We choose the four most popular, widely available databases for this systemic review: PubMed®, PubMed Central® (PMC), Scopus, and Clarivate Analytics's Web of Science (WoS). The keywords we searched for were: “urethral duplication”, “urethral multiplicity”, “prepubic sinus” and “urethral triplication”. The search results were restricted to the last 15 years (2008–2023). The last search was done on 31/12/2023. All the results were downloaded in the corresponding format and uploaded to our account on the Covidence platform for screening and data extraction. All the required steps and tasks were followed. After removing the duplicates, title and abstract screening were done, followed by full-text screening by each reviewer.

Our review included all the case reports and case series (human studies) of urethral duplications, prepubic sinuses, and urethral triplications of pediatric-age boys (under the age of 18). We excluded studies presenting patients of adult age, female sex, with bladder duplication without urethral multiplicity, or patients with complete penile duplication and penile agenesis associated with urethral multiplicity. If the case series presented patients eligible for our inclusion criteria, we included them in our database, excluding only those not eligible participants.

We modified Covidence's template for data extraction to fit our preferences. As general information, we extracted from each paper the following (11 parameters): DOI number, Title, Lead author name, Continent, Country in which the study was conducted, Aim of study, Study design, Start date, End date, Study funding sources, Possible conflicts of interest for study authors. For participant(s) data, we noted (3 parameters): Inclusion criteria, Exclusion criteria, and Method of recruitment of participants. Our study aimed to obtain individual patient data of each participant from every included case report and case series in as much detail as possible. As baseline population characteristics, we extracted (22 parameters): Age at diagnosis, Age at intervention, Presentation, History of UTI (urinary tract infection)/obstruction, History of urinary incontinence, History (Other), Preop investigations (Genitourinary), Diagnosis made with, Description of Micturating cystourethrogram (MCU), Description of the urethra, Length, Other findings, Associated genitourinary anomalies, Other associated anomalies, Effman's classification, Surgical technique, Additional surgeries, Number of interventions, Complications, Follow up, Qol-questionnaires/Surveys, Outcome/Continence/Cosmesis, Histology, Number of excluded female patients. Data extraction was cross-checked independently by all four reviewers. Any disagreements were solved by consensus. The process is associated with a flowchart detailing the flow from the search through source selection, duplicates, retrievals, and any additions. The workflow is shown in Figure 2.

Case reports and case series are uncontrolled study designs known for their increased risk of bias. Still, due to the lack of evidence, these publications on rare diseases such as urethral multiplicity have profoundly influenced the medical literature and continue to advance our knowledge (8). For quality assessment, we modified and individualized Covidence's Quality Assessment Template based on the JBI critical appraisal tool for case series (9), BMJ's methodological quality and synthesis of case series and case reports (8), and Joanna Briggs Institute's approach (10). One investigator carried out the assessment, and the others cross-checked it. In case of disagreement, it was resolved by consensus in the presence of the fourth reviewer. We searched for the following risks: (A) Were there clear criteria for inclusion in the case report/series? (B) Was the condition measured in a standard, reliable way for all the participants? (e.g., the study should clearly describe the method of measurement of the condition in a standard and reproducible way.) (C) Did the case series have consecutive inclusion of participants? (e.g., a consecutive inclusion is more reliable than those that do not: “We included all patients (x) with urethral duplication who presented to our clinic between 1992 and 2015” is more reliable than a study that states, “We report a case series of×patients with urethral duplication.”) /Does the patient(s) represent(s) the whole experience of the investigator (center), or is the selection method unclear to the extent that other patients with a similar presentation may not have been reported? (D) Was the patient's history clearly described and presented as a timeline? [A good case report will clearly describe the patient's history, including their medical, family, and psychosocial history, relevant genetic information, and relevant past interventions and outcomes. (CARE Checklist 2013)]; (E) Was/were the patient(s) presented clearly and adequately (e.g., demographics, existing health condition, physical and laboratory findings, and associated morbidities and Effman's classification for each patient separately)? (F) Were valid medical investigation methods used to identify the condition of all participants? (G) Were the details of the surgical treatment described adequately for each participant? (H) Were all the complications and their treatment (if possible) well described and reported? (I) Was the duration of the follow-up described for each patient separately? (J) Were the outcome results of the case/cases clearly described? Possible item ratings were yes, unclear, no, or not applicable. Data were extracted in “.xlt” format and analyzed further via Microsoft Excel. Descriptive statistics for variables were reported as median and min-max values, mean ± standard deviation (SD), absolute number (n), and percentage (%). The non-parametric Mann-Whitney U test was used to compare continuous variables.

