A Rare Cause of Ascites: Vesicoabdominal Fistula as a Late Complication of Radiation-Induced Cystitis – A Case Report Open Access

The differential diagnosis of ascites includes a wide range of conditions. The most common causes are liver cirrhosis with portal hypertension, heart failure, inflammatory conditions (e.g., acute pancreatitis), and cancer, especially with peritoneal involvement. Diagnosis is typically based on clinical presentation and imaging methods (e.g., ultrasound, abdominal computed tomography [CT] scan, or magnetic resonance imaging [MRI]). The nature of ascites can be determined by obtaining the fluid through puncture, followed by biochemical and cytological analysis. Vesico-peritoneal fistula (VPF) is an extremely rare condition. Most of the papers published to date describe VPF as an early postoperative complication of urogenital surgery. Other reported etiologies include fistulation associated with abscess formation or resulting from postradiation changes [1‒3]. The treatment is usually conservative, but in certain cases, surgery may be a possible alternative.

The mechanism of postradiation damage is not well understood; it includes injury to the urothelium, blood vessels, and smooth muscle. The disruption of tight junctions and the polysaccharide layer, along with cellular damage, leads to decreased resistance of the bladder wall against hypertonic urine, resulting in an inflammatory reaction. Bladder fibrosis is thought to develop secondary to vascular ischemia of the bladder wall. Vascular ischemia, edema, and cellular destruction lead to the replacement of bladder smooth muscle fibers by fibroblasts, resulting in increased collagen deposition and a subsequent reduction in bladder compliance and capacity, with a risk of fistula formation [4].

The symptoms of a late-onset VPFs differ from the acute postoperative VPFs in several ways. Late-onset VPFs are often harder to diagnose due to their slow progression and nonspecific symptoms, which may lead to delays in treatment. Diagnosis may only occur when other potential causes of chronic abdominal symptoms are ruled out.

Unlike the immediate postoperative pain, late-onset symptoms often manifest as persistent or intermittent abdominal discomfort and chronic bloating. The pain may be dull and difficult to localize, becoming more pronounced after voiding or prolonged sitting. While early onset fistulas may present with acute urinary tract infections, late presentations often involve recurrent or persistent urinary tract infections that are difficult to treat, as the abnormal urinary flow into the peritoneum can lead to chronic bacterial colonization. In long-standing cases, the continuous leakage of urine into the peritoneal cavity can lead to fluid and electrolyte imbalances, causing malabsorption, weight loss, and potentially malnutrition, especially if the fistula interferes with bowel function. In contrast to the acute peritonitis seen early after the fistula formation, late symptoms may present as chronic peritoneal irritation with low-grade inflammation, causing vague discomfort rather than overt signs of infection or peritonitis.

A 71-year-old female patient, who had undergone hysterectomy, adnexectomy, and chemoradiotherapy for carcinoma of the uterus in 1990, was referred to our hospital in 2023 with ascites, lower abdominal pain, oliguria, and extreme elevation of renal parameters (urea: 18.3 mmol/L, creatinine: 625 µmol/L or 7.07 mg/dL). Abdominal ultrasound revealed no obstruction of the urinary tract or renal or liver pathology related to the ascites. After initial diuretic treatment and insertion of a urinary catheter, the ascites and renal parameters partially resolved.

A subsequent CT scan suggested the presence of peritoneal carcinomatosis and recurrence of uterine cancer (shown Fig. 1, 2). An open laparoscopy with peritoneal biopsy and ascites evacuation was performed. During the surgery, no signs of malignancy were observed, and histological findings were negative. However, macroscopically, severe postradiation colitis of the rectum and sigmoid colon was observed. Biochemical analysis of the ascites revealed high levels of creatinine and urea (urea: 10.7 mmol/L, creatinine: 201 µmol/L). The nature of the ascites and the course of the disease suggested a possible communication between the urogenital tract and the peritoneal cavity.

A cystoscopy was performed, revealing postradiation cystitis but no signs of fistulization. Due to the ongoing clinical suspicion of communication between urinary bladder and peritoneal cavity, a MRI of the small pelvis was performed, which also showed negative result. Finally, retrograde cystography demonstrated a leak of iodine contrast into the peritoneal cavity through a thin fistula at the apex of the urinary bladder (shown in Fig. 3). Given the previously reported rapid improvement of symptoms after urinary catheter insertion, we decided to insert a permanent urinary catheter.

