Tuesday, October 23, 2012

Neonatal Intestinal Obstruction

A brief introduction to neonatal intestinal obstruction. A primer for medical students or residents of pediatric surgery on there first few day of training.

Classification:
Morphological:
Intrinsic:
  • Atresia: Complete intrinsic occlusion of the intestinal lumen
  • Stenosis: Refers to localized narrowing of the bowel or a diaphragm with a small perforation,  causing incomplete obstruction.
Extrinsic: e.g., volvulus, peritoneal band, annular pancreas
Level of Obstruction:
High:
e.g., pyloric atresia, duodenal atresia
Low:
e.g., ileal atresia or hisrschprungs disease

Functional:
  • Neonatal sepsis
  • NEC
  • Hypothyroidism
  • Electrolyte imbalance
  • Birth trauma
  • Prematurity
  • Transplacental transfer of maternal medication
Clinical Presentation:
  • Bilious or non-bilious vomiting
  • Abdominal distention
  • No or delayed passage of meconium
Natural History:
  • Aspiration pneumonia
  • Sepsis
  • Biochemical and hematological derangements
Causes of death:
  • Congenital anomalies
  • Intercurrent infections
  • Prematurity
Prenatal Diagnosis:
USG:
  • Polyhydramnios
  • Detection of lower atresia by seeing multiple distended bowel loops
  • Perforation can be picked by
    • Ascites
    • Meconium pseudocyst formation,
    • Calcification
Preoperative Preparation:
  • Insert nasogastric tube
  • Pass intravenous line
  • Replace losses (10-20 ml/kg/H) until adequate urine output maintained
  • In case of pneumonia, peritonitis, sepsis start antibiotics
  • Send CBC, serum electrolyte and renal function tests blood grouping and cross match.
  • One stable perform imaging investigations
  • Double IV Fluid maintenance if gastrograffin is to be used
  • Echo to rule out associated cardiac anomalies
Postoperative Care:
  • Total Parenteral Nutrition till oral feeding
Specific Diseases:
Pyloric atresia-epidermolysis bullosa syndrome:
All reported cases have Died before 11 months with or without surgery

Pyloric web: 
Pylorus is obliterated by a diaphragm.

Pyloric stenosis: 
Diaphragm with a small central hole in it causing incomplete obstruction. Late prsenting patients will have metabolic alakalosis.

Duodenal Atresia:
Most common location for atresia
Embryology: Failure of duodenal recanalization after 3rd week of gestation
Associations: Down syndrome, Trisomy 21, Congenital Heart Disease, renal, central nervous system, or musculoskeletal system, extrahepatic pancreaticobiliary ductal system and pancreas.
Risk: Prematurity
Operative Treatment:
Type 1:
Duodenotomy, excision and duodenoplasty. (locate CBD  by gently pressing the GB)
Type 2 and 3:
Duodenoduodenostomy + LADDS if required

Duodenal stenosis: 
Causes:
  • Diaphragm with a small central hole in it
  • Annular pancreas
  • Aberrant pancreatic tissue
  • Preduodenal portal vein
Differential Diagnosis: 
Malrotation. Confirm with upper GI contrast

Jejunal and Ileal Atresia:
Incidence: Distal Ileal and Proximal Jejunal atresia are most common
Embryology: Late intrauterine mesenteric vascular accidents such as volvulus, intussusception, internal hernias, bowel incarceration in an omphalocele or gastroschisis
Associations: Apple peal variety patients have  prematurity, malrotation, short gut syndrome, multiple atesia
Pathphysiology: 
  • Deficiency of coordinated peristalsis
  • Hyperplasia of ganglion cells in the dilated proximal segment
  • Absent acetylcholinesterase activity at the ends of proximal and distal atretic segments
Differential Diagnosis:
  • Meconium ileus
  • Hirschprungs Disease
Operative Treatment Principles
  • Preserve as much bowel as possible
  • Resect proximal dilated bowel
  • Tapering or Plication if short bowel syndrome is feared
  • Check for distal patency
  • End to End to End to Oblique Primary anastomosis is preferred
Malrotation:
Embryology:
Malrotation occurs due to failure of gastrointestinal tract to complete its normal rotation and fixation as it return to abdominal cavity during 8th to 10th week of gestation
Incidence:
  • 50-75% present before one month
Diagnosis:
  • Upper GI contrast: extrinsic compression and torsion (corkscrew, coiled or bird’s beak sign)
  • Abdominal USG (Doppler USG) Relationship of Superior mesenteric artery and vein
Complications:
  • Volvulus
Clinical Features:
  • Abdominal distention
  • Pain
  • Rectal bleeding
Natural history:
  • Hypotension
  • Respiratory failure
  • Systemic acidosis
  • Sepsis
Diagnosis: 
  • Airless abdomen on x-ray. 
  • Can also be diagnosed by color doppler
Treatment:
  • It is a Surgical Emergency.
Operative Steps:
  • Evisceration of Bowel

  • Derotation in anticlockwise direction. 
  • Division of LADDS bands
  • Splaying of mesentery
  • Appendectomy
  • Small bowel is placed on left and cecum on right parallel to each other
Meconium Ileus:
Simple: 
Retention of think tenacious meconium in bowel causing obstruction
Complicated:
  • Giant meconium cyst
  • Meconium peritonitis,
  • calcification in the peritoneal cavity
Most common cause: 
Cystic Fibrosis. Rare in Asians
Presentation:
  • Present with adbdominal distention at birth.
  • In complicated meconium ileus the abdomen is erythrematous, oedematous, distened, with signs of peritonitis. When a mass is palpalble it indicated psudocsyt formation.
Radiography:
  • Soap bubble or Ground-glass appearanc
  • for complicated calcification, ascites, gas under diapgragm.
Treatment:
For Simple Meconium Ileus a Contrast enema is diagnostic and therapeutic. More than two is required. The success rate is around 60-70%.If not successful than laparotomy is needed.
Operative Principles:
  • Enterotomy in the dilated segment of bowel
  • Emulsify Meconium by gastrograffin or nacetylcysteine 1-4 %
  • Evacuate meconium
  • Preserve as much of bowel length as possible
  • With or without Stoma
For Complicated Meconium Ileus Operative resection with or without Stoma is required.
Postoperative Care:
  • Wash the distal loop with the indwelling catheter
  • Give oral n-acetylcystein
  • Start pancreatic enzymes
Hirschprungs Disease:
Embryology:
Caused by abnormal migration of neural crest cell. The early the failure the higher the aganglionic segement.Most commonly it is upto rectosigmoid junction
Diagnosis: 
  • Per-Rectal Examination
  • Barium enema
  • Rectal biopsy
Treatment:
Rectal washouts to keep bowel clean
Surgical options:
  • Colostomy folowed by Duhamel
  • One stage endorectal pullthorugh open or laparoscopic using frozen section biopsy
Imperforate Anus:
Emergency Surgery:
  • Sigmoid lop colostomy
Definitive Management:
  • Investigate
  • Definitive Surgery
Meconium plug syndrome:
Inspissated and dehydrated meconium in the distal colon and rectum
Etiology:
  • Diabetic mothers
  • Hypothyroid babies
  • Premature infants
Differnetial Diagnosis:
  • Hirschprungs Disease: Rectal biopsy to rule out
  • Cystic Fibrosis: Sweat test after 6 weeks to rule out
Treatment:
  • Revealed and healed by contrast enema
Small left colon:
Diagnostic Pointer on xray is rectum is dilated but left colon not. Treatment is complex.

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