*2.3.1 Embryology*

The exact etiology is unknown. Exposure to erythromycin has been implicated as a risk factor [1].

### *2.3.2 Clinical presentation*

It is characterized with feeding intolerance and non-bilious emesis that becomes projectile over time; usually presenting around 2–4 weeks of life, however, may not present up until 6–12 weeks. Emesis is non-bilious because the site of obstruction, the pylorus, is proximal to the ampulla of Vater. It tends to occur in first born Caucasian males.

## *2.3.3 Diagnosis*

On physical exam, may be able to palpate an "olive like" firm, mobile mass in the right upper quadrant or epigastrium, however this is often difficult to appreciate on a restless infant. Abdomen is otherwise soft and non-distended. Ultrasound is diagnostic and demonstrates a pyloric channel length ≥ 16 mm, wall ≥4 mm in thickness.

Repeated vomiting of gastric acid (HCl) leads to hypochloremia, alkalosis and dehydration. Hypovolemia stimulates aldosterone secretion with resultant sodium resorption and potassium secretion. Thus, the infant's laboratory panel will reveal hypochloremic, hypokalemic metabolic alkalosis. Hydrogen is shifted extracellularly in exchange for potassium to correct the acid–base imbalance, exacerbating hypokalemia. Eventually, worsening hypokalemia stimulates the renal hydrogenpotassium pump to resorb potassium and secrete hydrogen, resulting in acidic urine. This is termed "paradoxical aciduria" because bicarbonate secretion should take precedence in an alkalotic state, but the nephrons prioritize correction of potassium at the expense of hydrogen loss instead.

**Figure 2.** *Diamond duodenoduodenostomy for duodenal atresia repair.*

#### *2.3.4 Surgical management*

Pyloric stenosis is not a surgical emergency and operative intervention is deferred until electrolytes have normalized, ideally, chloride >95, bicarbonate <30. As the primary metabolic derangements are caused by volume and gastric juice loss, resuscitation should be initiated with 10-20 cc/kg normal saline boluses. Once volume status has been adequately restored and urine output robust, potassium containing fluids (D5 1/2NS + 10 K/L) are administered at maintenance rate.

The Ramstedt pyloromytomy was historically carried out through a right subcostal transverse incision however the laparoscopic approach is becoming preferred in current practice. A longitudinal incision along the anterior surface of the pylorus is carried down through the serosa and hypertrophied muscle until the submucosa protrudes, much like slicing the tough outer skin of a grape until the smooth inner flesh is encountered. The length of the myotomy extends from the antrum of the stomach proximally to the pyloric vein of Mayo distally, which designates the junction of the pylorus and proximal duodenum. Oral feeding may be initiated 6–8 h post-operatively and advanced as tolerated.

#### *2.3.5 Outcomes*

Long term results from pyloromyotomy are excellent and few infants, if any, have residual complications. Incomplete myotomy can present with persistent feeding intolerance in the peri-operative period and requires re-operation.

#### **2.4 Biliary atresia**

#### *2.4.1 Embryology*

The pathophysiology is unknown. Between 4 and 10 weeks of gestation, the extrahepatic biliary tract develops from the hepatic diverticulum. This occurs normally. In the post-natal period, there appears to be an inflammatory process that causes fibrosis of the extrahepatic biliary ducts [2].

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*Congenital Anomalies of the Gastrointestinal Tract DOI: http://dx.doi.org/10.5772/intechopen.92588*

dark urine and light or gray colored stools are present.

Worsening jaundice unamenable to phototherapy during the first 2 weeks of life, subsequently demonstrating unrelenting direct hyperbilirubinemia are characteristic. Laboratory values are consistent with biliary obstruction and demonstrate direct hyperbilirubinemia and elevated alkaline phosphatase. Signs of cholestasis,

Hepatobiliary technetium-99 iminodiacetic acid scan (99-Tc IDA) has highest sensitivity and specificity [2]. Normally, the radiotracer is taken up by hepatocytes and readily excreted into the intestines via the biliary ducts. In biliary atresia, technetium will be taken up by the liver normally, but obstruction of the extrahepatic ducts prevents outflow of radiotracer into the duodenum. Abdominal ultrasound may reveal a small or obliterated gallbladder. Magnetic resonance cholangiopancreatography (MRCP) is also be helpful in ruling out intrahepatic atresia or choledocal cysts.

Expeditious operative intervention is imperative as liver damage can be attenuated,

even reversed, and chance of survival improved with early biliary decompression. Beyond 3–4 months, irreversible liver damage may preclude successful outcome. The Kasai portoenterostomy is the procedure of choice. First, an intraoperative cholangiogram is performed to delineate the anatomy of the biliary tree and confirm the diagnosis. A liver biopsy is obtained to document degree of liver damage. Next, the fibrotic common bile duct is dissected from the hepatoduodenal ligament up to the level of the porta hepatis and excised. An approximately 20 cm limb of jejunum is brought up in a

Successful, long term establishment of bile flow correlates with earlier surgical intervention. Infants aged <60 days at time of surgery have best results. Approximately one-third of children undergoing portoenterostomy have a 10-year or greater survival, while the rest will ultimately succumb to liver failure and require transplant. Other indications for liver transplant include presence of intrahepatic atresia, fat soluble vitamin deficiencies causing failure to thrive and variceal bleeding secondary to portal hypertension. 5-year survival following liver

Apart from progressive liver failure, cholangitis is another major post-operative complication occurring in as much as 50% of patients who undergo portoenterostomy [2]. Decreased bile flow indicated by elevated total bilirubin in the setting of fever and leukocytosis is essentially diagnostic of cholangitis until proven other-

Etiology is unknown. Aberrant pancreaticobiliary junction near the duodenal

retrocolic fashion and a Roux-en-Y hepaticojejunostomy is created.

wise. It is managed with IV antibiotics and fluid resuscitation.

*2.4.2 Clinical presentation*

*2.4.4 Surgical management*

*2.4.3 Diagnosis*

*2.4.5 Outcomes*

transplant ranges from 75 to 95% [2].

**2.5 Choledochal cysts**

wall has been suggested [3].

*2.5.1 Embryology*
