Intraluminal measurement of papillary duct urine pH, in vivo: a pilot study in the swine kidney

Abstract

We describe the in vivo use of an optic-chemo microsensor to measure intraluminal papillary duct urine pH in a large mammal. Fiber-optic pH microsensors have a tip diameter of 140-µm that allows insertion into papillary Bellini ducts to measure tubule urine proton concentration. Anesthetized adult pigs underwent percutaneous nephrolithotomy to access the lower pole of the urinary collecting system. A flexible nephroscope was advanced towards an upper pole papilla with the fiber-optic microsensor contained within the working channel. The microsensor was then carefully inserted into Bellini ducts to measure tubule urine pH in real time. We successfully recorded tubule urine pH values in five papillary ducts from three pigs (1 farm pig and 2 metabolic syndrome Ossabaw pigs). Our results demonstrate that optical microsensor technology can be used to measure intraluminal urine pH in real time in a living large mammal. This opens the possibility for application of this optical pH sensing technology in nephrolithiasis.

Keywords: Fiber-optic chemical sensor; Hydrogen ion concentration; Kidney; Shock wave lithotripsy; Tubule.

Figure 1

Fiber-optic microsensor.

Figure 2

Measurements of buffer pH solutions using the fiber-optic phase detection system. Each open circle at a particular buffer pH represents a single measurement from one microsensor (see Table 1). Identity line is shown.

Figure 3

Sequence of events involved in measuring tubule urine pH (see text in Results section).

Figure 4

Shown are examples of phase angle and derived pH values from microsensors in Bellini ducts. Note that fluctuations in phase angle values prior to a stable reading resulted in only small changes in pH values.

Figure 5

Shown are microsensor phase angle values of buffer pH solutions before and after ETO sterilization (panel A). Microsensor derived pH values of buffer pH solutions after ETO sterilization (panel B). Mean ± SD values and identity line are shown.