HOWARD, FRED M. MS, MD; EL-MINAWI, AHMED M. MD, MSc, PhD; SANCHEZ, REINALDO A. MD
Laparoscopy under local anesthesia is not new,1 but its use in diagnosis to localize areas of tenderness possibly responsible for chronic pelvic pain is relatively new. Palter and Olive2 first described this technique, usually called conscious pain mapping, in 1996. They studied 11 women with pelvic pain and found that ten had diffuse visceroperitoneal tenderness. Demco3 also published findings with it (he called it patient-assisted laparoscopy), mostly in women with endometriosis-associated pelvic pain. He found that most women localized or mapped their pain to their endometriotic lesions and the surrounding peritoneum.4
The rationale for conscious pain mapping is that it might allow specific identification of lesions that cause chronic pelvic pain and specific surgery, or it might avoid unneeded surgery in women who do not map their pain to a specific lesion. Published studies of conscious pain mapping are still limited, especially in patients who have had unsuccessful diagnoses and treatments, so we report the findings of our first 50 cases of conscious pain mapping.
Materials and Methods
Starting in 1996, conscious pain mapping was offered to all women referred to the Rochester Endometriosis and Pelvic Pain Center who were candidates for diagnostic laparoscopy after thorough evaluation to exclude nongynecologic diagnoses. Fifty women consented and had conscious pain mapping between June 1996 and August 1999. Those cases form the basis of this report. Approximately 40 women declined conscious pain mapping during the study period, mostly in the first 18 months.
Procedures were done by the senior author (FMH) in the ambulatory surgery center at Rochester General Hospital with an anesthesiologist in attendance. Before sedation, the patient was placed in low lithotomy position, and an indwelling bladder catheter was inserted using topical local anesthesia at the urethra. A uterine manipulator was placed using a four-quadrant cervical block, if the patient had a uterus. If not, a lubricated sponge stick was placed in the vagina. Women were given intravenous propofol at that point to induce conscious sedation. Dosage varied based on the anesthesiologist's judgment of the patient's anxiety level and responsiveness. Ten milliliters of 1% lidocaine buffered 1:9 with sodium bicarbonate were injected in a fan pattern at the umbilicus, then the abdomen was elevated and a 2-mm or 5-mm disposable trocar was inserted. Two-millimeter trocars were used in 42 (84%) cases and 5-mm trocars in seven (14%). The laparoscope was introduced to confirm intraperitoneal placement. Ten milliliters of buffered 1% lidocaine were injected suprapubically while the abdomen was insufflated with up to 1 L of carbon dioxide, which allowed a view of the suprapubic lidocaine injection to the level of the peritoneum. A suprapubic 2-mm or 5-mm trocar was then inserted under direct view. A blunt probe was introduced through the suprapubic trocar to do the mapping. Pressure and traction were used as stimuli for mapping. An area of small bowel was stimulated to allow the women to establish baseline pain levels. They were instructed preoperatively to use a verbal analog scale of “0” to “10” to numerically rate their pain. They also were instructed to identify any stimuli that reproduced their usual pain. After baseline from small bowel stimulation was established, an attempt was made to map systematically the internal inguinal rings, round ligaments, bladder dome, anterior cul-de-sac, broad ligaments, fallopian tubes, ovaries, pelvic sidewalls, posterior cul-de-sac, uterus, and appendix, and any visible lesions. It was not possible to see the posterior cul-de-sac in all cases. Often, if a positive lesion was identified, the patient had difficulty continuing the evaluation because of persistent severe pain even after stimulation of the lesion was terminated. In some cases, topical lidocaine was irrigated onto the positive lesion, which generally blocked the sensitivity of the lesion and decreased pain.
Positive mapping cases were defined as those in which one or more lesions were found that correlated with some or all of patients' pain. A primary positive site was defined as a site or lesion that correlated with some or all of the patient's pain and had the highest verbal analog scale severity rating. A secondary positive site was defined as a site or lesion that correlated with the patient's pain, but had a lower verbal analog scale rating than the primary site.
