Beyond the tip of the iceberg: A meta‐analysis of the anatomy of the clitoris

An understanding of ranges in clitoral anatomy is important for clinicians caring for patients including those who have had female genital mutilation, women seeking genital cosmetic surgery, or trans women seeking reconstructive surgery. The aim of this meta‐analysis is to investigate the ranges in clitoral measurements within the literature. A meta‐analysis was performed on Ovid Medline and Embase databases following the PRISMA protocol. Measurements of clitoral structures from magnetic imaging resonance, ultrasound, cadaveric, and living women were extracted and analyzed. Twenty‐one studies met the inclusion criteria. The range in addition to the average length and width of the glans (6.40 mm; 5.14 mm), body (25.46 mm; 9.00 mm), crura (52.41 mm; 8.71 mm), bulb (52.00 mm; 10.33 mm), and prepuce (23.19 mm) was calculated. Furthermore, the range and average distance from the clitoris to the external urethral meatus (22.27 mm), vagina (43.14 mm), and anus (76.30 mm) was documented. All erectile and non‐erectile structures of the clitoris present with substantial range. It is imperative to expand the literature on clitoral measurements and disseminate the new results to healthcare professionals and the public to reduce the sense of inadequacy and the chances of iatrogenic damage during surgery.


| INTRODUCTION 1.| The anatomy and function of the clitoris
The clitoris is a multiplanar structure located within the urogenital triangle that transverses the deep and perineal pouches (O'Connell et al., 2005).It is located deep to the labial fat, labia minora, and inferior to the pubic symphysis and arch (O'Connell et al., 2005).The clitoral complex is pyramidal in shape and maintains a consistent relationship with the urethra and vagina (O'Connell et al., 2008).
The clitoris has both external (glans and prepuce) and internal (body, paired crura, and bulbs of the vestibule) components.The prepuce, sometimes referred to as the hood or foreskin, is a layer of thin hairless skin that covers the distal end of the clitoris, the anterior layer is continuous with the labia minora.The glans is a cylindrical structure at the tip of the clitoris which is easily observed by retracting the prepuce and is the most superficial part.The body/corpora is shaped like a boomerang as it folds back on itself, meaning that it has an ascending and descending segment.The apex (most superior part of the body) is anchored to the pubic symphysis via the three-layered suspensory ligament, that maintains the 'bent' position (Botter et al., 2022).The body is composed of two corpora cavernosa, separated by an incomplete septum.The septum is an extension of the tunica albuginea, which is a fibrous connective tissue sheath that surrounds the corpora cavernosa superficially.The body bifurcates laterally into the left and right crura that follow the inferior border of the ischiopubic rami and are located deep to the respective ischiocavernosus muscles (Gordon et al., 2021;Jackson et al., 2019;O'Connell et al., 1998;O'Connell et al., 2005).Together, the body and crura are shaped like a wishbone.The paired vestibular bulbs are composed of erectile tissue that run parallel to the crura and are located deep to the bulbocavernosus muscles.The posterolateral margin of the bulbs is located adjacent to the paired greater vestibular glands (O'Connell et al., 2005;Di Marino & Lepidi, 2014;).The bulbs maintain a consistent relationship with the clitoral complex and can completely or partially fill the space between labia minora, body, and crura (O'Connell et al., 1998).
The mantra that the clitoris has the sole function of pleasure and orgasm has been perpetuated throughout history (Masters & Johnson, 1966).This reductionist ideology may have caused a lack of thorough studies regarding clitoral function and its evolutionary role in reproduction.Levin (2020) has recently elucidated that clitoral stimulation leads to a cascade of events that are intimately intertwined with the facilitation of conception.Clitoral stimulation leads to increased vaginal blood flow, lubrication, pO 2 , and temperature.Additionally, it partially neutralizes the basal vaginal acidity and activates vaginal tenting and ballooning, increasing the chances of conception (Levin, 2020).While it is important to note that clitoral orgasms do not result in conception, Levin's study starts to unravel the importance of clitoral evolutionary existence.

