Bladder stone causing vesicovaginal fistula and migration into the vagina

Background

Neurogenic bladder is commonly associated with urinary stasis and urinary tract infections that can lead to bladder stone formation, more so, in patients managed with indwelling urinary catheters. It can present with frequent catheter blockages and pericatheter leaks.

This case report highlights a very rare complication of bladder stone where it caused pressure necrosis of the bladder wall leading to vesicovaginal fistula (VVF) formation. The stone then migrated in the vagina and was causing rectal pain and bleeding and if left untreated could result in rectovaginal fistula, sepsis and significant risk of mortality.

This case emphasises the importance of understanding the common and serious complications associated with neurogenic bladder especially in patients with indwelling catheters. If there is a persistent problem with catheter management, further evaluation by a urologist must be considered.

Case presentation

We present a case of a woman in her late 70s with a background of progressive multiple sclerosis (MS); severely affecting her mobility (WHO performance status 4) and quality of life. Other comorbidities included insulin-dependent diabetes mellitus and Crohn’s disease.

She was managed with an indwelling urethral catheter for the past 20 years but was never under urology review. For the last 18 months, her carers were experiencing difficulty in managing her catheters, such as pericatheter leaks and blockages requiring frequent catheter change. She was referred to urology in early 2021 for consideration of a suprapubic catheter (SPC). An urgent referral for general surgery review was also made by the general practitioner (GP) at the same time, for evaluation of per rectal bleeding and a possible rectal mass on digital rectal examination.

Investigations

A ultrasonogram (USG) was done for initial evaluation that demonstrated a 4.7 cm bladder stone (figure 1). There was right-sided hydronephrosis (HN) and an almost atrophic left kidney. The blood results showed a white blood cell count (WBC) of 9.2, haemoglobin of 117 g/L and the inflammatory marker, C reactive protein was 8 mg/L. Though the renal function was stable at the time of presentation with an estimated glomerular fraction rate of 73 mL/min and serum creatinine of 69 µmol/L;, the patient was deemed to be at risk high risk of losing the function of the solitary functioning right kidney as a complication of long-standing bladder stone.

In the meantime, the general surgery team requested a CT scan for evaluation of suspected rectal mass. The CT scan showed that the stone is actually in the vagina along with a few small calculi in the bladder (figure 2).

Since this was her first presentation at our institute, access to previous scans was difficult but was made possible after due diligence by our team and the consultant radiologist, finally scans dating back to 2010 could be successfully retrieved and reviewed. These scans were done for non-urological indications and the patient was never referred to urology in the past.

It was then concluded that her bladder stone was seen on the scans dating from 2010 to 2014 which then migrated into the vagina where it continued to grow in size (figure 3). This could be from pressure necrosis, leading to VVF. This fairly big size stone likely obstructed both ureteric orifices leading to an atrophic left kidney and right HN (figure 4).

The case was rediscussed in the endourology and pelvic floor multidisciplinary team meetings and the teams were in agreement that the upper tract dilation is most likely caused by the thick-walled bladder and extraluminal compression from the stone. There was no filling defect in the right ureter on delayed CT urogram images. A further discussion was held with the patient and her next of kin. Concerns surrounding the size of the vaginal stone were expressed to the family, with the acknowledgement that if left alone it could lead to a rectovaginal fistula due to ongoing pressure. Due to the fragility of the tissue, it was agreed that simultaneous VVF repair might not provide the best outcome.

Differential diagnosis

Bladder stones can cause frequent blockages and pericatheter leaks in patients with long-term catheters. Further evaluation with examination and imaging helped in reaching the diagnosis of an underlying VVF with a significant size bladder stone which was initially thought to be a rectal mass.

Treatment

On cystoscopy, the urethra was wide open due to long-term indwelling urethral catheter. VVF was found to be extending from the bladder neck up to the trigone and leading to the vagina posteriorly (figure 5). The bladder mucosa was assessed after blocking the VVF with the finger and appeared normal with no squamous metaplasia. Bladder capacity was less than 50 mL. On speculum examination, a large stone in the vagina was identified which was subsequently retrieved transvaginally with the use of cystolithotomy forceps (figure 6). The remaining small vesicle calculi were also removed. The patient was discharged home without a catheter with the advice of managing her urinary incontinence with continence pads.

Outcome and follow-up

At 4 week follow-up, the patient was recovering well. On examination, it was noted that the fistulous communication was still present, though has become slightly smaller in size. Further discussion was conducted in the outpatient clinic regarding the long-term management of the VVF. The pros and cons of surgical repair of fistula versus conservative management were discussed in detail. It was explained to the patient and her next of kin, that due to the quality of tissue and a very small capacity bladder, the chances of success are limited. It is quite likely that her VVF is acting as a safety net for her upper renal tract and hence closing the VVF may lead to compromise of her solitary kidney. In addition to this, the patient is bed-bound so even after VVF repair will need either long term catheter (LTC) or continence pads to manage her bladder.

On a balance, it was agreed to manage her VVF conservatively. On 6 monthly follow-up, the patient is keeping well and has stable renal function. She will be on annual surveillance with USS and renal function test, given her solitary functioning right kidney.