MicroCT analysis unveils the role of inflatable female genitalia and male tibial complex in the genital coupling in the spider genus Aysha (Anyphaenidae, Araneae).

Sperm transfer in spiders is achieved by copulatory organs on the male pedipalps (i.e., copulatory bulbs), which can be simple or a complex set of sclerites and membranes. During copulation, these sclerites can be used to anchor in corresponding structures in the female genitalia by means of hydraulic pressure. In the most diverse group of Entelegynae spiders, the retrolateral tibial apophysis clade, the female role in the coupling of genitalia is considered rather passive, as conformational changes of the female genital plate (i.e., the epigyne) during copulation are scarce. Here, we reconstruct the genital mechanics of two closely related species belonging to the Aysha prospera group (Anyphaenidae) that bear a membranous, wrinkled epigyne and male pedipalps with complex tibial structures. By using microcomputed tomography data of a cryofixed mating pair, we reveal that most of the epigyne remains greatly inflated during genital coupling, and that the male tibial structures are coupled to the epigyne by the inflation of a tibial hematodocha. We propose that a turgent female vulva is a prerequisite for the genital coupling, which could implicate a female control device, and that the structures from the male copulatory bulb have been functionally replaced by tibial structures in these species. Furthermore, we show that the conspicuous median apophysis is maintained in spite of being functionally redundant, posing a puzzling situation.

No evidence for asymmetric sperm deposition in a species with asymmetric male genitalia.

Background: Asymmetric genitalia have repeatedly evolved in animals, yet the underlying causes for their evolution are mostly unknown. The fruit fly Drosophila pachea has asymmetric external genitalia and an asymmetric phallus with a right-sided phallotrema (opening for sperm release). The complex of female and male genitalia is asymmetrically twisted during copulation and males adopt a right-sided copulation posture on top of the female. We wished to investigate if asymmetric male genital morphology and a twisted gentitalia complex may be associated with differential allocation of sperm into female sperm storage organs. Methods: We examined the internal complex of female and male reproductive organs by micro-computed tomography and synchrotron X-ray tomography before, during and after copulation. In addition, we monitored sperm aggregation states and timing of sperm transfer during copulation by premature interruption of copulation at different time-points. Results: The asymmetric phallus is located at the most caudal end of the female abdomen during copulation. The female reproductive tract, in particular the oviduct, re-arranges during copulation. It is narrow in virgin females and forms a broad vesicle at 20 min after the start of copulation. Sperm transfer into female sperm storage organs (spermathecae) was only in a minority of examined copulation trials (13/64). Also, we found that sperm was mainly transferred early, at 2-4 min after the start of copulation. We did not detect a particular pattern of sperm allocation in the left or right spermathecae. Sperm adopted a granular or filamentous aggregation state in the female uterus and spermathecae, respectively. Discussion: No evidence for asymmetric sperm deposition was identified that could be associated with asymmetric genital morphology or twisted complexing of genitalia. Male genital asymmetry may potentially have evolved as a consequence of a complex internal alignment of reproductive organs during copulation in order to optimize low sperm transfer rates.

The European Academy of Andrology (EAA) ultrasound study on healthy, fertile men: An overview on male genital tract ultrasound reference ranges.

BACKGROUND: So far, male genital tract color-Doppler ultrasound (MGT-CDUS) was not standardized. Recently, the European Academy of Andrology (EAA) published the results of a multicenter study assessing the CDUS characteristics of healthy-fertile men (HFM) to obtain normative parameters. OBJECTIVES: To report the EAA US study (i) standard operating procedures (SOPs) for assessing MGT-CDUS, (ii) main MGT-CDUS normative parameters, and (iii) compare the EAA and previously published "normal" CDUS values. METHODS: A cohort of 248 HFM (35.3 ± 5.9 years) was studied, evaluating MGT-CDUS before and after ejaculation following SOPs. RESULTS: SOPs for MGT-CDUS assessment are summarized here. All subjects underwent scrotal CDUS and 188 men underwent transrectal ultrasound before and after ejaculation. The main CDUS reference ranges and characteristics of the HFM-MGT are reported here. The mean testicular volume was ∼17 mL. The lower limit for right and left testis was 12 and 11 mL, defining testicular hypotrophy. The upper limit for epididymal head, body, tail, and vas deferens was 11.5, 5, 6, and 4.5 mm, respectively. Testicular and epididymal arterial reference ranges are reported. The EAA varicocoele classification is reported. CDUS-varicocoele was detected in ∼37% of men. Prostate mean volume was ∼25 mL, while lower and upper limits were 15 and 35 mL, defining hypotrophy and enlargement, respectively. Prostate arterial reference ranges are reported. Prostate calcifications and inhomogeneity were frequent; midline prostatic cysts were rare and small. Ejaculatory duct abnormalities were absent. The upper limit for periprostatic venous plexus was 4.5 mm. Lower and upper limits of seminal vesicles (SV) anterior-posterior diameter were 6 and 16 mm, defining hypotrophy or dilation, respectively. Seminal vesicle volume and ejection fraction reference ranges are reported. SV-US abnormalities were rare. Deferential ampullas upper limit was 6 mm. A discussion on the EAA and previously published "normal" CDUS values is reported here. CONCLUSIONS: The EAA findings will help in reproductive and general male health management.

