Authors: Pak-Kan Tang, Rebecca F Geddes, Yu-Mei Chang, Rosanne E Jepson, Dirk Hendrik Nicolaas van den Broek, Nicola Lötter, Jonathan Elliott
Vet Intern Med. 2024 May-Jun;38(3):1553-1562.
doi: 10.1111/jvim.17011
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Identification of nephrocalcinosis in cats with chronic kidney disease (CKD) is of clinical interest but the ability of ultrasonography to detect nephrocalcinosis is uncertain.
To compare ultrasonography, micro-computed tomography (μCT) and histopathology for identification of nephrocalcinosis.
Twelve kidneys from 7 euthyroid client-owned cats with CKD.
Descriptive study. Renal ultrasonography was performed ante-mortem for nephrocalcinosis detection. Kidneys were grouped based on nephrocalcinosis: present, suspected, or absent. When cats died, necropsy was performed. Renal tissue was evaluated using μCT for macroscopic nephrocalcinosis, and nephrocalcinosis volume-to-kidney tissue ratio (macro-VN:KT) and sagittal nephrocalcinosis area-to-kidney tissue ratio (macro-AN:KT) were calculated. Each kidney subsequently was bisected longitudinally, formalin-fixed, and paraffin-embedded for microscopic nephrocalcinosis assessment using von Kossa and Alizarin red staining with AN:KT (VK-micro-AN:KT and AR-micro-AN:KT) quantified using ImageJ. Data are presented as median (range). Relationships between macroscopic and microscopic AN:KT were assessed using Spearman's correlation.
Nephrocalcinosis by ultrasonography was considered to be absent in 3, suspected in 3, and present in 5 kidneys; 1 kidney had nephrolithiasis with nephrocalcinosis. The macro-VN:KT was 0.001%, 0.001%, and 0.019%, and the macro-AN:KT was 0.08%, 0.30%, and 1.47%, respectively. Histologically, VK-micro-AN:KT was 0.21%, 2.85%, and 4.56%, and AR-micro-AN:KT was 1.73%, 5.82%, and 8.90% for kidneys where ultrasonographic macro-nephrocalcinosis was absent, suspected, or present, respectively. A strong correlation was identified between macroscopic (macro-AN:KT) and microscopic (VK-micro-AN:KT) nephrocalcinosis (rs = 0.76; P = .01).
Ultrasonographically diagnosed nephrocalcinosis correlates well with macroscopic and microscopic nephrocalcinosis at necropsy despite their separation in time.