Capsaicin-Triggered Vaginal Burning Due to Obstructed Rectovaginal Fistula: A Rare Case of Perineal Coproliths

Introduction

Rectovaginal fistulas (RVFs) commonly present with symptoms such as passage of gas, mucus, or fecal matter through the vagina, often accompanied by malodor or recurrent vaginitis. These typical features generally facilitate early recognition and prompt surgical referral [1]. However, atypical or occult presentations are rarely reported and can result in misdiagnosis or delayed management. We report an occult RVF presenting with a highly atypical symptom – isolated vaginal burning triggered exclusively by spicy food ingestion – without any flatus or fecal leakage, ultimately attributed to capsaicin transit through a low intersphincteric fistulous tract obstructed by perineal coproliths (fecaliths). Our case also reinforces the importance of timely and appropriate surgical management [2]. The distinct symptom profile, combined with imaging findings, underscores the diagnostic challenge and highlights the need to consider RVF even in the absence of classic manifestations.

A literature review reveals few, if any, documented cases of diet-induced vaginal burning as the sole manifestation of RVF, and to the best of our knowledge, no previous report has described capsaicin-related symptomatology linked to a fistulous tract. Additionally, while coproliths have been sporadically reported in the rectum or sigmoid colon [3,4], their formation within a fistula tract and role in obstructing classical symptoms of RVF is exceptionally rare.

Clinically, this case highlights 2 practical implications: first, clinicians encountering unexplained, food-triggered vaginal irritation should consider targeted pelvic imaging (eg, pelvic magnetic resonance imaging [MRI] and endoanal/perineal ultrasound) to evaluate for occult fistulous disease; second, a staged, individualized management strategy – beginning with removal of obstruction and seton drainage, with delayed definitive repair or diversion if necessary – may be the most appropriate approach for selected low-level, inflamed, or obstructed RVFs. This case highlights the need for heightened clinical suspicion in post-surgical pelvic patients with unexplained pelvic discomfort.

Case Report

A 52-year-old female patient developed a burning sensation in the vagina, which she described as resembling chili water 2 years ago after consuming spicy food, but the symptom did not occur with a bland diet. The patient underwent vaginal colposcopy and gynecological ultrasound examination at the local hospital, but no abnormalities were found. Three months before presenting to our facility, after experiencing diarrhea, the patient’s vaginal burning sensation worsened. The patient suspected it might be caused by vaginitis, so she purchased azithromycin for oral administration. However, the symptoms did not alleviate, and the patient could only relieve the symptoms by consuming bland food.

This patient underwent unilateral oophorectomy 15 years before presentation due to a diagnosed “ovarian cyst”; perineal surgery was performed 10 years before presentation due to perineal injury during childbirth; left breast cancer resection was performed 8 years before presentation due to diagnosed breast cancer; postoperative pathology revealed invasive carcinoma of the left breast, and the patient subsequently received regular chemotherapy. The patient entered menopause 3 years before presentation, with no other significant past medical or personal history, and denied any family history of hereditary diseases.

Two colorectal specialists conducted a detailed physical examination of the patient: a subcutaneous lump measuring approximately 2×2 cm with a hard texture and clear boundaries was found in the perineal body (Figure 1). Subsequent ultrasound examination revealed hyperechoic subcutaneous tissue in the perineum, suggestive of calcification (Figure 2). Pelvic contrast-enhanced MRI indicated a low-level inter-sphincteric fistula according to the Parks classification (Figure 3). Blood tests, coagulation tests, infection markers (syphilis, HIV, hepatitis B, hepatitis C), routine stool tests, gastrointestinal tumor markers, gastroscopy, colonoscopy, chest computed tomography, and other examinations showed no abnormalities; however, a urine routine test indicated 36.7 red blood cells/μL. Given the atypical symptom of vaginal burning without evident vaginal discharge or flatus, the initial differential diagnosis included (1) recurrent vaginitis or contact dermatitis, particularly triggered by dietary irritants such as capsaicin; (2) vulvodynia or estrogen deficiency–related mucosal hypersensitivity, especially considering the patient’s postmenopausal status; and (3) perineal epidermal inclusion cyst or calcified scar tissue, given the firm subcutaneous mass in the perineal body and history of prior perineal trauma. However, the presence of a persistent perineal mass with calcification on ultrasound, combined with a low intersphincteric fistula tract identified by pelvic MRI, raised suspicion for a chronic fistulous process. While no overt signs of RVF were observed, the combination of imaging findings and recurrent vaginal burning after spicy meals prompted consideration of an occult RVF partially obstructed by coproliths. The differential diagnoses were excluded as follows. The absence of vulvovaginal inflammation on colposcopy, absence of discharge, and lack of response to empirical oral antibiotics excluded recurrent vaginitis/contact dermatitis; episodic and food-related rather than persistent symptoms and examination lacking atrophic mucosal changes excluded vulvodynia/postmenopausal mucosal sensitivity; and imaging revealing a tract with intratract calcification and intraoperative communication with the rectum and vagina, consistent with a fistulous process rather than an isolated cyst, excluded epidermal inclusion cyst/calcified scar.

The patient underwent surgical exploration under general anesthesia. An arc-shaped incision approximately 1.8 cm in length was made in the perineum, 1.5 cm anterior to the anal verge. Using blunt dissection with tissue forceps, the skin, fascia, and partial muscle layers were separated along the incision. A probe inserted through the incision traced a fistulous tract extending approximately 2 cm toward the left anterior perineum.

