the distal pouch was divided and ligated. Initially, it was decided to excise the distal pouch; however, after dissection, proximal pouch also turned dusky. Hence, the distal and proximal pouches along with intervening normal looking colon were excised and end ileostomy was performed. The histopathological examination of the specimen [Figure 4] revealed the disorganized muscles in the muscularis layer of pouch colon; the intervening colon had normal colonic histology. We planned for abdominoperineal posterosaggital anorectoplasty (AP-PSARP) at 3 months of age.
|Figure 2: Intraoperative photograph showing ileum (white arrow) abruptly opening into proximal pouch (green arrow) and interposed normal colon (blue arrow) ending into distal pouch (red arrow). Bladder (black arrow) retracted to visualize the anatomical details|
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|Figure 3: Intraoperative photograph showing double pouch colon with interposed normal colon (blue arrow); ileum (white arrow) abruptly opening (black arrow) into proximal pouch (green arrow) and distal pouch (red arrow) ending into colovesical fistula (gray arrow).Wide mouth Meckel's diverticulum is also seen (violet arrow)|
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|Figure 4: Pathological specimen of double pouch colon showing proximal end (white arrow) of proximal pouch (green arrow) stained with meconium, interposed normal colon (blue arrow) between the two pouches; distal pouch (red arrow) ending into colovesical fistula (grey arrow)|
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| Discussion|| |
CPC is a rare form of ARM, in which part of or the entire colon is replaced by a pouch-like dilatation with a fistula to the genitourinary tract. Size of the pouch may be variable ranging from 5 to 15 cm; wall is very thick, tenia coli are absent or poorly defined with the absence of haustration and appendices epiploicae. Transition between CPC and normal bowel is abrupt. Mesentery is short and poorly formed. Vascular supply is usually from branches of superior mesenteric artery.
CPC was placed in the group of “rare/regional variants” of the Krickenbeck International Classification, and majority of the cases have been reported from North India. It constitutes 17.22% of ARM cases from high volume institute of Northwest India. Incidence of CPC may be as high as 37% of the high-type ARM.
The most commonly accepted Narasimharao's classification (anatomical) divides CPC into four subtypes based on the length of normal colon proximal to the colonic pouch. The Type 5 was first described as presence of two pouches (variant) by Mathur et al., but it was first reported by Chadha et al., who described it as segmental dilatation proximal to CPC. Type 5 or double pouch colon has been described as pouch-like (segmental) dilatation of the colon with intervening normal colon of varying length between the two pouches, the distal pouch opening into the genitourinary system with a fistula. It has been previously described in only six cases in the literature, which has been summarized in [Table 1].,,,,, In 2007, it was suggested that Type V CPC should be added to the original Narasimharao's Classification (Type I–IV) which would include all the other variants of CPC, such as CPC with segmental dilatation of colon, CPC with prune belly syndrome (PBS), CPC with rectal atresia, and other variants; it was republished in 2015.
|Table 1: Summary of all previous cases of congenital pouch colon Type 5 including the present one|
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Meconuria was observed in only two out of seven male neonates with CPC Type 5 [Table 1].,,,,, On preoperative abdominal radiograph suggestive of Type 5, i.e., two large air-fluid levels in the lower abdomen (may be less than half of abdominal girth) were seen in three out of seven cases. The interposing normal colonic segment length ranged between 2 and 7 cm in all the cases [Table 1]. Resection of the distal pouch was performed in five cases,,,,, while resection of both pouches with end ileostomy was done in the first reported patient and the present case. In our neonate, the proximal pouch appeared dusky after dissection of the distal pouch; hence, it was removed. Preservation of proximal pouch along with the interposing normal colon is ideal.,,,, Tapering coloplasty of the proximal pouch with end colostomy was accomplished in two cases in the neonatal period,, while it was performed at the time of definitive surgery (AP-PSARP with an ileostomy cover) in one case. Tapering coloplasty of the proximal pouch may be deferred at the neonatal period and may be left in situ, as it returned to a normal caliber following ostomy of the normal interposing colon in one patient. Rawat et al. have suggested distal pouch preservation to gain length.
The etiology of Type 5 CPC has been hypothesized due to “vascular insult” with obliteration of ileocolic branch of superior mesenteric artery resulting in the formation of distal pouch and from the obliteration of inferior mesenteric artery, leading to the formation of the second pouch., The interposed segment of normal colon remains unaffected as its vascular supply through the middle colic branch of the superior mesenteric artery remains patent., As per Earlam, the severity and duration of the vascular insult affect the final outcome of the developing bowel. Mild insult results in aganglionosis, while different types of atresia are due to severe vascular insult. This “vascular insult” theory cannot explain the simultaneous occurrence of segmental dilatation and CPC with an intervening normal segment on the basis of vascular theory alone. This theory also fails to explain the presence of ARM and other associated malformations. Furthermore, the presence of high incidence of vesicoureteral reflux (VUR) cannot be explained by this hypothesis. As per the author, the embryological basis of different types of CPC may be explained by “defective mesenchyme formation during organogenesis,” leading to abnormal segment which would dilate to form the colonic pouch and segmental dilatation. This explains the presence of disorganized muscles in the muscularis layer of pouch colon, thinned out musculature (normal ganglionosis in colonic tissue), abnormal vascular pattern of the pouch, increase incidence of VUR (defective mesenchyme involved in the formation of bladder musculature [trigone]), and presence of segmental dilatation of colon, PBS, ileal or colonic duplications, appendiceal abnormalities,,,, and also its association with rectal atresia. Furthermore, characteristic features of segmental dilatation of colon such as abrupt transition to normal bowel (both proximal and distal), absence of tenia coli, absence of haustration, presence of ganglion cells, and marginal vascular pattern are similar to pouch colon malformation, suggesting common pathology. Embryologically, ARM is explained by Stephen's theory of incomplete downward growth of cranial fold (Tourneux fold) with failure of fusion of lateral fold (Retterer fold). Thus, “defective mesenchyme” due to abnormal mesenchymal precursor cells is hypothesized as cause for both ARM and different variants of CPC, resulting in defective organogenesis at multiple sites in the hindgut and primitive cloaca.
| Conclusion|| |
Type 5 is the rarest form of CPC. Its presentation is similar to the other variants. Abdominal radiograph may show two large air-fluid levels in the lower abdomen, suggestive of Type 5 CPC. Attempt should be made to preserve proximal pouch along with the interposing normal colon (ideal), though it may not be possible always (as in our case). The embryological basis of CPC may be explained by “defective mesenchyme formation during organogenesis,” which may also explain all the variants (associations).
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
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