Diphallia: literature review and proposed surgical classification system.

BACKGROUND: Diphallia occurs once in 5-6 million births, with no two patients presenting with the same anatomical variation. Here we discuss a review of diphallia case reports, as well as present a new surgical classification system based on the soft tissue composition of the two phalluses, the anatomy of the urethra present within the most normal phallus and the bladder configuration.
METHODS: Eighty-seven diphallia case reports were collected and analysed, excluding those presented in animals and articles that were non-English, with the results compiled to provide an in-depth reference of the specific anatomy found in diphallia patients and the associated abnormalities.
RESULTS: Our proposed classification system was then applied to each patient and the most common configuration base on our classification system presented, along with commonly seen associated anomalies.
CONCLUSION: The reviewed cases represent a subset of the most unique diphallia patients; thus, several cases may be left unreported. Future reports can then be categorized, aiding as a reference, and potentially building on the classification, should the patient not fit into a specific group, leading to an expansion of the classification system.

Introduction

Diphallia or duplicate penis is an extremely rare embryological anomaly with a wide range of anatomic appearances ranging from small accessory tissues to complete duplications of the phallus, glans, urethras, and bladders, as well as an extensive list of associated abnormalities. The phalluses are usually unequal in size and positionally, can lie side by side, stacked on top of the other in the sagittal plane, or with little association to each other. This paper assesses patients within the literature to summarize diphallia variants, as well as build on the existing classification of diphallia to include a more specific categorization of the phallus soft tissue, the urethral anatomy, and the bladder configurations to create a surgical classification system.

Background

Diphallia is estimated to occur in 1 out of 5–6 million births, with around 100 patients being reported within the literature. The oldest published instance of diphallia was reported in 1609 by Johannes Jacob Wecker; ‘in Bologna during public dissections the cadaver of a man who had a double penis’, however the earliest pictorial record of diphallia dates back to 1862 in the Lupanar (Latin for brothel) in Pompeii, in which a painting on the wall depicted a completely diphallic man (Fig. 1).

Fig. 1

Pompeian Lupanar showing Priapus with a double phallus. Image from Galassi et al. accessed January third, 2021.

Embryology

Previously, Cecil submitted four embryological explanations for diphallia. The first includes the bladder, the prostatic urethra, and the penis being derived from a bilateral anlagen, which normally gives a single end product by fusion, meaning diphallia is a product of an incompletely fused anlagen. Next, diphallia may be an atavism, as snakes and lizards normally possess double penis or possibly represents a teratoid structure. Cecil also suggested that it may be a minor degree of duplication, much like supernumery digits, of the individual.

Hollowell et al. however affirm that these explanations are incomplete and suggests that that embryologically, the diphallia anomaly occurs in the fetus between the third and seventh week of gestation, in which an insult hampers normal functioning of the caudal cell mass of the fetal mesoderm at the time of the urogenital sinus separating from the genital tubercle into the penis. Complete diphallia may then stem from longitudinal duplication of the infraumbilical cloacal, with the subsequent mesodermal migration leading to the formation of two separate and complete sets of genital tubercles, genital folds, and genital swellings. ,

Treatment

Treatment of diphallia is typically approached on an individual basis, as no two patients within the literature are the same. The associated anomalies are a major cause of mortality in diphallia patients, and treatment is usually done in a stepwise manor, with corrections aimed at the anomalies, excision of the more abnormal phallus, excision of the urethra in instances of duplicate urethra, and excision or correction of either duplicate bladders or bladder exstrophy. It may also be difficult to discern which phallus to excise, thus with the proposed classification system, a label can be used to drive the treatment approach, allowing a decision to be made based on the more normal phallus, with the more normal urethral pathway and normal bladder configuration.

