GASTROENTEROLOGY

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COMMON GASTROINTESTINAL PROBLEMS AND EMERGENCIES IN NEONATES AND CHILDREN

The large number of infants and children who are seen in physicians ofces, urgent care centers, and hospital emergency rooms for signs and symptoms related to an abdominal etiology attests to the fact that this is an exceedingly common problem. Among this large group of patients is a signicant number that have serious surgical diagnoses. This includes a number of disorders, many of which are uncommon. In addition, there are many common and uncommon neonatal surgical problems that are seen in the newborn nursery and are referred to a neonatal intensive care unit and pediatric surgical specialist. This article concentrates on a few of the most common problems that we encounter in our practice and discusses a few of the potentially devastating congenital anomalies that may appear later in infancy and childhood. Our intent is to give a more in-depth discussion of each of these topics and to have the points we make more easily incorporated into daily practice. Much of the material comes from the our experience but is also based on recent literature. Where controversy exists, we endeavor to include the best evidence-based practices.

APPENDICITIS Background Since Fitz described appendicitis in 1886 [1] and McBurney delivered his classic paper in 1889 [2] describing McBurneys Point, the diagnosis of

From the Department of Surgery, SUNY Upstate Medical University, Syracuse, New York (JMH); and the Department of Surgery, Division of Pediatric Surgery, SUNY Upstate Medical University, Syracuse, New York (TB, LN, MR) ....................................................................................................................................................

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appendicitis has remained controversial. In our experience, approximately 25% of the time the diagnosis is obvious and straightforward. In roughly 25% of patients, the diagnosis requires a careful history and physical examination and some basic laboratory studies. In the last approximately 50% of patients, the diagnosis can be difcult to make accurately. This last group includes the very young (ie, those under 5 years old); patients who have been symptomatic for more than 2 or 3 days; adolescent girls aged 13 to 18; and a group of patients in whom the history, physical examination, and laboratory studies do not t the usual picture of appendicitis. Imaging studies are necessary in this last group of 50% of cases, and exploratory laparotomy or diagnostic laparoscopy may also be required to make an accurate diagnosis. History and Physical Examination Symptoms of appendicitis usually begin with abdominal pain, often in the periumbilical area. Classically, after 6 to 18 hours from onset, the pain migrates to McBurneys point, dened as the point two thirds of the distance from the umbilicus along a straight line toward the anterior superior iliac spine of the pelvis. In most cases, the pain steadily worsens until the appendix perforates. At that time, the localized pain may decrease, but the more generalized pain of peritonitis takes over. Anorexia is the next most common symptom, occurring in about 95% of patients. Nausea is seen in approximately 75% of cases, and vomiting is seen in 60% to 70% of patients. Diarrhea, or more accurately tenesmus, may occur but is usually seen late in the clinical course of appendicitis when the sigmoid colon becomes irritated by a severely inamed or perforated appendix. About 75% of patients have a low-grade fever around 38C (100.4F), but a higher fever or the absence of fever should not eliminate the diagnosis of appendicitis [3]. The physical examination to rule in or rule out appendicitis begins when the patient walks into the providers ofce or emergency department. Many patients exhibiting this type of abdominal symptomatology walk in a somewhat bent over (exed abdomen) or guarded fashion, giving the provider valuable information regarding the potential for peritoneal irritation. We generally begin the abdominal portion of the examination by asking the patient to cough. If this maneuver causes pain in the right lower quadrant, this is considered to be a positive sign for peritoneal irritation. The rapid release of the hand on the abdomen after deep palpation as a test for rebound tenderness is almost uniformly worthless in children because virtually all children respond by jumping with this maneuver. Palpating the abdomen softly allows the provider to compare the right- and left-sided rectus abdominus muscles and lets the evaluator know whether or not there is rectus rigidity. The location of the maximal tenderness at McBurneys point is helpful. Rovsings sign, or referred tenderness from the left lower quadrant to the right lower quadrant during palpation, is a signicant sign of appendicitis. The psoas sign, elicited by

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extending the hip posteriorly with the patient lying prone, and the obturator sign, elicited by abducting the right hip with the patient lying supine, have not been helpful. Auscultation of bowel sounds is generally not considered to be helpful in examining a child for potential appendicitis because bowel sounds tend to be hypoactive or absent once peritonitis occurs after appendiceal perforation. The rectal examination in a case of suspected appendicitis does not provide much useful information unless there is a pelvic abscess present. Because other diagnoses besides appendicitis exist in children who may present with these signs and symptoms (eg, severe constipation), a rectal examination should be performed, preferably only once by the senior-most provider evaluating the patient.

