Colonic atresia is a condition in which a part of the colon has not formed correctly, with the result that it is either blocked completely or missing altogether; colonic stenosis is a condition in which a part of the colon is very narrow, resulting in a partial blockage. Other obstructions of the colon that affect newborns include the following:
Although these conditions are all forms of colonic obstruction, they are different from atresia and stenosis and thus are more completely reviewed elsewhere.
The colon is the rarest site of atresia in the gastrointestinal (GI) tract. It is a congenital anomaly that may be suggested by prenatal sonograms and is usually revealed in affected newborns shortly after birth. Patients usually present with abdominal distention and failure to pass meconium.
Stenosis of the colon is much more common. Patients usually present later in life, most often because of an identifiable event. In congenital stenosis, a narrow segment of colon is observed, but bowel continuity is maintained. A discrepancy between the colonic segments above and below the area of stenosis is present. In acquired stenosis (commonly referred to as stricture), what starts as a normal segment becomes narrowed. This is most common in premature babies who have recovered from an episode of necrotizing enterocolitis.
Colonic atresia and congenital stenosis are uncommon lesions. Infants present with abdominal distention and vomiting and often fail to pass meconium. Associated anomalies are common, and their severity directly affects outcome. Although the etiology of colonic atresia has traditionally been believed to be related to antenatal mesenteric vascular accidents, a 2005 study suggests that defects in the fibroblast growth factor 10 (FGF10) pathway may be involved. 
The combination of Hirschsprung disease and colonic atresia remains rare; however, missing the association before reconnecting the intestinal tract can lead to repeat operations, poor outcome, and increased mortality.
Surgical correction is the mainstay of therapy for atresia and stenosis. In the absence of significant comorbidity, primary resection and anastomosis constitute the recommended surgical treatment and appear to have an outcome equivalent to that of resection with creation of a colostomy and subsequent closure.
The colon arises from the digestive tube, which is present by the end of the first month of gestation. Rapid elongation begins at 5 weeks’ gestation. Over the ensuing 5 weeks, the intestinal tube, separable into cephalad and caudal limbs (on the basis of their relation to the omphalomesenteric duct), rotates counterclockwise and returns to its familiar position in the abdomen. The proximal caudal limb is supplied by the superior mesenteric artery (SMA), whereas the distal portion is supplied by the inferior mesenteric artery (IMA). 
The SMA gives rise to the ileocolic, right colic, and middle colic arteries, which supply the ileocecal region, the ascending colon, and the proximal transverse colon, respectively. The left colic artery, arising from the IMA, supplies the left portion of the transverse colon and the descending colon. The middle colic and left colic arteries join near the splenic flexure to form the marginal artery. The sigmoid arteries, rectosigmoid arteries, and branches of the IMA supply the sigmoid colon.
Pathophysiology and Etiology
The feature common to both atresia and stenosis is intestinal blockage, either partial or complete.
In colonic atresia, the problem is complete bowel obstruction. Gas and stool cannot pass, and the colonic segment above the atresia becomes distended. If left untreated, this leads to perforation.
In colonic stenosis, the problem is that gas and stool try to pass through a narrow area. While the baby is passing soft baby stools, this may or may not be noticeable. When the baby’s diet changes from breast milk or formula to cereals and solid foods, the stool can become thicker and more formed. This may cause stenosis to become symptomatic, leading to distension, feeding intolerance, or failure to thrive.
In babies who have had necrotizing enterocolitis, stenosis occurs after the original episode has resolved. This may manifest in varying degrees, ranging from minor feeding intolerance and distension to near-complete bowel obstruction.
Small bowel and colonic atresias are not believed to occur by the same process as duodenal atresia, which is suspected to be due to failure of vacuolization of the duodenum and was described by Tandler in 1900.
In 1955, Louw and Barnard hypothesized that small bowel atresias are caused by prenatal vascular interruption.  The same mechanism is believed to cause colonic atresia. Thrombosis, volvulus, and herniation with strangulation are all mechanisms that may cause in utero vascular injury and bowel necrosis with subsequent reabsorption. Fairbanks proposed a relationship between fibroblast growth factor 10 (FGF10) expression, vascular development, and colonic atresia. 
