Abdominal Masses in the Neonatal Period

History Gathering

  • Oligo or polyhydraminos
  • Full-term
  • Prenatal US, amniocentesis, pigtail catheter
  • Family history


Physical Exam

  • Supine : shape, umbilicus, hernias
  • Mass: location, size, shape, texture, mobility, tenderness, solid, cystic, air filler
  • If distension attempt to relieve to improve exam: NG for obstruction, Crede cath for urinary retention
  • +/- rectal exam
  • other: chest hypoplasia (Potter’s), bulging hymen (hydrometrocolpos), skin (neuroblastoma)


Differential by location

Flank Mass

  • Renal 55%
    • Hydronephrosis (most common)
      • Unilateral: UPJ or UVJ obstruction, aberrant renal artery, kink in ureter
      • Bilateral: bladder outlet obstruction (posterior valves or neurogenic bladder) dx: renal scintigraphy and voiding cystourethrogram
      • Tx: pyeloplasty, resect obstruction
      • Note: sever hydro can be detected in utero and treated with a uretero-amniotic shunt
    • Multicystic Kidney
      • Unilateral: multicystic dysplastic kidney
      • Bilateral
        • Autosomal recessive polycystic kidney, tx: dialysis, transplant
        • Autosomal dominant polycystic kidney presents later
    • Solid kidney tumor
      • Most likely mesoblastic nephroma (benign), concentric rings on US, resect
      • Wilm’s tumor rarely presents before 6m
  • Juxtarenal
    • Neuroblastoma; most common extracranial malignancy in early childhood, solid, fixed, retroperitoneal (adrenals), catecholamines (sweating, flushing)
      • Check urine homovanillic acid, vanillyl mandelic acid
      • AXR, US, CT (staging), bone marrow aspiration (look for bone mets)
      • Resection +/- chemo and radiation
      • Good prognostic factors: less than 1yo, stage, histology
      • 4S: stage 1-2 with dissemination to liver, skin (blueberry muffin spots), bone marrow; low risk
    • Adrenal hemorrhage – rare, asymptomatic, no management required
    • Renal Vein Thrombosis – rare, hematuria, HTN, thrombocytopenia, US, anticoagulation only if bilateral or extending to IVC
    • Pulmonary Sequestration

Right Upper Quadrant

  • Liver and biliary tree
    • Hemangioendothelioma (aka infantile hepatic hemangioma) - +/- cutaneous hemangiomas, can by asymptomatic or cause AV shunting and CHF, can spontaneously regress
      • Part of Kasabach-Merritt syndrome: low platlets, consumptive coagulopathy, hemolytic anemia
      • Treat with steroids, IFN, embolization/resection, or transplant
  • Hepatoblastoma
    • Elevated AFP, associated with Beckwith Wiedermann (macrosomia, macroglossia, visceromegaly, omphalocele)
    • Resect, +/- neoadjuvant chemo
  • Hamartoma
    • Benign but associated with chromosomal abnl
  • Choledochal cyst – cystic dilation of bile ducts, asymptomatic or jaundice, resection and drainage of hepatic duct into intestine

Left Upper Quadrant

  • Splenic cyst – resect if large

Mid Abdomen

  • Intestinal
    • Pyloric stenois – “olive”, non-bilious emesis, pyloromyotomy
    • Intestinal duplication – cystic or tubular, communicating or non-communicating, often no symptoms but can cause pain, obstruction, bleed, volvulus
      • Muscular ring on US, resect
  • Intestinal lymphatic malformation (omental, retroperitoneal, mesenteric) – mobile mass, benign but can cause obstruction, resect
  • Meconium
    • Ileus – associated with CF, small bowel atresia
    • Plug
    • Obstruction of  prematurity
    • Peritonitis or pseudocyst (if perforation occurs)
    • Present as distention, doughy mass, ground glass on AXR
    • Water soluble contrast enema can be diagnostic and therapeutic

Mid Abdominal Wall

  • Fascial defects causing sub-cutaneous mass
  • Omphalocele and gastroschisis are not “masses” technically
  • Omphalomesenteric remanents: incomplete vitelline duct reabsorption
    • Meckles, omphalomesenteric sinus, cyst, fistula
    • Surgical repair


  •  Uterine
    • hydrocolpos, hydrometrocolpos, imperforate hymen, vaginal transverse septum or atresia (block secretions caused by placental hormones)


  • Cystic tumors – mobile, usually benign, if complex on US get markers, large cysts need to be excised or percutaneously drained
  • Urachal cyst – the allantois remains  and there is a connection between umbilicus and bladder – urine out umbilicus or a cyst
  • Teratoma – can cause hemorrhage, polyhydraminos, posterior perineal mass: surgery +/- chemo
  • Hernias and hydrocele
    • Inguinal – can incarcerate or strangulate, surgery
    • Hydrocele – observe 1 year

Groin mass

  • Girls: entrapped ovary
  • Boys: ectopic testicle


“The Neonate with an Abdominal Mass” JC Chandler MWL Gauderer, Pediatr Clin Nam 51(2004) 979-997