Assessing Anatomical Changes in Male Reproductive Organs in Response to Larval Crowding Using Micro-computed Tomography Imaging.

Ecological conditions shape (adaptive) responses at the molecular, anatomical, and behavioral levels. Understanding these responses is key to predict the outcomes of intra- and inter-specific competitions and the evolutionary trajectory of populations. Recent technological advances have enabled large-scale molecular (e.g., RNAseq) and behavioral (e.g., computer vision) studies, but the study of anatomical responses to ecological conditions has lagged behind. Here, we highlight the role of X-ray micro-computed tomography (micro-CT) in generating in vivo and ex vivo 3D imaging of anatomical structures, which can enable insights into adaptive anatomical responses to ecological environments. To demonstrate the application of this method, we manipulated the larval density of Drosophila melanogaster Meigen flies and applied micro-CT to investigate the anatomical responses of the male reproductive organs to varying intraspecific competition levels during development. Our data is suggestive of two classes of anatomical responses which broadly agree with sexual selection theory: increasing larval density led to testes and ejaculatory duct to be overall larger (in volume), while the volume of accessory glands and, to a lesser extent, ejaculatory duct decreased. These two distinct classes of anatomical responses might reflect shared developmental regulation of the structures of the male reproductive system. Overall, we show that micro-CT can be an important tool to advance the study of anatomical (adaptive) responses to ecological environments.

Pápulas perladas / Pearly papules

Las pápulas perladas del pene (PPP) son lesiones benignas de aspecto blanquecino perlado que se encuentran alrededor de la corona del glande. A pesar de ser asintomáticas y benignas por naturaleza, la aparición de PPP puede causar un gran malestar psicológico tanto al paciente como a su pareja sexual, por lo que se trata de un motivo de consulta frecuente en Atención Primaria por parte de hombres jóvenes. Presentamos el caso de un joven de 22 años que consultó por hallazgo casual de lesiones indoloras en el glande. Debido a que es importante tranquilizar al paciente respecto a la naturaleza de la lesión, resulta fundamental para la médica o médico de familia conocer su localización y su aspecto típico.(AU)

Pearly penile papules (PPP) are benign, pearly-white lesions located around the crown of the glans penis. Despite being asymptomatic and benign by nature, the appearance of PPP can cause major psychological discomfort to the patient and their sexual partner. It is a common reason for primary healthcare consultation by young men. We report the case of a 22-year-old man who consulted due to the accidental finding of painless lesions on the glans penis. As it is important to reassure the patient about the nature of the injury, knowledge of the location and its typical appearance by the family doctor is essential.(AU)

Ultrasound aspects of symptomatic versus asymptomatic forms of male accessory gland inflammation.