Colonic atresia is typically classified according to the 1989 descriptions of intestinal atresia by Bland-Sutton and the 1964 descriptions by Louw. [5, 6] In type 1 colonic atresia, the bowel and mesentery remain intact, but the bowel lumen is interrupted by a complete membrane (see the image below).
In type 2 colonic atresia, the bowel is discontinuous, with portions connected by a fibrous cord. In type 3 colonic atresia, the bowel ends are completely separated, and the mesentery has a gap. Stenotic lesions are characterized by intact bowel with incomplete occlusion and require no classification.
In 1990, Davenport et al reviewed 118 cases of colonic atresia and reported the following distribution lesion sites  :
Ascending colon - 33 (28%)
Hepatic flexure - 4 (3%)
Transverse colon - 27 (23%)
Splenic flexure - 30 (25%)
Descending and sigmoid colon - 24 (20%)
Two thirds of colonic atresias are in the distribution of the inferior mesenteric artery (IMA). This finding may be related to a lack of collateral blood supply or to disease processes that render this portion of the colon more susceptible to injury.
Although the colon is supplied by the superior mesenteric artery (SMA) and the IMA, there is considerable variation among smaller named arterial branches. The parts of the colon most vulnerable to ischemia appear to be the splenic flexure and the ileocecal area—coincidentally, the areas farthest from the major trunks. However, atresia and stenosis occur throughout the colon; the variation in terminal branches, coupled with the complex rotation and fixation of the bowel, may create regions of ischemic injury in utero that result in atresia or stenosis. 
Any process leading to occlusion of branches of these vessels in utero may result in atresia. Compression at the umbilical ring,  internal hernia, intussusception,  choledochal cyst,  volvulus, and thrombosis all may initiate bowel infarction, leading to disintegration, reabsorption of dead tissue, and sealing of bowel ends.  Bowel content is sterile; thus, sepsis does not occur. Meconium is produced throughout the gut during the third trimester; thus, a newborn whose atresia occurs after that time may still pass meconium in the neonatal period.
Prenatal maternal use of vasoconstrictive medications (eg, cocaine, amphetamines, nicotine, or decongestants) has been suggested as a risk factor for intestinal atresia formation. 
Although prenatal mesenteric vascular accident has been long accepted as the most likely cause of colonic atresia, a study on the role of the FGF10 signaling pathway has brought that belief into question. In this study, mice that were unable to express FGF10 and FGF receptor 2b developed colonic atresia, even though their mesenteric vasculature was normal during periods when atresias were developing; this suggests that the etiology of colonic atresia may be more complicated than was once thought and that it may not involve a vascular issue. 
Congenital stenosis occurs when the bowel injury is incomplete, as may be the case when injury occurs close to the bowel wall, allowing collateral blood flow to preserve the injured tissue. Another mechanism is limited ischemia, in which the blood supply is partially or intermittently occluded, resulting in incomplete intestinal injury.
Acquired stenosis is more common than atresia or congenital stenosis. Via the same mechanism of vascular compromise, the injured bowel undergoes healing and scarring with narrowing of the affected intestine. Intense inflammatory reactions, such as those that occur in necrotizing enterocolitis and Crohn disease, may result in stricture. Tuberculosis-associated left colon stricture has also been reported. 
Patients who undergo bowel resection for any reason and have a segment of intestine removed and joined by anastomosis may develop stricture at the anastomotic site as a consequence of ischemia or a technical issue. Surgery is usually required to revise the joined loops.
Colonic atresia is very rare, with reported incidences ranging from 1 in 1500 live births  to 1 in 66,000.  Webb (1931) and Benson (1968) cited an incidence of 1 in 20,000, which most closely reflects experiences in the modern era. [15, 16] In 1982, Powell suggested that colonic atresia represents 5-15% of intestinal atresias,  whereas in 1966, Freeman reported a figure of 1.8%.  In 1953, Gross reported that colonic atresia represented 4.3% (6/140) of cases of intestinal atresia at the Boston Children’s Hospital. 
Multiple atresias are uncommon in the colon; however, colonic atresia may be overlooked when small intestinal atresia is present.  Rare cases of familial colonic atresia have been described. Animal studies have shown an autosomal recessive pattern of inheritance in cattle. Hereditary multiple intestinal atresia affects both the large and the small intestine, whereas nonhereditary multiple intestinal atresia usually spares the colon. 
