Zinner syndrome in adult male: a rare case report

Introduction

Zinner syndrome (ZS) is a rare congenital urogenital malformation in men, which is caused by abnormal development of the mesonephric duct and blocked ascent of the ureteric bud during early embryonic development. Its typical triad includes seminal vesicle cysts, ejaculatory duct obstruction, and ipsilateral renal agenesis or dysplasia (1). First reported by Zinner in 1914 (2), ZS has an incidence of about 2.14 per 100,000. The disease onset is insidious. Patients usually seek medical treatment due to pain and discomfort in the inguinal area and pelvic cavity, accompanied by symptoms of urinary tract obstruction or bladder irritation during sexual activities or the reproductive active period. The main clinical symptoms include dysuria, frequent urination, perineal pain, epididymitis, pain during ejaculation, etc. (1,3). It may be accompanied by infertility (4). If the symptoms are obvious, surgical treatment will be required. Since ZS has been rarely reported both at home and abroad, many clinicians are not fully aware of it. Currently, the diagnosis of ZS mainly relies on imaging examinations, and accurate imaging diagnosis is crucial for the selection of its treatment options. We present this case in accordance with the CARE reporting checklist (available at https://tau.amegroups.com/article/view/10.21037/tau-2024-763/rc).

Case presentation

Male patient, 40 years old, a worker, was admitted to the hospital due to difficulty in urination for 5 days without obvious cause, accompanied by frequent urination and urgent urination. There was no hematuria, hemospermia, fever, night sweats, nausea or vomiting. He was married and had children. He had congenital absence of the left kidney and had no history of genetic diseases or infectious diseases.

There were no obvious abnormalities in the physical examination. There was no percussion pain in the bilateral renal areas, no tenderness in the ureteral areas and bladder area, and nothing special in the external genitalia. Laboratory examinations, including routine blood, urine and feces tests, renal function tests (creatinine, uric acid, urea, glomerular filtration rate), urine culture and drug sensitivity tests, etc., showed no obvious abnormalities.

The transabdominal ultrasound in an external hospital indicated an absent left kidney, subsequently confirmed on computed tomography (CT) (Figure 1A). Meanwhile, the right kidney showed compensatory enlargement. The left seminal vesicle was enlarged, with the maximum diameter measuring approximately 5.5 cm × 4.5 cm × 1.5 cm, and its density was not uniform. On the axial plain CT scan, the density of the lesion in the left seminal vesicle area was slightly higher than that of the bladder, and the boundary with the left posterior wall of the bladder was not clear (Figure 1B). On the magnetic resonance imaging (MRI) scan, a roundish lesion with significantly high signal intensity on T1-weighted imaging (T1WI) (Figure 1C) and slightly high signal intensity on T2-weighted imaging (T2WI) (Figure 1D) was seen in the left seminal vesicle area. The signal was relatively homogeneous and the boundary was clear. On the sagittal plane of T2WI, a residual tubular structure extending upward in the left seminal vesicle area was observed (Figure 1E). There was no obvious diffusion restriction shown on the apparent diffusion coefficient (ADC) map (Figure 1F) and the high b-value diffusion-weighted imaging (DWI) map (Figure 1G). No enhancement was seen on the contrast-enhanced scan, and the lesion pushed forward against the left posterior wall of the bladder (Figure 1H). According to the classification system of seminal vesicle cysts proposed by Tan et al. (5), this case belongs to type II cysts, and active surgical intervention is required to relieve compressive symptoms and prevent the spread of infection. The laparoscopic images are shown in Figure 1I. The patient underwent laparoscopic resection of the left ureteral stump, left seminal vesicle, and partial bladder. The gross specimen was shown in Figure 1J, which was consistent with the seminal vesicle cyst and ureterocele. Postoperative pathology showed that there was infiltration of acute and chronic inflammatory cells in the fibromuscular cyst wall, and focal necrosis was visible (Figure 1K,1L).

Figure 1 Imaging findings of the patient. (A,B) Coronal and axial plain CT of the abdomen confirms the presence of a large cystic lesion in the pelvic area with the absence of the homolateral kidney (white arrows). (C) Axial non-contrast T1 weighted MR shows significantly hyperintense signal in the left seminal vesicle cyst (white arrow). (D) Axial T2 weighted MR with fat saturation underline the mild hyperintensity of the left seminal vesicle cyst (black arrow). (E) Sagittal T2 weighted MR mild hyperintense signal (white arrow). (F,G) ADC (black arrow) and DWI (white arrow) map show no restriction of the cyst. (H) Axial contrast-enhanced T1 weighted MR subtraction image shows the absence of contrast enhancement (white arrow). (I) Laparoscopic image. (J) Gross specimen, left seminal vesicle cyst, ureterocele. (K,L) Postoperative pathology, there is an infiltration of acute and chronic inflammatory cells in the fibromuscular cyst wall, and focal necrosis can be seen (HE staining, ×100). ADC, apparent diffusion coefficient; CT, computed tomography; DWI, diffusion-weighted imaging; HE, hematoxylin and eosin; MR, magnetic resonance.