| The great "re-discovery"
The history of the anatomy of the clitoris has been described previously (Charlier et al., 2020;O'Connell et al., 2005;Park, 1997).In brief, Hippocrates, the father of medicine, initially described a small protrusion of the female genitals and called it the "columella" or "uvula" and stated that it functioned to protect the vaginal opening (Charlier et al., 2020;Hippocrates., 1751).While the clitoris, as an anatomical structure, was known to ancient Greek scholars, it is evident that this knowledge was lost through time.Perhaps this was due to mistranslation of terminology or that some scholars incorrectly assumed that the presence of the clitoris was a rare pathological anomaly (Charlier et al., 2020;O'Connell et al., 2005;Park, 1997).For example, Galen believed that the female genitalia represented a direct external copy of biological male anatomy where the penis was equivalent to the uterus, and the glans equivalent to the vaginal cavity, leaving no explanation or even mention of the existence of the clitoris (Galenus, 1550).
The first published anatomical dissection of the clitoris was performed by Charles Estienne, a French anatomist, who published his work in a dissection des parties du corps human in 1546 (Estienne, 1546;Mollendorf, 2011;Park, 1997).He used the phrase "membre honteux" (shameful member) to describe the structure and stated that it possesses a "glandular function…to enclose, retain, and receive some humidity in its natural sponginess" (Estienne, 1546).Despite Estienne's efforts, the official "re-discovery" of the clitoris is shrouded in controversy (Charlier et al., 2020;Park, 1997).Matteo Colombo, an Italian anatomist, described an organ that became turgid during mechanical stimulation or sexual arousal, stating it was the "principal seat of women's enjoyment in intercourse" in his work De re anatomica (Colombo, 1559).However, his own student Gabriele Falloppio insisted that Colombo had stolen his findings, stating that "modern anatomists have entirely neglected it" (Falloppio, 1561), a phrase that arguably still rings true today.In fact, Andreas Vesalius refuted Falloppio's 'discovery' and adamantly stated that this "useless" part was attributed to "hermaphrodites who otherwise have well-formed genitals" (Vesalius, 1564).While these scholarly men squabbled over the existence, or lack thereof, Gross (2022) affirms that the presence of the clitoris has been known by women for millennia.Indeed, a midwife, Jane Sharp (1671), described the sexual function of the clitoris in 1671 (Sharp, 1671).A year later, anatomist Regnier De Graaf (1672) published an accurate description of the clitoral structures, including the bulbs (De Graaf, 1672).Despite this, the neurovasculature was not fully described until 1844 by anatomist George Ludwig Kobelt (Charlier et al., 2020;Kobelt, 1844).Subsequently, interested parties had to wait until 2005, with work initiated in 1998, for a full and accurate anatomical description of the structures of the clitoris and its relationship to other genital structures (O'Connell et al., 1998;O'Connell et al., 2005).Utilizing MRI, cadaveric dissections, and findings from the literature, Helen O'Connell et al. (2005) confirmed that the clitoris is a "multiplanar structure consisting of a non-erectile tip, the glans, and erectile bodies (the paired bulbs, crura and corpora) …with a consistent relationship to the distal urethra and vagina" (O'Connell et al., 2005).
The representation of the clitoris in anatomy textbooks also has an intriguing history and is described by Hayes and Temple-Smith (2022).The relative size of the clitoris compared to other genital structures, and the number of labels depicting clitoral structures fluctuate throughout history (Moore & Clarke, 1995).Specifically, a fully labeled image of the entirety of clitoral structures was not published until the 40th edition of Gray's Anatomy (Hayes & Temple-Smith, 2022;Standring, 2005).Nowadays, only a quarter of specialist gynecological and textbooks report measurements for the clitoris (Adrikopoulou et al., 2013), mirroring a lack of accurate descriptions of variation in anatomical textbooks (Beni et al., 2022).

