Objectives: To compare the distinction of tissue layers of porcine ureters ex vivo between optical coherence tomography (OCT) and endoluminal ultrasonography (ELUS). Catheter-guided OCT is a new method of intraluminal microstructural imaging, with a spatial resolution of 10-20 mum.
Methods: Porcine ureters and kidneys were obtained fresh from the municipal slaughtery, cannulated with a 7F catheter sheath, flushed with normal saline solution, and marked on the outside with surgical suture. Between the marked positions, images were obtained from within the ureter lumen using OCT (M1, Lightlab, Westport, MA) and ELUS at 40 MHz. The distinction of the urothelium, lamina propria, and inner and outer muscle layers was rated as possible (1) or impossible (0) by 2 independent observers (O1, O2). The rates of distinction were compared between OCT and ELUS image quadrants using the chi(2) test.
Results: Of the 224 OCT image quadrants and 144 ELUS image quadrants, OCT was superior to ELUS in the distinction of any wall layers (O1, chi(2)P = 68.1051, P < .001; O2, chi(2)P = 66.1630, P < .001), urothelium and lamina propria (O1, chi(2)P = 200.0750, P < .001; O2, chi(2)P = 240.0024, P < .001), and lamina propria and muscle layer (O1, chi(2)P = 38.8411, P < .001; O2, chi(2)P = 24.7536, P < .001) but was inconclusive for the inner and outer muscle layer (O1, chi(2)P = 260.3004, P < .001; O2, chi(2)P = 0.4992, P > .25).
Conclusions: OCT was able to distinguish significantly better than ELUS between different wall layers of porcine ureter ex vivo. The feasibility of OCT in vivo and in the presence of pathologic wall thickening of the ureter remains to be demonstrated.