Most clinical characteristics of IC/BPS are classified by cystoscopic findings. The urodynamic study of IC/BPS has been investigated, but no definite benefit could be obtained, except an increased bladder sensation and positive potassium chloride (KCl) test noted in some patients with IC. A previous study of HIC showed evident diffuse thickness of the bladder wall and contracted bladder, which might lead urologists to choose partial cystectomy for early symptom relief. However, little research has been conducted to investigate the morphology of the bladder wall in NHIC and the relationship between bladder wall thickness (BWT) and clinical characteristics of IC/BPS. This study investigated bladder morphology on computed tomography (CT) scans in a cohort of patients with IC and its relationship with bladder histopathology and urinary biomarkers.

A total of 182 patients with cystoscopy-proven IC/BPS underwent abdominal computed tomography (CT) before intervention. The BWT on CT was classified as smooth, focal thickness, and diffuse thickness. Clinical symptoms, urodynamic findings, cystoscopic characteristics, presence of Hunner’s lesion, urinary biomarkers, and bladder histopathology were compared among the three subgroups. We retrospectively analyzed patients with clinically proven IC/BPS. IC symptom scores, including the IC symptom index, IC problem index, and visual analog scale (VAS) of pain, were recorded at baseline. All patients were thoroughly investigated to confirm the diagnosis of HIC and NHIC based on the presence of Hunner’s lesion or glomerulations after cystoscopic hydrodistention without or with anesthesia. Before diagnostic cystoscopy, all patients had also undergone video urodynamic study (VUDS) with a positive KCl test after bladder emptying. The patients also underwent pelvic CT to investigate their lower urinary tract condition and BWT. To assay urinary inflammatory proteins and oxidative stress biomarkers, urine samples were collected at fullness bladder sensation. In this study, we investigated the urinary inflammatory and oxidative stress biomarkers including CXCL10, MCP-1, NGF, BDNF, exotoxin, IL–2; IL-6; IL-8, MCP–1 beta; RENTES, TNF-α, PGE2, 8-OHdG, 8-isoprostane; and TAC. Cystoscopic hydrodistention was performed under general anesthesia and an intravesical pressure of 80 cmH2O for 10 minutes, and the bladder was carefully examined for the formation of petechial, glomerulation, splotch hemorrhage, mucosal fissures, or ulceration. To evaluate BWT and other possible pathologies, pelvis bladder CT was performed before cystoscopic hydrodistention during a recent admission.

Among the studied patients, 85 had smooth, 64 had focal, and 33 had diffuse BWT (Figure 1). The duration of IC history was 9.45 ± 8.56, 9.98 ± 9.98, and 8.03 ± 6.69 years, respectively (p = 0.599). Table 1 shows the clinical demographics, symptoms, and urodynamic parameters of cystoscopic findings in patients with different BWT subgroups. Patients with diffuse BWT were significantly older, had smaller MBC and cystometric bladder capacity (CBC), higher grade of glomerulation, and higher IC symptom scores. We found HIC in 84.8% of patients with diffuse BWT, 21.9% in patients with focal BWT, and none in patients with smooth BWT. Patients with focal BWT had a higher rate of small MBC than patients with smooth BWT did. In investigating the urine biomarker levels among controls and different IC/BPS patients with different BWT, we found the urinary biomarkers were significantly higher in IC/BPS patients than that of controls in IL-8, CXCL10, eotoxin, IL-6, TNF-α, PGE2, 8-OHdG, and 8-isoprostane. The levels of urinary biomarkers were higher in patients with focal or diffuse BWT than with smooth BWT, in IL-8, CXCL-10, exotoxin, and IL-6. The urinary levels of oxidative stress biomarkers were significantly higher in IC/BPS patients than the controls, but was not significantly different among IC/BPS patients with different BWT. We also investigated the histopathological findings of 49 patients of IC/BPS with smooth BWT, 34 with focal BWT, and 26 with diffuse BWT for urothelium denudation, eosinophil and plasma cell infiltration, lamina propria hemorrhage, and granulation and compared these among patients of different BWT subgroups. We found significantly higher rates of mild-to-severe urothelial denudation and presence of plasma cell infiltration in the bladder wall among patients with focal BWT and the highest rates in patients with diffuse BWT as compared with patients with smooth BWT. Patients with diffuse BWT had significantly higher rates of mild-to-severe inflammatory cell infiltration, eosinophil infiltration, nerve bundle hyperplasia, and granulation tissue than those in the smooth and focal BWT subgroups. The other histopathological findings were not different among patients with different BWT subtypes.

In patients with IC/BPS, focal and diffuse BWT on bladder CT correlated well with the presence of HIC, small MBC, and high grade glomerulation. The presence of diffuse BWT is associated with increased bladder inflammatory cell infiltration, urothelial cell denudation, eosinophils and plasma cells infiltration, nerve bundle hyperplasia, and granulation tissue in patients with IC/BPS, which might predict the presence of HIC.

The results of this study demonstrated that focal or diffuse BWT detected in the bladder CT scans of patients with IC/BPS can be a good diagnostic test for patients with HIC and reflect the severity of bladder inflammatory conditions associated with a small bladder capacity and more IC symptoms. BWT in CT scans can reflect chronic inflammation of the bladder wall in patients with IC/BPS, which is clinically relevant for the diagnosis and treatment of IC subtypes.