All procedures performed in this study were in accordance with the ethical standards of the Ethics Committee of The Central Hospital of Wuhan and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

ZS is a rare genitourinary system disease characterized by congenital seminal vesicle cysts combined with ipsilateral renal agenesis. It is more commonly manifests in men aged between 20 and 40 years who are at the peak age of sexual life. Both the urinary system and the reproductive organs originate from the mesonephric duct (6). The growth factors secreted by the metanephric blastema induce the growth of the ureteric bud, and the ureteric bud also secretes growth factors and proliferates. The fusion of the two forms the outline of the primitive kidney. Any interference with this fusion process will lead to renal agenesis or hypoplasia. Meanwhile, the failure of the separation between the ureteric bud and the terminal end of the mesonephric duct will lead to the atresia of the ejaculatory duct and the obstruction of the seminal vesicle, resulting in the accumulation of secretions and the cystic dilation of the seminal vesicle (7). Some scholars believe that when renal agenesis combined with ipsilateral seminal vesicle cysts is found, the possibility of ZS should be considered. The review analysis by van den Ouden et al. (4) showed that the incidence on the right side is relatively higher. Ectopic opening of the ureter and the presence of non-functional ureteral tissue around the seminal vesicle are important reference bases (8-10). Therefore, the main manifestations of ZS are unilateral ejaculatory duct obstruction, ipsilateral seminal vesicle cysts, and ipsilateral renal hypoplasia. Sheih et al. (11) conducted ultrasound screenings on 280,000 children within the last 2.5 years. Statistical findings showed that the proportion of pelvic cystic lesions combined with ipsilateral renal hypoplasia or renal agenesis was only 0.0046%, which is truly rare. As the volume of the seminal vesicle cysts gradually increases in patients with ZS, it can compress the surrounding adjacent organs and cause symptoms of urinary tract obstruction or bladder irritation (12). Digital rectal examination can reveal a cystic mass on the posterolateral side of the prostate, with obvious tenderness. When accompanied by a seminal vesicle abscess, a fluctuating sensation may be felt (13). Among patients with ZS, seminal vesicle cysts with a maximum diameter usually less than 5 cm generally do not cause clinical symptoms (5,14,15), while seminal vesicle cysts with a diameter of ≥5 cm usually cause related symptoms due to compression of the posterior wall of the bladder, the prostatic part of the urethra, etc., and may even cause compression of the rectum and lead to poor defecation (16).

Regarding the treatment of ZS, if the patient has a small seminal vesicle cyst and is asymptomatic, no special treatment is required, and regular review is sufficient. Drug therapy is usually used as a palliative measure or for patients with mild symptoms. For patients with relatively large cysts who have obvious clinical symptoms or have already suffered from infertility, surgical treatment is recommended. Surgical methods include transrectal or perineal puncture and aspiration of seminal vesicle cysts, open surgery, laparoscopic resection of seminal vesicle cysts, etc. (17,18). Robot-assisted laparoscopic surgery for this disease has the advantages of clear vision, minimal trauma, rapid postoperative recovery, and fewer complications. It is currently the best treatment option (19-22). Although the primary focus of treatment typically revolves around managing urinary system symptoms and addressing anatomical abnormalities, it is of utmost importance to consider the potential fertility issues faced by these patients. ZS is a rare congenital urogenital disorder that can significantly impact a patient’s fertility. It is often difficult to assess the fertility status during adolescence. Semen analysis should be conducted after reaching adulthood. Hofmann et al. (23) found in their research that the semen parameters of some patients improved after surgery, yet the surgery had limited effectiveness in improving fertility. Similarly, the study by Tang (24) indicated that laparoscopic resection alleviated patients’ symptoms, but had limited effect on resolving infertility issues. As a result, assisted reproductive technology has gradually become the main treatment strategy. The classification system of seminal vesicle cysts proposed by Tan (5), by integrating the cyst size, infection status, and associated malformations, provides an important basis for the individualized treatment of ZS. This case belongs to type II seminal gland cysts, accompanied by urinary irritative symptoms such as dysuria. Active surgical intervention is required to relieve the compressive symptoms and prevent the spread of infection. During the surgery, it was found that the cyst was severely adhered to the surrounding tissues and organs, making separation difficult, and there was inflammatory infiltration. Subsequently, the urologist performed laparoscopic resection of the seminal vesicle cyst, residual ureter, and part of the bladder. The patient recovered well after the surgery. Symptoms such as dysuria, frequent urination, and urgency were significantly improved. So far, no recurrence has been observed during the follow-up.

