Nuclear Renogram as Part of Diagnostic Scan for Nephroptosis

Introduction: Nephroptosis, or renal ptosis, is an uncommon condition in which a patient develops flank pain after being erect for greater than 20-30 minutes due to one or both kidneys dropping below their correct position in the abdomen. The condition has been traditionally defined if a kidney descends >2 vertebral bodies (or >5 cm) during a position change from supine to upright. Currently, the gold standard for diagnosing this condition is visual descent seen on intravenous pyelograms (IVP). Patients with severe symptoms can be offered laparoscopic or robotic nephropexy to fixate the kidney in its cranial-most, undescended position.

Methods: We performed nuclear renogram for all of our patients with suspected nephroptosis in addition to the IVP. The scan was performed in 2 phases: routine nuclear renogram was performed with 10 mCi of Tc-99m MAG3 obtaining flow, function and post void images (no Lasix); then another scan was performed with 20 mCi of Tc-99m MAG3, with patient being imaged in an erect position to see the difference in function and location of the kidneys. An anterior iliac crest hot Co-57 source marker was used throughout the duration of the scans to help with the localization of the kidneys and maintain consistency of the scan positions. In addition, a 14cm lead marker was used to show the size.

Results: We retrospectively identified four patients who presented to our institution between January 2019 and December 2022 with concern for nephroptosis who underwent both clinical and imaging evaluation. The diagnosis of nephroptosis was made via collaborative review of the cases by IVP of radiology, renogram of nuclear medicine and urology (see Figures 1-4). Nuclear renogram was helpful in identifying the descent of the kidney between supine and upright positions.

Conclusions: We propose to add nuclear renogram in the evaluation of Nephroptosis. Renal scintigraphy is a valuable tool in the evaluation of patients with suspected nephroptosis. Renal scintigraphy can provide anatomic information similar to intravenous pyelography with the benefit of providing additional functional information, which may aid urologists in selecting patients for treatment who have a history of chronic flank pain with normal, supine-only imaging work-up. The protocol needs to be optimized and standardized, markers need to be used for location and measurement. We also propose to use a Co-57 ruler overlay to calibrate the measurements. Further study is needed to validate this protocol for implementation into routine clinical practice.

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