Elucidating vaginal fistulas on CT and MRI.

Vaginal fistulas are broadly categorised as they affect either the distal bowel (sigmoid colon, rectus, anal canal) or urinary tract (bladder, distal ureter or urethra) Among the spectrum of causes, in Western countries, iatrogenic surgical injuries represent an increasing concern CT diagnosis of bowel vaginal fistulas benefits from small field-of-view oblique and sagittal interpretation, and optional intrarectal contrast If not contraindicated, focused MRI provides superior visualisation of ano- and rectovaginal fistulas CT-urography and additional CT-cystography now represent the mainstay techniques to diagnose urinary VF Vaginal fistulas are broadly categorised as they affect either the distal bowel (sigmoid colon, rectus, anal canal) or urinary tract (bladder, distal ureter or urethra) Among the spectrum of causes, in Western countries, iatrogenic surgical injuries represent an increasing concern CT diagnosis of bowel vaginal fistulas benefits from small field-of-view oblique and sagittal interpretation, and optional intrarectal contrast If not contraindicated, focused MRI provides superior visualisation of ano- and rectovaginal fistulas CT-urography and additional CT-cystography now represent the mainstay techniques to diagnose urinary VF

Although lacking an accepted classification scheme or standardised terminology, VF may be broadly separated into either entero- or urinary VF according to involvement of the distal bowel or lower urinary tract, respectively. Both categories are further subdivided on the basis of the target organ [ 2 , 10 ]. Entero-VF (Fig.  1 ) may involve the sigmoid colon (colo-VF), rectum (recto-VF) or anus (ano-VF). Their underlying causes and mechanisms are summarised in Table  1 [ 1 , 5 , 11 ]. Fig. 1 Schematic representation of entero-vaginal fistulas (VF). a colo-VF (CVF). b recto-VF (RVF) and ano-VF (AVF). Note absent uterus in ( a ). Vagina indicated by asterisk (*), urine in yellow, stools in brown Table 1 Categorisation, causes and mechanisms of entero-vaginal fistulas Type Cause Notes Colovaginal Complicated colonic diverticulitis Patients with prior hysterectomy Either (a) inflamed sigmoid colon directly adheres to the vaginal vault or (b) via formation of interposed abscess that opens in the vagina Rectovaginal Past irradiation such as for uterine cervix carcinoma Delayed onset (years after treatment) Increasingly uncommon Primary or recurrent pelvic tumours Either (a) rectal carcinoma invading the vagina or (b) gynaecologic malignancies invading the rectum Surgical injury   - Low anterior resection for rectal cancer Risk up to 5–10% of patients, part of anastomotic leakage spectrum Inadvertent clipping of vagina in staples   - Pelvic floor surgery With positioning of prosthetic mesh   - Haemorrhoid surgery Anovaginal Crohn’s disease (CD) CD = 25% of all vaginal fistulas (VF) VF < 4–9% of all CD-related perianal inflammatory disease Often complex forms Ulcerative colitis Perianal inflammatory disease (rare) Ileal pouch-anal anastomosis leakage Cryptoglandular or other inflammation E.g. Bartholin’s gland abscess Perineal laceration From either (a) direct trauma (often sexual violence) or (b) obstetric injury (spontaneous or instrumental delivery) Schematic representation of entero-vaginal fistulas (VF). a colo-VF (CVF). b recto-VF (RVF) and ano-VF (AVF). Note absent uterus in ( a ). Vagina indicated by asterisk (*), urine in yellow, stools in brown Categorisation, causes and mechanisms of entero-vaginal fistulas Patients with prior hysterectomy Either (a) inflamed sigmoid colon directly adheres to the vaginal vault or (b) via formation of interposed abscess that opens in the vagina Risk up to 5–10% of patients, part of anastomotic leakage spectrum Inadvertent clipping of vagina in staples CD = 25% of all vaginal fistulas (VF) VF < 4–9% of all CD-related perianal inflammatory disease Often complex forms Perianal inflammatory disease (rare) Ileal pouch-anal anastomosis leakage In developing countries, VF are still common and almost invariably secondary to obstructed labour [ 4 , 12 ]. Conversely, despite advancements