Introduction
Chronic pelvic pain can originate from various etiologies such as chronic prostatitis, pelvic inflammatory disease, endometriosis, vulvodynia, interstitial cystitis, and surgery in the pelvis. In this chapter, we focus on postsurgical pelvic pain in both men and women.
Chronic Postsurgical Pelvic Pain in Men
Inguinodynia: Inguinal hernia repair is the most common surgery in the United States and worldwide. Each year more than 2 million of these procedures are performed worldwide, and there are over 800,000 cases done in the United States annually. , Inguinal hernia is more common in males than females. The prevalence of inguinal hernia is 90.8% in males and 9.2% in females. Inguinal hernia repair is the most common identifiable factor that is associated with inguinodynia. Inguinodynia is a form of chronic postsurgical pain defined as persistent groin pain lasting for more than 2 months following surgery. It is estimated that 10%–12% of all inguinal hernia repair patients develop moderate to severe inguinodynia, and of these patients, approximately 6% develop chronic debilitating pain that negatively impacts their activities of daily living and employment. ,
Chronic Orchialgia: Chronic orchialgia is described as testicular discomfort that can range from a heavy sensation in the groin to frank pain. A complaint of orchialgia is considered to be chronic when the discomfort lasts for more than 3 months. , , Vasectomy is a well-known risk factor for the development of chronic orchialgia. Fifty million men undergo vasectomy procedures annually worldwide, with over 500,000 cases being performed in the United States. , It is estimated that 1%–2% of men who undergo vasectomies will develop chronic orchialgia, with some studies reporting incidence rates as high as 54%. Besides vasectomy, surgical repair of the varicose pampiniform plexus can cause nerve damage as well and lead to chronic orchialgia. Nerve injury from inguinal hernia repairs can also cause chronic orchialgia.
Pelvic Pain from Other Postsurgical Etiology: There is a paucity of data in the literature on the incidence of pelvic pain after other types of pelvic surgeries in men such as radical prostatectomy and cystectomy. These surgeries often require extensive lymph node dissection in the pelvis and dissection around major nerves such as the obturator nerve. , For instance, nerve-sparing prostatectomies require careful dissection of the neurovascular bundle around the lateral wall of the prostate. These surgical maneuvers can potentially lead to nerve injury and the development of neuropathic pain. Furthermore, postoperative adhesions that develop after these surgeries can lead to visceral or somatic pain in the pelvis.
Chronic Postsurgical Pelvic Pain in Women
Chronic Postsurgical Pain after Cesarean Section: Chronic pain after the cesarean section was not well studied until 2004. Numerous studies have emerged since then, establishing the association between chronic pain and cesarean deliveries. , Chronic pain after cesarean section persists for 3 months after delivery and can be at the scar site, localized deep in the pelvis, or at the anterior abdominal wall below the umbilicus and buttock. Based on the current literature, the prevalence of chronic pain, either at the scar site or in the pelvis, at 6 months postcesarean section ranges from 12% to 18%. The prevalence of disabling pain has ranged from 4% to 7% with an associated decline in the quality of life for the mother and mother–child relationship. With rates of cesarean section on the rise, recognizing the importance of prevention and treatment of postoperative pelvic pain is paramount.
Chronic Postsurgical Pain after Hysterectomy: Hysterectomy is a common surgery in women. According to the Center for Disease Control, there are over 600,000 hysterectomies performed every year in the United States. Similar to the cesarean section, hysterectomy is associated with the development of chronic pain in the pelvis and at the scar site. Posthysterectomy pelvic pain in women between the age 18 and 49 is 14% in the United States and 24% in the United Kingdom. The prevalence is reported to be higher in other countries. For example, based on Danish Hysterectomy Database, posthysterectomy pelvic pain was reported by 31% of patients 1 year after surgery.
Etiology and Pathogenesis
The mechanisms underlying the development of chronic postsurgical pelvic pain is complex and poorly understood. Almost all forms of chronic postsurgical pain have attributes of both neuropathic and nonneuropathic pain. , Neuropathic pain after surgery is thought to be caused by damage to nerves. In the case of inguinodynia and vasectomy-related orchialgia, injury to the iliohypogastric, ilioinguinal, and genitofemoral nerves have been implicated. , , In surgeries involving deep pelvic organs such as prostatectomy, cystectomy, hysterectomy, and cesarean section, injury to nerves that course through the pelvis (i.e., obturator nerve) are thought to mediate the development of postsurgical pelvic pain. , , In animal studies, it has been shown that damage to nerves results in the release of inflammatory chemicals. These inflammatory chemicals alter gene expression and produce a state of continuous noxious signal transmission to the higher brain that results in long-term neuroplastic changes.