Laboratory Investigation There is no denitive laboratory test for accurately diagnosing appendicitis. When evaluating these patients, we order only a complete blood count (CBC) and a urinalysis. An elevated white blood cell (WBC) count, particularly with a bandemia, helps conrm the diagnosis but by itself is not considered to be diagnostic. In these cases we expect to see a WBC count in the range of 12,000 to 16,000, but a very high WBC count does not exclude the diagnosis. In addition, a normal WBC count may not exclude the diagnosis of appendicitis. Consistently, 4% of our patients with appendicitis have a normal WBC count and differential and are afebrile upon presentation. Upward of 20% to 25% of patients have a normal WBC count regardless of febrile status [3]. The urinalysis is perfumed to rule out the potential diagnosis of urinary tract disease. The nding of a few WBCs or red blood cells (RBCs) in the urine, however, does not rule out a case of appendicitis. Occasionally, the appendix abuts the right ureter or the dome of the bladder; WBCs or RBCs in the urine are then more likely but are usually found only in small numbers. C-reactive protein has become popular in helping to rule in or rule out appendicitis, particularly in Europe, but over the years studies have not demonstrated this test to be more predictive than the WBC count [4].

Imaging Studies In patients where the history, physical examination, and laboratory ndings do not lead to the diagnosis of appendicitis, imaging studies are indicated. A plain lm radiograph of the abdomen or an abdominal series may reveal a fecalith, and in a patient with signicant right lower quadrant tenderness on physical examination, this is generally considered adequate data to make the correct diagnosis. However, a fecalith is present in only approximately 10% of the cases, so an ultrasound or a CT scan is necessary. This has been an area of controversy for the last 5 to 10 years.

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There are proponents on both sides of the ultrasound versus CT evaluation discussion, and both groups claim to have a near 100% accuracy in making the diagnosis [5,6]. Ultrasound evaluation tends to be an operator-dependent modality. Our experience has been that it is our rst choice in the thin patient, particularly within the rst 12 to 18 hours of the presenting illness. A skilled technician or radiologist can accurately diagnose appendicitis with an ultrasound evaluation in roughly 50% of cases [5]. In the evaluation of a more obese child, a CT scan is the preferred choice [5]. This is performed after the administration of oral or rectal iodinated contrast so that the gastrointestinal (GI) tract (ileum, cecum, and potentially the appendix) in the right lower quadrant is lled with the radio-opaque contrast agent. One prospective study of 100 patients demonstrated up to a 98% accuracy rate using this method of evaluation [6]. The use of intravenous (IV) contrast material in making the diagnosis of appendicitis remains controversial. Recent studies have shown that IV contrast helps to better delineate an inamed appendix and the periappendiceal inammatory response [7]. A CT scan performed too early in the course of the illness leads to a false-negative result. This is a signicant problem because we are seeing more patients in our emergency department in whom a CT scan has been performed before the patient is evaluated by a resident or attending surgeon. Our recommendations for imaging studies in the diagnosis of appendicitis are to perform them in a systematic fashion. A resident or attending surgeon should evaluate the patient rst; then, if it is felt that on the basis of the history, physical examination, and laboratory studies the patient has appendicitis, the patient should go directly to the operating room without an imaging study [6]. In the equivocal patient who is not obese and who is within the rst 24 hours of the illness, an ultrasound study should be performed to rule in or rule out appendicitis. If the ultrasound is positive, with a noncompressible, nonperistaltic tubular structure 6 mm or greater in diameter, the patient goes to the operating room for an exploratory laparotomy to evaluate the appendix. If the ultrasound is negative, without visualization of the appendix, or equivocal, we proceed with a CT scan. Whether or not this is performed with oral or rectal contrast depends upon the standard protocol for the particular institution in which the patient is being evaluated. We almost always use the oral route, which is less invasive, but the patient must be able to tolerate the contrast without vomiting. Although the positive predictive value (PPV) for the oral route has been reported to be 94%, the rectal route using a limited right lower quadrant CT scan has a PPV as high as 98% [8,9]. If the result is positive, showing a dilated appendix and signs of inammation in the area (Fig. 1), the patient is taken to the operating room for surgical evaluation. If the CT results are negative, the patient may be admitted for observation or discharged at the discretion of the examiner and parents with instructions for follow-up if symptoms worsen. A prospective study using these criteria has yielded good results with an accuracy rate of correct diagnosis of 94% [6].

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FIGURE 1. CT scan of the abdomen/pelvis in a patient with acute appendicitis. Note the circular object in the right paracolic gutter (white arrowhead), with the thickened wall of the cecum and associated mesenteric fat stranding. The radio-opaque density within the lumen of the appendix is consistent with a fecalith.

Perforated Appendicitis The perforation rate in cases of appendicitis has varied from 10% to 85% depending upon age, gender, and whether or not the institution where the patient is evaluated is located in the inner city. In most major hospital centers, the incidence of perforation in the general pediatric population ranges from 20% to 40%. These patients often present as being dehydrated and toxic-appearing with obvious physical signs of peritonitis. When these patients present, they should be immediately uid resuscitated and treated with antibiotics before being taken to the operating room. There is a small subgroup of patients with appendiceal perforations in whom the diagnosis is missed or who do not present for medical evaluation until late in the course of the illness. In this type of patient, who may have been ill for a period of 7 to 10 days, radiographic studies often reveal a walled-off abscess or phlegmon in the right lower quadrant. These patients can often be treated medically and have their abscesses drained percutaneously by an interventional radiologist. When the patient stabilizes and recovers, they are generally sent home. After a period of 6 weeks, we opt to perform an interval appendectomy. Surgery At the conclusion of a careful history and physical examination, laboratory studies, and imaging studies, there is a small group of patients in