in open and laparoscopic surgical techniques, in the Western world, over 90% of all urinary VF (Fig.  2 , Table  2 ) now develop as iatrogenic complications of irradiation or surgical injury to either distal ureter or bladder. However, a post-surgical VF is rather uncommon (2% of cases) compared with bladder (60–70%) and ureteral (24–30% of cases) injuries without vaginal involvement [ 13 – 16 ]. Fig. 2 Schematic representation of urinary VF. a uretero-VF (CVF). b vesico-VF (VVF) and urethro-VF. Note absent uterus in ( a ). Vagina indicated by asterisk (*), urine in yellow, stools in brown Table 2 Categorisation, causes and mechanisms of urinary vaginal fistulas Type Cause Notes Ureterovaginal Surgical injury Intraoperative injury to the distal ureter Risk further increased by parametrial and nodal dissection Often via formation of urinoma that drains into the vaginal vault   - Most frequent (75% of cases): total abdominal or radical hysterectomy   - Less common procedures: laparoscopic treatment of endometriosis, surgery for ovarian cancer, complex urological or lower gastrointestinal pelvic surgeries Vesicovaginal + urethrovaginal Surgical injury Intraoperative injury to urinary bladder Often with formation of urinoma that drains into the vaginal vault Sometimes via necrosis of vaginal vault from incorrectly placed sutures between the vaginal cuff and posterior aspect of bladder   - Same interventions as above plus   - Emergency caesarean section   - Anti-incontinence procedures, cystocele repair, resection of urethral diverticulum Locally advanced malignancies Rare, e.g. uterine cervix carcinomas, urethral/bladder transitional carcinomas Past irradiation such as for uterine cervix carcinoma Delayed onset (years after treatment) Increasingly uncommon Perineal laceration From direct trauma (most usually sexual violence) Obstetric complication (spontaneous or instrumental delivery) Historical, still today in developing countries lacking obstetric practices Via pressure necrosis of the anterior vaginal wall and bladder neck, compressed between the foetal head and the symphysis pubis Schematic representation of urinary VF. a uretero-VF (CVF). b vesico-VF (VVF) and urethro-VF. Note absent uterus in ( a ). Vagina indicated by asterisk (*), urine in yellow, stools in brown Categorisation, causes and mechanisms of urinary vaginal fistulas Intraoperative injury to the distal ureter Risk further increased by parametrial and nodal dissection Often via formation of urinoma that drains into the vaginal vault Regardless of type, all VF cause distressing symptoms including persistent vaginitis despite treatment, dyspareunia, painful perineal dermatitis and excoriation. Entero-VF are heralded by foul-smelling enteral or faecal discharge through the vagina. Faecal incontinence may develop secondary to associated loss of anal sphincter function [ 1 , 5 ]. The characteristic symptom of urinary VF is continual leakage of urine from the vagina and vulvar irritation. In recently operated patients, specific symptoms of VF are often masked by common post-operative problems such as abdominal and flank pain, hematuria, worsening renal function, fever and paralytic ileus. Not unusually, iatrogenic damage to the urinary tract is heralded by imaging detection of fluid collections representing urinoma. Biochemical assay of discharge fluid for creatinine levels and intravesical injection of methylene blue dye are helpful to confirm the presence of the VF [ 3 , 4 ].

In the developing world, obstructed labour and perineal lacerations during spontaneous or instrumental delivery remain the most prevalent causes; conversely, in Western countries, VF are increasingly iatrogenic in nature as they develop as complications of various pelvic, urologic and gynaecologic procedures. Although uncommon, VF result in substantial morbidity for patients. The ideal cross-sectional techniques depend on the anatomic site and affected organ. With appropriate acquisition and focused interpretation, state-of-the art CT and MRI provide optimal visualisation of entero- and urinary VF that is crucial for correct therapeutic choice and surgical planning.