Methods

For this paper, a review of published diphallia patients was conducted by one reviewer. Google scholar and PubMed were analysed using key phrases diphallia, double penis, psuedophallia and bifid glans giving a total of 518 articles. Articles were screened based on title and abstract, making sure to include relevant case reports in humans, excluding articles in animals, duplicate articles and non‐English articles. Following the screening of relevant inclusion and exclusion criteria, a total of 76 articles were analysed, which totalled 87 relevant diphallia patients found within the literature. Each patient was then analysed and presented in Table 1. From each patient, the unique anatomical variant for each was then examined. This included first addressing the age of the patient at the time of presentation, followed by categorizing the soft tissue structure of each phallus, the anatomy of the scrotum and testicles, as well as if there was a penoscrotal transposition. The reports were also analysed for their urethral anatomy, and if there was a hypospadias or epispadias present, as well as the bladder configuration. Lastly, the associated abnormalities were summarized based on the reviewers best clinical judgement. Each patient was then classified based on the proposed classification system below.

Table 1

Literature review of diphallia, associated anatomy and classifications

Author, Year	Age at definitive treatment	Number of corpora cavernosa	Hypospadias/Epispadias	Scrotum	Testes	Penoscrotal Transposition	Urethra	Bladder	Other anomalies	Classification
Acimi 5	3 yrs.	Phallus 1: 2	Hypospadias	Normal	Descended bilaterally	No	Duplicate	Single	Imperforate anus	1Aα
		Phallus 2: 2
Acimi 6	4 mo.	Phallus 1: 2Phallus	Hypospadias	Bifid	Descended bilaterally	No	Duplicate, one functional	Single	Unilateral Kidney agenesis	1Bα
									Lumbosacral meningocele
		2: 2
									Ureterovesical duplication
Adair and Lewis 7	1 yr.	Phallus 1: 2	N/A	Normal	Descended unilaterally	No	Single	Single	Umbilical hernia	7Aα
									Unilateral Kidney agenesis
		Duplicate Glans
AI‐Herbish and AI‐Samarrai 8	1 mo.	Phallus 1: 2	Hypospadias	Bifid	Descended bilaterally	No	Duplicate with bifurcation of one urethra	Single	Unilateral Kidney agenesis	1Αα
									Musculoskeletal anomalies
		Phallus 2: 2							Hemivertebra and absent first rib
Aihole, 2015 9	1 yr.	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Duplicate	Single	Pre‐axial polydactyly	7Βα
									Solitary Kidney
		Duplicate Glans							Atrial septal defect
Akgül et al. 10	4 yrs.	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Duplicate	Duplicate	Anal atresia	1Αβ
									Duplicate rectum, colon, cecum, appendix and terminal ileum
		Phallus 2: 2
									Rectovesical fistula
Aleem 11	2 mo.	Phallus 1: 1	Epispadias	Bifid	Descended bilaterally	No	Single	Single	Wide diastasis of the pubic bones and partial sacral agenesis.	1Dα
		Phallus 2: 1
Ali 12	19 yrs.	Phallus 1: 1	N/A	Normal	Descended bilaterally	No	Single	Single	N/A	2Aα
		Phallus 2: 2
