SAT-778 - CKD-MBD on DXA Images A Tale of Two Sites

We present the case of a 75-year-old female patient with end-stage chronic kidney disease secondary to hypertension and partial right nephrectomy for clear-cell renal cell carcinoma (1998), status post living unrelated donor kidney transplant (2012), complicated by tertiary hyperparathyroidism status post subtotal parathyroidectomy (2014) followed by hungry bone disease. Other pertinent medical history includes: MGUS IgA Lambda, stage IV squamous cell carcinoma of left shoulder status post resection (2021) with known metastases to left axillary lymph node and bone (T12, T3, C4), coronary artery disease status post CABG (4 vessel) on 12/2018, PCIx3 (2020), MVR status post mitral clip (03/25), non-ischemic cardiomyopathy status post ICD implant (2010), and gout. The patient had a recent ICU admission with acute on chronic renal failure, non-STEMI and acute worsening of her EF by TTE (45% down to 20%). She resumed inpatient HD then proceeded to dialysis MWF. The patient is known to have osteoporosis by DXA criteria only, which was treated with Alendronate 70 mg every 2 weeks tapered to once monthly (2023-2025), then stopped recently after worsening renal function.
Estimated GFR by serum creatinine in 10/2025 based upon CKD-EPI 2021 (16 mL/min/1.73 m2) and Cystatin C (12 mL/min/1.73 m2) were comparable. Hb was 8.3 g/dL, albumin 2.8 g/dL indicating poor nutritional status. In 11/2025, repeat labs indicate worsening renal failure, (eGFR 8 mL/min/1.73 m2), acidosis (CO2 15 mmol/L), Ca 7.1 mg/dL, P 3.3 mg/dL, alkaline phosphatase 86 Units/L, PTH 33 pg/mL, 25(OH)D 32 ng/mL.
The first (baseline) DXA study (02/01/2023) showed lowest T-score at left forearm 1/3 radius (1/3R) site (-3.8), left total hip (TH) (-2.8), and L3-L4 (+1.1). Follow up DXA with the latest (11/05/2025) over 31 months showed the following changes as compared to the baseline study: L3-L4 -0.069 gm/cm2 (-5.6%) decline (least significant change [LSC] 0.024 gm/cm2), left TH -0.040 gm/cm2 (-6.8%) decline (LSC 0.020 gm/cm2, and left 1/3R site +0.043 gm/cm2 (+9.2%) increase (LSC 0.014 gm/cm2). Upon review of DXA images, there appears to be increasing vascular calcification shadows in both hip and forearm images as compared to baseline study images.
The lack of decline in the 1/3R site despite history of end-stage CKD in this patient can be attributed to the relative hypoparathyroid insufficiency following partial parathyroidectomy with sparing of the cortical bone rich 1/3R site. The differential effect of peripheral arterial calcification as part of the CKD-MBD syndrome on the BMD as a measurement artifact at the TH (decrease) and 1/3R (increase) with CKD progression and worsening ectopic peripheral arterial calcification. Peripheral arterial calcification can produce opposing DXA BMD artifacts depending on vessel location relative to the bone map (TH outside, 1/3R inside) and may explain discordant site trends in CKD-MBD.

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