Congenital pouch colon and segmental dilatation of the colon: A report of two unusual cases.

This report describes two unusual cases of anorectal malformation. The first had a type III congenital pouch colon with a colovesical fistula. In the other very similar case, segmental dilatation of the colon was present along with penoscrotal hypospadias and, distally, a length of normal colon ending in a rectourethral fistula. In both patients, the appendix was short, stubby and a Y-shaped duplication of the normal colon was present just proximal to the dilated segment of colon.

INTRODUCTION

Congenital pouch colon (CPC), also termed as ‘pouch colon syndrome’,[1] is an unusual abnormality in which a pouch-like dilatation of a shortened colon is associated with an anorectal malformation (ARM) and high-grade vesicoureteral reflux. This malformation has most frequently been reported from centers in northern India.[1-4] CPC has been categorized into four subtypes.[1] In the more severe variety, either the normal colon is absent with the ileum opening directly into the colonic pouch (type I), or there is a short segment of cecum proximal to the pouch (type II).[1] The less severe varieties (types III and IV CPC) have a longer segment of normal colon proximal to the colonic pouch.

Segmental dilatation of the colon (SDC) is a rare entity, usually reported in children beyond the neonatal period.[5] There are only a few reports of patients with SDC associated with an ARM.[6-11] This report describes two unusual cases of ARM, the first of whom had a type III CPC with a colovesical fistula. In the other very similar case, SDC was present along with hypospadias and, distally, a length of normal colon terminating in a rectourethral fistula. In both patients, there was a Y-shaped duplication of the normal colon just proximal to the dilated segment of colon. To the best of our knowledge, similar cases have not been reported in the literature.

CASE REPORTS

Case 1

A full-term, 7-h old, 2 kg weight, male child was brought with absence of the anal opening. There was no other obvious associated congenital anomaly. An invertogram suggested a high ARM. The sacrum was normal. Laparotomy, performed via a left lower quadrant incision, revealed a type III CPC with 10 cm of normal colon proximal to the colonic pouch [Figure 1]. The appendix was short and stubby. Distal to that, the normal colon branched in a Y-shaped fashion into two limbs of equal caliber, both communicating with the colonic pouch. Membranous atresia of the lateral limb was present, just distal to its site of origin from the normal proximal colon [Figure 1]. The pouch, which lacked tenia coli and haustrations, narrowed distally to a colovesical fistula at the level of the bladder neck. Both ureters were grossly dilated. The pouch was decompressed by an incision on its anterior surface and a divided colostomy was constructed in the normal colon proximal to the duplication. Postoperatively, however, the baby developed septicemia and succumbed to septicemic shock.

Figure 1

Case 1. Operative view showing the colonic pouch and the Y-shaped duplication of the proximal colon with membranous atresia of the lateral limb of the duplication (black arrow). There is a gap in the mesentery (white arrow) and an incision to decompress the colonic pouch (arrowhead)

Case 2

A one-day old, 2.5 kg weight, male baby was brought with absence of the anal opening, meconuria, and gross abdominal distension. Apart from penoscrotal hypospadias, there was no obvious congenital malformation. An invertogram revealed a large air-fluid level on the left side of the abdomen suggestive of a type I/II CPC malformation. The sacrum was normal. Laparotomy revealed a grossly distended pouch-like segment of colon with 6 cm of normal colon proximal to the dilated segment [Figure 2]. The dilated segment of colon was supplied by a prominent branch of the superior mesenteric artery (SMA) along its outer or lateral aspect. The appendix was short and stubby. The distal portion of the normal proximal colon had branched in a Y-shaped fashion with a short, narrow medial limb and a wider, longer lateral limb, both of these opening into the distended colonic segment. Distal to the dilated colonic segment, colon of normal caliber could be seen extending into the pelvis behind the urinary bladder. The smaller medial communicating limb was divided and closed by interrupted sutures at both ends, and a divided colostomy was constructed proximal to the dilated colon in the wider lateral limb of proximal colon. The recovery was uneventful. A distal colostogram, performed at the age of six months, revealed that the colon distal to the dilated segment terminated in a long fistula communicating with the urethra proximal to the penoscrotal urethral meatus [Figure 3]. The child is at present awaiting definitive surgery.

Figure 2

Case 2. Photograph taken during surgery showing the dilated colon and the Y-shaped duplication of the normal proximal colon. The narrow medial limb of the duplication has been divided. Note the short, stubby appendix (arrowhead)

Figure 3

Case 2. Distal colostogram showing the colon ending in a long, narrow rectourethral fistula opening (arrow) proximal to the hypospadic urethral meatus

DISCUSSION

Although the two cases reported here are strikingly similar, the presence of normal colon distal to the pouch-like colonic dilatation led to the second patient being termed as having SDC associated with an ARM. However, as with CPC, the overall length of the colon was short and there was a short, stubby appendix, a finding that has often been reported with types I-III CPC.[1-4]

The similarity between CPC and SDC has been noted previously.[1312] Characteristic features of SDC include abrupt transition to normal proximal and distal colon,[13] hypomotility of the dilated segment, absence of tenia coli, and abundant serosal vascularization fed by a large, marginal colonic artery.[13-15] All these features, apart from normal colon distal to the colonic pouch, are seen in pouch colon malformations.

The embryopathogenesis of CPC is a matter of speculation.[341617] There are two reports of patients with findings very similar to those seen in our second case. Mathur et al.[7] reported a newborn with the ileum opening into a pouch-like SDC involving the cecum and ascending colon. The rest of the colon, distal to the colonic sac, was of normal caliber and ended in a colovesical fistula. The authors suggested that intrauterine obliteration of the ileocolic branch of the SMA may have been responsible for the abnormality, as distal to the dilated segment, the colon was normal.[7] Mahajan et al.[8] reported a newborn male with SDC involving the ascending, transverse, and descending colon. The cecum and appendix were normal and opened into a pouch-like SDC. The pouch lacked haustrations, appendices epiploicae and tenia coli, and continued into sigmoid colon of normal caliber going deep down into the pelvis behind the bladder.[8] According to the authors, from the anatomy of their case, it could be seen that the defective segment of the intestine, which undergoes dilatation, may not always be close to the URS.[8] The embryogenesis of both CPC and SDC may be quite similar, the main difference being that in SDC the faulty organogenesis does not involve the terminal hindgut and there is a length of normal colon distal to the dilated portion.[8]

There are also a few reports of boys who had a double colonic pouch with a short segment of normal colon between the pouches, the distal pouch terminating in a colovesical fistula.[61819] In a recent report, this group of patients has been categorized as type V CPC.[20] It has been suggested that in these patients, ‘defective organogenesis’ may have occurred at two sites in the terminal hindgut close to the primitive cloaca, with a normally developed segment of colon in between.[6] The distal segment would dilate to form the colonic pouch with the colovesical fistula, while the proximal portion would form the dilated segment of colon suggestive of SDC.[6]

Y-shaped tubular duplications of the colon in association with ARM are exceedingly rare.[21] The Y-shaped duplication of the colon in our patients with, in one child, membranous atresia of the lateral limb of the duplication, is very difficult to explain. However, considering that in types I-III CPC, the colonic pouch has a tenuous blood supply along its outer or lateral aspect from a terminal branch of the SMA,[13] it is possible that an ischemic accident during later gestation may be the responsible factor. Significantly, ileal or colonic duplications have been reported earlier in association with both CPC[1318] and segmental dilatation of the intestine.[2223]