A conscious pain mapping procedure was defined as successful if the patient tolerated the procedure and consistently identified the source(s) of her pain, or stated that no sources could be identified. Complete view of the entire pelvis was not considered essential for the procedure to be successful, but all areas had to be accessible to laparoscopic probing, including the posterior cul-de-sac.
Pain levels were measured using a 10-cm visual analog scale with endpoint labels “no pain” and “worst pain ever.” Preoperative pain levels were measured in the month before conscious pain mapping and postoperative pain levels were measured at regular intervals postoperatively. Visual analog scale pain levels at last follow-up visit were those reported in this study as postoperative pain levels.
Data were analyzed with SPSS for Windows 10.0 (SPSS Inc., Chicago, IL). Dichotomous variables were compared by χ2 and Fischer exact testing. Nonparametric data were compared using the Wilcoxon rank sum test.
Ages of patients in this series ranged from 17 to 51 years, with a median age of 34 years. Duration of pain ranged from 11 to 180 months, with a mean of 79 months. Racial distribution was 44 white, five black, and one Hispanic. Nine women were nulliparous, five were para 1, 30 were para 2, and six were para 3.
Before referral to the Rochester Endometriosis and Pelvic Pain Center, 46 (92%) women had laparoscopies, 22 (44%) had laparotomies, and 13 (26%) had hysterectomies. All women had at least one prior procedure for pelvic pain. Preoperative visual analog scale pain levels ranged from 6 to 10, with a mean ± standard deviation (SD) of 8.7 ± 1.2, and 45 (90%) women had pain levels of 8 or more.
Conscious pain mapping was successful in 35 cases (70%) (Table 1). Twenty-nine women had positive sites mapped; 18 had one positive site, ten had two positive sites, and one had four positive sites, for a total of 42 positive sites. In six other women, conscious pain mapping was successful, but they had diffuse visceroperitoneal tenderness that appeared to reproduce their chronic pelvic pain and did not have any specific, discrete positive lesions or sites. Primary and secondary positive lesions or sites are summarized in Table 2. Of the 42 lesions or sites mapped, adhesions and endometriosis accounted for almost half (19 or 45% of sites mapped). Specific viscera (bladder, ovary, vaginal apex, uterus, round ligament, and fallopian tube) also accounted for a significant portion of positively mapped sites (15 or 36% of positive sites in ten of 35 successfully mapped women). Combined with six women with diffuse visceroperitoneal tenderness, these data suggest that 16 women, 45% of those successfully mapped, may have had chronic visceral pain syndrome.
Endometriosis was diagnosed visually in 20 women, but confirmed histologically in only 13 (65%). There were 15 cases with successful conscious pain mapping and a visual diagnosis of endometriosis, and in these cases endometriotic lesions were mapped as painful sites in seven. In all seven of those cases there was histologic confirmation of the diagnosis. In the remaining eight successfully mapped cases in which endometriotic lesions did not map positively, there was histologic confirmation of the diagnosis in only two cases. Thus, seven of nine cases with successful conscious pain mapping and histologically confirmed endometriosis mapped their pain to endometriotic lesions, compared with none of six successfully mapped cases in which the visual diagnosis of endometriosis was not histologically confirmed (P = .007, Fischer exact test).
Adhesions accounted for 11 of 42 positively mapped sites (Table 2), more than any other specific lesion or site and were present in 27 of 50 women (54%). In six women, adhesions directly caused failed conscious pain mapping. Among 21 remaining cases, 15 were mapped successfully and one or more adhesions mapped as painful in seven (47%) cases.
Several miscellaneous sites appeared to correlate with and reproduce patient pain at conscious pain mapping. Fifteen women mapped pain specifically to visceral structures, with bladder, ovary, and vaginal apex the most common (Table 2). Other uncommon sites included a sciatic hernia, leiomyoma, hernia repair site, and postoperative peritoneal cyst.