Along the path of the probe, the overlying skin was incised, exposing a cavity approximately 2 cm in size located within the rectovaginal septum. The cavity was filled with multiple firm coproliths and fragments of cyst wall–like fibrotic tissue (Figure 4). These were carefully removed. Further probing along the same tract revealed communication with the posterior vaginal wall, where the probe emerged from an internal opening approximately 2 cm proximal to the vaginal introitus.

Under direct guidance, a loose seton (rubber band) was placed through the fistula tract to maintain drainage and prevent premature closure. The incision margins were debrided to ensure unobstructed drainage (Figure 5A). Given the typical gross appearance of the coproliths and the absence of suspicious tissue, no specimen was submitted for pathological analysis. No primary closure or flap repair was performed. During postoperative management, the patient received a 5 to 7 day course of prophylactic antibiotics, regular wound care with dressing changes, and instructions for seton care and perineal hygiene.

She was discharged 1 week after surgery in stable condition (Figure 5B). A telephone follow-up at 2 weeks revealed complete resolution of vaginal burning. At 1-year follow-up, the patient reported no recurrence of symptoms, with normal defecation and urination, and no other discomfort. Given the patient’s full clinical recovery and the high cost of pelvic MRI, follow-up imaging was not pursued. No recurrence or residual symptoms were reported at 1 year.

Discussion

RVFs are typically characterized by continuous or intermittent passage of gas or feces through the vagina, often resulting from obstetric trauma, surgery, inflammatory bowel disease, or radiation [5,6]. However, the patient in this case presented with a highly atypical symptom profile, most notably the absence of vaginal discharge and the presence of a burning sensation triggered exclusively by spicy food consumption. These atypical manifestations contributed to a delay in diagnosis and initial misdiagnosis as vaginitis, a factor known to be associated with less favorable outcomes when surgical repair is postponed [7]. In this case, the clinical presentation was atypically masked due to obstruction of the fistula tract by coproliths. Perineal coprolith formation is rarely reported in the literature, particularly in association with RVF. A literature search yielded only sparse case reports describing coproliths forming within fistulous tracts or obstructing perineal abscesses [8], and, to the best of our knowledge, none have involved an occult RVF masked by such stones. A focused PubMed search (keywords: “rectovaginal fistula” AND “coprolith” OR “fecalith” OR “perineal fecalith”) yielded no prior reports of diet-triggered vaginal burning in association with an occult RVF obstructed by coproliths.

Moreover, the symptomatology in this patient was uniquely diet-triggered. The patient reported vaginal burning consistently triggered by spicy foods. We hypothesize that this reproducible, food-triggered burning sensation reflects trans-fistulous capsaicin exposure within a partially obstructed tract [9], as our patient consistently experienced burning vaginal sensations following ingestion of chili-containing food. While capsaicin is known to cause mucosal irritation, its role in revealing occult fistulas has not been described. This phenomenon may represent a form of “chemosensory signaling” across compromised epithelial barriers, wherein dietary molecules with neuroactive properties – such as capsaicin – exacerbate local inflammation or sensory input along aberrant tissue communications [10]. The presence of this reproducible, food-triggered symptom pattern could serve as a valuable diagnostic clue in future cases, prompting consideration of fistulous disease even in the absence of fecal soiling.

The co-existence of fistula and coprolith obstruction poses unique diagnostic and therapeutic challenges. Imaging studies such as MRI and endoanal ultrasonography were instrumental in this case for delineating the tract and identifying calcified material [11]. It is noteworthy that standard gynecological evaluation alone, including vaginal colposcopy and transvaginal ultrasound, failed to detect the pathology, which underscores the importance of cross-specialty imaging in persistent, unexplained perineal symptoms [12]. Clinicians should be aware that deep pelvic fistulas, particularly those not involving high-output drainage, may only become apparent through advanced imaging or surgical exploration. Clinically, this highlights the importance of comprehensive imaging when symptoms suggest a deep-seated perineal or vaginal pathology without external discharge.

From a surgical perspective, the use of a seton after removal of the obstructive coproliths allowed for controlled drainage and healing of the fistulous tract. This case suggests that a staged surgical approach can benefit patients with partially obstructed RVFs. Previous studies, including reports of medicated seton (Kshar Sutra) use in low RVF repair, have demonstrated favorable outcomes even in resource-limited settings, supporting the efficacy of staged, seton-based management when local inflammation or tissue compromise is present [13]. Seton placement in RVF, while more commonly used in Crohn disease–associated fistulas, has also been shown to be effective in non-inflammatory etiologies when the tissue is inflamed or infected, delaying definitive repair until local conditions improve [14]. For patients with chronic fistula symptoms obscured by dietary or anatomical modifiers, a tailored diagnostic and therapeutic pathway may be warranted. This case also supports recent literature suggesting that aggressive, individualized surgical intervention – including early consideration of protective stoma or staged repair in anatomically complex or recurrent RVFs – may optimize outcomes and reduce recurrence [15].

This report describes a single case and lacks objective postoperative imaging; the 1-year clinical outcome was based on patient report via telephone follow-up. Despite these limitations, this case highlights that in patients presenting with food-triggered vaginal burning without gas or stool leakage, occult RVF masked by coproliths should be considered. Targeted cross-specialty imaging such as MRI or endoanal ultrasound may improve early recognition. Further cases or larger series are needed to determine whether such diet-triggered symptomatology can reliably indicate coprolith-obstructed RVF and to refine diagnostic and staged management strategies.

Conclusions

This case suggests that diet-triggered vaginal burning without gas or stool leakage can indicate an occult RVF masked by coproliths. Clinicians should maintain a high index of suspicion in patients with prior pelvic surgery and pursue targeted evaluation using pelvic MRI and transperineal ultrasound when symptoms correlate with food irritants. Staged management with loose seton placement can be an effective option in selected low-level fistulas while definitive healing is awaited.