There were 90 studies included in the study. Of these, 62 were case presentations, and 28 were case series. The distribution of the studies across continents was as follows: Asia with 49, Europe with 16, North America with 9, South America with 4, Africa with 8, Australia with 1, and multi-continental 3 studies. The studies were conducted in 26 different countries, with India having the highest number of studies—20, followed by Turkey—12, and the United States—8.

The total number of patients included in our study was 250. Based on the classification of Effman, there were 38 cases of type I (15.3%), 21 cases of type IIA1 (8.4%), 55 cases of type IIA2 (22.1%), 91 cases of type IIA2Y (36.5%), 4 cases of type IIB (1.6%), and 9 cases of type III (2.4%). We also included 19 cases of prepubic sinuses (7.6%), 9 cases of triplication (3.6%), and 6 cases of unknown-type duplications (2.4%) in our review. Figure 3 illustrates the distributions of urethral multiplicity types.

There were clear criteria for inclusion (97.77%), the conditions were measured in a standard, reliable way (90%), and there was a consecutive explicit inclusion and selection method (94.44%) for most of the included articles. The patient's medical history (63.33%), general presentation—including demographics, existing health condition, physical and laboratory findings, and associated morbidities and Effman's classification—(58.88%), complications (42.22%), follow-up (58.88%), and outcome (64.44%) were described adequately in approximately half of the papers. Also, we found qualitative information about the investigation methods (86.66%) and the applied surgical techniques (93.33%) in almost every report/ series.

The mean score value for all the included studies was 7.5 ± 1.91. Case series-type articles gained a lower score: 7.21 ± 2.2 vs. 7.62 ± 1.77 (p = 0.344). Also, there were more limited data, according to patient presentation, medical history, follow-up, and outcomes, in case series than in case presentations.

There were nineteen cases of prepubic sinuses. The age of the presentation was 4 years on average. In three cases, the diagnosis was made at birth, but the intervention was postponed for two years in two cases and three years in one case.

The most common symptom at presentation was discharge, reported in fourteen cases, that was purulent in seven instances, serous in three -, mucoid in two -, and unspecified in two cases. In two instances, erythema/inflammatory response (fever) was observed, and in one case, pain was reported. In terms of medical history, two instances involved circumcision, and two cases involved infection (pubic abscess). Treatment involved surgical intervention: complete excision in all the cases. Preoperatory investigations and the results of the histology exams are presented in Table 1. The outcomes were excellent in all the cases.

Thirty-eight cases of type I urethral duplications were identified, including type IA in twenty-two and IB in eight cases, according to the Effman classification and not specified in eight cases. The average age at the time of intervention was 4 years and 7 months, and in six cases, the intervention was postponed or delayed.

A visible secondary meatus was observed at presentation in twenty-seven out of thirty-eight cases. This meatus was located dorsally/epispadiac/peno-pubic positions in sixteen cases and ventrally/proximally/hypospadiac/peno-scrotally in seven cases. Eight patients didn't experience any symptoms (the malformation remained asymptomatic), while six boys had discharge that was either sero-mucoid or purulent in 3–3 cases. Other symptoms included double urinary stream, infection in 2–2 cases, and dorsal chordee and distal hypospadias in 1–1 cases. Five boys had a history of circumcision, while five others had infections such as UTI or penoscrotal abscess. The preoperative investigations, associated anomalies, and treatment options in type I urethral duplications are listed in Table 2.