In 13 cases with positive lesions it was necessary to apply lidocaine solution topically to primary and secondary positive sites to continue the procedure. In 12 of 13 primary sites and in all six secondary sites, lesions became nontender. No other positive sites were located in these cases.
Forty women had operative laparoscopy under general anesthesia immediately after conscious pain mapping (Table 3). The only complication of conscious pain mapping was omental perforation with the umbilical trocar in eight cases, but there were no further sequelae caused by those perforations.
Postoperative follow-up averaged 12.6 months (SD 9.7 months; range 0–39 months), with four cases (8%) lost to follow-up. Mean visual analog scale pain level postoperatively was 5.5 ± 3.7 (range 0–10), a change of 3.2 points from the mean preoperative visual analog scale (95% confidence intervals [CI], 2.2, 4.3; P = .001, Wilcoxon rank sum test). Forty percent of women had pain levels of eight or more postoperatively, compared with 90% preoperatively. Twenty-two women (44%) had decreased pain (a decrease of visual analog scale scores of 2 or more) postoperatively, and eight (16%) were pain-free. Fifteen women had further surgery during follow up. Six had hysterectomies, and at least one each had inguinal herniorrhaphy, presacral neurectomy, adhesiolysis (two women), myomectomy, resection of endometriosis, release of ilioinguinal nerve entrapment, and repeat conscious pain mapping (two women).
Preoperative visual analog scale pain levels correlated with the duration of pelvic pain (Pearson correlation coefficient .302, P = .03), but postoperative visual analog scale pain levels did not significantly correlate with preoperative duration of pain (Pearson correlation coefficient .127, P = .53).
Results of published series of diagnostic conscious pain mapping in women with chronic pelvic pain are summarized in Table 4. Palter and Olive2 first reported conscious pain mapping in an office setting using 2-mm cannulas and instruments. They reported three types of pain, the first of which was a localized sharp, stabbing pain with manipulation of viscera or a lesion, which could be relieved with topical local anesthetics. We noted that type of pain in our subjects with positive conscious pain mapping to a specific lesion or viscera, although we did not block the pain with topical local anesthetic in all cases because of concern that if local anesthetic is applied too soon it might alter subsequent findings during mapping. The second type of pain they observed was a crampy, dull pain or feeling of fullness related to CO2 insufflation, which was relieved by lowering intra-abdominal CO2 pressure. We did not observe that type of pain, but we limited intra-abdominal pressure to less than 10 mmHg and less than 1 L volume. The third type of pain was an immediate, sharp, burning sensation with the onset of insufflation, which did not interfere with success of the procedure. We observed that type of pain in some women, but found that it interfered with success of the procedure because it led to intolerable pain and defeated conscious mapping in five cases. It is possible that the pain was caused by carbon dioxide, which has been found to be particularly irritating to the peritoneum and caused more pain than nitrous oxide.5 However, a recent randomized clinical trial that compared nitrous oxide versus carbon dioxide insufflation did not show any difference in intraoperative pain.6
Palter and Olive2 found generalized visceral hypersensitivity in all areas of the pelvis and abdominal cavity in ten subjects. We saw that in only six of 35 successful cases. Our patients with diffuse visceroperitoneal hypersensitivity also seemed to have it only in the pelvis, not the small bowel or peritoneum outside the pelvis. We cannot explain the difference between our observation and that of Palter and Olive. We believe that patients with diffuse pelvic visceral and peritoneal tenderness might be diagnosed with chronic visceral pain syndrome, a diagnosis suggested for chronic pain syndromes believed to be visceral.7 It might be that many patients with no apparent diagnosis at diagnostic laparoscopy under general anesthesia had chronic visceral pain syndrome. Further evaluations are needed to confirm those proposals.
