A complete blood count may provide evidence for inflammation (white blood cell [WBC] and platelet count), poornutrition or bleeding (hemoglobin, red blood cell volume, reticulocyte count), and infection (WBC number and differential, presence of toxic granulation). Serum electrolytes, bloodurea nitrogen (BUN), and creatinine help define hydration status. Tests of liver dysfunction include total and direct bilirubin, alanine aminotransferase, aspartate aminotransferase for evidence of hepatocellular injury, and γ-glutamyltransferase oralkaline phosphatase for evidence of bile duct injury. Hepatic synthetic function can be assessed by coagulation factor levels,prothrombin time, and albumin level. Pancreatic enzyme tests (amylase, lipase) provide evidence of pancreatic injury or inflammation. Urinalysis can gauge dehydration and identify a possible source of protein loss.
Consultation with a radiologist is often advisable to discuss appropriate imaging, decide what variants of the technique to use, and learn how to prepare the patient for the study.
A plain abdominal x-ray to document excessive retained stool when history is consistent with constipation and encopresis is not necessary, as examination alone can confirm the diagnosis.
Endoscopy permits the direct visualization of the interior of the gut. Video endoscopes may be used even in very small infants by pediatric gastroenterologists. Wireless capsule endoscopy (Fig. 126-1) enables visualization of lesions beyond the reach of conventional endoscopes.
Consultation with a pediatric gastroenterologist for endoscopy is recommended for further evaluation of suspectedesophageal or gastric inflammation unresponsive to medications and to confirm the diagnosis of eosinophilic esophagitisor celiac disease, evaluate gastrointestinal bleeding, evaluatesuspected inflammatory bowel disease, and screen for polypdisorders. In addition, a trained endoscopist can removeesophageal and gastric foreign bodies and place feeding tubes.
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Figure 126-1 Wireless capsule endoscopy: Aphthous ulcers (arrows) in jejunum diagnostic of Crohn’s disease in patient with negative find-ings on upper endoscopy and colonoscopy.
Abdominal pain can result from injury to the intra-abdominal organs or overlying somatic structures in the abdominalwall, or from extra-abdominal diseases. Visceral pain results when autonomic nerves within the gut detect injury, transmitting sensation by nonmyelinated fibers. The pain is vague, dull,slow in onset, and poorly localized. A variety of stimuli, including normal peristalsis and various intraluminal chemical andosmotic states, activate these fibers to some degree. Regardlessof the stimulus, visceral pain is perceived when a threshold ofintensity or duration is crossed. Lower degrees of activation may result in perception of nonpainful or perhaps vaguelyuncomfortable sensations, whereas more intensive stimulation of these fibers results in pain. Overactive sensation may be thebasis of some kinds of abdominal pain, such as functional abdominal pain and irritable bowel syndrome.