To the best of our knowledge, we present the first and most extensive cohort focused on acquired PFs. Managing PFs poses technical challenges due to anatomical complexities preceding complicating factors, such as tissue damage from radiation or ablation, infection, and concomitant neoplasia. Nevertheless, we described diagnostic possibilities and therapeutic strategies for addressing this complication following pelvic surgery for either prostate or colorectal diseases.

Uroenteric fistula can be caused by radiotherapy alone. The reported studies did not differentiate PF from RUF. Any type of radiation is currently related to around 50% of RUFs [1, 4]. The presumed pathophysiology associated with local irradiation across the rectal wall is microvascular injury due to local tissue hypoxia that causes mucosal damage and ischemia, leading to ulcers, perforations, and fistula formation. The estimated rate of RUF after external beam radiotherapy (EBRT) is about 1% and about 3% in the case of brachytherapy (BT) [4]. In a cohort of 51 patients treated for PCa at the Mayo Clinic, RUF incidence after EBRT, BT, and combined EBRT + BT was 30%, 30%, and 40%, respectively [7]. Following high-intensity focused ultrasound (HIFU) therapy, the rates of RUF are reported to be less than 3% after a single HIFU session for localized PCa [8]. Patients undergoing salvage HIFU therapy and repeated HIFU sessions have the highest overall risk for RUF, exceeding 5% [8]. Of the 471 patients treated with Irreversible Electroporation of the Prostate (IRE) and minimum follow-up for 4 months, Guenther et al. [9] reported a prostatic fistula in one patient (0.2%), which closed spontaneously after a few weeks.

In one case of our series, during colorectal resection for CRC, there was a prostatic injury, which developed a fistula, and the surgical repair was performed in 4 days. In the context of radical prostatectomy, rectal injuries are the main factor in the development of RUFs, with a correlation of up to 54% [4]. Overall, RUFs represent a relatively rare complication after prostatectomy, occurring in around 0.53% of cases [2, 4, 10].

In our study, the most relevant symptoms were fecaluria at 39%, rectal urine leakage at 31%, recurrent UTIs at 31%, pneumaturia at 23%, perineal pain at 15%, and dysuria at 15%. Compared to RUF characteristics, signs, and symptoms, fecaluria is present in about 43–65%, pneumaturia 67–85%, the leakage of urine through the rectum during micturition in about 40%, recurrent UTIs in 73%, abdominal pain 22%, and dysuria 15% [4]. The presence of fecaluria in an RUF is known to be a poor prognostic sign, indicating that the fistula may be significant in size [1, 6, 10].

The diagnosis of PF is based on history, physical examination, and imaging tests. Radiologic evaluation (CT scan and MRI) and diagnostic procedures (voiding cystourethrogram, retrograde urethrography, cystoscopy, colonoscopy) help us to delineate anatomy and identify concomitant colorectal, urethral, or bladder pathology. Urinary and fecal incontinence and function should be evaluated since they may affect subsequent treatment decisions. In our cohort, the combination of cystoscopy, retrograde urethrogram, and MRI serves as the gold standard imaging modality for diagnosing PF.

The conservative approaches used in our cohort included SPC, TUC, or PRP injection. Two (15.4%) patients observed spontaneous healing after conservative treatment with TUC or SPC. Although PRP injections failed to close the fistula, we observed a significant decrease in its size at the time of surgery compared to initial MRI data. Despite the majority of conservative management approaches failing, we believe that PRP injections or other healing-promoting factors may have a potential role. However, more data from larger trials are required to establish the efficacy of these agents in the management of these rare fistulas. Previous studies have demonstrated that conservative management of RUFs has a wide range of success rates, from 14 up to 100%, and it includes surgical procedures aimed to accomplish a urinary diversion (SPC, nephrostomy) or a fecal diversion (ileostomy or colostomy) [4]. If the RUF after prostatectomy is not closed after 3 months of catheterization, further treatment should be considered [3].