BACKGROUND: The ultrasound (US) evaluation of the male sex accessory gland inflammation (MAGI) helps the clinicians to understand the severity of this condition, allowing them to distinguish the uncomplicated form (prostatitis) from the complicated ones (prostate-vesiculitis and prostate-vesiculitis-epididymitis), as well as the unilateral from the bilateral forms, the fibrosclerotic and the hypertrophic-congestive form. OBJECTIVE: This retrospective study aimed to evaluate the US features of MAGI patients with active symptoms compared to patients without sexual, voiding, and ejaculatory dysfunction. MATERIALS/METHODS: To achieve this aim, an analysis of the prevalence of MAGI US criteria was carried out on a very large series of over 500 patients diagnosed with MAGI classified according to the different symptom profile evaluated through a dedicated questionnaire (previously conceived and published by our group) arbitrarily named "structured interview about MAGI" (SI-MAGI) for sexual, voiding, and ejaculatory disorders reported by these patients. RESULTS: The results of this study revealed that US criteria most frequently detected in patients with severe urinary symptoms were the presence of areas of high echogenicity (almost exclusively in the periurethral prostatic zone) together with the presence of single or multiple areas of acinar ectasia of the prostate. The presence of seminal vesicles with polycyclic areas within the glandular lumen separated by hyperechoic septa represented US criterion most frequently detected in patients with severe spontaneous or post-ejaculate pain. Finally, US criterion most frequently detected in patients with severe sexual dysfunction was the dilation of the periprostatic venous plexus, suggesting the hypothesis of a possible alternative therapeutic approach. CONCLUSION: The data of the present study suggest that symptoms may associate with US signs in patients with MAGI. Also, specific US signs may associate with specific symptoms. Further studies are needed to understand whether patients with specific US signs may in turn benefit from a personalized therapeutic choice.

Ultrasound evaluation of patients with male accessory gland inflammation: a pictorial review.

Male accessory gland infection/inflammation (MAGI) is a major cause of male infertility. The importance of ultrasound evaluation in these patients is highly controversial, although evidence of its relevance has increased in recent years. Ultrasound criteria are an important element for confirming the clinical diagnosis. Furthermore, they help to localize the anatomical site or sites of the inflammatory process and in assessing its extension which, in turn, have different consequences on the seminological and symptomatic aspects. This article summarizes the clinical interpretations related to ultrasound aspects in patients with MAGI and the possible effects on the seminological, microbiological, endocrinologic, urological, sexological, and internist aspects.

Surgical treatment and outcome of complete unilateral urinary tract duplication in a dog.

OBJECTIVE: To report the surgical technique and outcome for correction of complete unilateral duplication of the left urinary tract in a dog. ANIMALS: One 7-month-old entire male Jack Russell terrier. STUDY DESIGN: Case report METHODS: A dog was referred for investigation because of urinary incontinence (UI), preputial irritation (pruritus), diphallia, and cryptorchidism. Computed tomography including urethrographic studies revealed a left duplex kidney, double ectopic left ureters, and a duplex urinary bladder comprising two halves separated by a median septum, each of which emptied into a separate urethra which coursed through separate penises. The left testis was abdominally retained. The right upper urinary tract was considered normal, and the right testis was within the scrotum. Left sided ureteronephrectomy was performed, the median bladder septum was ablated, and the left urethra was ligated. The left penis was partially amputated, and the dog was castrated. RESULTS: Urinary incontinence was improved but persisted after surgery. After repeat imaging, revision surgery was performed 3 months later in which the distal stumps of the (left) ectopic ureters were found to be filling with urine from the right urethra. Urinary incontinence resolved after resection of these ureteric stumps from the prostate and complete transection of the left urethra. CONCLUSION: Extensive surgery with resection and correction of urinary tract duplication was successful in resolving UI in this case. Urogenital duplication should be considered a rare cause of UI. The presence of external congenital deformity (eg, diphallia) should alert clinicians to the possibility of significant concurrent internal abnormalities.

First description of male genital sclerites and associated musculature for two members of Coniopterygidae (Insecta: Neuropterida: Neuroptera) based on X-ray microCT imaging.

Coniopterygidae are the dwarfs among the Neuroptera. Despite their miniaturisation, the males are equipped with genital sclerites that are excessively heterogeneous. They function in copulation and sperm transfer and have been widely utilized for species identification, as well being considered of high phylogenetic relevance. The present study is the first to describe the musculature associated with the genital sclerites of two species of Coniopterygidae, Helicoconis lutea (Wallengren, 1871) (Aleuropteryginae), and Coniopteryx pygmaea (Enderlein, 1906) (Coniopteryginae) based on X-ray microCT imaging. We found six pairs of muscles associated with the genital sclerites in H. lutea and seven in C. pygmaea. The images depict other internal organs of the posterior abdominal segments, such as gonads and alimentary canal. In both investigated species, the internal sclerites support the ductus ejaculatorius, which - surprisingly - turned out to be a landmark for the identification of closely adjacent internal sclerites and associated musculature. The interpretation of these sclerites as gonocoxites and gonapophyses of the tenth segment (traditionally denoted as parameres and penis) could be corroborated. Thus it is no longer tenable to assert that possession of a "penis" is exclusive to Coniopterygidae, since this sclerite is part of the ground pattern in Neuroptera. Interactions of genital sclerites and corresponding musculature during copulation are discussed.

