Lakshmana Das Narla, M.D.
Department of Radiology
Medical College of Virginia
of Virginia Commonwealth University
Richmond, Virginia
Elizabeth A. Hingsbergen, M.D.
Department of Radiology
Medical College of Virginia
of Virginia Commonwealth University
Richmond, Virginia
Charles E. Bagwell, M.D.
Department of Pediatric Surgery
Medical College of Virginia
of Virginia Commonwealth University
Richmond, Virginia
A. Bowel Necrosis
Necrotizing enterocolitis - NEC
Ischemia and Infarction
Neutropenic colitis
Sepsis
Emphysematous gastritis
Caustic ingestionB. Mucosal disruption
Pyloric obstruction
Bowel obstruction
Blunt abdominal trauma
Trauma of child abuse
Hirschsprung disease
Crohn's disease
Ulcerative colitisC. Increased mucosal permeability
Immunotherapy
- graft versus host disease
- organ transplantation
- bone marrow transplantation
AIDS enterocolitides
Steroid therapy
Chemotherapy
Collagen vascular diseaseD. Pulmonary disease
Asthma
Chronic pulmonary disease
Cystic fibrosis
Chest traumaSource: Modified from Bert Lincoln Pear
Necrotizing enterocolitis (NEC) is the most common, and at times
fatal, acquired GI emergency in the neonatal intensive care unit. Ten percent of
infants weighing less than 1500 grams have definite NEC and another 17% have possible
NEC.
A staging system developed by Bell recognizes three stages:
Stage I,
early or suspected NEC;
Stage II,
definite NEC; and
Stage III,
advanced disease.
The exact etiology of NEC is unknown; ischemia, infection, and
hyperosmolar feeds contribute to the development of NEC. Unfed babies seldom
develop NEC. Occasionally there are epidemic outbreaks of NEC in newborn nurseries,
which suggests an infectious etiology. Symptoms in the form of abdominal distention,
feeding intolerance, vomiting, blood in the stool, diarrhea, lethargy, instability of
temperature and blood pressure, and apnea are usually seen in the first week of
life. In advanced disease, the signs may include erythema of the body wall, and
palpable distended bowel loops [Figure 10].
The mortality of NEC is about 30%, but is higher in very low birth weight infants.
Though NEC is more common in premature infants, it may occur in full term infants with
risk factors including hypoxia, hypoglycemia, polycythemia, respiratory distress syndrome,
congenital heart disease [Figure 11],
cardiac surgery [Figure 12], repair
of gastroschisis, [Figure 13] and
intestinal atresia. Babies born to mothers who abuse cocaine also have a higher
incidence of NEC [Figure 14].
In NEC, inflammation begins in the mucosa and submucosa and may extend
through the full thickness of the bowel wall. Involvement may be diffuse but is
usually patchy [Figures 15 A & B].
The distal ileum and right colon are involved far more frequently than any other site
though any part of the intestine may be affected.
Plain films are routinely and commonly used for the diagnosis and
follow-up of patients with NEC. The most commonly detected abnormality is diffuse
gaseous distention of the intestine, a non-specific finding. A persistent area
of dilated bowel may indicate focal involvement of bowel with NEC. Pneumatosis in
the form of submucosal or subserosal air is classic for NEC. The bubbly submucosal
morphology of pneumatosis is easily confused with stool or meconium in a normal
colon. In difficult cases follow-up films are helpful, as stool will usually move
whereas pneumatosis may not. At times prone views may also be helpful in
distinguishing pneumatosis from stool. The medical treatment of NEC consists of bowel
decompression with an NG tube, NPO, IV fluids and antibiotics. The reported incidence of
portal venous gas (PVG) in NEC varies widely, and probably occurs in between 10% and 30%
of patients. PVG is not an indication for surgery. Free intraperitoneal air is an
indication for surgery, and can be detected on supine film, left lateral decubitus film or
supine cross table lateral film [Figure 16].
Only one half to three quarters of patients with perforation have free air detectable even
on horizontal beam films. A patient weighing less than 1500 grams may be too
unstable to go to the operating room and can be treated by percutaneous peritoneal
drainage at the bedside [Figure 17].
This technique can be very successful in temporizing in the very ill neonate. In 40%
of these infants, no further therapy is needed; the other 60% of infants generally require
surgery at a later date.
The complications of NEC are strictures, enterocyst formation, malabsorption, inflammatory polyps, and enteric fistulae. Intestinal strictures may follow either medical or surgical management of NEC and occur in 10% to 20% of survivors. Although NEC mostly affects the distal ileum and right colon, most strictures occur in the left colon, and most often occur in or adjacent to the splenic flexure [Figure 18]. Colonic strictures are multiple in 30% of cases. Strictures can be treated more conservatively by balloon catheter dilatation. In children who have had diversion ileostomy or colostomy, it is important to evaluate the distal defunctionalized bowel with contrast enema to rule out strictures before reanastomosis.