Arya et al. 13	31 yrs.	Phallus 1: 2	Epispadias	Bifid	Descended bilaterally	No	Duplicate, no urethral plates	Exstrophy	N/A	1Dγ
		Phallus 2: 2
	3 mo.	Phallus 1: 2	N/A	Bifid	Descended bilaterally	No	Duplicate	Single	N/A	1Aα
		Phallus 2: 2
Bakheet and Refaei 14	Neonate	Phallus 1: 2	N/A	Duplicate	Duplicate, descended bilaterally	No	Duplicate	Single	Duplicate colon, rectum, anus	1Aα
		Phallus 2: 2
Bhat et al. 15	1 yr.	Phallus 1: 2	Hypospadias	Bifid	Descended bilaterally	No	Duplicate, opening normally and into lateral wall of bladder	Single	N/A	1Cα
		Phallus 2: 2
Blanco 16	18 yrs.	Phallus 1: 2	Hypospadias	Normal	Descended bilaterally	No	Duplicate	Single	N/A	1Aα
		Phallus 2: 2
Cernach et al. 17	11 mo.	Phallus 1: 2	N/A	Bifid	Descended bilaterally	No	Duplicate	Duplicate	Duplicate anus, one imperforatehemivertebrae and diastasis of pubic symphysis	1Aβ
		Phallus 2: 2
Chadha et al. 18	Neonate	Phallus 1: 2	N/A	Bifid	Descended into lateral compartments	No	Bifurcation at prostatic urethra	Single	N/A	1Aα
		Phallus 2: 2
de Oliveira et al. 19	5 yrs.	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Duplicate, unilateral stenosis	Single	N/A	1Bα
		Phallus 2: 2
Deshpande 20	2 yrs.	Phallus 1: 2	N/A	Bifid	Descended unilaterally	No	Duplicate	Single	N/A	1Aα
		Phallus 2: 2
Dewan et al. 21	7 yrs.	Phallus 1: 2	N/A	Bifid	Descended unilaterally	No	Duplicate, opening normally and into lateral wall of bladder	Single	Imperforate anus	1Aα
		Phallus 2: 2
Djordjevic and Perovic 22	15 mo.	Phallus 1: 2	Hypospadias	Bifid	Descended bilaterally	No	Duplicate	Duplicate	Symphyseal diastasis	1Aβ
		Phallus 2: 2
Dunn et al. 23	3 yrs.	Phallus 1: 2	N/A	Bifid	Descended bilaterally	No	Duplicate	Duplicate	N/A	1Aβ
		Phallus 2: 2
Dutta et al. 24	Neonate	Phallus 1: 2	N/A	Bifid	Descended bilaterally	No	Duplicate, pneumaturia	Duplicate	Pelvic kidney	1Aβ
		Phallus 2: 2							Anorectal atresia
Elsawy et al. 25	1 mo.	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Duplicate, one hypoplastic	Single	Inguinal hernia	4Aα
									Absent right thumb
		Phallus 2: 2
Frollo et al. 26	84 yrs.	Phallus 1: 2	Hypospadias	Normal	Descended bilaterally	No	No urethra in either phallus	Single	N/A	1Cα
		Phallus 2: 2
Gavali et al. 27	5 yrs.	Phallus 1: 2	Hypospadias	Normal	Descended bilaterally	No	Single	Single	Single Kidney agenesis	7Bα
		Duplicate Glans
Ghafoori et al. 28	5 yrs.	Phallus 1: 1	N/A	Normal	Descended bilaterally	No	Duplicate	Single	N/A	3Aα
		Phallus 2: 1
Goad et al. 29	13 yrs.	Phallus 1: 2	Hypospadias	Normal	Descended bilaterally	No	Single	Single	N/A	1Aα
		Phallus 2: 2
Gupta and Virdi 30	10 yrs.	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Duplicate	Single	N/A	1Aα
		Phallus 2: 2
Gyftopoulos et al. 31	Neonate	Phallus 1: 2	Hypospadias	Bifid	Undescended bilaterally	No	Duplicate	Duplicate	Horseshoe kidney Partial duplication of distal colonVentricular septum defect	1Aβ
		Phallus 2: 2							Hypoplasia of the right leg due to agenesis of the fibula
									Cloacal opening at the perineum
	Neonate	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Duplicate, one with blind ending	Duplicate	Urethrorectal Y‐fistula	3Aβ
