Type IV Congenital Pouch Colon in Male Children: Anatomical Variations and a Proposed New Subclassification.

BACKGROUND: Congenital pouch colon (CPC) is a rare variant of anorectal malformation. In male patients, CPC communicates distally with the urogenital tract by a large fistula. The CPC cases which do not fulfill the criteria as mentioned in the classical description are reported along with the pertinent literature review.
MATERIALS AND METHODS: This was a retrospective study from January 2004 to December 2017 of male children with Type IV CPC. We evaluated clinical presentation, primary management, anatomical relationship, previous surgical intervention, definitive management, result, and outcome in terms of continence status on Templeton score.
RESULTS: Fifty-one children were included in the study among whom 36 children (Group 1) had a colovesical fistula and 15 children (Group 2) had no communication of the pouch with the genitourinary tract. In Group 2 children, the clinical presentations and management were varied: 4 underwent primary pull-through procedure, whereas 11 underwent staged procedure. Group 2 included three children in whom a narrow and thin-walled anal canal or anal canal with lower rectum was present, which was incorporated during the pull-through procedure. On continence assessment, only one child in Group 1 had "good" continence score compared to four children (three having anal canal) in Group 2.
CONCLUSION: CPC Type IV can present without genitourinary tract communication (fistula), contrary to its emblematic description. Awareness about anatomical variations and adaptation of surgical technique accordingly is vital. The identification of the anal canal with or without the lower part of the rectum (even though apparently narrow and thin walled) and incorporation of this in bowel continuity lead to better outcomes in terms of continence. Copyright:

INTRODUCTION

Congenital pouch colon (CPC) is an anomaly in which a pouch-like dilatation of a shortened colon is associated with an anorectal malformation (ARM). The most widely used classification of CPC described by Narasimha Rao et al. categorizes CPC into four subtypes (Types I–IV) based on the length of the normal colon proximal to the colonic pouch.[1] Type V also has been described in the literature.[23] Type I is the most severe form and Type IV is the least. In males, the pouch usually terminates in a colovesical fistula just proximal to the bladder neck.[14] CPC has been included, as a rare variant, in the Krickenbeck classification of ARM. A recent review showed that about 90% of reported cases in the world were from India.[5] According to Gupta and Sharma, CPC should have some anatomical criteria: (1) there is anorectal agenesis, (2) total length of the colon is short, (3) colon has a pouch formation for a varying length – saccular or diverticular with the collection of meconium or fecal matter, (4) the blood supply to the pouch is abnormal, (5) the colon wall is thick and muscular with hypertrophied mucosa, (6) the fistula with the genitourinary tract is large, muscular, and long and it is closely adherent with the bladder wall, and (7) there is no transitional zone between the pouch colon and the normal bowel. The pattern changes suddenly and sharply.[5] In this study, we are discussing Type IV CPC cases which do not fulfill all the above-mentioned criteria.

MATERIALS AND METHODS

This was a retrospective study from January 2004 to December 2017, conducted at a tertiary care center. Data were collected from previous records maintained by us. Ethical clearance was obtained from the institutional review board (IEC/2018/000831). We included all male patients with CPC Type IV, irrespective of their age at presentation, any operative intervention before presenting to our center, and also children who were still awaiting a definitive procedure. All other types of male ARM including CPC Types I, II, and III as well as female patients with ARM were excluded as well as children with incomplete data and children/parents who refused to participate in the study.

All children routinely underwent two-dimensional echo and ultrasonography of the kidney, ureter, and bladder. Other investigations were guided by clinical examination findings. Wherever feasible, either a contrast enema or distal cologram was performed before the definitive procedure [Figure 1a]. Our routine protocol for children with CPC presenting in the newborn period with an absent anal opening and abdominal distension is pouch excision, fistula ligation, and end colostomy at the first stage and later on abdominoperineal pull through (APPT) at 9 months–1 year of age. In all cases (except where pouch excision was already done at another hospital), the excised pouch was sent for histopathological examination. We evaluated clinical presentation, primary management, anatomical configuration, previous surgical intervention, definitive management, result, and outcome in terms of continence status. Continence assessment was done according to the Templeton score questionnaire.[6] Only those children/parents were interviewed where the child was at least 6 months after completion of all stages of surgery and was above 3 years of age.

Figure 1

(a) Barium enema study of a child presenting with constipation postanoplasty for low anorectal malformation. Black arrow is showing sharp cutoff of narrow and dilated area. (b) Intraoperative images of pouch colon. Black arrow is showing abrupt change of caliber without transition zone. White arrow is showing abnormal vasculature

Data were analyzed using the software, Statistical Package for the Social Sciences (SPSS) for Windows (IBM SPSS Statistics for windows, version 22.0. Armonk, NY, USA). The difference between the occurrence of associated malformations in both the groups and also the difference between the outcomes (continence scores) in different groups were compared by Pearson's Chi-squared test. P < 0.05 was considered statistically significant.

