large ovarian cyst, which produces vomiting and marked abdominal pain Abdominal ultrasound generally identifies intra-abdominal cysts readily Renal abnormalities are probably the most common cause of abdominal masses in early infancy Renal cystic disease is the most common cause of flank mass in the neonate Hydronephrosis due to ureteral–pelvic junction obstruction or posterior urethral valves may also cause abdominal distension in the neonate Confirmation of renal anomalies is made by ultrasound Tumors such as neuroblastoma, Wilms tumor, an ovarian tumor, and a teratoma generally can be palpated easily as firm, discrete abdominal masses by the time they are causing frank abdominal distension (see Chapter 98 Oncologic Emergencies ) Bowel duplication can be a subtle diagnosis until a complication such as mechanical bowel obstruction or hematochezia develops Finally, a midline pelvic mass should suggest pregnancy or hematocolpos EVALUATION AND DECISION History The history should attempt first to differentiate acute from chronic symptomatology by focusing on the rate of progression, recent trauma, weight loss, or weight gain Progressive distension suggests accumulating ascites, intraabdominal tumor, or increasing hepatosplenomegaly Parents may note early, subtle changes in these symptoms before they become apparent to the clinician Next, systemic signs such as fever, anorexia, edema, and lethargy further define the acuteness of the problem and, to some degree, narrow the diagnostic possibilities One must always be on alert, however, for an acute complication superimposed on a more subtle chronic condition Next, symptoms relative to specific organs, including the GI, renal, cardiac, and gynecologic systems, should be pursued These include questions about nausea, vomiting (bilious or nonbilious), abdominal pain, change in bowel habits, stool history (color, consistency), shortness of breath, cough, hemoptysis, urine output (including strength of stream and any abnormality of urinary color or foamy urine), menstrual history, and sexual activity Other important historical information includes stress or anxiety (associated with aerophagia), previous abdominal surgery, and recent medication use (including laxatives and antidiarrheal agents) Finally, a family history of anemia, early infant death among relatives or metabolic disease, a travel history, and a careful newborn history may be revealing Physical Examination