Abdominal Masses

10.1055/b-0034-87872

Abdominal Masses

Imaging is essential in management of suspected abdominal masses. Data to be obtained are the composition of the mass (solid, cystic, or mixed), its limits, its location and organ dependence, its vascularization, and the presence of additional findings (lymphadenopathy, ascites, etc.). Afterward, an approximation about the nature of the mass (benign/malignant) and a possible differential diagnosis can be inferred. US is almost always the first imaging modality used, and can provide essential information. CT, MR, NM, and PET are useful to complete the diagnosis.

**Table 2.64 Neonatal cystic masses**
Diagnosis	Findings	Comments
Hydronephrosis	Depending if uni-/bilateral and on level of obstruction.	Most common mass in neonate. Usually diagnosed in utero.
Multicystic dysplastic kidney	Cluster of cysts in renal fossa In rare occasions may be focal.
Multilocular cystic nephroma	Noncommunicating cysts with thick septa.
Hydrometrocolpos Fig. 2.135a, b	Fluid-filled dilated vagina and uterus. In midline.	May be associated with other congenital anomalies.
Ovarian cyst	Lateral mass, usually unilocular.	May appear rather abdominal than pelvic.
GI duplication	Layered wall, with muscle.	May produce obstruction.
Mesenteric-omental cyst	Thin walled. Uni- or multilocular.
Meconium pseudocyst	Formed by twisted and fused loops of bowel.
Adrenal hemorrhage	Anechoic if subacute.	Decreases in size in serial controls.
Cystic neuroblastoma	Usually echogenic.	Equal or increasing in size.
Hepatic or splenic cyst	Unilocular. May be multiple.
Mesenchymal hamartoma of liver	Multiple rounded cystic areas, hypovascular.
Choledochal cyst	Usually located in or near the hepatic hilum.	NM can confirm the diagnosis.
Gallbladder hydrops	Usually biliary sludge and/or echogenic bilis is depicted on US examination.
Cystic hygroma/lymphangioma Fig. 2.136	Multilocular, thin wall, grows among other structures without displacing.
Sacrococcygeal teratoma	Mixed cystic-solid pattern.

**Fig. 2.135a, b Hydrometrocolpos.** A newborn with abdominal distension. (a) Plain film depicts a pelvic mass with intestinal loop displacement. (b) Sagittal pelvic US obtained after partial drainage shows a fluid-filled vagina and a uterus with mildly distended endometrial lumen, located behind the bladder.

**Fig. 2.136 Peritoneal lymphangioma.** Transverse US image in mesogastrium depicts a characteristic polylobulated cystic mass with thin septa.

**Table 2.65 Neonatal solid masses**
Diagnosis	Findings	Comments
Polycystic kidney disease	Bilateral enlarged distorted kidneys.	In autosomal recessive form.
Mesoblastic nephroma	Large ill-defined mass.	May be cystic.
Renal ectopia	Empty renal fossa.	Usually pelvic kidney or crossed-fused ectopia.
Renal vein thrombosis	Unilateral enlarged kidney with absent flow (acute phase), subsequent atrophy.	Secondary to dehydration, sepsis, umbilical vein catheterization.
Nephroblastomatosis-Wilms tumor	Large tumors unior multifocal and unior bilateral.	Most common solid renal mass in children.
Neuroblastoma	Large, heterogeneous, irregular mass. Adrenal, retroperitoneum, or other locations.	Good prognosis.
Hemangioendothelioma—hemangioma of liver	Diffuse mass affecting entire liver.	Benign tumor. Tendency to involute.
Hepatoblastoma	Large heterogeneous mass	Elevated alpha fetoprotein.

**Table 2.66 Older children cystic masses**
Diagnosis	Findings	Comments
Hydronephrosis
Renal cyst	Usually unilocular.	May be multiple.
Renal cystic disease	Usually bilateral and symmetric.	In autosomal dominant form.
Rhabdoid renal tumor	Mostly cystic.	Bad prognosis.
Perirenal hematoma	Post trauma or biopsy.
Teratoma Fig. 2.137a, b, p. 228	Mixed solid-cystic pattern.
Appendiceal abscess	Thick irregular wall.	May contain appendicolith.
Mesenteric-omental cyst	Unior multilocular.
Hepatic parasitic cyst	Well defined. Echinococcal cyst.
Cerebrospinal fluid pseudocyst	Cyst related with the tip of a catheter.	In patients with ventriculoperitoneal shunt.
Hepatic/renal/splenic cyst	Thin wall. Single or multiple.
Hepatic/renal/splenic abscess	Thick wall, irregular.
Hematometrocolpos	Midline, echogenic.	Girls in puberal age.
Urachal cyst/abscess	Midline, related to bladder dome and umbilicus.

**Fig. 2.137a, b Mature teratoma** in a 13-year-old girl. Sagittal (a) and transverse (b) US images show a complex cystic mass cranial to the uterus and positioned over the bladder with solid hyperechoic components representing fat and hairs, which was confirmed at pathologic examination.

**Table 2.67 Older children solid masses**
Diagnosis	Findings	Comments
Wilms tumor	Large tumor, hypervascular, heterogeneous. May invade IVC and cross midline.
Neuroblastoma	Adrenal, retroperitoneal, or in other locations. Irregular margins, heterogeneous, crosses midline, with retroperitoneal lymph nodes. Stippled calcifications.	Worst prognosis than in neonate. Two-thirds of patients > 2 y have disseminated disease.
Rhabdomyosarcoma	Lobulated solid soft-tissue masses, with local invasion, and nodal and distant metastases.	Usually genitourinary (bladder, prostate, vagina, cervix, paratesticular) or biliary.
Burkitt lymphoma	Rapidly growing infiltrative mass originated in ileal lymphoid follicles that extends to adjacent bowel mesentery.	Usually in boys between the ages of 5 and 10 y. May present as a small bowel obstruction or intussesception.
Hepatocellular carcinoma	Well-circumscribed mass with central scar and calcifications.	In older children. Fibrolamellar subtype.
Hepatic adenoma	Well-defined mass without arterial-phase enhancement.	Predisposed in children with von Gierke disease.
Hepatic metastasis	Multiple and solid nodules. Some cases: diffuse heterogeneous hepatomegaly.	From neuroblastoma or Wilms tumor.
Wandering spleen	Not really a tumor, but an unexpected abdominal mass.	May become infarcted if pedicle torsion occurs.