Feasibility of Mannitol as a Neutral Oral Contrast Agent in Per Oral MDCT Colonography: A cross-sectional study

Background: Large bowel diseases, including colorectal carcinomas, adenomas, polyps, and inflammatory bowel diseases, are prevalent causes of morbidity and mortality worldwide, with tubercular diseases being common in India. Conventional radiology and colonoscopy have historically been instrumental in diagnosis; however, colonoscopy’s invasiveness and patient discomfort limit its widespread use. Computed tomographic colonography (CTC) offers a minimally invasive alternative, but its efficacy depends on adequate bowel distension and preparation, which can be uncomfortable for patients.

Objective: This study evaluates the feasibility of using mannitol as a neutral oral contrast agent in per oral MDCT colonography, aiming to achieve sufficient colonic distension and mucosal visualization with minimal patient discomfort and reduced preparation requirements.

Materials and Methods: An observational, cross-sectional study was conducted on 100 patients aged 18-70 years undergoing MDCT of the abdomen and pelvis. Patients received a low-residue diet and laxatives prior to the procedure, followed by ingestion of 1500-2000 ml of 3% mannitol over approximately 20–80 minutes. Imaging was performed 120-145 minutes post-ingestion, using a 64-slice CT scanner. Parameters assessed included colonic distension (qualitative and quantitative), mucosal and mural visualization, fecal residue presence, and patient discomfort.

Results: The majority of colonic segments demonstrated optimal distension, with ascending and descending colon achieving the highest maximum diameters (mean ~5.15 cm and 3.43 cm respectively). Complete collapse was rare (<5%), while partial and suboptimal distension occurred in 7-34% of segments. Mucosal and mural visualization was adequate in most segments, though fecal residue was more prevalent in the rectum and sigmoid colon. Patient discomfort was mild, with mild abdominal pain reported in 20%, and nausea, vomiting, and loose stools in fewer cases. The average time for contrast ingestion was approximately 45.85 minutes, with imaging performed around 117 minutes after starting contrast intake.

Conclusion: Mannitol appears to be a feasible neutral oral contrast agent for per oral MDCT colonography, providing adequate colonic distension and visualization with minimal patient discomfort. This approach has the potential to reduce preparation-related burden and improve patient compliance, representing a promising paradigm shift in large bowel imaging