Combined Multicystic Dysplastic Kidney and Ureteropelvic Junction Obstruction in a Child

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Description

A solitary kidney in a child represents a unique challenge in pediatric nephrology and urology, particularly when the contralateral kidney exhibits Ureteropelvic Junction (UPJ) obstruction. This rare combination underscores the critical importance of preserving renal function, preventing obstruction-related complications, and ensuring long-term health outcomes. The interplay between congenital anomalies, compensatory hypertrophy, and obstructive physiology can significantly influence both clinical presentation and management strategies. Understanding the pathophysiology, diagnostic considerations, and therapeutic options in this setting is essential for optimizing outcomes.

Congenital solitary kidney occurs either due to unilateral renal agenesis or severe dysplasia resulting in nonfunctioning renal tissue. The remaining kidney typically undergoes compensatory hypertrophy to meet the body’s metabolic and excretory demands. While many children with a solitary kidney maintain normal renal function throughout childhood, they remain at heightened risk for injury, hypertension, proteinuria, and chronic kidney disease if the functional unit is compromised. The presence of a contralateral ureteropelvic junction obstruction compounds these risks, as obstruction can lead to hydronephrosis, infection, and progressive parenchymal damage, potentially threatening the sole functional kidney if not addressed promptly.

UPJ obstruction is the most common congenital cause of hydronephrosis in children and results from impaired drainage at the junction between the renal pelvis and proximal ureter. The obstruction may be intrinsic, due to a stenotic segment or a peristaltic ureteral segment, or extrinsic, caused by aberrant crossing vessels, fibrous bands, or external compression. In children with a solitary kidney, the contralateral kidney’s UPJ obstruction may initially be asymptomatic, as the solitary kidney compensates for excretory function. However, over time, impaired drainage can cause renal pelvic dilatation, increased intrapelvic pressure, and progressive parenchymal atrophy. Chronic obstruction in this setting poses a unique threat because the solitary functional kidney bears the entire physiological burden; any insult, such as infection or calculi, can precipitate acute renal failure or accelerate long-term decline in function.

The diagnostic evaluation of this condition relies heavily on imaging. Ultrasonography is the first-line modality, allowing assessment of renal size, parenchymal thickness, and the degree of hydronephrosis. In the context of a solitary kidney, the functional unit typically appears hypertrophied, while the obstructed contralateral kidney, if present but hypoplastic, may demonstrate variable degrees of dilation and parenchymal thinning.

Pyeloplasty remains the standard surgical approach for UPJ obstruction in children, with the Anderson-Hynes dismembered technique widely used. Minimally invasive approaches, including laparoscopic or robot-assisted pyeloplasty, have gained popularity due to reduced postoperative pain, shorter hospital stay, and favorable long-term outcomes. The choice of approach must take into account the child’s age, anatomical considerations, and surgeon expertise. In some cases, temporary urinary diversion, such as a nephrostomy tube or ureteral stent, may be necessary in severely obstructed or infected kidneys prior to definitive repair. Careful perioperative monitoring of renal function is essential, particularly in children with a solitary kidney, as even transient reductions in renal perfusion can have significant consequences.

Long-term follow-up after intervention is critical, given the ongoing risk of renal deterioration. Serial ultrasonography and functional imaging are recommended to assess drainage, detect recurrent obstruction, and monitor compensatory hypertrophy in the solitary kidney. Blood pressure, serum creatinine, and urinary protein excretion should be monitored regularly to detect early signs of renal impairment. Families should be counselled regarding hydration, avoidance of nephrotoxins, and the importance of prompt evaluation of urinary tract infections. Pediatric patients with a solitary kidney and contralateral UPJ obstruction require lifelong surveillance, as progressive renal insufficiency or hypertension may manifest years after initial surgical repair.

The prognosis for children with a solitary kidney and contralateral UPJ obstruction depends primarily on early diagnosis, prompt relief of obstruction, and preservation of renal parenchyma. When intervention is timely, and the solitary kidney demonstrates good baseline function, long-term outcomes are generally favorable. Most children achieve normal growth, maintain near-normal renal function, and have a low risk of chronic kidney disease. Delays in diagnosis or management, however, can lead to permanent loss of renal function, recurrent infections, hypertension, and increased risk of chronic kidney disease later in life. Advances in prenatal imaging and minimally invasive surgery have substantially improved the prognosis for this population.

Conclusion

A solitary kidney with contralateral ureteropelvic junction obstruction in a child represents a rare but clinically significant challenge in pediatric urology. The combination of compensatory hypertrophy, obstructive physiology, and risk for infection necessitates careful monitoring, prompt diagnosis, and judicious surgical intervention. Functional imaging plays a pivotal role in guiding management, while minimally invasive surgical techniques provide effective relief of obstruction with low morbidity. Lifelong follow-up is essential to monitor renal function, prevent complications, and ensure optimal growth and development. With appropriate evaluation and management, children with this complex congenital scenario can achieve favorable long-term outcomes, maintain adequate renal function, and minimize the risk of chronic kidney disease.