The incidence of colonic stenosis is not readily available, because most cases are acquired. In 1953, Gross reported only 1 colonic lesion in 71 patients with intestinal stenosis.  Necrotizing enterocolitis is the most common etiology of postnatal colonic stenosis; narrowing develops in 10-25% of affected patients. [22, 23, 24]
Patients with colonic atresia or congenital stenosis may sometimes have characteristic findings on prenatal ultrasonography, such as dilated bowel loops or the presence of polyhydramnios. Initial physical examination findings are normal in the absence of associated conditions. The anus usually appears normal. Progressive abdominal distention develops. Rectal examination reveals white or pale mucus rather than pigmented meconium.
Failure to pass meconium completely suggests atresia, whereas delayed passage of meconium (>24 hours) suggests Hirschsprung disease. Patients with colonic atresia may pass meconium normally because the incident that caused the atresia may have occurred after the colon had become filled with meconium.
Colonic stenosis usually follows some form of injury to the colon, sustained either in utero or postnatally, and ischemia is considered central to the insult. The infant or child may present with symptoms similar to atresia with high-grade stenosis; less stenotic lesions may not become apparent until feeding is undertaken. In those instances, the child’s abdomen may become distended with feeding, and stool production is scant, if present.
Babies with necrotizing enterocolitis may show signs of acquired stenosis after their acute episode. When the septic signs of the illness resolve and the child is doing well, feeding is often attempted. If a stenosis has formed, the baby usually will not tolerate feedings, and the abdomen will become distended. Studies may be performed to confirm the diagnosis and to try to localize the site of narrowing, at the discretion of the surgeon.
Plain radiography of the abdomen reveals bowel obstruction and may reveal a prominent dilated loop (see the image below). A prone view shows absence of gas in the rectum, though gas may be present if the film was obtained after the rectum was examined. Radiography in congenital colonic stenosis also reveals an obstructive pattern that may mimic atresia.
Contrast enema may be performed before operative treatment, at the discretion of the surgeon, and can be useful in ruling out the presence of other lesions downstream from the atresia. It reveals a microcolon with a rounded proximal end (see the first image below). In congenital colonic stenosis, contrast enema reveals narrowing of the colon, with limited filling of the dilated proximal colon (see the second image below)
Antenatal ultrasonography may reveal bowel loop distention or polyhydramnios.
In all children with neonatal bowel obstruction, an electrolyte measurement, a complete blood count (CBC), and a crossmatch should be obtained before operative intervention is initiated.
Rectal biopsy (performed either as a suction biopsy before surgical correction or at the time of operative correction) should be considered to evaluate for associated Hirschsprung disease. [25, 26] The association is quite rare; in a series of 12 patients, none were found to have Hirschsprung disease. 
Treatment & Management
Like all other intestinal atresias, colonic atresia is fatal if the obstruction is not relieved. A baby with colonic atresia is at risk for dehydration, perforation, and sepsis. Any intestinal atresia requires operative intervention to prevent these complications.
The specific operative indication in colonic atresia is complete bowel obstruction. Once a newborn is identified as having bowel obstruction, no additional information is required to prove the need for surgery. Other studies may be done before the operation, but no studies are necessary to confirm the need for surgery.
When colonic stenosis is very tight, it behaves like colonic atresia. In less severe cases, the child may have chronic problems such as bloating with feeds, cramping, or poor weight gain. Any of these symptoms may be significant enough to warrant either radiologic investigations or operative exploration and repair.
Intestinal obstruction at any level necessitates surgical relief. The timing of surgery in colonic atresia and stenosis depends on the patient’s clinical condition and any associated malformations and comorbidities.
The decision to proceed with primary correction (resection with anastomosis) or stoma diversion depends on the same factors, as well as on the skill and experience of the surgeon and the surgical team. Although no contraindications to surgery are recognized, stoma diversion is the minimum intervention necessary to relieve the obstruction. Severe underlying illness and associated life-threatening malformations may be considered relative contraindications to immediate primary repair.
