Chronic Pelvic Pain
Khara M. Simpson
Wen Shen
Chronic pelvic pain (CPP) is a common and often difficult problem, with direct medical costs estimated at $1 to $2 billion per year in the United States. CPP affects quality of life, increases work absenteeism, decreases overall productivity, and limits normal physical, social, emotional, and sexual function. The differential diagnosis is extensive and the cause is often multisystem and multifactorial. CPP is the diagnosis for 10% to 20% of gynecology office referrals. Up to 90% of patients with CPP will undergo one or more unsuccessful, and often unnecessary, gynecologic procedures. At least 40% of gynecologic laparoscopies are performed for CPP, but only 30% to 60% of those surgeries reveal a cause. Ten percent to 20% of hysterectomies are performed with the primary indication of CPP, but relief is not universal.
TYPES OF PELVIC PAIN
There are no standard diagnostic criteria, but a reasonable definition of CPP is cyclic or noncyclic pain in the lower abdomen, pelvis, lower back, or buttocks of at least 6 months duration that causes functional disability and motivates the patient to seek medical help. Because of varied definitions, the epidemiology and natural history of CPP are not well described. Acute pelvic pain can be defined with the same criteria but lasts <30 days.
CPP is most common in younger adult women. Four percent to 15% of reproductive age women are affected, similar to other common disorders such as asthma, migraine headache, and lower back pain.
Dysmenorrhea (pain associated with menstrual cycles) occurs in up to 90% of women. Risk factors include age <30 years; body mass index <20; tobacco use; early menarche; menometrorrhagia; and history of pelvic inflammatory disease (PID), tubal ligation, and physical/sexual assault.
Dyspareunia (pain during sexual activity) occurs in 1% to 40% of women. Risk factors include female circumcision, history of PID, anxiety, depression, sexual assault, and postmenopausal status.
Noncyclic pelvic pain (with no relation to menses) occurs in 4% to 40% of women. Risk factors include anxiety, depression, prior cesarean section, pelvic adhesions, endometriosis, menorrhagia, and history of miscarriage or physical/sexual abuse.
BIOLOGY AND CLASSIFICATION OF PAIN PERCEPTION
Acute pain perception is an evolutionary protective mechanism causing reflexive withdrawal from noxious stimuli. Individuals with congenitally impaired pain sensation have shorter lifespans.
Pain receptors respond to intense mechanical stress or local inflammatory/pain mediators (e.g., histamine, bradykinin, substance P). That stimulus is transduced to an electrical impulse that is transmitted via A-delta (fast myelinated) and C-fiber (slow unmyelinated) dorsal root ganglion neurons to synapse in the dorsal horn of the spinal cord. Second-order pain neurons then cross the anterior commissure and travel via the lateral spinothalamic tract to the thalamus where they synapse again. Third-order pain neurons project from the thalamus to the insular cortex (emotional content), the anterior cingulate cortex (planning/motivational function), and the primary sensory cortex (primary pain perception).
Pain afferent pathways can be modulated in the brain and spinal cord by descending pathways that can augment or diminish pain sensation. The possible interactions between acute pain perception, chronic pain pathway activation, and higher level/emotional modulation of pain circuitry underlie the complex pathophysiology of CPP. Normal descending inhibition of dorsal horn synaptic activity, for example, is decreased in chronic pain syndromes such as irritable bowel syndrome. Emotional factors such as depression and anxiety also decrease the pain threshold.
Nociceptive somatic pain (e.g., postoperative pain, trauma, inflammation) is produced by heat, cold, mechanical, and chemical stimuli. Deep somatic pain is detected within muscles, ligaments, and bone. Deep visceral pain from internal organs is poorly localized and has some overlap with somatic sensory tracts in the spinal cord, causing “referred pain.” The T10 to L1 afferent visceral pain fibers that innervate the uterus, adnexa, and cervix also supply the lower ileum, sigmoid colon, and rectum. Pelvic pain sensations can originate in any of those closely related structures.
Neuropathic pain (e.g., postherpetic neuralgia, diabetic neuropathy, nerve entrapment, Taxol chemotherapy-induced peripheral neuropathy) is due to peripheral or central nerve damage causing a malfunction in pain detection. It is commonly perceived as a chronic burning or tingling pain and produced from both local and systemic processes.
