The uterus, cervix, and adnexa share visceral innervation with the lower ileum, sigmoid colon, and rectum. These pain signals travel through sympathetic nerves to spinal cord segments T10 to L1. It is often difficult, therefore, to determine whether lower abdominal pain is of gynecologic or enterocoelic origin. Skillful medical history and examination are necessary to distinguish gynecologic from gastrointestinal causes of pain. Inﬂammatory bowel disease, such as Crohn’s disease or ulcerative colitis, infectious enterocolitis, intestinal neoplasms, appendicitis, and hernia must be ruled out with appropriate history and physical examination, complete blood cell count, and stool cultures and visualization of colonic mucosa when appropriate.
IBS is one of the more common causes of lower abdominal pain and may account for up to 60% of referrals to the gynecologist for chronic pelvic pain. An estimated 35% of patients with chronic pelvic pain have a concurrent diagnosis of IBS (102,103). Women who had a hysterectomy for chronic pelvic pain are twice as likely to have IBS. The pathophysiology of IBS appears to be inﬂuenced by central nervous system sensitization and decreased descending inhibition, which ultimately leads to the visceral hypersensitivity. Visceral hypersensitivity and abnormal reﬂex responses, demonstrated in both animal and human studies, results in an increased intensity of pain, lowered threshold for sensation, and an enlarged viscera-somatic region of pain referral, all of which lead to the IBS symptoms (104,105).
The predominant symptom of IBS is abdominal pain. Other symptoms include abdominal distention, excessive ﬂatulence, alternating diarrhea and constipation, increased pain before a bowel movement, decreased pain after a bowel movement, and pain exacerbated by events that increase gastrointestinal motility, such as eating, stress, anxiety, depression, and menses. The pain is usually intermittent, occasionally constant, cramp-like, and more likely to occur in the left lower quadrant. The patient with IBS can be placed into one of three categories: constipation-predominant, diarrhea-predominant, and pain-predominant (alternating bowel habits) depending on their main symptoms. The new Rome III criteria for diagnosis
Table 16.5 Rome III Criteria for Irritable Bowel Syndrome
At least 3 days per month of recurrent abdominal pain or discomfort for the previous 3 months, has associated with two of three features: 1.
Relieved with defecation; and/or 2.
Onset associated with a change in frequency of stool; and/or 3.
Onset associated with a change in form (appearance) of stool.
(Table 16.5) includes at least 3 days of recurrent abdominal pain or discomfort per month over the past 3 months with at least two of the following features: relief with defecation, onset associated with change in stool frequency, or onset associated with change in form and appearance of stool (106).
On physical examination, the findings of a palpable tender sigmoid colon or discomfort during insertion of the finger into the rectum and hard feces in the rectum are suggestive of IBS.
The diagnosis of IBS is usually based on history and physical examination, and although suggestive, especially in young women, the findings are not specific. A CBC, thyroid function study, stool sample to test for white cells and occult blood, and sigmoidoscopy or colonoscopy or barium enema are usually required, particularly in older individuals and in young individuals who have not responded to initial treatment. The results of these studies are all normal in patients with IBS.