The European Academy of Andrology (EAA) ultrasound study on healthy, fertile men: clinical, seminal and biochemical characteristics.

BACKGROUND: Infertility affects 7%-12% of men, and its etiology is unknown in half of cases. To fill this gap, use of the male genital tract color-Doppler ultrasound (MGT-CDUS) has progressively expanded. However, MGT-CDUS still suffers from lack of standardization. Hence, the European Academy of Andrology (EAA) has promoted a multicenter study ("EAA ultrasound study") to assess MGT-CDUS characteristics of healthy, fertile men to obtain normative parameters. OBJECTIVES: To report (a) the development and methodology of the "EAA ultrasound study," (b) the clinical characteristics of the cohort of healthy, fertile men, and (c) the correlations of both fertility history and seminal features with clinical parameters. METHODS: A cohort of 248 healthy, fertile men (35.3 ± 5.9 years) was studied. All subjects were asked to undergo, within the same day, clinical, biochemical, and seminal evaluation and MGT-CDUS before and after ejaculation. RESULTS: The clinical, seminal, and biochemical characteristics of the cohort have been reported here. The seminal characteristics were consistent with those reported by the WHO (2010) for the 50th and 5th centiles for fertile men. Normozoospermia was observed in 79.6% of men, while normal sperm vitality was present in almost the entire sample. Time to pregnancy (TTP) was 3.0[1.0-6.0] months. TTP was negatively correlated with sperm vitality (Adj.r =-.310, P = .011), but not with other seminal, clinical, or biochemical parameters. Sperm vitality and normal morphology were positively associated with fT3 and fT4 levels, respectively (Adj.r = .244, P < .05 and Adj.r = .232, P = .002). Sperm concentration and total count were negatively associated with FSH levels and positively, along with progressive motility, with mean testis volume (TV). Mean TV was 20.4 ± 4.0 mL, and the lower reference values for right and left testes were 15.0 and 14.0 mL. Mean TV was negatively associated with gonadotropin levels and pulse pressure. Varicocoele was found in 33% of men. CONCLUSIONS: The cohort studied confirms the WHO data for all semen parameters and represents a reference with which to assess MGT-CDUS normative parameters.

MRI in the evaluation of the azoospermic male.

PURPOSE We aimed to show the usefulness of magnetic resonance imaging (MRI) in the evaluation of infertile men and its ability to distinguish obstructive from nonobstructive azoospermia. METHODS Between April 2015 and February 2018, 45 azoospermic men underwent scrotal MRI. We evaluated the images with an emphasis on signal characteristics of the testis and morphologic changes typical for obstruction. Testicular volume (TV), apparent diffusion coefficient (ADC) value, T1 and T2 signal ratios (testis/muscle) were measured for every testis. On the basis of histologic results, patients were divided into two groups: obstructive azoospermia (OA) and nonobstructive azoospermia (NOA). RESULTS Testes of patients in the OA group had significantly lower ADC values (mean 0.876±101 ×10-3 mm2/s) than in the NOA group (mean, 1.114±147 ×10-3 mm2/s). TV was significantly higher in patients with OA (median, 17.61 mL; range, 11.1-38.4 mL) than in those with NOA (median, 10.5 mL; range, 5.2-22.2 mL). ROC analysis showed that both TV and ADC values were highly predictive for distinguishing between OA and NOA patients, with an area under the ROC curve of 0.82 and 0.92 respectively. A cutoff value of ≥12.4 mL could distinguish obstructive from nonobstructive azoospermia with a sensitivity of 92% and specificity of 63%, whereas for ADC measurements a cutoff value of ≥0.952 ×10-3 mm2/s exhibited a sensitivity of 81% and specificity of 90% There was no statistically significant difference in T1 and T2 signal ratios between both groups. Abnormalities typical for obstruction of the male reproductive tract (e.g., dilatation of ejaculatory ducts, prostatic or seminal vesicle cysts) were found in 78% of patients (14/18) in the obstructive group. CONCLUSION Scrotal MRI is a very effective tool for the evaluation of azoospermic men and may provide important information facilitating interventional treatment of infertility.

Imaging of the male reproductive tract: Not so easy as it looks like.

