Supernumerary kidney

Supernumerary kidneys are a rare congenital anomaly of the urogenital system, where there are one or two accessory kidneys.

Epidemiology

Less than 100 cases are documented. 

Clinical presentation

Patients may be asymptomatic. If present symptoms range from fever, pain to abdominal mass. These symptoms are mostly due to related renal pathology such as hydronephrosis, pyelonephritis, malignant tumors or calculus disease.

Associations

Urogenital anomalies such as fusion anomalies, ectopic ureteric opening, vaginal and uretral atresia, urethral or penile duplication. 

Non-urogenital anomalies such as coarctation of aorta, imperforate anus, ventricular septal defects and meningomyelocoele are also associated with supernumerary kidneys. 

Radiographic features 

Most of the kidneys are on the left and most often caudal to the native kidney. Mostly the accessory kidney is smaller in size with reduced excretion. Evaluation may be done by US, IVU, CT , MRI and Nuclear Medicine studies like DMSA and DTPA scans. US is useful in the morphological characterization while the rest aid in functional assessment.

Treatment and prognosis

Management is symptom based.  For asymptomatic patients regular USG follow up and USG with excretory function assessment is suggested if patient is symptomatic. 

Differential Diagnosis

• duplex kidney
• megapolycalycosis