Any patient with poor cardiac function and failure can be at risk
for pneumatosis intestinalis and associated perforation. In the first 2 days of
life, development of pneumatosis should raise a red flag for hypoplastic left or right
heart syndrome.
Case: A nine year old patient with history of band heterotopia, presented with acute onset
of respiratory failure. Chest x-rays [Figure
19] showed marked cardiomegaly with failure. Echocardiogram showed poor
contractility with ejection fracture of 10%. During the PICU management of cardiac
failure, she developed abdominal distension. Abdominal films revealed extensive
pneumatosis of the right colon. Over the next week, her cardiac function improved as
did the pneumatosis intestinalis.
Pneumatosis secondary to mucosal disruption can be caused by ulceration, erosions or trauma (blunt abdominal trauma including non-accidental trauma - child abuse).
Case: A 5 year old cerebral palsy patient was involved in a motor vehicle accident. Initially he was admitted for a right humerus fracture; during the hospital stay he developed extensive pneumatosis and portal venous gas [Figure 20].
John Caffey in 1946 noted an association in children of subdural hematoma and long bone fractures. In 1962, Kempe and Silverman wrote the classic article entitled "The Battered Child Syndrome". Of child abuse and neglect fatalities, 90% are younger than five years and 40% are infants <1 year of age. The classic metaphyseal corner fracture bucket -handle fracture of long bones has the highest specificity for child abuse. Mortality and morbidity are from central nervous system (Shaken baby syndrome) and visceral injuries. The spectrum of visceral injuries in child abuse include: gastric perforation, gastric intramural hematoma and pneumatosis, perforation of small bowel (with 60% occurring in jejunum distal to the ligament of Treitz, 30% in duodenum and 10% in ileum), duodenal, jejunal and colonic hematoma, pancreatitis and pancreatic pseudocyst, and liver, spleen and kidney laceration. Adrenal hemorrhage, chylous ascites and bladder rupture are also associated with child abuse.
Case: A 21 month old girl was brought to the emergency department unconscious and hypotensive. Physical examination revealed multiple bruises, lacerations and human bite marks on the abdomen and back. Radiological work up included normal chest, cranial CT and skeletal survey. Abdominal CT showed gastric antral thickening due to intramural hematoma [Figure 21A]. Upper gastrointestinal examination showed antral hematoma and no duodenal hematoma [Figure 21B]. On the second day she had increasing abdominal tenderness and elevated white count with left shift. Repeat abdominal CT showed gastric pneumatosis [Figure 21C], which resolved with conservative management. The intramural hematoma may result in gastric mucosal tear, and subsequent dissection of air into the wall of the stomach is enhanced by partial or complete obstruction. Antral hematoma and gastric pneumatosis are additional intraabdominal manifestations of child abuse.
Pneumatosis secondary to mucosal disruption presumably due to overdistention is seen in peptic ulcer, pyloric stenosis, annular pancreas, and more distal obstructions. The causes for acquired small bowel obstruction in children include appendicitis, adhesions from previous surgery, intussusception, incarcerated inguinal hernia, malrotation with midgut volvulus, and Meckel's diverticulum.
Case: A six week old infant presented
with vomiting and abdominal distension. Abdominal films [Figure 22 A&B] showed an
obstructive bowel gas pattern with pneumatosis; the obstruction was secondary to
incarcerated inguinal hernia.
Pneumatosis Intestinalis Secondary to Hypertrophic Pyloric Stenosis (HPS):
In 1952, Koch described a 59 year old man with complete pyloric
stenosis associated with peptic ulcer, resulting in pneumatosis of ileum. Fifty-five
percent of all cases of pneumatosis reviewed at the time were secondary to gastric or
duodenal ulcer accompanied by pyloric stenosis.
Hirschsprung in 1888 coined the term "pyloric stenosis" and
believed that pyloric narrowing was congenital. However, HPS is not found in utero
or at birth. Most cases present between the second and sixth week of life. The cause
of circular muscle hypertrophy remains unknown, probably secondary to abnormal innervation
of circular muscles and possibly related to lack of nitric oxide synthase activity.
Genetic factors are also important in HPS, since it is more common in babies with affected
parents or siblings. HPS is more common in boys than in girls (4:1) and in white
than in black or oriental children. The often-quoted increased incidence of HPS in
first-born babies is probably not correct.
