CONGENITAL ANOMALIES OF LARGE BOWEL

CONGENITAL ANOMALIES OF LARGE BOWEL

A. Developmental obstructive defects: Atresia and stenosis of colon Hirschsprung disease Functional immaturity of the colonB. Anomalies of rotation and fixationC. Intestinal duplicationD. Anorectal anomalies

Atresia and stenosis of colon• Colonic atresia: condition in which a part of the

colon has failed to correctly form, and that part is either completely blocked or is altogether missing (complete obstruction).

• Is believed to be caused by an in utero vascular accident.

• Pts present with: Abdominal distention, failure to pass meconium, cannot pass gas and stool, colonic segment above the atresia becomes distended.

• Colonic stenosis: condition in which a part of the colon is very narrow (partial obstruction).

• Stenosis > atresia of colon.

• Colonic atresia is fatal if the obstruction is not relieved.

• Risk for dehydration, perforation, and sepsis.

• Investigations: (1) antenatal US: may reveal bowel loop distention or

polyhydramnios. (2) Plain abdomen x-ray: reveals bowel obstruction

and prominent dilated loop. (3) Contrast enema reveals narrowing of the colon,

with limited filling of the dilated proximal colon-colonic stenosis.

Contrast study of colonic atresia

Contrast enema revealing colonic stenosis at the hepatic flexure.

Treatments.Surgical Therapy• The management of colonic atresia is directed at

eliminating the bowel obstruction and establishing intestinal continuity.

• This may be performed in one operation by resecting the atretic ends and anastomosing the colon.

• In congenital colonic stenosis, one usually finds less difference in the sizes of the proximal and distal limbs, making resection with primary anastomosis the preferred treatment.

Hirschsprung’s disease

• Definition: absence of intramural ganglion cells (aganglionosis) in variable length of distal bowel.

• Failure of migration of vagal neural crest cells into wall of colon (5-7 weeks).

• Aganglionic segment remains contracted and normally innervated bowel are dilated.

• failure of relaxation of aganglionic segment→ prevents movement of intestinal contents→ Dilation.

• 1: 5000 newborn• m:f = 4:1• May be familial or associated with Down’s syndrome

or other genetic disorders.• Gene mutations have been identified on

chromosome 10 (RET proto-oncogene) and chromosome 13 in some pts.

• Clinical features:Delayed passage of meconiumAbdominal distensionBilious vomitingConstipation • Complication: Enterocolitis

Investigations.1. Plain abdominal

radiograph. -show distended bowel

loops with a paucity of air in the rectum.

2. Barium enema. -narrowed distal colon

with proximal dilation. -retention of barium

after 24 hours.

Investigations cont..

3. Rectal biopsy. -provide definitive diagnosis -findings that indicate an absence of ganglion

cells. -Disadvantages : may cause bleeding, scarring

and need of general anesthesia during full-thickness biopsy procedures.

Managements• Medical Care• The general goals of medical care : (1) to treat the complications of unrecognized

or untreated Hirschsprung disease (2) to institute temporary measures before

definitive reconstructive surgery (3) to manage bowel function after

reconstructive surgery.

Surgical care.• Aims to remove the aganglionic segment and bring

down healthy ganglionic bowel to the anus (“pull-through” operation)

• Can be done in single stage or several stages after first establishing a proximal stoma in normally innervated bowel.

• Most pts achieved good bowel control.• Minority experienced residual constipation and/or

faecal incontinence.

Surgical care cont..• The 3 most commonly performed repairs are: (1) Swenson procedure (2) Duhamel procedure (3) Soave procedures• Regardless of the pull-through procedure chosen,

cleaning the colon before definitive repair is necessary.

Functional immaturity of the colon• Common cause of neonatal obstruction, particularly

in: (1) premature neonates (2) those whose mothers were treated during labor

with magnesium preparations or high doses of opiates or other sedatives.

• Functional immaturity of the colon comprises several entities, most notably small left colon syndrome and meconium plug syndrome.

• Affected patients have: (1) abdominal distention (2) difficulty in initiating evacuation (3) sometimes vomiting (4) bowel distention (less severe) • The condition is both diagnosed and treated with a

contrast enema.• Clinical improvement following the enema, and over

the course of hours to days the radiographic and clinical signs of obstruction subside.

ANOMALIES OF ROTATION AND FIXATION

• Most important anomalies are: (1) nonrotation (2) malrotation (3) reversed rotation• Early diagnosis of these conditions is important to

prevent midgut volvulus and small bowel necrosis.• The symptoms of rotation anomalies are identical to

those of proximal bowel obstruction and may be accompanied by symptoms of vascular occlusion.

• The obstruction may be complete or partial.

• In the neonate, complete obstruction and vomiting is the most common presenting symptom within the first month of life (77% ) .

• In older children, the obstruction is usually partial and provokes recurrent attacks of vomiting and occasionally distention.

• An upper gastrointestinal series is usually performed initially to demonstrate the level and nature of the obstruction.

• Other investigations: US, CT, and MRI

Nonrotation: show the small intestine on the right side of the abdomen and the colon and cecum on the left side. The ileum is seen crossing the midline from right to left (arrows).

Malrotation: the intestine occupies an intermediate position between that of nonrotation and the normal postnatal position. The cecum and the terminal ileum are displaced upward and medially.

Midgut volvulus: demonstrates the “corkscrew” appearance of the proximal small bowel (arrows) as it twists around the superior mesenteric artery.

Treatments.Surgical Therapy• The treatment of malrotation and volvulus is surgical;

no other treatment is available.• A surgeon should be immediately consulted when

malrotation or volvulus is suspected.• The Ladd procedure remains the cornerstone of

surgical treatment for malrotation today.• A classic Ladd procedure: reduction of volvulus (if

present), division of mesenteric bands, placement of small bowel on the right and large bowel on the left of the abdomen, and appendectomy.