| The shameful organ
Anecdotal evidence suggests that throughout history, and even today, the word 'clitoris' can spark a visceral reaction of embarrassment or intrigue.This, in part, could be due to its lack of representation in medical and scientific literature and in the media (Beni et al., 2022).
How can one relatively small bodily structure be shrouded in so much mystery?How did it take anatomists hundreds of years to truly understand its structure (Charlier et al., 2020)?The answer lies in a multiplicity of sociocultural factors (O'Connell & Vikraman, 2015).Indeed, the majority of anatomists and clinicians were male until a few decades ago (Jefferson et al., 2015).In England, the right to study medicine was formally granted to women in 1915, and moral and ethical issues prevented men from taking a specialist interest in female reproductive anatomy (Jefferson et al., 2015).Moreover, the availability of female cadavers that were dissected by physicians or surgeons in medical schools and colleges was limited compared to males, as many of these bodies were sourced from executed males (Park, 1997).However, Harvard historian of medicine, Katharine Park devoted her whole research to the role of women in dissection.Her book "Cultures of Dissection and Anatomies of Generation" highlight how women were at the center of cadaveric dissection in the Middle-Ages, with multiple case-studies.The interest in the anatomy of women stemmed from a desire to understand the origins of life (Park, 1997).
Furthermore, it has been argued that the use of language to describe the clitoris and genitals alike has perpetuated a stigma that persisted for generations (Charlier et al., 2020;Draper, 2021).For example, the anatomical term "pudendum" which was formally used by Claudius Galen (129-216 BC) to describe both male and female external genitalia of both humans and animals, derived from the Latin word, pud ere, meaning "to be ashamed of."Conversely, Zdilla (2021) argues that the term pud ere has been taken out of context and the root term is inclusive of respect, modesty, virtue, awe, and veneration (Zdilla, 2021).Despite this, the dictionary definition of pudendum states that the word refers "especially to women" and the first edition of Terminologia Anatomica (1998) applied the Latin root only female anatomy (Draper, 2021).While the word pudendum was removed from Terminologia Anatomica in (2019), it remains commonly used in clinical practice, and is still used to describe the neurovasculature in both sexes (i.e., the pudendal nerve) (Draper, 2021).
The etymology of the clitoris is uncertain; however, the Greek translation (κλειτοριζ) is related to the word "hill."It could also be derived from the word "κλειτυς," which translates as the verb "shut" or "close" or the word "κλεις," which translates as "key" or "latch" (Williamson & Nowak, 1998).
Historically, the stigma and lack of understanding of the function of the clitoris led to the justification and, unfortunately, performance of clitoridectomies as a treatment for insanity, epilepsy, catalepsy, and hysteria (Elchalal et al., 1999;O'Connell et al., 2005).However, the removal of the clitoris is still performed worldwide (UNICEF, 2022), during the deeply rooted religious practice of female genital mutilation (FGM) (UNICEF Data, 2022; UNICEF, 2022).The practice can take different forms, which can be classified depending on the genital structures being removed or modified.Type 1 procedures include clitoridectomies, Type 2 procedures involve the removal of the clitoris and labia minora, while Type 3 procedures results in mutilation and infibulation (WHO, 2022).The rationale behind the practice is mainly societal and religious, often ignited by beliefs about what is considered appropriate sexual behavior for young women, as it allows the obtainment of premarital virginity and marital fidelity (WHO, 2022).The World Health Organization estimates that over 200 million women have been affected by FGM and is most prevalent in Africa, Asia, and the Middle East (WHO, 2022).It can result in long-term gynecological and obstetrics issues, not to mention loss of pleasure during sexual activity (Abdulcadir et al., 2016;El-Dirani et al., 2022;Lurie et al., 2020;WHO, 2022).It is important to underline that the practice of FGM is illegal in the United Kingdom and that each case should be reported to the authorities to allow appropriate safeguarding (Home Office, 2011).
Genital reconstructive surgery is an option for women suffering from FGM, despite the fact it is still not recommended by the Royal College of Obstetricians and Gynecologists, as current evidence suggests unacceptable complication rates without conclusive evidence of benefit (RCOG, 2015).However, recent studies have described the benefits of these procedures (Puppo, 2017;Wilson & Zaki, 2022).
Gender reaffirming surgeries and genital cosmetic surgeries are additional procedures that require a thorough understanding of vulval anatomy and its variations to reduce complications.Moreover, patients wishing to avail themselves of these surgeries should be informed on what constitutes normal variation to ensure acceptance of the results and their own anatomy.In fact, prior to cosmetic surgery, the American College of Obstetricians and Gynecologists recommends that clinicians reassure patients that size, shape and color of external genitalia vary considerably, prior to elective surgery (ACOG, 2020).Despite this, a study demonstrated that a quarter of general practitioners are not confident in evaluating the normality of female genital anatomy, which may impact patient care (Simonis et al., 2016).Perhaps this is due, in part, to the recycled photographs of anatomical models in the lithotomy position across major anatomical textbooks and a consistent lack of diversity of the genitalia represented (Beni et al., 2022).Furthermore, measurements regarding clitoral structures are lacking from most anatomy textbooks (Adrikopoulou et al., 2013;Beni et al., 2022).Furthermore, the National Institute of Clinical Excellence (NICE) impact report demonstrated that sexual health should be considered a fundamental part of health alongside well-being and quality of life (NICE, 2018), and a study by Public Health England highlighted that women consider reproductive and sexual health central to their lives (PHE, 2018).Indeed, a good understanding of genital anatomy is fundamental to achieving a satisfying sexual life (Nagoski, 2015).While a study demonstrated that the clitoris was the most readily recognized structure of biological female external genitalia by the public (Waldersee, 2019), one in 10 women remain distressed or worried about their sex life (PHE, 2018).It has been reported that a sense of female inadequacy is perpetuated by distorted images supplied by the pornographic industry and the mainstream media (Moran & Lee, 2014).
This has led some women to perceive that their own vulvar structures, including the clitoris, are inappropriate in shape and size, that may impair sexual satisfaction and wellbeing (Nagoski, 2015).A 2011 audit conducted in the United Kingdom, highlighted that distress caused by the patient's vulvar appearance was the cause of referral for labiaplasty in 71% of the cases analyzed (Deans et al., 2011).

