Congenital anomalies of the kidney and urinary tract: Case

This infant has a right multicystic dysplastic kidney with a non-functioning right kidney on the DMSA scan and a grade 3 vesicoureteral reflux into the left, the solitary functioning kidney. The right multicystic dysplastic kidney is a parenchymal CAKUT, and the contralateral reflux into the left kidney is a common and important association, because the left kidney carries the entire renal function. The febrile urinary tract infection at 3 months reflects the reflux into the left kidney, and the prevention of further infection is the priority. [6]

Clinical findings

The key clinical findings are the non-functioning right multicystic dysplastic kidney, the grade 3 vesicoureteral reflux into the left kidney, the history of one febrile urinary tract infection, the normal blood pressure, the growth on the 25th centile, and the serum creatinine of 42 micromoles per litre. The DMSA scan confirms that the right kidney is non-functional and the left kidney has 100 percent of the total function with no cortical scarring, which is reassuring but places the entire renal burden on the refluxing left kidney. [5]

The differential for the contralateral anomaly in a child with a multicystic dysplastic kidney includes vesicoureteral reflux, which is the most common, a ureteropelvic junction obstruction, and renal hypoplasia. The MCUG has confirmed the grade 3 reflux, and the DMSA has shown no scarring in the left kidney. The serum creatinine is normal for age, but the long-term risk to the solitary functioning kidney is the central concern. [6]

Investigations and diagnosis

The diagnosis is a right multicystic dysplastic kidney with a contralateral grade 3 vesicoureteral reflux. The investigation pathway has been completed, with the postnatal ultrasound confirming the multicystic dysplastic kidney, the MCUG showing the grade 3 reflux into the left kidney, and the DMSA scan showing the non-functioning right kidney and the intact left kidney. The surveillance plan is to monitor the right kidney for involution by serial ultrasound, the left kidney for scarring by periodic DMSA scan, and the renal function by serial creatinine and blood pressure. [1]

Management and outcome

The management is conservative. The right multicystic dysplastic kidney is not removed, because Aslam and Watson showed that the majority involute over years and the risk of hypertension and malignancy is low, which is why the nephrectomy is no longer routine. The grade 3 vesicoureteral reflux into the left kidney is managed with prophylactic antibiotics, such as trimethoprim at 2 mg per kg at night, to prevent further febrile urinary tract infection and renal scarring, and the reflux is monitored for spontaneous resolution by periodic MCUG or by the alternative of a contrast-enhanced ultrasound. [6]

The long-term risk is the hyperfiltration injury in the left kidney, the solitary functioning kidney. Matsell and colleagues showed that the outcomes of a solitary functioning kidney from a multicystic dysplastic kidney differ from those of renal agenesis, and both groups need monitoring for hypertension, proteinuria, and a declining renal function. The surveillance includes the annual blood pressure, the annual urinalysis for proteinuria, and the periodic serum creatinine. An ACE inhibitor or an angiotensin receptor blocker is commenced if hypertension or proteinuria develops, to slow the hyperfiltration injury. [5]

The family is counselled on the diagnosis, the conservative management, the surveillance plan, and the long-term prognosis. The right multicystic dysplastic kidney is likely to involute and cause no further problem. The left kidney is the sole functioning kidney, and the grade 3 reflux increases the risk of infection and scarring, which is why the prophylactic antibiotics are maintained until the reflux resolves or is corrected. The long-term CKD risk is real but modest, and the child is expected to live a normal life with careful surveillance. The transition to adult nephrology care is planned in adolescence, because the CKD risk from CAKUT persists into adulthood, as highlighted by the registry data on paediatric CKD. [10]