Most cases of musculoskeletal endometriosis exist without evidence of pelvic disease. The symptoms and signs of disease follow a somewhat predictable course dictated by the anatomic site of involvement. Surgical treatment is most often successful.
Two cases of the posterior left thigh have been reported [1, 2], as well as two cases of the right thigh, one anteriorly , and one laterally . One case report of endometriosis of the right gluteus maximus exists . The patients ranged in age from 24 to 36 and had noticed progressive pain or localized swelling over the course of months to years. Symptoms were typically worse during menses in most cases. Physical examination would typically show a hard, rubbery, often tender mass, in most cases, although computed tomography (CT) scan was required to diagnose a deeper lesion . Local aggressive surgical excision was curative without the need for postoperative medical therapy in all but one case . Cutaneous implantation of endometriosis in the surgical scar is possible .
A 5cm X 7cm painful soft tissue mass posterior to the right fibular head which appeared over the course of seven months in a 32-year-old black woman was not associated with neuropathy or vascular involvement . The pain and swelling increased during menses. Surgical exploration found the mass extended from the posterior head of the fibula under the lateral head of the gastrocnemius and completely surrounded the peroneal nerve. A biopsy showed endometriosis. The pain and swelling decreased quickly during danocrine therapy but recurred within two weeks of stopping treatment, but decreased again when treatment was resumed.
A 45-year-old nulliparous woman with right foot drop for six years developed a painful 8cm X 15cm swelling of the right lateral thigh . CT scan showed that this connected through the obturator foramen with a pelvic soft tissue tumor. The thigh tumor was partially removed in two operations and gonadotropin-releasing hormone (GnRH) agonist therapy given for six months. This was associated with an increase in the size of the lateral thigh swelling as well as the size of the pelvic tumor by magnetic resonance imaging (MRI) scan. The serum CA-125 level was 1990 IU/ml. At reoperation, the right trochanter major was found to be invaded by the tumor, with extension into the marrow. The thigh tumor was almost completely removed, but the pelvic tumor was not. The ovaries were removed and were normal. Bleeding into the pelvic tumor several months later was associated with anemia and a CA-125 level of 10,232. She died two months later of suspected pulmonary embolus.
A 27-year-old nullipara noticed a small slightly painful lump of the left side of her neck which had been growing for about a year . A 2cm ovoid rubbery, mobile mass was removed and microscopy showed endometriosis in the secretory phase. Pelvic and pulmonary examinations were negative.
Inguinal canal endometriosis
Cullen, 1896, gave the first English-language report of endometriosis of the inguinal canal . This entity usually represents nodular endometriosis (or 'adenomyoma') arising from the round ligament or from the fascial structures surrounding the external inguinal ring with surrounding fibromuscular metaplasia presenting as a painful tumor. Cullen mentions a similar case reported by von Recklinghuasen in the same year. Cullen's microscopic plates clearly indicate what would today be considered endometriosis. Because of the catamenial pain and the resemblance to eutopic endometrium, he postulated that the tumor rose from Müllerian rests.
Sampson later reported three cases of symptomatic inguinal endometriosis, the patients complaining of painful lumps of the groin which steadily grew in size with increased pain during menses. The preoperative diagnosis was inguinal hernia in two cases. Two were on the right side, and all were treated by local excision with good symptomatic relief. In one case, endometriosis was densely adherent to the femoral vein . In only one of his cases was the adenomyoma attached to the round ligament and significant pelvic endometrosis was present in two of the women but none in the third. Because none of his cases had any direct contact with the peritoneal cavity or seemed to spring directly from the round ligament, he postulated vascular or lymphatic spread as the mode of origin.
A literature review of 30 cases , and a series report of six cases , indicate that 90% of inguinal endometriosis is right-sided, and 91% of patients have coexistent pelvic endometriosis. A nodule can sometimes be misdiagnosed as an indirect inguinal hernia when it is present near the external inguinal ring. Occasionally, such nodules may be attached to the pubic tubercle , and radiate pain toward the hip.
