Read Core Topics in General & Emergency Surgery: Companion to Specialist Surgical Practice Online
Authors: Simon Paterson-Brown MBBS MPhil MS FRCS
Core Topics in General & Emergency Surgery: Companion to Specialist Surgical Practice (57 page)
Dafydd A. Davies and
Jacob C. Langer
While paediatric surgery has increasingly become the domain of the subspecialist paediatric surgeon, adult general surgeons are still often faced with the challenges of assessing and managing children with surgical emergencies. The unique differences between adults and children must be taken into account when addressing every aspect of surgical management, including assessment, diagnosis, resuscitation and operative interventions. Children face a different spectrum of conditions, have different physiological responses to trauma, illness and surgical stress, and have different psychosocial needs.
This chapter will address the common abdominal paediatric surgical emergencies encountered by general surgeons. These will be categorised according to age: (i) Neonates (up to 44 weeks postgestational age), (ii) infants (1 month to 2 years of age) and (iii) children (2 years of age and older).
Prenatal diagnosis
Routine prenatal ultrasonography has become the standard of care in many parts of the developed world, and has resulted in the detection of many congenital anomalies before birth. Common detectable anomalies relevant to the general surgeon include: abdominal wall defects, congenital diaphragmatic hernia, intestinal obstruction, and intra-abdominal masses.
Whenever possible these patients should be referred for prenatal consultation with obstetrics, neonatology and paediatric general surgery. In most cases, delivery should occur at a hospital with a neonatal intensive care unit and paediatric surgical service. If this is not possible they should be immediately transferred following delivery and resuscitation.
Intestinal obstruction is the most common abdominal emergency in the neonatal period, and is usually due to a congenital, developmental or genetic anomaly.
Assessing neonatal patients for obstruction requires a thorough history, including the nature of any vomiting and the presence or absence of abdominal distention. Since neonates are unable to verbalise, surgeons must gather as many clues as possible from the prenatal, perinatal and family historical details (
Table 12.1
).
Table 12.1
Important considerations in the neonatal history
Examination of neonates with suspected intestinal obstruction should start with vital signs and an assessment of the level of resuscitation required. Certain forms of obstruction can cause severe dehydration or sepsis, which will need to be addressed early. Dysmorphic features may give clues to syndromes in which obstruction is common. The abdominal examination should make note of any discoloration, distention and signs of peritoneal inflammation, such as guarding and rigidity. It is important to look for an incarcerated inguinal hernia as the cause of obstruction (see later). A thorough evaluation of the perineum must also be carried out to ensure normal location and patency of the anus.
Routine blood tests including electrolytes and full blood count are helpful in assessing the level of dehydration as well as helping determine if electrolyte disturbances or sepsis are contributing to the presentation. It should be kept in mind that serum creatinine in the newborn reflects the mother's levels, and may not be helpful in assessing the neonate's renal function.
Abdominal radiography should be the initial imaging modality for neonates with possible intestinal obstruction. Typically, infants with duodenal obstruction have a ‘double-bubble’ appearance (
Fig. 12. 1
), whereas those with distal intestinal obstruction will have multiple dilated bowel loops. It is impossible to differentiate distal small-bowel obstruction from colonic obstruction based on the plain abdominal radiograph in neonates, as the haustral markings seen in adults are not visible in this age group.
Figure 12.1
Abdominal radiograph of an infant showing the typical ‘double-bubble’ appearance resulting from duodenal obstruction.
A contrast study is often required to definitively diagnose the aetiology of intestinal obstruction. If malrotation is suspected, an urgent upper gastrointestinal contrast study should be performed first. Once this diagnosis has been excluded a contrast enema can be done to exclude distal pathology if this is indicated. For those infants with distal obstruction on plain radiograph, a contrast enema will help to differentiate the three most common causes of distal obstruction: meconium ileus, jejuno-ileal atresia and Hirschsprung's disease (
Fig. 12.2
). Water-soluble contrast should always be used instead of barium, to avoid the possibility of barium leaking into the abdominal cavity should a perforation occur, and also because water-soluble contrast is more effective in relieving the obstruction in cases of meconium obstruction.
Figure 12.2
Water-soluble contrast enemas of infants with distal bowel obstruction.
(a)
Meconium ileus, showing a microcolon, dilated proximal small bowel and a soap-bubble appearance in the right lower quadrant.
(b)
Ileal atresia, showing a microcolon, contrast entering the distal small bowel but dilated proximal small bowel without contrast.
(c)
Hirschsprung's disease: lateral film showing a contracted distal rectum with dilated bowel proximally.
Neonates with suspected intestinal obstruction should be transferred in a temperature-controlled transport isolette to a specialised paediatric surgical unit for evaluation and definitive management. Resuscitation should begin as soon as the patient is assessed and should continue during transport. Nasogastric decompression with a large-calibre nasogastric tube (size 8–10 French) is important to improve ventilation, monitor resuscitation, and limit bowel distention and subsequent ischaemia.
