A Novel Concept on the Patho-Physiology of Defecation and Fecal Incontinence (FI) in Women – Moreover, Its Reconstructive Surgery

We put forward a new concept explaining the physiology of defecation and the anatomy of the internal anal sphincter (IAS). We explain the important role that the IAS plays in the control of defecation and fecal continence. Our aim is to explain the physiology of defection, factors that control fecal continence and causes of fecal incontinence in women together with the importance and the structure of the internal anal sphincter (IAS) and how it maintains fecal continence. The harmony between the central nervous system (CNS), the autonomic nervous system, the integrity of the anal sphincters and the muscles of the body are essential for keeping fecal continence. Traumatic injury can occur during childbirth affecting the anal sphincters and causing fecal incontinence (FI). Difficult vaginal deliveries can lead to more than one lesion at the same time. Simultaneous stress urinary incontinence (SUI), vaginal prolapse and fecal incontinence (FI) arise as a sequel to the cumulative trauma of recurrent frequent vaginal deliveries.


Introduction
We put forward a new concept explaining the physiology of defecation and the anatomy of the internal anal sphincter (IAS). We explain the important role that the IAS plays in the control of defecation and fecal continence. Our aim is to explain the physiology of defection, factors that control fecal continence and causes of fecal incontinence in women together with the importance and the structure of the internal anal sphincter (IAS) and how it maintains fecal continence. The harmony between the central nervous system (CNS), the autonomic nervous system, the integrity of the anal sphincters and the muscles of the body are essential for keeping fecal continence. Traumatic injury can occur during childbirth affecting the anal sphincters and causing fecal incontinence (FI). Difficult vaginal deliveries can lead to more than one lesion at the same time. Simultaneous stress urinary incontinence (SUI), vaginal prolapse and fecal incontinence (FI) arise as a sequel to the cumulative trauma of recurrent frequent vaginal deliveries.
We will describe a novel technique for the surgical repair of vaginal wall prolapse, SUI and fecal incontinence.
Fecal Continence depends on a closed and empty anal canal, which in turn depends on four main factors: 1. The integrity of the two anal sphincters: (the internal anal sphincter (IAS) and the external anal sphincter (EAS); both anal sphincters must be intact with healthy and strong walls. Intact healthy vascular and nerve supply are important factors for anal sphincter function.
2. An acquired high alpha-sympathetic tone at the IAS that keeps the anal canal closed and empty at all times until there is a desire and/ or a need to pass flatus &/ or stool and under suitable social circumstances. The high alpha-sympathetic tone is gained by learning and training in early childhood.

3.
Healthy and strong pelvic floor muscles, including the levator ani, that maintain the angle between the rectum and the anal canal.

4.
Synchronization and synergistic actions between the central nervous system (CNS), the autonomic nervous system, peripheral somatic nerves, the muscles and the anal sphincters.
The closed and empty anal canal has a high anal pressure that is much higher than rectal pressure; rectal pressure reflects the abdominal pressure.

Figure 1. Physiology of defecation
Diagram that explains the steps that take place sequentially during defecation.

Gaining control of defecation
Gaining control is achieved by maintaining high alpha-sympathetic tone in the IAS keeping it contracted and the anal canal closed and empty at all times and until an appropriate place and time are available. On rectal distension, stretch receptors are stimulated. The sensation of rectal distension travels along the pelvic parasympathetic nerves to S 2, 3 and 4 to the sacral spinal cord centers. The ano-rectal junction contains specialized sensory end organs for tension, temperature, texture, touch and friction. Specialized afferent nerves sub serve these organized nerve endings. Controlled by the central nervous system (CNS), an intact sampling reflex allows the individual to choose whether to: a. Retain the rectal contents or, b. Discharge the contents whether flatus and/ or stool.
Dependent on the available social circumstances, and once maturational control of continence has been achieved, if the woman chooses to retain rectal contents until a later time when social circumstances are more favourable, then she will: Fecal incontinence can have other causes including one or a combination of the following:

1.
Congenital causes: In cases of imperforate anus, partial or complete lack of the sphincter mechanism (rare).

2.
Patulous anus is associated with mental retardation.

3.
Malabsorption conditions e.g. cystic fibrosis; drugs; and indigestible dietary fats that interfere with the intestinal absorption will lead to FI.