In virtually all cases of endometriosis of the groin region, the pathology has been recognized by physical examination alone. Treatment by local excision allows histologic diagnosis and produces symptomatic relief in virtually all cases, with recurrence being rare.
Central nervous system endometriosis
A 26-year-old woman had a five year history of generalized lower extremity muscle and pains with moderate lumbosacral pain radiating to the left leg for two years. Pain increased monthly about five days before menses. Headache, nausea, vomiting, stiffness of the neck and back and a fever caused hospital admission for suspected meningitis. Lumbar puncture showed normal pressure and red blood cells. A myelogram showed a mass at the level of L-1 and L-2. Laminectomy found a round tumor inside the dural sac on the left, measuring up to 1.5cm in diameter. It was adherent to the roots of the cauda equina and two nerve roots were sacrificed for its removal. Photomicrographs illustrating the lesion show clear evidence of endometriosis. The pain was relieved although skin anesthesia in dermatomes L-1 and L-2 on the left side remained. Pain and myelogram evidence of recurrence of the tumor recurred within three months and the patient was treated with progesterone for symptomatic relief .
A 27-year-old female patient (referred to as a peasant by the original authors in China) had progressively worsening lower extremity and lumbar pain for ten years. Weakness and dysuria eventually appeared and the patient eventually could not stand. MRI showed a tumor at the L-4 level of the spinal canal and at surgery the tumor was fused to the cauda equina so that complete removal was impossible. Microscopy confirmed endometriosis. Permanent danocrine therapy was begun and the patient was asymptomatic at two years follow-up .
A 28-year-old woman had a two years history of cyclic low back and groin pain. MRI showed a mass 2.6cm X 1.3cm X 1.4cm in dimension beneath the dura of the lumbar spinal canal. It was incompletely removed. Laparoscopy showed pelvic and intestinal endometriosis and gonadotropin-releasing hormone (GnRH) agonist therapy was administered for 12 months, with decreased pain resulting. Two years later a second operation was done for recurrent symptoms and a tumor 5cm X 1.7cm x 1.9cm was found with involvement of the cauda equina. Total excision was completed and microscopy confirmed endometriosis. The uterus tubes and ovaries were removed and the patient was treated with postoperative androgen. Her cyclic pain and sphincter dysfunction resolved .
A 20-year-old woman had a three year history of right sided occipital headaches unrelated to menses culminating in a severe headache and generalized seizure. An electroencephalogram showed generalized moderate slowing over the right temporal area. CT showed a well-circumscribed lesion of the right parietal area. Angiography showed the mass to be avascular. At craniotomy, a greenish-brown cystic lesion was seen on the surface of the parietal lobe, filled with thick chocolate-colored fluid. The entire lesion was excised and danocrine was given for six months. She appeared cured at one year after surgery .
Peripheral nervous system endometriosis
Endometriosis on or near the sciatic nerve is the most common site of involvement of the peripheral nervous system by endometriosis. Approximately 90% of cases are right-sided. Patients may complain of pain in a sciatic distribution occurring just before and during menstruation, sometimes with motor dysfunction of the affected extremity [20, 21, 22, 23, 24]. The sciatic pain may become chronic in some. Endometriosis usually involves the pelvic portion of the roots of the sciatic nerve without actual invasion of the nerve, although cases of endometriosis within the sheath of the sciatic nerve after it exited the pelvis has been reported, with treatment through a skin incision over the right buttock [20, 25].