Oesophageal atresia:
This anomaly is characterised by a gap in the oesophagus, resulting in a blind-ending proximal pouch. In 90% of cases, the distal oesophagus is connected to the back of the trachea as a tracheo- oesophageal fistula. Oesophageal atresia is usually first suspected when the baby has difficulty swallowing saliva and may have coughing or respiratory distress during the first feed.
1
Intubation may be needed if ventilation or respiration are significantly impaired. The diagnosis is confirmed by the inability to pass a 10–12 French nasogastric tube. This tube should be left in the proximal oesophageal pouch and placed on suction to prevent aspiration of secretions. Operative repair should only be performed by an experienced paediatric surgeon and involves division of the fistula and end-to-end anastamosis of the proximal and distal oesophagus.
Meconium ileus:
Cystic fibrosis (CF) is the most common autosomal recessive disorder in Caucasian children.
2
The disease alters the regulation of chloride transport in epithelial cells, resulting in a variety of clinical manifestations. Ten to fifteen per cent of children born with CF will develop meconium ileus, in which the meconium becomes sticky and causes intraluminal obstruction. This can further lead to complications of volvulus, atresia or perforation. In addition, meconium ileus may occasionally occur in children without CF. A diagnostic work-up, including both sweat chloride determination and genetic studies, must therefore be performed on all children with meconium ileus.
Abdominal radiographs may show distal intestinal obstruction with a bubbly appearance in the right lower quadrant due to gas mixing with the viscous meconium (
Fig. 12.2a
).
2
There may also be intraperitoneal calcification if in-utero perforation has occurred.
Following resuscitation and nasogastric decompression, a water-soluble contrast enema will reveal a microcolon (small calibre) and multiple meconium plugs in the terminal ileum (
Fig. 12.2a
). In approximately 50% of cases, the contrast enema will relieve the obstruction. If progress is made, but the infant remains obstructed after the initial enema and is otherwise stable, the procedure can be repeated. If the contrast enema is unsuccessful in relieving the obstruction and/or no further progress has been made, a laparotomy must be carried out. If there is no volvulus or perforation, enterotomies are made and mechanical washout is performed. Complications of volvulus, acquired atresia or perforation are managed by intestinal resection with or without a stoma, depending on the condition of the bowel and of the patient.
Intestinal atresia/stenosis:
Atresia and stenosis can occur at any point in the alimentary canal. The two prominent aetiological theories are failure of recanalisation of the intestine during foetal development or an ischaemic event in utero.
3
Early resuscitative measures should be initiated and confirmatory diagnosis can usually be made with either upper or lower gastrointestinal contrast studies. The presence of a ‘double-bubble’ sign on abdominal radiograph is considered diagnostic for duodenal atresia (
Fig. 12.1
), although this finding associated with distal gas may also be due to stenosis, duodenal web, or malrotation. Trisomy 21 is present in one-third of children with duodenal atresia. Patients with distal atresia will typically have multiple dilated loops of bowel on the plain abdominal radiograph. Although a diagnosis of proximal obstruction can be confidently made based on plain radiography, those with distal obstruction should always undergo water-soluble contrast enema to differentiate atresia from meconium ileus or Hirschsprung's disease.
Since most infants with intestinal atresia are stable once decompressed and resuscitated, they should then be transferred to a facility with paediatric surgical expertise. Most of these anomalies are treated with a primary anastomosis. If there is significant dilatation of the proximal segment, a tapering enteroplasty should be performed as the dilated bowel tends not to have effective peristalsis.
Hirschsprung's disease:
Hirschsprung's disease (HD) is a congenital disorder characterised by a lack of ganglion cells in the distal bowel. This results in failure of peristalsis and functional obstruction. The ‘transition zone’ is usually located in the rectosigmoid region, but HD can affect the entire colon and in rare occurrences the small bowel. HD most often presents in the neonatal period with distal bowel obstruction and failure to pass meconium in the first 24 hours of life. Patients can present later in life with a history of severe constipation. Early identification and management are important to prevent complications of HD such as enterocolitis and nutritional problems.
Water-soluble contrast enema has a sensitivity and specificity of 70% and 83%, respectively, and may therefore be normal, particularly in the newborn.
4
The gold standard for the diagnosis of HD is rectal biopsy, either by a suction technique at the bedside or full-thickness biopsy.
Initial management, after resuscitation and nasogastric decompression, includes digital rectal stimulation and/or rectal irrigations (10 mL/kg normal saline).
Although the historical teaching used to be routine diverting colostomy followed by a ‘pull-through’ operation several months later, the current standard of care is primary reconstructive surgery without a routine colostomy in most patients.
5
Preliminary colostomy should be reserved for infants presenting with severe enterocolitis or colonic perforation.