		Phallus 2: 2
Hanine et al. 32	8 yrs.	Phallus 1: 1	N/A	Normal	Descended bilaterally	No	Single	Single	N/A	2Aα
		Phallus 2: 1
Hollowell et al. 13	5 mo.	Phallus 1: 2	Hypospadias	Bifid	Descended bilaterally	No	Duplicate	Duplicate	Imperforate anus Perineal fistula	1Aα
		Phallus 2: 2							Meningocele
	50 yrs.	Phallus 1: 2	Hypospadias	Bifid	Descended into lateral compartments	No	Duplicate	Single	Prolapse of the rectum	1Cα
									Absence of perineal
									Midline infraumbilical musculature
									Bilateral inguinal hernias
		Phallus 2: 2
Jesus et al. 33	20 yrs.	Phallus 1: 2	Hypospadias	Normal	Descended bilaterally	No	Duplicate	Single	N/A	7Cα
		Duplicate Glans
Johnson et al. 34	17 yrs.	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Duplicate	Single	N/A	7Aα
		Duplicate Glans
Karagöz et al. 35	15 yrs.	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Single	Single	N/A	7Aα
		Duplicate Glans
Kardasevic et al. 36	Neonate	Phallus 1: 2	Hypospadias	#NAME?	Descended bilaterally	No	Duplicate	Duplicate	Atrial and ventricular septal defect	1Aβ
									Duplicate right ureter
		Phallus 2: 2
									Triple spleen
									Duplicate right kidney
Karna and Kapur 37	Neonate	Phallus 1: 2	N/A	Bifid	Undescended bilaterally	No	Duplicate	Single	Omphalocele	1Aα
									Tracheoesophageal fistula
									Imperforate anus
									Single Kidney agenesis
									Duplicate distal ileum, cecum, appendix and colon
		Phallus 2: 2
									Musculoskeletal anomalies
Kaufman et al. 38	15 yrs.	Phallus 1: 2	Hypospadias	Normal	Descended bilaterally	No	Duplicate, with third perineal urethra	Single	Imperforate anus	1Aα
		Phallus 2: 2
Keckler 39	Neonate	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Duplicate	Single	N/A	1Aα
		Phallus 2: 2
Kendrick et al. 40	3 mo.	Phallus 1: 2	N/A	Normal	Descended bilaterally	Partial	Duplicate, opening normally and into lateral wall of bladder	Single	N/A	2Bα
		Phallus 2: 1
Khorramirouz et al. 41	6 yrs.	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Duplicate, unilateral stenosis	Duplicate	Horseshoe Kidney	7Bβ
		Duplicate Glans
Kırlı et al. 42	Neonate	Phallus 1: 2	Epispadias	Normal	Descended bilaterally	No	Duplicate	Exstrophy	Inguinal hernia	1Dγ
		Phallus 2: 2
Kundal et al. 43	3 yrs.	Phallus 1: 2	Epispadias	Normal	Descended bilaterally	No	Duplicate	Single	N/A	1Aα
		Phallus 2: 2
Landy et al. 44	Neonate	Phallus 1: 2	N/A	Normal with accessory scrotum	Descended bilaterally	No	Duplicate	Single	Imperforate anus	1Aα
		Phallus 2: 2
Larsen 45	14 yrs.	Phallus 1: 1	N/A	Normal	Descended unilaterally	Partial	Duplicate	Single	Atrophic leg	3Aα
		Phallus 2: 1
Leite et al. 46	2 yrs.	Phallus 1: 1	N/A	Normal	Descended bilaterally	No	Duplicate, one with blind ending	Single	Short oesophagus	3Aα
		Phallus 2: 1
Maher et al. 47	Neonate	Phallus 1: 2	N/A	Duplicate	Descended bilaterally	No	Duplicate	Duplicate	Separated natal clefts with no anal orifice	1Aβ
									Hydronephrotic left kidney
									Duplicated colon
									Caudal duplication syndrome
		Phallus 2: 2
Mandal and Sahi 48	Neonate	Phallus 1: 2	N/A	Duplicate	Duplicate, descended bilaterally	No	Duplicate	Single	N/A	1Aα