While three cases of successful medical treatment of sciatic endometriosis have been reported, one with danocrine , another with GnRH agonist , and the third with progestins  most cases have been treated surgically. At surgery, a pocket sign may be present (Fig. 1) . At the bottom of the pocket will be found a small fibrotic mass which will be adherent to the internal iliac vein near the bifurcation of the common iliac vein or to the roots of the sciatic nerve lateral to the vein, or to both (Fig. 2). Surgery by laparoscopy or laparotomy will be very difficult, and it is necessary to be acquainted with the anatomy of the deep pelvic sidewall and pelvic floor (Figs 3-7). The bottom of the pocket will not evert as will pockets of the cul-de-sac, because the nodule at the bottom of the pocket is firmly fused to underlying structures. In approaching the bottom of such a pocket laparoscopically, it is more efficient to make an incision posterior to the ureter and approach the bottom of the pocket from a medial direction (Fig. 3). Ligation of the internal iliac artery or vein may be necessary for proper exposure (Fig. 8). The fibrosis involving vascular structures can be intense and use of a cell-saver during surgery is recommended. The surgeon should be comfortable with repair of large arterial or venous structures with vascular suture material.
A pocket sign of the right broad ligament. The ureter forms the medial margin of the edge of the pocket opening. Small superficial hemorrhagic lesions of endometriosis are seen on the medial right broad ligament as well as on the right uterosacral ligament near its insertion into the posterior cervix.
The tip of the suction-irrigator is at the posterior edge of a 1.5cm nodular mass attached by dense fibrosis to the internal iliac vein, which is not clearly seen. The inferior roots of the sciatic nerve are hidden behind the nodule and the vein.
Normal anatomy of the right pelvic sidewall. The peritoneum has been opened: (a) areolar tissue which surrounds the right external iliac vein; (b) obturator nerve; (c) obturator vein; (d) hypogastric vein which is invested in some residual areolar tissue; (e) uterine artery; (f) ureter.
Same patient as in Fig. 3. The grasper is elevating the right obturator vein and the tip of the grasper is against the region of obturator internus. Note the obturator vein joining another more posterior vein to form a larger vein. The right ischial spine is hidden beneath tissue (*). The pudendal nerve (arrow) is seen traversing behind the ischial spine through the greater sciatic foramen. The roots of the sciatic nerve cannot be seen.
Deep view of the right posterior pelvis. (a) cut edge of peritoneum adjacent to right side of the rectum; (b) pelvic plexus; (c) right internal iliac vein; (d) right internal iliac artery. Anatomic variations are possible in this area.
Close-up view of the right pelvic plexus. This neurological area is important for bladder and bowel function. Unilateral damage during dissection of endometriosis invading this area can result in permanent bladder atony.
The right superior gluteal artery (*) is seen leaving the pelvis through the greater sciatic foramen.
The anterior branch of the internal iliac artery, commonly called the hypogastric artery, has been ligated with blue Vicryl sutures (a), and divided to better investigate the posterior pelvic sidewall. The ureter is seen medially (b). A deep branch of the internal iliac vein (c), and the right obturator nerve (d), are also seen.
One case of endometriosis of the right obturator nerve treated by laparotomy has been reported (Fig. 9) , and another has since been encountered and treated laparoscopically. In both cases, the nerve was encircled by endometriosis and fibrosis without invasion. Since the obturator nerve is shallower in the pelvis, it is easier to reach compared to the sciatic nerve. Fibrosis can be intense, but large vascular structures are rarely involved so the dissection for neurolysis is easier.
Two cases of endometriosis of the liver have been reported in women aged 21 and 37 years [31, 32]. Both patients presented with epigastric pain and the younger had episodic pain and nausea and vomiting. Examinations of the liver by CT and ultrasound scans were abnormal in both cases. Laparotomy was used to remove the cystic process from the left liver lobe in one patient, and from the right lobe in the other. Danocrine therapy was given postoperatively in both cases. The older patient also had a left ovarian endometrioma cyst and pelvic peritoneal endometriosis. The posterior edge of the right lobe of the liver as it joins the diaphragm can sometimes be superficially involved by endometriosis spreading from disease of the adjacent diaphragm.
One case of endometriosis of the pancreas has been reported .
