A 15-year-old boy presents to his pediatrician after an appendectomy 1 week ago. The patient denies any abdominal pain, fevers, chills, nausea, vomiting, diarrhea, or constipation. He eats solids and drinks liquids without difficulty. He is back to playing basketball for his school team without any difficulty. His urine appears more amber than usual but he suspects dehydration. His temperature is 98.6°F (37°C), blood pressure is 110/70 mmHg, pulse is 76/min, and respirations are 15/min. His physical exam is unremarkable. The laparoscopic incision sites are all clean without erythema. The pediatrician orders a urinalysis, which is notable for the following. Urine: Epithelial cells: Scant Glucose: Negative Protein: 3+ WBC: 3/hpf Bacteria: None Leukocyte esterase: Negative Nitrites: Negative The patient is told to return in 3 days for a follow-up appointment; however, his urinalysis at that time is similar. Which of the following is the most appropriate next step in management?
CT scan abdomen and pelvis with contrast
Renal biopsy
Repeat urinalysis
Urine dipstick in the morning and in the afternoon
Urine dipstick in the morning and in the afternoon
This patient is found to have proteinuria on urinalysis in the absence of clinical symptoms or signs of nephrotic syndrome. Given the likely diagnosis of transient proteinuria, the most appropriate next step is to repeat the urine dipstick in the morning and in the afternoon.

Transient proteinuria can be due to febrile illnesses, seizures, strenuous exercise, emotional stress, serious illnesses like heart failure, and abdominal surgery. A detailed workup is not needed if the clinical story is clear, but an orthostatic test can be completed. One way to do this is to assess the urine dipstick in the morning and in the afternoon. Another way requires the patient to collect urine at multiple times throughout the day. A diagnosis is confirmed if the morning sample is protein-free but the evening sample contains protein. In general, pediatric patients with orthostatic proteinuria should have under 1 gram of protein in a full 24 hours. Treatment is with reassurance because this condition usually resolves by itself.

Ingold and Bhatt review the evidence regarding the diagnosis and treatment of orthostatic proteinuria in patients. They discuss how this condition is benign and typically occurs in adolescents. They recommend reassurance and supportive treatment.

Incorrect Answers:
Answer A: A CT scan of the abdomen and pelvis with contrast could assess for any anatomic obstruction and a possible post-renal cause of kidney dysfunction. It would be more prudent to obtain basic labs and a timed urinalysis before exposing a pediatric patient to radiation.

Answer B: Renal biopsy is indicated if the patient's clinical presentation is concerning for a glomerular or tubulointerstitial etiology for proteinuria. Patients will have edema, hematuria, or dysuria.

Answer C: Repeat urinalysis will not change the presence of proteinuria. Generally, a patient who has proteinuria should have a repeat urinalysis performed to rule out transient proteinuria. If the repeat urinalysis demonstrates proteinuria (as in this patient), then the diagnosis is unlikely to be transient proteinuria, and further workup is needed.

Answer E: Urine electrolytes and creatinine will assess the kidney's ability to concentrate urine and assess the etiology of acute kidney injury. Patients will present with oliguria or anuria.

Bullet Summary:
Consistent proteinuria in a child should by evaluated by performing a urinalysis in the morning and in the afternoon to see if proteinuria comes on toward the end of the day.