MASAS ABDOMINALES EN RECIEN NACIDO La Imagenología disponible incluye: 1) Plain abdominal radiogaphy (AXR) 2) Ultrasonography (US) 3) Computed tomography (CT) 4) Radionuclide scanning (nuclear medicine, NM) 5) Intravenous urogram (IVU) 6) Voiding cystourethrogram (VCUG)

+ Usually the initial imaging study + Minimal ionizing radiation + To exclude gastrointestinal obstruction or fecal masses + Localize mass, and detect presence/absence of Ca++ + Exclude skeletal involvement, including spine 1) Plain abdominal radiography (AXR )

2) Ultrasonography (US): + No ionizing radiation (noninvasive) + Anatomy (solid vs. cystic, organ of origin, e.g. renal vs. extrarenal); Ca++ detection; vascularity (Doppler US) + Iodinated contrast medium not used (? role of US contrast medium in the future) + Limitations: bone/gas artifacts, operator dependency

3) Computed tomography (CT): + Anatomic and morphologic characteristic of mass + Extent of involvement of adjacent structures + Distant foci of spread + Not limited by bone and gas + Sedation may be required (decreased with fast scanners) + Use of ionizing radiation + Use of enteral and parenteral contrast media (iodine sensitivity may limits its use)

4) Radionuclide scanning (nuclear medicine, NM): + Organ (e.g. kidney) function, tissue vascularity, tumor viability + Magnetic resonance imaging (MRI) + No ionizing radiation + Excellent contrast resolution of soft tissues + Status of flowing vasculature may be evaluated + Best study for excluding extradural extension mass + Expensive, sedation frequently necessary (por largo de examen), not good for Ca++ detection + Upper gastrointestinal series (UGI) + To exclude specific gastrointestinal causes, e.g. duplication cyst, obstructive bowel lesion Barium or watersoluble iodinated contrast medium

5) Intravenous urogram (IVU): + Largely replaced by other modalities + Limited glomerular function in neonates limits use + Ionizing radiation, use of parenteral contrast medium

6) Voiding cystourethrogram (VCUG): + Evaluates lower urinary tract and genital masses + Angiography + Provides the precise segmental vascular anatomy and for interventional procedures (e.g. embolization)

Radiologic evaluation of an infant or child suspected of having an abdominal mass includes (a) demonstrating the presence or absence of a mass, and if present, the extent of the mass, (b) giving a specific pathologic diagnosis, when possible, based on the imaging characteristics, and (c) showing tumor spread. Although the possible etiologies are numerous the radiologic data, combined with the age of the child and clinical information, will usually allow a specific diagnosis or a very limited differential list. It is important to note that not all abdominal masses are clinically palpable, and not all abdominal masses need to be imaged (e.g. splenomegaly associated with a viral illness or leukemia, unless specific etiology, such as a Candida abscess, is sought).

Etiologies Neonatal (birth to 1 month) Renal (55%) + Hydronephrosis + Ureteropelvic junction (UPJ) obstruction + Posterior urethral valves + Vesicoureteric reflux + Ectopic ureterocele + Prunebelly syndrome + Ureterovesical junction obstruction + Renal ectopia + Polycystic kidney disease - Autosomal dominant - Autosomal recessive + Renal vein thrombosis + Mesoblastic nephroma + Wilms' tumor + Abscess

Etiologies Neonatal (birth to 1 month) Genital (15%) + Hydrometrocolpos + Ovarian mass + Simple cyst + Torsion + Teratoma Gastrointestinal (15%) + Duplication cyst +Volvulus + Complicated meconium ileus + Mesenteric/omental cyst + Bowel atresia with proximal cystic dilatation + Hypertrophic pyloric stenosis + Gastric teratoma

Etiologies Neonatal (birth to 1 month) Nonrenal retroperitoneal (10%) + Adrenal hemorrhage + Neuroblastoma + Teratoma + Rhabdomyosarcoma + Lymphangioma + Hemangioma + Lipoma + Anterior meningocele Hepatobiliary (5%) + Metastases + Hemangioendothelioma + Hepatoblastoma + Mesenchymal hamartoma + Simple cyst of the liver + Hematoma of the liver + Choledochal cyst + Hydrops of gallbladder

ALGORITMO MASAS ABDOMINALES

Caso Clínico (1) Initial AXR is unremarkable with a nonobstructive bowel gas pattern. Ultrasound examination shows a multicystic mass in the right renal fossa and a normal left kidney. Note that the cysts are not communicating with each other (unlike the hydronephrosis) and are arranged in a haphazard fashion (unlike hydronephrosis where calyces are radiating from the central renal pelvis).

Caso Clínico (2) Diagnosis is multicystic dysplastic kidney (MCDK). VCUG performed to exclude distal obstructive pathology and associated renal anomalies (higher prevalence) shows vesicoureteric reflux up the distal left ureter (grade 1 reflux). In this classic infundibulopelvic type of multicystic dysplastic kidney (MCDK), the ureter is atretic and there is absence of blood supply to the kidney.

Caso Clínico (3) Multicystic dysplastic kidney is one of the commonest causes for a neonatal abdominal mass. Bilateral involvement is incompatible with life, associated with severe pulmonary hypoplasia and maternal oligohydramnios. Most MCDK are left alone, and they often become smaller, although some remain the same size or even grow on follow up. If renal scintigraphy is performed, MCD kidney will show no uptake or excretory function.