		Phallus 2: 2
Marti‐Bonmati et al. 49	Neonate	Phallus 1: 2	Hypospadias	Ectopic scrotal tissue	Descended unilaterally	No	Duplicate, one with blind ending	Exstrophy	Imperforate anus	1Aγ
		Phallus 2: 2
Maruyama et al. 50	Neonate	Phallus 1: 1	Hypospadias	Bifid	Descended unilaterally	No	Duplicate	Single	Tracheoesophageal fistula with oesophageal atresia	3Cα
									Imperforate anus Bilateral radial limb defects
									Cleft palate
		Phallus 2: 1							Patent ductus arteriosus, Single umbilical artery
									Right megaureterLeft multicystic dysplastic kidney
Matsumoto et al. 51	12 mo.	Phallus 1: 1	Hypospadias	Bifid	Descended bilaterally	Complete	Duplicate	Single	Atrial septal defect	2Aα
		Phallus 2: 2
Melekos et al. 52	8 yrs.	Phallus 1: 1	Hypospadias	Normal	Descended bilaterally	No	Duplicate	Single	Horseshoe Kidney	6Cα
		Phallus 2: 1
Mingazzini 53	36 yrs.	Phallus 1: 1	N/A	Normal	Descended bilaterally	No	Duplicate, unilateral stenosis	Single	Umbilical hernia	3Aα
		Phallus 2: 1
Mirshemirani et al. 54	Neonate	Phallus 1: 2	Hypospadias	Bifid	Descended bilaterally	No	Duplicate	Duplicate	Imperforate anus	1Cβ
		Phallus 2: 2							Duplicate colon
	14 yrs.	Phallus 1: 1	Hypospadias	Bifid	Descended bilaterally	No	Duplicate	Single	Imperforate anus	3Cα
									Duplicate sigmoid colon
		Phallus 2: 1
	4 yrs.	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Duplicate	Duplicate	Right inguinal hernia	1Aβ
		Phallus 2: 2
	12 yrs.	Phallus 1: 2	Epispadias	Bifid	Descended bilaterally	No	Duplicate	Exstrophy	Single kidney	4Dγ
									Hemi‐Vertebra
		Phallus 2: 2
	1 yr.	Phallus 1: 2	N/A	Bifid	Descended bilaterally	No	Duplicate	Duplicate	N/A	1Aβ
		Phallus 2: 2
	9 mo.	Phallus 1: 2	N/A	Bifid	Descended bilaterally	No	Duplicate	Single	Imperforate anus	1Aα
		Phallus 2: 2
Mukunda et al. 55	Neonate	Phallus 1: 2	N/A	Bifid	Descended bilaterally	No	Bifurcation at prostatic urethra	Single	Meckel's diverticulum	1Eα
		Phallus 2: 2
Mutlu et al. 56	9 yrs.	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Bifurcation at prostatic urethra	Single	Rotational anomaly of right kidney	2Eα
		Phallus 2: 1
									Left ureter duplication
Nunez et al. 57	Neonate	Phallus 1: 2	Hypospadias	Normal	Descended bilaterally	No	Duplicate	Single	Anorectal malformation	7Cα
		Duplicate Glans
Peris 58	17 yrs.	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Single	Single	N/A	2Aα
		Phallus 2: 0
Priyadarshi 59	1 yr.	Phallus 1: 1	Epispadias	Bifid	Descended bilaterally	No	Duplicate	Single	Ectopic bowel segment	3Dα
		Phallus 2: 1
Rajarajan 60	23 yrs.	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Duplicate	Single	Anorectal anomalies and colonic duplication	4Cα
		Phallus 2: 2
Rao and Chandrasekharam 61	3 mo.	Phallus 1: 2	Epispadias	Normal	Descended bilaterally	No	Duplicate, one with blind ending	Single	N/A	7Dα
		Duplicate Glans
Remzi 62	14 yrs.	Phallus 1: 2	Hypospadias	Duplicate	Duplicate, descended bilaterally	No	Duplicate	Exstrophy	hemivertebrae, lumbosacral scoliosis	1Cγ
		Phallus 2: 2
