Congenital Diaphragmatic Hernia - PDF

Almustansiriyah University Pediatric Surgery College of Medicine Dr. Muhamed Jassim Department of Surgery MBChB - F.I.C.M.S Congenital d...

Almustansiriyah University Pediatric Surgery College of Medicine Dr. Muhamed Jassim Department of Surgery MBChB - F.I.C.M.S Congenital diaphragmatic hernia Congenital diaphragmatic hernia (CDH) is herniation of abdominal viscera to the thoracic cavity through a congenital (developmental) defect in the diaphragm. In ninety percent of cases; Bochdalek CDH , and the remainders are located Morgagni CDHs diaphragmatic defect is left sided in 80%, right sided in 19%, and bilateral in 1% of cases. The incidence rate of congenital diaphragmatic hernia is about 1/2000 live births and affects male infants more commonly. Associated anomalies are reported in about 40% of cases as cardiovascular, urogenital, musculoskeletal, neurological, and chromosomal anomalies. 1 Etiology and Pathophysiology: Embryologically, the diaphragm begins to develop in the fourth week of gestation by a complex interaction and fusion of four embryonic elements: Septum transversum anteriorly. Esophageal mesentery posteriorly. Pleuroperitoneal folds laterally. Muscular ingrowth from body wall posterolaterally. Initially, the septum transversum grows and migrates posteriorly to fuse with the esophageal mesentery, this will separate the heart (pericardial cavity) from the liver (peritoneal cavity). At that time, the pleural and peritoneal cavities are still communicated through a paired pleuroperitoneal canals that located on either side of the esophagus. Then the pleuroperitoneal folds will grow and migrate medially to fuse with the esophageal mesentery and septum transversum to close the pleuroperitoneal canals. Fusion of these components is completed at 7- 8 week of gestation forming the primitive diaphragm and typically the right side of the diaphragm is closed before the left one. Finally, phrenic axons and myogenic cells migrate to the primitive diaphragm accompanied by muscular ingrowth from body wall forming the mature diaphragm. Congenital diaphragmatic hernia is thought to be caused by failure of the pleuroperitoneal fold to close the pleuroperitoneal canal completely resulting in a diaphragmatic defect which allows the abdominal viscera as stomach, small bowel, colon, left lobe of liver and /or spleen to herniate to the thoracic cavity. The herniated abdominal organs will compress the lung during a critical period of lung development causing pulmonary hypoplasia in both ipsilateral and contralateral lungs. Pulmonary hypoplasia is characterized by: Decreased airway branching. 2  Decreased bronchioles and alveoli. Presence of abnormal thick intra-alveolar septations that impair gas exchange. Surfactant deficiency. Abnormally thick-walled pulmonary vasculature causing pulmonary hypertension. The pulmonary hypertension in turn will cause persistent fetal circulation with right to left shunt (through both foramen ovale and ductus arteriosus). The right-left shunt will cause passage of deoxygenated blood to the systemic circulation, resulting in hypoxemia, hypercapnia, hypoxia, and acidosis. All these changes will stimulate pulmonary vasoconstriction which will worsen the pulmonary hypertension. Clinical features: Newborns with congenital diaphragmatic hernia (CDH) typically present with respiratory distress and cyanosis. The spectrum of presentation can vary from immediate, profound respiratory distress at birth (most common), to an initial stable period with delayed respiratory distress, to an asymptomatic newborn. The physical findings on examination include: Signs of respiratory distress as tachypnea, chest wall retraction, grunting, and cyanosis. Scaphoid abdomen. Increased anteroposterior diameter of the chest (barrel chest). On chest auscultation; there is decreased breath sounds bilaterally, positive bowel sounds on the ipsilateral side and displaced cardiac impulse to the contralateral side due to mediastinal shift. Although most newborns with CDH are diagnosed in the first 24 hours of life, as many as 20% of cases may present beyond the neonatal period with mid respiratory symptoms, recurrent respiratory infections, and feeding intolerance. Sometimes the presentation may be with intestinal obstruction due to bowel entrapment through the diaphragmatic defect, or volvulus as CDH is invariably associated with abnormal intestinal rotation and fixation. Investigations: Laboratory tests: blood gas analysis: to assess PH, PaO2, PaCO2, and acid-base status. In CDH there is hypoxemia, hypercapnia, and respiratory acidosis. Serum lactate: is significantly elevated due to tissue hypoxia. Chest X-ray: the diagnosis of CDH is typically confirmed by chest radiograph demonstrating bowel loops within the hemithorax, mediastinal shift toward the contralateral side, minimal bowel gases in the abdomen, and displacement of nasogastric tube to the thoracic cavity. Echocardiography: to assess ventricular contractility, pulmonary hypertension, right to left shunting and to identify any associated cardiac defects. 