| Aims
Therefore, this meta-analysis aimed to collate, for the first time, the published measurements relating to the erectile (body, crura, bulbs) and non-erectile (glans and prepuce) structures of the clitoris, and their relationship to other genital structures (external urethral meatus and anus) from cadaveric, living, and medical imaging (MRI and US) studies.The hope is that these data will be a useful guide to clinicians and the general public alike.

| Protocol and registration
This systematic review was submitted to the International Prospective Register of Systematic Reviews (PROSPERO) platform under protocol number CRD42021254598.The report of this study accords with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), which consists of a checklist of items recommended for preparing systematic reviews and meta-analyses.As this was a literature study, formal ethics approval was not mandatory.

| Inclusion criteria
Studies were included if they reported numerical data regarding clitoral measurements from healthy human participants.As cadaveric studies were utilized, data from women over 50, who may be postmenopausal were included.All published measurements were included if the study reported no significant difference ( p > 0.5) between a study and control group.

| Exclusion criteria
Measurements from prepubescent and adolescent females (i.e., participants under 18 years of age) were excluded.In addition, measurements from females with clinical conditions were excluded from the dataset if clitoral measurements were statistically different (p < 0.05) from control groups.Additionally, measurements were excluded if a study explicitly stated that they were not to be used as standard value.

| Information source
An electronic search was conducted in Ovid Medline and Embase from the creation of each database up until December 2021.To identify relevant studies, the Boolean operator "AND" and "OR" with the MeSH terms: ("clitoris" AND "anatomy" OR "structure" OR "topography" OR "Morphology") were utilized.The following categories were selected using the automatic 'limit' feature within the databases; "English language," "human" and "humans."Subsequently, a manual search from the reference lists in eligible articles to identify those relevant to this research was performed.

| Data extraction
All relevant demographic data including the authors, title, experimental modality of study (MRI); ultrasound (US); cadaveric; living), number of participants, age group and ethnicity were extracted.The type of fixative within the cadaveric studies was documented; in addition, details from patient studies were recorded.
The average (mean or median were applicable) and range (minimum and maximum) length and width of clitoral structures (glans, body, crura, bulb of vestibule, and prepuce) were reported, in addition to the distance from the clitoris to the external urethral meatus, vagina and/or anus.

| Study search
All results from the database search were screened by reading the title and abstract, and the eligibility criteria (as described in Section 2.2) were applied by three reviewers (R.B., A.S., and M.P.).Duplicate studies were removed.Thereafter, the full texts of all eligible studies were evaluated by three reviewers (R.B., A.S., and M.P).Any disagreements were resolved by discussion with an additional reviewer (G.L.).
All data (as described in Section 2.4) were extracted, summarized, and tabulated.The risk of bias was limited as all data were assessed and independently verified by two authors (S.J. and P.L).Any disagreements were resolved by an additional author (G.L).