Initial resuscitation and support
Initial treatment of newborns with colonic atresia is directed toward resuscitation. The child often has a distended abdomen and is dehydrated. Usual treatments carried out before operative intervention include the following:
Intravenous (IV) fluid resuscitation
IV antibiotic therapy – This is usually administered to all patients, though the indications are not clearly evidence based; because during the first 3 days of life the intestinal flora is not yet colonized with anaerobes, gram-positive and gram-negative coverage is sufficient at that time
After the prompt initiation of these basic measures, the child should be transferred to a neonatal intensive care unit (NICU) at a center with pediatric surgeons capable of correcting the malformation. Associated abnormalities of other organ systems may require attention and treatment.
Surgical management of colonic atresia is directed at eliminating the bowel obstruction and establishing intestinal continuity. In selected patients (ie, those with limited comorbidities and limited associated malformations), these goals may be achieved in a single operation by resecting the atretic ends and anastomosing the colon. If the child has significant comorbidities, a diverting enterostomy may be brought out just proximal to the atresia, and intestinal continuity may be restored during a second operation.
Choice of procedure
Some authors have advocated resection with primary anastomosis for right colon lesions and colostomy diversion with subsequent reconstruction for left-side disease. In theory, the liquid feces in the right colon pose less of a risk to a fresh anastomosis than formed stool would. However, a 1990 study found that survival rates were unaffected by the type of procedure and that outcomes were excellent with either.  A 2009 series reported excellent outcomes for primary anastomosis in 10 of 12 patients, two of whom had gastroschisis. 
Colonic atresia associated with Hirschsprung disease can be associated with abnormal distal colonic fixation. [28, 26] The association of nonfixation with aganglionosis seems significant enough to warrant obtaining biopsy results before establishing intestinal continuity in those selected cases.
Diverting enterostomy alone is always a safe option if the suspicion of aganglionosis is significant and experienced pediatric pathology services are unavailable. Because of the rarity of this association, it may be reasonable to reserve biopsy for patients with intestinal fixation abnormalities, postoperative feeding or elimination difficulties, or failure to thrive.
The question of the necessity for routine rectal biopsy before the establishment of intestinal continuity is not so much controversial as it is difficult to answer definitively. The small number of cases that associate Hirschsprung disease with colonic atresia is such that the association is greater than random but still exceedingly rare.
The downside to taking a staged approach if Hirschsprung disease is a possibility is minimal in comparison with the risk of multiple operations and increased mortality when the association is missed before the anastomosis. Knowing both sides of this issue allows the surgeon to choose the approach that best serves their patient.
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. In acquired colonic stenosis following necrotizing enterocolitis, primary excision and anastomosis is the treatment of choice for stable patients without life-threatening comorbidities.
Hamzaoui et al reported using a transanal approach, similar to the transanal technique for Hirschsprung disease, after exploratory laparotomy with colostomy at birth in two patients with rectal and low sigmoid atresia (operated on at 6 and 3 months of age, respectively).  No intraoperative or postoperative complications were noted at 2-year follow-up, and neither patient had fecal incontinence after closure of the colostomy.
Basic preoperative laboratory measurements for all neonates should include a complete blood count (CBC), electrolyte assessment, and a crossmatch. If time permits, a contrast enema can be quite useful for assessing the colon and excluding any other narrowing, which can be difficult to accomplish during surgery.
All children who undergo laparotomy need adequate analgesia. Narcotics should be administered to babies only in a monitored setting (ie, a NICU with apnea, pulse oximetry, and cardiac monitors). No baby should be prevented from receiving adequate analgesia simply because he or she cannot articulate the need for it.
A transverse supraumbilical laparotomy is usually performed. The abdomen is eviscerated, and the bowel is inspected. The atresia should be readily identified by the dilated bulbous proximal portion with a microcolon on the other side (see the images below). A large mesenteric or intestinal gap may be observed between the proximal and distal ends, reflecting the region that would have been supplied by the vessel that sustained the prenatal vascular accident (the hypothetical cause of the atresia).
The abdomen is then fully explored. The full intestinal length is examined for the presence of other atresias. This may require passing a catheter distally into the open end of the distal segment and distending the bowel with saline to ensure that the lumen is patent. The presence of multiple atresias may necessitate multiple resections; to minimize intestinal loss and the number of anastomoses, these atresias should be assessed collectively.
