🎗️ Chapter 17: Abdominal Masses

Nelson's Pediatric Symptom-Based Diagnosis | Wilms Tumor · Neuroblastoma · Hepatoblastoma · Splenomegaly · Ovarian Cyst · Hydronephrosis · Teratoma

🔍 Abdominal Masses in Children: Key Concepts

📊 Common Masses by Age
Neonate: hydronephrosis, multicystic dysplastic kidney, neuroblastoma, mesoblastic nephroma. Infant (0-1y): Wilms, neuroblastoma, hepatoblastoma, hydronephrosis. Child (2-10y): Wilms, neuroblastoma, lymphoma, hepatoblastoma. Adolescent: ovarian tumors, lymphoma, IBD mass.
🔄 Wilms Tumor (Nephroblastoma)
Age 2-5 years. Smooth, non-tender flank mass, rarely crosses midline. Associated: aniridia, hemihypertrophy, Beckwith-Wiedemann, WT1/WT2 mutations. AFP not elevated. Treatment: nephrectomy + chemotherapy.
⚠️ Neuroblastoma
Age <5 years (median 2y). Firm, irregular, crosses midline. Retroperitoneal, may have intraspinal extension. Elevated urinary catecholamines (VMA, HVA). MYCN amplification poor prognosis. Can present with opsoclonus-myoclonus.
💧 Hepatoblastoma
Age <3 years. Right upper quadrant mass, elevated AFP (80-90%). Associated: Beckwith-Wiedemann, familial adenomatous polyposis. Treatment: resection + chemotherapy.
🧬 Splenomegaly
Most common cause of left upper quadrant mass. Causes: infection (EBV, CMV), portal hypertension, hemolytic anemia, storage diseases, leukemia/lymphoma. Palpable notch distinguishes from kidney.
🚩 Red Flags in Abdominal Mass
Hematuria (Wilms), hypertension (Wilms, neuroblastoma), opsoclonus-myoclonus (neuroblastoma), metastasis (bone pain, proptosis), failure to thrive, fever, night sweats.

💡 Key Takeaway: Ultrasound is first-line to differentiate solid vs cystic. Wilms tumor is smooth, does not cross midline. Neuroblastoma is irregular, crosses midline, and may have calcifications. AFP elevated in hepatoblastoma, not in Wilms.

🩺 Clinical Approach to Abdominal Masses: Step-by-Step Algorithm

🔹 Step 1: Localize the mass by quadrant
• RUQ: hepatomegaly (tumor, storage), choledochal cyst.
• LUQ: splenomegaly (most common), kidney mass, neuroblastoma.
• Flank: Wilms tumor, hydronephrosis, multicystic dysplastic kidney.
• Midline: neuroblastoma (crosses midline), bladder distention, omental/mesenteric cyst.
• Pelvis: ovarian cyst/tumor, pregnancy, hydrometrocolpos, rhabdomyosarcoma.
🔹 Step 2: Distinguish solid from cystic (ultrasound)
• Solid: Wilms, neuroblastoma, hepatoblastoma, lymphoma, sarcoma.
• Cystic: hydronephrosis, ovarian cyst, mesenteric cyst, choledochal cyst, duplication cyst.
• Complex cystic-solid: teratoma, Wilms with cystic change, abscess.
🔹 Step 3: Age-based differential
• Neonate: hydronephrosis (most common), multicystic dysplastic kidney, mesoblastic nephroma, neuroblastoma.
• Infant (1-12m): neuroblastoma, Wilms, hepatoblastoma, hydronephrosis.
• Child (1-10y): Wilms (most common primary renal malignancy), neuroblastoma, lymphoma, hepatoblastoma.
• Adolescent: ovarian tumors, lymphoma, IBD-related mass.
🔹 Step 4: Key diagnostic tests
• Ultrasound: first-line, distinguishes solid vs cystic, vascularity.
• CT/MRI: surgical planning, metastasis, vascular involvement.
• Urinary catecholamines (VMA, HVA): neuroblastoma.
• AFP: hepatoblastoma (elevated), yolk sac tumor.
• hCG: germ cell tumor.
• CBC: leukemia, lymphoma, infection.
🔹 Step 5: Red flags requiring urgent referral
• Rapidly enlarging mass, metastasis (bone pain, proptosis), paraneoplastic syndromes (opsoclonus-myoclonus, hypertension).
• Wilms: can extend into renal vein/IVC → pulmonary embolism.
• Neuroblastoma: can cause spinal cord compression.