Comparative Anatomy of the Male Guinea‐Pig and Human Lower Urinary Tract: Histomorphology and Three‐Dimensional Reconstruction

Abstract

The guinea-pig is often used for experimental studies in urology. However, the anatomy of the lower urinary tract of the guinea-pig is poorly described in the literature. The structure and function of the lower urinary tract, i.e. continence, micturition and sexual function, are closely related to the gross anatomy of the pelvis and the fine structure of the musculature. We investigated the anatomy and histomorphology of the lower urinary tract by serial sections in male guinea-pigs and compared it to that in humans. Immunohistochemical stainings for alpha-smooth muscle cell actin were used to differentiate between smooth and striated muscles. By using whole pelvic preparations, including all internal organs preserved in their in situ location for three-dimensional reconstruction, we developed three-dimensional models, which elucidate the spatial relationship of all muscular structures and can help to deduce functional aspects of lower urinary tract function. In the guinea-pig, most of the muscles found in humans can be demonstrated in comparable location and extension. However, the structure of the prostate and the existence of the so-called coagulation glands define a significant difference in the morphology of the prostatic urethra.

Animal models in urological disease and sexual dysfunction

“…In this regard, it is paramount to utilise animal models that most closely resemble the human LUT, both in terms of anatomical and physiological function. A wide variety of animal species have previously been utilised to investigate LUT function, including non‐human primates, dogs, pigs, cats, rabbits, rats, guinea‐pigs, mice and hamsters (Harada et al ., 1989; Kontani et al ., 1992; Yoshimura et al ., 1993; Danuser & Thor, 1996; Ghoniem et al ., 1996; Watanabe et al ., 1997; Giuliani et al ., 1998; Yoshimura et al ., 1998; Zvara et al ., 1998; Doi et al ., 1999; Nickel & Venker‐van Haagen, 1999; Palea & Pietra, 1999; Pandita et al ., 2000; Bae et al ., 2001; Calvert et al ., 2001; Lecci et al ., 2001), the majority of these species sharing a number of common anatomical (DeLancey, 1990; Dwyer & Glenning, 1990; Birder & de Groat, 1993; Fletcher, 1996; Neuhaus et al ., 1999; 2001; Dass et al ., 2001; Ganzer et al ., 2002; 2004; Silva & Karram, 2004), pharmacological (de Groat & Yoshimura, 2001) and neurophysiological (de Groat, 1998; Blok & Holstege, 1999; Blok, 2002) features in comparison to humans. However a number of these species are also known to exhibit specific differences in normal urinary tract structure and function in comparison to humans, which must be considered before extrapolating pharmacological or physiological findings to potential therapeutic treatments in man.…”

Experimental investigation of the biomechanics of urethral tissues and structures

“…Small rodents are not taken into consideration owing to the different size and structure of the lower urinary tract (Nozaki, ; Neuhaus et al . ; Maia et al . ).…”

Foreign body cystitis in a male guinea pig due to a sedge (Carex species) leaf

“…This reflected that the described firm beads were most probably blocking the cranial part of the spongy portion of the urethra where the inner diameter of the urethra reduces from 4 to 3 mm due to the presence of the spongy tissue surrounding it 31. Only the pelvic part of the urethra is surrounded by defined smooth and striated muscular structures 32. The use of either alpha‐adrenergic drugs such as prazosin or spasmolytic agents such as midazolam might help in deblocking the pelvic part of the urethra and enable flushing of the granules back into the bladder, making them accessible to surgical removal.…”