Fistulas of the female genital tract were described in medical literature since ancient times: among them, vaginal fistulas (VF) are the most prevalent and are defined as abnormal epithelium-lined communications between the vagina and other pelvic organs [ 1 ]. The spectrum of causes encompasses congenital and developmental abnormalities, inflammatory diseases, infections, tumours, sexual and obstetric trauma, irradiation and post-surgical injuries [ 2 ]. Regardless of the underlying disorder, all VF result in substantial morbidity and severely impair the patients’ quality of life [ 3 – 5 ]. The majority of patients with VF are initially referred to a gynaecologist; however, despite more or less evident clinical signs, vaginal exploration may identify the fistulous orifice in less than 80% of cases [ 5 ]. Similarly, visualisation of the abnormal communication is generally quite challenging at either ano-proctoscopy or urethro-cystoscopy. As a result, clinicians and surgeons need critical help from radiologists to (1) confirm the presence of a VF, (2) visualise its site, course and involved organs, and (3) characterise the underlying pathology [ 6 , 7 ]. Traditionally, imaging demonstration of VF relied on fluoroscopic studies such as contrast medium (CM) enema, intravenous excretory urography, voiding and retrograde cystography, which may opacify a patent fistulous tract but provide very limited information on the affected organs [ 8 , 9 ]. Although developed as the best radiographic technique to confirm and visualise a VF by pressure, conventional vaginography is relatively invasive, cumbersome and poorly tolerated as it requires obstruction of the vaginal introitus by an inflated Foley catheter before injection of CM [ 9 ]. In recent years, CT and MRI studies are largely replacing conventional radiologic techniques. With appropriate acquisition and focused interpretation, state-of-the art cross-sectional imaging may provide optimal visualisation of VF, involved organs and underlying diseases, which is crucial for correct choice between conservative and surgical treatment and appropriate surgical planning. Aiming to improve radiologists’ familiarity with these uncommon but challenging entities, this pictorial essay provides a concise review of VF types, clinical features, causes and mechanisms, then presents with examples the state-of-the art CT and MRI techniques and appearances of VF.

On targeted MRI, urethro-VF may be identified as more or less subtle fistulous tracks similar to ano-VF that course between the anterior aspect of the vagina and the target-like female urethra (Fig.  14 ) [ 43 , 44 ]. Fig. 14 Urethro-VF in an elderly woman seen at MRI as subtle midline track (thin arrows) between the distal third of the vagina (arrow) and urethra containing Foley catheter (thick arrows), with high signal intensity on T2- ( a ), FS T2-weighted ( b ) and high b value DW ( c ) sequences, positive enhancement on post-gadolinium FS T1-weighted acquisition ( d ) Urethro-VF in an elderly woman seen at MRI as subtle midline track (thin arrows) between the distal third of the vagina (arrow) and urethra containing Foley catheter (thick arrows), with high signal intensity on T2- ( a ), FS T2-weighted ( b ) and high b value DW ( c ) sequences, positive enhancement on post-gadolinium FS T1-weighted acquisition ( d ) On either CT-cystography or excretory-phase CT-urography, a urinary VF is heralded by the presence of opacified urine in the vagina (Figs.  15 and 16 ). Uretero- and vesico-VF are identified as urine-filled tracks that connect the vagina to the distal ureter (Fig.  15 ) or bladder (Fig.  16 ), respectively [ 25 , 45 , 46 ]. Alternatively from post-surgical ones, VF may result from locally advanced tumours of the urinary bladder and/or female urethra, which are recognised as abnormal solid, enhancing mural thickening that infiltrates the vagina (Figs. 4 and 16 ) [ 36 ]. Fig. 15 Two cases of iatrogenic urinary VF. a – c After recent surgery for recurrent endometrial