1. CBC and differential. Leukocytosis and left shift are usual findings with appendicitis. Children with chronic illnesses (eg, inflammatory bowel disease) are often anemic. If marked neutropenia (WBCs < 1000/mm3), consider typhlitis.
2. Serum electrolytes, glucose, BUN, creatinine. If significant vomiting, check electrolytes and hydration status. BUN and creatinine are elevated in hemolytic uremic syndrome. Glucose is elevated in diabetic patients whose abdominal pain is associated with ketoacidosis.
3. Bilirubin, AST, ALT, alkaline phosphatase. Elevated in hepatobiliary disease.
4. Amylase, lipase. Elevated in pancreatitis (lipase is more specific).
5. Urinalysis and culture. UTIs are associated with WBCs in urine and a positive culture; calculi produce hematuria. (Presence of a few WBCs or RBCs is also consistent with appendicitis adjacent to ureter or bladder.) Urine sediment is often abnormal in Henoch-Schonlein purpura.
6. p-HCG. Exclude ectopic pregnancy in postpubertal girls with lower abdominal pain.
8. Stool culture. If diarrhea is prolonged or associated with blood or elevated fecal leukocytes, check for Campylobacter, Yersinia, Salmonella, Shigella, and Clostridium difficile.
9. ESR. Nonspecific, but usually elevated in inflammatory bowel disease.
C. Radiographic and Other Studies. Imaging studies are unnecessary in most children with abdominal pain, because diagnosis can be established clinically.
1. Chest and abdominal x-rays. Chest x-ray may reveal lower lobe pneumonia; an upright chest film is the best view for detecting pneumoperitoneum. Abdominal x-rays are usually nonspecific but will show intestinal obstruction, stool with constipation, and occasionally a radiopaque urinary calculus or an appendiceal fecalith. Pneumatosis intestinalis (air in the wall of the intestine) is the hallmark of necrotizing enterocolitis. In patients with inflammatory bowel disease, a much dilated transverse colon suggests toxic megacolon.
2. Ultrasonography. Often useful if pain is localized. The best imaging study for gynecologic causes of abdominal pain (eg, ovarian torsion, ovarian cysts, PID with tuboovarian abscess). May identify inflamed appendix when diagnosis is unclear.
3. CT scan. Provides excellent anatomic detail of entire abdomen. Considered 95% accurate in diagnosing appendicitis. Typhlitis may be diagnosed and followed to identify necrosis and perforation. Because significant radiation exposure is involved, use only when necessary.
4. GI contrast x-rays. Immediately obtain an upper GI series for bilious vomiting if midgut volvulus is suspected. Upper and lower GI contrast studies are useful in patients with obstruction or inflammatory bowel disease.
5. Upper and lower GI endoscopy. Useful in patients with inflammatory bowel disease.
6. Diagnostic laparoscopy. If the cause of persistent abdominal pain cannot be identified by other means, intra-abdominal organs can be viewed directly with a laparoscope. If patient has right lower abdominal pain, the appendix should be removed even if it appears normal; in many cases the pain will resolve.
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