Zinner syndrome: a rare diagnosis in infancy

Background

Zinner syndrome (ZS) is a rare diagnosis affecting men, with only 50 cases reported in the paediatric population. Furthermore, only 12 cases have been reported in infancy; however, most patients remain asymptomatic.1 Moreover, there have been rare reported cases of malignancy in adult patients.2 Hence, careful understanding of this syndrome and follow-up of patients are necessary to avoid morbidity and mortality from this treatable condition. ZS occurs due to an abnormality of the Wolffian duct during embryogenesis, presenting with a triad of seminal vesicle cyst (SVC), ipsilateral renal agenesis or multicystic dysplastic kidney and ejaculatory duct obstruction; however, other pelvic cystic structures must be ruled out with initial investigations.3

Case presentation

The patient presented to the outpatient department at our institute in his early infancy, who had full-term normal vaginal delivery and normal milestones for his age. He did not have any history of surgery or medical comorbidities at presentation. The patient had been asymptomatic since birth; however, abnormalities had been noted on ultrasound during pregnancy. He was previously investigated at other hospitals.

Investigations

Antenatal ultrasonography (USG) done at a private clinic at 25 weeks gestation diagnosed a left-sided gross hydroureteronephrosis with a pelvic anteroposterior diameter of 12 mm and 21 × 10.5 mm curved tubular structure seen posteroinferior to the urinary bladder. The remainder of the findings was normal for the patient’s age. Another USG was repeated 4 days after birth at the same private clinic, which revealed similar findings. Serum creatinine of the baby 1 week after birth was 0.6 mmg/dL, and urine routine microscopy showed 2–4 pus cells/High power field which were within normal limits for his age. At the age of 1 month, the patient underwent contrast-enhanced CT scan of the abdomen at another private clinic and was diagnosed with a 5.2 × 4.7 × 6 cm multicystic area in the left renal fossa with no renal contrast excretion on the left side suggestive of multicystic dysplastic kidney (figure 1). It also showed a tubular dilated structure along the course of the left ureter which is seen traversing posterior to the urinary bladder into the rectovesical pouch (figure 1). The patient presented to our institute with the above investigations already performed. A DMSA scan was subsequently carried out, in which the left kidney was non-functioning/not visualised.

MRI abdomen including KUB region was done at 4 months of age and showed left gross hydronephrosis with atrophic parenchyma with the left renal pelvis communicating with left ureter and the blindly ending ureter (figure 2). A 34 × 24 mm multilobulated cystic lesion adjacent to the urinary bladder communicating with the prostatic urethra was suggestive of an SVC. The left seminal vesicle was not visualised separately from the cystic structure. The right seminal vesicle was visualised.

The case was discussed with radiology department, and a repeat USG was done at 6 months of age which showed similar findings of gross hydronephrosis on the left side (6.29 × 4.3 cm) and a lobulated cystic lesion (3.5 × 2.3 cm) posteroinferior to the bladder base on the left side. A voiding cystourethrogram done at 6 months of age showed a bladder capacity of 30 mL, dilated posterior urethra, irregular bladder wall, no vesicoureteric reflux (VUR) and a postvoid residue of 5 mL (figure 3). A note was made of a saccular structure on the posteroinferior side of the bladder on the left side on anteroposterior view which was not seen on the postvoid images.

The patient was further planned for cystoscopy which was delayed due to the COVID-19 pandemic and the subsequent lockdown. On relaxation of stringent lockdown rules, a cystoscopy was performed, at which point the patient was over 1 year old. This showed a normal urethra and bladder wall in which the right ureteric opening was visualised as normal; however, the left ureteric orifice (UO) was not seen.

Differential diagnosis

There are some important differential diagnoses to consider when diagnosing pelvic cystic lesions postnatally.3 4 First, prostatic utricular cysts (PUCs) should be ruled out given their midline position and communication with the urethra, along with their association with bilateral seminal vesicles and erectile dysfunction. A very common characteristics of younger patients with PUC include differences in sex development, with other features such as VUR, hypospadias and cryptorchidism noted. Another differential diagnosis would be Müllerian duct cysts (MDCs); however, these do not communicate with the urethra. Furthermore, MDCs typically do not occur at such a young age but with older individuals. On the other hand, individuals diagnosed with MDCs often have normal external genitalia with the pelvic cyst often in the midline, as seen in ZS. It is pertinent to note that both SVCs seen in ZS and ejaculatory duct cysts (EDCs) arise from the Wolffian duct, whereas PUC and MDC develop from Müllerian ducts. Wolffian duct cysts are paramedian and often are associated with upper urinary tract abnormalities.5 6

EDCs should also be considered, again due to their midline nature. Another differential would be an ectopic hydronephrotic pelvic kidney or ureter, with further alternative diagnoses being ureterocoeles or possibly bladder diverticula explaining the retrovesical collection.5–7 Distinctions between each of these bladder abnormalities can be made using their position in relation to the bladder neck (lateral, paramedian or median) or by identifying and grouping them together with concomitant anomalies of the urogenital tract.5–8 For example, an ectopic hydronephrotic pelvic kidney appears as a cystic pelvic mass, similar to ZS. Contrast excretion would be noted along with an aberrant artery inflowing the ectopic kidney. In a similar fashion, bladder diverticula are both cystic and paramedian, again like ZS. On the other hand, bladder diverticula can be ruled out in a patient with ZS given the normal seminal vesicles and definitive diagnosis on cystoscopy. A less likely but nonetheless important differential to exclude would be ectopic ureterocoeles as they would show as pelvic structures, lateral in location; however, they are most usually found at the lower end of the ureter.9

It is important to note that although we have focused mainly on the differential diagnoses of pelvic cysts postnatally, but antenatally also, pelvic cysts can have a wide range of differentials. These may be urinary tract related such as ureterocoeles, urachal abnormalities, urinomas and renal cysts. Other non-urinary tract related abdominal cysts can be observed antenatally, such as cystic neuroblastomas, choledocal cysts, meconium cysts, lymphangiomas or enteric duplication cysts to name just a few .10 It is also extremely important to mention the possibility of abdominal neoplasms such as teratomas which may be a reason for early delivery of the fetus.11 Despite this, it is rare for intra-abdominal cysts to affect management in the prenatal period or require early delivery of a fetus; however, many fetuses that have persisting cysts after birth do require some form of surgical intervention.

Treatment

Given the asymptomatic presentation of our patient, he was treated conservatively. Cystoscopy was done which revealed normal urethra and normal right UO. The left UO was absent, and the rest of the findings was normal.

Outcome and follow-up

Asymptomatic or minimally symptomatic patients can safely be managed conservatively with long-term follow-up; therefore, we have planned for a long-term follow-up of our patient, at least until he reaches adolescence.