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whom the diagnosis is unclear. A diagnostic laparoscopy is a reasonable procedure in this group of patients, and during the procedure the appendix should be resected, regardless of its appearance. Our experience has been that frequently the appendix is clearly inamed on microscopic examination when grossly, via laparoscopy, it appears normal. Whether a routine appendectomy should be performed in the traditional open manner or via laparoscopy is a point of debate because there are good studies that show contradictory results [10,11]. Our experience has been that in obese patients, who comprise a larger percentage of our population every year, the laparoscopic approach seems to have an advantage, yielding decreased operating time and a shorter hospital stay. In the thin, young child, there does not seem to be an advantage using either technique. PYLORIC STENOSIS Background Vomiting is a common problem in infancy and childhood. It is therefore essential to differentiate among the various etiologies of vomiting, including that caused by a nonanatomic etiology, that caused by an anatomic abnormality, or cases that require surgical attention. Most vomiting caused by an anatomic or mechanical obstruction is associated with green or bilious emesis. The most common etiology of anatomic nonbilious vomiting in infancy is infantile hypertrophic pyloric stenosis. Infantile hypertrophic pyloric stenosis is the progressive elongation and thickening of the circular layer of the antral-pyloric muscle resulting in progressive gastric outlet obstruction. Pyloric stenosis occurs in 3 of 1000 live births [12]. The reported male-to-female ratio ranges from 2:1 to 5:1 [13]. Although the etiology of pyloric stenosis is unclear, proposed etiologies include gastric hyperacidity leading to muscle spasm and hypertrophy; abnormal pyloric innervation; and abnormal local concentrations of vasoactive intestinal peptide, nitric oxide, and substance P. None of these etiologies has been proven or can adequately explain the favorable response to surgery [14]. History and Physical Examination Pyloric stenosis usually presents between the third and sixth week of life and is rarely present at birth. Infants usually present with progressive nonbilious vomiting. This may increase to what is typically described as being forceful or projectile vomiting by the parent. Occasionally, the vomiting can be of an acute onset. It is not uncommon for infants who present with this symptom to be initially diagnosed as having gastroesophageal reux. Treatment of these infants with thickened formulas or prokinetic agents frequently exacerbates their symptoms. Infants may

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have had multiple formula changes in the belief that the vomiting is due to a milk protein allergy. Although vomiting is a typically a part of the milk protein allergy symptom complex, diarrhea and blood in the stools are more frequently associated with this entity. Long-standing vomiting may be associated with coffee-ground emesis due to a secondary gastritis. If the vomiting is of signicant duration, there is associated weight loss, a key sign that may help differentiate pyloric stenosis from gastroesophageal reux or milk protein allergy. Physical examination may reveal a normal, healthy-appearing infant or an infant who is lethargic with signs of dehydration. If the vomiting is long standing, the infant may have the appearance of a child with failure to thrive. Generally, from 5% to 10% of infants with pyloric stenosis have an indirect hyperbilirubinemia that resolves after surgical correction. The diagnosis of pyloric stenosis can be made on physical examination. Two signs are considered to be pathognomonic: the gastric wave and a palpable pyloric olive, dened as an olive-sized horizontal mass representing the hypertrophic pyloric muscle in the epigastrium. Usually, the presence of a gastric wave and a palpable olive cannot be demonstrated during the same examination in a child because they have conicting requirements for their demonstration. The gastric wave requires that the stomach be full. Visualization of the wave requires patience and a restful infant. Frequently, it is easier to see the wave by viewing the childs abdomen tangentially. The wave appears as a bulging mass that traverses the infants epigastrium from the left ank to just right of the midline. Palpation of the pyloric olive requires the infants stomach to be empty and the abdominal wall to be relaxed. By standing on the right side of the infant, the evaluating provider can grasp the legs with the left hand and ex the legs at the hips, thus relaxing the abdominal wall. Sometimes the administration of an oral glucose water solution may help to settle the infant to facilitate this maneuver. With the providers right hand starting underneath the liver edge, one can palpate the abdomen deeply and sweep inferiorly. The pyloric olive can then be appreciated as the providers ngers trap the hypertrophic muscle along the back. The olive can be palpated and visualized as the hypertrophic pylorus pops as the ngers roll over the olive. Imaging Studies The radiologic conrmation of pyloric stenosis is based upon the upper GI series and, more recently, on the pyloric ultrasound evaluation. Typically, the upper GI study shows delayed or no gastric emptying, an elongated pyloric channel with a string sign (a barium-lined elongated and narrowed pyloric channel) (Fig. 2), and an indentation of the antrum by the hypertrophic pyloric muscle. More recently, the pyloric ultrasound has been used in the evaluation of pyloric stenosis. Ultrasound has an advantage over the upper GI series because there is no radiation exposure to the infant and no barium is present in the stomach before the induction of anesthesia.

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FIGURE 2. Barium upper GI series in an infant with pyloric stenosis, demonstrating the classic string sign with a wisp of contrast passing through the hypertrophic pylorus (white arrowhead).

