P3.N265: Nephroptosis – a rare but potentially serious complication in renal transplant recipients

Introduction: The accepted standard treatment for end-stage renal disease is kidney transplantation. The typical post-operative course involves pain management and initiation of immunosuppressive therapies to prevent organ rejection. Patients are then monitored for potential renal dysfunction with frequent outpatient visits and any change to the patient’s creatinine needs to be evaluated thoroughly. Common reasons for changes in kidney function include acute rejection, infection, and dehydration; however, rare causes, depending on clinical presentation, need to be included in the differential diagnosis.

Case Description: An 18-year-old male patient underwent deceased donor kidney transplantation secondary to an unspecified glomerulonephritis. Delayed graft function and concerns of vascular pathology lead to placement of the kidney from the extra- to the intraperitoneal space after graft exploration. Several weeks after his second surgery, he presented to the transplant clinic with an unexplained rise in serum creatinine from a baseline of 1.8 mg/dl to 11 mg/dl within 5 days. He had also experienced mild diarrhea and some weight loss and evaluations for other causes of renal dysfunction were negative. With IVF and rest, his creatinine returned to baseline. Two additional and similar episodes of unexplained AKI occurred later on and ultimately, the patient was diagnosed with nephroptosis by renal doppler ultrasound in supine and standing position and rising creatinine by serial measurements after 3 days of walking. He was taken to surgery for nephropexy of his transplanted kidney to the abdominal wall to correct his nephroptosis with now stable renal function weeks after transplantation.

Discussion: Nephroptosis is a rare and potentially serious post-transplant complication with downward displacement of a kidney upon standing that can cause vascular flow impairment to the kidney. In adolescent and adult transplant patients, the transplanted kidney is placed extraperitoneal. In infants and children, the transplanted kidney is placed intraperitoneally and typically does not have room to move as the close proximity of surrounding structures limit excessive mobility. In this patient, we postulate that intraperitoneal placement provided more space for graft movement leading to the nephroptosis.

Conclusion: While nephroptosis is an extremely rare post-transplant complication, it is important to include it in the list of differential diagnoses in patients with unexplained rise in serum creatinine.