6.
Perineal resection of the rectum for carcinoma.
A major cause of fecal incontinence in young healthy women is anal sphincter damage during vaginal delivery, which occurs in as many as 18% in the USA. Studies from other countries indicate 5-20% of women report incontinence of stool 3-6 months after sphincter tear (EAS), and 29-53% of women report incontinence of flatus, despite having the tear repaired at delivery (5).
Surgical repair of the torn EAS is by suturing end-to-end the torn edges of the EAS; or suturing after overlapping the torn edges. All published reports of the results of overlapping technique have shown significant improvements in symptoms of FI, with 60-80% achieving continence (6). It is also clear, however, that fecal control deteriorates over time with only 50% of the initial successful outcomes having improved continence at five years (7). Poor understanding of perineal anatomy and inadequate training in repair techniques are possible reasons for the high incidence of persistent symptoms (6,7). In addition, this can explain why repair of the EAS in cases of complete perineal tear whether by end-to-end or overlapping techniques does not lead to complete continence (7).
The problem is that the role of the Internal Anal Sphincter (IAS) in defecation and FI is not quite clear.
We will describe the IAS in a novel way and its important role in maintaining fecal continence and defecation (1, 2, 33), (figure 2).
The IAS is a collagen-muscle tissue cylinder that surrounds the anal canal, and is in turn surrounded externally in its lower part by the EAS. Its nerve supply is from the alphasympathetic nerves coming through the thoracolumbar alpha-sympathetic nerves, from the hypogastric plexus (T10-L2). The collagen constitutes the firm frame (chassis) of the IAS, while the muscle is the mover of the sphincter in response to nerve stimulus. Its functions are: The IAS is in close relation to the posterior vaginal wall, which stretches very much during labor. Prolonged labor, difficult, multiple frequent labors cause overstretching of the posterior vaginal wall, leading to flabbiness of the vagina with subsequent falling down of the redundant vaginal wall, posterior vaginal wall prolapse (rectocele). The redundancy of the vaginal wall is the result of rupture of its collagenous sheet (the vaginal firm frame). The rupture will affect and damage the intimately related IAS with subsequent FI. The rupture in the IAS affects the collagen layer (the collagen frame). Damage of the IAS causes dilation of the anal canal. Open and dilated anal canal with a lowered pressure allows the rectal contents to enter the open anal canal with subsequent fecal incontinence. Therefore, we can more correctly say that the first cause of FI is anal sphincter damage, with traumatic injury to one and/or both anal sphincters, IAS, EAS (figures: 3 to 15).
A Novel Concept on the Patho-Physiology of Defecation and Fecal Incontinence (FI) in women; Moreover, its Reconstructive Surgery  Three dimension ultrasound (3DUS) images of the rectum and anal canal with torn IAS in patients with fecal incontinence (FI).
FI is the main complaint in posterior vaginal wall prolapse (rectocele). Concomitant troubles, which commonly occur, are vaginal prolapse (anterior and posterior), stress urinary incontinence (SUI) and FI (1) (Figures: 13, 14 &15). The internal urethral sphincter (IUS) is in close contact to the anterior vaginal wall and will be involved in the childbirth trauma with subsequent SUI and anterior vaginal wall prolapse.
Childbirth trauma is the major cause of damage, but aging, hormone deficiency (menopause) and degeneration from chronic and/or repeated infections causing collagen degeneration and atrophy can add to the weakness of the internal urethral sphincter (IUS), IAS and the vagina.

