Renal pyramidal thickness predicts obstruction in patients with congenital non-refluxing megaureter
Angelena B. Edwards, MD, Claire Carmichael, B.S., Gina Lockwood, M.D,FAAP, Douglas Storm, M.D, FAAP, Christopher Cooper, M.D, FACS,FAAP.
University of Iowa, Iowa City, IA, USA.
BACKGROUND: Renal pyramidal thickness (PT) is a predictive factor of UPJ obstruction in children with congenital hydronephrosis. We assessed the predictive value of PT in children with congenital non-refluxing hydroureteronephrosis in terms of obstruction, relative renal function on MAG3 scan, and surgical intervention rates. METHODS: An IRB approved retrospective review of patients with hydroureteronephrosis diagnosed between 2007 and 2021 was conducted. Inclusion criteria required an initial renal ultrasound within the first 4 months of life, VCUG, and MAG 3 renography, with exclusion of patients with VUR or UPJ obstruction. 40 children met inclusion criteria with a total of 48 hydroureters (8 with bilateral hydroureteronephrosis, 6 with complete ureteral duplication, 3 with an associated ureterocele). The renal ultrasounds were independently reviewed to measure the renal PT of the mid-pole renal pyramid of the kidney with hydroureter and the contralateral non-hydronephrotic PT was also measured, as was the maximum ureteral diameter. RESULTS: The median age at initial ultrasound was 20 days (IQR 3-38.25) with a median PT of 2.27mm (IQR 1.82-2.75) in kidneys impacted by hydroureter (excluding bilateral involvement) compared to 5.63mm (IQR4.6- 6.38) in the contralateral kidney without hydroureter (p= <0.001). The median split renal function in patients with hydroureteronephrosis was 49% (IQR 46-54) on Mag 3 Scan at a median age of 42 days (IQR 32-55). 25 renal units underwent surgery at a median age of 109 days. Indications for surgery included progression of hydroureteronephrosis (20), worsening renal function (2), febrile UTI (2), and stone formation (1). The median PT on the initial ultrasound in those undergoing surgery was 2.01mm (IQR 1.69-2.64) in renal units with hydroureteronephrosis at a median age of 7 days of life (IQR 2.5-23) and 5.66mm (IQR 4.65-6.46) in the contralateral kidney without hydroureter (p= <0.001). On subsequent ultrasound at a median age of 82 days (IQR 44.5-127.75) prior to surgical intervention the median PT was 1.71mm (1.30-2.73) in kidneys with hydroureteronephrosis compared to 6.21mm (IQR 5.59-7.1) in normal contralateral renal units (p= <0.001). The initial ultrasound of all renal units with hydroureter (including individuals with bilateral hydroureteronephrosis) at a median of 5.5 days (IQR 2-23.5) had a median PT = 2.20mm (IQR 1.84-2.62) and those who underwent surgical intervention had a median PT 2.22mm (1.69-2.91) (p=0.44). However, on follow up imaging at a median age of 92 days (IQR 44.5-160) the PT in those undergoing surgical intervention was 1.83mm (IQR 1.34-2.95) compared to a PT of 2.87mm (IQR 2.35-3.59) in observed kidneys (p= 0.010). CONCLUSIONS: Similar to children with UPJ obstruction, PT < 3mm appears to be a significant risk factor for operative intervention in children with non-refluxing megaureter. In addition, a decreasing PT on serial ultrasound is also a risk factor for surgery. All renal units with PT>3 mm in our study had a preserved split renal function of >50%. Utilization of PT measurements may permit a more individualized risk-based management plan in children with non-refluxing hydroureteronephrosis.
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