RESULTS

A total of 51 male children of Type IV CPC were included for the analysis with 36 (Group 1) having colovesical fistula and 15 (Group 2) without any genitourinary communication. A total of 27 associated anomalies were present [Table 1]. In Group 1, all patients initially underwent end colostomy and fistula ligation. One child died after initial colostomy due to septicemia. Of the remaining, 31 have undergone APPT and 4 are awaiting APPT. In Group 2 patients, the clinical presentations and management were varied [Tables 2 and 3]. Among the staged procedures in Group 2, in three children, the anal canal was present. This was subsequently incorporated in bowel continuity: in two, the upper sigmoid was anastomosed to the anal canal, and in one, the descending colon was anastomosed to the lower rectum. All children were operated by either of two surgeons (KLNR/PM). In all cases, histopathology of excised pouch confirmed the diagnosis with certain distinguishing pathological findings, i.e., acute and chronic inflammation of the mucosa and submucosa, focal or generalized thinning of muscle layers, especially of the outer muscle coat, disorganized and disrupted muscle layers, decreased number of mature ganglion cells, neuronal hyperplasia, and hypertrophy in nerve plexuses.

Table 1

Associated malformations in the study group

Anomalies	Group 1 (n=36)	Group 2 (n=15)
Genitourinary
VUR	6	1
Crossed fused ectopia		1
UDT	1	1
UPJO		1
Hypospadias	3
Solitary kidney	3
Ectopic kidney	1
Microphallus	1
Gastrointestinal
Meckel’s diverticulum	1	1
TEF	1
Skeletal
Polydactyly	1
CTEV	2
Vertebral anomaly	1
Others
Presacral teratoma		1
Total	21	6
P	>0.05

VUR: Vesicoureteral reflux, UDT: Undescended testis, UPJO: Ureteropelvic junction obstruction, TEF: Tracheoesophageal fistula, CTEV: Congenital talipes equinovarus

Table 2

Clinical presentation of Type IV congenital pouch colon without genitourinary communication

Age	Anorectal anomaly	Chief complaint	Previous surgical intervention
2 days	AAO	AD	Nil
2 days	AAO	AD	Nil
2 days	AAO	AD	Nil
2 days	AAO	AD	Nil
4 days	AAO	AD	Nil
7 days	AS	AD	Nil
7 days	AS with dysplastic rectum	AD	Nil
9 days	AAO	AD	Nil
15 days	Perineal fistula	AD	Nil
7 months	AS with dysplastic rectum	Referred for definitive procedure	Pouch excision with end stoma
10 months	AS	CC	Nil
1 year	AS	Referred for definitive procedure	1. Anoplasty2. Loop sigmoid colostomy
2 years	AS	CC	Nil
3 years	AS	CC	Anoplasty
4 years	AS	CC	Anoplasty

AAO: Absent anal opening, AD: Abdominal distension, AS: Anal stenosis, CC: Chronic constipation

Table 3

Surgical interventions done in Group 2 children

Procedure types	First procedure	Second procedure	Number of patients
SS	Pouch excision and APPT	-	4
TS	Pouch excision and end colostomy	APPT	7
TS	Divided sigmoid colostomy	Pouch excision and APPT	1
TS	Divided sigmoid colostomy	Pouch excision and colon to anal canal anastomosis	1
TS	Pouch excision and end colostomy	Colon to anal canal anastomosis	1
TS	Anoplasty	Pouch excision and colon to lower rectum anastomosis	1

SS: Single stage, TS: Two stage, APPT: Abdominoperineal pull through

The mean follow-up duration was 68.2 months (range: 3 months–14 years) and 35.8 months (range: 6 months–8 years) for Group 1 and Group 2, respectively. In the entire study group, 41 patients had increased frequency of stool, whereas 5 children had constipation.

To assess continence status, 34 children were eligible for interview. The remaining were either awaiting definitive surgery (n = 4) or could not be contacted (n = 6), or age was <3 years (n = 6). Continence was significantly better in Group 2, especially in those with anal canal preservation [Table 4].

