Pediatric Surgery

         Hypertrophic pyloric stenosis (HPS) is idiopathic thickening and elongation of the pylorus that produces gastric outlet obstruction. HPS is the most common surgical cause of nonbilious vomiting in infants. Offspring of an affected parent have an increased incidence of HPS (10%); the highest rate (20%) occurs in boys born to affected mothers.

·         Congenital abnormalities of the diaphragm include a posterolateral defect (Bochdalek hernia), an anteromedial defect (Morgagni hernia), or the eventration (central weakening) of the diaphragm. The Bochdalek hernia is the most common variant and generally occurs on the left (80%) & posterior (BEHIND). Approximately 20% occur on the right, and < 1% are bilateral.

The most feared complication is persistent fetal circulation (PFC). In CDH, one or both lungs are hypoplastic, the pulmonary vascular bed is reduced, and the pulmonary arteries exhibit thickened muscular walls that are hyperreactive. Newborns with CDH are particularly prone to the development of pulmonary hypertension. PFC arises from a sustained increase in pulmonary artery pressure. Blood is shunted away from the lungs, and the unoxygenated blood is diverted to the systemic circulation (right-to-left shunt) through the patent ductus arteriosus and patent foramen ovale. PFC results in hypoxemia, profound acidosis, and shock. PFC is triggered by acidosis, hypercarbia, and hypoxia, all potent vasoconstrictors of the pulmonary circulation.

·         Hepatoblastomas usually occur in infants and young children, whereas hepatocellular carcinoma usually occurs in children older than 10 years. Hepatocellular carcinoma usually is associated with cirrhosis and hepatitis B and is histologically identical to the adult form. Surgical resection is the primary therapy for both tumors. Hepatoblastomas often have a good response to adjunctive chemotherapy, whereas hepatocellular carcinoma rarely responds to chemotherapy.

·         In neuroblastomas, age at presentation is the major prognostic factor. Children younger than 1 year have an overall survival rate > 70%, whereas the survival rate for children older than 1 year is < 35%. Shimada proposed a prognostic classification based on evaluation of histologic parameters (tumor differentiation, mitosis-karyorrhexis index [MKI]) as well as age. Aneuploid tumors, tumors with low MKI, and tumors with < 10 copies of the n-myc gene also have better outcomes.

Age is also important in children with Wilms' tumors, but the prognosis is better because the tumors are more readily excised and much more sensitive to chemotherapy.

·         CONGENITAL CYSTS AND SINUSES OF THE NECK

1. The most common brachial cleft anomaly is the second brachial cleft anomaly presenting near the mid- to upper border or the sternocleidomastoid muscle.
2. A thyroglossal duct cyst is the most common congenital cyst found in the neck.
3. A cystic hygroma is a congenital lymphatic malformation that is benign an usually presents as a soft mass in the lateral neck.
4. Because embryologically the thyroid descends before formation of the hyoid cartilage, the tract may pass right through the hyoid. Therefore, complete tract removal requires excision of the central portion of the hyoid and dissection up to the base of the tongue (i.e., the Sistrunk procedure).