Radiotherapy-Related Bladder Fistula: A Hidden Cause of Recurrent Abdominal Symptoms

Introduction

Acute ascites is a critical condition in the gastroenterology department and are usually accompanied by significant peritoneal irritation and circulatory failure. Bladder rupture has been recognized as a rare and insidious cause of acute ascites, with a high mortality rate of approximately 25% [1]. We present an unusual case of vesical fistula with recurrent urinary ascites for over 1 year, with multiple hospitalizations. While vesical fistula secondary to radiation therapy following gynecological surgery has been documented [2], its clinical presentation can be nonspecific. Patients may initially present with a spectrum of symptoms, including ascites, acute abdominal pain, oliguria, and hematuria [3–5], leading to misdiagnosis as gastrointestinal diseases.

Case Report

A 60-year-old woman presented with a 1-year history of intermittent abdominal pain, which had acutely worsened over the preceding day. The abdominal pain, localized to the lower abdomen and exacerbated by straining during urination, was accompanied with a rapid increase in abdominal girth and decreased urine output. She reported no fever, chills, nausea, vomiting, hematuria, dyspnea, or lower-limb edema.

Her medical history included a pattern of abdominal pain lasting from hours to days, recurring every 10–15 days, accompanied by oliguria, increased abdominal circumference, and diarrhea since 2021. Prior to this visit (March 2024), she had been hospitalized 3 times for abdominal pain: in July 2022, March 2023, and June 2023. Hydroperitoneum was confirmed with each episode but was relieved within 2 days by self-administered belladonna tablets and cephalosporins. However, the cause of ascites remained unknown. Her medical history included a hysterectomy and bilateral adnexectomy for cervical carcinoma in 2009, followed by radiotherapy until 2010. In 2020, she was admitted to a hospital with hematuria due to radiation cystitis and was managed with blood transfusion and cystoscopic mucosal electrocautery.

On examination, she had stable vital signs (temperature: 36.2°C, pulse rate: 92 beats per minute, blood pressure: 134/86 mmHg, and respiratory rate: 20 breaths per minute). Bloating, diffused rebound tenderness, and shifting dullness were noted. The rest of the physical examination was unremarkable.

Laboratory tests indicated blood neutrophil count (7.72×109/L, reference: 1.8–6.3×109/L), blood urea nitrogen (14.01 mmol/L, reference: 3.10–8.80 mmol/L), blood creatinine (242 μmol/L, reference: 41.0–111.0 μmol/L), serum uric acid (436 μmol/L, reference: 178–416 μmol/L), and erythrocyte sedimentation rate (ESR 66 mm/h, reference: 0–20 mm/h). PT/APTT, serum electrolytes, and serum proteins were within normal range. Hepatitis virus serology tests were negative. Tumor markers, ascites antacid bacillus, and serum Mycobacterium tuberculosis IgG antibody were negative. Abdominal computed tomography (CT) revealed extraordinary ascites, a thickened and roughened bladder wall (Figure 1A–1D), and post-hysterectomy changes. The ascites was also confirmed by ultrasound. No abnormalities were found in cardiac and liver examinations.

After admission, the patient underwent peritoneal puncture. Ascites drainage immediately yielded approximately 1000 ml. The ascites test revealed an elevated creatinine level (938.0 μmol/L, reference: 41.0–111.0 μmol/L), urea nitrogen (25.22 mmol/L, reference: 3.10–8.80 mmol/L), with leukocytes 220×106/L, chloride 115.8 mmol/L, and protein 4.1 g/L. Due to significantly elevated creatinine and urea nitrogen in the ascitic fluid compared to the blood, a preliminary diagnosis of urinary ascites was proposed.

Further tests, such as ascites Rivalta test, acid-fast bacillus staining smear, and bacterial culture, were negative. Hematuria, proteinuria, hypertension, and lower-limb edema were not observed in the past 3 months, ruling out acute kidney injury. Vesical fistula was finally confirmed after abdominal drainage of blue ascitic fluid (Figure 2) following instilling 500 ml of saline-methylene blue solution through the urinary catheter (Figure 2). Then, together with the radiologist, we reviewed the abdominal CT and found a discontinuity of the bladder wall in the coronal view (Figure 1D), indicating a bladder fistula.

