Introduction
Chronic pelvic pain (CPP) in women is defined as noncyclical pain lasting greater than 6 months and can affect all ages. It is associated with impairment in sexual function and emotional and behavioral health. Patients present with symptoms suggestive of pelvic floor, urinary, bowel, sexual, or gynecological dysfunction. These include dysmenorrhea, dyspareunia, dysuria, and pain along the groin, vagina, or perineum. Among the many sources of CPP commonly seen in clinical practice are endometriosis, pelvic inflammatory disease, nonmalignant adnexal masses, vulvodynia, pudendal neuralgia, neuropathic postsurgical, and myofascial pain along the pelvic brim. Pain that fails to improve with established treatment algorithms for well-defined disease processes may be deemed refractory.
The World Health Organization estimates the global prevalence of CPP to be 5.7%–26.6%. This number is likely an underrepresentation given many countries do not have data to report. Determining an underlying etiology to develop an effective treatment plan often requires a multidisciplinary team approach including primary care physicians, gynecology, urology, gastroenterology, behavioral health, and pain management specialists.
CPP is often associated with endometriosis; however, many patients do not have an obvious source for pain. A study across 10 countries demonstrated an average diagnostic delay of 6.7 years for endometriosis in women with predominantly CPP symptoms, and this was longer in women with elevated BMI. Physical limitations with activity and subfertility are accompanied by significant psychosocial impairment. , The economic burden stems primarily from the loss of productivity and decreased quality of life. , Pelvic inflammatory disease (PID) results from genital tract infections that cause inflammation and is most frequently seen in women ages 15–25. The incidence is difficult to quantify, as it is not a reportable disease. Various demographic, clinical, and behavioral risk factors such as smoking have been identified as predictors of CPP after PID. A sequela of PID are adhesions that may be associated with pain and may result in mechanical obstruction of the gastrointestinal tract or torsion of reproductive organs. Nonmalignant adnexal masses such as leiomyomas, tubo-ovarian cyst have a high lifetime incidence ranging between 5% and 71% based on age, ethnicity, BMI, and comorbidities such as diabetes and hypertension. , Vulvodynia has prevalence 8% and often goes underdiagnosed as demonstrated by an incidence of 4.2%.
This chapter will focus on refractory pelvic pain that has failed to improve with conventional medical management of the primary diagnosis being treated.
Etiology and Pathogenesis
Unlike acute pain that is caused by inflammation, trauma, or infection resulting in afferent nociceptive input, the underlying etiology of CPP is complex with varying neuropathic, somatic, visceral, and musculoskeletal contributions ( Fig. 3.1 ). The pathogenesis is genetic, endocrine, behavioral, and central nervous system mediated.
Genetic mechanisms are inferred by the increased incidence of other chronic pain syndromes in patients with CPP. , The endocrine system has also been implicated in the pathogenesis of CPP as dysregulation of sex hormones is associated with certain disease states such as endometriosis and can modulate nociception and pain perception. , The behavioral mechanism suggests an underlying trigger such as a negative emotional experience. Central sensitization may develop and lead to an amplified pain response and reduced nociceptive thresholds of the dorsal horn neurons. This can lead to sensory disturbances and organ malfunction. Visceral stimuli that are normally subthreshold can be perceived and processed as noxious stimuli, an example of visceral hyperalgesia.
Many of the structures in the pelvis receive their innervation from the superior hypogastric plexus, which is located in the retroperitoneum and situated bilaterally along the anterior surface of the L5 vertebral body. It comprises sympathetic and parasympathetic visceral afferent and efferent projections. The caudal ends of the sympathetic chains then converge to form the ganglion impar, which provides sympathetic innervation to pelvic viscera as well as carry both sympathetic and nociceptive fibers from the perineum, distal rectum, perianal region, and distal urethra among others. Parasympathetic innervation of the pelvis originates from the S2 to S4 roots via the pelvic splanchnic nerves. Somatic innervation, including afferent sensory fibers, also arises from the S2–S4 nerve roots.
Clinical Presentation
There may be a myriad of signs and symptoms upon presentation. Patients report abdominopelvic pain that is deep, nagging, aching, cramping, sharp, burning, or lancinating. The pain may radiate along the back, groin, or thighs in a nondermatomal pattern. Patients often describe dysmenorrhea, menometrorrhagia, dysuria, pain along the pelvic brim, or vulva upon palpation. Dyspareunia is particularly taxing on both the patient and their sexual partner.
Diagnosis
A comprehensive history and physical examination remain the mainstay for initial diagnosis. Common causes that may result in persistent pelvic pain should be evaluated and ruled out. A focused psychosocial history looking for recent stressors such as loss of a family member or prior negative experiences should be obtained to evaluate for coexisting depression and anxiety. An organ-based review should be detailed with attention to urologic, gastrointestinal, gynecological, and musculoskeletal involvement. Finally, red flag signs indicating systemic disease, including postmenopausal bleeding, postcoital bleeding, pelvic mass, involuntary weight loss, and hematuria, should be excluded.
Should there be symptoms suggestive of a well-known disease, treatment of the causing disease is initiated according to specific guidelines and best practices. In the majority of patients without an identifiable disease process, subspecialty consultation should be considered if organ-specific symptoms predominate. Without organ-specific sources of pain, a consult to a pain management specialist is encouraged.
Commonly obtained imaging includes transabdominal and transvaginal ultrasound , and pelvic computed tomography (CT) scans that may be beneficial in evaluating any underlying pelvic masses. Diagnostic laparoscopy is considered the gold standard for diagnosis in patients with clinical concern for endometriosis, adenomyosis, and leiomyosis. Laboratory testing including LH, FHS, estradiol, urine analysis, vaginal swab, and stool culture may be considered if clinically appropriate.
