Supernumerary kidney

Last revised by Dr Daniel J Bell on 11 Sep 2021

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

Less than 100 cases have been documented in the medical literature.

Many conditions have been found to be associated with supernumerary kidneys including:

Patients may be asymptomatic. If present, symptoms may encompass fever, pain and an abdominal mass. These symptoms are mostly due to related renal pathology such as hydronephrosis, pyelonephritis, malignant tumors or calculi.

Most of the supernumerary kidneys are on the left and usually caudal to the native kidney. Mostly the accessory kidney is smaller in size with reduced excretion. Evaluation may be done by ultrasound, IVU, CT , MRI and nuclear medicine studies like DMSA and DTPA scans. Ultrasound is useful in the morphological characterization whilst the rest aid in functional assessment.

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

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Cases and figures

  • Case 1: supernumerary kidney
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  • Case 2: Supernumerary kidney
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