Definitions and Epidemiology
The term “emergency” is subjective and therefore can be difficult to define, especially when considering all the complexities of caring for a sick child with a surgical problem. To the anxious parent, anything surgical may be an emergency. Healthcare providers often have differing perspectives on what is or is not an emergency. The topics in this chapter are all surgical issues that need intervention, most in a relatively short period of time. But some might be considered “urgencies” rather than true surgical emergencies. For example, most surgeons do not consider appendicitis and pyloric stenosis as true surgical emergencies. The infant with pyloric stenosis is often delayed hours, possibly even days, while undergoing the necessary fluid rehydration and resuscitation. Likewise, appendicitis can be temporized with IV antibiotics overnight and taken to the operating room the following morning. Conversely, malrotation with midgut volvulus and other causes of ischemic bowel are always surgical emergencies due to the impending irreversible effects of ongoing ischemia. Finally, there are many diagnoses that may fall over a wide spectrum of severity. Therefore, the clinical picture will often dictate the presence of an emergency more than the diagnosis. Many congenital and acquired pediatric surgical issues can progress to emergencies if the underlying problem has been present long enough. In a general sense, intervention for surgical emergencies and the less acute surgical urgencies fall into four categories: obstruction, ischemia, perforation, and bleeding.
Clinical Presentation and Treatment
The first step in the evaluation and treatment of a patient with a possible surgical emergency is resuscitation. Fluid losses can be massive from bleeding and bowel obstructions, while enormous third spacing can occur from perforation and ischemia. Choice of fluid replacement depends on where the loss occurs but should be isotonic early in the resuscitation, using either lactated Ringer’s (LR) solution or normal saline (NS). For most fluid losses and conditions where acidosis is present, LR is a better selection. It is the fluid replacement of choice for trauma, and many surgical problems can be compared to a trauma situation. LR contains electrolytes much closer to physiological serum chemistries than NS and also contains lactate for buffering. The lactate in LR does not contribute to the acidosis; in fact, it has the opposite effect. The lactate is rapidly converted to bicarbonate by the first-pass effect of the liver and will improve a patient’s acidotic picture much more effectively than NS. Moreover, the pH of NS is acidic (5.0) and can worsen an underlying acidosis. Conversely, NS is a far better choice for upper GI fluid losses such as excessive emesis. Pyloric stenosis is the best example. In these patients, the emesis has progressed to such an extreme that a severe hypochloremic metabolic alkalosis results. The acidic nature and high chloride concentration (154 mEq/L) of NS make this fluid the ideal resuscitation fluid for upper GI losses.
Once resuscitation has been initiated, diagnostic workup can begin. Age is a key factor in determining where the problem is likely to be found. Bleeding is evaluated by upper or lower endoscopy or a radionucleotide scan. Possible obstruction or perforation is evaluated by plain film radiograph. In some cases, additional upper or lower GI contrast studies may be useful. Ultrasound may be useful in diagnosing some obstructive conditions where a mass may be involved such as intussusception. CT scans will show problems such as intussusceptions and enteric cysts causing obstruction but are not usually the first study of choice.
The differential diagnosis for a GI obstruction is large. Obstruction should not be considered a primary diagnosis, but rather the result of another diagnosis causing the obstruction. Once again, age at presentation helps to narrow the possibilities, many of which are exclusive to the first few weeks of life. Postoperative surgical adhesions still rank as one of the most common causes of obstruction in anyone with a prior abdominal surgical history. Other considerations include the location of the obstruction. Distal obstructions tend to cause significant abdominal distention while proximal obstructions may present with high-volume emesis and little or no abdominal distention. The color and frequency of emesis are helpful in narrowing down where an obstruction may have occurred. Moreover, the description and location of any overlying pain accompanied with a plain film radiographic may also point in the right direction early in the investigation.