3  Renal ultrasonography: to rule out genitourinary anomalies. Cranial ultrasonography and Magnetic resonant imagining (MRI): to identify associated cranial anomalies and to assess any hypoxic-ischemic changes. Chromosomal studies: to identify any associated chromosomal anomalies. Management: Congenital diaphragmatic hernia is NOT a surgical emergency, the initial management is resuscitation and stabilization of newborns with cardiopulmonary distress. The resuscitative measures include: Oxygen supply by nasal cannula. Mask and bag ventilation should be avoided as it causes more gastric and intestinal distention from the swallowed air which will compromise the respiratory distress. Placement of nasogastric or orogastric tube to prevent gastric and intestinal distention. Establishment of arterial and venous access both for resuscitation and monitoring. IV fluid therapy with insertion of urinary catheter to monitor fluid resuscitation. Surfactant therapy is indicated for patient with extreme prematurity. Administration of pulmonary vasodilators to treat pulmonary hypertension as inhaled nitric oxide (iNO). Ventilatory support for patients with persistent hypoxemia / hypercapnia and include: Endotracheal intubation and conventional ventilation using pressure-controlled mode with a maximum safe pressure of 25 cm H2O. Higher pressure is associated with higher risk of barotrauma. High frequency oscillatory ventilation (HFOV) is indicated if hypoxemia/hypercapnia cannot be controlled with conventional ventilation. Extracorporeal membrane oxygenation (ECMO) is indicated if the above measures fail to correct the hypoxemia. The targets of full and adequate resuscitation are: PaO2 > 85mmHg. PaCO2 < 70mmHg. pH > 7.2 Evidence of good tissue perfusion as resolution of cyanosis, good urine output, and serum lactate less than 3 mmol/L. After adequate resuscitation and stabilization; surgical repair of congenital diaphragmatic hernia can be carried out either by the traditional open approach (laparotomy or thoracotomy), or by minimally invasive approach (laparoscopy or thoracoscopy). The laparotomy approach is the most commonly used approach and usually done through a subcostal incision and less commonly 4 through a midline abdominal incision. The principles of surgical repair include: reduction of the herniated abdominal viscera, excision of the hernia sac that present in about 20% of cases, and closure of the diaphragmatic defect. If the diaphragmatic defect is large enough to preclude primary closure; a prosthetic mesh or autologous tissue flap (as abdominal wall or chest wall muscle flaps) can be used to close the defect. Morgagni hernia Anterior (Morgagni) diaphragmatic hernia accounts for < 2% of CDHs. It results from failure of fusion of the sternal and the costal portions of the diaphragm mainly on the right side. Typically, a hernia sac is present and contains stomach, omentum, small intestine, and/or colon and rarely the liver and/or spleen. Clinical features: The majority of children with Morgagni hernia are asymptomatic at birth and present during childhood with recurrent respiratory infections, epigastric discomfort, vomiting, and sometimes intestinal obstruction. Diagnosis: The diagnosis of Morgagni hernia can be established by chest radiograph which shows bowel loops in the retrosternal space with air-fluid levels. Sometime, contrast radiograph as barium meal and enema, or CT scan may be needed to confirm the diagnosis. Treatment: Operative repair of Morgagni hernia can be done by an open approach through upper midline or transverse incisions, or by minimally invasive approach as laparoscopy. The surgical management involves reduction of the herniated viscera, excision of the hernia sac, and closure of the diaphragmatic defect with or without a mesh according to the size of the defect. 