There are a number of options for the surgical correction of HD, including the Swenson, Soave and Duhamel procedures. In recent years, laparoscopic and trans-anal approaches have been described, which have decreased morbidity and shortened hospital stay. It goes without saying that these operations should all be carried out by an experienced paediatric surgeon.
Anorectal malformations:
Anorectal malformations can be divided into low and high anomalies. Low anomalies are characterised by rectoperineal or rectovestibular fistulas in female patients. Most males with high malformations have a fistula from the rectum to the bladder neck or urethra. Females with high anomalies usually have a single channel (cloaca) formed by coalescence of the urethra, vagina, and rectum. Less commonly, there may be rectal atresia without a fistula, and some infants present with an anal membrane or anal stenosis.
Infants with these malformations usually present in the first day of life with distal bowel obstruction. Low malformations in girls with large fistulas can permit adequate evacuation of stool, and are occasionally missed. Careful examination of the perineum of all newborns for anal patency and position is therefore important. Many of these patients will suffer from associated anomalies which need to be investigated prior to proceeding with anatomical repair of the anorectal malformation.
The next consideration is to determine if the defect is amenable to primary repair or whether faecal flow should be diverted with a colostomy followed by delayed secondary anatomical repair. Children with a rectoperineal fistula can usually be managed with a local procedure from below, without a colostomy. Children with high anomalies are usually managed with a preliminary colostomy. The use of a colostomy in females with a rectovestibular fistula is controversial. The colostomy can be made using either the transverse or the sigmoid colon, and can be a loop or divided stoma. The authors favour Pena's recommendation for a divided colostomy in the proximal sigmoid colon.
6
Long-term continence in these patients is determined by the level of the rectal fistula, and the presence of an absent or hypoplastic sacrum. Depending on the nature of the anomaly, repair can be carried out using a posterior sagittal approach, a laparoscopic approach, or a combination of posterior and abdominal approaches. Technical expertise is crucial to success, and again these procedures should only be performed by experienced paediatric surgeons.
Malrotation:
The process of normal rotation and fixation occurs between the sixth and tenth weeks of development. If no rotation occurs, the patient is left in a position of non-rotation, which has a wide-based mesentery and does not require correction. Classic malrotation occurs when the process is interrupted part way through, leaving the caecum and the duodeno-jejunal junction (ligament of Treitz) close to each other (
Fig. 12.3
). Because this arrangement results in a narrow-based mesentery, the bowel is prone to midgut volvulus around the superior mesenteric vessels, which may lead to intestinal ischaemia. Malrotation with midgut volvulus is one of the true paediatric surgical emergencies and failure to recognise it early can be catastrophic, leading to loss of large portions of bowel and subsequent short-bowel syndrome or death.
Figure 12.3
Schematic illustrations depicting normal intestinal rotation, non-rotation and malrotation. Bold dotted lines illustrate the width of the mesenteric base in each situation.
Rotation abnormalities are most often asymptomatic. While volvulus can occur at any time, it is most common in the first week of life.
7
The most common presentation of malrotation is bilious vomiting, which may occur for two reasons: midgut volvulus with kinking of the duodenum, or compression of the duodenum by Ladd's bands. Peritonitis and shock from midgut volvulus are late symptoms and are associated with a worse prognosis. Every attempt should be made to diagnose and correct malrotation before this occurs.
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For this reason, every infant who presents with bilious vomiting should be considered to have malrotation with midgut volvulus until proven otherwise.
Any patient with suspected malrotation and volvulus needs urgent imaging and surgical consultation. Abdominal radiograph is often non-diagnostic but may show a dilated stomach, a ‘double bubble’ with distal gas or a relatively gasless abdomen. Upper gastrointestinal contrast study is the preferred examination. A nasogastric tube placed prior to the exam can not only aid in decompression of the stomach, but also the administration of the water-soluble contrast. The chief radiographic signs of malrotation are: (1) abnormal position of the duodenojejunal junction, (2) a spiral, ‘corkscrew’ or Z-shaped course of the distal duodenum and proximal jejunum, and (3) location of the proximal jejunum in the right abdomen.
8
Abdominal ultrasound may show abnormal orientation of the superior mesenteric artery and vein, or a ‘whirlpool sign’.
9
The operation to correct malrotation involves a laparotomy, although a laparoscopic approach may be taken for children without evidence of volvulus.
10
If there is volvulus, the bowel is untwisted and checked for viability. If there is ischaemia, the bowel is wrapped with warm towels and re- inspected. Grossly necrotic bowel is resected and the rest is left, with a second-look laparotomy planned for 24–48 hours later. In children who have necrosis of the entire midgut, a palliative approach should be considered.
If the intestine is viable, a Ladd procedure should be performed. This operation consists of five stages: (1) division of Ladd's bands; (2) mobilisation of the colon to the left side of the abdomen; (3) mobilisation and straightening of the duodenum; (4) dissection and widening of the small bowel mesentery; and (5) appendicectomy.