**2. Visceral pain physiology**

The physiological basis for pain testing is viscero-somatic pain referral. One of the first such observations was made by Sir James Mackenzie (1853–1925). Although known primarily for his work on cardiac physiology, arrhythmias, and heart disease, he wrote a book in 1913 that provides insight into how we might understand the clinical signs of pelvic disease [6]. Mackenzie provided a diagram of a man with biliary colic who had pain radiating to his right upper quadrant (**Figure 1**). This painful area was also found to have an area of allodynia in the same area. Allodynia is defined as pain from a non-painful source. The allodynia can be static or dynamic depending on the mode of testing. Static allodynia is direct pressure on the skin, while dynamic allodynia uses movement across the affected area. Notably, Mackenzie found a small area within the region of allodynia that was particularly tender and corresponded to the anterior cutaneous nerve that passed through the abdominal wall fascia. Mackenzie correctly noted that not only the colicky pain was referred to the right upper quadrant but also there was also a tiny muscular component of this referral, centered on the tender ninth thoracic nerve as it perforates the abdominal wall fascia.

This simple diagram is the basis for the clinical testing of women's pelvic pain at the bedside. Most of the causes of pain in the pelvis associated with endometriosis are due to inflammatory processes. These are considered nociceptive influences on the afferent nervous system that pass to the spinal cord primarily in the T12 and L1 segments. The viscero-somatic referral then initiates efferent activity through the corresponding anterior cutaneous nerves to the lower abdomen. The result of the efferent activity is the pattern of allodynia and tender areas in a similar fashion to Mackenzie (**Figure 1**). There are many variations of the presentation, unilateral, bilateral, with both equal and unequal sizes of the allodynia [6].

Another contributor was Sir Henry Head (1861–1940) who, mapped out the referral patterns of the body of many illnesses that initially became the Head zones but later evolved to be the dermatomes. The accompanying figure demonstrates the ovarian zones (**Figure 2**) [7].

#### **Figure 1.**

*Location of right upper quadrant allodynia associated with tenderness in the region of ninth anterior cutaneous nerve due to biliary colic.*

**63**

**Figure 3.**

*Pain Testing in Endometriosis for the Clinician DOI: http://dx.doi.org/10.5772/intechopen.92756*

More recent studies of the visceral-somatic referral and guidelines for the

To detect allodynia, a cotton-tipped applicator is slowly drawn down from the midclavicular line toward the pubic region along the imagined border of the rectus abdominus muscle. It is necessary to start the test outside the area of allodynia. Starting within will not detect the necessary changes. As the applicator is positioned, the woman is asked to note if there is any sudden change in sensation or the onset of a sharp pain. When this is announced, the level is marked off with a body marker. An example of two small areas of allodynia containing trigger points associated with the T12 anterior cutaneous nerves is

An extreme example of severe chronic pelvic pain demonstrates how large the area of allodynia can become—this degree is unusual (**Figure 4**). The delineation of allodynia that is marked off with a pen can stimulate spinal activity such that there is an almost immediate shift in the borders of allodynia (**Figure 4**). These shifts in the levels of sensation correspond to "jumps" taking place in the spinal cord,

*Small areas of allodynia containing painful trigger points of T12 anterior cutaneous nerves.*

management of associated persistent pain have been reported [8–12]**.**

**3. Detection of allodynia and expansion**

shown in **Figure 3**.

**Figure 2.**

*Demonstration of the Head zones.*

segment by segment.

*Pain Testing in Endometriosis for the Clinician DOI: http://dx.doi.org/10.5772/intechopen.92756*

*Endometriosis*

**2. Visceral pain physiology**

it perforates the abdominal wall fascia.

ovarian zones (**Figure 2**) [7].

The physiological basis for pain testing is viscero-somatic pain referral. One of the first such observations was made by Sir James Mackenzie (1853–1925). Although known primarily for his work on cardiac physiology, arrhythmias, and heart disease, he wrote a book in 1913 that provides insight into how we might understand the clinical signs of pelvic disease [6]. Mackenzie provided a diagram of a man with biliary colic who had pain radiating to his right upper quadrant (**Figure 1**). This painful area was also found to have an area of allodynia in the same area. Allodynia is defined as pain from a non-painful source. The allodynia can be static or dynamic depending on the mode of testing. Static allodynia is direct pressure on the skin, while dynamic allodynia uses movement across the affected area. Notably, Mackenzie found a small area within the region of allodynia that was particularly tender and corresponded to the anterior cutaneous nerve that passed through the abdominal wall fascia. Mackenzie correctly noted that not only the colicky pain was referred to the right upper quadrant but also there was also a tiny muscular component of this referral, centered on the tender ninth thoracic nerve as

This simple diagram is the basis for the clinical testing of women's pelvic pain at the bedside. Most of the causes of pain in the pelvis associated with endometriosis are due to inflammatory processes. These are considered nociceptive influences on the afferent nervous system that pass to the spinal cord primarily in the T12 and L1 segments. The viscero-somatic referral then initiates efferent activity through the corresponding anterior cutaneous nerves to the lower abdomen. The result of the efferent activity is the pattern of allodynia and tender areas in a similar fashion to Mackenzie (**Figure 1**). There are many variations of the presentation, unilateral,

Another contributor was Sir Henry Head (1861–1940) who, mapped out the referral patterns of the body of many illnesses that initially became the Head zones but later evolved to be the dermatomes. The accompanying figure demonstrates the

*Location of right upper quadrant allodynia associated with tenderness in the region of ninth anterior cutaneous* 

bilateral, with both equal and unequal sizes of the allodynia [6].

**62**

**Figure 1.**

*nerve due to biliary colic.*

**Figure 2.** *Demonstration of the Head zones.*

More recent studies of the visceral-somatic referral and guidelines for the management of associated persistent pain have been reported [8–12]**.**
