Abdominal Masses

  • Core 1 (Pre-Clerkship)
    • Biomedical Science
      • Anatomy and Imaging: The Para-Alimentary tract
      • Cancer Biology - What is cancer?
    • Integrative systems
      • MDTI - multiple myeloma & high-grade lymphoma
      • Reproduction - Ovarian cancer and pathology
      • Endocrinology - Adrenal Pathology
      • Renal - Uroepithelia Malignancy
  • Core 2 (Clerkship)
  • Core 3 (Post Clerkship) Electives that may further knowledge - Peds Oncology

  • Differential can often be stratified by age and location (see below) 
  • Associated symptoms can give you clues about the organ system involved 
    • Constipation (GI)? Hematuria (Urinary/Renal)? Hypertension (Adrenal/Renal)? Menstruation (Gyne)? Lymphadenopathy (Lymphoma)? 
    • Systemic/B-symptoms are more concerning for lymphoma/malignancy 
    • B symptoms: fever, night sweats, weight loss, pallor and loss of energy 
  • Rate of growth: fast growing/changing mass may be more suggestive of aggressive malignancy 
  • Family history may point to cancer syndrome and certain medical conditions may be associated with higher risk of certain cancers 

COMMON NEONATAL ABDOMINAL MASSES 

Organ  

Neoplasm? 

Condition 

Notes 

Kidney 

No 

Hydronephrosis 

MOST COMMON. Can be caused by vesicoureteral reflux, posterior urethral valves, and UPJ obstruction 

No 

Cystic kidney disease 

Multicystic dysplastic kidneys or ARPKD 

Yes 

Congenital Mesoblastic Nephroma 

Most common renal tumor in infants. Presents <3mo. 

Adrenal 

No 

Adrenal hemorrhage 

Usually diagnosed antenatally 

Yes 

Neuroblastoma 

Can rarely present in infancy 

Liver 

No 

Hemangioma 

Congenital – does not grow. Infantile – grows rapidly. 

Spleen 

No 

Splenomegaly 

Can be due to metabolic storage disorders 

GI 

No 

Duplication cyst 

Can appear anywhere in the GI tract 

Other 

No 

Traumatic hematoma 

From delivery. Adrenal, splenic, hepatic 

 

COMMON EARLY CHILDHOOD ABDOMINAL MASSES 

Organ  

Neoplasm? 

Condition 

Notes 

Kidney 

Yes 

Wilm’s Tumor 

Most common childhood renal tumor. Peak 2-5 years old. Associated with WAGR, Denys-Drash, Beckwith-Weidemann syndromes 

Yes 

Clear Cell Carcinoma 

Second most common childhood renal tumor. <4 years old. 

Adrenal 

Yes 

Neuroblastoma 

Most common infantile malignancy and most common extra-cranial solid tumor in children. Usually < 6yo. 

Yes 

Adrenocortical carcinoma 

Rare. <5yo. Usually metastatic on presentation w/ symptoms of steroid excess 

Liver 

Yes 

Hepatoblastoma 

<5yo. High AFP. 

GI 

No 

Constipation 

MOST COMMON. 

No 

Pyloric Stenosis 

Typically 1-2 months old 

No 

Intussusception 

Typically 4-36 months old 

No 

Choledochal cyst 

<2yo. Can also present with abdominal pain/jaundice 

Other 

Yes 

Burkitt Lymphoma 

Usually >6yo or adolescence 

 

COMMON LATE CHILDHOOD/ADOLESCENT ABDOMINAL MASSES 

Organ  

Neoplasm? 

Condition 

Notes 

Kidney 

Yes 

Renal Cell Carcinoma 

Most common adolescent renal tumor. More common than Wilm's >12yo 

Liver 

Yes 

Hepatocellular Carcinoma 

>10yo, usually with chronic liver disease/cirrhosis. AFP elevated. 

