HISTORY OF PRESENT ILLNESS
The patient is a 4-year-old female on interim maintenance chemotherapy for acute lymphoblastic leukemia (ALL) who presents to outpatient oncology clinic with emesis and bloody stools. She was doing well until 3 days prior to arrival when she developed decreased activity and anorexia. The following day she developed nonbloody, nonbilious emesis occurring about every 2 hours. The day before presentation, she had three bloody maroon colored stools. The morning before arrival to clinic, her emesis had increased to six times per hour and she had become listless at home. There was no history of fever, rash, abdominal pain, petechiae, or purpura. She had no sick contacts.
The patient was diagnosed with ALL 4 months ago. She last received chemotherapy 1 month ago. Her course has been uncomplicated except for one admission for pneumonia (1 month ago) and one admission for fever in the setting of a central line (1 week ago). During both admissions all of her blood cultures were negative.
T 37.7°C; RR 28/min; HR 160 bpm; BP 100/60 mmHg
Weight 14.2 kg, 5th percentile (down from 16.6 kg 1 week ago); Height 150 cm, 95th percentile
General examination revealed a lethargic, disoriented child responding only to voice and painful stimuli. She had sunken eyes and dry mucous membranes without evidence of mucositis. Her cardiac examination revealed tachycardia but she had a regular rhythm with good peripheral perfusion. Her lung examination was normal. Her abdomen was distended but there was no tenderness, rebound, or guarding. Bowel sounds were hyperactive. There was a small amount of gross blood on rectal examination with no evidence of anal fissures or masses. Her cranial nerves were intact.
Laboratory evaluation revealed 10 200 white blood cells/mm3 with 6% band forms, 64% segmented neutrophils, 8% lymphocytes, and 20% monocytes. Her hemoglobin was 10 g/dL and her platelet count was 240 000 cells/mm3. Serum chemistries were as follows: sodium, 133 mmol/L; potassium, 3.2 mmol/L; chloride, 78 mmol/L; bicarbonate, 20 mEq/L; blood urea nitrogen, 105 mg/dL; creati-nine, 1.4 mg/dL; glucose, 100 mg/dL; phosphorus, 7.2 mg/dL; uricacid, 20.6 mg/dL; bilirubin, 1.2 mg/dL; alanine aminotransferase, 342 U/L; aspartate aminotransferase, 96 U/L; lactate dehydrogenase, 1432 U/L; amylase, 36 U/L; lipase, 82 U/L; and ammonia, 24 μmol/L.
Abdominal radiographs showed multiple dilated loops of small bowel with no air in the distal large bowel. There was no visible free air in the abdominal cavity. Blood and urine cultures were drawn at the time of admission.
COURSE OF ILLNESS
The patient’s altered mental status did not improve with fluid resuscitation. She was started on vancomycin and cefepime for broad-spectrum antibiotic coverage. She underwent a magnetic resonance imaging (MRI) of the head which was normal without signs of increased intracranial pressure or hemorrhage. A nasogastric tube was placed to decompress the abdomen. A CT scan of the abdomen was completed followed by a nuclear medicine imaging study which revealed the diagnosis (see Figure 3-9).
FIGURE 3-9. Meckel scan. (Reproduced, with permission, from Sawin RS. Appendix and Meckel’s diverticulum. In: Oldham KT, Colombani PM, Foglia RP, Skinner MA, eds. Principles and Practice of Pediatric Surgery. Philadelphia: Lippincott Williams & Wilkins; 2005:269-1282.)
DISCUSSION CASE 3-5
The patient’s abdominal radiograph with dilated loops of small bowel and a paucity of air in the large bowel suggested intestinal obstruction. The etiology of intestinal obstruction can be either intraluminal or extraluminal. In a 4-year-old child, causes of intraluminal obstruction include bezoars, fecal impaction, foreign bodies, intraluminal tumors, inflammatory bowel disease, parasites, or Hirschsprung disease. Extraluminal causes of obstruction in a child of this age include an incarcerated hernia, malrotation with volvulus, duplication system, extraluminal tumor or compressing lymph node, or adhesions from previous abdominal surgeries.