Projectile non-bilious emesis which may be blood tinged secondary to
gastritis is the common presentation. Patients may present with jaundice, metabolic
alkalosis and dehydration. The diagnosis of HPS can be made on clinical
grounds by palpation of the hypertrophied circular muscle (olive) in 80% of cases in
babies with appropriate history. If HPS is the presumptive diagnosis, US is the
examination of choice, with sensitivity and specificity approaching 100%. For other
causes of vomiting, including GE reflux or malrotation, UGI is the study of choice.
On US, the thickness of the muscle measured from the outer edge of the echogenic mucosal
complex to the outer edge of the muscle is the most sensitive and specific sign of
HPS. Recent work has shown that a muscle thickness of
3-mm or greater is virtually 100% specific for HPS [Figure 23A]. Measurements
should be made on a midline longitudinal view, through the midportion of the
pylorus. Overdistention of the stomach may push the pylorus posteriorly and make it
difficult to visualize; in this case the stomach needs to be decompressed with a
nasogastric tube. Most babies with HPS will have pyloric lengths of >16-mm, but
some patients without HPS will have lengths >16-mm. Thus, the diagnosis should
not be made on channel length alone [Figure
23B]. The plain film may show a "caterpillar appearance" of the
stomach secondary to deep peristaltic wave [Figure
23C]. UGI shows elongation and narrowing of the pyloric channel with
indentation on the antrum and duodenal bulb [Figure
23D]. Various signs have been described: Double track sign, teat sign,
mushroom sign and beak sign. The treatment of HPS is Ramstedt pyloromyotomy [Figure 23E].
Antral hyperplasia secondary to Prostaglandin E therapy in patients with ductal dependent
congenital heart disease is an iatrogenic cause of gastric outlet obstruction in the
neonatal period and may mimic HPS. Symptoms usually resolve after the
discontinuation of Prostaglandins.
Case: A premature infant at 4 weeks of age developed vomiting. Supine film of the abdomen showed pneumatosis intestinalis [Figure 24A]. Work up with ultrasound confirmed a diagnosis of HPS [Figure 24B].
Hirschsprung disease is a common cause of all neonatal bowel
obstruction, accounting for one third of all cases [Figure 25]. The incidence of
Hirschsprung disease is 1 in 5000 live births and increases to 3.6% in families with one
affected male and to 8% when a female has been affected. Hirschsprung disease is
three or four times as common in boys as in girls and, for unknown reasons, is very rare
in premature infants. In the uncommon total colonic variant, the incidence in boys
and girls is nearly equal with a strong hereditary tendency. Patients present in the
neonatal period 80% of the time, with presenting symptoms including delay in passage of
meconium, abdominal distension, constipation and bilious vomiting. Twenty percent of
the patients have associated abnormalities including: Down syndrome (8%), cardiac defects
(8%), GU abnormalities (6%), GI anomalies (4%). GI anomalies can include: colonic
atresia, imperforate anus, and neurocristopathies. Neurocristopathies can occur singularly
or in combination with neurocristopathic syndromes such as neuroblastoma,
pheochromocytoma, neurofibromatosis, Waardenburg's syndrome, and multiple endocrine
neoplasia II and Ondine curse or congenital central hypoventilation syndrome (CCHS).
The histopathological criterion for diagnosis of Hirschsprung disease
is absence of the ganglion cells of the myenteric plexus; this results in a narrowed
aganglionic segment and markedly dilated segment proximal to the distal obstruction. The
myenteric ganglion cells arise from the neural crest and migrate cephalocaudally along the
vagal trunks through the intestines. An early arrest in the migration between the
seventh and twelfth weeks of gestation leads to Hirschsprung disease, and can affect a
variable length of the colon and the small bowel. Aganglionosis affecting the small
bowel is rare, occurring in approximately 3% of the patients. The transition zone
from abnormal to normal ganglionic bowel is found in rectosigmoid or sigmoid colon in 65%,
the descending colon in 14%, the rectum in 8% and the more proximal large bowel in 10% [Figure 26].
Eighteen percent of patients with disease develop enterocolitis during the first 3 months
of life, and enterocolitis can develop after surgery [Figure 27]. Mortality is as high as
30%; some of these patients will have pseudomembranous colitis that can be rapidly fatal
without prompt treatment.
Another well-documented complication of Hirschsprung disease, occurring
in 4% of patients, is perforation of the bowel. This most commonly involves the
proximal colon (68%), the appendix (17%), or distal small bowel (6%). This
complication is most commonly associated (62%) with total aganglionosis, and generally
occurs by 4 months of age. At the time of perforation, the neonate may have no
other findings of aganglionosis, and thus the true diagnosis may not be considered.