Table 4

Distribution of children according to the Templeton score of continence

Group (number of children)	Good (%)	Fair (%)	Poor (%)
Group 1 (20)	1 (5)	9 (45)	10 (50)
Group 2 (14)	4* (28)	3 (22)	7 (50)
P	P<0.00001

*3 children with anal canal preservation during definitive procedure

DISCUSSION

During the preliminary descriptions of CPC, there was a difference of opinion regarding the existence of this entity. At present, it is now a well-established diagnosis with certain anatomical features with various classifications. Rao's Type I CPC was the most common form reported in the literature previously, but gradually, Type IV has become more common. It may be because of the decreased severity of pouch colon or because of proper identification of Type IV cases which were missed out previously.[578] In this type, rectum or rectosigmoid is converted into a pouch and rest of proximal intestine is normal.[1] In most descriptions, CPC in male children presented with absent anal opening and had communication with the genitourinary tract.[45] In our study also, while the most common presentation was similar to that described in the literature, i.e., absent anal opening and colovesical communication, 15 children presented in a different manner, and consequently, the management was also different.

For better understanding and proper comparison, we propose that Type IV CPC should be subclassified as mentioned in Figure 2. We stress on the presence of anal canal and its location within a normally placed sphincter muscle complex, with resulting beneficial effect on continence. The anal canal in these patients seems narrow and thin walled. On careful examination, the dentate line can be seen. The anal opening in these patients is located at the normal place but is very small. The external appearance is variable, and the anus may be pulled up or protruding outside with a whorled appearance of the surrounding skin [Figure 3a].

Figure 2

Proposed subclassification of Type IV pouch colon

Figure 3

Operative images of sigmoid to anal canal anastomosis. (a) Preoperative image is showing anal stenosis. Note the whorled appearance of the narrow anal opening. (b) The anal opening is widened and the sigmoid everted for anastomosis to anal canal. (c) Completed anastomosis and reposition of bowel inside the anal opening

Urogenital malformations (undescended testis, vesicoureteral reflux, renal agenesis, etc.) have been previously reported as the most common associated anomalies with CPC.[91011] However, in spite of the high supralevator nature of CPC, major associated malformations are not common. A review of 566 cases showed hydronephrosis and hydroureteronephrosis in 7% and 28.2%, respectively, vesicoureteral reflux in 6.36%, and renal agenesis in 1.4%.[5] In our study also, urogenital malformations were most commonly associated. Associated anomalies were common in Group 1 (58.3%) compared to Group 2 (40%) although not statistically significant.

In our study, three children had initially presented with constipation after an anoplasty despite an adequate anal opening. On subsequent contrast enema, CPC Type IV was diagnosed. Pavai et al. also reported a similar experience wherein two male children presenting with constipation after anoplasty for low ARM were found to have a Type IV CPC on further evaluation.[9] We want to emphasize the point that when children with low ARM do not improve after anoplasty (in spite of an adequate anal opening), we should reconsider the diagnosis and perform a contrast enema to delineate the anatomy.

A review of the literature shows the use of single stage as well as staged procedures in the management of Type IV CPC.[1213] While both have advantages and disadvantages, we prefer an individualized approach. In a stable child with well-defined anatomy, we preferred to do a one-stage procedure. In acute presentation and poor general condition, staged procedure should always be considered. The ability to prepare the bowel properly before a single-stage pull through should also be considered as it is difficult to clear a loaded colon in the presence of anal stenosis. Intraoperatively, it is important to differentiate between pouch colon and bowel dilatation due to distal obstruction, CPC being identified by the sharp cutoff between normal bowel and pouch (no transition zone), abnormal vascularity, and thickened wall [Figure 1b].[5] This can be confirmed later by biopsy of resected segment as histopathological criteria are also well defined.[1415]

In our study, a total of eight children had a dysplastic anal canal, i.e., narrow and thin walled. However, only in three children, the anal canal could be incorporated in bowel continuity during APPT [Figure 3]. In these three children, postoperative continence status was superior [Table 4]. They presented with constipation (like low ARM patients) during initial follow–up while most of the other children had stool frequency (like HARM patients) and soiling during follow-up. These three children had normal bowel continence and were completely asymptomatic at the last follow-up. In our view, this adaptation of surgical technique according to the peculiar anatomy led to better functional results. The presence of anal canal signifies well-formed sphincter complex with intact sensory-motor pathways. Therefore, we recommend to preserve the native distal most bowel and incorporate it into bowel continuity even though it may appear apparently very narrow and thin.

CONCLUSION

CPC Type IV can present without genitourinary tract communication (fistula), contrary to its emblematic description. Awareness about anatomical variations and adaptation of surgical technique accordingly is vital. The identification of the anal canal with or without the lower part of the rectum (even though apparently narrow and thin walled) and incorporation of this in bowel continuity lead to better outcomes in terms of continence.

Informed consent

Patients' consent was obtained for the surgery. It was a retrospective study. Data were collected from the old records. Permission was obtained from the Institute Ethical Board for “Waiver for consent of the patients to participate in the study” (IEC/2018/000831).

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for 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.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.