5  Diaphragmatic eventration Diaphragmatic eventration is abnormal paradoxical movement of the diaphragm during respiration that interferes with the pulmonary mechanics and function. Normally, the diaphragm is a dome shaped muscle that contract (moved down) during inspiration so the intrathoracic space is increased to allow adequate lung expansion, and relax (move up) during expiration to help in expelling the air from the lung. In diaphragmatic eventration; this movement is reversed causing impairment of pulmonary function. Diaphragmatic eventration is classified into two types: Congenital diaphragmatic eventration: is caused by incomplete development of the diaphragm and commonly occurs on the left side. Large eventration may interfere with lung development and can cause pulmonary hypoplasia as CDH, but pulmonary hypertension and persistent fetal circulation are usually not seen in the eventration. Acquired diaphragmatic eventration: is caused by injury to the phrenic nerve by birth trauma, during cardiac surgery, or invasive mediastinal tumor. Clinical features: Clinically, diaphragmatic eventration may present acutely with respiratory distress in the neonatal period, or may present during early childhood with recurrent chest infections, wheezing, feeding intolerance, vomiting, and exercise intolerance. Diagnosis: The diagnosis of diaphragmatic eventration is usually suspected on plain chest radiograph showing an elevated hemidiaphragm, and confirmed by fluoroscopy which identify the abnormal paradoxical movement of the diaphragm with respiration. Treatment: Surgical intervention is indicated for a large eventration that associated with impaired pulmonary function and /or recurrent respiratory infections. The procedure of choice is diaphragmatic plication by series of nonabsorbable sutures, so the diaphragm become immobile and taut. This will increase the intrathoracic volume during inspiration, allowing good lung expansion and improving the tidal volume and the overall pulmonary function. 6 Small diaphragmatic eventration with minimal or no symptoms can be observed, as most patients will overcome and compensate for the abnormal diaphragmatic dynamics with time. 7 Almustansiriyah University Pediatric Surgery College of Medicine Dr. Muhamed Jassim Department of Surgery MBChB - F.I.C.M.S ─────────────────────────────────────────────── Meconium Ileus Meconium ileus (MI) is obstruction of the terminal ileum by extremely thick, tenacious, and viscid meconium. It is one of the common causes of intestinal obstruction in the newborn, accounting for about 9-33% of neonatal intestinal obstruction. The incidence rate is about 1/2000 live births and affects both genders equally. Etiology: Meconium ileus is the earliest clinical manifestation of cystic fibrosis (CF), occurring in about 16% of patients with CF and considered a pathognomonic for it. Cystic fibrosis is an autosomal recessive disease characterized by mucoviscidosis (increased mucous viscosity) of the exocrine secretions throughout the body. It is caused by a mutation in the cystic fibrosis transmembrane (conductance) regulator (CFTR) gene, which located on the long arm of chromosome 7. The CFTR gene encodes for chloride channels which control the flow of chloride ions across the apical surface of the epithelial cells. The transport of chloride ions is accompanied by movement of water in tissues which is necessary to produce thin, freely flowing mucous. 1  The result of mutation is a thick and sticky secretion that obstruct the tubular structures lined by the affected epithelium (as respiratory, gastrointestinal, pancreatic, biliary, genital, and sweat glands). The most common mutation is F508del that results in removal of phenylalanine amino acid at position 508 of CFTR gene, and is found in approximately 70% of cases. In the gastrointestinal tract, the thick, sticky, and tar like meconium is impacted in the terminal ileum causing intraluminal bowel obstruction. Also, the abnormally thick pancreatic secretion will obstruct the pancreatic ductal system causing autodigestion of the acinar cells, fatty replacement of pancreatic parenchyma, and fibrosis resulting in pancreatic insufficiency. Classification: Meconium ileus is classified into two types: ❖ Simple meconium ileus: when meconium ileus is not associated with any complication and reported in approximately one half of patients. In simple meconium ileus the terminal ileum is filled with firm concretion of meconium and is small in diameter, proximal to this area the bowel is dilated by thick meconium with gases and fluid. ❖ Complicated meconium ileus: when meconium ileus is complicated by: Volvulus. Intestinal atresia. Intestinal perforation Meconium peritonitis. Pseudocyst formation. Clinical presentations: Newborns with simple meconium ileus usually appear healthy at birth. However, within 1-2 days they develop progressive abdominal distension, bilious emesis, with no passage of meconium. Eventually, the