Sonography has been shown to be highly sensitive (90% to 96%) and specic (100%) for the diagnosis of pyloric stenosis [15,16]. Using the pyloric ultrasound study, two views are paramount: a transverse view that looks like a bulls-eye to measure the pyloric muscle thickness and a longitudinal view to measure the muscle wall thickness and the length of the pyloric channel. The criteria for the diagnosis of hypertrophic pyloric stenosis vary in different reports. The generally accepted measurement criteria are a muscle thickness of 4 mm and a pyloric channel length of 17 mm (range 34 mm and 1617 mm, respectively) [17,18]. The disadvantages of the ultrasound diagnosis of pyloric stenosis include a dependence upon the skill of the ultrasound technician, and, in small infants, the measurement criteria may not be met because of the infants size. Sonography and contrast radiography should not be viewed as competing diagnostic modalities but rather as complementary techniques. Physical examination and radiologic conrmation may not be diagnostic early in the evolution of pyloric stenosis and may need to be repeated 3 to 7 days after the initial presentation.

Fluids and Electrolytes Once the diagnosis of pyloric stenosis is suspected, an electrolyte panel should be obtained, and an IV infusion should be started. The infant

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should be assumed to be dehydrated in these cases, and an infusion of a 5% glucose solution in a half-normal saline solution with the addition of 10 mEq of potassium chloride per liter begun at a rate of 150 mL/kg/d [19]. If the infant seems to be severely dehydrated, a bolus of 10 to 20 mL/kg of NS may be required. The typical IV solution recommended for infants of this age, a 5% glucose solution in a quarter-normal saline solution, should be avoided because this usually worsens any underlying metabolic derangement despite attempts at rehydration. Because prolonged vomiting of gastric contents leads to the loss of hydrogen and chloride ions, the typical metabolic abnormality seen is a hypochloremic metabolic alkalosis, evidenced by high serum bicarbonate and low chloride levels. The metabolic abnormality should be corrected quickly to ensure a serum chloride level above 95 mEq/dL before surgery. In severe cases, this abnormality may take over 24 hours to correct.

Surgery Ramstedt [20] rst described the basic principles of surgical correction of pyloric stenosis in 1912. The procedure involves the longitudinal splitting of the hypertrophic muscle down to the gastric mucosa without reapproximation of the muscle (Fig. 3). The basic operation has not changed since its introduction. Over the years, several surgical approaches to the pylorus have evolved. The classical approach is a transverse right upper quadrant incision. Tan and Bianchi [21] introduced a circumumbilical incision for pyloromyotomy in 1986. This technique has the advantage of a better cosmetic appearance, leaving an almost undetectable scar for the infant. The mean operating time is slightly longer for the periumbilical incision than the right upper quadrant incision, reecting the increased difculty of delivering the pylorus through this incision. Some series report a higher rate of mucosal perforation and wound infection using the periumbilical approach [22], whereas others report complication rates similar to the classical approach [23]. Recently, proponents of minimal access surgery have advocated for a laparoscopic approach for pyloromyotomy [24]. This approach has the advantage of a superior cosmetic appearance and a lower wound infection rate. There is a debate between the open and laparoscopic pyloromyotomy approaches that centers on a higher mucosal perforation rate, particularly during the surgeons initial experience with this procedure. Recently, Hall [25] reported a meta-analysis of 345 infants who underwent open pyloromyotomy versus 230 infants who underwent the laparoscopic procedure. There were ve mucosal perforations in the open pyloromyotomy group versus eight mucosal perforations in the laparoscopic group [25]. As more pediatric surgeons are trained in advanced laparoscopic surgery, there will more than likely be a gradual transition from the open procedure to the laparoscopic pyloromyotomy. In Halls meta-analysis, the average operating time for both approaches was 31 minutes [25].

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FIGURE 3. Intraoperative photographs of a pyloromyotomy. The hypertrophied pylorus is delivered up into the abdominal wound (A), and the muscular wall is divided longitudinally and spread to expose the intact mucosa (B).

Pyloromyotomy universally relieves the gastric outlet obstruction. Parents should be warned that their infant may initially vomit after surgery and that this is not unexpected. Feedings are usually begun 4 to 6 hours after surgery, then subsequently every 3 to 4 hours. Most infants are ready for discharge from the hospital 24 hours after surgery. After discharge, the infant usually has an increased appetite until they are back on their normal growth curve, which usually takes 3 to 4 weeks. There have been no known long-term consequences of pyloromyotomy reported in the literature. The most common operative complications of this procedure include wound infection, a mucosal perforation rate of 0.08% to 4% [26], and an inadequate pyloromyotomy. Unrecognized mucosal perforation leads to peritonitis

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and sepsis, and inadequate pyloromyotomy leads to persistent postoperative emesis. INTUSSUSCEPTION Background Intussusception, the telescoping of a proximal limb of intestine (the intussusceptum) into the adjacent distal intestine (intussuscipiens) (Fig. 4), is the most common cause of intestinal obstruction between 3 months and 6 years of age, with an incidence of 1 to 4 cases per 1000 live births [27,28]. The pediatric clinical presentation of intussusception is distinctly different from that seen in adults. Intussusception in children involves the terminal ileum in 90% of cases, including ileocolic, ileocecal, and ileoileocolic forms, whereas small bowel intussusception is more common in adults (60% of cases) [2931]. Furthermore, pathologic lesions serve as the lead point in <10% of pediatric cases, whereas adult intussusception is attributable to a denable lesion in 90% of patients [2932]. These distinctions make the diagnosis and management of intussusception in children more different than in adults. The pathologic process of intussusception involves the compression of the invaginated mesentery, resulting in lymphatic obstruction and venous congestion. Subsequent bowel wall swelling with mucus overproduction and ischemia with resultant mucosal bleeding produce the classic red currant jelly stools that are classically seen with intussusception; currant jelly stools are present in 60% of cases of intussusception [33].