Therefore, unexplained perforation of the colon, appendix or small bowel is another
indication for biopsy to exclude Hirschsprung disease.
In children with AIDS, GI symptoms are due primarily to acute and chronic enteric infections, and much less often to GI neoplasms. Imaging findings in children with AIDS are, for the most part, similar to those found in adults. Esophagitis due to Candida, cytomegalovirus (CMV) and herpes simplex (HSV) can occur. CMV can also involve the stomach and colon. CMV colitis is often quite severe and may result in pneumatosis, stricture, toxic megacolon, and perforation. Chronic diarrhea is one of the most disabling manifestations of AIDS and other etiologies include Cryptosporidium, Isopora belli, Salmonella, Shigella, Campylobacter, and Giardia. The pneumatosis in children with AIDS characteristically involves the cecum and right colon and most of the patients recover with conservative management. Immunodeficiency is assumed to play the same role as immunosuppression in causing lymphoid depletion and loss of bowel wall integrity.
Case: A 16 month old boy with systemic manifestations of AIDS for 10 months presented with fever, bilious vomiting and abdominal distention. Plain films of the abdomen revealed pneumatosis intestinalis diffusely involving the large bowel [Figure 28]. The patient was treated conservatively and the pneumatosis resolved within 3 days. No organisms were isolated from the blood or stool during the hospitalization, despite chronic CMV infection.
Acute enteric infection may be the most prevalent infectious disease
of humans and is probably the leading cause of death in the world. Microorganisms
responsible for acute diarrheal illnesses include viruses (rotavirus, parvovirus,
coxsackievirus, and echovirus), bacteria (Campylobacter jejuni, salmonella, shigella,
Escherichia coli, yersinia, staphylococcus aureus, and clostridium perfringens), and
parasites (Giardia lamblia, entamoeba histolytica).
Viruses are a major cause of childhood morbidity and mortality
worldwide. Mortality rates are low in developed countries but approach 1,000,000
annually in young children in developing countries. Rotavirus infections occur
repeatedly in humans from birth through old age. Rotavirus can be classified into groups
A-E according to antigenic groups on VP6, the major capsid antigen. Only groups A,
B, and C rotaviruses have been shown to infect humans, and most human rotavirus disease is
caused by group A viruses. The virus is highly infectious and appears to retain
infectivity over many months. Most episodes are asymptomatic or associated with
mild enteric symptoms. Infections in young children can be accompanied by severe
life-threatening diarrhea, most commonly with the primary infection. Children with
viral gastroenteritis generally present with watery, non-bloody diarrhea, often with
vomiting and low grade fever. Disease is self-limited and treatment is to correct
dehydration from excessive diarrhea. Infection with rotavirus can be verified by
electron microscopy, immunoabsorbent assay of stool specimens, or with complement fixing
antibody titers.
Case: A 6 month old child presented with diarrhea and bloody stools. Supine abdominal film demonstrate pneumatosis [Figure 29]. The patient was kept NPO and given fluid resuscitation, and recovered without any complications.
The vast majority of salmonella infections in the United States are
caused by serotypes not specifically adapted to human or animal host, whereas the most
frequent isolate in developing countries is S. typhi, which is highly adapted to human
hosts. The number of isolates reported in the United States has been increasing
steadily since 1975, largely a result of outbreaks associated with the mass production of
food products (particularly poultry), which are frequently contaminated. Salmonella
infection occurs when ingested organisms bypass gastric defenses, multiply within the
intestinal lumen, and penetrate the intestinal mucosa stimulating intracellular
accumulation of cyclic adenosine monophosphate (cAMP) that causes massive Na+ and Cl-
secretion into the gastrointestinal lumen. Organisms multiply within the macrophages
of the reticuloendothelial system. They may then disseminate via the systemic
circulation.
The clinical and pathological manifestations are subdivided into four
syndromes:
1) gastroenteritis,
2) enteric fever,
3) bacteremia with or without
disseminated disease,
4) asymptomatic carriage.
Serious complications of bacteremic infection include infections of the
aorta, endocardium, bone and meninges. Salmonella infection is particularly severe
in patients who have AIDS, leukemia, lymphoma, immunodeficiency of other causes,
inflammatory bowel disease, and macrophage dysfunction. Diagnosis is based on the
culture of the organism from appropriate sites.
Case: A 7 month old male presented with vomiting, diarrhea, and bright red stool per rectum. Abdominal films showed pneumatosis and no free air [Figure 30]. Stool cultures were positive for salmonella. The patient was treated conservatively with IV fluids; no antibiotics were given as this may increase the incidence of carrier states. Pneumatosis resolved by the third day.