dilated bowel loops become visible on examination and have a characteristic doughy character on palpation. The rectum and anus are often narrow and may be misdiagnosed as anal stenosis. While in complicated meconium ileus, the presentation is usually within the first 24 hours of life and sometime immediately after birth due to in utero bowel perforation or bowel compromise. Signs of peritonitis are usually found on initial neonatal examination as abdominal distention, tenderness, abdominal wall edema and erythema, and clinical evidence of sepsis. Sometimes, the abdominal distension may be severe enough to cause respiratory distress. A palpable abdominal mass may be felt on abdominal examination and indicate pseudocyst formation, which result from in utero bowel perforation followed by capsulation of the meconium in the peritoneal cavity. 2 Diagnosis: ❖ Plain abdominal radiography: In simple meconium ileus, the abdominal x-ray shows evidence of distal small bowel obstruction as dilated bowel loops and absence of air in the rectum with few or no air-fluid levels. The absence of air-fluid levels is due to high viscosity of the meconium that prevents the air to interface with the fluid. Instead, the swallowed air is mixed with the tenacious meconium producing soap bubble or ground glass appearance. While in complicated meconium ileus, the abdominal radiography may show peritoneal calcifications, pneumoperitoneum (in cases of bowel perforation), or a large dense mass with a rim of calcification which imply the presence of pseudocyst. ❖ Contrast enema: By administration of water-soluble contrast material to the colon through a catheter placed in the rectum. The contrast enema will demonstrate a colon of small diameter, often described as “microcolon of disuse” and filled with pellets of meconium. Management: Neonates with meconium ileus are resuscitated initially as any case of intestinal obstruction by: IV fluid administration. Gastric decompression by insertion of nasogastric or orogastric tube to prevent abdominal distension, aspiration, and pulmonary complications. Administration of broad-spectrum antibiotics. Ventilatory support as necessary. Correction of electrolytes disturbances. Non operative management: The majority of newborns with simple meconium ileus can be managed nonoperatively by administration of isotonic water-soluble contrast enema under fluoroscopic control. The enema fluid will dilute and soften the thickened meconium to be evacuated normally from the anus. The most commonly used enema is warm saline enema with the addition of N-acetylcysteine which help to dissolve the meconium. The N-acetylcysteine should also be administrated through the nasogastric tube to dissolve the thick secretion in the upper gastrointestinal tract. Successful enema is defined by passage of meconium pellets followed by semifluid meconium few hours after administration. Once the obstruction is relived, oral feeding can be started and increased gradually as tolerated with pancreatic enzymes supplementation. 3 Operative management: In simple meconium ileus, operative intervention is indicated in the following circumstances: Failed two attempts of non-operative treatment as evident by inadequate meconium evacuation and persistent clinical features. Complications of non-operative treatment as bowel perforation. The principles of surgical intervention involve evacuation of the tenacious meconium manually through an enterotomy incision made in the ileum. The evacuation can be aided by intraoperative instillation of N-acetylcysteine or saline solution. An ileostomy is usually created, and usually closed after 4-6 weeks. While in complicated meconium ileus, operative management is almost always indicated. The surgical intervention includes debridement of necrotic material, resection of compromised bowel segment(s), pseudocyst resection, and creation of a diverting ileostomy. Postoperatively, whether simple or complicated MI, N-acetylcysteine is instilled through the nasogastric tube and the ileostomy openings to dissolve and solubilize any residual meconium. Prognosis: The prognosis of infants with meconium ileus was uniformly poor with a reported mortality rate of about 50-67%. However, the prognosis of meconium ileus is improved dramatically in the last few years due to advances in prenatal diagnosis, pulmonary and neonatal intensive care, nutrition, antibiotics, anesthesia, operative management, and improved understanding of the pathophysiology and treatment of cystic fibrosis. Now day, the survival rate is about 85-100% in simple meconium ileus and up to 93% in complicated meconium ileus. 4