FIGURE 4. Photograph of a small bowel intussusception, with the proximal intussusceptum (white arrow) pulled into the lumen of the distal intussuscipiens (white arrowhead).

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History and Physical Examination The classic presentation of intussusception begins with a previously well-appearing child who suffers a sudden onset of episodic crampy or colicky pain accompanied by exed limbs and straining. Episodes of pain generally occur 10 to 20 minutes apart and often last for several minutes. The infant may seem asymptomatic between episodes. These painful episodes gradually become more frequent and are often accompanied by fever, lethargy, bilious emesis, dehydration, and currant jelly stools. The classic triad of colicky abdominal pain, vomiting, and currant stools is present in 21% of cases [34]. Physical examination of the child may reveal a soft, nontender abdomen early in the course of the illness, although a palpable, vertically oriented sausage-shaped mass in the right upper quadrant may be present in up to 50% of cases [35]. Imaging Studies The value of conrmatory radiographic studies in the diagnosis and treatment of intussusception has been thoroughly reviewed. Plain abdominal lms are often the initial study, and suggestive ndings include the meniscus sign (leading edge of the intussusceptum outlined by adjacent colonic gas), the target sign (mass in the right upper quadrant), and the absence of cecal gas and stool in the right lower quadrant. Plain radiographs have been shown to be diagnostic in up to 45% of children with intussusception [36]. Barium enema has historically been the traditional study of choice, with diagnostic sensitivity and specicity approaching 100%. Evidence of a lling defect at the apex of the column of barium, with tracking around the invaginating intestine to produce a coiled-spring appearance, is diagnostic for intussusception. The therapeutic value of a barium enema is also well documented, with reduction of the intussusception seen in approximately 70% of the cases [37]. If an obstructive pattern exists on plain radiographs, reduction of the intussusception via barium enema is unlikely. Technologic advances combined with trends toward radiation reduction in the pediatric population have moved diagnostic ultrasound to the forefront at many centers, with accuracy rates comparable to that of barium contrast enemas [38,39]. Ultrasounddirected pneumatic reduction with an air enema has been shown to have greater success rates as compared with barium enema or saline hydrostatic reduction (90% compared with 70% and 67%, respectively) and generally fewer complications [37]. Surgery In circumstances where hydrostatic or pneumatic reduction are unsuccessful or contraindicated (eg, hemodynamically unstable patients, signs of peritonitis on physical examination), surgical intervention is

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required. Initial intraoperative manual reduction is attempted and is usually successful. The portion of nonviable or irreducible intestine is resected, and an end-to-end primary anastomosis is performed. An incidental appendectomy is usually performed during this procedure. Laparoscopy is gaining favor, particularly in cases of uncertain or failed reduction by conservative methods [40], and has demonstrated successful reduction in up to 65% of cases refractory to enema therapy [41]. INTESTINAL MALROTATION Background Intestinal malrotation describes an interruption of the typical intestinal rotation and xation during fetal development with arrest of the process at various stages producing clinically distinct acute or chronic presentations. Although case reports date back to before 1900, Ladd [42] published a seminal article in 1936 on the treatment of malrotation in which he described the surgical procedure that carries his name and remains the standard of care for the operative correction of intestinal malrotation. The incidence of intestinal malrotation in the United States is approximately 1 in 500 live births [43]; 40% of these infants are diagnosed during the rst week of life, and 75% are diagnosed by 1 year of age. The male-to-female ratio is 2:1 up to 1 year of age; prevalence is equal thereafter. Mortality is highest with a younger presentation, with mortality rates ranging from 2% to 24% when identied in infancy. The gestational defect of intestinal malrotation involves the normal embryologic extracoelomic herniation and rotation of the intestinal tract around the superior mesenteric artery (SMA). This rotation occurs simultaneously with a profound lengthening of the intestinal tract. During the remainder of gestation, the cecum migrates from the right of the SMA down to the familiar right lower quadrant of the abdomen. This combination of rotation, intestinal lengthening, and cecal migration to the right lower quadrant results in a broad mesenteric root, running from the left upper quadrant to the right lower quadrant of the abdomen, and containing all of the vasculature of the intestinal tract from the ligament of Treitz to the midtransverse colon. Defects at various stages in this sequence can produce different clinical presentations, which have been broadly classied into four distinct entities: acute or chronic midgut volvulus and acute or chronic duodenal obstruction. Volvulus Acute midgut volvulus usually presents in the rst year of life. The primary symptom is sudden onset of bilious emesis and abdominal pain. Because this syndrome entails the vascular compromise of the SMA, the