Current pain theory incorporates the Descartean concept of sensory specificity (i.e., a single stimulus is conducted along a dedicated pain pathway) and more recent ideas regarding the modulating influence of emotional, cognitive, cultural, attentive, and suggestive factors on both initial transmission and ultimate perception.
Psychogenic pain (e.g., somatization) is another possible etiology in a complete biopsychosocial model, representing the physical manifestation of unresolved emotional or psychological conflict.
It can be difficult to determine whether a patient has a symptom of nociceptive stimulation or an ongoing malfunction of pain perception or both. Acutely painful
processes, for example PID, may eventually resolve but leave permanently remodeled pelvic structures (e.g., adhesions) that can cause chronic pain. An extended inflammatory stimulus (e.g., inflammatory bowel disease) can lead to higher order pain sensitization and hyperesthesia. Pain associated with intense emotional content (e.g., childhood sexual abuse) can alter neurocognitive development, leading to hypervigilance and heightened pain sensation.
Although gynecologists often think of CPP as originating from either gynecologic or nongynecologic sources, it may be more helpful to take a broader view. Anatomic localization (e.g., abdominal wall, bowel, bladder, perineum), affected organ system (e.g., gastrointestinal, genitourinary, musculoskeletal, psychiatric), and type of pain (e.g., somatic, visceral, neuropathic, psychogenic) are possible diagnostic paradigms.
EVALUATION OF CHRONIC PELVIC PAIN
The evaluation of CPP starts with a complete medical history and the goal of establishing an enduring therapeutic physician-patient relationship.
History and Physical Exam
Prior records (including past history, test results, operative notes, and pathology reports) should be reviewed to avoid redundant tests or procedures and to gauge the effectiveness of prior interventions and progress over time.
Pain inventory questionnaires can be helpful in recording subjective and objective data and may increase the efficiency of initial data gathering. Useful resources are available from the International Pelvic Pain Society (IPPS) at www.pelvicpain.org. Pain questionnaires are helpful in allowing the patient to develop a coherent and relevant narrative before appearing at the office and allow rapid review of symptoms, permitting the interview to focus on pain issues. A personal body pain map is extremely helpful in focusing the differential and examination.
Adequate time should be allotted for a complete medical and psychosocial history without rushing the patient. A detailed review of systems, including genitourinary, gastrointestinal, musculoskeletal, and psychoneurologic questions, is important.
Establish a detailed understanding of the intensity, location, character, and duration of the pain and any association with intercourse, menstruation, defecation, recent or distant surgery, radiation treatments, or abdominopelvic infections. Precipitating and relieving factors should be reviewed.
Screening for physical or sexual abuse, domestic violence, and other psychosocial stressors (e.g., death of loved one, divorce) should be completed. Twenty percent to 60% of patients with CPP report a history of sexual or childhood abuse. A complete mental health history and depression screening are helpful; mood and personality disorders are frequently comorbid with CPP. It is not clear whether these problems are a cause or result of pain. Increased depression scores, however, correlate with increased pain scores, so simultaneous treatment is most effective.
Current, usual, and worst pain can be recorded using a pain scale (e.g., visual analogue scale). Associated symptoms such as weight loss, hematochezia, and perimenopausal/postmenopausal bleeding should prompt a thorough investigation for malignancy.
The physical exam begins with a general and neurologic assessment. Fully explain the plan and exam techniques to relieve anxiety and promote patient cooperation and comfort. The IPPS physical exam form or similar tools may be useful for recording the complete assessment. The exam should help narrow the differential, rule out systemic disease or neoplasm, and suggest additional testing.
Evaluate the general appearance, including dress, nutrition, posture, apparent age, gait, and pain behaviors. Evaluate posture (both seated and standing) and gait (for any hip height and leg length discrepancy).
Ask the patient to indicate the precise location of her pain. If she is able to use a single finger, a discrete source is more likely than if she uses a broad sweeping motion of the entire hand.
Note the presence of scars or hernias on abdominal exam. Gently attempt to elicit pain with palpation of the skin, fascia, or muscle. Especially note any reproducible tenderness. Appropriate trigger point mapping should be performed if fibromyalgia is in the differential.