| Meta-analysis
The overall mean measurement and range (minimum to maximum) for each clitoral structure was calculated using the average measurements from each study within Microsoft Excel.In studies where only the range was reported, the median was used in this calculation.If the range was unavailable, the 5%-95% interquartile range was reported if available.
Statistical analysis to compare the average measurements from different experimental modalities (MRI, US, cadaveric and living) was performed on Graph Pad Prism 9, if more than two measurements for each experimental modality were recorded.First, a Shapiro-Wilk test for normality was performed and subsequently a non-parametric Kruskal-Wallis (glans, body and distance between clitoral and external urethral meatus measurements) or Mann-Whitney test (crura length) was performed.Where fewer than two measurements were available for a particular modality, no statistical test was performed.

| PRISMA search results
The initial electronic literature research retrieved 2317 articles.Before the title and abstract screening, 1241 papers were excluded for not meeting the inclusion criteria (876) or were duplicates (365).After title and abstract screening, 865 reports were excluded.Two hundred and eleven full-text articles were further evaluated.Twenty-one studies met the inclusion criteria and were selected for analysis and data extraction (Figure 1).

| Number of participants and modality of study
In total, clitoral structures from 2432 biological females (n) aged 18-84 years-old were recorded (Table 1).Four studies (Suh et al., 2003 (n = 18); Abdulcadir et al., 2016 (n = 15); Vaccaro et al., 2014 (n = 20); Bowen et al., 2022 (n = 22) were performed through MRI (n = 87), two studies (Buisson et al., 2008  A summary of details from each publication, including the inclusion and exclusion criteria, was documented (Table 2).Additionally, details on the anatomical landmarks used to measure each structure (Table 3) and distance between other genital structures as document in the publications was recorded (Table 4).

| Key clitoral measurements
The average length and width of the glans was 6.40 mm (range 1.00-21.00mm) and 5.14 mm (range 2.00-32.00mm), respectively.
The average length and width of the body was 25.46 mm (range 5.00-59.00mm) and 9.00 mm (range 5.00-20.00mm), respectively.
The average length of the clitoral prepuce was 23.19 mm (range 5.00-40.00mm).
The average distance from the clitoral glans to the external urethral meatus was 22.72 mm (range 7.00-52.00mm).The average distance to the vagina was 43.14 mm.The average distance from the clitoris to the anus was 76.30 mm (and the 5%-95% interquartile range was 59.50-96.10mm) (Figure 2).