The insertion of the permanent urinary catheter led to rapid improvement in renal function, resolution of abdominal pain, and regression of ascites. After 6 weeks, the catheter was removed, and no signs of recurrence of the communication were noted during follow-up.

The data on the management of VPF in the context of chronic postradiation damage to the urinary bladder are extremely limited and consist primarily of several case reports. It can therefore be considered a rare condition, as suggested by the study of Donnez et al. [1], based on follow-up data from patients after surgery.

The diagnosis is challenging, as ascites is an uncommon condition in patients who have undergone surgery and chemoradiotherapy of the urogenital tract [1]. Confirming the leak is also difficult, as demonstrated in our case report.

Suspicion of VPF should arise from the high concentration of urea and creatinine in the ascites, combined with elevated renal parameters in the serum in the setting of normal kidney function. This so-called pseudo-renal failure is caused by the reabsorption of urea and creatinine across the peritoneal layer.

The CT of the abdomen with iodine-based contrast, CT urography, and MRI proved to be suboptimal imaging modalities for the detection of this subtle anomaly. Contrast-enhanced CT did not provide sufficient resolution to visualize the small fistula. Although MRI is generally well-suited for soft tissue evaluation, it similarly failed to identify any pathological communication. The CT urography, in contrast to the retrograde cystography, did not generate sufficient intravesical pressure to permit contrast leak through the narrow fistula.

While several authors advocate cystoscopy as the primary diagnostic tool, in our case, the fistula was not visualized via this modality [5]. The principal advantage of cystoscopy lies in its dual diagnostic and therapeutic potential, particularly in facilitating fistula treatment or biopsy acquisition when malignancy is suspected.

Peng et al. [6] have suggested that CT cystography may serve as a viable alternative to conventional retrograde cystography in selected clinical contexts. However, Ma et al. [7] reported that CT cystography may be inferior to X-ray-based retrograde cystography due to the potential for incomplete bladder filling during CT protocols. Considering these findings, we propose conventional retrograde cystography as the most reliable imaging modality for the diagnosis of delayed bladder fistula.

Treatment options include minimally invasive laparoscopy or conservative treatment [1, 2]. In our patient, due to postradiation changes in the urinary bladder, which could complicate the surgery and impair healing, conservative treatment was chosen. The permanent urinary catheter was inserted and left in place for 6 weeks. Follow-up cystography did not show any leaks. The patient has been asymptomatic for over a year, as of the last follow-up in April 2025. This modality of the treatment seems to be the optimal first choice of treatment for patients with VPF due to postoperative damage [1], and the only solution for patients contraindicated for surgery. When there is no response to conservative treatment, minimally invasive surgery such as laparoscopic repair is strongly recommended for VPF [2].

In cases of early onset VPFs, surgical intervention is the primary treatment. The approach typically involves laparoscopic or open surgical repair to close the fistula and restore normal bladder function. Laparoscopic techniques are preferred due to their minimally invasive nature, leading to shorter recovery times and reduced complication rates. For late-onset VPFs, management may be more complex. Surgical repair remains the treatment of choice; however, the procedure may be more challenging due to the presence of adhesions and altered anatomy. In some cases, a staged approach involving initial drainage and subsequent definitive repair may be necessary.

With appropriate surgical intervention, the prognosis for patients with VPF is generally favorable. Most individuals experience resolution of symptoms and a return to normal bladder function. However, long-term follow-up is recommended to ensure the continued success of the repair and to address any potential complications promptly. We hope that the case we present will contribute to a quicker diagnosis of VPF, particularly in patients with unexplained ascites, elevated renal parameters, and no apparent renal pathology, especially those with a history of pelvic surgery or radiation.

The CARE Checklist has been completed by the authors for this case report, attached as online supplementary material (for all online suppl. material, see https://doi.org/10.1159/000546596).

Written informed consent was obtained from the patient for publication of this case report and any accompanying images. Ethical approval was not required for this study in accordance with local and national guidelines.

The authors have no conflicts of interest to declare.

This study was supported by a grant DRO–VFN00064165 given by the Ministry of Health of the Czech Republic.

Jakub Klevar and Pavel Hrabák were the patient’s attending physician and drafted the original manuscript, contributed to writing – review and edition. Libor Zámečník is consulting urologist and review the paper. Radan Brůha supervised and reviewed the manuscript.

All data generated or analyzed during this review are included in this paper and its online supplementary material files. Further inquiries can be directed to the corresponding author.