In addition to the surgical treatments listed in Table 2, various other procedures were performed. Two cases underwent chordectomy, two cases received glanduloplasty/penoplasty, circumcision was carried out in three cases, TIP repair in one case, Browne hypospadias repair in one case, incision of the web in one case, and diverticulectomy in one case. All cases had excellent outcomes without reported complications, and follow-up was conducted for up to six years. Histological examination was only presented in three cases, which revealed urothelium in two cases and stratified keratinizing epithelium in one case.

There were a total of twenty-one cases of type IIA1 urethral duplications, with an average age of presentation being 3 years and 6 months. Out of these cases, eleven were diagnosed at birth.

The most common presentation was a visible secondary urethral opening, with sixteen cases reported. Among these cases, eleven were dorsal/epispadiac, and one was hypospadiac. Other presentations included incontinence (six cases), two urinary streams (two cases), swelling during voiding (one case), poor flow (one case), recurrent UTI (three cases), bladder exstrophy (three cases), and fecaluria (one case).

Regarding functionality, nine out of the twenty-one cases had a normal functional apical urethra, while three cases had an incontinent epispadiac/dorsal urethra. Two cases had a main hypospadiac meatus, and two had urine dribbling from the penile urethral meatus and passed urine in a stream from the anterior anal verge. Two boys had anal urinary leakage.

Three boys had a history of circumcision, and three cases had a history of recurrent UTIs.

Preoperative investigations, associated anomalies, and treatment options are listed in Table 3.

In fourteen cases, the duplications were corrected in a single-stage manner. However, there were also cases where up to 5 interventions were required. Complications were presented in five cases, which included fistula formations in three, dorsal penile skin loss, and stenosis in 1–1 cases. The follow-up period ranged from 9 months to 14 years, and the outcomes were functionally and aesthetically satisfactory.

There were fifty-five cases of type IIA2 urethral duplication that presented at the age of 3 years on average. The presentation was related to morphology and function symptoms. Morphology-related symptoms included a visible secondary meatus in fifteen cases, with two being orthotopic, four being epispadiac, one being hypospadiac, one having bladder exstrophy, and one having splitting. Function-related issues included a double urinary stream in twelve cases, with three having a more functional ventral meatus and one having both functional meatuses. Other function-related issues included incontinence in eight cases, straining in four cases, thin stream in two cases, swelling of the penis increasing with urination in one case, flow from the umbilical region in one case, no voiding in one case, painful terminal hematuria in one case, and asymptomatic in four cases.

The history of these cases included UTI in thirteen cases, circumcision in five cases, colostomy in three cases, prematurity, operated Fallot tetralogy, and orchiectomy for teratoma in 1–1–1 cases.

Preoperative investigations, associated anomalies, and treatment options are listed in Table 4.

Regarding contrast studies, in fourteen cases, a single channel arising from the bladder was described, splitting into two, coursing independently to the meatuses.

The dorsal tract is usually less developed and stenotic at its origin, while the ventral tract can present dilations, diverticula, and tortuosities at the base and can be stenotic distally. In some cases, both urethras are functional and of good caliber.

Outcomes are generally good. However, stress incontinence, dysuria, straining, psychological problems, and erectile dysfunctions have been reported. Complications were described in nine cases, with eight cases of stenosis (successfully treated with dilatations in five and requiring Mitrofanoff in three cases). Follow-up was conducted for up to 12 years.

There were a total of ninety-one cases of type IIA2Y urethral duplications.

In this specific type of urethral duplication, twenty-five patients were described as having a predominantly ventral type of voiding. Seven patients presented with a double urinary stream; in six cases, the micturition was primarily orthotopic (dorsal), whereas four patients voided only per rectum. Morphologically, ten patients were observed to have two urethral orifices, one orthotopic or epispadiac (normal sized, or as a blind-ending megalourethra, or as a small orifice), and a ventral opening in the rectum, perineal region, raphe, or at the penoscrotal junction.