Ischemia can occur from local mechanical issues such as twisting of the bowel to systemic functional conditions such as a low-flow state. It can be devastating once it begins because a vicious cycle may ensue. Bowel that has been compromised from low flow becomes more edematous and inflamed creating a third-spacing effect that draws in more fluid. As more fluid is drawn into the bowel wall, edema progresses, causing further mechanical compression of the vasculature and worsening ischemia. Coupled with the bacterial translocation and sepsis that often accompany a low-flow state, the ischemia can progress rapidly down a deteriorating route. Emergent intervention including aggressive fluid replacement is required. Failure to act quickly can lead to significant loss of bowel or death due to worsening acidosis, sepsis, and systemic circulatory collapse.
Perforation can result from obstruction, ischemia, or both. Distal colonic obstructions often lead to perforation of the cecum by the law of Laplace. Small bowel obstructions may lead to a perforation in a variety of locations proximally anywhere along the small bowel. Ischemic areas are especially susceptible to perforation due to weakened bowel wall strength. Other causes of perforation include trauma, foreign bodies, and ulceration (e.g., colonic ulceration due to acid production in a Meckel’s diverticulum). Visceral perforations occasionally wall themselves off, but not before significant contamination has occurred. The patient with a hollow viscus perforation may have impressive peritoneal signs on physical exam. Gastric perforations, which tend to have low bacterial counts, may release huge quantities of air into the peritoneum, but the abdominal examination may not be as impressive as seen with small bowel or colon perforations.
Most GI bleeding is usually slow, chronic, or both, can be treated medically or endoscopically, and therefore rarely requires emergent surgical exploration. However, entities such as Meckel’s diverticulum can result in massive bleeding that can best be managed surgically. Localization of any GI blood loss is critical before exploration is considered unless the patient is unstable. Most GI bleeds are localized through careful history and physical exam followed by endoscopy and imaging studies, as described in Chapter 6. For serious bleeding whose source remains elusive, exploring a GI tract through an open operation concurrently with luminal endoscopy by a gastroenterologist may be considered. Finally, emergent surgical exploration is reserved for situations where blood loss is high and standard diagnostic imaging modalities are either impossible or unsafe.
Neonatal gastric perforation can be spontaneous, ischemic, or traumatic. Nasogastric (NG) tube trauma is a common cause of iatrogenic perforation, especially in premature infants. The likelihood of this complication can be reduced using simple preventative means such as careful measurement and placement of an appropriate-sized NG tube. Other causes of iatrogenic perforations include barotrauma from bag-mask ventilation or other forms of positive pressure ventilation. Patients with a tracheoesophageal fistula are at particular risk and may require emergent decompression with a surgical G-tube before the fistula is dealt with. Ischemic perforation can result from birth asphyxia, sepsis, or necrotizing enterocolitis (NEC). The mechanisms may include impaired mucosal defenses secondary to poor perfusion or frank infarction of the gastric wall. Spontaneous perforation without obvious cause may happen, and usually occurs in newborns with no traumatic or ischemic histories. Some of these babies are premature while others are simply small for gestation age.
A change in abdominal examination is common for these children when a gastric perforation occurs. The abdominal exam may only demonstrate a modest degree of tenderness, because the spilled gastric contents are not as irritating to the peritoneum as contents spilled from perforations in the large or small intestine. However, the volume of air released can be impressive. Plain film radiography often shows massive pneumoperitoneum. An excessively large volume of intra-abdominal air is a clue that suggests that a perforation may be gastric.
Surgical management depends on the cause. Traumatic and spontaneous perforations do well with primary repair only. Ischemic perforations require debridement and resection of the devitalized tissues.
Gastric volvulus is a rare form of a proximal obstruction in children. Two variants of gastric volvulus exist: organoaxial and mesentericoaxial. Gastric volvulus is associated with congenital deficiencies in stomach fixation. Typically, the stomach is tethered by the gastrohepatic, gastrosplenic, and gastrophrenic ligaments as well as the retroperitoneal duodenum. Anomalies of the gastrohepatic and gastrosplenic ligaments allow for an organoaxial volvulus as the stomach rotates about its longitudinal axis. Abnormalities of the gastrophrenic and duodenal attachments may create a mesentericoaxial volvulus.