Rock and Gearheart 63	1 yr.	Phallus 1: 2	N/A	Bifid	Descended bilaterally	No	Duplicate	Duplicate	Hypoplastic kidney	1Aβ
									Widely separate pubic diastasis
		Phallus 2: 2
									Sacral insufficiency
Rodriguez 64	Neonate	Phallus 1: 2	HypospadiasEpispadias	Duplicate	Duplicate, descended bilaterally	No	Duplicate	Single (bilobated)	Duplicate umbilical cord	1Cα
		Phallus 2: 2
Rossete‐Cervantes and Villegas‐Muñoz 65	83 yrs.	Phallus 1: 2	N/A	Normal	Duplicate, descended bilaterally	No	Duplicate	Single	N/A	1Aα
		Phallus 2: 2
Savir et al. 66	31 yrs.	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Duplicate	Single	N/A	4Aα
		Phallus 2: 2
Sharma et al. 67	Neonate	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Duplicate, one with blind ending	Single	Duplicate colon	1Aα
		Phallus 2: 2
Sharma et al. 68	Neonate	Phallus 1: 2Phallus	N/A	Normal	Descended bilaterally	No	Duplicate, one with blind ending	Single	N/A	1Aα
		2: 2
Sina et al. 69	2 mo.	Phallus 1: 2	N/A	Normal with accessory scrotum	Descended bilaterally	No	Duplicate	Single	N/A	2Aα
		Phallus 2: 1
Smith and Sherer 70	18 yrs.	Phallus 1: 2	N/A	Normal	Descended unilaterally	No	Duplicate	Exstrophy	N/A	7Aγ
		Duplicate Glans
Solomon et al. 71	Neonate	Phallus 1: 2	N/A	Normal	Descended unilaterally	No	Duplicate	Single	Supernumerary kidney	6Aα
		Phallus 2: 2
Sotiropoulos et al. 72	12 yrs.	Phallus 1: 2	Hypospadias	Bifid	Descended bilaterally	No	Duplicate, both blind ending	Exstrophy	Hypoplastic kidney	1Aγ
									Omphalocele
		Phallus 2: 2							Bilateral inguinal hernia
									Imperforate anus
									Colovesical fistula
	14 yrs.	Phallus 1: 2	Epispadias	Bifid	Descended bilaterally	No	Duplicate	Exstrophy	Agenesis left upper extremity, and a web deformity of the left popliteal region. Rectoperineal fistula	7Cγ
		Duplicate Glans
	Neonate	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Duplicate	Exstrophy	Vesicoureteral reflux Aplastic kidney	2Dγ
		Phallus 2: 2
	17 yrs.	Phallus 1: 1	N/A	Normal	Descended bilaterally	No	Duplicate	Duplicate	Atrophic right kidney	6Aβ
		Phallus 2: 1
Tepeler et al. 73	14 yrs.	Phallus 1: 2	N/A	Bifid	Descended bilaterally	No	Duplicate	Single	N/A	2Aα
		Phallus 2: 1
Tirtayasa et al. 74	12 yrs.	Phallus 1: 2	Epispadias	Bifid	Descended bilaterally	No	Duplicate	Single	Ectopic bowel segment	1Dα
		Phallus 2: 2
Tu et al. 75	Neonate	Phallus 1: 2	N/A	Bifid	Descended bilaterally	No	Duplicate	Single	N/A	1Aα
		Phallus 2: 2
Vilanova and Raventos 76	30 yrs.	Phallus 1: 2	N/A	Normal	Descended bilaterally	No	Single	Single	N/A	2Aα
		Phallus 2: 1
Wojewski and Kossowski 77	6 yrs.	Phallus 1: 2	N/A	Duplicate	Duplicate, descended bilaterally	No	Duplicate	Duplicate	Talipes equinovarus Ureter stenosis	1Aβ
		Phallus 2: 2
Zhang et al. 78	23 yrs.	Phallus 1: 2	N/A	Normal	Duplicate, descended bilaterally	No	Single	Single	N/A	7Aα
		Duplicate Glans
Zolfaghari et al. 79	4 mo.	Phallus 1: 2	Hypospadias	Normal	Descended bilaterally	No	Duplicate, one with blind ending	Single	Bilateral congenital hip dislocation, severe right talipes equinovarus and hypotrophy of the right lower limb. Inguinal hernia	1Aα
		Phallus 2: 2