Differential Diagnosis
The differential diagnosis should first seek to rule out infection and malignancy. The remaining causes of CPP may be divided by organ system. Urological pain syndromes include interstitial cystitis and urethral pain. Gynecologic causes include dysmenorrhea, endometriosis, PID, adnexal masses, and injuries related to childbirth. Gastrointestinal sources include hemorrhoids, anal fissures, and irritable bowel syndrome. Musculoskeletal and neuromuscular etiologies include pudendal neuralgia, pelvic floor muscular dysfunction, and vulvodynia.
Physical Exam Findings
Physical examination should be targeted at identifying the muscles, nerves, and organs likely responsible for the patient’s pain to elucidate the source. There are few pathognomonic findings on examination of chronic pelvic pain patients. The abdomen should be inspected for any gross deformity or masses. Prior surgical incisions should be evaluated to ensure appropriate healing and for overlaying skin dysesthesia or allodynia. Gentle palpation with a single digit along the rectus sheath and obliques for point tenderness should be performed to assess the degree of musculoskeletal involvement. A Carnett’s test is conducted with a patient lying supine while the examiner places a finger over the abdominal musculature. The patient is asked to elevate the legs or head to contract the rectus abdominis. A positive test resulting in increase in pain suggests a muscular, or nerve entrapment etiology opposed to true visceral pain. Deeper palpation can be useful in evaluating adnexal tenderness or masses.
Examination of external genitalia and speculum exam should be performed with care due to hyperalgesia or allodynia. Palpation along the pelvic brim musculature may elicit the pain due to trigger points along the obturator internus and externus muscles. Palpation along the ischial spine may reproduce a sharp neuropathic pain due to irritation of the pudendal nerve. A spine examination of the lumbar facet joints, sacroiliac joints, hip joints, and lower back and buttock musculature is helpful in ruling out predominant musculoskeletal sources of pain.
Treatment
A multimodal approach to treatment is often necessary and should incorporate physical and behavioral therapy, pharmacological treatment, interventional, and surgical management as necessary to ensure treatment success ( Fig. 3.2 ).
Pharmacologic
Pharmacological treatment for CPP necessitates an individualized and interdisciplinary approach. A straightforward algorithmic approach is often unsuccessful due to the variable underlying etiologies and coexisting medical and psychosocial comorbidities. Treatment recommendations are often extrapolated from the treatment of other chronic pain conditions to help guide management. Limited data surrounding the initial pharmacological treatment is available for women with CPP.
The first step in the pharmacological treatment of CPP focuses on identifying the underlying pain mechanism (somatic, neuropathic, visceral, sympathetic). These categories often overlap and demand a multimodal strategy to provide a synergistic analgesic effect thereby improving the likelihood of successful treatment. Initial pharmacological therapy is usually limited to nonsteroidal antiinflammatory drugs and muscle relaxants as they are generally well tolerated with limited side effects. Acetaminophen is often added if a predominantly somatic presentation is suspected, despite minimal evidence of efficacy.
Patients with predominantly neuropathic and sympathetic features are more likely to respond to tricyclic antidepressants, anticonvulsants (i.e., gabapentinoids), and selective norepinephrine reuptake inhibitors. Combination therapy with different neuropathic agents has been shown to be more effective in CPP. Specifically, gabapentin alone or in combination with amitriptyline resulted in greater pain relief than amitriptyline alone.
For patients with cyclic exacerbation of their CPP, hormonal therapy with combined estrogen-progestin contraceptive, progestin-only contraceptives, or gonadotropin-releasing hormone analogs may be considered. Hormonal therapy should be managed by obstetrics and gynecology. Chronic opioid therapy is not recommended for the treatment of CPP.
Injections
Interventional management should be considered to increase patient functionality and when conservative therapy has failed to provide adequate pain relief. Targeted injections can aid in the diagnostic evaluation and offer therapeutic benefits for patients with complex pain presentations. A careful review of the postprocedural pain diary may offer clinical insight by estimating the underlying pain process (visceral, neuropathic, or sympathetically mediated) and its degree of contribution to the presenting pain syndrome.
Superior hypogastric plexus block
The superior hypogastric plexus (SHP) contains both sympathetic and parasympathetic fibers located bilaterally along the anterior surface of the L5 vertebral body. Primary visceral afferents from the descending colon, rectum, bladder, ureters, uterus, and adnexal structures travel proximally alongside these sympathetic nerves and ganglia allowing them to be accessible for the diagnostic block. The SHP block is most commonly done with fluoroscopic guidance; however, CT can also be used. It is typically targeted from a posterior paramedian approach at the level of the lower one-third of the fifth lumbar vertebral body and upper one-third of the first sacral vertebral body with the needle tip advanced to the anterior vertebral body ( Fig. 3.3 ). The SHP block has been demonstrated to be effective in the management of nononcological chronic pain due to endometriosis. , If the diagnostic block is successful, therapeutic neurolysis with alcohol and phenol have both been completed with improvement for patients with nonmalignant pelvic pain.
Ganglion impar block
The termination of the sympathetic chains forms a single fused ganglion known as the Ganglion Impar (GI) or Ganglion of Walther. Primary visceral afferents from the perineum, distal rectum, distal urethra, vulva, perianal area, and distal one-third of the vagina travel alongside visceral sympathetic fibers converging at the GI.
Multiple approaches to target the ganglion impar have been described, but the most popular technique is the transcoccygeal approach due to its shortest trajectory. Although the patient is in the prone position, a spinal needle is placed through the sacrococcygeal ligament with the needle tip slightly posterior to the rectum ( Fig. 3.4 ). Extra care should be taken to not advance needle tip into the rectum. Contrast is injected to confirm appropriate placement. Local anesthetic with or without steroids may be injected.