A B
The patient previously had a classical repair so the vagina is not prolapsed. However, she suffers from combined SUI&FI.

Fecal Incontinence 12
A Novel Concept on the Patho-Physiology of Defecation and Fecal Incontinence (FI) in women; Moreover, its Reconstructive Surgery Figure 12: Images with 3DUS of the rectum and anal canal in patients with FI. Images in C & D are of a complete perineal tear (fourth degree). The external anal sphincter is torn and appears as a horseshoe; in addition, the internal anal sphincter is torn as well. Images in A and B are of the internal anal sphincter, which is torn leading to an open dilated anal canal. The IAS in this image also appears like a horseshoe.
A B D C Figure 12. Images with 3DUS of the rectum and anal canal in patients with FI. Images in C & D are of a complete perineal tear (fourth degree). The external anal sphincter is torn and appears as a horseshoe; in addition, the internal anal sphincter is torn as well. Images in A and B are of the internal anal sphincter, which is torn leading to an open dilated anal canal. The IAS in this image also appears like a horseshoe.

Diagnosis
In addition to the clinical history and examination, imaging with three-dimension ultrasound (3DUS) and magnetic resonance (MRI) is an essential tool in the management of cases of FI. Typically, it shows an open anal canal with torn IAS. It may also reveal an open urethra and torn IUS with concomitant SUI and vaginal prolapse (figures: 3, 4, 5, 6, 7, 8, 10, 11, 12, 13 & 14). Histopathological examination of a torn piece of the IAS confirm that the rupture mainly affects the collagen frame of the IAS (figure 9).

Reconstructive surgery (figures: 15, 16, 17, 18 & 19)
In conclusion, a major cause of FI in young patients is torn IAS. We have developed an operative procedure to expose and mend the torn edges of the IAS. Since there is usually concomitant vaginal prolapse and SUI, we try to correct these concurrently as part of this new operation.
In the Anterior section, we correct the SUI and the anterior vaginal wall descent through the following steps: (Figures: 15 & 16).
A Novel Concept on the Patho-Physiology of Defecation and Fecal Incontinence (FI) in women; Moreover, its Reconstructive Surgery  We grasp the cervix with two pairs of cervical volsela. We inject about 10-20 ml. normal saline with adrenaline (2 per 200 thousand concentration}, beneath the vaginal wall to act as a hydro dissection and vasoconstrictor. This separates the anterior vaginal wall from the posterior wall of the IUS. We make a 2-4 cm transverse incision about three cm above the external cervical os. With a pair of dissecting scissors, we separate the anterior vaginal wall from the IUS. We cut the anterior vaginal wall longitudinally from the transverse cut all the way, "down", to the submeatal sulcus, which correspond to the perineal membrane. We grasp each vaginal flap with three pairs of Kocher's forceps. The defect in the IUS will be apparent and on each side, we can clearly see two clear edges. One edge is of the anterior vaginal wall and the other is the torn posterior wall of the IUS.

1.
Expose the IUS (we dissect the IUS clear from the anterior vaginal wall).  A Novel Concept on the Patho-Physiology of Defecation and Fecal Incontinence (FI) in women; Moreover, its Reconstructive Surgery Figure 18: Surgical steps of posterior repair. We dissect the IAS from the posterior vaginal wall (A). We mend the sphincter (B&C), in addition, we approximate the two levator ani muscles by two stitches, but we do not tie them till we finish overlapping the posterior vaginal wall (D).
A B C D Figure 18. Surgical steps of posterior repair. We dissect the IAS from the posterior vaginal wall (A). We mend the sphincter (B&C), in addition, we approximate the two levator ani muscles by two stitches, but we do not tie them till we finish overlapping the posterior vaginal wall (D). Figure 19. Images that show the steps taken to expose the torn IAS and mend it (A&B). We then overlapped the redundant posterior vaginal wall as is seen in (C). Next, we approximated the two levator ani muscles; and finally repaired the perineum as is seen in (D).