No 

Focal nodular hyperplasia 

Adolescent females have highest incidence 

Spleen 

No 

Splenomegaly 

Can be due to EBV/infections 

GI 

No 

Constipation 

MOST COMMON 

Genitourinary 

No 

Ovarian cysts 

 

No 

Imperforate hymen 

Presents around menarche 

No 

Pregnancy 

 

Yes 

Germ Cell tumor 

 

Yes 

Teratoma 

Usually benign 

Yes 

Rhabdomyosarcoma 

 

Other 

Yes 

Burkitt Lymphoma 

Usually >6yo or adolescence 

Yes 

Soft tissue sarcomas 

Can arise in the abdomen/peritoneum 

Adapted from: AAP and Uzunova 2018 

 

Evaluation

  • Abdominal ultrasound 
    • Non-invasive and can help to determine size, characteristics of mass, and organ involvement
  • Depending on the findings, additional imaging with CΤ, PET scan, or MRΙ may be warranted
  • Can consider pelvic/testicular ultrasound as well depending on differential 

Other testing for children presenting with abdominal mass 

Test 

Rationale 

CBC 

Low hemoglobin, platelets and/or white cell count may be an indicator of metastatic bone marrow involvement. May have very high leukocytosis in leukemia. 

PTT/PT/INR 

Deranged clotting is occasionally associated with Wilms tumor. 

Electrolyte Panel 

Elevated creatinine may be related to renal involvement/infiltration or postrenal obstruction by tumor. Elevated creatinine may also be seen in tumor lysis syndrome along with hyperkalemia. 

Calcium and phosphate 

Hypocalcemia and hyperphosphatemia are part of tumor lysis syndrome. High calcium can be seen in congenital mesoblastic nephroma and can also be a sign of paraneoplastic syndrome. 

Lactate dehydrogenase (LDH) 

High serum LDH is a sign of elevated cell turnover and is often substantially elevated in leukemia/lymphoma. 

Urine dipstick/UA 

Hematuria or proteinuria could be the presenting symptom in children with Wilm’s tumor or other renal tumors. 

Adapted from Uzunova 2018 

  • Narrow the differential by considering age, location, pre-disposing medical/family history, associated symptoms, and exam findings. 
    • Abdominal masses in newborns are primarily non-malignant renal masses 
  • Wilm’s tumor and neuroblastoma are the most common malignant causes of abdominal mass in childhood 
  • Primary GI tumors are rare to see in childhood, although Burkitt lymphoma can present in the GI tract. 
  • Hepatic masses represent 5-6% of childhood abdominal masses and are primarily malignant outside of the neonatal period 
  • Ultrasound is the best first-line test for inital evaluation of abdominal mass 

Click the drop down to reveal the correct answers

Q1: What is the best initial imaging modality for evaluating a pediatric abdominal mass?

Q2: What are the two most common malignant causes of abdominal mass in children?

Q3: How can you differentiate Wilms tumor and neuroblastoma on exam?

Q4: What is the most common mass in neonates?

Q5: Which syndromes are associated with Wilms tumor?

Q6: A 3-year-old presents with hematuria and an abdominal mass. What is the most likely diagnosis?

Q7: A male infant presents with abdominal pain, poor urinary output, and bilateral flank masses. What condition should be suspected?

Q8: A school-aged child has chronic abdominal pain and a palpable mass in the left lower quadrant. What is a common non-malignant cause?

Q9: A child presents with abdominal pain, weight loss, and night sweats, along with a palpable mass. What type of malignancy should be considered?

Q10: A child with known abdominal mass now presents with abdominal pain, pallor, bruising, and lab abnormalities (e.g., high uric acid, hyperkalemia). What emergency condition is developing?

Answers

Q1: Abdominal ultrasound.

  • Explanation: It's non-invasive, does not use radiation, and helps assess size, characteristics, and organ of origin. It’s the first-line imaging test. 

Q2: Wilms tumor and neuroblastoma. 

  • Explanation: Wilms is the most common renal tumor in children (peak age 2–5), while neuroblastoma is the most common extracranial solid tumor in children, often <6 years old. 

Q3: Wilms tumor will cross not cross midline whereas neuroblastoma will not 

Q4: Most commonly benign kidney mass - hydronephrosis

Q5: WAGR, Denys-Drash, and Beckwith-Wiedemann syndromes

Q6: Wilms tumor 

  • Explanation: Wilms tumor is the most common renal tumor in early childhood, typically presenting with a painless flank mass and sometimes hematuria.

Q7: Posterior urethral valves, which cause urinary obstruction and hydronephrosis. Ultrasound is used to diagnose.

Q8: Fecal mass due to chronic constipation—a frequent cause of abdominal pain in children.

Q9: Lymphoma (especially non-Hodgkin), which often presents with systemic “B symptoms” and abdominal lymphadenopathy.

Q10: Tumor lysis syndrome (TLS)—an oncologic emergency due to rapid breakdown of malignant cells.