Damage to nerves can occur intraoperatively from surgical manipulation, leading to subsequent stretch or crush injuries. The use of electrocautery in the nearby vicinity can also cause thermal injury and accidental transection of the nerves. One common etiology for intraoperative nerve injury is from entrapment of the nerve in suture or tacks used to secure the mesh in the case of hernia repair. Nearby neurovascular structures are vulnerable to injury postoperatively as well. Postoperative changes such as fibrosis, meshoma, seroma formation, and adhesions can entrap and impinge nearby neurovascular bundles.
In addition to neuropathic pain, patients can also experience visceral and somatic pain. Somatic pain can occur with recurrence of the pathology such as recurrence of an inguinal hernia. More commonly, somatic pain arises due to the formation of excessive fibrotic tissue, meshoma, or postoperative adhesion tissues pulling and distorting nearby structures such as the bowel and ovaries. Surgical changes can also entrap the spermatic cord or impinge on the venous flow of the testicle and spermatic cords. This can lead to orchialgia and pain during sexual intercourse. , Periostitis pubis is characterized by persistent lower abdominal pain and tenderness over the pubis. This is thought to occur due to periosteal anchoring of the mesh during inguinal hernia repair.
Clinical Features
Patients with chronic postsurgical pelvic pain present with a wide array of symptomatology. Neuropathic pain usually manifests as neuralgia, hypo/hyperesthesia, hyperalgesia, paresthesia, and allodynia. Patients commonly describe their symptoms as stabbing, burning, pulling, shooting, and prickling in nature. The duration of these symptoms can range from intermittent to constant. ,
As previously mentioned, depending on the etiology, these symptoms can be localized to the deep pelvis, anterior abdominal wall below the umbilicus, inguinal canal, the scrotum or labium, and anterior thigh. In the case of inguinodynia, patients often find their pain to be worse with ambulation, stretching of the upper body, stooping, hyperextension of the hip, or sexual intercourse. , , Pain generally improves with laying down and with flexion of the hip or thigh. In the case of chronic orchialgia, patients present with heaviness in the scrotum, pain involving the testicles, and pain with sexual intercourse. These patients generally report that their scrotal pain is aggravated when sitting down. Pain from other pelvic surgeries can present as neuropathic pain at the incision site or deep in the pelvis. Many patients will also report dull and aching discomfort in the pelvis described as pounding, gnawing or pulling. Patients with periostitis pubis from inguinal hernia repair often have tender points at the level of the pubis and associated abdominal pain.
Diagnosis
Clinical features of chronic postsurgical pelvic pain are nonspecific and are shared by a wide array of pathologies. Therefore, evaluation of a patient with chronic pelvic pain after surgery should begin with a broad differential, and a diagnosis is made after excluding other critical pathologies. Evaluation should begin with a comprehensive clinical history and physician exam, ascertaining any history of recent pelvic surgery. One should be cautious to diagnose chronic postsurgical pelvic pain within the first few months after surgery because wound recovery can take several months even after an external surgical scar has healed, and the perceived pain may emanate from the healing process.
Clinical history should delineate the nature and chronicity of the pain. Chronic postsurgical pelvic pain can be neuropathic or nonneuropathic in nature and can be intermittent or persistent; however, the symptoms must be present for 2–3 months to receive a formal diagnosis of chronic postsurgical pelvic pain. Imaging studies can be helpful to rule out other pathologies and assess the presence of meshoma and excessive fibrotic tissues. , Ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) have all been utilized as well. , MRI has been touted as the superior imaging modality for delineating the cause of pain. , , Electromyography can detect and rule out peripheral nerve injury. Diagnostic peripheral nerve blocks can also be helpful to identify the source and nerve distribution of the pain. ,
Treatment
Noninterventional Therapies
As previously described, chronic postsurgical pelvic pain is complex, with emotional, cognitive, and social factors playing a large role in the development and evolution of the pain syndrome. Therefore, treatment for this condition should be multimodal in approach and include components of psychotherapy, physiotherapy, acupuncture, and mind-body therapies. ,
Pharmacologic treatment options include nonsteroidal anti-inflammatory drugs and steroids. , , These agents work by reducing inflammation, but due to their side effect profile, long-term use is limited. The most commonly used agents for associated neuropathic pain disorders are gabapentinoids (i.e., gabapentin and pregablin), selective serotonin and norepinephrine reuptake inhibitors (SNRIs), and tricyclic antidepressants. , , Gabapentinoids act as voltage-gated calcium channel antagonists that decrease the release of glutamate and are used for the treatment of many neuropathic pain syndromes, including fibromyalgia; it has also been shown to decrease the incidence of chronic pain development when given preoperatively. , Duloxetine and venlafaxine are SNRIs recommended as first-line agents for neuropathic pain syndromes by the International Association for the Study of Pain. , These agents are low cost and have the added benefit of treating coexisting mood disorders in addition to neuropathic pain.