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entire small bowel is at risk for infarction without prompt intervention. Furthermore, the relatively late appearance of additional diagnostic signs, such as abdominal distension, rectal bleeding, hematemesis, and abdominal tenderness, makes a high index of suspicion critical for successful management of these infants. The presentation of chronic midgut volvulus, resulting from an intermittent or partial twisting producing venous obstruction, is often more subtle. The infant may tolerate feedings and gain weight initially. A history of occasional abdominal pain and malabsorption may be the only hints toward diagnosis of this condition. Furthermore, the physical examination may be benign if the infant or child presents during an unobstructed interval. Examination during a symptomatic episode is essentially identical to that of an acute midgut volvulus, with abdominal distension, tenderness, and guarding. Other features of this syndrome can include recurrent constipation alternating with diarrhea, intolerance to solid foods, and gastroesophageal reux [44].

Duodenal Obstruction Acute duodenal obstruction results from the compression or kinking of the duodenum by isolated bands of peritoneum under tension, or Ladds bands. The typical presentation is an infant with forceful bilious vomiting. On examination, gastric waves may be present, much like that seen in the case of pyloric stenosis, and peritonitis and shock are present only in rare circumstances with coincident downstream volvulus. Intermittent bilious vomiting with pain is the most common presenting complaint with chronic duodenal obstruction from a partially occlusive Ladds band. Physical examination is often unimpressive, and diagnosis is reliant upon a high index of suspicion and radiographic studies. Depending upon the frequency of emesis, diagnosis can range from during infancy to school-aged children.

Imaging Studies Radiographic examination is the hallmark of diagnosis in intestinal malrotation. Abdominal plain lms and CT scanning have shown limited effectiveness in identifying malrotation. However, the upper GI series and the contrast enema are valuable, and recent studies involving ultrasound show promise [45,46]. The upper GI series is the gold standard in stable patients and rules out malrotation if the duodenal C-loop crosses to the left of the midline at a level greater or equal to the pylorus (Fig. 5). A contrast column that ends abruptly or tapers in a corkscrew fashion is suspicious for midgut volvulus. In the case of contrast enema, a normally placed cecum in the right lower quadrant substantially reduces, but does not rule out, a possible intestinal malrotation.

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FIGURE 5. Barium upper GI series in an infant with intestinal malrotation in which the duodenum fails to cross the midline from the infants right to left and all of the opacied small intestine resides in the right hemiabdomen.

Surgery Medical care is directed toward the stabilization of the patient in preparation for surgical correction. Nasogastric decompression, IV resuscitation, and correction of electrolyte abnormalities should be among the rst interventions. Evaluation by a pediatric surgeon in unstable patients should not be delayed for conrmatory contrast studies. The steps of surgical correction, known collectively as the Ladd procedure, entail the derotation of any volvulus, division of mesenteric bands, placement of the small bowel in the right hemiabdomen and large bowel to the left, appendectomy, and resection of any nonviable loops of small bowel. MECKELS DIVERTICULUM Background Meckels diverticulum, named for the German comparative anatomist who rst described these small bowel diverticula in 1809, results from an incomplete obliteration of the fetal omphalomesenteric or vitelline duct. During the eighth week of gestation, the vitelline duct, a communication with the yolk sac, involutes as the placenta replaces the yolk sac as the source of fetal nutrition. The failure of this vitelline duct obliteration can result in several anomalies, including omphalomesenteric stulae, enterocysts, brous bands connecting the small intestine to the umbilicus, or a Meckels diverticulum. Meckels diverticulum, which accounts for 90% of

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vitelline duct anomalies [47], is a true diverticulum composed of all layers of the normal intestinal wall. Although their position along the intestinal tract is variable, most Meckels diverticula are found within 100 cm of the ileocecal valve. The average length is 3 cm [48], and up to 60% contain heterotopic mucosa, the most common being gastric mucosa (60%), pancreatic tissue (16%), jejunal mucosa (2%), or Brunners glands (2%) [49]. Meckels diverticulum is considered to be the most common congential GI tract anomaly, present in up to 2% of the population [50], with a male-to-female ratio of 3:2. Meckels diverticulum has been associated with several other anomalies, including congenital cardiac malformations, anorectal atresia, exophthalmos, cleft palate, annular pancreas, and central nervous system malformations [51]. Complications of Meckels diverticulum, estimated at 4% lifetime [52], are most commonly the result of ectopic tissue or brous bands [53] and include intestinal obstruction (36%), diverticulitis/inammation (32%), intussusception (13%), hemorrhage (11%), and perforation (7%) [49]. In 0.5% to 3% of symptomatic cases of Meckels diverticula, tumors are present, the most common of which are carcinoid tumors in 33% of cases [49]. History and Physical Because Meckels diverticula can imitate a variety of familiar disease states, including appendicitis, peptic ulcer disease, biliary colic, gastroenteritis, colonic diverticulitis, and milk protein allergy [53], its diagnosis is problematic and should be considered in all pediatric patients with unexplained abdominal pain, nausea and vomiting, or intestinal bleeding. In children, painless bleeding is the most common presentation for Meckels diverticulum (mean age of 5 years) and is the result of ileal mucosal ulceration adjacent to acid-producing gastric mucosa. Obstruction is the most common presenting complaint in adults and occurs in up to 40% of pediatric patients [54]. Most patients are asymptomatic, with the anomaly discovered on contrast study or laparotomy for another indication. Physical examination ndings are variable and are dependent upon the nature of the presenting complication. Infants and children presenting with rectal bleeding often have a benign abdominal examination, and tachycardia is more consistent with a brisk intestinal bleed (bright red blood) rather than slower bleeding (mahogany stool). Obstructed patients are generally distended and have hyperactive bowel sounds and abdominal tenderness without peritoneal signs and rarely have a palpable mass. Similar to appendicitis, patients with Meckels diverticulitis have focal tenderness with guarding, hypoactive bowel sounds, and peritonitis if perforation has occurred. Imaging Studies Barring the patient that presents with an acute abdomen mandating emergent surgical exploration, the diagnostic workup is largely based

