Ultrasound for monitoring different stages of post-transplant lymphoproliferative disorder in a transplanted kidney: A case report and review of the literature

Abstract

Rationale: Post-transplant lymphoproliferative disorder (PTLD) is a well-recognized, but uncommon complication in patients with kidney transplantation, which poses challenges in diagnosis and poor prognosis due to its low incidence and nonspecific clinical manifestations. As a routine follow-up examination method for kidney transplant patients, ultrasound (US) plays a significant role in the diagnosis of PTLD. Therefore, it is critical to evaluate the ultrasonic characteristics of PTLD in transplanted kidney patients for early detection and diagnosis.

Patient concerns: A 59-year-old female patient was unexpectedly found with a mass in the hilum of the transplanted kidney 12th month after transplantation, which gradually grew up in the following 4 months. The latest US examination found hydronephrosis. Contrast-enhanced ultrasound (CEUS) demonstrated a hypo-enhancement pattern in arterial and parenchymal phases and showed a new irregular area lacking perceivable intensification within the mass, which was considered necrosis. Meanwhile, the patient developed an acute increase in serum creatinine from 122 to 195 μmol/L.

Diagnosis: A US-guided biopsy was conducted with the final pathological diagnosis of PTLD (polymorphic).

Interventions: After receiving 3 times of rituximab and symptomatic treatment, blood creatinine returned to normal but the mass was still progressing in the patient. Therefore, the treatment approach was modified to immune-chemotherapy.

Outcomes: The patient was in a stable condition to date.

Lessons: PTLD is a rare complication in a transplanted kidney. US and CEUS are the preferred imaging methods in renal transplant patients due to their good repeatability and no nephrotoxicity. This case demonstrates that continuous dynamic monitoring by using US and CEUS has significant value in the detection and diagnosis of PTLD in a transplanted kidney, suggesting early clinical intervention to avoid further progression.

Figure 1.

B-mode ultrasound (US) and Color Doppler flow imaging (CDFI) of the patient. (A) B-mode US and CDFI images demonstrated a poorly defined, hypovascular mass (arrows) in the hilum of the transplanted kidney. The size of the mass gradually enlarged, and the internal echo gradually decreased from isoechoic to heterogeneous (hypoechoic mainly) during the 3 examinations. (B) Hydronephrosis in the transplanted kidney. (C) The contrast peak intensity of the mass, renal parenchyma, and surrounding soft tissue separately. The contrast peak intensity in the mass was lower than that in the parenchyma and it was markedly increased in the examination of March 2023. No significant difference was found between the mass and the soft tissue in the first 2 examinations. CDFI = Color Doppler flow imaging.

Figure 2.

Contrast-enhanced ultrasound (CEUS) of the patient. The CEUS examinations in October and November 2022 showed the mass exhibited a centripetal hypo-enhancement pattern. The examination in March 2023 showed an increase in contrast intensity of the mass but still manifested the hypo-enhancement pattern, and a new irregular area lacking perceivable intensification within the mass.

Figure 3.

Pathological findings of US-guided biopsy. Hematoxylin and eosin staining revealed diffuse infiltration of atypical lymphoid cells. (40 ×). US = ultrasound.

Figure 4.

¹⁸F-FDG PET/CT of the patient after 3 times of rituximab treatment. CT scan showed the transplanted kidney was enlarged and swollen, and the cortex was thickened. Multiple poorly circumscribed and irregular low-density shadows were observed in the renal allografts. (A) ¹⁸F-FDG PET MIP image shows a quantity of intense uptake in the right lower quadrant (SUVmax = 15.7). The B1, C1, and D1 (PET), B2, C2, and D2 (CT), and B3, C3, and D3 (fused PET/CT) showed multiple abnormal FDG-avid lesions in the transplanted kidney (arrows) in axial, sagittal and coronal sections separately. No other significant abnormal FDG-avid lesion is observed in the rest PET study of the entire body (including the brain).