Diagnostic imaging is one of the most important tools in the breeding soundness evaluation of dogs and cats with reproduction problems. In recent years several imaging techniques have been developed, trying to aid the diagnosis and to differentiate between abnormal findings. This review presents the current knowledge on the imaging of normal and abnormal testes, spermatic cord, excurrent duct system, scrotum, accessory sex glands, penis and muscles for protrusion, erection and ejaculation of the dog and of cat. It also highlights the weak points and disadvantages of each imaging technique.

Transformation of the female genitalia in congenital adrenal hyperplasia: MRI study.

PURPOSE: In this report, we aim to define the different degrees of structural abnormality affecting the female genitalia in cases of CAH by using the multiplanar capabilities and high soft tissue resolution of MRI. PATIENTS AND METHODS: The study included cases of CAH who were referred to our pediatric surgical facility for genital reconstruction during the period 2016 through 2019. We studied the pelvic MRI anatomy in cases of CAH while referring to clinical and operative findings. To set up a grading scale for the degree of virilization in cases of CAH, we included another two control groups of normal boys and girls representing the two ends of the spectrum. RESULTS: The study included 23 cases of CAH who underwent preoperative pelvic MRI examination. All cases had normal chromosomal analysis (46 XX). Their age ranged from 1 to 156 months at time of MRI examination (mean 42.4; median 25). The level of the lower end of the vagina was identified in midsagittal T2WI and confirmed in sequential axial cuts. Based on the level of the lower end of the vagina in relation to the pubic symphysis, we classified cases of CAH into either low or high types. Moreover, we could observe a correlation between the degree of vaginal descent and structural transformation of erectile tissue between both genders. CONCLUSION: MRI can have an important role in the evaluation of cases of CAH by displaying the severity of internal anomaly which is crucial for proper preoperative counseling. TYPE OF STUDY: Case control study. LEVEL OF EVIDENCE: Level III.

Advanced ultrasound techniques in small animal reproduction imaging.

Ultrasonography is the imaging technology of choice for the evaluation of the reproduction system and of pregnancy in both humans and animals. Over the past 10 years, there have been significant technological improvements of the equipment, while new technologies have been developed. Doppler, contrast-enhanced ultrasonography, elastography, and 3D/4D ultrasonography are advanced ultrasound techniques that have been designed as methods to increase the diagnostic sensitivity of two-dimensional (b-mode) ultrasound, and not as stand-alone tests. The basic physics as well as the advantages and limitations of these advanced ultrasound methods are briefly described. In the reproductive diagnostics of small animals, these techniques have gained an increased popularity as proved by the increased publication of several reports that are also briefly summarized in this review. Clinical applicability is to date limited because of a lack of research on the diagnostic value in concrete situations. Future research projects should focus also on standardization of the used techniques, on determination of thresholds to discriminate between healthy or diseases or fertile versus infertile and on the predictive value of advanced ultrasound findings. Continuing development and optimization of different ultrasound techniques as well as the increase of related scientific interest and worldwide research promises that the clinical interest on the use of advanced ultrasound techniques will increase in future.

Ultrasonographic characteristics of the testes, epididymis and accessory sex glands and arterial spectral indices in peri- and post-pubertal Nelore and Caracu bulls.

Ultrasonography can provide information about the integrity of organs; however, rarely is applied to the reproductive organ evaluation of bulls. The objective of the present study was to characterize and compare values for variables and ultrasonographic characteristics of the testes, epididymis and accessory sex glands, as well as spectral Doppler indices of the testicular and internal iliac arteries, between peri- and post-pubertal Nelore and Caracu bulls. Nelore (n = 203) and Caracu (n = 79) bulls were assigned by age class: peri-pubertal (12-15 months) and post-pubertal (> 22 months). Data were analyzed using SAS's PROC MIXED procedure (P < 0.05). The biometric variables of the testes and cauda epididymis differed between peri- and post-pubertal Nelore and Caracu bulls. There was a difference between breeds for the vesicular glands, ampulla of vas deferens, disseminate portion of the prostate, and craniocaudal dimension of the bulbourethral glands. Echogenicity of the testicular parenchyma differed between breeds and age classes. The pulsatility and resistive indices of the testicular arteries differed between Nelore and Caracu bulls. The biometric and ultrasonographic characteristics of the testes, epididymis and accessory sex glands, as well as of the arterial indices in bulls are affected by genetic group and age class, and when assessed there is useful information regarding the progression of sexual maturation.

Examination of jackass (Equus asinus) accessory sex glands by B-mode ultrasound and of testicular artery blood flow by colour pulsed-wave Doppler ultrasound: Correlations with semen production.