The urologists suggested that radiotherapy-induced fibrosis may have resulted in indurated bladder tissue with poor vascularity, which would make surgical repair highly challenging and increase the likelihood of postoperative recurrence. The patient strongly refused cystoscopy, opting for conservative management with antibiotics, urinary catheterization, and abdominal drainage instead. Within 48 hours, she had significantly decreased abdominal drainage, increased urine output, and alleviation of abdominal pain. The abdominal drain was removed 3 days later. She was discharged with a retained urinary catheter, which remained in place for 3 months, without reported discomfort at follow-up.

Discussion

The etiology of non-traumatic bladder rupture is diverse, and is often related to malignancy, pelvic radiotherapy, neurogenic bladder dysfunction, bladder inflammation or infection, bladder outflow tract obstruction, alcoholism, female pelvic organ prolapses, and rare congenital or acquired bladder diverticulum rupture [1]. In this patient, vesical fistula likely developed as a late complication of radiotherapy or cystoscopic electrocautery, given her history of radiation therapy, gynecological surgery, and hematuria with cystoscopic treatment. However, the possibility of a bladder tumor could not be definitively excluded based on current evidence. The patient declined further examination, but follow-up after discharge revealed no indications of bladder tumors.

The diagnosis of vesical fistula is challenging due to its diverse presentations and the possibility of being overlooked by CT [6,7]. In addition, urinary ascites often presents as an emergency requiring immediate catheterization, anti-infective treatment, or surgery. It is rare for a patient to have vesicle fistula with intermittent remission of abdominal pain, ascites, and oliguria for over 1 year. Markedly elevated creatinine and urea nitrogen levels in the ascites requires a high index of suspicion for urinary system-related ascites, particularly in patients with a history of pelvic irradiation.

Our patient’s prolonged stability with intermittent symptoms of abdominal pain after each push-to-urinate suggests a unidirectional mechanism, possibly analogous to a flap valve, where abdominal pressure typically exceeds bladder pressure, minimizing urine leakage (Figure 3). The strain during urination could reverse this pressure differential, facilitating urine flow into the peritoneal cavity (Figure 3). The relief of ascites and abdominal pain may also be related to the cessation of urinary fistula due to bowel compression and increased abdominal pressure. The location of the fistula corresponded with her symptoms, but it remains unclear, as the patient refused further invasive investigations.

Laboratory findings in patients with urinary ascites can mimic acute renal failure, where the creatinine level is elevated due to peritoneal reabsorption rather than due to impaired kidney function [8,9]. The similarity of urinary ascites to other gastrointestinal disorders often misdirects clinicians towards managing acute renal failure and peritonitis instead of identifying a bladder rupture [4]. Heyns et al [10] reported that the ratio of ascites creatinine to serum creatinine rises to 5: 1 in patients with bladder rupture after 24 hours. Ascites creatinine testing was crucial in the differential diagnosis of this case, with an ascites-to-serum creatinine ratio of 4: 1 (938 umol/L vs 242 umol/L), aligning with the previous report [10].

Throughout her medical journey, the patient underwent multiple rounds of routine and biochemical ascites tests, along with a comprehensive set of imaging and laboratory assessments to evaluate the function of her heart, liver, and kidneys, and to assess for cancer, which are all parts of a thorough differential diagnosis. However, oversight of consistently elevated ascites creatinine levels may have occurred, underscoring the significance of basic diagnostic methods. Indeed, amidst the proliferation of advanced medical technologies, there is a growing concern that basic clinical skills and routine examinations might be inadvertently neglected in clinical practice. One of the key takeaways from this case is the necessity to maintain a balanced approach to patient evaluation – one that integrates both advanced and basic diagnostic methods.

Conclusions

Due to the increased risk of re-perforation, conservative management with antibiotics and prolonged drainage is often recommended for patients with a history of pelvic irradiation [1]. Clinicians should consider vesical fistula in the differential diagnosis for unexplained ascites and peritonitis, particularly in cases with medical history of cystoscopic treatment, abdominopelvic surgery, or radiotherapy.