Palter and Olive2 compared their cases to 16 women with infertility who had microlaparoscopy. They noted that mean pain levels with conscious pain mapping in women with chronic pelvic pain were two points higher (on a ten-point scale) than pain levels in infertility patients who had diagnostic microlaparoscopy.
Demco3 published findings for 100 women who had conscious pain mapping with positive pain mapping in all but two of the successful cases. Our technique for conscious pain mapping was similar, although Demco did paracervical blocks before mapping and we did not. Our avoidance of anesthetizing the uterus might account for our finding uterine visceral pain in several cases.
Almeida and Val-Gallas8 reported that all but two of their 50 patients who had conscious pain mapping had positive findings. Seventeen women had prior laparoscopies for chronic pelvic pain, but none had prior laparotomies. Thirty-three had no prior surgical evaluations or treatments for chronic pelvic pain, distinctly different from our study. All our patients had prior surgical evaluations or treatments for chronic pelvic pain. We suspect that the marked differences between our results and those of Almeida and Val-Gallas and of Demco are most likely because of significant differences in populations studied. The only visceral pain reported by Almeida and Val-Gallas was from the appendix. We did not observe appendiceal tenderness in any of our initial 50 cases. Our results with conscious pain mapping and those reported show that in some patients with endometriosis or adhesions, the lesions are tender to direct palpation or stretching, which reproduces patients' pain. Although it is generally accepted that endometriotic lesions can cause pain, conscious pain mapping results were consistent with the clinical observation that not all endometriotic lesions produce pain and tenderness. Demco tried to correlate the appearance of endometriotic lesions with tenderness at conscious pain mapping and found that 84% of red lesions, 76% of clear lesions, 44% of white-scar lesions, and 22% of black lesions were painful.9 Our series of patients with tender endometriotic lesions was too small for any reliable comparative data; however, our data confirm that a visual-only diagnosis of endometriosis is unreliable10 and that histologically confirmed endometriotic lesions are much more likely to positively map at conscious pain mapping than lesions visually consistent with endometriosis but without histologic confirmation.
Whether adhesions can produce pain is more controversial. The findings in all published series of conscious pain mapping that adhesions can be tender and that stimulation can reproduce patients' pain strongly support the conclusion that some adhesions cause abdominopelvic pain. As with endometriosis, those data also suggest that adhesions are not always a source of pain in women with chronic pelvic pain and adhesions.
From our data it appears that conscious pain mapping is worthwhile even in complex patients who have had surgical evaluation and treatment for pain. In such women, as in other series of patients with chronic pelvic pain, adhesions and endometriosis are still common diagnoses, but conscious pain mapping findings suggest that visceral pain syndrome is also a frequent diagnosis.
Chronic pelvic pain is a multifaceted and complicated problem, and it is not appropriate to assume that findings with conscious pain mapping directly translate into cause and cure. In a series from our center that evaluated laparoscopic diagnosis and treatment of 65 patients, before the introduction of conscious pain mapping, we found that endometriosis and adhesive disease were the most common diagnoses, with prevalences of 38% and 34%, respectively.11 Those data are similar to gross visual diagnoses in the current series of 40% and 54%, respectively, for endometriosis and adhesions, but conscious pain mapping only confirmed that those lesions were associated with patients' pain in 14% and 16%, respectively. In our previous series, after laparoscopic evaluation and treatment without conscious pain mapping, 78% of women had decreased pain and 45% were pain-free, compared with the current series with conscious pain mapping, in which 44% had decreased pain and 16% were pain-free. A significant difference between the populations in the two studies is that only half of the women in the previous series had prior evaluations and treatments for chronic pelvic pain.
The clinical value of conscious pain mapping diagnostically and therapeutically cannot be stated based on this or other observational series. We believe our series allowed us to avoid unnecessary operative laparoscopies in seven of 35 successfully mapped cases. Whether it improves outcomes in women with chronic pelvic pain, by decreasing unnecessary surgical interventions or improving pain relief by more specific medical and surgical treatments, probably will require a randomized trial.