Diffusion properties of transurethral intraprostatic injection

Abstract

OBJECTIVES To evaluate the location and extent of diffusion that occurs when liquid is injected transurethrally into the prostate gland, by correlating real‐time fluoroscopy and gross pathology, and to quantify the variables that influence intraprostatic diffusion during chemoablation of the prostate. MATERIALS AND METHODS A solution of diatrizoate meglumine (HypaqueTM, Nycomed, Princeton, NJ) gentamicin and methylene‐blue dye (HGM) was injected transurethrally into the prostate in six dogs, using a passive‐deflection needle injection system. The intraprostatic diffusion characteristics were evaluated during each injection using real‐time C‐arm fluoroscopy, and following each injection by gross examination of methylene blue staining within the prostatic tissues. HGM back‐flow into the urethra at the time of injection was assessed by measuring gentamicin levels in the collected bladder irrigant after each injection, using a standard dilution formula. RESULTS There was variability in the intraprostatic diffusion both fluoroscopically and grossly. The needle occasionally assumed a straighter trajectory than its intended curve. Intraprostatic diffusion was detected in 12 of 36 injections (33%). Using standard manipulations of various devices increased the intraprostatic diffusion in these injections to almost 80%. There was less intraprostatic diffusion when the injection resistance was either extremely high or absent. There was no extraprostatic extravasation of HGM beyond the prostatic capsule. CONCLUSION Current methods of transurethral intraprostatic injection are variable for both the diffusion of HGM solution and in needle deployment. The gross diffusion patterns with the HGM solution were consistent with the diffusion patterns documented in our previous research using absolute ethanol. These and other factors may partly explain the variability of the lesions produced with ethanol injection. Therefore, more research is needed to further elucidate the diffusion characteristics of solutions injected intraprostatically using the transurethral approach.

Intraprostatic ethanol diffusion: comparison of two injection methods using ex vivo human prostates

“…There is a correlation between the volume injected and the size of the lesion when using a standard 21-G needle. 9 Further studies are needed to elucidate the correlation between the injected dose and the volume of tissue in which the drug is distributed using CED.…”

“…Results from this study showed the variability is likely owing to various degrees of ethanol backflow along the needle tract. 8,9 We hypothesized that the variability is secondary to the tissue type the needle tip is imbedded into, causing differences in resistance and diffusion during injection. As a possible solution, we investigated convection enhanced delivery (CED) using a microporous hollow fiber catheter (MiHFC).…”

Treatment of lower urinary tract symptoms: Agents for intraprostatic injection

“…A disadvantage with liquid alcohol is that its distribution is difficult to control, making accurate placement problematic [24]. Larson et al [25] tried to overcome this problem by using anhydrous ethanol in gel form.…”

Comparison of Intraprostatic Ethanol Diffusion Using a Microporous Hollow Fiber Catheter Versus a Standard Needle

“…We previously reported that the prostate capsule acts as a barrier that prevents the injected substance from diffusing beyond the organ, making it a suitable target for drug delivery using direct intraprostatic injection. 2,3 …”

“…Variable clinical outcomes were also reported, 5–8 likely due to varying resistance of the tissue type in which the needle tip was embedded (stroma, muscle or glandular tissue) as well as backflow of the substance along the needle tract. 3 …”