On Tuesday afternoon, a five-month-old girl was referred to the emergency department for evaluation of intermittent fevers (103.8) and lethargy. On physical examination, she had a rectal temperature of 99.8, pulse 129, respiratory rate 40, and weight of 6.9 kilograms. Her chest was clear and the abdominal exam was unremarkable. The white blood count was 18.5. The differential was 35% polys, 16% bands, 47% lymphocytes and 1% monocytes. Urinalysis was cloudy with a specific gravity of 1.009, 3 to 5 red blood cells, more than 100 white blood cells, and moderate bacteria.
The infant was admitted for fever workup with laboratory studies suggestive of a urinary tract infection and possible pyelonephritis. The urine culture grew out E coli and the infant was started on intravenous Ampicillin and Gentamycin. A renal ultrasound to rule out hydronephrosis was ordered. During the night, the child spiked a temperature of 102 and was given Tylenol with good effect.
At 9:00 a.m. Wednesday, the renal ultrasound revealed a 2x2 cm mass in the upper pole of her right kidney. According to the radiologist, the location and appearance of the lesion—as well as the age of the patient—made it suspicious for a Wilms' tumor. A progress note written by a pediatric resident listed the primary diagnosis as "UTI/pyelonephritis and renal mass."
The attending pediatrician reviewed the abdominal CT scan with the radiologist and confirmed the finding of a right renal intraparenchymal mass, and no clear adenopathy (a chest CT scan was negative). The differential diagnoses remained Wilms' tumor, possible mesoblastic nephroma. The plan was to continue antibiotics and obtain a surgery consult for a right nephrectomy.
Later in the day, the pediatric surgeon evaluated the infant and his differential diagnoses included a small Wilms' tumor and a mesoblastic nephroma. The parents were told that their daughter had a Wilm's tumor, and they consented to an surgery. This was scheduled the next day for either a heminephrectomy or a complete nephrectomy.
At 8:00 p.m., repeat urinalysis was clear with specific gravity of 1.014, no red blood cells, 0-2 white blood cells, and few bacteria. The white blood cell count was 11.2 and the infant was afebrile.
Thursday morning, the patient was taken to the operating room for a possible nephrectomy. According to the operative report, "the right kidney was palpated and had only a subtle enlargement near the upper pole anteriorly just above the mid-portion. After the kidney was mobilized, once again it was palpated and there was no definitive mass that could be felt." The kidney was removed and sent off for frozen section. The patient's pain was well controlled and her temperature was at normal levels during the postoperative period.
According to the final pathology report, the right kidney had acute and chronic pyelonephritis (acute lobar nephronia, severe with perinephrenic fat extension). This kidney lesion is commonly associated with reflux infection of E. coli which was cultured in the urine of this patient. There was no evidence of malignancy.