Case Quiz (January 2019)
A 10-year-old boy was admitted with a 3-month history of progressively worsening fatigue. He had been noted to be anemic 2 weeks prior to his hospitalization, with hemoglobin of 8.1 g/dL and was started on oral iron by his primary care pediatrician. Because of persistence of his symptoms, repeat laboratory testing was performed and showed his hemoglobin had decreased to 7.4 g/dL. His serum potassium was 7.2 mEq/L, serum bicarbonate was low at 14 mEq/L, and serum creatinine was elevated at 8.4 mg/dL. He was admitted to the pediatric intensive care unit where he received furosemide and sodium polystyrene. Studies to evaluate his renal disease included a renal ultrasound which revealed normal sized kidneys with bilateral grade 2 hydronephrosis without dilated ureters and with a distended, but thin-walled bladder; a voiding cystourethrogram showed no reflux and a normal urethra, but significant after void residual.
Other studies included serum complements C3 and C4, both of which were normal, hepatitis B and hepatitis C and HIV serologies that were all negative, and an antinuclear antibody that was also negative. His urinalysis had a low specific gravity of 1.006 with no blood or protein. He was urgently started on hemodialysis because of hyperkalemia and was maintained on outpatient hemodialysis three times a week at discharge, with a presumptive diagnosis of advanced CKD likely from a urologic cause.
Our patient underwent urodynamic studies which showed a normally compliant low-pressure bladder with complete bladder emptying. Even though he only had moderate hydronephrosis on ultrasound, due to the severity of his kidney disease, he underwent bilateral retrograde pyelograms which showed that both proximal ureters were somewhat medially deviated; the left proximal ureter had a 1 cm long narrow segment and the right proximal ureter had a 2 cm long narrowing. Double J ureteral stents were placed on both sides. Following stenting his urine output increased, and his renal function improved but only minimally, to a serum creatinine of 4 mg/dl. Due to a concern that the narrowing was from extrinsic ureteric compression, abdominal and pelvic CT scans were performed. On these scans, performed about 2 months after his initial renal ultrasound, both kidneys were noted to be very large. Renal biopsy was done.
Case Answer (January 2019)
Primary Renal Lymphoma (PRL) is a very rare disease entity with a reported incidence of 0.7% of all extranodal lymphomas. The tumor has been hypothesized to originate from mucosa-associated renal lymphoid tissue or from lymphatics in the renal capsule. Clinical presentations include palpable renal masses, hematuria, constitutional symptoms, hypertension, and acute kidney injury.
The etiology of the kidney disease was presumably mainly from infiltration of the renal parenchyma by the malignant cells with an added component of extrinsic compression of the proximal ureters by the intraparenchymal masses.