Most cases of cutaneous endometriosis present as tender nodules in surgical scars following surgery on the uterus, especially Cesarean section. The diagnosis is suggested by cyclic pain and tenderness during menses, with slow growth of the nodule in some patients over the course of months or years [34, 35, 36]. The lesions typically involve the rectus fascia on one side or another of low transverse incisions and may occasionally tract down toward the bladder. Actual connection with the uterus is rare. Treatment is by local excision, which will usually include a portion of rectus fascia. In cases of scar endometriosis following supracervical hysterectomy by laparotomy, a cervicocutaneous fistula of endometriosis surrounded by dense fibrosis may result, with symptoms of bleeding or discharge at the skin opening . Treatment is by excision of the fistulous tract.
Endometriosis has been diagnosed in a needle tract 18 months following amniocentesis for midtrimester abortion in a woman taking oral contraceptives. She noted a midline lower abdominal wall mass which became tender during menses. She discontinued the pill after seven years but the size and character of the mass did not change. A biopsy confirmed endometriosis but the patient was lost to follow-up before complete excision could be arranged . Transplantation of endometrium to the umbilicus occurred in 2 of 10 women who underwent laparoscopic hysterectomy with removal of strips of endometrium and myometrium through the unprotected umbilicus. Symptoms began two years after laparoscopic hysterectomy and included umbilical pain and cyclic swelling of the umbilicus. Diagnosis was obvious by a combination of physical examination, ultrasound, MRI and thin-needle aspiration. One of these women had undergone hysterectomy in the late luteal phase of the hormonal cycle, the other during menstruation. Local excision was performed in both cases . Vulvar endometriosis has been reported in a nulligravida , as well as in episiotomy scars [41, 42]. Treatment is by local excision.
Endometriosis in the thorax can involve either the parietal pleural surface or the parenchyma of the lung itself. Endometriosis of the pleural surface of the thorax occurs on the right in over 90% of cases and can be associated with chest pain associated with menses and shortness of breath . Pneumothorax will occasionally occur. Some cases reported as thoracic endometriosis could actually be considered as diaphragmatic endometriosis. Almost 50% of patients in one retrospective review had coexisting pelvic endometriosis . Treatment has usually been surgical, ranging from chest tube treatment of pneumothorax to thoracotomy with pleurectomy. Danocrine therapy was successful in one case.
Involvement of the lung parenchyma by endometriosis is uncommon and can cause painless or painful catamenial hemoptysis [43, 44, 45]. Bronchoscopy during an episode of hemoptysis helped isolate the responsible lung segment in one case with a presumptive diagnosis , but was rather inconclusive in another . One patient's symptoms worsened during estrogen therapy but improved somewhat with androgen therapy . Simple chest x-rays have allowed diagnosis in two cases [44, 45], resulting in treatment by thoracotomy and segmental pulmonary resection.
Endometriosis in males
In older males with metastatic prostate cancer treated by orchiectomy and high dose estrogen therapy with chlorotrianisene, embryonic rests of Müllerian cells can be stimulated to bleed, sometimes heavily. Cystoscopy revealed ulcerated lesions of the bladder surrounding and obstructing the left ureter in one case in which transurethral resection was incomplete . Hematuria did not respond to birth control pill therapy but eventually ceased when all hormonal therapy was stopped. Repeat cystoscopy showed a smaller mass beneath an intact mucosa. In another case where hematuria was investigated with cystoscopy, an ulceration near the right bladder dome was found and treated by segmental resection of the affected area of the bladder .
One case of endometriosis of the prostate causing hematuria was diagnosed by transurethral resection in a 78-year-old man treated with chlorotrianisene after a diagnosis of prostatic cancer based on an abnormal prostate exam . Adenocarcinoma of the prostate was not confirmed histologically and the patient died of a stroke at the age of 91.
Vicarious menstruation is the bleeding occurring during menses in an area remote from the uterus, such as the eye [49, 50], or nasal membranes. When disease processes, such as ulcerations, inflammation, or foreign bodies, have been ruled out, it is thought that vicarious menstruation may simply be due to the response of abnormally fragile capillary beds responding to the vasodilating effects of estrogen .
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