The accessory sex glands play a major role in the production of seminal plasma, and testicular artery blood flow seems to strongly influence testicular function. However, very little ultrasound imaging of these organs has been undertaken in donkeys. The present work reports the results of such examinations in five jackasses along the year. The accessory glands were inspected by B-mode ultrasound while the testicular artery blood flow was assessed by colour pulsed-wave Doppler ultrasound. The testicular artery was examined at pampiniform plexus (PPT), supratesticular area (ST) and capsular artery (CA). Values were recorded for the total arterial blood flow (TABF), peak systolic velocity (PSV), end-diastolic velocity (EDV), resistive index (RI), pulsatility index (PI) and time average maximum velocity (TAMV). Semen was obtained and assessed for sperm concentration, viability, abnormalities and motility using a CASA system. The bulbourethral glands, prostate and ductus deferens ampullae were relatively larger than in the stallion. Bulbourethral glands and ampullae sizes were inversely correlated with sperm motility. An reduction in blood flow between the level the PPP and the CA was observed, helping to reduce testis temperature and oxygen pressure. Blood flow at the CA showed the strongest correlation with semen production. PI and RI were positively correlated with the CASA motility variable STR (p = .02, p = .06) and sperm viability (p = .01), while sperm concentration (p = .05) correlated inversely with PSV, EDV, TAMV and TABF. EDV also correlated negatively with the CASA variables VSL, LIN, STR and VAP (p ≤ .05). PI and RI were also negatively correlated with testis length (p = .0093, p = -.0438).

MRI of the Male Pelvic Floor.

The pelvic floor is a complex structure that supports the pelvic organs and provides resting tone and voluntary control of the urethral and anal sphincters. Dysfunction of or injury to the pelvic floor can lead to gastrointestinal, urinary, and sexual dysfunction. The prevalence of pelvic floor disorders is much lower in men than in women, and because of this, the majority of the published literature pertaining to MRI of the pelvic floor is oriented toward evaluation of the female pelvic floor. The male pelvic floor has sex-specific differences in anatomy and pathophysiologic disorders. Despite these differences, static and dynamic MRI features of these disorders, specifically gastrointestinal disorders, are similar in both sexes. MRI and MR defecography can be used to evaluate anorectal disorders related to the pelvic floor. MRI can also be used after prostatectomy to help predict the risk of postsurgical incontinence, to evaluate postsurgical function by using dynamic voiding MR cystourethrography, and subsequently, to assess causes of incontinence treatment failure. Increased tone of the pelvic musculature in men secondary to chronic pain can lead to sexual dysfunction. This article reviews normal male pelvic floor anatomy and how it differs from the female pelvis; MRI techniques for imaging the male pelvis; and urinary, gastrointestinal, and sexual conditions related to abnormalities of pelvic floor structures in men.Online supplemental material is available for this article.©RSNA, 2019.

Comparative effectiveness of imaging modalities for preoperative assessment of anorectal malformation in the pediatric population.

OBJECTIVE: The aim of this study was to compare the accuracy of MRI, colostography/fistulography, and X-ray imaging modalities for preoperative diagnosis of anorectal malformations (ARMs) in pediatric patients. METHODS: This retrospective analysis included a total of 84 pediatric patients with ARMs. Preoperative imaging findings were assessed by 2 radiologists and compared to surgical findings. RESULTS: MRI identified anomalies of the spine in 25 of 84 patients (29.8%), anomalies of the genital system in 7 of 84 patients (8.3%), anomalies of the urinary system in 22 of 84 patients (26.2%), and underdeveloped sphincter muscle complex in 34 of 84 patients (40.5%). In the 44 subjects receiving both MRI and X-ray, MRI was more sensitive in detecting anomalies of spine (18/44 vs. 8/44; P = 0.002), and both correctly identified the distal end of the rectum in 77.3% (34/44) of the cases. In the 24 subjects receiving both MRI and colostography/fistulography, MRI was more accurate in identifying Pena's classification (22/24 vs. 15/24; P = 0.039). Distal end of the rectum was correctly identified in 75.0% (18/24) and 58.3% (14/24) of the cases (P = 0.125). CONCLUSIONS: MRI could clearly reveal fistula anatomy and associated anomalies of ARMs and should be routinely used for preoperative evaluation of ARMs. TYPE OF STUDY: Study of diagnostic test. LEVEL OF EVIDENCE: Level II.