Ultrasound, CT, and MRI all contribute significantly to the diagnosis of ZS. Ultrasonography can be used as a screening method for ZS, and the typical manifestation is an anechoic mass in the seminal vesicle region (25,26); the accuracy of trans-rectal ultrasonography is higher than that of pelvic ultrasonography, but its field of view is small (27). Intravenous urography can assess the abnormalities of the kidneys and ureters and whether the seminal vesicle cysts communicate with the urinary tract. However, it cannot display the adjacent anatomical structures of the seminal vesicle cysts (28). Both CT and MRI can accurately locate the seminal vesicle cysts. Moreover, they have a large scanning range and a wide field of view and can often detect abnormalities of other organs at the same time. In terms of imaging, CT scanning can determine whether the seminal vesicle cysts are accompanied by ipsilateral renal hypoplasia or renal agenesis. Sometimes, the dilated vas deferens, ejaculatory ducts and ectopically dilated residual ureters communicating with the seminal vesicles can be seen, but the components of the cysts cannot be determined (9). MRI can display the anatomical structures of the pelvis and the male reproductive tract, accurately identify the residual ureter that is easily overlooked by CT, distinguish the components and nature of the seminal vesicle cysts, and then make a differential diagnosis between the seminal vesicle cysts and other pelvic cystic masses (29). Therefore, MRI can be used as the preferred examination method for ZS. Arora et al. (30) believed that MRI is more specific and can further distinguish the components and nature of the seminal vesicle cysts. There are also studies claiming that the T1WI hyperintensity in seminal vesicle cysts indicates a high protein content or possible bleeding in the lesion (31). In this case, the MRI of the seminal vesicle cysts showed a hyperintense signal on T1WI, and the signal of the lesions was relatively homogeneous, suggesting that there might be a high protein content within the cyst or combined bleeding. On the contrast-enhanced scan, no enhancement was observed in the cyst contents. The cyst wall was thin, and the boundaries became clearer, which was consistent with previous studies.

This disease needs to be differentiated from the following lesions:

• Simple seminal vesicle cysts are the local dilation of the seminal vesicle ducts, with regular shapes, mostly round or oval-shaped. They are often located on one side of the seminal vesicle gland and are not accompanied by congenital hypoplasia of the kidneys and ureters.
• Acquired seminal vesicle cysts usually occur bilaterally at the same time and are more common in elderly patients with chronic seminal vesicle and prostatic inflammation, or the formation of scars in the seminal vesicle due to surgical history, which subsequently leads to secondary obstruction and cystic dilation.
• The Mullerian duct cysts are located in the exact center at the back of the upper half of the prostatic urethra and is not connected to the seminal vesicle duct or the prostatic part of the urethra. The cause of this disease is the cystic dilation of the incompletely degenerated Mullerian duct in the prostate. In the coronal/sagittal plane, they are often typically inverted water-drop-shaped.
• The ejaculatory duct cysts are located in the verumontanum area at the back of the prostatic part of the urethra. The direction of the long axis is consistent with the course of the ejaculatory duct. They are usually oval-shaped or tubular and do not compress adjacent organs and not accompanied by abnormal development of the kidneys and ureters.
• Ureteral cysts refer to cystic lesion formed at the lower end of the ureter that protrudes into the bladder, with a clear boundary and uniform density/signal. Its size changes with urination activities. Stones may occur concurrently inside the cyst, and it can also be accompanied by hydronephrosis and ureteral duplication deformities of the ipsilateral kidney and ureter, but it is not accompanied by the absence of the ipsilateral kidney and ureter.

Conclusions

In conclusion, ZS is a rare congenital abnormal development deformity of the male genitourinary tract. The common clinical manifestations include urinary tract irritation, perineal pain, dysuria and infertility. There are also some asymptomatic patients. Clinically, when the above symptoms are present along with the typical triad, this kind of disease should be considered. Integrating its characteristic imaging features will help improve the diagnostic accuracy of this disease.

Acknowledgments

We thank Dr. Xiutao Zhang for providing accurate information in this case report.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://tau.amegroups.com/article/view/10.21037/tau-2024-763/rc

Peer Review File: Available at https://tau.amegroups.com/article/view/10.21037/tau-2024-763/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tau.amegroups.com/article/view/10.21037/tau-2024-763/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the Ethics Committee of The Central Hospital of Wuhan and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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