Colonoscopy for screening after kidney transplantation?

Kidney transplant recipients have high rates of advanced colorectal neoplasia and cancers, which are better detected by colonoscopy than by fecal hemoglobin screening, suggests a study in the British Medical Journal.

The cross-sectional study included 229 Australian kidney transplant recipients, mean 9.0 years since transplantation. All were at least 50 years old and, aside from kidney transplantation, at average risk of colorectal cancer. The patients underwent fecal immunochemical testing for hemoglobin followed by colonoscopy with histologic examination of biopsy specimens. The two tests were compared for detection of advanced colorectal neoplasia: adenoma at least 10 mm in diameter, villous features, high-grade dysplasia, or colorectal cancer.

Advanced colorectal neoplasias were detected by colonoscopy in 13 percent of patients and by fecal hemoglobin in 12 percent. Colonoscopy detected colorectal cancer in five patients, three of whom had abnormal results on fecal hemoglobin testing.

The fecal test had 31 percent sensitivity and 90.5 percent specificity for the detection of advanced colorectal neoplasia; positive and negative predictive values were 32.1 percent and 90.1 percent, respectively. One additional case of advanced neoplasia would be detected for each eight colonoscopies performed.

Colorectal cancer is a significant risk for long-term survivors of kidney transplantation. There are few data on colorectal screening for this group of patients; the current guidelines call for fecal hemoglobin screening in patients aged 50 or older.

The new study shows substantial rates of advanced colorectal neoplasia, including cancers, in patients with kidney transplants. Although fecal hemoglobin testing is “reasonably” specific, the sensitivity and positive predictive value are low. “[S]urveillance with colonoscopy may be the most appropriate approach to reduce the risk of colorectal cancer in kidney transplant recipients,” the researchers write [Collins MG, et al. Screening for colorectal cancer and advanced colorectal neoplasia in kidney transplant recipients: cross-sectional prevalence and diagnostic accuracy study of faecal immunochemical testing for haemoglobin and colonoscopy. BMJ 2012; 345:e4657].