Classification

The term short colon should not be used to describe this ARM. The short colon is a term that should be used exclusively for the condition seen in babies born with a shortened length of left colon, which is also narrow in caliber; these babies are usually born to diabetic mothers - there is no ARM. The condition of short colon was first classified by Chiba et al. (Table 11.2) [15].

According to the current definition of CPC, type 3 of this classification can be called congenital CPC. Type 5 including the abnormal vessels forms part of the CPC. CPC also needs to be differentiated from those cases with the congenital segmental dilatation of the colon, without any ARM [20].

Table 11.3 Types of CPC. Initially, in India, cases of types I and II were more commonly seen and accounted for more than 70% of cases until 1985. Interestingly, during the past two decades, it is types III and IV CPC that have become more common

Type I

Normal colon is absent and the ileum opens directly into the colonic pouch.

Type II

The ileum opens into a short segment of cecum, which then opens into the pouch.

Type III

Presence of a significant length of normal colon between the ileum and the colonic pouch.

Type IV

Presence of near-normal colon with only the terminal portion of colon (sigmoid and rectum) converted into a pouch.

The Length The Colon Newborn
Type I Type II Typ« III Typt IV

Complrlc IncompIeK

Fig. 11.1 Modified classification of congenital pouch colon (CPC)

For all descriptive purposes, the widely accepted classification is based on the length of normal colon present proximal to the dilated pouch, as given by Narsimha Rao et al. (Table 11.3; Fig. 11.1) [15].

Wakhlu et al. [19], with their large clinical experience in this field, have simplified the classification, basing it upon the length of normal colon and the management planning in relation to need for colo-plasty. They describe type A as a partial short colon, with at least 8 cm of colon proximal to the pouch. Their type B (or complete short colon) is where there is no normal colon, or a colon of less than 8 cm in length.

In the authors' view, the terms "incomplete" and "complete" CPC may be more appropriate. It is preferable that the term short colon should be avoided to avoid confusion in terminology. It is also feasible to use the remaining colon for definitive pull-through, which would be more important, rather than the 8 cm length of colon. Based on these, the authors propose a modified version of Wakhlu's classification.

Table 11.2 Types of short colon

1.

Agenesis of colon

2.

Short colon without imperforate anus

3.

Short colon with imperforate anus (dilated colon)

4.

Short colon as a part of exstrophy of the bowel and bladder (small and narrow colon)

S.

Short colon due to abnormal vessels and the like

1. Incomplete CPC: where the length of the normal colon is adequate for performing the pull-through, without the need for doing a coloplasty. The procedure would involve excision of the pouch with an end colostomy at birth and a definitive pull-through later. A single-stage pull-through in the newborn stage can also be undertaken if the condition of the baby permits.

2. Complete CPC: where there is either absent or insufficient normal colon left to permit a pull-through procedure. In this situation, a coloplasty procedure would be required to retain only a 15-cm length of CPC in the form of a tube, to be brought out as an end colostomy. A pull-through procedure at the time of performing coloplasty should not be preferred in the newborn stage as it is associated with high morbidity and mortality.

According to the authors, the CPC should have the following anatomical criteria:

1. There is anorectal agenesis.

2. The total length of the colon is short (Fig. 11.2).

3. The colon has a pouch with varying length; saccu-lar or diverticular with a collection of meconium or fecal matter (Fig. 11.3).

4. The blood supply to the pouch is abnormal (Fig. 11.4).

5. The colon wall is thick and muscular with hyper-trophied mucosa (Fig. 11.5).

6. The fistula with the genitourinary tract is large, muscular, and long. It is closely adherent with the bladder wall.

7. There is no transitional zone between the pouch and the normal bowel. The pattern changes suddenly and sharply.

Associated genitourinary malformations (cloacal anomalies, double vagina, exstrophy) are common in girls; however, other (nongenitourinary) associated congenital anomalies are less common.

The anatomical features vary according to the length of the colon that exhibits pouching. In complete pouching of the colon, there is a large, dilated, thick-walled pouch occupying most of the left side of abdomen. The cecum, if present almost always opens into the sac from the right side. It may be associated with an absent, rudimentary, or double appendix. The ileum opens into the cecum or the pouch from right side and there is associated malrotation. The pouch has a poorly developed mesentery and is supplied by the superior mesenteric artery on the superior and right side and an arcuate extension of the superior mesenteric artery on the left side [21]. The inferior mesenteric artery is present only in incomplete CPC and supplies the lower half of left lateral side of pouch. The pouch lacks haustrations, taeniae, and appendices epiploicae. At times the inferior mesenteric artery may be completely absent.

The distal communication of the pouch is in most instances with genitourinary system. In males, the communication is most commonly present with the bladder and the fistula opens on the posterior wall of bladder near the base. Occasionally the fistula may open higher or lower down (Fig. 11.6). The fistula is usually quite broad and thick-walled, and measures up to 1 cm in external diameter. In females, colocloacal fistula is the most commonly occurring fistula, followed by colovaginal and colovestibular fistulae.

In cases of incomplete CPC, the cecum is situated in the epigastrium or the left hypochondrium and a variable length of normal colon is found, which ends in a large sac that communicates with the bladder in males and the vagina or vestibule in females. The ce-cum, appendix, and the normal part of the colon are vascularized by the superior mesenteric artery. The inferior mesenteric artery, if present, supplies part of the colonic pouch.

The pelvic musculature is variable in cases of CPC, and when associated with a complete pouch or low vertebral anomalies, the pelvic and perineal muscles are poorly developed.

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