The dilated proximal portion of the colon is then resected. As a consequence of dysmotility, the dilated proximal bowel functions poorly. Resecting the proximal intestine back to an area of normal caliber is essential for postoperative function and, by lessening the size discrepancy between the two portions of the bowel to be joined, facilitates the creation of the anastomosis.
Only a minimal amount of distal bowel is removed. However, the atretic end is thickened and should not be used in closure; accordingly, that end is resected. The distal colon is usually divided on a bias, with more bowel removed on the antimesenteric side than on the mesenteric side (to promote better blood supply at the anastomosis). The antimesenteric side is usually opened further to counter the size discrepancy with the proximal end.
If a mesenteric gap is present, it is usually closed primarily, if possible.
Diversion with primary repair at second stage
In this operation, reconstruction is accomplished in much the same manner as in a primary repair (see above).
As in a primary repair, the proximal intestine is resected back to an area where bowel caliber is normal. This end is then brought out onto the anterior abdominal wall and matured as an ostomy.
If the patient is critically ill, the distal segment may be left completely undisturbed until the patient’s status changes in the future. If the patient is stable, the end of the distal is removed, and the fresh end is brought up to the abdominal wall skin as a mucous fistula.
Both ostomies can be brought out at the same location, either through the corner of the laparotomy or through a separate incision; they may also be separated by a skin bridge. Location, however, is nonessential. What is most important is that the colostomy be matured and positioned on the abdominal wall in such a way that an appliance can be securely placed around it.
The mucous fistula should not be matured like a mushroom; rather, it should be flush with the skin and only large enough to admit a catheter for irrigation or contrast radiography. If it is placed immediately next to the colostomy with no skin bridge, it should be small enough to allow appliance placement over both. If a skin bridge between ostomy and mucous fistula is preferred, it should be either small enough to be directly covered by the ostomy appliance wafer or far enough away not to interfere with ostomy appliance placement.
Neonates who have undergone surgical correction of atresia or stenosis require neonatal critical care in conjunction with the pediatric surgical care.
In the early postoperative period, the intestine and soft tissues absorb fluid, which surgeons refer to as third-space losses. These losses necessitate rehydration to ensure the maintenance of intravascular volume and adequate tissue perfusion. Inadequate hydration can lead to pressor administration, which can impair intestinal perfusion. Third-space losses usually persist for 24-48 hours if no source of sepsis is present.
Patients who have undergone a colostomy require specific care for the stoma and its output. Bowel function usually returns more quickly in these patients than in those who undergo resection and anastomosis. Colostomy closure is performed electively at a future date. Most surgeons prefer to wait a minimum of 6-8 weeks to allow intraperitoneal inflammation to subside.
Surgical treatment of colonic atresia and stenosis is associated with essentially the same complications as any operation involving bowel resection with stoma creation or anastomosis. Surgical site infection or incisional hernia can occur after any surgery.
The complication surgeons are most concerned about is anastomotic leakage. Leaks may manifest at any time but usually become noticeable several days to a week after surgery. Signs may be as subtle as mild tachycardia and fever or as obvious as rapid progression from mild illness to full-blown septic shock. Radiography may reveal intra-abdominal free air. Computed tomography (CT) may reveal abscesses. Anastomotic leakage calls for exploration and diverting enterostomy.
Intra-abdominal abscesses may occur without leakage but are rare. Intraoperative bleeding that leads to postoperative clotting can set the stage for abscess, which may be amenable to drainage by means of interventional radiology.
Anastomotic narrowing may occur and may be related to technical error, ischemia, or leakage. Patients who undergo colostomy may have stoma narrowing, prolapse, or parastomal herniation.
Early parenteral nutrition is appropriate for in all patients. Patients with atresia, despite having their bulbous dysmotile proximal portions resected, can have prolonged postoperative ileus and usually benefit from early parenteral nutrition.
If a nasogastric tube was placed during the operation, it usually remains in place, at the discretion of the surgeon. The most traditional approach is to keep a nasogastric tube to suction (taking care to replace its output with IV fluids) until the child is passing flatus or stool. When that occurs, the tube may be placed to bedside gravity drainage; if that is well tolerated, the tube may be removed. Some surgeons clamp the tube before removal as a final test to see if the child can truly tolerate his or her own intestinal gases and secretions.