Classification

Schneider has previously classified diphallia into four main categories:

Duplication of the glans alone

Bifid diphallia

Complete diphallia with each penis having two corpora cavernosa and a corpus spongiosum

Pseudodiphalia in which there is a rudimentary accessory atrophic penis existing independently of the normal penis

Our proposed classification is based on anatomical variants found within the literature on diphallia, which builds on Schneider's classification in order to provide a more specific description of the phallus soft tissue, as well as include a description of the pathway of the most normal urethra and the bladder configuration. The classification method has been proposed to be used to simplify the categorization of diphallia patients, using the system to classify the most intact phallus, the most normal urethra, and whether there is an additional surgical step regarding the bladder. The system will place the anatomy of diphallia into specific categories based on the structure of the phallus, the urethral anatomy and the bladder formations. Table 2 below displays the proposed categories.

Table 2

Proposed classifications of phallus, urethra and bladder found in Diphallia

Phallus
Character	Type
Separate phalluses, 3 corpora each	1
Separate phalluses, 3 corpora in only one	2
Separate phalluses, neither contain 3 corpora	3
Phalluses contained within same shaft skin, 3 corpora each	4
Phalluses contained within same shaft skin, 3 corpora in only one	5
Phalluses contained within same shaft skin, neither contain 3 corpora	6
Bifid glans	7
Urethra to most normal phallus
Character	Type
Normal urethra present	A
Urethral stenosis	B
Hypospadias	C
Epispadias	D
Bifurcation	E
Bladder
Character	Type
Single	α
Double	β
Exstrophy	γ

Results

With a review of the literature, and application of the proposed classification system, common diphallia configurations can be displayed. While these individuals may still differ in terms of specific anatomy, such as the relation of the phalluses to one another, the specific pathway of the urethras or the associated anomalies, the classification and the frequency in which they occur is based on the soft tissue make‐up of the phalluses, the urethra as it pertains to the most normal urethra and the bladder configuration. Of the reviewed literature with sufficient information, our classification showed that diphallia patients categorized as 1Aα contributed to the largest percentage of reports at 26.4%. The next most frequent pattern seen was 1Aβ, where the soft tissue and urethra were structurally normal, however there was a duplicate bladder, which made up 12.6% of the patients reviewed. The 2Aα configuration was the next most seen classification within the literature, appearing in 7% or 8.0%, followed by configurations 1Cα, 3Aα, 7Aα, which each contributed to 4.6% of the patients. The remaining reports and the corresponding classifications can be reviewed in Table 3. Table 4 then depicts the most common configurations found within the literature and additional examples of diphallia, which shows a graphic of the corresponding anatomy, an example of the gross anatomy extracted from their corresponding reference and the patient that correspond to the detailed classification.

Table 3

Proportion of diphallia anatomical variants within the literature

Classification	Count	Percent (%)
1Aα	23	26.4
1Αβ	11	12.6
2Aα	7	8.0
1Cα	4	4.6
3Aα	4	4.6
7Aα	4	4.6
1Aγ	2	2.3
1Dα	2	2.3
1Dγ	2	2.3
3Cα	2	2.3
4Aα	2	2.3
7Bα	2	2.3
7Cα	2	2.3
1Bα	2	2.3
1Cβ	1	1.1
1Cγ	1	1.1
1Eα	1	1.1
2Bα	1	1.1
2Dγ	1	1.1
2Eα	1	1.1
3Aβ	1	1.1
3Dα	1	1.1
4Cα	1	1.1
4Dγ	1	1.1
6Aα	1	1.1
6Aβ	1	1.1
6Cα	1	1.1
7Aα	1	1.1
7Aγ	1	1.1
7Bβ	1	1.1
7Cγ	1	1.1
7Dα	1	1.1

Table 4

Most common anatomical varriants for diphallia

Classification	Diagram	Gross anatomy	References
1Aα			Chadha et al. 18
1Αβ			Maher et al. 47
2Aα			Sina et al. 69
1Cα			Bhat et al. 15
3Aα			Leite et al. 46
7Aα			Zhang et al. 78

Associated anomalies

Upon review of the literature, several diphallia patients present with no other associated anomalies. However, several abnormalities can be seen in other diphallia patients. These anomalies arise from both genitourinary and gastrointestinal systems, as well as some reports seeing musculoskeletal or cardiovascular anomalies. The majority of the malformations fall within the former two. Genitourinary abnormalities include the presence of either a duplicate bladder , , , , , , , , , , , , or bladder exstrophy, , , , , , , as well as duplicate ureters, , vesicoureteral reflux, , and ureteric stenosis. Further anomalies within the urinary system include issues and malformations pertaining to the kidneys, which include single kidney agenesis, , , , , , , duplicate unilateral kidney, pelvic kidney and horseshoe kidney. , , Fistulas pertaining to the urinary system were also a common association with rectovesical and urethrorectal , , being noted. Next, there is also a wide range of gastrointestinal abnormalities that appear to arise in patients with diphallia. The most seen is the presence of an imperforate anus. , , , , , , , , , , , There can also be further duplication of various aspects of the gastrointestinal system associated with diphallia, which includes duplication of the rectum, colon, cecum, appendix, and terminal ileum. , , , , , , , Along with the mentioned fistulas mentioned above, perineal and tracheoesophageal fistula , have been reported as associated abnormalities pertaining to the gastrointestinal tract. It was also noted that there were hernias associated with diphallia patients, mostly those occurring at the umbilicus, , , , however inguinal hernias , , are also cited within the literature. Further gastrointestinal anomalies then include ectopic bowel segments, , omphalocele , and Meckel diverticulum.