| DISCUSSION
This is the first meta-analysis to collate all recorded measurement of clitoral structures from MRI, US, cadaveric, and living people.This study confirmed clitoral structures present with a range of measurements that is not accurately represented in anatomical textbooks.
For example, the average length of the clitoral glans in this study was 6.40 mm (1.00-21.00mm), while the average length of the body was 25.65 mm (5.00-59.00mm).Only two anatomical textbooks have published empirical data on these structures and have published the combined length of the body and glans as 20.00 mm (Moore et al., 2014) or ranging from 30.00 to 40.00 mm (Paulsen et al., 2018).This study has revealed that these published figures are smaller than in-vivo measurements, as the combined average length of the body and glans from this study was 32.05 mm (6.00-80.00mm).
An objective decision was made to omit data from adolescent females under 18 years old, as they are still developing (Brix et al., 2019).Despite this, a study demonstrated that the median clitoral glans width in 44 adolescent females, aged 10-19 years-old, was 3.00 mm and ranged from 1.00 to 8.00 mm (Brodie et al., 2019).This length is smaller than that reported in this review (5.00 mm).Kreklau and colleagues grouped 15-24 years old and reported that the average length of the glans was 7.86 mm, slightly higher than our reported average (6.84 mm).We included data from studies that did not report a statistical difference from control groups.This included women without sexual dysfunction or with female sexual function index scores >3.6.Conversely, we omitted cohorts of data in which there was a statistically significant difference in clitoral measurements in women with pathological conditions, such as polycystic ovaries  et al., 2019).Furthermore, the distance between the clitoral glans and the anus was significantly greater in women with stress urinary incontinence (81.1 mm), compared to a control group (72.1 mm) (Ekmez & Ekmez, 2021).As part of the exclusion criteria, we omitted measurements from women who have experienced FGM.However, Abdulcadir et al. ( 2016) reported no significant difference in the width of the clitoral glans and length of the body.Despite this, they did find a significantly smaller clitoral and bulbar volume in women with FGM, compared to those without (Abdulcadir et al., 2016).While we have not reported on the volume of clitoral structures, studies performed using US demonstrated that clitoral volume can fluctuate throughout the menstrual cycle (Battaglia et al., 2008;Battaglia et al., 2009).
While Vaccaro et al. (2014) reported that a positive correlation between BMI and clitoral distance to the anterior vaginal wall is caused by increased adipose tissue, the increase in size of clitoral structures in women with higher BMIs "does not have a clear etiology."Furthermore, while arousal can increase the size of the vestibular bulbs during arousal, there are no changes in the dimension of the clitoral body (Suh et al., 2004).T A B L E 3 Anatomical landmarks used for measuring clitoral structures as described in the publications.T A B L E 4 Anatomical landmarks used for measuring clitoral distances as described in the publications.There is a general consensus that labia majora length is affected by the menopause (Agrawal et al., 2021;Cao et al., 2015), which is likely to be caused by hormonal changes (Battaglia et al., 2008).
Different modalities were utilized to measure the clitoral structures.Living patients have the advantage of allowing large scale studies, as these can be conducted in regular gynecological clinics (Agrawal et al., 2021).On the downside, examination in vivo does not allow measurement and examination of the internal clitoral structures.
Cadaveric research is valuable, but there is a limited number of cadavers available each year, and these are usually from mature patients, who may have undergone menopause.Additionally, different  et al., 2005).US studies have been proven to give important information and measurement regarding the internal anatomy of the clitoris (Buisson et al., 2008), but operator-depended factors, such as the pressure exercised by the probe, have not been taken into consideration.MRI studies are considered the gold standard, as they have been proven to be a reliable source of information, due to the visualization of internal structures and the possibility to enhance certain tissues, differentiating them because of their response to magnetic resonance (O'Connell et al., 2005).
We appreciate that there may be factors that have influenced the reported measurements in the studies.These include the different experimental modalities (MRI, US, cadavers, and living patients), the cadaveric fixative, anatomical landmarks (Tables 3 and 4), and human error.However, no significant difference was reported between the F I G U R E 2 A schematic diagram of the clitoral complex with measurements from the literature.
experimental modality and the results obtained, indicating that different techniques can be used to measure clitoral structures and determine viable ranges in individuals.To prove this, a further in-vivo study should be performed measuring clitoral structures in biological females, from various backgrounds and ages, utilizing one experimental modality, with standardized and defined anatomical landmarks.

| CONCLUSION
The results in our meta-analysis were novel in highlighting how the clitoral components can vary in size and shape, whilst remaining within the normal range.It is of utmost importance for the medical profession to advocate for the acceptance of the increased range demonstrated in these results, creating an environment of acceptance and normalization of female genitalia.As such, these findings call for an updated and expanded representation of the clitoris and its components in anatomical textbooks, to increase awareness and knowledge amongst medical professionals and the general public.These measurements confirm the presence of normal variation within clitoral structures and this will be beneficial for the care of all women, including those who have experienced FGM, in addition to those who feel insecure about their genitalia and may be considering cosmetic or gender reaffirming surgery.

(
Kös ¸üs ¸et al., 2016), recurrent postcoital cystitis(Gyftopoulos et al., 2019), and stress urinary incontinence(Ekmez & Ekmez, 2021), as these clitoral measurements were statistically different ( p < 0.05) from control groups.Kös ¸üs ¸et al. (2016) speculate that high androgen levels in women with PCOS could cause virilization, which may cause clitoral enlargement, and that hyperandrogenism is linked to longer clitoral length.Clitoral lengths were significantly greater in women with polycystic ovaries (4.00 mm), compared to those without (2.0 mm)(Kös ¸üs ¸et al., 2016).Moreover, the distance between the clitoris and urethra was significantly greater (31 mm) in patients with recurrent postcoital cystitis, compared to a control group (28 mm) (Gyftopoulos Abbreviation: N/a, data not available.
Abbreviation: N/a: Not applicable, that is, not provided in publications.
dissecting and embalming techniques might result in different final measurements of the specimen, adding bias to the process (O'Connell

1
Measurements of clitoral structures in mm.Inclusion and exclusion criteria of studies, with a brief summary of conclusions.