**2. Methods of determining SUI in animal models**

SUI is a clinical diagnosis mainly by history and physical examination. ICS has defined uro‐ dynamic stress incontinence as involuntary leakage of urine during filling cystometry, asso‐ ciated with increased intra‐abdominal pressure, in the absence of a detrusor contraction [10]. The role of urodynamic studies (UDS) is important in identifying types of SUI. Types of SUI can be determined with valsalva leak point pressure (VLPP) and urethral pressure profilometry (UPP). According to Blaivis, SUI types 1 and 2 are related to urethral hyper mobility with VLPP > 90 cm of water for type 1 and between 60 and 90 cm of water for type 2, respectively. Blaivis type 3 SUI is with VLPP < 60 cm water, also known as intrinsic sphincter deficiency (ISD). In addition, a urethral pressure profile (UPP which is urethral pressure– detrusor pressure) < 20 cm water is also seen in the cases of ISD [12]. Animal models that simulate SUI provide an assessment of the mechanism of risk factors, including childbirth injuries, preclinical testing of new treatments and therapies for SUI. Since animals cannot express intent, the use of these animal models has been focused on measuring decreased urethral resistance [13].

#### **2.1. Sneeze testing**

on quality of life. Over \$12 billion are spent annually for management of SUI in women [4]. The average annual total cost for fecal incontinence is estimated at \$4110 per person [5]. Stress urinary incontinence (SUI) may be defined as involuntary loss of urine on effort or physical exertion (e.g., sporting activities), or on sneezing or coughing. Urgency urinary incontinence (UUI) relates to involuntary loss of urine associated with a desire to void, while anorectal

The ultimate success of long‐term management for double incontinence (DI) is based on an understanding of disease pathophysiology. Little is known about the degree to which UI and FI share risk factors. Animal models have been used to understand pathogenesis of these conditions in humans and for developing novel treatment alternatives. Even though many animal models have been developed to understand pathogenesis, yet many of etiological fac‐ tors are not explained. Many animal models are used as simulators for teaching surgical skills but long‐term studies have not shown the desired improvement in surgical outcome [6]. The surgical procedures in humans were developed through the use and application of animal

Urinary incontinence is relatively easy to understand when compared to fecal incontinence as anal sphincter defects and FI are complicated surgical problems. Research on use of stem cell for treatment of FI was conducted on rabbits by an iatrogenic sphincter defect, created by cutting of anal sphincter. Human umbilical cord matrix (hUCM) and stem cells from rabbit femur and tibia were harvested and transplanted into injured sphincters which later showed an improvement in their function. Bone marrow‐derived stem cells and mesenchymal cells of animals have shown to enhance contractile function of anal sphincter without surgical repair [8]. The limitation of using animals is in their difference with anatomy and size of vis‐ cera, which affects the functional outcome. Human cadavers have been used for a long time for teaching anatomy, but due to ethical issues animals were introduced in medical teach‐ ing. Animal models were found quite effective, but because of major difference in functional anatomy, mannequins were introduced for medical teaching and learning. There are many centers for simulation‐based innovation for medical education (SIME), which probably would

Most of the studies on new medical and surgical treatment involve the use of animal mod‐ els for preclinical trials. In this chapter, we discussed use of animal models for relevant research, procedures on pathogenesis and surgical training techniques for DI. We have used standardized terminology for definitions as described by the International Continence Society (ICS) and International Urogynecological Association (IUGA) joint report on ter‐

SUI is a clinical diagnosis mainly by history and physical examination. ICS has defined uro‐ dynamic stress incontinence as involuntary leakage of urine during filling cystometry, asso‐ ciated with increased intra‐abdominal pressure, in the absence of a detrusor contraction

**2. Methods of determining SUI in animal models**

incontinence (AI) is a complaint of involuntary loss of feces or flatus.

126 Experimental Animal Models of Human Diseases - An Effective Therapeutic Strategy

model as slings and trocar‐driven implants [7] for anti‐incontinence procedures.

give similar results [9].

minology [10, 11].

SUI is clinically assessed on humans as observation of involuntary leakage from the urethra with effort or physical exertion, or on sneezing or coughing [10]. Based on the urinary leak with a rise in abdominal pressure, sneeze test can be performed in female rat under anesthe‐ sia. A whisker cut from anesthetized rat was used to tickle its nose. Even under anesthesia the rat responded with a small sneeze, which transiently increased abdominal pressure. Karl et al. performed cystometry with methylene blue dye in bladder to detect urinary leak. The animal was diagnosed as incontinent if they leaked during the sneeze test and continent if no leak on sneezing was observed [13, 14].

#### **2.2. LPP testing**

The human bladder functions by storage and voiding of urine. Voiding is accompanied by an increase in detrusor pressure and a decrease in urethral pressure. In leak point pressure (LPP) testing [15], rats were anesthetized and a transperitoneal catheter implanted in the blad‐ der dome was tunneled subcutaneously from the back of the bladder neck to an exit via the skin. The catheter was capped and the skin incision closed in two layers. The bladder catheter was connected to both a syringe pump and a pressure transducer. The bladder when filled with room‐temperature saline through the catheter, the bladder pressure was recorded via a microtip transducer urethral catheter. Pressure and force transducer signals were amplified and recorded on a chart recorder. All bladder pressures were referenced to air pressure at the level of the bladder very similar to LPP assessment in humans with use of external trans‐ ducers. The three commonly used mechanisms are manual pressure/Crede's LPP, electrical stimulation LPP and table tilt LPP [16–18].