In terms of musculoskeletal and cardiovascular abnormalities, there is a wide range of malformations shown in the literature that are associated with diphallia. Two common associations include both hemivertebra , , and a wide diastasis of the pubic bone , , , with further musculoskeletal malformations comprising of menigocele , and talipes equinovarus , and less commonly pre‐axial polydactyly, partial sacral agenesis, agenesis and hypotrophy of digits or limbs, , , , , or bilateral congenital hip dislocations. Cardiovascular malformations are more rare, however present in multiple patients, which include abnormalities such as atrial septal defects. , A summary of associated abnormalities pertaining to specific patients is outlined in Table 1.

Table 5 then displays the most commonly seen abnormalities seen in concordance with diphallia. Most commonly, an imperforate anus was seen associated with diphallia patients which was shown in 13.8% of the reviewed patients. Next, 9.2% of the patients also saw further duplication along the gastrointestinal tract, with duplications of either the rectum, colon, cecum, appendix or terminal ileum being reported. Single kidney agenesis and inguinal hernias were then the next most seen abnormalities, arising in 8.0% and 6.9% of the patients, respectively. Lastly, the most common musculoskeletal anomaly associated with diphallia was limb agenesis or hypotrophy, which appeared in 5.7% of the diphallia cases.

Table 5

Proportion of associated abnormalities

Associated Abnormality	Count	Percent (%)
Gastrointestinal
Imperforate anus	12	13.8
GIT duplication	8	9.2
Anorectal malformation	5	5.7
Ectopic bowel segments	2	2.3
Omphalocele	2	2.3
Oesophageal atresia with tracheoesophageal fistula	2	2.3
Meckel diverticulum	1	1.1
Genitourinary
Single renal agenesis	7	8.0
Horseshoe kidney	3	3.4
Duplicate ureters	2	2.3
Vesicoureteral reflux	2	2.3
Pelvic kidney	1	1.1
Duplicate kidney	1	1.1
Ureteric stenosis	1	1.1
Muskuloskeletal
Limb agenesis/hypotrophy	5	5.7
Wide diastasis of pubic bone	4	4.6
Hemivertebra	3	3.4
Meningocele	2	2.3
Talipes equinovarus	2	2.3
Sacral agenesis	1	1.1
Bilateral hip dislocations	1	1.1
Cardiovascular
Atrial septal defect	2	2.3
Hernias
Inguinal	6	6.9
Umbilical	2	2.3

Discussion

The paper highlights an overview of diphallia, illustrating different aspects of the anomaly including history, embryology and treatments. It also expands to provide a classification system that is built on previous works to give a system in which future patients can be categorized and compared. The results then feature the most common anatomical variations, showing that roughly 25% of the published instances have two phalluses with 3 corpora, at least a single normal urethra and a single bladder. The literature review and the published articles however may be biased as typically the more unique and interesting patients are presented, leaving a potentially large number of unpublished reports that could contribute to the current review and proposed classification system. The results regarding associated anomalies potentially hold a similar bias, in that unique abnormalities may have been focused on, leaving out seemingly minute associations. Lastly, as new patients may be presented, and different variants may arise in which the proposed classification system may or may not encompass, or penile anomalies such as triphallia or triple penis, as reported by Jabali et al. get reported, the current proposed classification may need to be modified.

Conclusion

Following a literature review, each diphallia patient is a unique variant with its own anatomical configuration and associated anomalies. This has led to the proposed classification system that builds on previous bodies of work to categorize each patient based on the most normal aspects of the diphallia. By classifying the structure of the phallus that is to be kept, the pathway of the urethra present within the most normal phallus and the bladder morphology, a surgical approach can be broached and executed to ensure a satisfactory functional goal, with preserved continence, erectile function, and cosmetic outcomes.

Conflict of interest

The review is not registered, and the protocol was not prepared. Support from the Paediatric Surgery and Urology Department at the Queensland Children's Hospital. None declared.

Author contributions

Dylan John Kendrick: Conceptualization; data curation; formal analysis; investigation; methodology; visualization; writing – original draft; writing – review and editing. Roy Mark Kimble: Project administration; supervision; writing – review and editing.