There were several complaints related to function, including dribbling from various areas (ten cases) such as the prepuce (one case), glans (two cases), near the dentate line (one case), anus (four cases), and perineum (two cases); voiding with two streams (seven cases); voiding per rectum since birth (five cases); incontinence (three cases), dysuria (two cases), straining (one case), inappropriate bladder drainage (one case), wetting the perineum (one case), and sitting on the toilet when urinating (one case). Additionally, there were eight cases of UTIs, one case of abdominal distension, and one case where catheterization was impossible.

The orthotopic urethra was either stenotic, atretic, or hypoplastic in forty-two cases; it was partially stenotic in thirty cases and was of good caliber in nineteen cases. The length of the stenotic part varied from case to case. In sixty-six cases, the ventral urethra was in an anal or rectal position, in eighteen cases, it was in a perineal position, three cases were abortive, and in four cases, it was of an unspecified position.

The perineal opening of the ventral urethra is not always on the midline. It can be found in the gluteal area at either 3 or 11 o'clock. The ventral urethra had a better caliber. However, eight patients had stenotic ventral urethra. When both urethras are stenotic or abortive, renal failure is the consequence.

Preoperative investigations, associated anomalies, and treatment options are listed in Table 5.

Complications that were observed during follow-up for up to 30 years included meatal stenosis, recalcitrant stenosis, multiple stenosis, anastomosis site stenosis (nineteen cases), fistula (seven cases), infection (three cases), urethral diverticulum (one case), stenosis that required Mitrofanoff (one case), fibrosis of the neourethra (two cases), wound dehiscence (one case), and urinary catheter malfunction (one case).

The outcome was variable.

There were only four patients presenting this rare type of urethral duplication. They presented, on average, at the age of 7 years.

The patients complained about various symptoms such as straining or had neuropathic bladder while urinating with single-stream. The diagnosis was made incidentally.

Preoperative investigation showed that two patients had undergone MCU and RU, while two others had undergone cystourethroscopy and ultrasonography.

Associated anomalies were also found in these patients, such as a scrotal abscess in one, a non-functional kidney in another, and caudal regression and a tethered cord.

The surgical techniques used for these patients included urethra-urethrostomy, excision of the accessory urethra, and dilatation of the urethra—in case of stenosis.

There were six patients with an average age of 4 years. Their presentation included visible secondary meatus, with glandular, penile, perineal, and recurrent UTIs being the most common. Preoperative investigations included methylene blue injection, cystoscopy, fluoroscopy, ultrasound, micturating cystourethrography, MRI, CT, retrograde urethrography, and intravenous urography. Associated anomalies were observed in the genital, urinary, and general areas.

Surgical interventions included mobilization of urethras, side-to-side urethrostomy, penoscrotal urethrostomy, excision of the dorsal accessory urethra, and no treatment. No complications were reported, and follow-ups were done for up to one year.

There were a total of nine patients with various symptoms: three of them urinated from the rectum, one had drops from the epispadic urethral meatus, one had abnormal foreskin, one had perineal voiding, one had enlargement of the penis during voiding, one had dribbling, and two had a double urinary stream. Additionally, one patient had a fever, one had abdominal pain, one had visible accessory urethras, one experienced fecaluria, one had incontinence, one had UTI, and one had dysuria.

There are some possible anatomical variations. There is always an orthotopic functional urethra with one or two epispadiac urethras, which open glandularly or on the dorsal surface of the penis. Ventrally situated urethras might open in the rectum/anus/perineum or on the ventral surface of the penis. In some cases, there are only epispadiac or only hypospadiac secondary urethras. Figure 4 represents the variations of urethral triplications we found. We encountered two of each 1,2,3 variations and one of each 4,5,6. As a particularity, four cases showed a Y triplication (11–14): a common proximal urethra divided into three channels.

Preoperative investigations, associated anomalies, and treatment options are listed in Table 6.

There were no reported complications. Follow-up: up to 4 years. The outcome was satisfactory in most of the cases.