Uncommon Fistulas of the Abdomen and Pelvis: Clinico-Radiological Correlation and the Role of Plain and Contrast Enhanced Computed Tomography

AbstractIntroduction and background:A fistula is an abnormal communication between two epithelial surfaces, and they are named based on the organs they connect. The name begins with the primary organ involved, followed by the organ to which the fistula is connected. For example, an enterocutaneous fistula arises from the small intestine and ends or opens into the skin[1]. The etiology of abdominal and pelvic fistulas can be due to iatrogenic causes, trauma, inflammatory bowel disease, obstetrical complications, neoplasm and radiation therapy The symptoms caused by the fistula have an enormous impact on both the physical and mental well-being of the patient[2].The prevalence of underlying disease, efficiency of surgical practice, quality of healthcare, incidence of trauma, and use of radiation are the most common factors that influence the incidence of fistulae1. The diagnosis of uncommon abdominal and pelvic fistulas depends on a combination of adequate clinical history and radiological evaluation. Depending on the underlying disease, various signs and symptoms can be identified. Specific symptoms related to the organ involved may be narrowed. Examples include symptoms of recurrent urinary tract infections, pneumaturia, or fecaluria in an enterovesical fistula[3]. Post-surgical Enterocutaneous fistulas can occur early with associated fever, elevated pulse rate, hypotension, breathing difficulties, abdominal pain, distension, acidosis and elevated white blood cells and C-reactive protein. Alternatively, it can present with discharge at the site of incision in the later period with associated inflammation of the skin. The high morbidity and mortality associated with intestinal fistulas is due to infection, malnutrition, and metabolic imbalance[4]. While common fistulas, such as those associated with Crohn's disease or post-surgical complications, are well-documented, uncommon fistulas—defined by their low incidence and atypical locations—remain understudied and frequently overlooked in clinical practice[5,6]. Their rarity and anatomic complexity often delay diagnosis, and proximity to vital structures heightens risks, exacerbating morbidity and mortality[7]. Few studies claim that ultrasonography (US) is useful in the diagnosis of fistula as it is non invasive[8], But Computed tomography (CT) is far more accurate in delineating a fistulous tract, and helps in identifying the etiology and the extent of involvement. This influences patient management and is highly valuable in planning corrective surgeries[2]. Multidetector CT is important in severely ill uncooperative patients and obtains high-spatial-resolution images and limits artifacts due to motion. CT fistulography with the injection of iodinated contrast media, such as 3% diluted iopamidol or iohexol, through the external fistulous opening is a useful technique that combines information of the involved organs and also other anatomic details[9,10]. Contrast-enhanced CT is the modality of choice for evaluating pelvic fistulas associated with malignancies, and MRI is complimentary to it[11]. Magnetic resonance imaging (MRI) is useful in the diagnosis of fistulas, but is limited by artifacts secondary to physiological motion, such as bowel peristalsis, cardiac pulsations and respiration[12]. Rapid, heavily T2-weighted MR imaging is useful for diagnosing occult vesicouterine fistula[13]. The approach to treatment depends on many factors, such as the severity of the condition, type of fistula, patient's general status, underlying etiology, and complications resulting from the fistula[14].. The management of fistulas, especially intestinal fistulas, is a complex and highly challenging task. It requires multimodal efforts, interpersonal communication, adequate assessment, and meticulous planning. Patients with suspected fistulas should be appropriately referred and investigated. All relevant information, including previous surgical details, should be obtained. Proper planning and multi-disciplinary approach are essential for successful management[15]. This study highlights the crucial role of computed tomography in facilitating the correct diagnosis, narrowing differentials, choosing appropriate contrast routes, delineating fistulous tracts, identifying complications, and planning management. Ultimately, integrating a detailed clinical history with advanced imaging is essential for optimizing outcomes in these challenging conditions. Aim: To identify the epidemiology, clinico-radiological correlation and imaging features of uncommon fistulas of the abdomen and pelvis using computed tomography. Objectives: To analyze the age and sex distribution of patients with uncommon fistulas in the abdomen and pelvis. To identify the etiology and establish the degree of clinic-radiological correlation. To interpret the imaging features using plain and contrast enhanced tomography. Purpose:To identify the epidemiology, clinico-radiological correlation and imaging features of uncommon fistulas of the abdomen and pelvis using computed tomography.Materials and Methods:Study design: This was a retrospective study.Study site: A tertiary care hospital in India.Study period: 10 years.Plain and contrast-enhanced computed tomography data were gathered from the institutional database for the past 10 years, and fistulas of the abdomen and pelvis with a very low incidence were identified. Clinical history was gathered on correlation with the definitive histopathological diagnosis of the etiology. Results: In a study of 35379 plain and 24861 contrast enhanced CTs of the abdomen and pelvis, 11 rare fistulas were identified, predominantly in women aged 40–60 years. These fistulas included types such as Aorto-gastric, Esophageal -pulmonary, Cholecysto-biliary, Cholecysto-duodenal, Nodal-duodenal, Colo-enteric, Colo-renal, Appendico- vaginal, Nephro- cutaneous, Uretero-cutaneous and Urethro-vaginal fistulas. The etiologies were as follows: 36.3 % neoplastic. 27.2 % iatrogenic. 18.1 % infectious. 18.1 % idiopathic, with radiological and clinical findings correlating in 82 % of cases.