carcinoma, CT-urography (note ureteral stent indicated by thick arrows) shows left lateral retraction and opacification of the vagina (arrows) through a short vesico-VF (thin arrow in c ) [Adapted from Open Access Ref. no. [ 25 ]]. d – f Following radical hysteroannessectomy for endometrial carcinoma, CT-urography shows marked fluid-filled dilatation of the vagina (arrow in d ). On ultra-delayed (30 min) acquisition ( e , f ), some opacified urine flows into the vagina (arrows) through a leaking uretero-VF (thin arrows) Fig. 16 Two cases of urinary VF complicating bladder cancers. a – c In a patient with previous hysterectomy, CT ( a , b ) shows extensive mural thickening (*) of the posterior bladder aspect, causing adhesion and focal retraction of the bladder dome, and corresponding filling defect on excretory phase acquisition ( c ). The patent VF (thin arrows) leads to opacification of the vagina (arrows). d – f In a patient with strongly enhancing tumour (*) of the right posterolateral aspect of urinary bladder ( d ), excretory phase acquisition ( e , f ) shows vaginal opacification (arrows) via a short VF (thin arrow in f ) Two cases of iatrogenic urinary VF. a – c After recent surgery for recurrent endometrial carcinoma, CT-urography (note ureteral stent indicated by thick arrows) shows left lateral retraction and opacification of the vagina (arrows) through a short vesico-VF (thin arrow in c ) [Adapted from Open Access Ref. no. [ 25 ]]. d – f Following radical hysteroannessectomy for endometrial carcinoma, CT-urography shows marked fluid-filled dilatation of the vagina (arrow in d ). On ultra-delayed (30 min) acquisition ( e , f ), some opacified urine flows into the vagina (arrows) through a leaking uretero-VF (thin arrows) Two cases of urinary VF complicating bladder cancers. a – c In a patient with previous hysterectomy, CT ( a , b ) shows extensive mural thickening (*) of the posterior bladder aspect, causing adhesion and focal retraction of the bladder dome, and corresponding filling defect on excretory phase acquisition ( c ). The patent VF (thin arrows) leads to opacification of the vagina (arrows). d – f In a patient with strongly enhancing tumour (*) of the right posterolateral aspect of urinary bladder ( d ), excretory phase acquisition ( e , f ) shows vaginal opacification (arrows) via a short VF (thin arrow in f ) Small non-malignant urethro- and vesico-VF may be managed conservatively with prolonged catheterisation or undergo electrocoagulation. Transvaginal surgical repair with or without flap techniques may be either performed early or postponed after healing of inflammation and necrosis, aiming to reduce morbidity. Similarly to iatrogenic and traumatic bladder rupture, a transabdominal approach is required in complex injuries, intraperitoneal leaks and cranial vesico-VF [ 12 , 47 , 48 ]. Sinus tracts differ from VF in that they do not connect to an organ but are blind-ending or terminate into an abscess collection [ 20 , 21 ]. Rare conditions that may mimic a VF both clinically and at imaging are peritoneal and lymphatic fistulas (Fig.  17 ), in which communication is established between the vaginal dome and a post-operative fluid or lymph collection. Differentiation relies on correct identification of the abnormal collection that does not fill with enhanced urine [ 49 ]. Fig. 17 Differential diagnosis: rare case of lymphatic VF in a 67-year-old with previous laparotomic surgery for advanced ovarian cancer. CT ( a , b ) shows fluid-filled dilatation of the vagina (arrows) communicating via a fistula (thin arrow in b ) with an ovoid fluid-attenuation pelvic collection (* in b ) consistent with postoperative lymphocele Differential diagnosis: rare case of lymphatic VF in a 67-year-old with previous laparotomic surgery for advanced ovarian cancer. CT ( a , b ) shows fluid-filled dilatation of the vagina (arrows) communicating via a fistula (thin arrow in b ) with an ovoid fluid-attenuation pelvic collection (* in b ) consistent with postoperative lymphocele