Patients referred for colon inspection (colonoscopy) due to suspicion of colon polyps/cancer will receive local administration of hexaminolevulinate (HAL) prior to colon inspection. Blue light illumination will induce red fluorescence of polyps and tumours, improving detection of the polyps and tumors. Different HAL doses will be tested to find the optimal image conditions. Tolerability measurements will be performed to ensure patient safety.

Colonoscopy is regarded as the "gold standard" for diagnosis of colorectal cancer. The sensitivity is uncertain but proposed to be (75-95%), however flat adenomas which are easily missed, are often not recognised. Fluorescence imaging may increase the sensitivity of standard white light colonoscopy by identifying more polyps and flat adenomas which will make the resection of adenomas more complete.

In this study hexaminolevulinate (HAL) will be administered locally as a photosensitiser, using different doses to find the optimal imaging conditions as well as making patient safety assessments.

Both standard white light and blue light (fluorescence) inspection will be performed.

Inclusion Criteria:

• Patients with suspicion of colorectal cancer
• Written informed consent
• Data protection consent
• 18-85 years

Exclusion Criteria:

• Liver cirrhosis
• Hepatitis
• Abnormal liver function
• Porphyria
• Patient non-compliance
• Coagulation disorder
• Contraindication to colonoscopy
• Pregnancy and lactation
• Participation in another study