Both acute and chronic forms of volvulus may occur, with acute being significantly more common. The typical patient presents with severe epigastric pain. Patients may also have significant retching without emesis. The abdominal exam can be quite variable but gastric distention may be severe. A tender abdomen with peritoneal signs may suggest ischemia or perforation and emergent exploration is required. The diagnosis is suspected if a NG tube cannot be passed.
Contrast radiologic evaluation may demonstrate significant gastric distention or the contrast may even fail to progress into the stomach and simply be retained in the esophagus because of an obstruction at the level of the GE junction. The organoaxial volvulus is the more common of the two types, but both can be hard to diagnose without a high degree of clinical suspicion.
Emergent exploration is indicated in the acute setting to reduce the risk of ischemia. Operative treatment begins with reduction and may need to include resection of ischemic areas. Perforations are usually closed primarily whenever possible. From a historical standpoint, a gastrostomy had been advocated to help reduce the presumed risk of a subsequent volvulus but actual clinical data have not confirmed that placing a gastrostomy makes any difference in the recurrence rate. It is generally accepted that recurrent gastric volvulus should be treated with a gastropexy.
HPS is an acquired condition that results in a thickened pyloric muscle layer that obstructs the gastric outlet. The incidence of HPS is around 0.86–3.96 per 1000 live births and is typically seen in infants between 3 and 6 weeks of age.1 There is a significant male predominance, with a male to female ratio of 4:1.
Infants with HPS typically develop progressively worsening emesis after the first few weeks of life. Initially, symptoms are intermittent, which may lead to an early misdiagnosis of gastroesophageal reflux or formula intolerance. The diagnosis becomes clear when vomiting becomes more severe and is noted to be non-bilious and projectile. Significant dehydration occurs, and the loss of gastric HCl results in hypochloremic, hypokalemic metabolic alkalosis. In severe cases, hypoglycemia can precipitate seizures. Unconjugated hyperbilirubinemia is common. The hyperbilirubinemia often gets the attention of the physician, but is transient and does not warrant further attention if it resolves after the stenosis is repaired.
Physical examination typically reveals an infant with significant dehydration including sunken eyes and fontanelles, decreased skin turgor, and dry mucus membranes. The classic finding on abdominal exam is the “olive sign” in the epigastrium. The olive is actually the thickened pylorus that can be easily palpated in the flaccid abdomen, but may be very difficult to find in the irritable or inconsolable infant. The exam is performed by placing two or three fingers lubricated with soap or lubricating jelly on the upper abdomen, slightly to the right of midline. The area is carefully palpated for a small oval mass while sliding the fingers inferiorly. A positive exam is 97% accurate and, if present, no further diagnostic studies are required.2 However, the exam may be very difficult to perform in the irritable child, especially when the stomach is full of fluid. In this situation, consoling the child and examining when the stomach is empty create the best opportunity for palpating the pyloric mass. NG suction to empty the stomach or examining the child immediately after vomiting will improve the likelihood of a successful exam. After the NG suctioning has been completed, a small amount of sugar water can be given to the child by bottle while the examiner attempts to locate the pylorus. Allowing the child to have the sugar water is a very effective method and any volume consumed by the child can be easily removed by the NG tube once the diagnosis is confirmed.
Unfortunately, the art of the pyloric exam seems to be fading. More and more physicians immediately opt for an ultrasound, which is a very accurate method for diagnosis of HPS. Ultrasound is an additional expense and may not be readily available at all times of day or in all locations. However, it is a reliable diagnostic tool for the infants whose physical exam is indeterminate. Ultrasound-measured pyloric length of >17 mm or a muscle layer thickness of >4 mm has positive predictive value of 90% for infants 4 weeks of age or greater.3 The barium upper GI series, once popular for diagnosing HPS, is used with much less frequency now, as it is notoriously inaccurate. Barium studies may still have utility in equivocal cases, but should be considered less reliable than either physical exam or ultrasound (see Figure 9–8).