In a child with suspected intestinal obstruction, blood tests are often normal early in the process. As vomiting and dehydration persist, the child may develop hemoconcentration, electrolyte abnormalities, and acidosis. Plain abdominal films in the upright and supine positions are helpful in evaluating the distribution of gas and fluid in the gastrointestinal tract. In complete obstruction, multiple air fluid levels and luminal dilation are seen proximally to the obstruction and the colon distal to the obstruction collapses. Perforation must be strongly considered if air is seen in the bowel wall, in the portal venous system, or within the peritoneal cavity. Contrast studies can be helpful in distinguishing ileus from obstruction. However, if perforation or colonic obstruction is suspected then barium should be avoided. Computed tomography can be helpful in localizing the obstruction and determining the etiology.
This patient had a CT scan that revealed a diverticulum with associated obstruction. A 99 mtechnetium(Tc)-pertechnetate scan was then performed which confirmed the presence of a Meckel diverticulum (see Figure 3-9). The patient was taken to the operating room where she was found to have a distal small bowel obstruction related to a Meckel diverticulum. The diverticulum was resected without any evidence of bowel wall infarction.
INCIDENCE AND EPIDEMIOLOGY OF A MECKEL DIVERTICULUM
A Meckel diverticulum is the most common congenital anomaly of the gastrointestinal tract, occurring in approximately 2% of the population. The diverticulum results from the incomplete obliteration of the vitelline duct, which connects the intestine to the yolk sac in the developing embryo. A Meckel diverticulum is usually 2 to 6 cm in length and is located on the antimesenteric border approximately 2 feet proximal to the ileocecal valve. Half of all Meckel diverticula will contain gastric, pancreatic, duodenal, or colonic ectopic tissue.
Meckel diverticula are more common in males, who also present more frequently with symptoms. They have been associated with other congenital anomalies including cardiac defects, cleft palate, and anorectal malformations.
Only 5% of all patients with a Meckel diverticulum will become symptomatic. Most frequently, symptomatic patients present within the first 3 years of life. The most common presentation is painless rectal bleeding, either bright red or maroon in color. Rectal bleeding is most often due to ectopic gastric tissue which produces acidic secretions that results in ulceration and bleeding. A Meckel diverticulum can also present with bowel obstruction resulting in abdominal pain, distension, and emesis. The most common reason for obstruction is when the diverticulum serves as a lead point for an intussusception. Obstruction can also result from intraperitoneal bands that connect the remnant vitelline duct to the ileum and umbilicus. Finally, a Meckel diverticulum can become inflamed (diverticulitis) resulting in severe right lower quadrant pain mimicking appendicitis. The inflamed diverticulum can perforate and result in peritonitis.
A Meckel diverticulum should be considered in any patient with painless rectal bleeding. Other causes of hematochezia are listed in Table 3-7. Plain abdominal radiographs and routine barium studies are not usually helpful in diagnosing a Meckel diverticulum.
TABLE 3-7. Differential diagnosis for hematochezia.
Inflammatory bowel disease
Meckel scan. The most useful study is a Meckel radionuclide scan which is performed after intravenous infusion of technetium-99m pertechnetate. The pertechnetate is taken up by gastric mucosa. In patients with ectopic gastric mucosa, there will be increased activity in the area of ectopic mucosa (usually the right lower quadrant). Uptake can be improved with administration of cimetidine, glucagon, or pentagastrin. In children, the Meckel scan has a sensitivity of 85% and a specificity of 95%. One must be aware of false positives and false negatives that may occur. False positives may arise from other sites of ectopic gastric mucosa, focal areas of small bowel pathology, vascular anomalies, bowel ulcerations, or bowel obstructions. False negatives may occur when the ectopic gastric tissue in the diverticulum is minimal or when the scintigraphic activity is diluted due to impaired vascular supply, brisk bleeding, or bowel hypersecretion.
Computerized axial tomography (CT scan). When the Meckel scan is nondiagnostic, a CT scan may be useful in detecting an inflamed or obstructing diverticulum.
LAPAROTOMY AND LAPAROSCOPY.
An inflamed Meckel diverticulum may be implicated as the cause of right lower quadrant abdominal pain or intestinal obstruction during surgical exploration. It may also be an incidental finding during abdominal surgery.
Treatment starts with ensuring hemodynamic stability. Definitive therapy includes surgical resection of the Meckel diverticulum on an emergent or semi-elective basis. Associated intussusception usually requires surgical rather than hydrostatic reduction; partial bowel resection with primary anastomosis is occasionally required. The treatment of an asymptomatic Meckel diverticulum is less clear. Characteristics that may suggest an increased risk of developing complications, and thus a need for surgical removal, are younger age (<10 years), longer diverticulum (>2 cm), and a narrow base (<2 cm in diameter).
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