When the tube is removed, the oral diet may be started. Most surgeons start with a clear liquid, such as sugar water or a balanced electrolyte solution. When that is well tolerated, the diet is advanced to either breast milk or formula.
Follow-up imaging studies are not performed unless indicated by clinical issues. Children who have had a stoma created usually undergo a contrast enema before stomal closure so that the distal limb can be evaluated for stricture or obstruction.
Follow-up in the office is essential. Many of these babies have residual intestinal motility problems that may manifest in either the proximal or the distal segment. Close follow-up is essential to ensure that they are appropriately managed. Failure to thrive or long-standing intestinal motility issues may be a sign of missed Hirschsprung disease and should prompt a biopsy. 
Whereas older series reported a high mortality for colonic atresia, modern series report survival of all patients, except those with significant life-threatening comorbidities. Patients with Hirschsprung disease and colonic atresia have more complicated courses and a mortality of 10%. 
Colonic stenosis outcomes have also improved significantly since Gross reported the death of the single patient treated at the Boston Children’s Hospital before 1952 (see Table 1 below).  Improvements in resuscitation and perioperative care have resulted in current survival rates of approximately 90%. [32, 33]
Table. Outcomes of Surgery in Colonic Atresia and Stenosis (Open Table in a new window)
|Author (Year)||No. of Patients||Procedure||Survival Rate|
|Gross (1952) ||6||Ostomy*||33%|
|Sturim (1966) ||2||Ostomy||50%|
|Coran (1969) ||9||Ostomy||66%|
|Pohlson (1988) ||11||Ostomy (6), anastomosis (4),† resection of diaphragm (1)‡||73%|
|Smith (1989) ||2||Not specified||100%|
|Davenport (1990) ||11||Ostomy (6), anastomosis (4)||91%|
|Barrack (1993) ||2||Anastomosis||100%|
|Dalla Vecchia (1998) ||21||Ostomy (18), anastomosis (3)||100%|
|Abu-Judeh (2001) ||1||Anastomosis||100%|
|Dassinger (2009) ||12||Ostomy (2), anastomosis (10)||100%|
*Ostomy, resection and staged anastomosis months later.
†Resection with primary anastomosis.
‡Cecotomy, resection of diaphragm.
Colonic atresia has been associated with abdominal wall defects and abnormalities of the genitourinary tract.  Nonfixation of the colon has been reported.  Association with anal atresia  and imperforate anus  has been reported but is extremely rare.
Colonic perforation may occur.  This is thought to be caused by overdistention of a closed colonic loop, with gas and stool trapped between a competent ileocecal valve proximally and the blind-ending colon distally. In 1988, Pohlson et al reported perforation of the terminal ileum in one case, clearly demonstrating that perforation can occur anywhere proximal to the obstructed bowel. 
Hirschsprung disease has been present in a small number of cases. [44, 30, 45, 46, 47] Additional anomalies associated with this pairing include omphalocele  and absence of a hand.  In most cases, the aganglionosis is discovered after colostomy closure when the distal bowel does not function properly.
Some authors have recommended that rectal biopsy be performed at the time of laparotomy,  whereas others believe that it should be reserved for children who do not pass stool readily when bowel continuity is restored after resection. [30, 46] Because colonic atresia is rare and because significant morbidity and mortality may result if the diagnosis is not made before intestinal continuity is established, it would seem prudent to perform rectal biopsy before committing to definitive repair. 
Cardiac conditions that require catheterization may predispose a baby to a mesenteric vascular incident resulting in colonic stenosis. Additional conditions reported in patients with colonic stenosis include the following [14, 17, 51] :
Cryptophthalmia syndrome (ie, cleft lip and palate, microphthalmia, dysplastic kidneys, and proximal jejunal atresia)
Proximal intestinal atresia
Riley-Day syndrome (ie, familial dysautonomia) has been associated with spontaneous colon ischemia.  Coloboma, cataracts and facial hemihypertrophy, facial asymmetry with palsy, microphthalmia with partial iridic coloboma, exophthalmia, and bilateral optic nerve hypoplasia all have been reported. [17, 53] In 2000, Kim et al described a case of colonic atresia in monozygotic twins.