#### *2.2.1. Manual LPP testing*

To perform manual LPP testing in rats, they put supine on table and a passive/manual abdominal pressure is applied and increased gradually, thus increasing the vesical pressure until leakage is observed at the urethral meatus. The peak bladder pressure was taken as the LPP. After leak, the external pressure is rapidly removed and bladder pressure quickly returns to baseline [17].

#### *2.2.2. Vertical tilt table LPP*

Rat is mounted on a vertical tilt table to keep the bladder erect during UDS, similar to human studies. A saline reservoir is connected to a suprapubic catheter to passively increase bladder pressure by elevating it and maintaining it at a range of pressures (20, 40 and 60 cm H2 O) [19]. In this method, the spinal cord is often transected usually at T8–T9. This transaction elimi‐ nates the supraspinal reflex voiding but preserves the urethral reflexes induced by bladder distention, which are predominantly organized in the lumbosacral spinal cord [20]. Studies have shown comparable results of LPP with sneeze test, manual pressure test and vertical tilt table test [21].

Several studies [25, 26] have demonstrated vaginal injury by VD which is induced by using a Foley catheter with cut tip and inflated with different fluid volumes from 2 to 4 ml. This creates pressure in vagina and iatrogenic injury to the urethra, bladder, vagina and levator muscles. Functionally, VD results in decreased urethral resistance, as evidenced by lowered leak point pressures on urodynamic testing done in most of the VD studies [27]. In a study by Lin et al., VD was created in mice by 0.1–0.3 ml balloon in comparison with sham distension. LPP was signifi‐ cantly lower in groups after VD with 0.2–0.3 ml as compared to sham [28]. Research has shown that this procedure has helped in understanding molecular factors like chemokines, neuro‐ regenerative agents and pharmacological agents that contribute to functional recovery includ‐ ing stem cell mobilization following injury [27, 29]. It has also helped in evaluation of the impact of contributing/decompensating factors in the pathophysiology and recovery of continence.

Animal Models of Double Incontinence: "Fecal and Urinary"

http://dx.doi.org/10.5772/intechopen.69962

129

Urinary urge incontinence is observed among patient of overactive bladder (OAB) which is called wet OAB. There are many pathophysiological bases for its explanation including neuro‐ genic and myogenic theories. It has been established through animal studies that urge incon‐ tinence is predominantly due to a defect in bladder muscle [30]. In a study on pigs, unstable bladder contractions were produced against induced outflow obstruction, bladder distention and bladder transaction. In affected pigs, stimulation of the spinal roots could no longer alter detrusor contraction. Similarly, sectioning of the spinal roots in these animals did not elimi‐ nate the unstable pressure rise explaining myogenic basis of OAB [31]. These manipulations do not eliminate the possibility of increased neuronal firing at the ganglionic level. However, recently, it has been shown that both hexamethonium (which blocks ganglionic transmission) and tetrodotoxin (TTX, which abolishes all neuronal activity) inhibit micturition but do not abolish unstable contractions in the pigs or rats [32, 33], hence supporting myogenic theory. The majority of the structural changes seen were obtained with light microscopic techniques,

and local detrusor changes were found similar to those among human with OAB.

The innervation of the external urethral sphincter (EUS) from the pudendal nerve is similar between rats and humans [34]. In female rats, the motor pudendal nerve bifurcates within Alcock's canal into separate fascicles that innervate the external anal sphincter (EAS) and EUS. The pudendal nerve controls EUS activity, including tonic activity during continence, and acti‐ vates to strengthen the guarding response to prevent urinary leakage [35]. It can be trapped and injured during vaginal childbirth because it passes through Alcock's canal in the ischiorec‐ tal fossa, especially between the sacrospinous and the sacrotuberous ligaments [36]. Pudendal nerve crush (PNC) injury was induced in rats simulating childbirth injury, leading to deficiency of EUS and causing SUI [37]. Another rat study demonstrated the Pudendal nerve injury effects on external anal sphincter similar to injury during child birth in human affecting EAS and causing FI. In Healy et al.'s study [38], one group of rats used for the experiment had induced bilateral inferior rectal nerve crush (Group A) injury which then acted as a positive control and was observed for EAS effects. In another group (Group B), an intrapelvic retro‐uterine balloon

**3.2. Causes of UUI**

**3.3. Causes of DI**

#### *2.2.3. Electrical stimulation LPP testing*

Electrical stimulation of abdominal muscles for 1 s induces sudden increase in both the intra‐ abdominal and the intravesical pressure. The lowest intravesical pressure that induced fluid leakage from the urethral orifice (leak point pressure) and the maximal intravesical pressure without urine leakage were recorded and were used to evaluate urethral resistance. However, like tilt table testing, electrical stimulation LPP testing also requires spinal cord transection, suppressing supraspinal continence control [22].

#### **2.3. Urethral closure pressure testing**

Effects of stem cell transplantation in rats were evaluated through urodynamic testing, and morphologic changes of the urethra and surrounding tissues were studied [23] both before and after transplantation. The bladder catheter was used as an intraurethral pressure mea‐ surement catheter, connecting it to a three‐limb tube through a conversion joint. One end of that three‐limb tube was connected to the intraurethral pressure sensor, and the other end was connected to the micropump, maintaining the original intraurethral pressure measure‐ ment catheter. Pressure was set at 0, and infusion by micropump at rate of 0.25 ml/min was started. Urethral pressure profilometry (UPP) rod was used to pull the intraurethral pres‐ sure measurement catheter at 0.1 mm/s traction speed. Meanwhile, intraurethral pressure and intrabladder pressure were recorded. Maximum urethral closure pressure (MUCP) was intraurethral pressure minus intrabladder pressure. Functional urethra length (FUL) was also calculated. Transplantation of adipose‐derived stem cells significantly strengthened local ure‐ thral muscle layers and significantly improved the morphology and function of sphincters.
