A 12-year-old boy comes to the physician for the evaluation of intermittent blood-tinged urine for several months. Four months ago, he had an episode of fever and sore throat that resolved without treatment after 5 days. During the past 2 years, he has also had recurrent episodes of swelling of his face and feet. 5 years ago, he was diagnosed with mild bilateral sensorineural hearing loss. His brother died of a progressive kidney disease at the age of 23. The patient appears pale. His temperature is 37°C (98.6°F), pulse is 70/min, and blood pressure is 145/85 mm Hg. Slit lamp examination shows a conical protrusion of both lenses. Laboratory studies show a hemoglobin concentration of 11 g/dL, urea nitrogen concentration of 40 mg/dL, and creatinine concentration of 2.4 mg/dL. Urinalysis shows: Blood 2+ Protein 1+ RBC 5–7/hpf RBC casts rare Which of the following is the most likely underlying cause of this patient's symptoms?

Autosomal-recessive kidney disease

Type II hypersensitivity reaction

A 61-year-old man comes to the physician because of several episodes of dark urine over the past 2 weeks. He does not have dysuria or flank pain. He works in a factory that produces dyes. Since an accident at work 5 years ago, he has had moderate hearing loss bilaterally. He takes no medications. He has smoked a pack of cigarettes daily for 29 years and drinks one alcoholic beverage daily. Vital signs are within normal limits. Physical examination shows no abnormalities. His urine is pink; urinalysis shows 80 RBC/hpf but no WBCs. Cystoscopy shows a 3-cm mass in the bladder mucosa. The mass is resected. Pathologic examination shows an urothelial carcinoma with penetration into the muscular layer. An x-ray of the chest and a CT scan of the abdomen and pelvis with contrast show a normal upper urinary tract and normal lymph nodes. Which of the following is the most appropriate next step in management?

Transurethral resection of tumor with intravesical BCG instillation

Transurethral resection of tumor with intravesical chemotherapy

A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

"Can you tell me more about the symptoms you have been experiencing?"

"Does the diarrhea typically precede the constipation, or vice-versa?"

"Is the diarrhea foul-smelling?"

"Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"

"Are the symptoms worse in the morning or at night?"

A 7-month-old boy presents to the emergency room with three episodes of vomiting and severe abdominal pain that comes and goes for the past two hours. The patient's most recent vomit in the hospital appears bilious, and the patient had one stool that appears bloody and full of mucous. The mother explains that one stool at home appears to be "jelly-like." On physical exam, a palpable mass is felt in the right lower quadrant of the abdomen. What is the next best diagnostic test for this patient?

Kidney, ureter, bladder radiograph

Complete blood count with differential

A 4-week-old male presents with his parents to the pediatrician for a well-child visit. The patient’s mother reports that the patient was eating well until about one week ago, when he began vomiting after breastfeeding. His mother has tried increasing the frequency of feeds and decreasing the amount of each feed, but the vomiting seems to be getting worse. The patient now vomits after every feed. His mother states the vomitus looks like breastmilk. The patient’s mother is exclusively breastfeeding and would prefer not to switch to formula but worries that the patient is not getting the nutrition he needs. Two weeks ago, the patient was in the 75th percentile for weight and 70th for height. He is now in the 60th percentile for weight and 68th percentile for height. On physical exam, the patient has dry mucous membranes. His abdomen is soft and non-distended. Which of the following is the best next step in management?

Trial of empiric proton pump inhibitor

Supplement breastfeeding with formula

Wilms tumor for USMLE Step 1: High-Yield Pediatrics Lessons

Wilms Tumor - The Kidney Culprit

Most common renal malignancy in children, peaking at age 2-5 years.
Typically presents as a painless, unilateral abdominal mass found by a parent. May have hematuria or hypertension.
Associated with syndromes: WAGR, Denys-Drash, Beckwith-Wiedemann.
Classic histology is triphasic: blastemal, epithelial, and stromal elements.

⭐ Look for aniridia (absent iris) - it strongly suggests WAGR syndrome (Wilms, Aniridia, Genitourinary anomalies, Retardation).

Triphasic Wilms Tumor Histopathology

Gene Scene - Syndromic Links

WT1 Gene (11p13): Tumor suppressor gene deletion/mutation.
- WAGR Syndrome: 📌 Wilms tumor, Aniridia, Genitourinary anomalies, mental Retardation.
- Denys-Drash Syndrome (DDS): Wilms tumor, diffuse mesangial sclerosis → early renal failure, male pseudohermaphroditism.
WT2 Gene (11p15): Abnormal imprinting.
- Beckwith-Wiedemann Syndrome (BWS):
  - Hemihypertrophy, macroglossia, omphalocele, neonatal hypoglycemia.
  - Increased risk of hepatoblastoma & neuroblastoma.
  - ⭐ BWS is associated with ↑ risk of embryonal tumors, not just Wilms.

Clinical features of Beckwith-Wiedemann Syndrome

Clues & Confirmation - The Workup

Initial Test: Abdominal Ultrasound
- Differentiates cystic vs. solid mass.
- Assesses contralateral kidney & IVC for thrombus.
Investigation of Choice: CECT Abdomen & Pelvis
- Shows intra-renal origin (📌 Claw Sign).
- Stages the tumor, checks nodes, and vascular invasion.
Metastasis Screen: CT Chest (Lungs are #1 site).
Definitive Diagnosis: Histopathology (Post-nephrectomy or pre-chemo biopsy).
Labs: Urinalysis (hematuria), renal function tests. Genetic testing if syndromes suspected (e.g., WAGR).

⭐ CECT Finding: The "claw sign" - sharp angles formed by the tumor and normal renal parenchyma - confirms the intra-renal origin of the mass.

Wilms Tumor vs Neuroblastoma CT: Claw Sign

Staging & Story - Favorable vs. Foe

Based on the NWTS/COG staging system. Histology is the most critical prognostic factor, dividing tumors into two main stories.

Favorable Histology: Found in ~95% of cases. Shows classic triphasic pattern (blastemal, epithelial, stromal) and has an excellent prognosis.
Anaplastic Histology (Foe): Found in ~5%. Marked by extreme nuclear atypia (anaplasia) and linked to TP53 mutations. Carries a significantly poorer prognosis.

⭐ Lungs are the most common site for hematogenous metastasis in Wilms tumor.

The Takedown - Treatment Triumphs

Primary Goal: Complete tumor removal and prevention of recurrence using a multimodal strategy.
Surgery: Radical nephrectomy with lymph node sampling is standard.
Chemotherapy (Stage-Dependent):
- - Low Risk (Stage I/II, FH): Vincristine + Actinomycin-D.
- - High Risk (Stage III/IV, FH): Add Doxorubicin (VAD) ± Radiotherapy.
- - Anaplastic: Requires intensified chemotherapy.

⭐ SIOP vs. NWTSG: Key protocol difference. SIOP (Europe) uses pre-operative chemotherapy to downstage tumors before surgery. NWTSG (USA) proceeds with upfront surgery followed by chemotherapy.

Most common renal tumor of childhood, typically presenting at 2-5 years.

Associated with syndromes like WAGR, Denys-Drash, and Beckwith-Wiedemann.

Presents as a painless, palpable abdominal mass that does not cross the midline.

Do NOT palpate the abdomen deeply to prevent tumor rupture and spillage.

Histology is classically triphasic: blastemal, epithelial, and stromal elements.

Anaplasia is the single most important unfavorable prognostic factor.

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Wilms tumor