(abdominal mass) cystourethrogram Blood urea nitrogen, creatinine CT and MRI refer to intracranial imaging in this table ECG, electrocardiogram; CT, computed tomography; MRI, magnetic resonance imaging; PCR, polymerase chain reaction Obtain a complete history including any previous medical problems such as known heart disease or failure to thrive Determine the time of onset of symptoms, exposure to infection, medications given at home, and specific symptoms noted by the parents Next, perform a careful physical examination because specific findings may lead to a diagnosis other than sepsis ( Table 73.3 ) Follow with laboratory evaluation as indicated by findings on history and physical examination Promptly obtain a rapid test for blood sugar as abnormalities may be life-threatening For all sick infants, obtain a blood culture and a urine culture, by either urethral catheter or suprapubic bladder tap Perform a lumbar puncture unless physical findings point strongly to a diagnosis other than sepsis or the infant is too critically ill to tolerate the procedure (e.g., respiratory distress) Bruising or bleeding with intravenous access attempts suggests the possibility of DIC and is a contraindication for lumbar puncture If available, send a CSF panel to rapidly detect pathogens associated with meningitis and encephalitis by PCR A chest radiograph is also essential to look for pulmonary infection and to evaluate the heart size Obtain a CBC as leukocytosis will add support to a suspicion of sepsis and may also be found in various other disorders including viral infections, myocarditis, pericarditis, intracranial bleeds, NEC, appendicitis, intussusception, and methemoglobinemia For all sick infants, send studies to evaluate serum sodium, potassium, chloride, glucose, and bicarbonate level, as metabolic problems (disturbances in acid–base balance, electrolytes, blood sugar) can result from sepsis or be the primary problem that mimics sepsis If hyponatremia is found, consider water intoxication, aspirin toxicity, cystic fibrosis, and CAH If there is also a marked hyperkalemia, CAH is most likely If there is hypochloremic alkalosis or alkalosis alone, then consider pyloric stenosis, aspirin toxicity, or gastroenteritis Hypoglycemia may be secondary to poor glucose reserves in an ill infant or related to drug (aspirin) toxicity, inborn errors of metabolism, CAH, or methemoglobinemia The presence of acidosis could be due to poor perfusion caused by shock, as well as primary problems such as dehydration, drug toxicity, methemoglobinemia, appendicitis, CAH, and inborn errors of metabolism In