Because traditional neuropathic agents take time (up to several weeks) to have an adequate analgesic effect, weak opioids such as tramadol can be utilized for episodic exacerbation during titration of these agents. In general, we do not recommend the use of chronic opioids for the treatment of chronic nonmalignancy pain syndromes. However, when judiciously utilized, the lowest effective dose should be given with regular follow up. ,
Nerve Blocks
Nerve blocks are utilized for diagnostic and therapeutic purposes in the setting of inguinodynia and orchialgia. , Historically, nerve blocks were performed using anatomic landmarks; however, most blocks are now performed under direct visualization using ultrasound guidance.
Ilioinguinal nerve and iliohypogastric nerve provides overlapping sensory innervation involving the hypogastric region, the inguinal crease, the upper medial thigh, the mons pubis, part of labia, and the anterior aspect of the scrotum. , Ultrasound-guided ilioinguinal nerve and iliohypogastric nerve blocks are effective for inguinodynia. Fig. 8.1 shows an ultrasound image of these two nerves. In a study by Thomassen and colleagues, the authors demonstrated prolonged pain relief for up to 20 months with ultrasound-guided ilioinguinal and iliohypogastric nerve blocks for inguinodynia. It is important to note that due to the proximity of ilioinguinal and iliohypogastric nerves it is difficult to isolate and block the two nerves separately. ,
Numerous case reports have demonstrated ultrasoundguided genitofemoral nerves block for orchialgia as well as inguinodynia; however, in most of these cases, the needle placement and block were distal to the site of injury or entrapment. , Genitofemoral nerve courses retroperitoneally before entering the inguinal canal; and therefore, any attempt to block this nerve proximal to the site of injury using anterior approach increases the risk of traversing the peritoneum. Currently, there is no case report that demonstrates ultrasound-guided technique for selective genitofemoral nerve block proximal to the site of nerve injury. With that said, CT-guided transpsoas genitofemoral nerve block has been demonstrated and is a promising technique to safely block genitofemoral nerve proximal to the site of nerve injury.
While inguinodynia and orchialgia are mediated by the ilioinguinal, iliohypogastric, and genitofemoral nerves, pain from the deep pelvis is mediated by the superior hypogastric plexus, ganglion impar, and pudendal nerve. Although less commonly seen, if postoperative pain in the distribution of these nerves is suspected, a block may be done for diagnostic and treatment purposes.
Neurolysis Techniques
Neuroablation with chemical neurolysis, cryoablation, or pulsed radiofrequency can be used to mitigate various forms of chronic postsurgical pelvic pain conditions. Such neurolytic techniques are attempted when nerve blocks have proven to be beneficial and patient desires longer relief.
Cryoablation : Cryoablation involves percutaneously placing a hollow probe near the targeted nerve and applying freezing temperatures, causing nerve destruction via Wallerian degeneration where the axon and myelin sheaths are selectively destroyed leaving behind intact perineurium and epineurium. , , This prevents neuroma formation and the subsequent development of deafferentation pain. Numerous studies have demonstrated the efficacy of cryoablation for the treatment of inguinodynia. In a study by Fanelli and colleagues, nine patients with inguinodynia underwent cryoablation of ilioinguinal or genitofemoral nerve under direct surgical visualization and experienced a 77.5% pain reduction from this procedure. In another report by Campos and colleagues, cryoablation of the femoral branch of the genitofemoral nerve was successfully used to treat inguinal pain. Cryoablation can provide up to 1 year of sustained relief.
