Value of Mercaptoacetyltriglycine (MAG3) Scintigraphy in Functional Assessment of Kidney Transplant: A Case Study

Introduction: Post-renal transplant malfunctions, such as acute tubular necrosis (ATN), graft rejection, infection, and ischemic damage can be challenging to differentiate due to overlapping symptoms. Accurate diagnosis and management typically require multiple imaging modalities and biopsies. MAG-3 renal scintigraphy may offer complementary renal parenchymal function assessment. We present a case of a 33-year-old woman with a transplanted kidney with complications. MAG-3 scintigraphy provided meaningful functional corroboration of inferred ultrasound findings, with limited CT assessment. Case Description: A 33-year-old woman with a donor kidney transplant experienced recurrent urinary tract infections after transplant. During routine follow-ups, a renal biopsy showed borderline cellular rejection, treated with steroids. Progressive creatinine level increase warranted a full work up; imaging revealed mild hydronephrosis, and cystoscopy was suggestive of vesicoureteral reflux. A renal biopsy showed mesangial expansion without recurrent rejection. Functional assessment with MAG-3 scintigraphy revealed regional abnormality in the lower half of the kidney, suggesting regional dysfunction. A contemporaneous ultrasound demonstrated elevated regional resistive index in the lower pole, corroborating the regional dysfunction. Discussion: This case shows value of MAG-3 scintigraphy in functional assessment of kidney transplants. A regional abnormality such as in this case is atypical, and can point to uncommon underlying pathology, such as infection or traumatic/iatrogenic vascular insult and not ATN. Scintigraphy can yield a more expansive differential diagnosis and is complementary to other modalities such as US.