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upon imaging targeted at a strong clinical suspicion of Meckels diverticulum. Routine lab studies, including a CBC, electrolytes, and liver function studies, are generally not helpful in making the diagnosis. Although plain abdominal radiographs, a CT scan, and an ultrasound may be useful in assessing the complications from Meckels diverticulum (eg, ileus, free uid in the abdomen, inammation), they are not diagnostic for Meckels diverticulum [55]. The most useful method of diagnosis is with a technetium-99m pertechnetate scan, which is dependent upon uptake of the isotope in heterotopic gastric tissue and has a reported accuracy of 90% in the pediatric population [56], although documented accuracy is 46% in the adult population [57]. This accuracy can be enhanced to 95% in children with the combination of pentagastrin (to enhance technetium uptake by ectopic gastric mucosa), cimetidine (to decrease intraluminal technetium release), and glucagon (to decrease peristalsis) [58,59]. Surgery Treatment for Meckels diverticulum has traditionally been dependent upon whether the entity is symptomatic or discovered incidentally. Symptomatic Meckels diverticula warrant a surgical resection of the diverticulum itself or the segment of small bowel containing it (Fig. 6). When bleeding is the presenting symptom, segmental small bowel resection is indicated because the bleeding source is often caused by mucosa adjacent to the diverticulum. Whereas surgical treatment for symptomatic Meckels diverticula is generally straightforward, the management of those discovered incidentally has been the topic of much investigation and debate. Given earlier published lifetime complication rates near 4% for unresected asymptomatic Meckels diverticula [52,60] versus a reported morbidity of 7% to 12% for elective resection [49], expectant management without resection had been the standard of care. More recent studies have proposed a lifetime complication rate requiring surgical intervention to be around 6%, whereas the overall morbidity of removal of incidental Meckels diverticula is 2% [61], suggesting that surgical resection has become the norm for incidental, asymptomatic cases. HIRSCHSPRUNG DISEASE Background The classic description of Hirschsprung disease was credited to Harald Hirschsprung in 1888. This disease entity is characterized by aganglionosis in the myenteric (Auerbach) and submucosal (Meissner) plexi of the distal colon causing a sustained contraction of that segment. In approximately 80% of cases, the aganglionic segment involves the rectum and the sigmoid colon only, whereas in 20% of cases, the aganglionic

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FIGURE 6. Intraoperative photograph of a Meckels diverticulum originating from a segment of small intestine.

segment involves the more proximal bowel and may involve the entire colon or the entire colon and variable length of the small bowel. Enlarged nerve trunks are present in the submucosa between the two muscle layers and contain increased levels of acetylcholinesterase. The smooth muscle in the aganglionic segment has a normal tone and a normal excitationcontraction coupling mechanism, and it responds to cholinergic and adrenergic agonists in a way that indicates normal functioning receptors. Based upon this physiology, the disease seems to be neurogenic in nature [62]. The enteric nervous system is formed by cells that migrate to the bowel from the neural crest. Hirschsprung disease is thought to be a neurocristopathy, related to the premature arrest of the craniocaudal migration of neural crest cells during the fth to the twelfth week of gestation. In human fetal models of Hirschsprung disease, neural crest cells had not been observed in the distal gut before their appearance in the proximal gut [63]. This has signicant implications for the surgical treatment of the disease in that there are no skip lesions. Once the transition zone has been identied, the surgeon can be condent that he knows the exact extent of the disease. Hirschsprung disease occurs in approximately 1 in 5000 live births. There is evidence that genetic factors play a role in this disease entity. Increased risk in siblings is reported to be from 2% to 9%, with a dominant pattern of inheritance seen in many families. There is increased association of Hirschsprung disease in other chromosomal abnormalities, including trisomy 21 (2% to 10% of cases). There is evidence for autosomal dominant, autosomal recessive and polygenic forms [6466]. There is also an association of Hirschsprung disease and the multiple endocrine

