Renal agenesis and multicystic dysplastic kidney (MCDK) are usually associated with either an absent or atretic ureter. Occasionally, these renal anomalies may be associated with a dilated tortuous ureter, ureterocele or other cystic malformation of mesonephric duct (MND) remnants.
The objective of this study was to identify and classify anatomical variants of tubulocystic remnants of the MND, with a secondary focus on natural history and management outcomes.
A retrospective cohort study of patients seen in the study institution between 2007 and 2014 with a tubulocystic abnormality of MND structures associated with either MCDK or renal agenesis was conducted. Medical imaging and progress notes were reviewed for all patients. Data collected included anatomical information, surgical intervention, histology and outcomes of both conservatively managed and surgically resected MND remnant structures.
Nineteen patients were identified, 5 girls and 14 boys. Median age at presentation was 4.6 years. Anomalies of the MND occurred on the left in 9 patients and on the right in 10 patients. Mean follow-up was 3.4 years. Patients fell into 3 distinct anatomical groups: Type I, including orthotopic remnants corresponding to ureteric bud structures (ureter and trigone); Type II, including ectopic MND remnants of ureteric bud structures, and Type III, including complex remnants corresponding to MND structures other than those from ureteric bud (vas, epididymis and seminal vesicles). Anomalies of structures arising from urogenital sinus and paramesonephric ducts were also identified. Most patients were asymptomatic and successfully managed conservatively. Transvesical puncture of trigonal cysts provided effective decompression in 5 patients. Partial or complete MCDK regression was seen in 7 patients, whereas MND cystic anomalies did not regress spontaneously.
When MND tubulocystic structures persist along with renal agenesis or MCDK, most arise from ureteric bud structures in an orthotopic position as a ureterocele with or without a blind-ending ureter-like structure. Less commonly, ureteric bud structures insert ectopically into the urogenital tract, or tubulocystic structures arising from the remainder of the MND occur. Embryogenesis of other urogenital structures may also be abnormal, and conditions such as Zinner syndrome and obstructed hemivagina and ipsilateral renal agenesis syndrome should be considered.
Complications are uncommon, and surgical intervention should be limited to symptomatic patients. Remnants of metanephric blastema may involute, but MND remnants persist.