Normalized distance along the colon centerline: a method for correlating polyp location on CT colonography and optical colonoscopy.

OBJECTIVE: The ability to accurately locate a polyp found on CT colonography (CTC) at subsequent optical colonoscopy (OC) is an important part of the successful implementation of CTC for colorectal cancer screening. The purpose of this study was to determine whether a polyp's normalized distance along the colon centerline derived from CTC data can accurately predict its location on OC. MATERIALS AND METHODS: The polyp population consisted of 152 polyps in 121 patients. CTC polyp findings were verified by same-day segmentally-unblinded OC. Each polyp's normalized distance along the colon centerline was computed by dividing its distance from the anorectal junction measured along the colon centerline by the length of the colon at CTC. The predicted polyp location at OC was computed by multiplying the normalized distance along the colon centerline by the colon length at OC (i.e., the distance to the cecum as determined at full colonoscope insertion). The differences between the true and predicted polyp locations at OC were compared using paired Student's t tests, linear regression, prediction interval assessment, and Bland-Altman analyses. RESULTS: The differences between the true and predicted polyp locations at OC using the supine and prone CTC-normalized distances along the colon centerline were 2.2 +/- 10.5 cm (mean +/- SD; n = 136) and 1.5 +/- 10.5 cm (n = 135), respectively. The predicted location was within 10 cm of its true location for 71.3% (97/136) to 74.8% (101/135) of polyps and within 20 cm of its true location for 93.3% (126/135) to 93.4% (127/136) of polyps. CONCLUSION: By computing the normalized distance along the colon centerline of a polyp found at CTC, the location of a polyp at OC can be predicted to within 10 cm (i.e., 1 colonoscope mark) for the majority of polyps.

Crystalloid deposits in the kidney.

Light chain-producing lymphoproliferative disorders such as multiple myeloma are frequently complicated by renal impairment. Typically, the renal biopsy of a patient with renal failure caused by multiple myeloma shows cast nephropathy, but occasionally crystals may be seen. We describe the case of a patient with acute renal failure caused by multiple myeloma in which, on renal and bone marrow biopsy, there were widespread crystalloid deposits. Crystalloid nephropathy is a very rare condition associated with multiple myeloma and other light chain-secreting disorders. An underlying lymphoproliferative disorder should be considered in the differential diagnosis if crystalloid deposits are seen on a renal or other tissue biopsy.

Tomacula in MAG-deficient mice.

The pathogenesis of tomacula in mice with a null mutation of the myelin-associated glycoprotein (MAG) gene is not well understood. This study, using a novel teased nerve fiber technique, demonstrates that tomacula in MAG-deficient mice are formed by redundant myelin infoldings and outfoldings in the paranodal regions as early as 4 weeks after birth and increase in size and frequency with age. Although tomacula show degenerative changes with increasing age, there was no significant evidence of demyelination/remyelination. Longitudinal sections of normal teased nerve fibers show early redundant myelin foldings in externally normal paranodal regions. These data and the absence of internodal tomacula support a role for MAG in the maintenance of myelin at the paranodal regions.