Radiofrequency ablation : Radiofrequency ablation can also be used to treat inguinodynia and orchialgia. Pulsed radiofrequency ablation uses bursts of high-intensity currents to heat the nerve tissue up to 42°C, thereby inducing thermal destruction of the nerve. The nerve tissue is allowed to cool between the bursts of heat, thereby preventing uncontrolled tissue damage and the subsequent development of neuroma, neuritis, and deafferentation pain. Rozen and colleagues published two reports where pulsed radiofrequency was applied to the T12, L1, and L2 nerve roots for the treatment of inguinodynia. , Patients experienced 75%–100% pain reduction that lasted for 6–9 months. , Pulsed radiofrequency ablation has been used to ablate peripheral nerves as well. In their studies, Cohen and Foster successfully treated three patients with inguinodynia by ablating the ilioinguinal nerve and iliohypogastric nerves. To perform the ablation, Cohen and colleagues used anatomic landmark techniques for needle placement and used sensory neurostimulation to confirm the targeted nerve. Patients reported complete pain resolution at 6 months follow-up. In another study by Mitra and colleagues, inguinodynia was treated with pulsed radiofrequency ablation of the ilioinguinal nerve using anatomic landmark and sensory neurostimulation techniques. In their study, the patient reported a significant reduction in visual analog scale (VAS) score from 8/10 to 3/10 at 3-month follow-up.
Chemical neurolysis: Compared to cryoablation and pulsed radiofrequency ablation, chemical neurolysis with phenol or alcohol is less frequently reported in the literature. These neurolytic agents are more prone to cause nearby tissue damage; therefore, their use is typically reserved for cancer-related visceral pelvic pain. , However, neurolysis of the superior hypogastric plexus and the ganglion impar have been utilized for severe cases of refractory visceral pelvic pain from nonmalignant etiologies.
Neuromodulation
Neuromodulation is an alternative approach for the treatment of chronic postsurgical pelvic pain refractory to pharmacologic and other interventional therapies. Neuromodulation techniques include stimulation of the spinal cord, dorsal root ganglion, and peripheral nerves. , Traditionally based on the “gate control” theory of pain where nonpainful sensory inputs effectively “gate” off ascending pain signals, stimulation-based therapies deliver electrical impulses to ameliorate pain perception. The mechanisms and details of spinal cord stimulators are discussed in more detail in other chapters of this textbook. Traditionally used for chronic back pain, radicular pain, and complex regional pain syndrome, neuromodulation therapies are now being applied for the treatment of chronic pelvic pain syndromes as well.
Peripheral Nerve and Dorsal Column Stimulation : Numerous case reports and case series have demonstrated the efficacy of peripheral nerve and dorsal column stimulation for treating inguinodynia and orchialgia. In a case report, Rosendal and colleagues used low-frequency peripheral nerve stimulation of the cutaneous branch of the ilioinguinal nerve and the genital branch of the genitofemoral nerves to treat chronic scrotal pain following a hydrocele repair. The patient’s VAS score decreased from 9/10 to 2/10 on the numeric rating scale at a 7-month follow-up. In another report, Banh and colleagues used ilioinguinal nerve stimulation to treat ilioinguinal neuralgia following hernia repair. In this report, patients had minimal pain on 3-months follow-up and were taken off all analgesics, including opioids.
Yakovlev and colleagues used traditional tonic spinal cord stimulation with percutaneous electrode leads placed at the T7–T9 level to successfully treat inguinodynia. In their study, the patient remained pain-free at 1-year follow-up.
Dorsal Root Ganglion Stimulation: Stimulation of the dorsal roots ganglion (DRG) is an alternative treatment modality that has recently increased in popularity, particularly for the treatment of chronic pain disorders in areas that have been difficult to treat with traditional dorsal column stimulation, such as the foot, abdomen, and groin. The DRG is a collection of sensory nerve cell bodies that are located bilaterally at each spinal level and can be accessed percutaneously for focused stimulation of particular dermatomes. Each lead contains four stimulating electrodes that are advanced from the epidural space to the intervertebral foramen where the DRG is located as shown in Fig. 8.2 . The number and the respective levels at which the leads are placed is typically dependent on the dermatomal distribution of the patient’s pain as shown in Fig. 8.3 . Moreover, compared to dorsal column stimulators, DRG stimulation requires less overall energy since the cerebrospinal fluid layer at the level of the DRG is relatively thin. There is also less risk of the patient experiencing unwanted paresthesia with positional changes compared to dorsal column stimulators.