Proper preoperative resuscitation is critical before operative intervention is undertaken. Electrolyte disturbances can be severe and fatalities due to arrhythmias can occur if these infants are placed under anesthesia prior to replenishment of fluid and electrolytes. The resuscitation can take anywhere from 12 to 72 hours and electrolytes should be rechecked periodically. It cannot be overemphasized that there is no emergency to rush the child with HPS to the operating room. Severely dehydrated infants should receive repeated boluses of IV NS (20 mL/kg each) until vital signs are stabilized and good urine output is confirmed. After the emergent volume resuscitation is completed, 5% dextrose with 0.45% NaCl (1/2 normal) should be run at 1.5 times the calculated maintenance rate. Potassium should be added once urine output is achieved, using 20–40 mEq potassium/L of solution. Part of the electrolyte disturbance in these patients is a significant hypokalemia. Serum potassium measurements underestimate the total body potassium deficit because the metabolic alkalosis will shift extracellular potassium intracellularly. All electrolyte derangements can be corrected with proper fluid replacement. Periodic checks of the electrolytes should be done during fluid resuscitation, in anticipation of performing surgery once the serum chloride is normalized and the serum bicarbonate is <30.
The classic operation for HPS is a pyloromyotomy (Figure 21–1). In open surgery, the procedure can be done through a right upper quadrant or an umbilical incision. Both approaches have their advocates and the choice between the two techniques was hotly debated among pediatric surgeons in the late 1990s, with no resolution. However, shortly after 2000, minimally invasive surgery (MIS) gained enormous popularity and the laparoscopic pyloromyotomy quickly replacing both open methods. Regardless of the approach, the key to the operation is a complete pyloromyotomy without perforation of the underlying mucosa. A longitudinal incision is made in the serosa of the pylorus all the way from antrum to pyloric–duodenal junction. Once the serosa is split, blunt spreading of the hypertrophic muscle is performed using a Ramstedt spreader. Care must be taken to avoid perforation of the mucosa, which is more likely to occur at the duodenal end of the myotomy. Fortunately, the risk of perforation is fairly low, with a rate of <3% in most series.4 The pyloromyotomy needs to be long enough such that each half of the opened pyloric ring moves independently.
Feedings can be started relatively soon after the procedure. No feeding regimen has been shown to be superior over any other. There is significant disagreement over the ideal feeding regimen, with somewhat complicated protocols still in use. Recent studies indicate that feeding ad libitum within a couple of hours after surgery is tolerated just as well as the progressive feeding regimens, with multiple concentration and volume changes, that have been popular for decades.5 The ad libitum method has the advantage of being much simpler to explain to residents, families, and staff.
Occasional emesis often occurs in the early postoperative period regardless of the chosen feeding regimen, but is not usually a cause for alarm. Persistent, high-volume emesis suggests an incomplete myotomy, which requires a return to the OR for completion. Intraoperative mucosal perforations recognized at the time of surgery can lead to peritonitis and sepsis. Initial signs and symptoms include abdominal tenderness, distention, and acidosis. This complication can be confirmed by contrast radiography and should be followed by emergent reexploration when suspected. Fortunately, both incomplete myotomy and perforation are rare. The majority of patients go home within 24 hours following the surgery.
Malrotation with midgut volvulus is a true surgical emergency. Once established, irreversible ischemia to the midgut can occur in just a few hours. Every physician must have malrotation in their differential diagnosis when evaluating children with sudden obstructive symptoms. Bilious emesis, the hallmark sign of malrotation, is assumed to be malrotation until proven otherwise.
Malrotation occurs due to a failure of the normal rotation and fixation of the bowel in the first 3 months of gestation. In the normal rotational process, the midgut herniates into the yolk sac during the fifth week of gestation. The superior mesenteric artery (SMA) serves as the blood supply for the midgut and is the main axis of its normal rotation. The rotation occurs in a counterclockwise direction. Normally, after 270˚ of counterclockwise rotation, the duodenojejunal region is tethered to the retroperitoneum in the expected “C-loop” orientation, with jejunum emerging into the peritoneum at the ligament of Treitz in the left upper quadrant. Concurrently, the ileocolic segment also rotates around the SMA, bringing the cecum down to the right lower quadrant. The normal mesentery of the midgut is tethered firmly along a broad retroperitoneal attachment from the ligament of Treitz to the cecum. For this reason, volvulus rarely happens in the properly rotated bowel.