This study shows a cumulative fistula closure rate using conservative or surgical treatment of 92.3%. A meta-analysis on RUF, including 416 patients in 26 studies, showed an overall healing rate of 88%, with an overall permanent fecal or urinary diversion rate slightly higher than 20% [6]. In the case of simple classic RUF, a 3-month waiting period before surgery to give time for the lesion to spontaneously close is recommended [4]. In the complex RUFs, the interval should be increased up to 6 months to improve tissue quality. In fecal diversion, these should be closed during the first 3 months.

One crucial point regarding the surgical repair of RUFs is to distinguish and classify RUFs into simple and complex. All of the following are characteristics of RUF complexity: size larger than 2 cm, urethral stricture, bladder neck necrosis, or ischemic damage associated with ablative energies. On the other hand, a fistula is considered simple when it is secondary to surgical trauma on a previous healthy tissue [4]. In two of our patients, following the failure of conservative therapy with PRP injection and unsuccessful repair solely with prostatectomy, a second intervention for PF repair was necessary. Based on the classification of RUFs, these were categorized as complex PFs resulting from preoperative radiation for CRC.

Similar to the management of complex vesicovaginal fistulas after radiotherapy, secondary revision surgery is sometimes necessary to achieve closure [11]. We should counsel our patients that although this complication is formidable, there is a chance for cure, especially in tertiary centers specialized in reconstructive pelvic surgery. Initially, most cases required definitive urinary or fecal diversion. However, as our management strategies evolved and became more nuanced, we have achieved cure rates exceeding 80%, even in complex cases involving prior radiation therapy.

There are up to 40 different surgical approaches described to treat RUFs, including open abdominal as well as laparoscopic and robot-assisted surgery, trans-perineal, trans-anal (Parks, Latzko), trans-sphincteric (York-Mason), trans-sacral, and combined approaches [2, 4, 6]. While the principles of fistula excision remain consistent, repairing iatrogenic PF represents a unique challenge due to the involvement of the rectal cavity, prostatic gland, and prostatic urethra. Any closure attempt should consider prostate removal, which can be particularly challenging in cases involving PCa, previous radiotherapy for rectal/anal cancer, or other cancer-related treatments that may alter the normal pelvic anatomy. The transabdominal approach allows primary fistula repair or en bloc fistula removal via cysto-/prostatectomy or anterior exenteration. In experienced hands, the trans-perineal approach has some of the highest closure rates, at 91%. However, these cure rates have been reported following prostatectomy [6]. Alternatively, a trans-sphincteric approach can be considered, but generally only in non-irradiated patients, with closure rates of 85–88%, and it is usually used in non-radiated patients. In our cohort, due to the increased number of patients with various procedures for rectal/anal cancer, these procedures were considered oncologically unsafe.

In complex RUFs, the use of interposition flaps is recommended. The different flaps used are gracilis muscle, omentum, rectus muscle, gluteus maximus muscle, and dartos, with the most commonly used muscle being the gracilis (95% of cases). The gracilis flap can be an ideal tissue transfer candidate as it provides robust, well-vascularized tissue that can be interposed at the target side [4, 6]. In our cohort, flaps were used in only 4 (31%) cases, but considering the high cure rate, we do not consider this a limitation of our study. However, we recommend the usage of flaps in all cases with uro-enteric fistulas if it’s technically feasible.

Despite reporting the first series of acquired PF, this study was limited by its retrospective nature, the heterogeneity of the study population, and the limited number of patients. Patient follow-up was variable among investigators. Given the low rate of prostatic fistulas and the non-uniformity of these cases, a prospective analysis of operative management was not feasible. Also, an evaluation of urinary continence following fistula repair was not performed due to the heterogeneity of the study group. The majority of patients presented a temporary urinary diversion before surgery, and a preoperative evaluation of the urinary continence could not have been performed in a standardized fashion using questionnaires.