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neoplasia syndrome MEN 2a, which predisposes these patients to thyroid cancer [67]. History and Physical Examination Hirschsprung disease presents most commonly in the newborn with abdominal distension and sometimes bilious vomiting. There is often a failure to pass meconium within the rst 24 hours of life. Some infants present after the newborn period with severe chronic constipation, whereas some present with full-blown sepsis from enterocolitis causing toxic megacolon, characterized by fever, bilious vomiting, explosive diarrhea, abdominal distension, and shock [68]. Diagnosis The diagnosis of Hirschsprung disease is made initially by barium contrast enema. By using this modality, one can visualize the classic transition zone where the distal bowel is smaller in diameter than the proximal dilated bowel. This transition zone may not be distinct in the newborn or in the infant or child with very short-segment Hirschsprung disease. The diagnosis is conrmed by suction rectal biopsy, usually done at the bedside, which conrms the absence of ganglion cells and the presence of nerve trunk hypertrophy. Some centers also stain these specimens for excess acetylcholinesterase to aid in the diagnosis [69]. In the older child who presents with severe constipation since infancy, malnutrition, and an empty rectal vault on physical examination, a fullthickness biopsy under anesthesia is indicated. Surgery Treatment of the patient with Hirschsprung disease starts with colonic irrigations with warm saline to assist in the evacuation of gas and stool. Broad-spectrum antibiotics should be administered in the infant or child who has any suspicion for enterocolitis (eg, fever, tachycardia, a tender abdomen, leukocytosis, or leukopenia). There have been many changes in the surgical approach to Hirschsprung disease in the last several years. In the past, a two- or three-stage correction was planned, with a leveling colostomy in the newborn period and formal pull-through procedure when the child was between 1 and 2 years of age. Today, there are four basic pull-through procedures (Swenson, Duhamel, Rehbein, and Soave) that are used by pediatric surgeons. An in-depth discussion of the subtleties of how one chooses which version of a given procedure is beyond the scope of this article. In recent times, single-stage pullthroughs without interval colostomies are being done routinely for shortsegment disease [70].

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Laparoscopy is used by many surgeons to minimize the size of surgical wounds and to facilitate the pelvic dissection. Complete transanal pull-throughs without any abdominal portion of the procedure are also being performed. These can be done safely in children who have shortsegment disease with a transition zone in the mobile part of the sigmoid colon. Finally, the formal pull-through surgery is being offered in the newborn as small as 2 to 3 kg [71]. These innovations have led to the corrective surgery being done at an earlier age, which is easier for the parents to manage with respect to enterostomies and post-operative rectal dilations. There is some evidence that the long-term results in these patients are improved when the pull-through is done early in the newborn period, but long-term data are not available [72]. Avoiding a colostomy has decreased the overall morbidity of the treatment of Hirschsprung disease because a substantial number of complications are related to this stage of therapy. The minimally invasive approach has also decreased morbidity from surgical wounds and postoperative adhesions. Whenever the infant has other concomitant medical issues or has longer segment disease, a rst-stage colostomy with a pull-through at a later time is the most prudent approach. Early complications of surgical therapy include an anastomotic leak leading to pelvic sepsis. This complication occurs in less than 1% of cases, can be life-threatening if not treated aggressively, and can have grave consequences on long-term continence, requiring a temporary diverting enterostomy. Other early complications include an anastomotic stricture, enterocolitis, fecal incontinence, and bladder dysfunction (usually noted in the older child). Late complications of surgical therapy include constipation and enterocolitis. Outcomes for Hirschsprung disease are variable, depending upon how the practitioner denes fecal continence and soiling. According to Cass [73], In practice, fecal continence can be dened as the passage of stool in the toilet such that no bowel motion occurs into the diaper or underclothes, whereas soiling requires a more stringent denition, such as the presence of any fecal staining on underclothes occurring more than once a month. Continence is the result of a complex physiologic function that is dependent on motor function, sensory input, extrinsic neural modulation, spinal pathways, and cerebral control [58]. A lack of normal fecal control is a signicant problem in long-term follow-up, with an incidence ranging from 10% to 50% [73,74]. SUMMARY The approach to the child with a surgical GI problem should include a thorough history and physical examination, followed by appropriate laboratory and imaging studies. An understanding of anatomy and in some cases embryology can be helpful in establishing an accurate diagnosis. Early surgical consultation should be the rule because some of these problems rapidly become life threatening.

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Key Points Although CT scan and ultrasound have exceptional sensitivity and specicity for acute appendicitis, they should be performed only after the diagnosis is in question after a thorough history and physical examination by an experienced pediatric surgeon (Evidence Level C). Pyloric stenosis should be suspected in an infant with nonbilious emesis and weight loss. The preferred radiographic study is diagnostic ultrasound, which avoids radiation exposure and the risk of barium aspiration incurred with an upper GI (Evidence Level A). Although barium enema has been the modality of choice for the diagnosis and nonoperative reduction of ileocolic intussusception, diagnostic ultrasound with pneumatic air reduction has demonstrated comparable results with respect to diagnosis and reduction, with fewer potential complications (Evidence Level A). Upper GI remains the gold standard test for intestinal malrotation, a diagnosis that should be considered in any pediatric patient presenting with bilious emesis (Evidence Level B). Despite surgical correction for Hirschsprung disease, patients can harbor colonic dysmotility and present with refractory constipation and incontinence (Evidence Level B).

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