Look for Carnett sign (i.e., increased abdominal tenderness when the patient lifts her head and shoulders in the supine position) suggesting abdominal wall rather than intra-abdominal pathology. Pain with the Beatty maneuver (i.e., thigh abduction against resistance) may suggest piriformis syndrome. The obturator sign (i.e., pain with flexion and internal rotation of the hip while lying supine) and the psoas sign (i.e., pain with hip flexion against resistance) can indicate inflammation or dysfunction within those muscles. The straight leg raise test evaluates radiculopathy or intervertebral disc disease. The FAbER test (i.e., pain with flexion/abduction/external rotation of the hip) assesses hip and sacroiliac joint pathology.
A thorough neurologic examination, including sensation, muscle strength, and reflexes, may be required. Examine the spine for scoliosis while the patient is sitting, standing, walking, and bending at the waist.
The gynecologic exam starts with external observation and then palpation with cotton swabs to define hyperesthetic areas (even if the skin appears normal). Colposcopic examination of the vulva and vestibule may be helpful. Light touch and pinprick sensation testing of the vulva is required.
Start the internal examination with a single-digit vaginal exam. Assess the vestibule, vaginal walls, rectum, urethra, bladder trigone, pubic arch, pelvic floor muscles, cervix, and vaginal fornices. Initial assessment of the uterus and adnexa are performed with a single digit as well.
Visual inspection of the vaginal vault can begin with a single speculum blade. Assess the vaginal cuff or cervix, cervical os, paracervix, and vaginal mucosa.
Finally, perform a bimanual exam of the uterus, adnexa, and other pelvic contents followed by rectovaginal exam. Fecal occult blood testing may be indicated. The bimanual exam, being the most invasive part of the evaluation, should be performed last. Some patients will be unable to tolerate any additional evaluation following the bimanual exam.
Imaging and Laboratory Testing
Imaging and diagnostic testing are tailored to the differential.
Pelvic ultrasonography is of little benefit unless uterine or adnexal pathology is suspected. Transvaginal imaging may better assess the pelvic structures than the transabdominal approach.
Magnetic resonance imaging can be helpful in selected cases, especially if adenomyosis is suspected.
Plain x-ray of the chest, spine, abdomen, or joints or computed tomography scan is rarely indicated.
Colonoscopy can assess colorectal cancer, inflammatory bowel disease, diverticulosis, and invasive endometriosis. It is indicated in cases with persistent diarrhea or hematochezia.
Cystoscopy and evaluation for interstitial cystitis/bladder pain syndrome are frequently indicated early in the workup.
Laboratory testing is guided by the history and physical and may include urine pregnancy test, vaginal pH and wet mount, gonorrhea and chlamydia polymerase chain reaction, complete blood count, erythrocyte sedimentation rate, thyroidstimulating hormone, rapid plasma reagin, hepatitis B surface antigen, HIV test, urinalysis/microscopy, and urine culture. There is no standard laboratory panel for CPP. Serum cancer antigen 125 testing is not useful unless a cancer workup is initiated. Endocrine testing for follicle-stimulating hormone, estradiol, and gonadotropin-releasing hormone (GnRH) stimulation test may be indicated for suspected ovarian remnant syndrome.
Laparoscopy and Consults
Although pelviscopy is performed for more than 40% of CPP cases, it should be employed only when noninvasive evaluation is completed and for cases in which a diagnosis can be reasonably anticipated. Laparoscopy is not a substitute for a complete history and physical or for diagnoses that can be made without a procedure. Most causes of CPP are not detectable by laparoscopy. It is most commonly performed when endometriosis or other structural pathology is suspected.
Selected evaluation by neurology, gastroenterology, anesthesiology, urology, psychiatry, or physical therapy consultants can provide important multidisciplinary perspective and assist in forming a complete treatment plan. Often, patients have been through a long, tedious, and piecemeal evaluation by multiple providers followed by redundant diagnostic and treatment failures. Performing a complete and multidisciplinary assessment from the start may reach a successful outcome more efficiently and reassure a demoralized and anxious patient. In addition, some tests are only appropriately obtained via consultation, such as nerve conduction studies or electromyography, if they are necessary.
DIFFERENTIAL DIAGNOSIS OF PELVIC PAIN
The differential diagnosis of pelvic pain is extensive, and many patients deserve multiple diagnoses.
Selected causes of CPP are listed in Table 30-1. Previously undiagnosed medical illness should also be considered, such as neoplasia, sickle cell disease, hyperparathyroidism, urolithiasis, lead/mercury intoxication, lactose intolerance, chronic constipation, chronic appendicitis, and chronic fatigue syndrome.
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