A rare pediatric case of grossly dilated ureter presenting as abdominal mass

An 8-year-old male child presented with pain abdomen, not localizing to any side since 1 week and palpable abdominal mass noticed since 2 days. The patient was sent for routine blood investigations, ultrasonography (USG), and renal dynamic scan. USG showed bilateral enlarged kidneys with hydroureteronephrosis and thin parenchyma. The left ureter (LU) was grossly dilated. The patient underwent technetium-99m ethylene cysteine (Tc-99m EC) scan. The right kidney (RK) was enlarged with reduced perfusion and radiotracer uptake showing obstructive drainage pattern and dilated tortuous ureter [Figure 1]. The left kidney (LK) appeared smaller in size compared to RK on renal scan contrary to USG findings; hence, the possibility of duplex system in LK was raised with good functioning nonobstructed upper moiety and nonfunctioning lower moiety showing no radiotracer uptake until the end of the study. As the doubt about left duplex system was raised on Tc-99m EC scan, with no such mention in USG report, the patient was scheduled for MR urography.

Patient underwent magnetic resonance (MR) urography on subsequent day and images showed duplicated collecting system of the left kidney. The upper moiety showed normal pelvi-calyceal system and ureter of the upper moiety while the lower moiety showed gross hydronephrosis with thinned out renal parenchyma and markedly dilated and tortuous ureter until the lower end [Figure 2]. The RK was hydronephrotic with reduced parenchymal thickness and showing dilated, tortuous, kinked right ureter until the lower end where it was being externally compressed by dilated left ureter. The patient underwent left lower pole hemi-nephrectomy[1] for the nonfunctioning lower moiety [Figure 3]. Postoperatively, the patient is doing well.

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Figure 1 Technetium-99m Ethylene cysteine (Tc-99m EC) scan of patient performed after intravenous injection of 3 mCi of Tc-99m EC and 10mg of Lasix as F+0 protocol. The dynamic images were acquired till 20 minutes followed by post-void and delayed static image till 2 hours. It showed enlarged right kidney with good perfusion and radiotracer uptake and obstructive drainage pattern. The right ureter was dilated and tortuous in its course. The left kidney appeared smaller in size compared to right kidney contrary to USG findings which showed bilateral enlarged kidneys. Possibility of left duplex system was raised with upper moiety showing good function and non-obstructed drainage and non-functioning lower moiety with no radiotracer uptake till the end of the study. The other causes of this discrepancy in size on renal scan and USG can be renal cyst, benign or malignant mass and renal calculi. The problem in diagnosis of renal masses is common on USG[5]

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Figure 2 MR Urography - T2 weighted images showing duplicated collecting system of the left kidney. The left upper moiety (LUM) showed normal pelvicalyceal system and ureter. The lower moiety was grossly hydronephrotic showing thinned out renal parenchyma and markedly dilated and tortuous ureter (LU) till the lower end. The right kidney (RK) showed marked hydronephrosis with reduced parenchymal thickness (4.7mm) and dilated, tortuous right ureter (RU) till lower end. The right ureter showed kinking in its path with external compression by dilated left ureter at lower end. The Urinary bladder (UB) was normally distended and indented on the superior surface by the dilated left ureter. So MR urography confirmed left duplex system and showed grossly dilated left ureter as the cause of palpable abdominal mass. It also showed that the hydronephrosis in right kidney was most likely due to tortuosity of right ureter and pressure of dilated left ureter on the lower third of right ureter

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Figure 3 Per-operative image during left lower pole hemi-nephrectomy, showing grossly dilated left ureter (decompressed). Post-operatively patient is doing well

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Renal masses account for 55% of cases presenting as a palpable abdominal mass in children.[2] In our case, as USG did not mention about duplex system in its report, but Tc-99m EC scan suggested left duplex system due to discrepancy in left kidney size when compared to USG, the patient was scheduled for MR urography. MR urography confirmed left side duplex system and showed grossly dilated LU as the cause of palpable abdominal mass. It also showed that the hydronephrosis in RK with tortuous RU was likely due to the pressure of dilated LU on the lower third of RU. In case of discrepancy in the size of the kidney on USG and renal scan, duplex kidney should be considered as differential, other causes being, renal cyst, benign/malignant mass and renal calculi. However, most of these causes can be differentiated on USG. Gross hydro-ureter presenting as palpable abdominal mass is very rare with few reported cases.[345] The problem in the diagnosis of renal masses is common on USG.[6]